Processes for the oxidation of methane and ethane using iodine-based catalysts

Abstract

The invention relates to the production of methanol via the partial oxidation of methane using iodine(III) catalysts, which allow the reaction to be performed at low temperatures and pressures. Similar chemistry can be used to make methyl bisulfate from methane in the presence of oleum, and to make ethylene glycol via the partial oxidation of ethane.

Description

[0001] PROCESSES FOR THE OXIDATION OF METHANE AND ETHANE USING IODINE-BASED CATALYSTS FIELD The present invention relates to the production of methanol via the partial oxidation of methane using iodine- based catalysts, which allow the reaction to be performed at low temperatures and pressures. Similar chemistry can be used to make (i) methyl esters such as methyl triflate from methane, (ii) methyl bisulfate from methane in the presence of oleum, and (iii) ethylene glycol via the partial oxidation of ethane. BACKGROUND Methane (CH4) is the most abundant hydrocarbon on the planet. CH4can be used as a fuel, although it is difficult to store and transport (b.p. = –161°C). Due to these challenges CH4is often flared at source, with $16.4 billion worth flared annually. Methanol (CH3OH), in contrast, is a readily transportable liquid fuel (b.p. 65°C) and a platform industrial chemical that is converted into myriad value-added products, including formaldehyde, acetic acid, olefins and plastics. Methanol is one of the top chemicals produced annually (111 million metric tonnes in 2022; Statista) and the CH3OH market is valued at $37.4 billion (Statista, 2021). Currently, CH3OH can be produced indirectly from CH4 by steam reforming to form syngas (CO / H2) and subsequently converted to methanol over a zeolite catalyst. This energy intensive process requires harsh conditions, requiring significant highly specialised infrastructure. It is therefore usually not commercially viable to store and transport the methane from source to plant. Steam reforming of CH4 to syngas (1); followed by CH3OH synthesis (2). This process is a significant emitter of carbon dioxide, especially since it is carried out on a vast scale to produce millions of tonnes of methanol each year (see https: / / energycentral.com / c / og / carbon-footprint-methanol). A simpler method would involve the partial oxidation of methane with oxygen, i.e. CH4 + 0.5 O2 = CH3OH, but practically this is impossible to achieve due to over-oxidation to carbon dioxide (i.e. complete combustion). A direct CH4to CH3OH process would avoid such a high cost by being locally scalable. The direct and selective catalytic oxidation of CH4 to CH3OH with O2 (the only commercially feasible oxidant) is clearly an extremely attractive and lucrative goal. To date, however, no industrially viable process exists for this transformation. It has been shown that inexpensive, highly electrophilic main-group (p-block) compounds TlX3and PbX4(X = trifluoroacetate, CF3CO2–) can cleanly oxidise CH4 (forming CH3X and HX) while being reduced to TlX and PbX2 respectively. Under these conditions, however, O2 (E0: O2 / H2O = +1.23 V vs SHE) is unable to regenerate Tl3+ / Pb4+from Tl+ / Pb2+(E0Mn+ / M(n-2)+> +1.23 V) and thus reactivity is stoichiometric (see Science, 2014, 343, 1232-1237). Main-group mediated catalytic oxidation of CH4to CH3OH. Previous work is stoichiometric in M (M = Tl or Pb). Hypervalent iodine species have been used to oxidise hydrocarbons including methane and ethane to alcohol esters. For example, Gunnoe and coworkers (J. Am. Chem. Soc.2014, 136, 8393-8401) have shown that iodate (IO3-) salts can be used to convert methane to methyl trifluoroacetate (MeOC(O)CF3; MeTFA) in the presence of trifluoroacetic acid (HTFA) and chloride ions. Similarly, iodine (III) species such as ICl3and I(TFA)3can be used to convert methane to MeTFA in HTFA in the presence of chloride ions. However, these reactions only result in any appreciable yield of methyl esters at high temperatures of at least around 180 °C and high pressures of the order to 240-6900 kPa. Also, these reactions are stoichiometric, not catalytic, with respect to the iodine species and do not directly produce methanol; a separate hydrolysis step would be required to convert methyl esters such as MeTFA to methanol. Such chemistry therefore has significant drawbacks for the green and efficient production of methanol. Ethylene glycol is another industrially important chemical used as a polymer precursor, coolant, heat transfer agent and in antifreeze. It is also produced on a scale of tens of millions of tonnes per year. It is generally produced from ethylene (which is itself produced from thermal cracking of ethane) via ethylene oxide. Ethylene oxide is reacted with water to produce ethylene glycol, catalysed by acids or bases (see, for example, Energy, 2008, 33, 817-833). However, the process produces undesirable side products including diethylene glycol, triethylene glycol and tetraethylene glycol. The separation of these oligomeric compounds and water from the ethylene glycol is energy intensive and generally leads to CO2 emissions. Typical process for the production of ethylene glycol from ethane, involving thermal cracking of ethane to form ethene, followed by oxidation to ethylene oxide and hydrolysis to ethylene glycol Other processes for the production of ethylene glycol include the OMEGA process which involves conversion of ethylene oxide to ethylene carbonate using CO2and subsequent hydrolysis in the presence of a base catalyst. Ethylene glycol may also be produced from carbon monoxide, which is readily available in countries with large coal reserves. Recently, alternative routes for the production of ethylene glycol have been investigated, including direct oxidation of ethane. However, significant challenges are selectivity for ethylene glycol and the ability to avoid needing to use high temperatures and pressures. Periana et al have investigated the use of thallium-based compounds for the oxidation of ethane to diester compounds that can be hydrolysed to ethylene glycol, but the reaction is not selective for diester compounds since some monoester is formed, and the use of highly toxic thallium compounds is industrially unattractive (see Organometallics, 2020, 39, 1907-1916). Methyl bisulfate (CH3OSO3H) is another important chemical, which is a key precursor to dimethyl sulfate, a common methylating agent in organic synthesis. It can be produced via the platinum-catalysed reaction of methane with SO3 and O2, but routes which avoid the need to use expensive transition metal catalysts are desirable. It has been shown that iodine dissolved in oleum (i.e. sulfuric acid containing free SO3) can be used to convert methane to methyl bisulfate (see Chem. Commun., 2002, 2376-2377). However, the reaction requires elevated temperatures of around 165-220 °C and high methane pressures of around 500 psi (ca.3500 kPa). Iodine (III) compounds such as I(HSO4)3were found not to be able to convert methane to methyl bisulfate in oleum. There is a need in the art for processes that address the drawbacks discussed above and which enable the production of methanol, methyl bisulfate and ethylene glycol in a greener and more energy efficient manner. SUMMARY OF THE INVENTION The present invention provides a number of different processes which all share the common inventive concept of the partial oxidation of an alkane (methane or ethane) by an iodine(III) compound in which the iodine bears particular functional groups. The reactions generally take place in the presence of acid and may involve the addition of NO2 as an oxidant to enable the process to function catalytically. The present invention provides a process for producing methanol comprising: (a) adding methane to a solution of an iodine(III) compound in acid in a reaction vessel, wherein the iodine in the iodine(III) compound is bonded to at least one -OSO2R, -OC(O)R or -N(SO2R)2 group, wherein R is a C1-8 alkyl group optionally substituted with one or more halogen atoms, or wherein the iodine(III) compound is I(SO4)(HSO4), wherein the acid is an acid that has a pKa of less than 3 on the aqueous pKa scale or the acid is an acid that has a Hammett acidity function (H0) of less than -2; (b) allowing the methane to react with the iodine(III) compound in the reaction mixture formed in step (a); and (c) adding NO2 to the reaction vessel. O2may be used to regenerate NO2, such that O2acts as the terminal oxidant in the process. The present invention also provides a process for producing methanol comprising: (a) adding NO2 to a solution of I2 in acid in a reaction vessel, wherein the acid is H2SO4 / SO3 or wherein the acid is an acid having the formula RSO3H, RCO2H or HN(SO2R)2, wherein R is a C1-8alkyl group optionally substituted with one or more halogen atoms, wherein said acid is an acid that has a pKa of less than 3 on the aqueous scale or the acid is an acid that has a Hammett acidity function (H0) of less than -2; (b) adding methane to the reaction vessel; (c) allowing the methane to react with the reaction mixture formed in step (a). The present invention also provides a process for the preparation of a compound of the formula CH3X or XCH2CH2X comprising reacting methane or ethane with an iodine(III) compound, wherein X is -OSO2R or -N(SO2R)2and wherein the iodine in the iodine(III) compound is bonded to at least one X group, wherein R is a C1-8 alkyl group optionally substituted with one or more halogen atoms. This process may be used to produce ethylene glycol by addition of NO2to the reaction vessel, which results in the formation of water in situ that can hydrolyse the XCH2CH2X to ethylene glycol, which can then be separated from the reaction mixture. The present invention provides a process for the preparation of ethylene glycol comprising adding ethane to a solution of the iodine(III) compound in acid in a reaction vessel, wherein the acid is an acid that has a pKa of less than 3 on the aqueous scale or wherein the acid is an acid that has a Hammett acidity function (H0) of less than -2, wherein X is -OSO2R or -N(SO2R)2 and wherein the iodine in the iodine(III) compound is bonded to at least one X group, wherein R is a C1-8alkyl group optionally substituted with one or more halogen atoms, and wherein the process further comprises adding NO2. The present invention also provides a process for the preparation of methyl bisulfate comprising: (a) adding methane to a solution of an iodine(III) compound in H2SO4 / SO3in a reaction vessel, wherein the iodine in the iodine(III) compound is bonded to at least one -OSO2R, -OC(O)R or -N(SO2R)2 group, wherein R is a C1-8 alkyl group optionally substituted with one or more halogen atoms; (b) allowing the methane to react with the iodine(III) compound in the reaction mixture formed in step (a). The present invention also provides a process for the preparation of methyl bisulfate comprising: (a) adding I2to H2SO4 / SO3in a reaction vessel; (b) adding NO2to the reaction vessel; (c) adding methane to the reaction vessel. Preferred features of the processes of the invention are defined in the appended claims. BRIEF DESCRIPTION OF THE FIGURES Figure 1 depicts the % conversion of CH4as a function of temperature in a solution of I(OTf)3in HOTf in an NMR tube with no stirring, wherein the CH4was added at 1 bar. Figure 2 is the1H NMR spectrum of pure MeOTf in HOTf. Figure 3 is the1H NMR spectrum of a low concentration of MeOH in HOTf. Figure 4 is the1H NMR spectrum of a high concentration of MeOH in HOTf. Figure 5 is the1H NMR spectrum of the reaction mixture obtained from the catalytic oxidation of methane using I2 in HOTf, as described in Example 6. Figure 6 is a depiction of the crystal structure of I(SO4)(HSO4), as determined by X-ray diffraction. Figure 7 depicts1H NMR spectra obtained during an experiment to examine CH4 activation by I(SO4)(HSO4) formed in situ from I(TFA)3 in oleum. The top spectrum is the spectrum obtained before CH4 addition and the bottom spectrum is the spectrum obtained after adding CH4at 1 bar and heating the reaction mixture to 100°C for 18 hours. Figure 8 is the gas phase IR spectrum of the headspace of a reaction between I2 in trifluoromethanesulphonic acid, and NO2. Figure 9 is the gas IR spectrum of the NO2 used in the Examples. DETAILED DESCRIPTION The present invention solves the problems described above by providing green, energy efficient processes for the production of methanol and methyl bisulfate from methane and for the production of ethylene glycol from ethane. The processes may also be used to make methyl esters and ethyl diesters, as will be described further below. With respect to methanol production, the present invention provides a single-step process for the reaction CH4+ 0.5 O2= CH3OH that uses an inexpensive catalyst based on iodine, operates under industrially-attractive conditions (low temperatures such as 50-100°C and low pressures, even atmospheric pressure), does not produce CO2, and can be cycled with CH4 and O2 reactants, which avoids the need to combine a combustible mixture of these gases. This is a significant milestone that offers clear economic advantages over existing CH3OH synthesis routes. The provision of a syngas-free route of converting methane to methanol in a single step without having to use high temperatures and pressures and without using an expensive or highly toxic metal catalyst has been one of the holy grails of catalysis. The present invention provides a remarkable step forward in this field. The present invention is based on the surprising discovery that certain iodine (III) compounds in acidic media can be used to convert methane to methyl esters without overoxidation to CO2 at dramatically milder conditions than known processes described above which utilise Pb or Tl catalysts or other hypervalent iodine compounds in the presence of chloride ions. In particular, the processes of the present invention can be used to oxidise methane cleanly and in high yield at 1 bar CH4 and at room temperature, which is a highly unexpected, groundbreaking result in view of the well-known difficulty of activating alkanes such as methane at low temperatures and pressures. Even more attractively, the present invention provides a process which is catalytic with respect to iodine, by using NO2, an abundant waste gas, as the redox mediator. In doing so, the process effectively takes two waste gas streams (CH4and NO2) and uses them to synthesise a methyl ester. Also, the use of NO2results in the formation of H2O in situ, which hydrolyses the methyl ester formed from the reaction of the iodine (III) compound with methane to methanol. The process is thus a true ‘waste to wealth’ transformation. Methanol is formed in situ when NO2 is employed in the process and can be separated from the reaction mixture, for example by distillation. Further still, the NO produced by reduction of the NO2during the process can be re-oxidised by O2to regenerate NO2 in a facile manner, making the waste gas NO2 a catalytic redox mediator and making O2 the terminal oxidant. The overall process is summarised below, for the case where the iodine (III) catalyst is I(OTf)3(OTf = triflate = CF3SO3-), which is dissolved in triflic acid (CF3SO3H (“HOTf”)). Definitions pKa refers to the -log10of the acid dissociation constant (Ka) of an acid (i.e. pKa = -log10Ka). Kais defined as: wherein HA is the acid, which dissociates into H+and A- ions, and the square brackets denote the concentration of each species. pKa as defined herein refers to pKa on the aqueous scale, meaning the pKa value measured in water at 25 °C. The pKa of most acids on the aqueous scale can be found in standard reference texts and so does not need to be measured in the majority of cases. If needed, pKa can be measured by potentiometric titration by titrating a sample of the relevant substance with acid, such as 0.1M HCl, and monitoring the titration with a pH electrode. The pKa value can be determined from the equivalence point of the titration curve, i.e. the point at which the slope of the titration curve is at its greatest (i.e. where the inflection point occurs and the line changes from upward curvature to downward curvature). At this point the pH = pKa. Such methods of determining pKa are standard and well-known in the art. The Hammett acidity function (H0) is a measure of the acidity of a substance. H0is a standard measure of acidity and H0 values for many acids can be found in standard reference texts, such that H0 does not need to be measured in the majority of cases. If needed, it can be calculated using the formula: wherein “log” is the common logarithm (log10), B is a weak base indicator, such as p-nitrochlorobenzene, BH+is the conjugate acid of B and pKBH+ = -log10(K) for the dissociation of BH+where K is the dissociation constant of BH+at 25 °C. represents the ionisation ratio of the indicator and this can be measured directly using UV-visible spectroscopy (i.e. by a spectrophotometric method) at 25 °C. Those skilled in the art will be familiar with measurement of such parameters by UV-visible spectroscopy. Such methods are widely described in the literature, for example in J. Am. Chem. Soc., 1971, 93, 5083–5087. The term “wherein the acid is an acid that has a pKa of less than 3 on the aqueous pKa scale or the acid is an acid that has a Hammett acidity function (H0) of less than -2” (and likewise for other disclosed values of pKa and H0) means that the acid is either (i) an acid that has a pKa of less than 3 on the aqueous pKa scale, as defined above, or (ii) an acid that has a Hammett acidity function (H0) of less than -2. The acid may be an acid that has both a pKa of less than 3 on the aqueous scale and a H0value of less than -2 (and likewise for other disclosed values of pKa and H0), or it may be an acid that satisfies one or other of these requirements but not both. The term “alkyl” refers to a straight- or branched-chain alkyl group containing only single bonds between carbon atoms and in which the carbon atoms are saturated with hydrogen atoms. Examples of alkyl groups include methyl (Me), ethyl (Et), n-propyl, isopropyl, butyl, isobutyl, sec-butyl, tert-butyl (tBu), pentyl, isopentyl, tert-pentyl, hexyl, isohexyl, and groups that in light of the ordinary skill in the art and the teachings provided herein would be considered equivalent to any one of the foregoing examples. The term “substituted” means that the specified group or moiety bears one or more substituents. The term "unsubstituted" means that the specified group bears no substituents. The term “optionally substituted” means that the specified group is unsubstituted or substituted by one or more substituents. Where the term “substituted” is used to describe a structural system, the substitution is meant to occur at any valency-allowed position on the system. In cases where a specified moiety or group is not expressly noted as being optionally substituted or substituted with any specified substituent, it is understood that such a moiety or group is intended to be unsubstituted. The term “perfluorinated” means that the carbon atoms in the relevant moiety are substituted with a fluorine atom at every available valency, in line with its standard meaning in the art. “H2SO4 / SO3” refers to sulfuric acid (H2SO4) that contains dissolved SO3. This substance is commonly known as oleum, or fuming sulfuric acid, and is usually produced by dissolving SO3 in concentrated H2SO4. Typically, in oleum, the H2SO4 contains dissolved SO3 in an amount of 1-65% w / w. A “sulfonic acid” is an acid that contains a -SO3H moiety. A “carboxylic acid” is an acid that contains a -CO2H moiety. A “perfluorinated C1-8alkyl sulfonic acid” comprises a perfluorinated C1-8alkyl group attached to a sulfonic acid (SO3H) moiety. A “perfluorinated C1-8alkyl carboxylic acid” comprises a perfluorinated C1-8alkyl group attached to a carboxylic acid (CO2H) moiety. An “iodine(III) compound” is a compound in which iodine is present in the +3 oxidation state. “OTf” is an abbreviation for “triflate”, which is the common name for a trifluoromethanesulfonate (CF3SO3-) moiety. It is the conjugate base of triflic acid (trifluoromethanesulfonic acid, CF3SO3H, also known as HOTf). “Tf” is an abbreviation for a CF3SO2 moiety. “TFA” is an abbreviation for “trifluoroacetate”, i.e. CF3CO2-. It is the conjugate base of trifluoroacetic acid (TFAH, or CF3CO2H). When a value is defined as being in the range from X to Y, the range includes the endpoints X and Y. Process for producing methanol using iodine(III) compound As explained above, the invention provides a process for producing methanol comprising: (a) adding methane to a solution of an iodine(III) compound in acid in a reaction vessel, wherein the iodine in the iodine(III) compound is bonded to at least one -OSO2R, -OC(O)R or -N(SO2R)2 group, wherein R is a C1-8 alkyl group optionally substituted with one or more halogen atoms, or wherein the iodine(III) compound is I(SO4)(HSO4), wherein the acid is an acid that has a pKa of less than 3 on the aqueous pKa scale or the acid is an acid that has a Hammett acidity function (H0) of less than -2; (b) allowing the methane to react with the iodine(III) compound in the reaction mixture formed in step (a); and (c) adding NO2to the reaction vessel. Throughout the present disclosure, term “a solution of an iodine(III) compound in acid” as used herein means a solution formed by adding an iodine(III) compound to an acid. This applies regardless of the nature of the iodine species that are present in the resultant solution. As explained below, in an alternative way of carrying out the process of producing methanol, the iodine(III) compound may be formed in situ from the oxidation of I2 in acid with NO2. When methane is added to the solution of the iodine(III) compound in acid, the methane is oxidised to a methyl ester in which a CH3 group is attached to a -OSO2R, -OC(O)R or -N(SO2R)2 group from the iodine(III) compound (a compound of formula CH3N(SO2R)2 is not formally a methyl ester but may be referred to as such, including in this disclosure). At the same time, the iodine is reduced from I(III) to I2. The I2can be oxidised back to an iodine(III) compound by NO2, which causes the NO2to be reduced to NO. Due to the presence of acid, when NO2 oxidises the I2 to I(III), H2O is also formed in situ. The H2O can hydrolyse the methyl ester in situ and therefore the use of NO2 not only enables the process to be catalytic by regenerating the I(III) compound, but also allows methanol to be produced without a separate hydrolysis step. In the reaction mixture, there is an equilibrium between the methyl ester and methanol: wherein X is a -OSO2R, -OC(O)R or -N(SO2R)2 group and the position of the equilibrium depends in part on the nature of HX, as explained below. In step (a), the methane may be added at low pressure. The reaction proceeds well at 1 bar pressure and methane may therefore be added at a pressure as low as 0.5 bar. The ability to activate methane at pressures in the region of about 1 bar or below is a remarkable benefit of the present invention compared to known processes, which require the use of much higher pressures. However, in an industrial context it may be desired to use a higher pressure in order to achieve a faster reaction. There is no particular maximum on the pressure that may be used, and this will largely be dictated by the nature of the reaction vessel used. Therefore, in step (a), the methane may be added to the reaction vessel at any pressure of about 0.5 bar or above, preferably in the range from about 0.5 bar to about 200 bar or about 0.5 bar to about 100 bar. More preferably, the methane is added to the reaction vessel at a pressure in the range from about 1 bar to about 100 bar, even more preferably in the range from about 1 bar to about 50 bar. A pressure in the range from about 1 bar to about 50 bar may beparticularly suitable for industrial applications. In step (b) of the process, the methane can be allowed to react with the iodine(III) compound at room temperature, i.e. at a temperature in the range from about 20 °C to about 30 °C. The reaction may take place at a temperature as low as about 10°C. However, the reaction proceeds faster at higher temperatures. Thus, in step (b), a temperature in the range from about 10°C to about 200°C may be used, but a temperature in the range from about 20°C to about 150°C is more preferable and a temperature in the range from about 50°C to about 150°C is even more preferable. It will be appreciated that the pressures and temperatures referred to above apply in the context of the same process and not to separate embodiments. Thus in the process of the invention, methane may be added to the reaction vessel at a pressure in the range from about 1 bar to about 100 bar, even more preferably in the range from about 1 bar to about 50 bar and the temperature in step (b) of the same process may then be in the range from about 10°C to about 200°C, preferably in the range from about 20°C to about 150°C and more preferably in the range from about 50°C to about 150°C. The process may therefore involve adding methane in step (a) at a pressure in the range from about 1 bar to about 100 bar and allowing the methane to react with the iodine(III) compound at a temperature in the range from about 20°C to about 150°C. A particularly preferred implementation of the process is for the methane to be added at a pressure in the range from about 1 bar to about 50 bar and for the temperature in step (b) to be in the range from about 50°C to about 150°C. The pressure at which NO2 is added to the reaction vessel in step (c) is not particularly critical, but it may be added at a pressure of at least about 0.5 bar, preferably in the range from 0.5 bar to 10 bar. Preferably, NO2 is added to the reaction vessel after step (b), after the formation of I2. The formation of I2 may be determined by UV-visible spectroscopy or conductivity measurements, preferably by UV-visible spectroscopy. In some acidic media, such as triflic acid, the formation of I2may be detected visually, by the formation of a precipitate of I2. Step (c) of the process may involve degassing the reaction vessel before NO2 is added. This avoids mixing methane with the oxidant NO2, which is preferable from a safety perspective. The reaction vessel may be degassed by any standard degassing process. An example of a suitable degassing process is to use a freeze-thaw process, in which the reaction mixture is frozen and the headspace in the reaction vessel is evacuated under vacuum using a vacuum pump. The reaction vessel is then sealed off from the vacuum pump but left under static vacuum, and the solution allowed to thaw, thus drawing gas out of the solution. The solution is then frozen again and the headspace evacuated using the vacuum pump. This may preferably be repeated several times (e.g. two to four times) to degas the reaction mixture thoroughly. Other known methods of degassing may be used instead, such a sparging with inert gas. The use of NO2makes the process catalytic because it regenerates the iodine(III) compound. The process may therefore be performed in a continuous manner in which the process further comprises: (d) adding further methane to the reaction vessel after adding NO2 to the reaction vessel in step (c); (e) allowing the methane to react with the iodine(III) compound in the reaction mixture formed in step (d); (f) adding further NO2 to the reaction vessel during or after step (e); and (g) repeating steps (d) to (f). The same pressure and temperature defined above for steps (a) and (b), respectively, may be used for steps (d) and (e), respectively. Similarly, like step (c), step (f) may involve degassing the reaction vessel before adding further NO2. NO2may be added in step (c) and step (f) (if the process involves step (f)) at any temperature, but preferably the solution is cooled to below 0 °C before NO2 is added and more preferably the solution is cooled to below -50 °C before NO2 is added. Preferably, the process further comprises adding O2to regenerate NO2. As explained above, when NO2oxidises I2 to I(III), it is reduced to NO and O2 reacts with NO to make NO2. O2 and NO2 may both be added to the reaction vessel in step (c) before any further methane is added. O2 and NO2 may both be added to the reaction vessel in step (f). If NO2and O2are both added to the reaction vessel in step (c) and / or step (f), the reaction vessel is preferably degassed first. This avoids O2and NO2mixing with methane, which is preferable from a safety perspective. It is more preferable for O2not to be added to the reaction vessel in which methane is reacted with the iodine(III) compound, for safety reasons. Therefore, preferably, NO2is regenerated by transferring the NO formed in the process to a separate vessel and mixing it with O2 in that vessel to form NO2. No catalyst is needed to catalyse the reaction of NO with O2 to form NO2. Therefore, preferably, no catalyst is used to catalyse the reaction of NO with O2to form NO2. However, optionally, a catalyst may be used for this process. The NO2can then be returned to the reaction vessel. Process for producing methanol using I2 in acid Methanol may also be produced using similar chemistry to that described above, wherein the iodine(III) compound is formed in situ by adding NO2 to a solution of elemental iodine (I2) in acid. Accordingly, the present invention provides a process for producing methanol comprising: (a) adding NO2to a solution of I2in acid in a reaction vessel, wherein the acid is H2SO4 / SO3or wherein the acid is an acid having the formula RSO3H, RCO2H or HN(SO2R)2, wherein R is a C1-8 alkyl group optionally substituted with one or more halogen atoms, wherein said acid is an acid that has a pKa of less than 3 on the aqueous scale or the acid is an acid that has a Hammett acidity function (H0) of less than -2; (b) adding methane to the reaction vessel; and (c) allowing the methane to react with the reaction mixture formed in step (a). The process may further comprise: (d) adding further NO2 to the reaction vessel after step (c) or adding O2 to regenerate NO2; (e) adding further methane to the reaction vessel during or after step (d); (f) allowing the methane to react with the reaction mixture formed in step (e); and (g) repeating steps (d) to (f) The addition of NO2 to the solution of I2 in acid in step (a) oxidises the iodine to the +3 oxidation state and forms a compound of the formula I(OSO2R)3, I(OC(O)R)3or I[N(SO2R)2]3(depending on the acid used), which can then act as a catalyst for the conversion of methane to methanol in the same way as described in detail above starting from the iodine(III) compound. The solution may be degassed after step (a), before adding the methane in step (b). The solution may also be degassed after step (c), before adding the further NO2in step (d). Degassing may be carried out by any suitable process as described in detail above, for example by a freeze-thaw process. Since the chemistry is very similar to that described above starting from an iodine(III) compound, except for the fact that the iodine(III) compound is formed in situ, the reaction can be conducted at the same temperature and pressure as described above. Methane may be added to the reaction vessel in step (b) and in step (e) (if step (e) is performed) at the same pressure as defined above for step (a) of the process starting from an iodine(III) compound. Also, the methane may be allowed to react in step (c) and step (f) (if step (f) is performed) at the same temperature as defined above for step (b) of the process starting from an iodine(III) compound. Therefore, the temperatures and pressures defined above apply mutatis mutandis to the process starting with the addition of NO2 to I2 in acid. Similar to the process described above starting from an iodine(III) compound, the process preferably further comprises adding O2 to regenerate NO2. As explained above, when NO2 oxidises I2 to I(III), it is reduced to NO and the NO can then be reacted with O2 to make NO2. O2 may be added to the reaction vessel after step (c) to regenerate NO2. O2may be added to the reaction vessel after step (f) to regenerate NO2. If O2is added to the reaction vessel after step (c) and / or step (f), the reaction vessel is preferably degassed first. This avoids O2mixing with methane, which is preferable from a safety perspective. It is more preferable for O2not to be added to the reaction vessel in which methane is reacted with the iodine(III) compound, for safety reasons. Therefore, preferably, NO2is regenerated by transferring the NO formed in the process to a separate vessel and mixing it with O2 in that vessel to form NO2. Preferably, a catalyst is used to catalyse the reaction of NO with O2 to form NO2. Suitable catalysts are well-known to those skilled in the art. The NO2can then be returned to the reaction vessel. In any of the processes described above for making methanol, the methane is preferably reacted with the iodine(III) compound for a duration of at least one minute. The methane may be reacted with the iodine(III) compound for a time in the range from 1 minute to 24 hours, for example a time in the range from 1 minute to 2 hours.Longer reaction times in the range from about 12 hours to about 24 hours may be used if desired, although it is not typically required to use such an extended reaction time. In both of the processes described above, the methanol product formed in the reaction can be separated from the reaction mixture. Preferably, this takes place by distillation. The distillation of methanol out of the reaction mixture drives the equilibrium in the reaction mixture between MeX and MeOH (see above) towards the production of more methanol. The acid that remains after distillation can be recycled for use in further reactions by adding more iodine(III) catalyst and methane. Alternatively, the MeX product may be distilled out of the reaction mixture and subsequently hydrolysed to form methanol, for example by the addition of water to the MeX obtained by distillation. In the case where triflic acid, TfOH, is used as the acid, a solid complex may be formed between methanol and the triflic acid. The formation of this complex allows methanol to isolated in a particularly straightforward manner by separation of the solid complex from the reaction mixture. This is a particular advantage of using TfOH as the acid in the process. Water may be added to the reaction mixture in order to hydrolyse any methyl esters completely to methanol. However, this is not a preferred way of carrying out the process in an industrial setting, in part because it may make the separation of methanol from the reaction mixture more difficult. It is preferred to separate methanol from the reaction mixture, for example by distillation, as described above, which drives the equilibrium between the methyl ester and methanol towards the production of more methanol. Iodine(III) compound for use in the process of producing methanol The process involves adding methane to an iodine(III) compound in acid in a reaction vessel. The iodine in the iodine(III) compound is bonded to at least one -OSO2R, -OC(O)R or -N(SO2R)2 group, wherein R is a C1-8 alkyl group optionally substituted with one or more halogen atoms, or the iodine(III) compound may be I(SO4)(HSO4). The iodine(III) compound can be made by methods well known to those skilled in the art. The synthesis of iodine(III) compounds including I(O2CCH3)3, I(O2CCF3)3, I(O2CCH2Cl)3and I(OTf)3is reported in Inorganic Chemistry, vol.28, no.4, 1989, and other iodine(III) compounds for use in the present invention can be synthesised analogously or by other methods known to those skilled in the art. I(SO4)(HSO4) may be prepared from the reaction of I(TFA)3with H2SO4 / SO3, as described below in example 9. It is not vital for all groups attached to iodine in the iodine(III) compound to be -OSO2R, -OC(O)R or -N(SO2R)2groups. The iodine in the iodine(III) compound may, for example, be bonded to one or more aryl (Ar) groups. Thus, the iodine(III) compound may, for example, be of the formula ArIZ2or Ar2IZ, where Z is -OSO2R, -OC(O)R or -N(SO2R)2. Ar is preferably a phenyl group, more preferably a substituted phenyl group, wherein the substituents are preferably nitro or halo groups. Such iodine(III) compounds may be synthesised by known methods, for example those reported in J. Am. Chem. Soc.2016, 138, 39, 12747–12750. Especially preferred Ar groups are C6F5or p-NO2C6H4, i.e. the iodine(III) compound may be of the formula (C6F5)IZ2, (C6F5)2IZ, (p-NO2C6H4)IZ2 or (p NO2C6H4)2IZ, where Z is as defined above. However, except in the case where the iodine(III) compound is I(SO4)(HSO4), the iodine(III) compound is very preferably homoleptic, meaning that all three substituents on the iodine atom are the same. In other words, the iodine(III) compound very preferably is I(SO4)(HSO4) or has the formula I(OSO2R)3, I(OC(O)R)3 or I[N(SO2R)2]3; even more preferably it is I(SO4)(HSO4) or has the formula I(OSO2R)3 or I[N(SO2R)2]3. R is a C1-8alkyl group optionally substituted with one or more halogen atoms. Preferred R groups are perfluorinated C1-8 alkyl groups or C1-4 alkyl groups substituted with at least one halogen atom. More preferred R groups have the formula CnF2n+1 or CnCl2n+1, wherein n is 1-4, even more preferably wherein n is 1 or 2. R groups of the formula CnF2n+1are more preferred than R groups of the formula CnCl2n+1, so more preferably, R has the formula CnF2n+1, wherein n is 1-4, even more preferably wherein n is 1 or 2. It is especially preferred that R is CF3. The iodine(III) compound may have the formula I(OSO2R)3or I[N(SO2R)2]3, wherein R is a perfluorinated C1-8alkyl group or a C1-4alkyl group substituted with at least one halogen atom. The iodine(III) compound may have the formula I(OSO2R)3 or I[N(SO2R)2]3, wherein R has the formula CnF2n+1 or CnCl2n+1, wherein n is 1-4, preferably wherein n is 1 or 2. The iodine(III) compound I(SO4)(HSO4) has been found to be highly effective for the oxidation of methane, as illustrated in the examples. Therefore, a preferred iodine(III) compound is I(SO4)(HSO4). As shown in example 10 below, I(SO4)(HSO4) may be prepared in situ from I(CF3CO2)3(also known as I(TFA)3) and H2SO4 / SO3(oleum), and the resultant solution shows excellent activation of methane under mild conditions (i.e. a pressure of about 1 bar and a temperature of about 65oC). Hence, in another preferred implementation of the invention, the iodine(III) compound is I(CF3CO2)3 and the acid is H2SO4 / SO3. The reaction of I(SO4)(HSO4) with methane produces methyl bisulfate if no NO2is present, but in the process of the invention described above for making methanol which involves using NO2, the presence of NO2 leads to the formation of water in situ, which hydrolyses methyl bisulfate in situ to form methanol. The reaction mixture then contains a mixture of methyl bisulfate and methanol, and methanol can be isolated from the reaction mixture if desired, for example by distillation. Therefore, I(SO4)(HSO4) may be used to produce methyl bisulfate or methanol, depending on the reaction conditions. The most preferred iodine(III) compounds for use in the process of producing methanol are I(OTf)3, I(SO4)(HSO4) and I(NTf2)3, especially I(OTf)3and I(SO4)(HSO4). Acids for use in the process of producing methanol As explained above, the process of producing methanol may involve adding methane to a solution of an iodine(III) compound in acid followed by the addition of NO2, or may involve adding NO2 to a solution of I2 in acid. In these processes, the acid is an acid that has a pKa of less than 3 on the aqueous pKa scale or is an acid that has a Hammett acidity function (H0) of less than -2, preferably an acid that has a pKa of less than 3 on the aqueous pKa scale. It has been found that such acids are sufficiently acidic to (i) facilitate the effective reaction of the iodine(III) compound with the alkane and (ii) lead to the generation of water when NO2oxidises the I2that is produced when the iodine(III) compound reacts with the alkane back to an iodine(III) compound, which enables the production of methanol in situ. Preferably, the acid is an acid that has a pKa of less than 3 on the aqueous scale. Preferably, the pKa of the acid is less than 1 on the aqueous pKa scale, more preferably less than 0 and most preferably less -1 on the aqueous pKa scale. As will be appreciated by those skilled in the art, the pKa of acids are very widely reported and can readily be found in standard reference texts. Those skilled in the art will be aware of many acids which have a pKa on the aqueous scale of less than 3, less than 1, less than 0 or less than -1, and would readily be able to identify such acids on the basis of their common general knowledge. The acid may be an acid that has a Hammett acidity function (H0) of less than -2. Preferably, the Hammett acidity function (H0) is less than -6, more preferably less than -10. As will be appreciated by those skilled in the art, the Hammett acidity function (H0) of many acids are widely reported and can readily be found in standard reference texts. H0values can be determined using routine methods, such as that described above. Those skilled in the art will be aware of many acids which have a Hammett acidity function (H0) of less than -2, less than -6 or less than -10 and would readily be able to identify such acids on the basis of their common general knowledge. As those skilled in the art will understand, many acids will have a pKa of less than 3 on the aqueous scale and a Hammett acidity function (H0) of less than -2. However, there may be some acids that only satisfy one or other of these requirements, but not both, and such acids are within the scope of the present invention. It is especially preferred that the acid is the conjugate acid of the -OSO2R, -OC(O)R or -N(SO2R)2 group that is attached to the iodine atom in the iodine(III) compound. This applies especially when the iodine(III) compound is homoleptic, i.e. has the formula I(OSO2R)3, I(OC(O)R)3or I[N(SO2R)2]3The acid may be a weaker acid than the conjugate acid of the -OSO2R, -OC(O)R or -N(SO2R)2 group that is attached to the iodine atom in the iodine(III) compound, providing the acid has a pKa on the aqueous scale of less than 3, preferably less than 1, or is an acid that has a Hammett acidity function (H0) of less than -2; using a weaker acid than the conjugate acid is less preferred than using the conjugate acid but still leads to an efficient reaction. Using a weaker acid than the conjugate acid of the -OSO2R, -OC(O)R or -N(SO2R)2 group that is attached to the iodine atom in the iodine(III) compound drives the equilibrium between MeX and MeOH towards the production of MeOH. It is therefore preferable not to use an acid that is a stronger acid than the conjugate acid of the -OSO2R, -OC(O)R or -N(SO2R)2 group that is attached to the iodine atom in the iodine(III) compound, although this is still feasible. HN(SO2CF3)2, commonly known as bistriflimidic acid, is a solid at room temperature and melts at around 46- 57 °C. As one skilled in the art will appreciate, when using this acid or any other acid that is a solid at room temperature, it is necessary to conduct the reaction at a temperature above the melting point of the acid, i.e. the acid should remain above the melting point of the acid while the reaction takes place. Therefore, when the acid is HN(SO2CF3)2, it is preferred for the reaction to be conducted at a temperature of at least about 50 °C, preferably in the range from about 50 °C to about 150 °C and more preferably in the range from about 60 °C to about 150 °C. In the process of producing methanol that involves adding NO2to a solution of I2in acid, the acid is an acid having the formula RSO3H, RCO2H or HN(SO2R)2, or the acid may be H2SO4 / SO3. Those skilled in the art will be well aware from their common general knowledge which of these acids have a pKa of less than 3 or a Hammett acidity value of less than -2. R is a C1-8alkyl group optionally substituted with one or more halogen atoms. Preferably, R is a C1-8alkyl group that is substituted with one or more halogen atoms. Preferred R groups are perfluorinated C1-8 alkyl groups or C1-4 alkyl groups substituted with at least one halogen atom. More preferred R groups have the formula CnF2n+1 or CnCl2n+1, wherein n is 1-4, even more preferably wherein n is 1 or 2. R groups of the formula CnF2n+1are more preferred than R groups of the formula CnCl2n+1, so more preferably, R has the formula CnF2n+1, wherein n is 1-4, even more preferably wherein n is 1 or 2. It is especially preferred that R is CF3. The specific acids listed below as suitable acids to use in the processes of the invention for the production of methanol may be used in the process of producing methanol that involves adding NO2to a solution of I2in acid, as well as in the process for making methanol involving adding methane to a solution of an iodine(III) compound in acid. The acid may be a carboxylic acid or a sulfonic acid or HNO3, wherein the carboxylic acid or sulfonic acid has a pKa of less than 3 on the aqueous scale or wherein the carboxylic acid or sulfonic acid has a Hammett acidity function (H0) of less than -2. Sulfonic acids include H2SO4, which may contain dissolved SO3 (i.e. oleum). The carboxylic acid or sulfonic acid may contain a halogenated alkyl or aryl group, preferably wherein the halogen atoms are fluorine or chlorine atoms. More preferably, the acid is a perfluorinated C1-8 alkyl sulfonic acid or perfluorinated C1-8 alkyl carboxylic acid, such as a perfluorinated C1-4 alkyl sulfonic acid or perfluorinated C1-4alkyl carboxylic acid. The use of acids which boil at a higher temperature than methanol (BPT = 65 °C at atmospheric pressure) is preferred because it facilitates simpler distillation of methanol from the reaction mixture. Perfluorinated C1-8 alkyl sulfonic acids and perfluorinated C1-8alkyl carboxylic acids are useful because they have sufficient acidity whilst having high boiling points and therefore the reaction proceeds well in these solvents and the methanol can easily be separated from the reaction mixture. In order to assist with facile separation of methanol from the reaction mixture by distillation, the acid may be a perfluorinated C5-8 alkyl sulfonic acid or a perfluorinated C5-8 alkyl carboxylic acid. Another useful acid medium to use in the reaction is H2SO4 / SO3 (oleum). As explained in further detail below, the reaction of the iodine(III) compound with methane in oleum yields methyl bisulfate, but when NO2 is added, water is formed in situ which hydrolyses the methyl bisulfate to methanol, setting up an equilibrium between methyl bisulfate and methanol. Methanol can be distilled off from the reaction mixture, which drives the equilibrium towards the production of more methanol. As shown in the examples section, the use of oleum leads to especially high yields of methyl bisulfate when NO2 is used in the process; the methyl bisulfate is present in equilibrium with methanol, which can be separated from the reaction mixture by distillation. Alternatively, water or another aqueous medium may be added to hydrolyse all the methyl bisulfate to methanol, although this is less preferred. As explained above, I(SO4)(HSO4) and I(TFA)3have shown particularly good results in H2SO4 / SO3(oleum), and therefore the iodine(III) compound may be I(SO4)(HSO4) or I(TFA)3, wherein the acid is H2SO4 / SO3. Examples of suitable acids to use in the processes of the invention for the production of methanol include CF3SO3H, CH3SO3H, CF3CF2SO3H, CF3CF2CF2SO3H, CF3(CF2)3SO3H, CF3(CF2)4SO3H, CF3(CF2)5SO3H, CF3(CF2)6SO3H, CF3(CF2)7SO3H, CF3CO2H, CF3CF2CO2H, CF3CF2CF2CO2H, CF3(CF2)3CO2H, CF3(CF2)4CO2H, CF3(CF2)5CO2H, CF3(CF2)6CO2H, CF3(CF2)7CO2H, CCl3CO2H, HN(SO2CF3)2, HN(SO2CF2CF3)2, FSO3H, H2SO4 / SO3 or HNO3. Preferably, the acid may be selected from the group consisting of CF3SO3H, CH3SO3H, CF3CF2SO3H, CF3CF2CF2SO3H, CF3CO2H, CF3CF2CO2H, CF3CF2CF2CO2H, CCl3CO2H, HN(SO2CF3)2, HN(SO2CF2CF3)2, FSO3H, H2SO4 / SO3 or HNO3. More preferably, the acid may be selected from the group consisting of CF3SO3H, CH3SO3H, CF3CF2SO3H, CF3CO2H, CF3CF2CO2H, FSO3H or H2SO4 / SO3, even more preferably CF3SO3H or H2SO4 / SO3. A particularly preferred acid to use in the process is triflic acid (CF3SO3H). It will be appreciated that the acids disclosed in this section can be used in conjunction with the iodine(III) compounds disclosed in the previous section. The iodine(III) compound preferably fully dissolves in the acid at the temperature at which the reaction with methane takes place, but that is not essential. It is preferred for (i) the iodine(III) compound to have the formula I(OSO2R)3, I(OC(O)R)3 or I[N(SO2R)2]3, wherein R is a C1-8 alkyl group optionally substituted with one or more halogen atoms, or for the iodine(III) compound to be I(SO4)(HSO4), and (ii) for the acid to be a perfluorinated C1-8alkyl sulfonic acid or a perfluorinated C1-8alkyl carboxylic acid or for the acid to be H2SO4 / SO3. As explained in the previous section, the iodine(III) compound may be I(OTf)3, I(SO4)(HSO4) or I(NTf2)3, with I(OTf)3being especially preferred. When one of these iodine(III) compounds is used, any of the acids listed above may be used, such as (but not limited to) CF3SO3H, CH3SO3H, CF3CF2SO3H, CF3CF2CF2SO3H, CF3(CF2)3SO3H, CF3(CF2)4SO3H, CF3(CF2)5SO3H, CF3(CF2)6SO3H, CF3(CF2)7SO3H, CF3CO2H, CF3CF2CO2H, CF3CF2CF2CO2H, CF3(CF2)3CO2H, CF3(CF2)4CO2H, CF3(CF2)5CO2H, CF3(CF2)6CO2H, CF3(CF2)7CO2H, CCl3CO2H, HN(SO2CF3)2, HN(SO2CF2CF3)2, FSO3H, H2SO4 / SO3or HNO3. The acid used in conjunction with I(OTf)3, I(SO4)(HSO4) or I(NTf2)3, especially I(OTf)3, may be selected from the group consisting of CF3SO3H, CH3SO3H, CF3CF2SO3H, CF3CF2CF2SO3H, CF3CO2H, CF3CF2CO2H, CF3CF2CF2CO2H, CCl3CO2H, HN(SO2CF3)2, HN(SO2CF2CF3)2, FSO3H, H2SO4 / SO3 or HNO3, or may be selected from the group consisting of CF3SO3H, CH3SO3H, CF3CF2SO3H, CF3CO2H, CF3CF2CO2H, FSO3H or H2SO4 / SO3. In a preferred implementation of the invention, the iodine(III) compound is I(SO4)(HSO4) or I(TFA)3 and the acid is H2SO4 / SO3. In a preferred implementation of the invention, the iodine(III) compound is I(OTf)3and the acid is CF3SO3H, or the iodine(III) compound is I(NTf2)3 and the acid is HNTf2. Even more preferably, the iodine(III) compound is I(OTf)3 and the acid is CF3SO3H. Preferably, the solution of the iodine(III) compound in acid does not contain chloride ions. One advantage of the process of the present invention over the work of Periana et al described in J. Am. Chem. Soc.2014, 136, 8393- 8401, which is discussed in the background section, is that the process of the present invention does not require the presence of chloride ions to obtain a high yield of methyl ester (which is hydrolysed to methanol in situ). As will be appreciated, the process of the invention has numerous other advantages over that prior work, particularly the production of methanol in situ, the catalytic nature of the process with respect to iodine and the fact that the reaction proceeds under much milder conditions. The volume of acid used is not particularly critical but may be in the range of 10-5000 mL / g relative to the mass of iodine(III) compound, for example in the range of 50-1000 mL / g relative to the mass of iodine(III) compound. The present invention provides a process for producing methanol comprising: (a) adding methane to a solution of an iodine(III) compound in acid in a reaction vessel, wherein the iodine(III) compound has the formula I(OSO2R)3, I(OC(O)R)3 or I[N(SO2R)2]3, wherein R is a C1-8 alkyl group optionally substituted with one or more halogen atoms, or wherein the iodine(III) compound is I(SO4)(HSO4), wherein the acid is a perfluorinated C1-8 alkyl sulfonic acid or a perfluorinated C1-8 alkyl carboxylic acid or wherein the acid is H2SO4 / SO3; (b) allowing the methane to react with the iodine(III) compound in the reaction mixture formed in step (a); and (c) adding NO2 to the reaction vessel. The preferences explained above for the definition of the iodine(III) compound, R and the acid apply to this implementation of the invention described immediately above. In this implementation of the invention, the most preferred iodine(III) compounds are I(OTf)3, I(NTf2)3 or I(SO4)(HSO4) and the most preferred acids are CF3SO3H or H2SO4 / SO3; also preferred is the iodine(III) compound being I(CF3CO2)3 and the acid being H2SO4 / SO3. Process for the preparation of CH3X or XCH2CH2X and process for the preparation of ethylene glycol The invention provides a process for the preparation of a compound of the formula CH3X or XCH2CH2X comprising reacting methane or ethane with an iodine(III) compound, wherein X is -OSO2R or -N(SO2R)2and wherein the iodine in the iodine(III) compound is bonded to at least one X group, wherein R is a C1-8 alkyl group optionally substituted with one or more halogen atoms. As explained above, the reaction of methane with an iodine(III) compound in which the iodine in the iodine(III) compound is bonded to at least one -OSO2R or -N(SO2R)2 group results in the formation of a compound of the formula CH3OSO2R or CH3N(SO2R)2. Performing the same reaction with ethane instead of methane leads to the production of a compound of the formula XCH2CH2X, wherein X is -OSO2R or -N(SO2R)2. The reaction cleanly and selectively yields the XCH2CH2X difunctionalised compound, rather than the monofunctionalised XCH2CH3, or a mixture of the monofunctionalised and difunctionalised compounds. This is a significant advantage over known ethane oxidation systems, which typically yield a mixture of mono- and bis-functionalised alkanes, and often the monofunctionalised product is stable in the oxidising solution and is not oxidised to the bis-functionalised product. However, in the process of the present invention, the monofunctionalised compound is unstable in the oxidising solution and is further functionalised to the difunctionalised compound. This facilitates simpler separation of the desired difunctionalised compound, avoiding expensive separation steps. Performing the reaction in the solid state The process for the preparation of CH3X or XCH2CH2X may be performed by passing methane or ethane gas over the iodine(III) compound in the solid state. The reaction in which methane or ethane gas is passed over the iodine(III) compound in the solid state may proceed at room temperature, i.e. a temperature in the range from about 20oC to about 30oC, but proceeds faster at elevated temperatures. It is therefore preferable to perform the reaction at a temperature in the range from about 50oC to about 150oC, more preferably at a temperature in the range from about 75oC to about 125oC. There is no particular upper limit on the pressure that may be used for the reaction of methane or ethane gas with the iodine(III) compound in the solid state, and this will largely be dictated by the nature of the reaction vessel used. The iodine(III) compound is present in a reaction vessel and the methane or ethane may be added to the reaction vessel at any pressure of about 0.5 bar or above, preferably in the range from about 0.5 bar to about 200 bar. More preferably, the methane or ethane is added to the reaction vessel at a pressure in the range from about 1 bar to about 100 bar, even more preferably in the range from about 1 bar to about 50 bar. A pressure of about 1 bar to about 50 bar may be particularly suitable for industrial applications. The reaction may thus be performed at a temperature in the range from about 50oC to about 150oC, more preferably at a temperature in the range from about 75oC to about 125oC, wherein methane or ethane gas is added to the reaction vessel at a pressure in the range from about 1 bar to about 100 bar, even more preferably in the range from about 1 bar to about 50 bar. Thus methane or ethane gas may be added to the reaction vessel at a pressure in the range from about 1 bar to about 50 bar and the reaction may then be performed at a temperature in the range from about 50oC to about 150oC. The iodine(III) compound may be incorporated into a catalyst support material, such as silica or a zeolite. Such catalyst support systems are well known to those skilled in the art and any suitable catalyst support system may be used in the process of the invention. NO2 may be added to the reaction vessel after the iodine(III) compound has reacted with the methane or ethane gas, in order to regenerate the iodine(III) compound. Preferably, the methane or ethane gas is evacuated from the reaction vessel before NO2is added. This is preferable for safety reasons. The CH3X or XCH2CH2X product may be decanted as a liquid from the reaction vessel or may be washed out of the reaction vessel using a solvent. Performing the reaction in solution The reaction to form CH3X or XCH2CH2X may be performed in solution instead of in the solid state. The invention thus provides a process for the preparation of a compound of the formula CH3X or XCH2CH2X comprising adding methane or ethane to a solution of the iodine(III) compound in acid in a reaction vessel, wherein the acid is an acid that has a pKa of less than 3 on the aqueous scale or the acid is an acid that has a Hammett acidity function (H0) of less than -2, providing that the acid is not H2SO4 / SO3, wherein X is -OSO2R or -N(SO2R)2 and wherein the iodine in the iodine(III) compound is bonded to at least one X group, wherein R is a C1-8 alkyl group optionally substituted with one or more halogen atoms. As explained above in the context of a process for making methanol, when methane reacts with the iodine(III) compound, a compound of the formula CH3X is formed initially. In the context of the reaction for making CH3X wherein X is -OSO2R or -N(SO2R)2 as defined above, the resulting compound would have the formula CH3OSO2R or CH3N(SO2R)2(the latter is not formally an ester but may be referred to as such, including in this disclosure). When ethane is used instead of methane, the corresponding XCH2CH2X compound is formed. The process for making CH3X or XCH2CH2X described in the previous paragraph involves either (i) performing the reaction in the absence of NO2, in which case water will not be formed in situ and the CH3X or XCH2CH2X will not be hydrolysed in situ to methanol or ethylene glycol, or (ii) adding NO2to the reaction mixture, in which case water will be formed in situ and an equilibrium will be established either between CH3X and CH3OH (in the case where methane is used), or XCH2CH2X and ethylene glycol (in the case where ethane is used). However, the CH3X or XCH2CH2X can be isolated instead of the methanol or ethylene glycol. Preferably, the CH3X or XCH2CH2X is isolated by distillation. The process may further comprise forming the solution of the iodine(III) compound in acid by mixing I2 with an acid and adding NO2to the reaction vessel, wherein the acid has the formula HX. This leads to the generation of the iodine(III) compound IX3in situ, which results in the formation of a compound having the formula CH3X or XCH2CH2X in the process of the invention. The process may further comprise adding NO2to the reaction vessel. NO2acts as an oxidant to regenerate the iodine(III) compound from the I2that is formed when the iodine(III) compound reacts with methane or ethane. As explained above, the presence of NO2 leads to the formation of water in situ. When ethane is used as the starting material, some of the resulting XCH2CH2X is therefore hydrolysed to ethylene glycol. The ethylene glycol can then be separated from the reaction mixture, for example by distillation. Distillation may be performed under reduced pressure due to the relatively high boiling point of ethylene glycol (197 °C at atmospheric pressure). Accordingly, the present invention provides a process for the preparation of ethylene glycol comprising adding ethane to a solution of an iodine(III) compound in acid in a reaction vessel, wherein the iodine in the iodine(III) compound is bonded to at least one -OSO2R or -N(SO2R)2 group, wherein the acid is an acid that has a pKa of less than 3 on the aqueous scale or the acid is an acid that has a Hammett acidity function (H0) of less than -2, wherein R is a C1-8alkyl group optionally substituted with one or more halogen atoms, and wherein the process further comprises adding NO2. In the process of producing ethylene glycol, the iodine(III) compound may alternatively be I(SO4)(HSO4) or I(CF3CO2)3, in which case the acid is preferably H2SO4 / SO3, or the iodine(III) compound may be or I(CF3CO2)3, in which case the acid is H2SO4 / SO3. The process for the preparation of ethylene glycol may further comprise forming the solution of the iodine(III) compound in acid by mixing I2 with an acid and adding NO2 to the reaction vessel, wherein the acid has the formula RSO3H or HN(SO2R)2and the acid has a pKa of less than 3 on the aqueous scale or the acid is an acid that has a Hammett acidity function (H0) of less than -2, wherein R is a C1-8alkyl group optionally substituted with one or more halogen atoms. R is preferably a C1-8 alkyl group that is substituted with one or more halogen atoms. Preferred R groups are perfluorinated C1-8 alkyl groups or C1-4 alkyl groups substituted with at least one halogen atom. More preferred R groups have the formula CnF2n+1or CnCl2n+1, wherein n is 1-4, even more preferably wherein n is 1 or 2. R groups of the formula CnF2n+1are more preferred than R groups of the formula CnCl2n+1, so more preferably, R has the formula CnF2n+1, wherein n is 1-4, even more preferably wherein n is 1 or 2. It is especially preferred that R is CF3. The pressure at which NO2is added to the reaction vessel is not particularly critical, but it may be added at a pressure of at least about 0.5 bar, preferably in the range from 1 bar to 10 bar. Preferably, NO2is added to the reaction vessel after the formation of I2. The formation of I2may be determined visually, for example by the formation of a precipitate of I2or the reaction mixture turning brown. The process may involve degassing the reaction vessel before NO2 is added. This avoids mixing methane or ethane with the oxidant NO2, which is preferable from a safety perspective. The reaction vessel may be degassed by any standard degassing process as described above, for example by a typical freeze-thaw process. The use of NO2 makes the process catalytic by regenerating the iodine(III) compound. The process may therefore be performed in a continuous manner in which the process further comprises: (a) adding further methane or ethane to the reaction vessel after adding NO2to the reaction vessel; (b) allowing the methane or ethane to react with the iodine(III) compound in the reaction mixture formed in step (a); (c) adding further NO2to the reaction vessel during or after step (b); and (d) repeating steps (a) to (c). In the context of a process for making ethylene glycol, it will naturally be apparent that ethane is added in steps (a) and (b), rather than methane. The process may comprise adding O2 to regenerate NO2 from the NO that is formed when NO2 reacts with the I2 formed from the reaction of the iodine(III) compound with methane or ethane. O2may be added after each addition of NO2in order to regenerate NO2. For example, O2may be added after step (c) as well as after any previous addition of NO2 to the reaction vessel. O2and NO2may both be added to the reaction vessel. If NO2and O2are both added to the reaction vessel, the reaction vessel is preferably degassed first. This avoids O2and NO2mixing with methane or ethane, which is preferable from a safety perspective. It is more preferable for O2not to be added to the reaction vessel in which methane or ethane is reacted with the iodine(III) compound. Therefore, preferably, NO2is regenerated by transferring the NO formed in the process to a separate vessel and mixing it with O2 in that vessel to form NO2. Preferably, no catalyst is used to catalyse the reaction of NO with O2 to form NO2. However, a catalyst may be used and suitable catalysts are well-known to those skilled in the art. The NO2can then be returned to the reaction vessel. The solution phase reaction may be performed at the same temperature and pressure as described above in the context of a process for making methanol. The methane or ethane may be added at low pressure. The reaction proceeds well at 1 bar pressure and methane or ethane may therefore be added at a pressure as low as 0.5 bar. However, in an industrial context it may be preferred to use a much higher pressure in order to achieve a faster and more complete reaction. There is no particular maximum on the pressure that may be used, and this will largely be dictated by the nature of the reaction vessel used. Therefore, the methane or ethane may be added to the reaction vessel at any pressure of about 0.5 bar or above, preferably in the range from about 0.5 bar to about 200 bar or from about 0.5 bar to about 100 bar. More preferably, the methane or ethane is added to the reaction vessel at a pressure in the range from about 1 bar to about 100 bar, even more preferably in the range from about 1 bar to about 50 bar. A pressure of about 1 bar to about 50 bar is particularly suitable for industrial applications. The methane or ethane can be allowed to react with the iodine(III) compound at room temperature, i.e. at a temperature in the range from about 20 °C to about 30 °C. The reaction may be allowed to occur at a temperature as low as about 10°C. However, the reaction proceeds faster at higher temperatures. Thus, a temperature in the range from about 10°C to about 200°C may be used, but a temperature in the range from about 20°C to about 150°C is more preferable and a temperature in the range from about 50°C to about 150°C is even more preferable. It will be appreciated that the pressures and temperatures referred to above apply in the context of the same process and not to separate embodiments. Thus in the process of the invention, methane or ethane may be added to the reaction vessel at a pressure in the range from about 1 bar to about 100 bar, even more preferably in the range from about 1 bar to about 50 bar and the temperature of the reaction in the same process may then be in the range from about 10°C to about 200°C, preferably in the range from about 20°C to about 150°C and more preferably in the range from about 50°C to about 150°C. The process may therefore involve adding methane or ethane at a pressure in the range from about 1 bar to about 100 bar and allowing the methane or ethane to react with the iodine(III) compound at a temperature in the range from about 20°C to about 150°C. A particularly preferred implementation of the process is for the methane or ethane to be added at a pressure in the range from about 1 bar to about 50 bar and for the temperature at which the methane or ethane is allowed to react with the iodine(III) compound to be in the range from about 50°C to about 150°C. In any of the processes described above for making CH3X, XCH2CH2X or ethylene glycol, the methane or ethane is preferably reacted with the iodine(III) compound for a duration of at least one hour. The methane or ethane may be reacted with the iodine(III) compound for a time in the range from 1 minute to 24 hours, for example a time in the range from 1 minute to 2 hours. Longer reaction times in the range from about 12 hours to about 24 hours may be used if desired, although it is not typically required to use such an extended reaction time. The process may further comprise hydrolysing the CH3X to form CH3OH or hydrolysing the XCH2CH2X to form ethylene glycol. This may be achieved by adding water to the reaction mixture. Iodine(III) compound for use in the process of producing CH3X or XCH2CH2X or ethylene glycol In the process of preparing CH3X or XCH2CH2X or ethylene glycol, the iodine in the iodine(III) compound is bonded to at least one -OSO2R or -N(SO2R)2group, wherein R is a C1-8alkyl group optionally substituted with one or more halogen atoms. It is not vital for all groups attached to iodine in the iodine(III) compound to be -OSO2R or -N(SO2R)2groups. The iodine in the iodine(III) compound may, for example, be bonded to one or more aryl (Ar) groups. Thus, the iodine(III) compound may, for example, be of the formula ArIZ2 or Ar2IZ, where Z is -OSO2R or -N(SO2R)2. Ar is preferably a phenyl group, more preferably a substituted phenyl group, wherein the substituents are preferably nitro or halo groups. Especially preferred Ar groups are C6F5or p-NO2C6H4, i.e. the iodine(III) compound may be of the formula (C6F5)IZ2, (C6F5)2IZ, (p-NO2C6H4)IZ2or (p NO2C6H4)2IZ, where Z is as defined above. However, the iodine(III) compound is very preferably homoleptic, meaning that all three substituents on the iodine atom are the same. In other words, the iodine(III) compound very preferably has the formula I(OSO2R)3or I[N(SO2R)2]3. R is a C1-8 alkyl group optionally substituted with one or more halogen atoms. Preferred R groups are perfluorinated C1-8alkyl groups or C1-4alkyl groups substituted with at least one halogen atom. More preferred R groups have the formula CnF2n+1or CnCl2n+1, wherein n is 1-4, even more preferably wherein n is 1 or 2. R groups of the formula CnF2n+1 are more preferred than R groups of the formula CnCl2n+1, so more preferably, R has the formula CnF2n+1, wherein n is 1-4, even more preferably wherein n is 1 or 2. It is especially preferred that R is CF3. The most preferred iodine(III) compounds for use in the process of producing ethylene glycol are I(OTf)3, I(SO4)(HSO4) or I(NTf2)3, especially I(SO4)(HSO4) or I(OTf)3. The most preferred iodine(III) compounds for use in the process of producing CH3X or XCH2CH2X are I(OTf)3, or I(NTf2)3. A preferred implementation of the process for the preparation of CH3X or XCH2CH2X or ethylene glycol is for the iodine(III) compound to be I(OTf)3 and for the acid to be HOTf. As mentioned above, in the process of making ethylene glycol, another preferred iodine(III) compound is I(SO4)(HSO4). When the iodine(III) compound is I(SO4)(HSO4), the preferred acid is H2SO4 / SO3. I(SO4)(HSO4) may be made in situ from I(CF3CO2)3 and H2SO4 / SO3, so in another preferred implementation of the process of making ethylene glycol, the iodine(III) compound is I(CF3CO2)3 and the acid is H2SO4 / SO3. The present invention provides a process for the preparation of CH3OTf comprising adding methane to a solution of I(OTf)3 in acid in a reaction vessel, wherein the acid is an acid that has a pKa of less than 3 on the aqueous scale, preferably less than 1 on the aqueous scale, or the acid is an acid that has a Hammett acidity function (H0) of less than -2. Preferably, the acid is triflic acid (CF3SO3H, also known as HOTf). The process may involve adding methane to the reaction vessel at a pressure in the range from 0.5 bar to about 100 bar and allowing the methane to react with the I(OTf)3 at a temperature in the range from about 20°C to about 150°C. More preferably, the process involves adding methane at a pressure in the range from about 1 bar to about 50 bar and allowing the methane to react with the I(OTf)3at a temperature in the range from about 20°C to about 150°C. A particularly preferred implementation of the process is for the methane to be added at a pressure in the range from about 1 bar to about 50 bar and for the allowing temperature at which the methane is allowed to react with the I(OTf)3to be in the range from about 50°C to about 150°C. The present invention provides a process for the preparation of (OTf)CH2CH2(OTf) comprising adding ethane to a solution of I(OTf)3 in acid in a reaction vessel, wherein the acid is an acid that has a pKa of less than 3 on the aqueous scale, preferably less than 1 on the aqueous scale, or the acid is an acid that has a Hammett acidity function (H0) of less than -2. Preferably, the acid is triflic acid (CF3SO3H, also known as HOTf). The process may involve adding ethane to the reaction vessel at a pressure in the range from 0.5 bar to about 100 bar and allowing the ethane to react with the I(OTf)3 at a temperature in the range from about 20°C to about 150°C. More preferably, the process involves adding ethane at a pressure in the range from about 1 bar to about 100 bar and allowing the ethane to react with the I(OTf)3 at a temperature in the range from about 20°C to about 150°C. A particularly preferred implementation of the process is for the ethane to be added at a pressure in the range from about 1 bar to about 50 bar and for the allowing temperature at which the ethane is allowed to react with the I(OTf)3to be in the range from about 50°C to about 150°C. The present invention provides a process for the preparation of ethylene glycol comprising adding ethane to a solution of I(OTf)3in acid in a reaction vessel, wherein the acid is an acid that has a pKa of less than 3 on the aqueous scale, preferably less than 1 on the aqueous scale, or the acid is an acid that has a Hammett acidity function (H0) of less than -2, wherein the process further comprises adding NO2 to the reaction vessel. Preferably, the acid is triflic acid (CF3SO3H, also known as HOTf). The process may involve adding ethane to the reaction vessel at a pressure in the range from 0.5 bar to about 100 bar and allowing the ethane to react with the I(OTf)3at a temperature in the range from about 20°C to about 150°C. More preferably, the process involves adding ethane at a pressure in the range from about 1 bar to about 100 bar and allowing the methane or ethane to react with the I(OTf)3at a temperature in the range from about 20°C to about 150°C. A particularly preferred implementation of the process is for the ethane to be added at a pressure in the range from about 1 bar to about 50 bar and for the allowing temperature at which the ethane is allowed to react with the I(OTf)3 to be in the range from about 50°C to about 150°C. The process for preparing ethylene glycol by adding ethane to a solution of I(OTf)3in HOTf may further comprise: (a) adding further ethane to the reaction vessel after adding NO2 to the reaction vessel; (b) allowing the ethane to react with the I(OTf)3in the reaction mixture formed in step (a); (c) adding further NO2to the reaction vessel during or after step (b); and (d) repeating steps (a) to (c). Acids for use in the process of producing CH3X or XCH2CH2X or ethylene glycol The acid is an acid that has a pKa of less than 3 on the aqueous pKa scale or the acid is an acid that has a Hammett acidity function (H0) of less than -2; preferably the acid is an acid that has a pKa of less than 3 on the aqueous pKa scale. Preferably, the acid has a pKa of less than 3 on the aqueous pKa scale, more preferably less than 1 and even more preferably less than 0 and most preferably less than -1. The acid may be an acid that has a Hammett acidity function (H0) of less than -2, preferably less than -6 and more preferably less than -10. As explained above, those skilled in the art will be well aware of such acids from their common general knowledge. In the process of producing CH3X or XCH2CH2X, the acid is not H2SO4 / SO3and preferably is not H2SO4. This is because the use of H2SO4 / SO3as the acid leads to the production of compounds of the formula CH3OSO3H or HOSO3CH2CH2OSO3H. The iodine(III) compound preferably fully dissolves in the acid at the temperature that the reaction with methane or ethane takes place, but that is not essential. It is especially preferred that the acid is the conjugate acid of the -OSO2R or -N(SO2R)2 group that is attached to the iodine atom in the iodine(III) compound. This applies especially when the iodine(III) compound is homoleptic, i.e. has the formula I(OSO2R)3or I[N(SO2R)2]3. Alternatively, the acid may be a weaker acid than the conjugate acid of the -OSO2R or -N(SO2R)2 group that is attached to the iodine atom in the iodine(III) compound, providing the acid has a pKa on the aqueous scale of less than 3 or is an acid that has a Hammett acidity function (H0) of less than -2. Using a weaker acid than the conjugate acid of the -OSO2R or -N(SO2R)2 group that is attached to the iodine atom in the iodine(III) compound drives the equilibrium between MeX and MeOH towards the production of MeOH (and similarly drives the equilibrium between XCH2CH2X and HOCH2CH2OH towards the production of HOCH2CH2OH). In the process for producing ethylene glycol, it is therefore preferable not to use an acid that is a stronger weaker acid than the conjugate acid of the -OSO2R or -N(SO2R)2 group that is attached to the iodine atom in the iodine(III) compound, although this is still feasible. HN(SO2CF3)2, commonly known as bistriflimidic acid, is a solid at room temperature and melts at around 46-57 °C. As one skilled in the art will appreciate, when using this acid or any other acid that is a solid at room temperature, it is necessary to conduct the reaction at a temperature above the melting point of the acid, i.e. the temperature should remain above the melting point of the acid while the reaction takes place. The acid may be a carboxylic acid or a sulfonic acid or HNO3, wherein the carboxylic acid or sulfonic acid has a pKa of less than 3 on the aqueous scale or wherein the carboxylic acid or sulfonic acid has a Hammett acidity function (H0) of less than -2. Sulfonic acids include H2SO4, which may contain dissolved SO3(i.e. oleum). The carboxylic acid or sulfonic acid may contain a halogenated alkyl or aryl group, preferably wherein the halogen atoms are fluorine or chlorine atoms. More preferably, the acid is a perfluorinated C1-8 alkyl sulfonic acid or perfluorinated C1-8alkyl carboxylic acid. The perfluorinated C1-8alkyl sulfonic acid or perfluorinated C1-8alkyl carboxylic acid may be a perfluorinated C1-4alkyl sulfonic acid,perfluorinated C1-4alkyl carboxylic acid, perfluorinated C2-8 alkyl sulfonic acid or perfluorinated C3-8 alkyl carboxylic acid. Methyl triflate (CH3OTf) boils at 100 °C under atmospheric pressure. In a process for the preparation of CH3OTf, the use of acids which boil at a higher temperature than CH3OTf is preferred because it facilitates simpler distillation of CH3OTf from the reaction mixture. The use of triflic acid (HOTf) is preferable because it boils at a higher temperature than CH3OTf and therefore CH3OTf can easily be separated from the reaction mixture by distillation. Similarly, perfluorinated C2-8alkyl sulfonic acids and perfluorinated C3-8alkyl carboxylic acids are useful when preparing CH3OTf because they have sufficient acidity whilst having high boiling points and therefore the reaction proceeds well in these solvents and the CH3OTf can easily be separated from the reaction mixture. Another useful acid medium to use in the process to produce ethylene glycol is H2SO4 / SO3(oleum). This results in the formation of HOSO3CH2CH2OSO3H, which may be hydrolysed to ethylene glycol. Examples of suitable acids to use in the process of producing CH3X or XCH2CH2X or ethylene glycol include CF3SO3H, CH3SO3H, CF3CF2SO3H, CF3CF2CF2SO3H, CF3(CF2)3SO3H, CF3(CF2)4SO3H, CF3(CF2)5SO3H, CF3(CF2)6SO3H, CF3(CF2)7SO3H, CF3CO2H, CF3CF2CO2H, CF3CF2CF2CO2H, CF3(CF2)3CO2H, CF3(CF2)4CO2H, CF3(CF2)5CO2H, CF3(CF2)6CO2H, CF3(CF2)7CO2H, CCl3CO2H, FSO3H, HN(SO2CF3)2, HN(SO2CF2CF3)2or HNO3. Preferably, the acid may be selected from the group consisting of CF3SO3H, CH3SO3H, CF3CF2SO3H, CF3CF2CF2SO3H, CF3CF2CF2CO2H, CCl3CO2H, FSO3H, HN(SO2CF3)2, HN(SO2CF2CF3)2 or HNO3. More preferably, the acid may be selected from the group consisting of CF3SO3H, CH3SO3H, FSO3H or CF3CF2SO3H A particularly preferred acid to use in said process is triflic acid (CF3SO3H). It will be appreciated that the acids disclosed in this section can be used in conjunction with the iodine(III) compounds disclosed above. In the process for the preparation of CH3X or XCH2CH2X, it is preferred for (i) the iodine(III) compound to have the formula I(OSO2R)3 or I[N(SO2R)2]3, wherein R is a C1-8 alkyl group optionally substituted with one or more halogen atoms, and (ii) for the acid to be a perfluorinated C1-8 alkyl sulfonic acid or a perfluorinated C1-8 alkyl carboxylic acid. In the process for making ethylene glycol, it is preferred for (i) the iodine(III) compound to have the formula I(OSO2R)3 or I[N(SO2R)2]3, wherein R is a C1-8 alkyl group optionally substituted with one or more halogen atoms, or for the iodine(III) compound to be I(SO4)(HSO4), and (ii) for the acid to be a perfluorinated C1-8alkyl sulfonic acid or a perfluorinated C1-8alkyl carboxylic acid or for the acid to be H2SO4 / SO3. In the process for the preparation of CH3X or XCH2CH2X or ethylene glycol, as explained in the previous section, the iodine(III) compound may be I(OTf)3or I(NTf2)3, with I(OTf)3being especially preferred. When one of these iodine(III) compounds is used, any of the acids listed above may be used, such as (but not limited to) CF3SO3H, CH3SO3H, CF3CF2SO3H, CF3CF2CF2SO3H, CF3(CF2)3SO3H, CF3(CF2)4SO3H, CF3(CF2)5SO3H, CF3(CF2)6SO3H, CF3(CF2)7SO3H, CF3CO2H, CF3CF2CO2H, CF3CF2CF2CO2H, CF3(CF2)3CO2H, CF3(CF2)4CO2H, CF3(CF2)5CO2H, CF3(CF2)6CO2H, CF3(CF2)7CO2H, CCl3CO2H, FSO3H, HN(SO2CF3)2, HN(SO2CF2CF3)2or HNO3. The acid used in conjunction with I(OTf)3or I(NTf2)3, esepcially I(OTf)3, may be selected from the group consisting of CF3SO3H, CH3SO3H, CF3CF2SO3H, CF3CF2CF2SO3H, CF3CO2H, CF3CF2CO2H, CF3CF2CF2CO2H, CCl3CO2H, FSO3H, HN(SO2CF3)2, HN(SO2CF2CF3)2 or HNO3, or may be selected from the group consisting of CF3SO3H, CH3SO3H, FSO3H, CF3CF2SO3H, CF3CO2H or CF3CF2CO2H. In an especially preferred implementation of the invention, the iodine(III) compound is I(OTf)3 and the acid is CF3SO3H or the iodine(III) compound is I(NTf2)3 and the acid is HNTf2. Even more preferably, the iodine(III) compound is I(OTf)3and the acid is CF3SO3H. As explained above, I(SO4)(HSO4) and I(TFA)3 have shown particularly good results in H2SO4 / SO3 (oleum), and therefore it is also especially preferred for the iodine(III) compound to be I(SO4)(HSO4) or I(TFA)3, wherein the acid is H2SO4 / SO3. As explained above in the context of the process for producing methanol, preferably, the solution of the iodine(III) compound in acid does not contain chloride ions. The volume of acid used is not particularly critical but may be in the range of 10-5000 mL / g relative to the mass of iodine(III) compound, for example in the range of 50-1000 mL / g relative to the mass of iodine(III) compound. Process for the preparation of methyl bisulfate It has unexpectedly been discovered that methyl bisulfate (CH3OSO3H) can be formed by reacting methane with an iodine(III) compound in oleum (H2SO4containing dissolved SO3). It has previously been reported by Periana et al. that elemental iodine dissolved in sulfuric acid containing 2-3% SO3 can catalyse the conversion of methane to methyl bisulfate at elevated temperature and pressure (165-220 °C, 500 psig). In mechanistic studies of this reaction, the iodine(III) species I(HSO4)3was shown not to react with methane (see Chem. Commun., 2002, 2376-2377). However, it has now surprisingly been found that solutions of iodine(III) compounds bearing -OSO2R, -OC(O)R or -N(SO2R)2 ligands in oleum, wherein R is a C1-8 alkyl group optionally substituted with one or more halogen atoms, can convert methane to methyl bisulfate selectively, under mild conditions. The iodine(III) compound I(SO4)(HSO4) has also unexpectedly been found to be able to carry out this reaction selectively under mild conditions. The invention thus provides a process for the preparation of methyl bisulfate comprising: (a) adding methane to a solution of an iodine(III) compound in H2SO4 / SO3in a reaction vessel, wherein the iodine in the iodine(III) compound is bonded to at least one -OSO2R, -OC(O)R or -N(SO2R)2 group, wherein R is a C1-8 alkyl group optionally substituted with one or more halogen atoms, or wherein the iodine(III) compound is I(SO4)(HSO4); and (b) allowing the methane to react with the iodine(III) compound in the reaction mixture formed in step (a). As for the reactions described above, the iodine in the iodine(III) compound is reduced to I2 when the methane is oxidised. NO2can be added to reoxidise the iodine to iodine(III). Therefore, the process may further comprise step (c) of adding NO2to the reaction vessel. This causes the iodine(III) compound to be regenerated and means that only catalytic amounts of the iodine(III) compound are required. The pressure at which NO2is added to the reaction vessel in step (c) is not particularly critical, but it may be added at a pressure of at least about 0.5 bar, preferably in the range from 1 bar to 10 bar. Preferably, the solution is cooled to below 0 °C before NO2 is added and more preferably the solution is cooled to below -50 °C before NO2is added. The process may be operated in a continuous manner by sequentially adding methane and NO2 to the reaction vessel. The process may thus further comprise: (d) adding further methane to the reaction vessel after adding NO2to the reaction vessel; (e) allowing the methane to react with the iodine(III) compound in the reaction mixture formed in step (a); (f) adding further NO2 to the reaction vessel during or after step (b); (g) repeating steps (d) to (f). Preferably, the reaction vessel is degassed before further methane is added in step (d). The reaction vessel may be degassed before NO2is added. Therefore, steps (c) and / or (f) may comprise degassing the reaction vessel before adding NO2. Any of the degassing steps in the process may take place by any standard degassing process, as described above, for example by a freeze-thaw process. The process may comprise adding O2 to regenerate NO2 from the NO that is formed when NO2 reacts with the I2 formed from the reaction of the iodine(III) compound with methane. O2 may be added after each addition of NO2in order to regenerate NO2. For example, O2may be added after step (c) as well as after any previous addition of NO2to the reaction vessel. O2 and NO2 may both be added to the reaction vessel. O2 and NO2 may both be added to the reaction vessel during step (c) and O2and NO2may both be added to the reaction vessel during step (f), but it is preferable to add the O2after step (c) and after step (f). If NO2and O2are both added to the reaction vessel, the reaction vessel is preferably degassed first. This avoids O2 and NO2 mixing with methane, which is preferable from a safety perspective. It is more preferable for O2not to be added to the reaction vessel in which methane is reacted with the iodine(III) compound. Therefore, preferably, NO2 is regenerated by transferring the NO formed in the process to a separate vessel and mixing it with O2 in that vessel to form NO2. Preferably, no catalyst is used to catalyse the reaction of NO with O2 to form NO2. However, optionally, a catalyst may be used and suitable catalysts are well-known to those skilled in the art. The NO2can then be returned to the reaction vessel. As explained above, the reaction of an iodine(III) compound in acid with methane followed by the addition of NO2results in the production of methanol because some water is formed in situ when I2is oxidised back to an I(III) compound in the presence of acid (see reaction scheme above), which can hydrolyse some of the methyl ester that is initially formed to methanol and results in the establishment of an equilibrium between the methyl ester and methanol. Oleum is a particularly good acid in which to perform this reaction and this results in the formation of methyl bisulfate and some methanol. Methyl bisulfate is itself a useful chemical, as explained above, and therefore methyl bisulfate may be separated from the reaction mixture, for example by distillation under reduced pressure. As explained above, Periana et al have demonstrated that elemental iodine dissolved in sulfuric acid containing 2-3% SO3can catalyse the conversion of methane to methyl bisulfate at elevated temperature and pressure (165-220 °C, 500 psig). The inventors of the present invention have confirmed that I2 in H2SO4 containing 20% SO3 (significantly more than used by Periana et al) does not react with methane under milder conditions, when methane is added at a pressure of 1 bar and the reaction mixture is heated to 100 °C for 18 hours. However, it has surprisingly been found that when NO2is added to a solution of I2in H2SO4(20% SO3), methyl bisulfate is formed, even under these mild conditions. The addition of NO2 thus enables the production of methyl bisulfate from methane and elemental iodine under mild conditions and thus results in an improved process. Accordingly, the present invention provides a process for the preparation of methyl bisulfate comprising: (a) adding I2 to H2SO4 / SO3 in a reaction vessel; (b) adding NO2 to the reaction vessel; (c) adding methane to the reaction vessel. Preferably, NO2 is removed from the reaction vessel after step (b), before methane is added in step (c). This may be achieved by degassing the reaction vessel, for instance by using a freeze-thaw process as described above. The H2SO4 / SO3in which the iodine(III) compound or the I2is dissolved is preferably H2SO4that contains dissolved SO3 in an amount of 1-65% w / w, more preferably 10-65% w / w and even more preferably 10-40% w / w. As explained above, the process of the present invention allows methyl bisulfate to be produced from methane at much lower temperature and pressure than known methods. The same temperature and pressure may be used as described above for the conversion of methane to methanol. Therefore, the methane may be added to the rection vessel at a pressure as low as 0.5 bar. However, in an industrial context it may be preferred to use a much higher pressure in order to achieve a faster and more complete reaction. There is no particular maximum on the pressure that may be used, and this will largely be dictated by the nature of the reaction vessel used. Therefore, the methane may be added to the reaction vessel at any pressure of about 0.5 bar or above, preferably in the range from about 0.5 bar to about 200 bar or about 0.5 bar to about 100 bar. More preferably, the methane is added to the reaction vessel at a pressure in the range from about 1 bar to about 100 bar, even more preferably in the range from about 1 bar to about 50 bar. A pressure of about 1 bar to about 50 bar may be particularly suitable for industrial applications. The methane can be allowed to react with the iodine(III) compound at room temperature, i.e. at a temperature in the range from about 20 °C to about 30 °C. The reaction may be allowed to occur at a temperature as low as about 10°C. However, the reaction proceeds faster at higher temperatures. Thus, in step (b), a temperature in the range from about 10°C to about 200°C may be used, but a temperature in the range from about 20°C to about 150°C is more preferable and a temperature in the range from about 50°C to about 125°C is even more preferable. It will be appreciated that the pressures and temperatures referred to above apply in the context of the same process and not to separate embodiments. Thus in the process of the invention, methane may be added to the reaction vessel at a pressure in the range from about 1 bar to about 100 bar, even more preferably in the range from about 1 bar to about 50 bar and the reaction vessel may then be heated to a temperature in the range from about 10°C to about 200°C, preferably in the range from about 20°C to about 150°C and more preferably in the range from about 50°C to about 125°C. The process may therefore involve adding methane to the reaction vessel at a pressure in the range from about 1 bar to about 100 bar and then heating the reaction vessel to a temperature in the range from about 20°C to about 150°C. A particularly preferred implementation of the process is for the methane to be added at a pressure in the range from about 1 bar to about 50 bar and for the reaction vessel to be heated to a temperature the range from about 50°C to about 125°C. The process of producing methyl bisulfate involves adding methane to an iodine(III) compound in acid in a reaction vessel. The iodine in the iodine(III) compound is bonded to at least one -OSO2R, -OC(O)R or - N(SO2R)2 group, wherein R is a C1-8 alkyl group optionally substituted with one or more halogen atoms, or the iodine(III) compound may be I(SO4)(HSO4). It is not vital for all groups attached to iodine in the iodine(III) compound to be -OSO2R, -OC(O)R or - N(SO2R)2 groups. The iodine in the iodine(III) compound may, for example, be bonded to one or more aryl (Ar) groups. Thus, the iodine(III) compound may, for example, be of the formula ArIZ2 or Ar2IZ, where Z is - OSO2R, OC(O)R or N(SO2R)2. Ar is preferably a phenyl group, more preferably a substituted phenyl group, wherein the substituents are preferably nitro or halo groups. Especially preferred Ar groups are C6F5or p- NO2C6H4, i.e. the iodine(III) compound may be of the formula (C6F5)IZ2, (C6F5)2IZ, (p-NO2C6H4)IZ2 or (p NO2C6H4)2IZ, where Z is as defined above. However, the iodine(III) compound is very preferably homoleptic, meaning that all three substituents on the iodine atom are the same. In other words, the iodine(III) compound very preferably has the formula I(OSO2R)3, I(OC(O)R)3 or I[N(SO2R)2]3. I(SO4)(HSO4) is another preferred iodine(III) compound. R is a C1-8alkyl group optionally substituted with one or more halogen atoms. Preferred R groups are perfluorinated C1-8 alkyl groups or C1-4 alkyl groups substituted with at least one halogen atom. More preferred R groups have the formula CnF2n+1 or CnCl2n+1, wherein n is 1-4, even more preferably wherein n is 1 or 2. It is especially preferred that R is CF3. The iodine(III) compound may have the formula I(OSO2R)3, I(OC(O)R)3 or I[N(SO2R)2]3, wherein R is a perfluorinated C1-8 alkyl group or a C1-4 alkyl group substituted with at least one halogen atom. The iodine(III) compound may have the formula I(OSO2R)3, I(OC(O)R)3or I[N(SO2R)2]3, wherein R has the formula CnF2n+1CnF2n+1or CnCl2n+1, wherein n is 1-4, preferably wherein n is 1 or 2. R groups of the formula CnF2n+1are more preferred than R groups of the formula CnCl2n+1, so more preferably, R has the formula CnF2n+1, wherein n is 1-4, even more preferably wherein n is 1 or 2. The most preferred iodine(III) compounds for use in the process of producing methyl bisulfate are I(OTf)3, I(CF3CO2)3, I(SO4)(HSO4) and I(NTf2)3, especially I(OTf)3 and I(CF3CO2)3. The process may thus comprise: (a) adding methane to a solution of I(OTf)3or I(CF3CO2)3in H2SO4 / SO3in a reaction vessel, preferably at a pressure in the range from about 1 bar to about 50 bar; (b) allowing the methane to react with the reaction mixture formed in step (a), preferably in the range from about 20°C to about 150°C; and (c) preferably, adding NO2to the reaction vessel. This process involving I(OTf)3 or I(CF3CO2)3 may further incorporate any of the other preferred features disclosed above. Process for the oxidation of higher alkanes The above disclosure focuses on the activation of methane and ethane, which are the hardest alkanes to oxidise and which are of the greatest commercial interest. However, the chemistry described herein may also be used to oxidise higher alkanes that have at least 3 carbon atoms. Consequently, the invention provides a process for the oxidation of an alkane that contains at least 3 carbon atoms, preferably 3-10 carbon atoms and more preferably 3-6 carbon atoms, wherein the process comprises: (a) adding said alkane to a solution of an iodine(III) compound in acid in a reaction vessel, wherein the iodine in the iodine(III) compound is bonded to at least one -OSO2R, -OC(O)R or -N(SO2R)2group, wherein R is a C1-8alkyl group optionally substituted with one or more halogen atoms, or wherein the iodine(III) compound is I(SO4)(HSO4), wherein the acid is an acid that has a pKa of less than 3 on the aqueous pKa scale or the acid is an acid that has a Hammett acidity function (H0) of less than -2; (b) allowing the alkane to react with the iodine(III) compound in the reaction mixture formed in step (a). Most preferably, the alkane is propane and the process yields propylene glycol. In order to make the process catalytic, the process may further comprise adding NO2to the reaction vessel. The process may be performed in a continuous manner in which the process further comprises: (a) adding further of said alkane to the reaction vessel after adding NO2to the reaction vessel in step (c); (b) allowing said alkane to react with the iodine(III) compound in the reaction mixture formed in step (d); (c) adding further NO2to the reaction vessel during or after step (e); and (d) repeating steps (d) to (f). O2 may be used to regenerate NO2, such that O2 acts as the terminal oxidant in the process. O2 may be added in the manner described above in the context of the process for making methanol. The alkane may be a straight chain, branched chain or cyclic alkane. The present invention also provides a process for the oxidation of an alkane that contains at least 3 carbon atoms, preferably 3-10 carbon atoms and more preferably 3-6 carbon atoms, wherein the process comprises: (a) adding NO2 to a solution of I2 in acid in a reaction vessel, wherein the acid is H2SO4 / SO3 or wherein the acid is an acid having the formula RSO3H, RCO2H or HN(SO2R)2, wherein R is a C1-8 alkyl group optionally substituted with one or more halogen atoms, wherein said acid is an acid that has a pKa of less than 3 on the aqueous scale or the acid is an acid that has a Hammett acidity function (H0) of less than -2; (b) adding said alkane to the reaction vessel; (c) allowing the alkane to react with the reaction mixture formed in step (a). The preferences for the reaction conditions, the nature of the iodine(III) compound and the acid that are described above in the context of the process for making methanol apply equally to the process for the oxidation of an alkane that comprises at least 3 carbon atoms. Therefore, in step (a), the alkane may be added to the reaction vessel at any pressure of about 0.5 bar or above, preferably in the range from about 0.5 bar to about 200 bar or about 0.5 bar to about 100 bar. More preferably, the alkane is added to the reaction vessel at a pressure in the range from about 1 bar to about 100 bar, even more preferably in the range from about 1 bar to about 50 bar. A pressure in the range from about 1 bar to about 50 bar may beparticularly suitable for industrial applications. In step (b) of the process, the alkane can be allowed to react with the iodine(III) compound at room temperature, i.e. at a temperature in the range from about 20 °C to about 30 °C. The reaction may take place at a temperature as low as about 10°C. However, the reaction proceeds faster at higher temperatures. Thus, in step (b), a temperature in the range from about 10°C to about 200°C may be used, but a temperature in the range from about 20°C to about 150°C is more preferable and a temperature in the range from about 50°C to about 150°C is even more preferable. The temperatures described above may be used in conjunction with the alkane being added at the pressures described above. Except in the case where the iodine(III) compound I(SO4)(HSO4), the iodine(III) compound is very preferably homoleptic, meaning that all three substituents on the iodine atom are the same. In other words, the iodine(III) compound very preferably has the formula I(OSO2R)3, I(OC(O)R)3 or I[N(SO2R)2]3, more preferably I(OSO2R)3 or I[N(SO2R)2]3. R is a C1-8alkyl group optionally substituted with one or more halogen atoms. Preferred R groups are perfluorinated C1-8 alkyl groups or C1-4 alkyl groups substituted with at least one halogen atom. More preferred R groups have the formula CnF2n+1 or CnCl2n+1, wherein n is 1-4, even more preferably wherein n is 1 or 2. R groups of the formula CnF2n+1are more preferred than R groups of the formula CnCl2n+1, so more preferably, R has the formula CnF2n+1, wherein n is 1-4, even more preferably wherein n is 1 or 2. It is especially preferred that R is CF3. The iodine(III) compound may have the formula I(OSO2R)3or I[N(SO2R)2]3, wherein R is a perfluorinated C1-8alkyl group or a C1-4alkyl group substituted with at least one halogen atom. The iodine(III) compound may have the formula I(OSO2R)3 or I[N(SO2R)2]3, wherein R has the formula CnF2n+1 or CnCl2n+1, wherein n is 1-4, preferably wherein n is 1 or 2. The iodine(III) compound I(SO4)(HSO4) has been found to be highly effective for the oxidation of methane. Therefore, a preferred iodine(III) compound is I(SO4)(HSO4). Since I(SO4)(HSO4) may be prepared in situ from I(CF3CO2)3 (also known as I(TFA)3) and H2SO4 / SO3 (oleum), and the resultant solution shows excellent activation of methane under mild conditions (i.e. a pressure of about 1 bar and a temperature of about 65oC), in another preferred implementation of the invention, the iodine(III) compound is I(CF3CO2)3and the acid is H2SO4 / SO3. The most preferred iodine(III) compounds for use in the process of oxidising an alkane having 3-10 carbon atoms, most preferably propane, are I(OTf)3, I(SO4)(HSO4) and I(NTf2)3, especially I(OTf)3and I(SO4)(HSO4). Also preferred in this context, especially in the oxidation of propane, is I(TFA)3 in H2SO4 / SO3 as the acid. In these processes, the acid is an acid that has a pKa of less than 3 on the aqueous pKa scale or is an acid that has a Hammett acidity function (H0) of less than -2. Preferably, the acid is an acid that has a pKa of less than 3 on the aqueous scale. Preferably, the pKa of the acid is less than 1 on the aqueous pKa scale, more preferably less than 0 and most preferably less -1 on the aqueous pKa scale. The acid may be an acid that has a Hammett acidity function (H0) of less than -2. Preferably, the Hammett acidity function (H0) is less than -6, more preferably less than -10. As those skilled in the art will understand, many acids will have a pKa of less than 3 on the aqueous scale and a Hammett acidity function (H0) of less than -2. However, there may be some acids that only satisfy one or other of these requirements, but not both, and such acids are within the scope of the present invention. Preferably, the acid is the conjugate acid of the -OSO2R, -OC(O)R or -N(SO2R)2 group that is attached to the iodine atom in the iodine(III) compound. Alternatively, the acid may be a weaker acid than the conjugate acid of the -OSO2R, -OC(O)R or -N(SO2R)2group that is attached to the iodine atom in the iodine(III) compound, providing the acid is an acid that has a pKa on the aqueous scale of less than 3, preferably less than 1, or is an acid that has a Hammett acidity function (H0) of less than -2. The acid may be a carboxylic acid or a sulfonic acid or HNO3. Sulfonic acids include H2SO4, which may contain dissolved SO3 (i.e. oleum). The carboxylic acid or sulfonic acid may contain a halogenated alkyl or aryl group, preferably wherein the halogen atoms are fluorine or chlorine atoms. More preferably, the acid is a perfluorinated C1-8 alkyl sulfonic acid or perfluorinated C1-8 alkyl carboxylic acid, such as a perfluorinated C1-4 alkyl sulfonic acid or perfluorinated C1-4alkyl carboxylic acid. Another useful acid medium to use in the reaction is H2SO4 / SO3 (oleum). I(SO4)(HSO4) has been found to be an especially active catalyst, and it may be formed from I(TFA)3in H2SO4 / SO3. The iodine(III) compound may be I(SO4)(HSO4) or I(TFA)3, wherein the acid is H2SO4 / SO3. Examples of suitable acids to use in the process of oxidising an alkane that contains at least 3 carbon atoms include CF3SO3H, CH3SO3H, CF3CF2SO3H, CF3CF2CF2SO3H, CF3(CF2)3SO3H, CF3(CF2)4SO3H, CF3(CF2)5SO3H, CF3(CF2)6SO3H, CF3(CF2)7SO3H, CF3CO2H, CF3CF2CO2H, CF3CF2CF2CO2H, CF3(CF2)3CO2H, CF3(CF2)4CO2H, CF3(CF2)5CO2H, CF3(CF2)6CO2H, CF3(CF2)7CO2H, CCl3CO2H, HN(SO2CF3)2, HN(SO2CF2CF3)2, FSO3H, H2SO4 / SO3 or HNO3. Preferably, the acid may be selected from the group consisting of CF3SO3H, CH3SO3H, CF3CF2SO3H, CF3CF2CF2SO3H, CF3CO2H, CF3CF2CO2H, CF3CF2CF2CO2H, CCl3CO2H, HN(SO2CF3)2, HN(SO2CF2CF3)2, FSO3H, H2SO4 / SO3 or HNO3. More preferably, the acid may be selected from the group consisting of CF3SO3H, CH3SO3H, CF3CF2SO3H, CF3CO2H, CF3CF2CO2H, FSO3H or H2SO4 / SO3, even more preferably CF3SO3H or H2SO4 / SO3. A particularly preferred acid to use in the process is triflic acid (CF3SO3H). In preferred implementations of the process for oxidation of an alkane having 3-10 carbon atoms, the iodine(III) compound is I(OTf)3 and the acid is HOTf, or the iodine(III) compound is I(TFA)3 or I(SO4)(HSO4) and the acid is H2SO4 / SO3. EXAMPLES The invention is illustrated by the following examples. These examples are not limiting on the scope of the invention, which is defined by the appended claims. Example 1: Stoichiometric methane activation using I(OTf)3 in HOTf I(OTf)3(50 mg) was added to a J. Youngs NMR tube. HOTf (0.6 mL) was then added to this to make a yellow solution. A 0.01 M 1,3,5-trimethoxybenzene in DMSO-d6 capillary insert was added to the NMR tube for use as a concentration reference and deuterium lock. Typically, an NMR measurement was carried out at this point to determine if there were any contamination. The N2in the NMR tube was then removed by freeze-pump-thawing the solution three times. CH4(1 Bar) was then added to the NMR tube. An NMR measurement was typically carried out at this point to determine successful CH4 addition. The solution was then heated at the desired temperature. The colour of the solution typically displayed the following colours in order: yellow, turquoise, green, brown. The end point is determined by the visible formation of I2. An NMR measurement was then taken to determine CH4activation.1H NMR (400 MHz, DMSO) δ 9.79 (s, HOTf), 6.11 (s, (1,3,5-TMB)), 4.03 (s, CH3OTf, 3.73 (s, (1,3,5-TMB)), - 0.09 (s, CH4). Figure 1 depicts the % conversion of CH4using I(OTf)3and HOTf as a function of temperature in an NMR tube with no stirring, wherein the CH4 was added at 1 bar. It can be seen that the reaction progresses rapidly at temperatures below 100 °C when methane is added at 1 bar. This is a remarkable result given that previous systems for the oxidation of methane have required the use of much higher temperatures and pressures to achieve appreciable methane conversion. Example 2: Stoichiometric ethane activation using I(OTf)3in HOTf Ethane was generated in-situ from the hydrolysis of ethyl magnesium chloride. Ethyl magnesium chloride (1 M, in THF, 20 mL) was added to an ampoule which was connected to a silicon oil bubbler, which itself was connected to a two valve, three way glass manifold with a balloon attached, and this was then cooled to 0 °C. Wet ethanol was added to the solution of EtMgCl which produced ethane (the production of which was observed in the bubbler), which was collected in a balloon and then the balloon sealed shut with using the J. Youngs glass adaptor. The ampoule was then disconnected from the three-way manifold and the valve then connected to a Schlenk line by one arm, and to the other an NMR tube containing I(OTf)3 (50 mg) in HOTf (0.6 mL) with a 0.01 M 1,3,5-trimethoxybenzene in DMSO-d6 capillary insert was added. The NMR tube was then degassed by freeze-pump-thawing three times and left evacuated. The three-way valve manifold was also left under vacuum and then sealed from the Schlenk line. The balloon valve was opened allowing the ethane to fill the manifold, and then the evacuated NMR tube was opened, allowing ethane to enter. The NMR tube was then sealed. Reactivity was observed almost immediately, with the solutions colour changing from yellow to blue / green at the interface of the gas and liquid. Within 5 minutes at room temperature, the entire solution was turquoise. An NMR measurement was taken. The solution was then left at room temperature for 18 h. Another NMR measurement was taken.1H NMR (400 MHz, DMSO_weak) δ 10.11 (s, (HOTf)), 6.09 (s, (1,3,5-TMB)), 4.60 (s, (EG(OTf)2)), 3.70 (s, (1,3,5-TMB)). EG(OTf)2refers to the compound of the formula (OTf)CH2CH2(OTf). Example 3: Solid state reactivity of I(OTf)3 with CH4 I(OTf)3(50 mg) was placed into a J. Youngs NMR tube. The N2was removed in vacuo and then CH4(1 Bar) was added. The NMR tube was then heated at 100 °C. After 5 minutes the white solid had turned into a green oily solid. The NMR tube was heated for 24 h at 100 °C which afforded a brown oily liquid with sublimed I2 on the walls of the NMR tube. HOTf (0.6 mL) was added to the NMR tube to afford a brown solution. A 0.01 M 1,3,5-trimethoxybenzene in DMSO-d6 capillary insert was added to the NMR tube for use as a concentration reference and deuterium lock. An NMR measurement was then taken to determine CH4activation. The yield of MeOTf was 10.5% with respect to CH4.1H NMR (400 MHz, DMSO_weak) δ 10.06 (s, HOTf), 6.09(s, 1,3,5-TMB), 3.93 (s, MeOTf), 3.70 (s, 1,3,5- TMB), -0.21 (s, CH4). Example 4: Reaction of CH4 with I(OTf)3 in H2SO4 (20% SO3) I(OTf)3(30 mg) was placed inside an NMR tube in the glovebox along with a 0.01 M 1,3,5-trimethoxybenzene in DMSO-d6 capillary insert for use as a concentration reference and deuterium lock. Under a flush of nitrogen, H2SO4 (20% SO3) (0.6 mL) was added to the NMR tube to afford a pale-yellow solution. An NMR measurement was then taken. The N2was removed from the NMR tube by one freeze-pump-thaw (only one was performed to avoid loss of SO3) and CH4(1 bar) was added. An NMR measurement was taken again to determine CH4 addition success. The solution was then heated at 100 °C. After 5 minutes the solution had started to change colour at the gas / liquid interface from pale yellow to turquoise. After a further 10 minutes the entire solution was turquoise. The solution was heated at 100 °C for 40 h to afford a green / brown solution. An NMR measurement was taken.1H NMR (400 MHz, DMSO_weak) δ 10.16 (s, H2SO4), 6.09 (s, 1,3,5-TMB), 3.70 (s, 1,3,5-TMB), 3.63 (s, CH3OSO3H). Example 5: Catalytic CH4 oxidation using I(OTf)3 + NO2 + CH4 in HOTf I(OTf)3(50 mg) was added to a J. Youngs ampoule. HOTf (5 mL) was added to this to give a yellow solution. The solution was then degassed and CH4(1 Bar) was added. (A) The solution was allowed to stir at 100 °C until I2 was observed (brown solution colour). NO2 (0.0313 g) was then added at -78 °C, and allowed to thaw to give a turquoise solution, then degassed again and finally CH4 (1 bar) was added. Again, this was heated to 100 °C and allowed to react. The steps from A were then repeated 3 more times. NO2was added again to homogenise the solution. A 0.6 mL aliquot of this reaction was then taken and added to an NMR tube.1H-NMR showed that 4.25 eq. MeOTf were produced. Example 6: Catalytic CH4oxidation using I2+ NO2+ CH4in HOTf I2 (10 mg) was added to a J. Youngs ampoule. HOTf (5 mL) was added to this to give a brown suspension. The solution was then degassed and NO2 (0.0313 g) was added to give a turquoise solution. The solution was then degassed again and CH4(1 Bar) was added. (A) The solution was allowed to stir at 100 °C until I2was observed (brown solution colour). NO2(0.0313 g) was then added at -78 °C, and allowed to thaw to give a turquoise solution, then degassed again and finally CH4 (1 bar) was added. Again, this was heated to 100 °C and allowed to react. The steps from A were then repeated 3 more times. NO2 was added again to homogenise the solution. A 0.6 mL aliquot of this reaction was then taken and added to an NMR tube.1H-NMR showed that 2.76 eq. MeOTf were produced. NMR spectra of the reaction mixture and reference solutions provided evidence for the formation of methanol, as explained below: When pure MeOTf is added to HOTf, it exhibits a diagnostic proton resonance at 3.93 ppm in the1H NMR spectrum (see Figure 2). When MeOH is added to HOTf, it produces MeOTf, but the relative shift in the1H NMR spectrum (3.91 ppm) of this is lower than that observed for pure MeOTf in HOTf (3.93 ppm). The1H NMR spectrum of a low concentration of MeOH in HOTf is shown in Figure 3. As the concentration of MeOH in HOTf increases, this resonance shifts even further downfield, to 3.83 ppm. The1H NMR spectrum of a high concentration of MeOH in HOTf is shown in Figure 4. This indicates that when methanol is added to HOTf, it reacts to form methyl triflate (MeOTf) and water in a reversible reaction. This exists as an equilibrium, which presents as a single resonance in the1H NMR spectrum, due to fast exchange on the NMR timescale. The relative shift of this resonance can determine the amount of methanol to methyl triflate in a solution of HOTf containing both species. In the catalytic oxidation of methane using I2 and NO2 in HOTf described above, the1H NMR resonance for the product is found at 3.88 ppm (see the NMR spectrum in Figure 5), demonstrating that methanol must be present in the solution to shift this resonance upfield from that of pure MeOTf in HOTf (3.93 ppm). This is produced from in-situ hydrolysis of the MeOTf produced during the methane oxidation, with the water provided for this coming from the oxidation of I2 by NO2, which make this reaction catalytic as explained above. Example 7: Catalytic CH4oxidation using I(OTf)3+ NO2+ CH4in oleum I(OTf)3 (50 mg) was added to a J. Youngs ampoule. H2SO4 (20% SO3) (5 mL) was added to this to give a yellow solution. The solution was then degassed and CH4 (1 Bar) was added. (A) The solution was allowed to stir at 100 °C until I2was observed (brown solution colour). NO2(0.0313 g) was then added at -78 °C, and allowed to thaw to give a turquoise solution, then degassed again and finally CH4(1 bar) was added. Again, this was heated to 100 °C and allowed to react. The steps from A were then repeated 3 more times. NO2 was added again to homogenise the solution. A 0.6 mL aliquot of this reaction was then taken and added to an NMR tube.1H-NMR showed that 9.58 eq. MeOSO3H were produced. Example 8: Stoichiometric activation of methane using I2 in H2SO4 (20% SO3) with NO2 I2(10 mg) was added to a J.Young’s NMR tube. H2SO4(20% SO3) (0.6 mL) was added to this along with a 0.01 M 1,3,5-trimethoxybenzene in DMSO-d6 capillary insert for use as a concentration reference and deuterium lock. This gave a green / brown solution. The N2 was removed from the NMR tube by one freeze-pump-thaw (only one was performed to avoid loss of SO3) and NO2 (0.0313 g) was added to the NMR tube. This was then allowed to heat to room temperature and a blue solution was immediately produced. The NO and excess NO2was then removed from the NMR tube by one freeze-pump-thaw (only one was performed to avoid loss of SO3) and CH4 (1 bar) was added. An NMR measurement was taken. This was then heated at 100 °C for 18 h which produced a green brown solution. An NMR measurement was taken.1H NMR (400 MHz, DMSO_weak) δ 10.21 (HOTf), 6.09 (1,3,5-TMB insert), 3.71 (1,3,5-TMB insert), 3.67 (MeOSO3H). Example 9: Synthesis of I(SO4)(HSO4) I(SO4)(HSO4) was synthesized according to the following reaction: I(TFA)3 (100 mg) was added to a J. Youngs ampoule. H2SO4 (20% SO3, 3 mL) was added to this to produce a yellow solution. This was stirred at room temperature for 2 h. After this time the TFAH was removed in vacuo, at which point a white solid started to precipitate. N2was added to the solution, and the solution warmed slightly to redissolve all of the solid. The ampoule was then placed in a beaker of toluene and transferred to the 4 °C fridge. Crystals suitable for XRD were grown as colourless blocks. The crystal structure of the compound obtained by XRD is shown in Figure 6. As can be seen in Figure 6, the crystal structure is polymeric in nature, with bridging SO42-groups binding three iodine centres. Also coordinated to each iodine centre is a terminal HSO4- group. This conclusion that these bridging sulphonates are doubly deprotonated, comes from the fact that in order to charge balance with the I(III), they have to have a formal -2 charge. Also, the free, uncoordinated oxygen (O6) has not got a long enough S-O bond to have an OH group attached to the sulphur centre (S2-O6 = 1.419(4), typical of an S=O bond; S-OH bonds typically 1.52- 1.54 Å), whereas it can be seen in the terminal HSO4- that there is a clear and typical S-OH bond length (S1-O2 = 1.525(4)). The structure is reminiscent of that found for the thorium compound Th(SO4)(HSO4)2(see U. Betke and M. S. Wickleder, Eur. J. Inorg. Chem., 2012, 2012, 306–317). Because each bridging sulphonate has a -2 charge, and each is bound to three iodine centres, the formal charge if split evenly is therefore -2 / 3 for each iodine; each iodine is bound to three of these, accounting for a charge of 2, and finally the terminal HSO4- makes up the final necessary charge to show that the iodine is in the +3 oxidation state. Example 10: in situ reactivity of CH4 with I(SO4)(HSO4) I(TFA)3(30 mg) was added to 2 J. Youngs NMR tubes. H2SO4(20% SO3, 0.6 mL) was added to each. After leaving at r.t. for 1 h, the TFAH was evacuated from each reaction and then CH4(1 bar) was added to one reaction, and N2 was added to the other. Both were heated at 100 °C for 18 h. NMR showed that CH4 activation is observed, producing methyl bisulfate. This is a remarkable result given that only 1 bar of CH4was used at a temperature of just 100 °C. The1H NMR spectrum of the reaction mixture recorded before addition of methane (top) and after the reaction described above (bottom) is shown in Figure 7. Example 11: Gas phase infrared (IR) data of the headspace of a reaction between I2in trifuloromethanesulphonic acid, and NO2I2 (17.5 mg) was added to trifluoromethanesulphonic acid (2 mL) in an ampoule. The suspension was then frozen and NO2(5 mL) was added. Once the NO2was frozen, the ampoule was evacuated and sealed. It was then allowed to warm to room temperature where the solution turned from light pink to a deep turquoise solution. The headspace of the reaction was then vacuum transferred to an evacuated 10 cm gas phase IR cell (KBr windows). An IR spectrum was measured, which displayed characteristic absorbances associated with NO gas (1959 cm-1, 1928 cm-1– see R. E. Nightingale, A. R. Downie, D. L. Rotenberg, B. J. Crawford and R. A. J. Ogg, J. Phys. Chem., 1954, 58, 1047–1050). This IR spectrum is shown in Figure 8. Absorbances associated with NO2 (1750 cm-1(N2O4), 1600 cm-1(NO2), 1250 cm-1(N2O4), 750 cm-1(N2O4)) (see Figure 9) are not present in the spectrum (see R. E. Nightingale, A. R. Downie, D. L. Rotenberg, B. J. Crawford and R. A. J. Ogg, J. Phys. Chem., 1954, 58, 1047–1050). The absorbances below 1500 cm-1are associated with trifluoromethanesulphonic acid vapour. The NO2used for these reactions does not contain any NO gas, so this must be a product of the reaction between the NO2and I2in trifluoromethanesulphonic acid. This result demonstrates that NO is formed in the reaction, which can be subsequently re-oxidised by O2 and reused in the catalytic cycle.

[0002] EMBODIMENTS OF THE INVENTION A process for producing methanol comprising: (a) adding methane to a solution of an iodine(III) compound in acid in a reaction vessel, wherein the iodine in the iodine(III) compound is bonded to at least one -OSO2R, -OC(O)R or -N(SO2R)2group, wherein R is a C1-8 alkyl group optionally substituted with one or more halogen atoms, or wherein the iodine(III) compound is I(SO4)(HSO4), wherein the acid is an acid that has a pKa of less than 3 on the aqueous pKa scale or the acid is an acid that has a Hammett acidity function (H0) of less than -2; (b) allowing the methane to react with the iodine(III) compound in the reaction mixture formed in step (a); and (c) adding NO2 to the reaction vessel. The process of embodiment 1, further comprising adding O2to regenerate NO2. The process of embodiment 1 or embodiment 2, wherein NO2is added to the reaction vessel after step (b), after the formation of I2. The process of any one of embodiments 2-3, wherein O2and NO2are both added to the reaction vessel in step (c) before any further methane is added to the reaction vessel. The process of any preceding embodiment, wherein step (c) comprises degassing the reaction vessel before the NO2 is added. The process of any preceding embodiment, further comprising: (d) adding further methane to the reaction vessel after adding NO2to the reaction vessel in step (c); (e) allowing the methane to react with the iodine(III) compound in the reaction mixture formed in step (d); (f) adding further NO2to the reaction vessel during or after step (e); and (g) repeating steps (d) to (f). The process of any preceding embodiment, wherein the solution is cooled to below 0°C before NO2 is added in step (c) and step (f). The process of embodiment 6 or embodiment 7, wherein O2and NO2are added to the reaction vessel in step (f). The process of any one of embodiments 6-8, wherein step (d) further comprises degassing the reaction vessel before the further methane is added. The process of any preceding embodiment, further comprising performing distillation to separate methanol from the reaction mixture. The process of any preceding embodiment, wherein the step of allowing the methane to react with the iodine(III) compound is conducted at a temperature in the range from about 10 °C and about 200 °C, preferably in the range from about 20 °C to about 150 °C, more preferably in the range from about 50 °C to about 125 °C. A process for producing methanol comprising: (a) adding NO2 to a solution of I2 in acid in a reaction vessel, wherein the acid is an acid having the formula RSO3H, RCO2H or HN(SO2R)2, wherein R is a C1-8 alkyl group optionally substituted with one or more halogen atoms, wherein the acid is an acid that has a pKa of less than 3 on the aqueous scale or the acid is an acid that has a Hammett acidity function (H0) of less than -2; (b) adding methane to the reaction vessel; and (c) allowing the methane to react with the reaction mixture formed in step (a). The process of embodiment 12, further comprising: (d) adding further NO2to the reaction vessel after step (c) or adding O2to regenerate NO2; (e) adding further methane to the reaction vessel during or after step (d); (f) allowing the methane to react with the reaction mixture formed in step (e); and (g) repeating steps (d) to (f). The process of embodiment 12 or 13, comprising degassing the solution after step (a), before adding the methane in step (b). The process of 13 or embodiment 14, comprising degassing the solution after step (c), before adding the further NO2 in step (d). The process of any one of embodiments 12-15, wherein the temperature in step (c) and step (f) is in the range from about 10 °C and about 200 °C, preferably in the range from about 20 °C to about 150 °C, more preferably in the range from about 50 °C to about 125 °C. The process of any preceding embodiment, wherein methane is added to the reaction vessel at a pressure in the range from about 0.5 bar to about 100 bar. The process of any preceding embodiment, further comprising adding water to the reaction mixture after adding methane to the reaction vessel and allowing it to react. A process for the preparation of a compound of the formula CH3X or XCH2CH2X comprising reacting methane or ethane with an iodine(III) compound, wherein X is -OSO2R or -N(SO2R)2 and wherein the iodine in the iodine(III) compound is bonded to at least one X group, wherein R is a C1-8 alkyl group optionally substituted with one or more halogen atoms. The process of embodiment 19, wherein methane or ethane gas is passed over the iodine(III) compound in the solid state. The process of embodiment 20, wherein the reaction is conducted at a temperature in the range from about 50 °C to about 150 °C, preferably about 75 °C to about 125 °C. The process of embodiment 20 or embodiment 21, wherein the methane or ethane is added to the reaction vessel at a pressure in the range from about 0.5 bar to about 100 bar. The process of any one of embodiments 20-22, wherein the iodine(III) compound is incorporated into a catalyst support material. The process of any one of embodiments 20-23, wherein NO2 is passed over the iodine compound that remains after methane or ethane gas has been passed over the iodine(III) compound, in order to regenerate the iodine(III) compound. The process of embodiment 19, wherein the methane or ethane is added to a solution of the iodine(III) compound in acid in a reaction vessel, wherein the acid is an acid that has a pKa of less than 3 on the aqueous scale, providing that the acid is not H2SO4 / SO3. The process of embodiment 25, further comprising adding NO2to the reaction vessel, preferably wherein NO2 is added to the reaction vessel after the formation of I2. The process of embodiment 26, further comprising adding O2 to regenerate NO2. The process of any one of embodiments 26-27, comprising: (a) adding further methane or ethane to the reaction vessel after adding NO2 to the reaction vessel; (b) allowing the methane or ethane to react with the iodine(III) compound in the reaction mixture formed in step (a); (c) adding further NO2to the reaction vessel during or after step (b); and (d) repeating steps (a) to (c). The process of embodiment 28, wherein O2 and NO2 are added to the reaction vessel in step (c). The process of embodiment 28 or embodiment 29, wherein step (a) comprises degassing the reaction vessel before the further methane or ethane is added. The process of any one of embodiments 25-30, wherein the solution of the iodine(III) compound in acid is formed by mixing I2 with an acid and adding NO2 to the reaction vessel, wherein the acid has the formula HX. The process of any one of embodiments 24-31, wherein the methane or ethane is allowed to react with the iodine(III) compound at a temperature in the range from about 10 °C and about 200 °C, preferably in the range from about 10 °C to about 150 °C, more preferably in the range from about 50 °C to about 125 °C. The process of any one of embodiments 25-32, wherein the methane or ethane is added to the reaction vessel at a pressure in the range of about 0.5 bar to about 100 bar. The process of any one of embodiments 25-33, further comprising hydrolysing the XCH2CH2X to ethylene glycol or hydrolysing the CH3X to methanol. The process of any one of embodiments 26-33, wherein methanol or ethylene glycol is formed in the reaction mixture and is separated from the reaction mixture, preferably by distillation. A process for the preparation of ethylene glycol comprising adding ethane to a solution of an iodine(III) compound in acid in a reaction vessel, wherein the acid is an acid that has a pKa of less than 3 on the aqueous scale or the acid is an acid that has a Hammett acidity function (H0) of less than -2, wherein the iodine in the iodine(III) compound is bonded to at least one X group and wherein X is -OSO2R or -N(SO2R)2, wherein R is a C1-8alkyl group optionally substituted with one or more halogen atoms, or wherein the iodine(III) compound is I(SO4)(HSO4); and wherein the process further comprises adding NO2. A process for the preparation of methyl bisulfate comprising: (a) adding methane to a solution of an iodine(III) compound in H2SO4 / SO3in a reaction vessel, wherein the iodine in the iodine(III) compound is bonded to at least one -OSO2R, -OC(O)R or - N(SO2R)2 group, wherein R is a C1-8 alkyl group optionally substituted with one or more halogen atoms, or wherein the iodine(III) compound is I(SO4)(HSO4) ; (b) allowing the methane to react with the iodine(III) compound in the reaction mixture formed in step (a). The process of embodiment 37, further comprising: (c) adding NO2 to the reaction vessel. The process of embodiment 38, wherein NO2and O2are added to the reaction vessel in step (c). The process of embodiment 38 or embodiment 39, further comprising: (d) adding further methane to the reaction vessel after adding NO2 to the reaction vessel; (e) allowing the methane to react with the iodine(III) compound in the reaction mixture formed in step (a); (f) adding further NO2 to the reaction vessel during or after step (b); (g) repeating steps (d) to (f). The process of embodiment 40, wherein the reaction vessel is degassed before the further methane is added in step (d). A process for the preparation of methyl bisulfate comprising: (a) adding I2 to H2SO4 / SO3 in a reaction vessel; (b) adding NO2to the reaction vessel; (c) adding methane to the reaction vessel. The process of embodiment 42, wherein the reaction vessel is degassed after step (b), before adding methane to the reaction vessel in step (c). The process of any one of embodiments 37-43, further comprising hydrolysing the methyl bisulfate to form methanol. The process of any one of embodiments 38-44, wherein the solution is cooled to below 0°C before NO2is added. The process of any one of embodiments 37-45, wherein the H2SO4 / SO3 is H2SO4 that contains dissolved SO3 in an amount of 1-65% w / w, preferably 10-65% w / w. The process of any one of embodiments 37-46, wherein the methane is allowed to react with the iodine(III) compound at a temperature in the range from about 10 °C to about 200 °C, preferably in the range from about 20 °C to about 150 °C, more preferably in the range from about 50 °C to about 125 °C. The process of any one of embodiments 37-47, wherein methane is added to the reaction vessel at a pressure of about 0.5 bar to about 100 bar. The process of any one of embodiments 1-11 or 25-36, wherein the acid is a carboxylic acid or a sulfonic acid, wherein the carboxylic acid or sulfonic acid has a pKa of less than 1 on the aqueous scale or wherein the carboxylic acid or sulfonic acid has a Hammett acidity function (H0) of less than -2, or wherein the acid is HNO3. The process of embodiment 49, wherein the carboxylic acid or sulfonic acid contains a halogenated alkyl or aryl group, preferably wherein the halogen atoms are fluorine or chlorine atoms. The process of any one of embodiments 1-18, 25-36 or 49-50, wherein the acid is an acid that has a pKa on the aqueous scale of less than 3. The process of any one of embodiments 1-18, 25-36 or 49-50, wherein the acid is an acid that has a pKa on the aqueous scale of less than 1, preferably less than 0, more preferably less than -1. The process of any one of embodiments 1-18, 25-36 or 49-50, wherein the acid is an acid that has a Hammett acidity function (H0) of less than -2. The process of any one of embodiments 1-18, 25-36 or 49-50, wherein the acid is an acid that has a Hammett acidity function (H0) of less than -6, preferably less than -10. The process of any one of embodiments 1-18 or 25-36, wherein the acid is a perfluorinated C1-8 alkyl sulfonic acid or a perfluorinated C1-8alkyl carboxylic acid. The process of any one of embodiments 1-18 or 25-36, wherein the acid is CF3SO3H, CH3SO3H, CF3CF2SO3H, CF3CF2CF2SO3H, FSO3H, CF3CO2H, CF3CF2CO2H, CF3CF2CF2CO2H, CCl3CO2H, HN(SO2CF3)2, HN(SO2CF2CF3)2 or HNO3. The process of embodiment 56, wherein the acid is CF3SO3H, CH3SO3H, CF3CF2SO3H, FSO3H, CF3CO2H or CF3CF2CO2H. The process of embodiment 57, wherein the acid is CF3SO3H. The process of any one of embodiments 1-11 and 25-36, wherein the iodine(III) compound is I(OTf)3and the acid is CF3SO3H. The process of any one of embodiments 1-11 or 25-36, wherein the acid is the conjugate acid of the -OSO2R, -OC(O)R or -N(SO2R)2group that is attached to the iodine atom, or is a weaker acid than the conjugate acid of the -OSO2R, -OC(O)R or -N(SO2R)2group that is attached to the iodine atom, preferably wherein the acid is the conjugate acid of the -OSO2R, -OC(O)R or -N(SO2R)2 group that is attached to the iodine atom. The process of any one of embodiments 1-41 or 44-60, wherein R is a C1-4alkyl group substituted with at least one halogen atom or wherein R is a perfluorinated C1-8alkyl group. The process of any one of embodiments 1-41 or 44-60, wherein R has the formula CnF2n+1 or CnCl2n+1, wherein n is 1-4, preferably wherein n is 1 or 2. The process of embodiment 62, wherein R is CF3. The process of any one of embodiments 1-11 or 37-41 or 44-63, wherein the iodine(III) compound has the formula I(OSO2R)3, I(OC(O)R)3 or I[N(SO2R)2]3. 65. The process of embodiment 64, wherein the iodine(III) compound has the formula I(OSO2R)3or I[N(SO2R)2]3 and R is perfluorinated. 66. The process of any one of embodiments 19-36, wherein the iodine(III) compound has the formula I(OSO2R)3or I[N(SO2R)2]3. 67. The process of any one of embodiments 64-66, wherein the iodine(III) compound has the formula I(OSO2R)3. 68. The process of any one of embodiments 1-11 or 19-41 or 44-58 or 60-66, wherein the iodine(III) compound is I(OTf)3or I(NTf2)3. 69. The process of embodiment 68, wherein the iodine(III) compound is I(OTf)3. 70. The process of any one of embodiments 1-9 or 11, wherein the iodine(III) compound is I(OTf)3and the acid is CF3SO3H, wherein the process further comprises isolating methanol from the reaction mixture in the form of a solid complex formed between methanol and CF3SO3H. 71. The process of any one of embodiments 12-18, wherein the acid is CF3SO3H, wherein the process further comprises isolating methanol from the reaction mixture in the form of a solid complex formed between methanol and CF3SO3H. 72. The process of any one of embodiments 1-11 or 36-41, wherein the iodine(III) compound is I(SO4)(HSO4). 73. The process of any one of embodiments 1-11 or 36, wherein the iodine(III) compound is I(CF3CO2)3and the acid is H2SO4 / SO3. 74. The process of any one of embodiments 37-41 and 44-48, wherein the iodine(III) compound is I(CF3CO2)3. 75. The process of any one of embodiments 1-11 or 25-36, wherein the solution of the iodine(III) compound in acid does not contain chloride ions. 76. The process of any preceding embodiment, wherein the process comprises the addition of NO2and wherein after the NO2has been reduced to NO, the NO is mixed with O2in a vessel that does not contain methane or ethane in order to regenerate the NO2. 77. The process of any one of embodiments 1-18 and 36, wherein the acid is H2SO4 / SO3. The invention has been described in detail above, including preferred embodiments thereof. However, the invention is not limited except by the appended claims. Those skilled in the art will appreciate that modifications can be made to the preferred ways of implementing the invention that are described above, whilst remaining within the scope of the claims.

Claims

CLAIMS 1. A process for producing methanol comprising: (a) adding methane to a solution of an iodine(III) compound in acid in a reaction vessel, wherein the iodine in the iodine(III) compound is bonded to at least one -OSO2R, -OC(O)R or -N(SO2R)2group, wherein R is a C1-8 alkyl group optionally substituted with one or more halogen atoms, or wherein the iodine(III) compound is I(SO4)(HSO4), wherein the acid is an acid that has a pKa of less than 3 on the aqueous pKa scale or the acid is an acid that has a Hammett acidity function (H0) of less than -2; (b) allowing the methane to react with the iodine(III) compound in the reaction mixture formed in step (a); and (c) adding NO2 to the reaction vessel.

2. The process of claim 1, further comprising: (d) adding further methane to the reaction vessel after adding NO2to the reaction vessel in step (c); (e) allowing the methane to react with the iodine(III) compound in the reaction mixture formed in step (d); (f) adding further NO2 to the reaction vessel during or after step (e); and (g) repeating steps (d) to (f).

3. A process for producing methanol comprising: (a) adding NO2 to a solution of I2 in acid in a reaction vessel, wherein the acid is an acid having the formula RSO3H, RCO2H or HN(SO2R)2 or wherein the acid is H2SO4 / SO3, wherein R is a C1-8 alkyl group optionally substituted with one or more halogen atoms, wherein the acid is an acid that has a pKa of less than 3 on the aqueous scale or the acid is an acid that has a Hammett acidity function (H0) of less than -2; (b) adding methane to the reaction vessel; and (c) allowing the methane to react with the reaction mixture formed in step (a); wherein said process optionally further comprises: (d) adding further NO2to the reaction vessel after step (c) or adding O2to regenerate NO2; (e) adding further methane to the reaction vessel during or after step (d); (f) allowing the methane to react with the reaction mixture formed in step (e); and (g) repeating steps (d) to (f).

4. A process for the preparation of a compound of the formula CH3X or XCH2CH2X comprising reacting methane or ethane with an iodine(III) compound, wherein X is -OSO2R or -N(SO2R)2 and wherein the iodine in the iodine(III) compound is bonded to at least one X group, wherein R is a C1-8 alkyl group optionally substituted with one or more halogen atoms.

5. The process of claim 4, wherein either (i) methane or ethane gas is passed over the iodine(III) compound in the solid state, optionally wherein NO2is passed over the iodine compound that remains after methane or ethane gas has been passed over the iodine(III) compound, in order to regenerate the iodine(III) compound; or (ii) the methane or ethane is added to a solution of the iodine(III) compound in acid in a reaction vessel, wherein the acid is an acid that has a pKa of less than 3 on the aqueous scale or the acid is an acid that has a Hammett acidity function (H0) of less than -2, providing that the acid is not H2SO4 / SO3,wherein the process optionally further comprises adding NO2to the reaction vessel, preferably wherein the NO2 is added to the reaction vessel after the formation of I2.

6. A process for the preparation of ethylene glycol comprising adding ethane to a solution of an iodine(III) compound in acid in a reaction vessel, wherein the acid is an acid that has a pKa of less than 3 on the aqueous scale or the acid is an acid that has a Hammett acidity function (H0) of less than -2, wherein the iodine in the iodine(III) compound is bonded to at least one X group, wherein X is -OSO2R or -N(SO2R)2 and wherein R is a C1-8 alkyl group optionally substituted with one or more halogen atoms, or wherein the iodine(III) compound is I(SO4)(HSO4); and wherein the process further comprises adding NO2.

7. A process for the preparation of methyl bisulfate comprising: (a) adding methane to a solution of an iodine(III) compound in H2SO4 / SO3in a reaction vessel, wherein the iodine in the iodine(III) compound is bonded to at least one -OSO2R, -OC(O)R or -N(SO2R)2 group, wherein R is a C1-8 alkyl group optionally substituted with one or more halogen atoms, or wherein the iodine(III) compound is I(SO4)(HSO4); (b) allowing the methane to react with the iodine(III) compound in the reaction mixture formed in step (a); wherein said process optionally further comprises: (c) adding NO2 to the reaction vessel.

8. A process for the preparation of methyl bisulfate comprising: (a) adding I2to H2SO4 / SO3in a reaction vessel; (b) adding NO2to the reaction vessel; and (c) adding methane to the reaction vessel.

9. The process of any one of claims 1-3 or 5-6, wherein the acid is a carboxylic acid or a sulfonic acid, wherein the carboxylic acid or sulfonic acid has a pKa of less than 3 on the aqueous scale or the acid is an acid that has a Hammett acidity function (H0) of less than -2, or wherein the acid is HNO3.

10. The process of any one of claims 1-3, 5-6 or 9, wherein the acid is a perfluorinated C1-8 alkyl sulfonic acid or a perfluorinated C1-8alkyl carboxylic acid.

11. The process of any one of claims 1-3 or 5-6, wherein the acid is CF3SO3H, CH3SO3H, CF3CF2SO3H, CF3CF2CF2SO3H, CF3CO2H, CF3CF2CO2H, CF3CF2CF2CO2H, CCl3CO2H, FSO3H, HN(SO2CF3)2, HN(SO2CF2CF3)2 or HNO3; preferably wherein the acid is CF3SO3H.

12. The process of any one of claims 1-7 or 9-11, wherein R has the formula CnF2n+1or CnCl2n+1, wherein n is 1-4, preferably wherein n is 1 or 2.

13. The process of any one of claims 1-2, 4-7 or 9-12, wherein the iodine(III) compound has the formula I(OSO2R)3or I[N(SO2R)2]3.

14. The process of any one of claims 1-2, 4-7 or 9-12, wherein the iodine(III) compound is I(OTf)3 or I(NTf2)3, preferably I(OTf)3.

15. The process of any one of claims 1-2, 6-7 or 9-12, wherein the iodine(III) compound is I(SO4)(HSO4).

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