Acetate pyrolysis

Abstract

This invention relates to a process for the production of terminal alkenes by pyrolysis of an ester.

Description

[0001] P383687WO Specification

[0002] 1

[0003] Acetate Pyrolysis

[0004] This invention relates to a process for the continuous production of terminal alkenes having 4 to 20 carbon atoms by pyrolysis of an appropriate ester.

[0005] BACKGROUND

[0006] Terminal alkenes are intermediates for commercial products in many fields. For example, they can be intermediates in performance polymers such as polyethylene copolymers and the synthesis of 1,2-alkanediols which are common components of various creams and ointments, such as in moisturizers in the cosmetic field. Control of purity of a commercial product is often essential, and it is easier to obtain it when their intermediates are already highly pure.

[0007] Terminal alkenes can be manufactured through various synthetic routes, but many of these routes lead to mixtures of regioisomers.

[0008] Terminal alkenes can notably come from ethylene oligomerization. However, this method is not fully selective towards terminal alkenes. It also leads to isomers such as branched olefins or internal olefins as by-products. Separation of such by-products is difficult due to the small boiling point differences between alkene isomers and these can impact the properties of the downstream products, often negatively.

[0009] Another known alternative route to terminal alkenes is dehydration of linear alcohols as described in WO 2004 / 078336 or US 10882803. This pathway allows avoiding obtaining branched olefins as side-product. However, alcohols and water are not good leaving groups and therefore an acidic catalyst is required. The acidic catalyst then leads to isomerisation and thus internal alkenes are present at unacceptable amounts.

[0010] Access to terminal alkenes by pyrolysis of appropriate alkyl esters has been described for example in Journal of Organic Chemistry, vol 51, no. 2, 1986, pages 242-245, Journal of Organic Chemistry, vol 26, no9, 1961, pages 3193-3196 and Kinetics and Catalysis vol 55, no. 2, 2014, pages 212-216. It leads to high regioselectivity towards the terminal alkene. However, these synthetic routes have never been described on an industrial scale. Working at high temperature with hydrocarbon compounds can generate carbon residues as a side product which can stick to the reactor’s walls. Excessive clogging of the reactor can then be observed and this strongly impairs the efficiency of continuous production and blockages of reactors are common, leading to safety issues such as pressure build up which must be managed. Consequently, the production needs to be periodically stopped for extended periods of time and the reactor system needs to be cleaned when possible or even replaced sometimes, therefore adding additional cost to these processes and high levels of nonproductive time. Physical cleaning is expensive and time consuming and introduces P383687WO Specification

[0011] 2 additional stresses and strains on the reactor and joints due to thermal cycling and access requirements.

[0012] It is an aim of the invention to provide a process for the continuous production of a terminal alkene with high purity and high efficiency at industrial scale and minimised or no downtime for carbon removal.

[0013] BRIEF SUMMARY OF THE DISCLOSURE

[0014] A first aspect of the invention is a process for the continuous production of a terminal alkene having 4 to 20 carbon atoms comprising the steps (i), (ii), (iii), (iv) and optionally (v):

[0015] (i) feeding a flow reactor with a stream (a) comprising a compound of formula (I) wherein:

[0016] - X is independently C2-is-alkyl;

[0017] R3is independently selected from H, and Ci-6-alkyl optionally substituted with from 1 to 9 halo groups;

[0018] (ii) feeding the flow reactor with a stream (b) comprising carbon dioxide (CO2),

[0019] (iii) heating stream (a) and stream (b), if present, in a heating part of the flow reactor at a temperature in the range from 400 to 600°C to convert the compound of formula (I) into the corresponding terminal alkene to provide a product stream (c) comprising the terminal alkene,

[0020] (iv) recovering product stream (c),

[0021] (v) optionally heating stream (b) in the heating part of the flow reactor at a temperature in the range from 400 to 900°C; wherein the process is carried out such that stream (b) is heated in the heating part of the flow reactor during either step (iii) or step (v) or both.

[0022] It may be that the process is carried out such that stream (b) is heated in the heating part of the flow reactor during either step (iii) or step (v). P383687WO Specification

[0023] 3

[0024] The inventors of the present invention have found that terminal alkenes can be obtained via pyrolysis of corresponding alkyl esters with high purity and notably high regioselectivity. They have also found that feeding the flow reactor in which the pyrolysis reaction is happening or has happened with a stream of carbon dioxide reduces clogging of the system by carbon residue and thus leads to a higher efficiency of the continuous process. Surprisingly the stream of carbon dioxide does not lead to significant side reactions with the starting material and products of the pyrolysis under the conditions used. Thus, the stream of CO2 can be fed at the same time as the pyrolysis occurs. It can also be fed after stopping the pyrolysis, there is no need to flush the system before feeding the flow reactor with the stream of CO2 or flushing afterwards before starting the pyrolysis again. The process is thus easy, fast and it maximises productivity.

[0025] Without being bound to any theories, the inventors believe that two mechanisms are taking place in the presence of CO2 (i) radicals and other reactive minor intermediates are intercepted by the CO2 prior to becoming carbon thereby reducing the rate of carbon laydown and (ii) the carbon produced during the reaction reacts with CO2 via a comproportionation reaction to produce CO and is thereby removed from the system. The comproportionation reaction is an equilibrium reaction between carbon and carbon dioxide to produce carbon monoxide. Typically in industry, this is performed above 900°C where the equilibrium is in favour of CO. In our case, we discovered that it could be performed at lower temperature and at a sufficient rate to be useful.

[0026] In the presence of alkyl acetate feed an equilibrium amount of carbon slowly builds in the reactor until the rate of formation is equal to the rate of consumption. Periodically increasing the temperature with or without the presence of feed but in the presence of CO2 allows for a deeper removal of the carbon in the reactor via conversion to carbon monoxide, and in this way plant operational performance is maximised.

[0027] In a second aspect of the invention is provided a terminal alkene having a structure according to formula (IV): wherein X is independently C2-is-alkyl; wherein the terminal alkene is obtainable (e.g. obtained) according to the method of any one of claims 1 to 16. P383687WO Specification

[0028] 4

[0029] DETAILED DESCRIPTION

[0030] Definitions

[0031] When a process is carried out in a temperature in a specified range of temperatures, it is meant that process is carried out at a temperature or temperatures within that range. When a process is carried out a temperature in a specified range of temperatures this does not necessarily mean that the process is carried out at a single temperature within the specified range. For example, a process carried out at a temperature in the range from 400 °C to 600 °C may be carried out at 480 °C for a duration of time and 520 °C for another duration of time.

[0032] Bara is the unit of absolute pressure. Absolute pressure is a pressure that is relative to the zero pressure in empty, air-free space. This reference pressure is the ideal or absolute vacuum. Absolute pressure may be measured by techniques known in the art, e.g. by the use of manometer.

[0033] The term ‘inert gas’ is intended to include any gas which is able to displace oxygen gas but is unreactive in the reaction conditions to which it is subjected. Suitable gases include nitrogen, and the noble gases e.g. argon and krypton.

[0034] The term Cm-Cnrefers to a group with m to n carbon atoms.

[0035] The term “alkyl” refers to a monovalent linear or branched saturated hydrocarbon chain. For example, Ci-C4-alkyl may refer to methyl, ethyl, n-propyl, / so-propyl, n-butyl, sec-butyl and terf-butyl. The prefix “n-“, as in, e.g. n-C2-2o-alkyl, means that the alkyl chain is linear (i.e. unbranched). n-Cs- -alkyl, e.g., therefore covers n-propyl, n-butyl, n-pentyl, n-hexyl, n- heptyl, n-octyl, n-nonyl, n-decyl, n-undecyl, n-dodecyl and n-tridecyl.

[0036] The term “substituted” as used herein in reference to a moiety means that one or more, e.g. 1 , 2 or 3, of the hydrogen atoms in said moiety are replaced independently of each other by the corresponding number of the described substituents.

[0037] Included within the scope of the present invention are all stereoisomers, geometric isomers and tautomeric forms of the compounds of the invention, including compounds exhibiting more than one type of isomerism, and mixtures of one or more thereof.

[0038] Throughout this specification these abbreviations have the following meanings: FID Flame Ionisation Detector

[0039] HPLC High-Performance Liquid Chromatography P383687WO Specification

[0040] 5

[0041] TGA Thermogravimetric Analysis.

[0042] Throughout the description and claims of this specification, the words “comprise” and “contain” and variations of them mean “including but not limited to”, and they are not intended to (and do not) exclude other moieties, additives, components, integers or steps. Throughout the description and claims of this specification, the singular encompasses the plural unless the context otherwise requires. In particular, where the indefinite article is used, the specification is to be understood as contemplating plurality as well as singularity, unless the context requires otherwise.

[0043] Features, integers, characteristics, compounds, chemical moieties or groups described in conjunction with a particular aspect, embodiment or example of the invention are to be understood to be applicable to any other aspect, embodiment or example described herein unless incompatible therewith. All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and / or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and / or steps are mutually exclusive. The invention is not restricted to the details of any foregoing embodiments. The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed.

[0044] The reader's attention is directed to all papers and documents which are filed concurrently with or previous to this specification in connection with this application and which are open to public inspection with this specification, and the contents of all such papers and documents are incorporated herein by reference.

[0045] The following embodiments apply to the method for forming a terminal alkene. These embodiments are independent and interchangeable. Any one embodiment may be combined with any other embodiment, where chemically allowed. In other words, any of the features described in the following embodiments may (where chemically allowable) be combined with the features described in one or more other embodiments. In particular, where a method or compound is exemplified or illustrated in this specification, any two or more of the embodiments listed below, expressed at any level of generality, which encompass that method or compound may be combined to provide a further embodiment which forms part of the present disclosure. P383687WO Specification

[0046] 6

[0047] The process according to the invention is a process for the continuous production of a terminal alkene having 4 to 20 carbon atoms wherein X has the same meaning as for compound of formula (I) comprising the following steps:

[0048] (i) feeding a flow reactor with a stream (a) comprising a compound of formula (I) wherein:

[0049] X is independently C2-is-alkyl;

[0050] R3is independently selected from H, Ci-6-alkyl optionally substituted with from 1 to 9 halo groups;

[0051] (ii) feeding the flow reactor with a stream (b) comprising carbon dioxide (CO2),

[0052] (iii) heating stream (a) in a heating part of the flow reactor at a temperature ranging from 400- 600°C to obtain conversion of compound of formula (I) into corresponding terminal alkene and forming of a product stream (c) comprising terminal alkene and optionally compound of formula (I),

[0053] (iv) recovering product stream (c),

[0054] (v) heating stream (b) in the heating part of the flow reactor at a temperature ranging from 400-900°C.

[0055] Inlet - steps (i) and (ii)

[0056] Stream (a) comprises a compound of formula (I) P383687WO Specification wherein:

[0057] - X is independently C2-is-alkyl;

[0058] R3is independently selected from H, Ci-6-alkyl optionally substituted with from 1 to 9 halo groups;

[0059] It may be that R3is selected from H and C1-C4 alkyl. It may be that R3is unsubstituted C1-C4 alkyl. It may be that R3is Ci-Cs-alkyl. It may be that R3is unsubstituted C1-C3 alkyl. It may be that R3is methyl, e.g. unsubstituted methyl.

[0060] It may be that R3is C1-C4 alkyl substituted with halo groups. Said halo groups may be fluoro groups.

[0061] It may be that X is independently n-C2-i8-alkyl. It may be that X is C2-i6-alkyl, e.g. / 7-C2-16- alkyl. It may be that X is C2-i2-alkyl, e.g. n-C2-i2-alkyl. It may be that X is Cs- -alkyl, e.g. n- Cs- -alkyl. It may be that X is selected from n-butyl, n-pentyl, n-hexyl, n-heptyl, n-octyl and n-decanyl.

[0062] The compound of formula (I) may be selected from the group consisting of hexyl acetate, heptyl acetate, octyl acetate, nonyl acetate, decyl acetate and dodecyl acetate. The compound of formula (I) may be decyl acetate. The compound of formula (I) may be octyl acetate. The compound of formula (I) may be heptyl acetate. The compound of formula (I) may be hexyl acetate.

[0063] Stream (a) may comprise mainly the compound of formula (I). Stream (a) may consist of the compound of formula (I). There can be some side-products in stream (a), e.g. coming from obtention of compound of formula (I). Stream (a) can notably comprise acetic acid. Typically, no additional compound is added intentionally to stream (a). Preferably, stream (a) comprises at least 90wt.% of compound of formula (I), more preferably at least 95 wt.%.

[0064] The method may comprise the step of obtaining the compound of formula (I). Compound of formula (I) may be obtained by acylation of the corresponding alcohol or any other means commonly known in the art for producing an ester. P383687WO Specification

[0065] 8

[0066] It may be that the compound of Formula (I) is prepared by reacting a compound of Formula

[0067] (II) with a compound of Formula (Illa) or (I lib): wherein X, and R3are as defined above.

[0068] By-products and / or unreacted starting material may be removed, e.g. removed by distillation, prior to step (i).

[0069] The compound of formula (II), (Illa) or (I lib) may be derived from natural source by any reasonable means such as extraction from biomass.

[0070] The compound of Formula (II) may be derived from a natural source, such as extraction from biomass or by reduction, for example from the hydrogenation of fatty acids or sugars or from the homologation of ethanol.

[0071] Stream (a) may be in the gas form. The method may therefore comprise the step of vaporizing the compound of formula (I) before step (i).

[0072] Stream (b) comprises carbon dioxide (CO2).

[0073] Stream (b) may comprise mainly CO2. Stream (b) may consist of carbon dioxide. Stream (b) may comprise more than 95 wt.% of carbon dioxide.

[0074] Stream (b) may be in the gas form.

[0075] Other streams

[0076] In one embodiment, there is no other stream feeding the flow reactor, i.e. streams (a) and (b) are the only streams feeding the flow reactor.

[0077] In another embodiment, another stream can be fed to the flow reactor. It can be a stream (d) comprising nitrogen or argon. It may be that at least a portion of stream (d) can be fed to the reactor at the same time as at least a portion of stream (a). This may particularly be the case when no portion of stream (b) is fed to the flow reactor at the same time as any portion of stream (a).

[0078] Step (i) feeding a flow reactor with stream (a) P383687WO Specification

[0079] 9

[0080] In step (i), a flow reactor is fed with stream (a). It may be continuous feeding.

[0081] It may be that stream (a) is fed into the reactor at a flow rate in the range from 0.6 to 12 mols per L reactor volume per hour. Typically, these flow rates are adequate for a reactor at around 3 bara pressure.

[0082] The feed rate of stream (a) can vary during the process. It can be high during step (iii) to increase productivity of the conversion of compound of formula (i) into corresponding alkene. The feed rate of stream (a) may be lower during step (v). The feed rate of stream (a) may even be stopped during step (v).

[0083] Step (ii) feeding the flow reactor with stream (b)

[0084] In step (ii), the flow reactor is fed with stream (b). It may be continuous feeding or discontinuous feeding, e.g. intermittent or periodic feeding.

[0085] It may be that at least a portion of step (ii) and at least a portion of step (i) are performed at the same time. It may be that streams (a) and (b) are mixed within the reactor and the mixture of stream (a) and (b) is heated in the heating part of the reactor.

[0086] Alternatively, it may be that no portion of step (ii) is performed at the same time as any portion of step (i).

[0087] Stream (b) can be fed into the reactor at a flow ratio in the range from 0.1 to 20 mols of compound of formula (I) per mol of CO2. However, the feed rate will typically be selected to be sufficient to manage the carbon accumulation in the reactor. Should the feed be intermittently stopped, and the temperature elevated to accelerate carbon removal then the CO2 feed rate may be in the range from 0.1 to 1 mol CO2 / L reactor / h however the exact flow rate conditions would be dependent on the design of the equipment and temperature attained.

[0088] The feed rate of stream (b) may be lowered during step (iii). The feed rate of stream (b) may even be stopped during step (iii). The feed rate of stream (b) may be increased during step (v). The feed rate of stream (b) may be in the range 0.1 and 5 mols / L reactor / h.

[0089] Reaction conditions - Step (iii) - Pyrolysis

[0090] Step (iii) comprises heating stream (a) and stream (b), if present, in a part of the flow reactor at a temperature in the range from 400 to 600°C to obtain conversion of compound of formula (I) into corresponding terminal alkene and forming of a product stream (c) comprising terminal alkene and optionally compound of formula (I).

[0091] Stream (b) may be present in the heating part of the reactor during step (iii). It may be that stream (b) is not present in the heating part of the reactor during step (iii). It can be present P383687WO Specification

[0092] 10 discontinuously. When stream (b) is present, the carbon residue produced during the pyrolysis reaction of step (iii) can react with the CO2 of stream (b) to give carbon monoxide (CO).

[0093] It may be that step (iii) comprises heating stream (a) and stream (b), if present, at a temperature in the range of from 450 °C to 590 °C, e.g. from 480 °C to 580 °C. It may be that step (iii) comprises heating stream (a) and stream (b), if present, at a temperature in the range of from 500 °C to 570 °C, preferably from 520 °C to 560 °C. It may be that step (iii) comprises heating stream (a) and stream (b), if present, at a temperature in the range of from 500 to 580°C; optionally a temperature in the range from 520 to 560°C.

[0094] Step (iii) may be carried out under pressure, i.e. at a pressure above 1 bara. Step (iii) may be carried out at a pressure ranging from 1.05 to 7 bara, notably from 1.1 to 5 bara, preferably from 1.1 to 4 bara.

[0095] Step (iii) may be carried out in the presence of a catalyst. Preferably, however, step (iii) is carried out in the absence of a catalyst. Common catalysts include acid catalysts, base catalysts and metals on high surface area supports. More specifically, common catalysts include zeolite, e.g. zeolite Y and Zeolite Socony Mobil-5 (ZSM-5), silicoaluminophosphate (SAPO), silica-alumina, sulfated zirconium oxide, Fluid Catalytic Cracking (FCC) catalysts, zeolite ferrierite (FER), alumina, e.g. gamma-phase alumina and inert balls, e.g. low surface area alpha alumina balls or glass spheres.

[0096] Conditions performed in step (iii) may be such that the compound of formula (I) in stream (a) is not converted entirely into terminal alkene. It may be, therefore that during step (iii), compound of formula (I) is partially converted into terminal alkene. More particularly, conversion is in the range from 50 to 80 wt. %, e.g. in the range from 55% to 75 wt. %.

[0097] Step (iv) - Outlet

[0098] Step (iv) comprises recovering product stream (c).

[0099] Stream (c) comprises a terminal alkene obtained by pyrolysis of a compound of formula (I). It can also comprise compound of formula (I). Indeed, step (iii) can lead to partial conversion of compound of formula (I) so that stream (c) comprises a compound of formula (I) and its corresponding terminal alkene after partial pyrolysis of compound of formula (I).

[0100] Product stream (c) may comprise the terminal alkene in the range from 50 to 80 wt. % (wt % relative to the weight of product stream (c)), e.g. in the range from 55% and 75 wt. % (wt% relative to the total weight of product stream (c)). P383687WO Specification

[0101] 11

[0102] Stream (c) may further comprise unreacted compound of formula (I).

[0103] Stream (c) can also comprise minor side-products of the reaction of pyrolysis.

[0104] Stream (c) can also comprise CO2 and optionally CO. Indeed, when stream (b) and stream

[0105] (a) are mixed within the flow reactor, step (iii) comprises heating the mix of stream (a) and

[0106] (b). CO2 of stream (b) can react with carbon residue produced during the pyrolysis reaction and lead to production of CO. Stream (b) may be fed into the flow reactor at a flow rate high enough so that there is no full consumption of CO2, i.e. stream (b) may be fed into the flow reactor at a flow rate high enough to ensure that stream (c) comprises CO2. It may be that stream (b) is fed into the flow reactor at a flow rate such that the CO2 / CO ratio in stream (c) is higher than 1 . It may be that stream (b) is fed into the flow reactor at a flow rate such that the CO2 / CO ratio in stream (c) is higher than 3. It may be that stream (b) is fed into the flow reactor at a flow rate such that the CO2 / CO ratio in stream (c) is higher than 5.

[0107] Step (v) comprises heating stream (b) in the heating part of the flow reactor at a temperature in the range from 400 to 900°C.

[0108] The heating part of the flow reactor corresponds to the heating part mentioned in step (iii).

[0109] Step (v) is an optional step. It may be that the process does not comprise step (v). This will typically be the case if stream (b) has been heated in the heating part during step (iii).

[0110] It may be that the process comprises step (v). This may be the case whether or not stream (b) has been heated in the heating part during step (iii).

[0111] Step (v) may be carried out when stream (b) has been heated in the heating part during step (iii). Step (v) may be carried out when stream (b) has not been heated in the heating part during step (iii).

[0112] Stream (a) can be present in the heating part during step (v). Typically, stream (a) is not present during step (v).

[0113] Stream (c) can be present in the heating part during step (v). Typically, stream (c) is not present during step (v).

[0114] During step (v), the carbon residue produced during the pyrolysis reaction of step (iii) can react with the CO2 of stream (b) to give carbon monoxide (CO). P383687WO Specification

[0115] 12

[0116] It may be that step (v) comprises heating stream (b) at a temperature in the range from 550 °C to 750 °C, e.g. from 480 °C to 600 °C.

[0117] It may be that step (v) comprises heating stream (b) at a temperature in the range from 650 °C to 800 °C, preferably from 700°C to 750°C.

[0118] Step (v) may be carried out under pressure, in other words at a pressure above 1 bara. Step (v) may be carried out at a pressure ranging from 1.05 to 7 bara, notably from 1.1 to 5 bara, preferably from 1.1 to 4 bara.

[0119] Processes in which CO2 is present in the heating part of the reactor during step (iii)

[0120] In some embodiments, at least a portion of step (ii) and at least a portion of step (i) are performed at the same time. They may be performed simultaneously, i.e. they may start and end at the same time. It may be that there is at least one point in the process in which stream (a) and stream (b) are both being fed into the flow reactor.

[0121] It may be that step (i) is continuous. It may be that step (i) is discontinuous. It may be that step (ii) is continuous. It may be that step (ii) is discontinuous. It may be that both steps (i) and (ii) are continuous. Where both steps are continuous, they may be simultaneous. Where both steps are continuous, they may not be simultaneous. It may be that both steps (i) and

[0122] (ii) are discontinuous. Where both steps are discontinuous, they may be synchronized. Alternatively, where both steps are discontinuous, they may not be synchronized. It may be that step (i) is continuous and step (ii) is discontinuous. It may be that step (i) is discontinuous and step (ii) is continuous. Step (i) may start before step (ii) starts providing at least a portion of step (i) and at least a portion of step (ii) are performed at the same time. Step (ii) may start before step (i) starts providing at least a portion of step (i) and at least a portion of step (ii) are performed at the same time. Step (i) may finish before step (ii) finishes providing at least a portion of step (i) and at least a portion of step (ii) are performed at the same time. Step (ii) may finish before step (i) finishes providing at least a portion of step (i) and at least a portion of step (ii) are performed at the same time.

[0123] In other terms, it may be that stream (b) is fed to the flow reactor when the flow reactor is also fed with stream (a). Then, streams (a) and (b) are mixed within the flow reactor.

[0124] Streams (a) and (b) may be mixed in the heating part of the flow reactor. Streams (a) and (b) may be mixed in the flow reactor before the heating part. In these embodiments, during step

[0125] (iii), a mix of streams (a) and (b) is heated in the heating part of the flow reactor at the indicated temperature range for step (iii). P383687WO Specification

[0126] 13

[0127] Then, in these embodiments, during step (iii), the carbon residue formed during the pyrolysis reaction is converted at least partially by the CO2 into CO.

[0128] Where CO2 is present in the heating part of the flow reactor in step (iii), it may be that step (v) is performed. Where CO2 is present in the heating part of the flow reactor in step (iii), it may be that step (v) is not performed.

[0129] Feeding the flow reactor with stream (b) can be done discontinuously. Feeding the flow reactor with stream (b) can be done continuously.

[0130] When feeding the flow reactor with stream (b) is done discontinuously, step (iii) may alternate between heating stream (a) alone and heating a mix of stream (a) and stream (b).

[0131] When the flow reactor is fed continuously with stream (b), step (iii) comprises heating a mix of streams (a) and (b) continuously.

[0132] Processes in which step (v) is performed

[0133] In some embodiments, step (v) is performed. Step (v) may involve heating stream (b) in the heating part of the flow reactor to a temperature in the range 650 to 800°C, e.g. in the range 700 to 750°C.

[0134] In a variant, step (v) happens when stream (b) has not been heated in the heating part during step (iii). In other terms, stream (b) is not fed to the flow reactor whilst the flow reactor is fed with stream (a) and only stream (a) is heated during step (iii). Stream (b) is fed and heated afterwards. Then, no portion of step (ii) is performed at the same time as any portion of step (i). In these embodiments, steps (ii) and (v) happen after steps (i) and (iii).

[0135] It may be that no portion of step (ii) is performed at the same time as any portion of step (i). In another variant, step (v) happens when stream (b) has been heated during step (iii). In other terms, during step (iii), a mix of stream (a) and (b) has been heated at the temperature range required for step (iii) and, after step (iii), step (v) is performed so that stream (b) and optionally stream (a) is heated at the temperature required for step (v). In this variant stream (b) is heated twice, typically at two different temperatures, once during step (iii) and once during step (v).

[0136] Step (vi) Purification

[0137] The processes of the invention form a terminal alkene. The terminal alkene typically has a structure according to formula (IV): P383687WO Specification

[0138] 14 wherein X has the same meaning as for compound of formula (I). The terminal alkene is present in stream (c) that is recovered in step (iv).

[0139] After step (iv), the composition of stream (c) can be partially purified in order to isolate the terminal alkene.

[0140] Stream (c) is typically a gas. Stream (c) may be a mixture of a gas and a liquid.

[0141] Stream (c) may be condensed before purification, e.g. by cooling. Stream (c) may be partially condensed before purification, e.g. by cooling. Typically, when stream (c) is cooled you get a partition between a liquid phase and a gas phase. It may be that the majority of the alkene is in the liquid phase and the majority of the CO2 and other volatiles (methane, ethene, propene) are in the gas phase.

[0142] Stream (c) may be purified in the gas form.

[0143] Stream (c) can be fed into a distillation column. Typically, stream (c) will be fed in as a gas. It may be that stream (c) is fed in as a mixture of a gas and a liquid.

[0144] The distillation column can comprise 3 exits:

[0145] First exit: non condensable and minor volatile side product gases, (typically some or all of the following: CO2; gas from stream (d), CO)

[0146] Second exit: bottom fraction (typically comprising some or all of the following: unreacted compound of formula (I); minor side-products; carboxylic acid of formula R3-COOH).

[0147] - Third exit: condensable distillate fraction comprising the terminal alkene (optionally also comprising some or all of carboxylic acid of formula R3-COOH; minor sideproducts).

[0148] The compound of Formula (IV) may be purified by distillation. Distillation will typically be carried out in a distillation column. The overhead temperature may be above, e.g. from 1 to 5 °C above, the boiling point of the compound of Formula (IV). Distillation may remove any by-products with a boiling point less than that of the compound of Formula (IV), e.g. light P383687WO Specification

[0149] 15 components. Recovered light components may be stored and / or purified. Recovered light components may be combusted to provide at least some of the heat energy required for step iii) and / or step (v). The distillation column may comprise a liquid side draw. The liquid side draw may remove compound of Formula (IV), and, optionally, carboxylic acid R3COOH. Unreacted compound of Formula (I) will typically be left at the bottom of the distillation column. It may be that the unreacted compound of Formula (I) is fed back into the flow reactor as a portion of stream (a).

[0150] Distillation may result in a mixture of the compound of Formula (IV) and carboxylic acid R3COOH (e.g. an octene-acetic acid mixture) This mixture may be further treated to remove the carboxylic acid, for example washing with water, aqueous base or distillation at a different pressure (pressure swing distillation) or reactive distillation to convert the acid present, with an alcohol to an ester which is then more easily separable by distillation or any other known means in the art for separating an alkene and an organic acid which may have an azeotropic composition. .

[0151] The terminal alkene (e.g. the compound of Formula (IV)) may subsequently undergo further reactions. It may be that the terminal alkene (e.g. the compound of Formula (IV)) is subsequently dihydroxylated to form the corresponding diol. It may be that the terminal alkene (e.g. the compound of Formula (IV)) is subsequently epoxylated to form the corresponding epoxide. The terminal alkene may take part in a radical polymerisation reaction or in a radical co-polymerisation reaction along with another alkene. The alkene may be reacted with sulfur containing species to produce detergents.

[0152] It may be that the alkene is not purified before undergoing further reactions, e.g. those mentioned above. It may be that the carboxylic acid of formula R3-COOH is still present.

[0153] EXAMPLES

[0154] Example with octyl acetate

[0155] Octyl acetate (>99%) derived from a natural source was purchased commercially. It was fed to a pyrolysis unit under a range of conditions. The unit consisted of a HPLC-type pump, an electrically heated vapouriser (typically operated with a vapourizer exit temperature from 200 to 300°C), and a reactor, mounted vertically, heated in a furnace. The reactor was 500 mL in volume and had two thermocouples located centrally, one at the entrance and one 30cm in from the exit with which to record the temperature. The flanges for the reactor lay outside of P383687WO Specification

[0156] 16 the heated zone. An amount of gas was continuously fed to the system at varying rates. The products were condensed in a catch pot cooled to c. 40 °C and the off-gases (CO2, CO, methane, isl and light alkenes) released to vent.

[0157] A series of experiments were performed under a range of conditions to demonstrate the efficacy of the process as presented in Table 1.

[0158] Table 1

[0159] *Comparative example 1 process stopped due to blockage of reactor

[0160] At the end of some of the runs the amount of carbon residue present was removed by heating the reactor to a higher temperature and removing the carbon residue as carbon monoxide under a flow of CO2. The amount of carbon residue removed could be calculated during this exercise from the flow rate of carbon dioxide and concentration of CO in the CO2 stream. The off gas was measured by an external standard method using a molecular sieve column and an FID detector. CO and CO2 were converted by a methaniser prior to being measured. The results from the reaction both in liquid product analysis and off gas analysis are presented in Table 2.

[0161] Table 2 P383687WO Specification

[0162] 17

[0163] In example 1 a flow of carbon dioxide was introduced to the reactor. This shows that a high selectivity to 1 -octene can be achieved, and that carbon monoxide is produced in the reaction. At the end of the reaction, the feed was stopped, and the reactor was cleaned by flowing just CO2 into the reactor at a higher temperature (600°C). Once the CO concentration had fallen below 0.4 mol%, the reactor was cooled back to the reaction temperature and feed recommenced (Example 2).

[0164] In example 2 a flow of CO2 was introduced to the reactor. The feed of octyl acetate was reduced to 8mls / min, increasing the conversion to 79% vs 46% for example 1. This shows that a high selectivity to 1 -octene can be achieved even at high conversion and carbon monoxide is still produced in the reaction. At the end of the reaction the reactor was cleaned of Carbon residue by stopping the feed and increasing the temperature. Once the CO concentration had fallen below 0.8 mol%, the reactor was cooled back to the room temperature. The reactor was opened for inspection and 2.8g of carbon was found at the bottom of the reactor by the unheated flange. A portion of this material was analysed in a TGA (thermal gravimetric analyser) under a flow of CO2. After 15h at 700 °C, 70% of the mass had been removed.

[0165] In comparative example 1 nitrogen was used instead of CO2 the reaction was run for approximately 100h until the reactor blocked because of carbon residue accumulation. In example 2, under similar conditions but in the presence of Carbon dioxide the reactor was never blocked.

[0166] In comparative example 2, comparative example 1 was repeated at a higher gas rate and for a short period of time to prevent reactor blocking. The off gas was analysed (see Table 3). This demonstrated that no carbon dioxide within the detection limits of the instrument was generated during the reaction. A small amount of carbon monoxide and methane were generated, but much less than in example 2bis which was run at the same conditions under CO2.

[0167] Table 3 P383687WO Specification

[0168] 18

[0169] In examples 4 and 5 the reactor temperature was decreased to 520 °C and increased to 560 °C. These examples demonstrate that the amount of CO and methane produced in the reaction varies with temperature and that the carbon production rate also varies with temperature allowing for an optimization of selectivity, reactor occupancy and productivity with appropriate choice of conditions.

[0170] Example with hexyl acetate

[0171] The same process used for octyl acetate was also used for hexyl acetate.

[0172] A series of experiments were performed under a range of conditions to demonstrate the efficacy of the process as presented in Table 4.

[0173] Table 4

[0174] The results from the reaction both in liquid product analysis and off gas analysis are presented in Table 5. Table 5 P383687WO Specification

[0175] 19

[0176] Example 7 with hexyl acetate demonstrates that the technique is applicable across a range of alkyl carboxylate feedstocks. The wall temperature was increased through the reaction to maintain the exit temperature at 540 °C. Over the course of the experiment, the CO level in off gas increased from 2.8 mol% to 8.4 mol%. The average mass balance over each sample during the reaction averaged 98.9%.

[0177] At the end of the reaction, the hexyl acetate flow was stopped and the CO2 flow increased to 1000mls I min. The CO2 concentration in the exit gas was 2.5 mol% indicating that the comproportionation reaction is observable under these conditions (no methane or other gases were observed in the absence of feed). The CO concentration fell over a period of 6h to 1.59 mol%. The temperature was then increased further to 600°C and the rate of CO production increased back to 2.36 mol%. At the end of the run the reactor was cooled and 8.9 g of carbon was recovered from the end of the reactor located outside of the heated zone.

[0178] In example 8 with hexyl acetate, the furnace temperature was fixed throughout the experiment and the reactor exit temperature allowed to fall throughout the reaction as carbon built upon the walls of the reactor. The unit ran for 115h at this time the reactor exit temperature had stabilized at approximately 525°C and the conversion at 48%, where it remained for the rest of the experiment. At the end of the experiment, the feed was stopped and the reactor heated to 600°C to remove the carbon residue produced in the reaction at a CO2 flow rate of 1000 mls / min. A peak CO concentration of 4 mol% was observed.

Claims

P383687WO Specification20CLAIMSClaim 1A process for the continuous production of a terminal alkene having 4 to 20 carbon atoms comprising the steps (i), (ii), (iii), (iv) and optionally (v):(i) feeding a flow reactor with a stream (a) comprising a compound of formula (I)wherein:- X is independently C2-is-alkyl;R3is independently selected from H, and Ci-6-alkyl optionally substituted with from 1 to 9 halo groups;(ii) feeding the flow reactor with a stream (b) comprising carbon dioxide (CO2),(iii) heating stream (a) and stream (b), if present, in a heating part of the flow reactor at a temperature in the range from 400 to 600°C to convert the compound of formula (I) into the corresponding terminal alkene to provide a product stream (c) comprising the terminal alkene,(iv) recovering product stream (c),(v) optionally heating stream (b) in the heating part of the flow reactor at a temperature in the range from 400 to 900°C; wherein the process is carried out such that stream (b) is heated in the heating part of the flow reactor during either step (iii) or step (v) or both.Claim 2The process according to claim 1 , wherein in step (iii) stream (a), and optionally stream (b), are heating to a temperature in the range from 500 to 580°C; optionally a temperature in the range from 520 to 560°C.Claim 3P383687WO Specification21The process according to claim 1, wherein at least a portion of step (ii) and at least a portion of step (i) are performed at the same time and both stream (a) and stream (b) are heated in the heating part of the flow reactor.Claim 4The process according to claim 3, wherein the process does not comprise step (v).Claim 5The process according to claim 3, wherein the process does comprise step (v).Claim 6The process according to claim 1 or claim 2, wherein the process comprises step (v).Claim 7The process according to claim 6, wherein no portion of step (ii) is performed at the same time as any portion of step (i).Claim 8The process according to any one of claims 5 to 7, wherein in step (v), stream (b) is heated to a temperature in the range from 650 to 800°C; optionally a temperature in the range from 700 to 750°C.Claim 9The process according to any one of claims 1 to 8, wherein stream (b) is fed into the flow reactor at a flow rate such that the CO2 / CO ratio in stream (c) is higher than 1, optionally wherein the ratio is higher than 3; further optionally wherein the ration is higher than 5.Claim 10P383687WO Specification22The process according to any one of claims 1 to 9, wherein product stream (c) comprises the terminal alkene in an amount from 50 to 80 wt. % by total weight of stream (c); optionally from 55% to 75 wt. %.Claim 11The process according to any one of claims 1 to 10, wherein R3is unsubstituted Ci-3-alkyl; optionally wherein R3is methyl.Claim 12The process according to any one of claims 1 to 11 , wherein X is n-C2-i2-alkyl.Claim 13The process according to any one of claims 1 to 10, wherein the compound of formula (I) is decyl acetate.Claim 14The process according to any one of claims 1 to 10, wherein the compound of formula (I) is octyl acetate.Claim 15The process according to any one of claims 1 to 10, wherein the compound of formula (I) is heptyl acetate.Claim 16The process according to any one of claims 1 to 10, wherein the compound of formula (I) is hexyl acetate.Claim 17The process according to any one of claims 1 to 16, wherein the terminal alkene is subsequently di hydroxylated to form the corresponding diol.Claim 18The process according to any one of claims 1 to 16, wherein the terminal alkene is subsequently epoxylated to form the corresponding epoxide.P383687WO Specification23Claim 19A terminal alkene having a structure according to formula (IV):wherein X is independently C2-is-alkyl; wherein the terminal alkene is obtainable according to the method of any one of claims 1 to 16.

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