Process for preparing 2-methyltetrahydrofuran

Abstract

Process for the preparation of 2-methyltetrahydrofuran. The present invention relates to a process for the preparation of 2-methyltetrahydrofuran comprising a step b) of reacting 2-methylfuran in the presence of hydrogen and a catalyst comprising nickel supported on alumina comprising from 5 to 22% by weight of nickel relative to the total weight of the catalyst, thereby forming 2-methyltetrahydrofuran. Figure for the abstract: None

Description

Title of the invention: Process for preparing 2-methyltetrahydrofuran

[0001] The present invention relates to a process for preparing 2-methyltetrahydrofuran from 2-methylfuran in the presence of hydrogen and a catalyst comprising nickel supported on alumina.

[0002] 2-Methyltetrahydrofuran, also known as MeTHF, is widely used as a solvent in organic chemistry. It is notably proposed as an alternative to tetrahydrofuran, dichloromethane, or hexane. It is also used in the formulation of lithium battery electrolytes and in alternative fuels. It has the advantage of being produced from biomass, particularly from furfural. In theory, the reduction of furfural in the presence of hydrogen and a catalyst would allow access to 2-methyltetrahydrofuran via furfurol and 2-methylfuran as intermediates. In reality, this hydrogenation / hydrogenolysis sequence cannot occur with a single catalyst with high productivity.It is common practice to first transform furfural into 2-methylfuran or furfurol in the presence of a first catalyst and then, in a second step, to transform 2-methylfuran or furfurol into 2-methyltetrahydrofuran in the presence of a second catalyst.

[0003] The hydrogenation of 2-methylfuran in the presence of a catalyst can lead to 2-methyltetrahydrofuran, but also to other products such as 1-pentanol, 2-pentanol, or pentane. Therefore, a catalyst is sought that provides not only good conversions but also good selectivity.

[0004] Many metals have been tested to catalyze the hydrogenation reaction of 2-methylfuran to 2-methyltetrahydrofuran, including Pd and Ni. Nickel has the advantage of being less expensive than palladium, but its efficiency (conversion / selectivity) is generally lower.

[0005] For efficient industrial implementation (easy and economical), it is necessary to use a catalyst allowing high conversion of 2-methylfuran and maximum selectivity in 2-methyltetrahydrofuran.

[0006] Furthermore, this catalyst must be robust under the reaction conditions.

[0007] One of the aims of the invention is to provide a catalyst for transforming 2-methylfuran into 2-methyltetrahydrofuran which has the aforementioned advantages.

[0008] Another object of the invention is to provide a process for preparing 2-methyltetrahydrofuran from 2-methylfuran.

[0009] Another object of the invention is to provide a process for preparing 2-methyltetrahydrofuran from furfural.

[0010] To this end, the invention has as its first object a process for preparing 2-methyltetrahydrofuran comprising a step b) of reacting 2-methylfuran in the presence of hydrogen and a catalyst comprising nickel supported on alumina comprising from 5 to 22% by weight of nickel relative to the total weight of the catalyst, by which 2-methyltetrahydrofuran is formed.

[0011] The process of the invention is advantageously easy to implement, selective in 2-methyltetrahydrofuran, economical, industrially viable and allows to obtain a high, or even total, conversion of 2-methylfuran.

[0012] Preferably, step b) is carried out in the gas phase.

[0013] By "gas phase" or "gaseous phase" it is understood that the hydrogen and the 2-methylfuran are in the gaseous state under the temperature and pressure conditions of reaction b). The process typically includes, before step b), a step of vaporizing the 2-methylfuran.

[0014] On the other hand, the catalyst remains in solid form during reaction b). Typically, the catalyst is a heterogeneous catalyst.

[0015] The process then employs heterogeneous gas-phase catalysis, which is preferred at the industrial level. It has the advantage of not using a solvent and therefore avoids the costs of solvent recycling and / or used solvent treatment. Furthermore, a gas-phase process is generally more productive than a liquid-phase process, and therefore more economical.

[0016] Catalyst for step b) of hydrogenation of 2-methylfuran

[0017] The process uses a catalyst comprising nickel supported on alumina (Ni / Al2O3). The nickel can be in the form of metal (Ni), nickel oxide, or a mixture of these.

[0018] The amount of nickel in the catalyst is between 5 and 22% by weight, in particular between 7 and 20% by weight, especially between 8 and 18%, preferably between 10 and 17% by weight relative to the weight of the catalyst. These amounts allow for the best compromise between conversion and selectivity.

[0019] The catalyst can be prepared by impregnating nickel salt (nickel nitrate or nickel acetate for example) onto alumina and then reducing it to form nickel.

[0020] Such catalysts and their production are accessible to those skilled in the art. For example, see Chang et al. “Reductive amination of polypropylene glycol using Ni-CeO2@A12O3 with high activity, selectivity and stability”, Catalysis Communications, vol 127, 2019, p. 15-19, or Gavrilovié et al. “Ni alumina-based catalyst for sorption enhanced reforming - Effect of calcination temperature”, Catalysis Communications, Vol 185, 2023, p. 106800.

[0021] The catalyst preferably has a specific surface area greater than or equal to 70 m2 / g as measured by BET and / or an average particle size as measured by dynamic light scattering (DLS) preferably of 0.1 to 10 mm.

[0022] The hydrogenation catalysts described above allow for a high or even complete conversion of 2-methylfuran, which is particularly advantageous because 2-methylfuran and 2-methyltetrahydrofuran are difficult to separate due to their similar boiling points (64°C and 78°C, respectively). This complete conversion thus facilitates the purification of 2-methyltetrahydrofuran.

[0023] The catalyst is preferably used in the form of a tablet, bead or extrudate.

[0024] Possible activation of the hydrogenation catalyst b)

[0025] The process may include, before hydrogenation b), a step of activating the hydrogenation catalyst.

[0026] Indeed, the hydrogenation catalyst is generally supplied in at least a partially oxidized form. Activation of the hydrogenation catalyst is typically a reduction of the catalyst. Activation can take place in the reactor in which step b) of the hydrogenation of 2-methylfuran will be carried out (in situ activation) or in another reactor. Preferably, once activated, the hydrogenation catalyst is stored in wet form or in an organic solvent, for example in an alcohol, before use in step b). Activation of the catalyst is carried out by conventional methods, well known to those skilled in the art. For example, the catalyst can be activated in a reducing atmosphere, in particular in a hydrogen stream at a temperature ranging from 100°C to 250°C, for example from 120°C to 200°C.

[0027] Reaction conditions for the hydrogenation b) of 2-methylfuran

[0028] The hydrogenation of 2-methylfuran to 2-methyltetrahydrofuran takes place in the presence of hydrogen and generally a catalyst, preferably as described above.

[0029] Preferably, it takes place in the gas phase.

[0030] Reaction b) is generally carried out continuously.

[0031] Hydrogenation preferably takes place under pressure, preferably from 1.05 bara to 15 bara, in particular from 1.1 bara to 12 bara, preferably from 1.2 bara to 10 bara (it being understood that when hydrogenation b) is in the gas phase, the temperature is adjusted so that it is in the gas phase).

[0032] The hydrogen / 2-methylfuran molar ratio is preferably from 2 to 25, preferably from 3 to 20, more preferably from 5 to 18.

[0033] Hydrogenation can be carried out at a temperature between 110 and 170°C, in particular between 115°C and 160°C, preferably between 120°C and 155°C (it being understood that when hydrogenation b) is in the gas phase, the pressure is adjusted so that it is in the gas phase).

[0034] The weight hourly space velocity of 2-methylfurfural (WHSV “Weight Hourly Space Velocity”), corresponding to the mass of 2-methylfuran passing in Ih on the mass of catalyst used can be from 0.2 to 1.5 h1, preferably from 0.3 to 1.0 h1.

[0035] Installation for the implementation of hydrogenation b)

[0036] Hydrogenation is generally implemented through one or more fixed beds of hydrogenation catalyst. Each fixed bed may comprise one or more layers of catalyst. In the case of implementing a catalytic bed comprising several layers of catalyst, the concentration of hydrogenation catalyst may increase from the inlet to the outlet of the reactor, the number of layers varying according to the length of the catalytic bed, and the catalyst may be diluted in an inert material (glass, quartz, ceramic, for example).

[0037] Hydrogenation can be carried out within one or more tubular or multitubular reactors in series or in parallel.

[0038] The reactor temperature can be maintained by means of a heat transfer fluid which can be heated by steam, electrically or by any other known means and which can be cooled by means of a water and / or ethylene glycol refrigeration circuit or any other known refrigeration fluid. Purification of 2-methyltetrahydrofuran

[0039] The process may include, after step b), a 2-methyltetrahydrofuran recovery step and / or a 2-methyltetrahydrofuran purification step, which is generally carried out by distillation.

[0040] The process for preparing 2-methyltetrahydrofuran may include, before step b), a step a) of preparing 2-methylfuran by reacting furfural in the presence of hydrogen.

[0041] The embodiments described above for step b) of preparation of 2-methyltetrahydrofuran by reaction of 2-methylfuran are of course applicable.

[0042] Step a) of reacting furfural to form 2-methylfuran can be carried out by any known method, in gas phase or in liquid phase. Furfural

[0043] Furfural preferably has an acid value of less than 7 mmol / kg, and in particular less than 5 mmol / kg. Such acid values ​​improve the longevity of the catalyst. The acid value of furfural can, for example, be measured as follows: 200 mL of deionized water are introduced into an Erlenmeyer flask and stirred. A pH probe is The sample is immersed in this water and, once stabilized, the initial pH is recorded. 7.00 g of furfural are then added. The resulting solution is stirred until the pH stabilizes, and then a 0.01 M NaOH solution in water is gradually added until the pH returns to the initial level. The amount of NaOH solution required allows us to calculate the quantity in mmol of NaOH needed to neutralize 1 kg of furfural.

[0044] To achieve this acid value, furfural can be purified by distillation, or its acid value can be reduced by acid absorption in the presence of an adsorbent, typically basic solids or basic resins. Thus, the process may include, prior to step a), a step for reducing the acid value of furfural, for example by distillation, to an acid value of less than 7 mmol / kg. Catalyst

[0045] Generally, step a) is carried out in the presence of a catalyst. For example, step a) of the furfural reaction can be carried out in the presence of a copper-based catalyst.

[0046] Many metals have been tested to catalyze the reduction reaction of furfural to 2-methylfuran: Pd, Ru, Ni, or Cu. Copper has the advantage of being less expensive than palladium or ruthenium. Among the copper-based catalysts used in this reaction, the Adkins catalyst is the reference catalyst (Chem. Rev. 2018, 118, 11023-11117). It is a copper chromite-type catalyst.

[0047] However, the toxicity of chromium, particularly in its chromium VI form, necessitates increasingly strict regulations on its use. It is therefore advantageous to find a chromium-free alternative to this catalyst at the industrial level.

[0048] In a preferred embodiment, step a) implements a catalyst comprising copper, aluminum, and a transition metal selected from zirconium, manganese, and a mixture thereof, preferably zirconium. In other words, step a) then implements a catalyst comprising copper, aluminum, and zirconium (Cu-Al-Zr catalyst), a catalyst comprising copper, aluminum, and manganese (Cu-Al-Mn catalyst), a catalyst comprising copper, aluminum, zirconium, and manganese (Cu-Al-Zr-Mn catalyst), or a mixture thereof.

[0049] Reaction a) involves hydrogenation, by which furfural is converted to furfurol, followed by hydrogenolysis, by which furfurol is converted to 2-methylfuran. Reaction a) therefore corresponds to hydrogenation followed by hydrogenolysis. This preferred mode is based on the discovery that a copper-aluminum catalyst further containing zirconium and / or manganese is capable of simultaneously hydrogenating furfural and then hydrogenolyzing the intermediate furfurol formed to produce 2-methylfuran, which is surprising because catalysts Hydrogenation agents are not necessarily capable of undergoing hydrogenolysis, and vice versa. It is important to remember that hydrogenation involves the addition of a dihydrogen molecule (H2) to another compound without breaking a covalent bond, whereas hydrogenolysis is a chemical reaction in which a carbon-heteroatom covalent bond is broken or lysed by the action of hydrogen. Thus, the hydrogenation of furfural leads to furfurol, not 2-methylfuran.

[0050] In step a), hydrogenolysis immediately follows hydrogenation, and furfurol (the intermediate product) is generally not isolated. The reaction a) of furfural to form 2-methylfuran is therefore carried out in a single step. Generally, the process does not employ any hydrogenolysis catalyst other than the aforementioned catalyst. Typically, reaction a) (and generally the process as a whole) is not carried out in the presence of a Pd, Ru, and / or Ni-based catalyst.

[0051] During step a), various side reactions can occur, including the decarbonylation of furfural to furan, which leads to the generation of carbon monoxide. Advantageously, the performance of such a catalyst is not affected in the presence of carbon monoxide, and this catalyst minimizes decarbonylation.

[0052] Preferably, the catalyst does not comprise chromium, nickel, palladium, ruthenium, or a mixture thereof. Generally, reaction a) of the process is not carried out in the presence of Cr, Ni, Pd, Ru, Ni, or a mixture thereof.

[0053] Preferably, the transition metal is zirconium. Alternatively, the transition metal is manganese.

[0054] The catalyst may also include one or more other additives such as stabilizers and / or shaping aids such as lubricants or binders. The lubricants may be graphite, oils, or stearates. The binders may be aluminum oxide, silica, calcium aluminate, calcium silicate, or clay minerals.

[0055] In a particular embodiment, the catalyst consists of copper, aluminum, and a transition metal selected from zirconium and manganese (where the copper, aluminum, zirconium, and manganese may be in the form of metal or metal oxide or a mixture of metal and metal oxide), and optionally one or more additives, in particular as defined above. This / these additive(s) is / are generally free of transition metal(s), or even of metal other than calcium or aluminum (in any form: metal, metal salt, metal oxide).

[0056] The catalyst is preferably used in the form of a tablet (“tablet” or “pellet” in English).

[0057] The quantities by weight of metal within the catalyst described below are understood to be in relation to the weight of the catalyst after calcination (which is one of the steps to prepare it, as described below).

[0058] The amount of copper in the catalyst is preferably less than or equal to 60% by weight, relative to the weight of the catalyst. In particular, the amount of copper is from 15% to 60% by weight, especially from 20% to 55% by weight, preferably from 25% to 50% by weight, and particularly preferably from 28% to 47% by weight, relative to the weight of the catalyst.

[0059] The amount of aluminium in the catalyst is preferably between 8% and 29% by weight, in particular between 15% and 25% by weight, especially between 16% and 21% by weight relative to the weight of the catalyst.

[0060] The quantity of transition metal in the catalyst is preferably from 0.5 to 30% by weight, in particular from 2 to 25% by weight, more particularly from 4 to 20% by weight, especially from 5 to 19% relative to the weight of the catalyst.

[0061] When the transition metal is zirconium, the amount of zirconium is preferably from 0.5 to 30% by weight, in particular from 5 to 20% by weight, more particularly from 10 to 20% by weight, especially from 16 to 19% by weight relative to the weight of the catalyst.

[0062] When the transition metal is manganese, the amount of manganese is preferably from 0.5 to 20% by weight, in particular from 2 to 15% by weight, more particularly from 4 to 10% by weight, especially from 5 to 8% by weight relative to the weight of the catalyst.

[0063] Generally, the additive(s) are in a quantity of 0.5% to 30% by weight, in particular 1% to 10% by weight relative to the weight of the catalyst, it being understood that when there are several additives, the quantity of additives is the cumulative quantity of these.

[0064] The quantities of metals and additive(s) described above are particularly suitable so that the catalyst allows reaction a) of the process to have a high conversion and to be selective.

[0065] Within the catalyst, copper may be present in the form of copper (Cu), copper oxide, in particular in the form of CuO, or a mixture of these.

[0066] Within the catalyst, aluminium may be present in the form of aluminium (Al), aluminium oxide, in particular in the form of A12O3, or a mixture of these.

[0067] Within the catalyst, the transition metal may be present as the metal, as a metal oxide, or as a mixture thereof. Typically, manganese may be present as the metal (Mn), as an oxide, preferably as manganese dioxide MnO2 or Mn3O4, or as a mixture of metal and oxide. Similarly, the zirconium can be present in the form of metal (Zr), oxide, notably in the form of ZrO2, or mixtures of these.

[0068] Copper and the transition metal are typically at least partially in oxide form before catalyst activation. By "at least partially in oxide form," it is meant that some or all of the metal is in oxide form (or a mixture of oxides).

[0069] These catalysts can be prepared by mixing an aqueous solution comprising a copper salt, an aluminum salt, and a salt of a transition metal selected from zirconium, manganese, and a mixture thereof, with an alkaline aqueous solution, in particular a carbonate salt solution, thereby forming a precipitate, which is then calcined. The processes described in US applications 2018 / 0297015 or 2022 / 0401928 can, for example, be used. Thus, the process may include, prior to step a), a catalyst preparation step a0).

[0070] These catalysts are also commercially available. For example, the HySat™ 200 (Cu-Mn-Al) and Hysat™ 320 (Cu-Al-Zr) catalysts from Clariant can be used.

[0071] Catalysts can be in various oxidized forms. It may be necessary to activate them by contacting them with a reducing agent before use. Indeed, the reduced form of the catalyst is the active form.

[0072] Typically, catalysts are marketed in two forms:

[0073] - solid catalysts which are generally at least partially oxidized and therefore which it is best to activate before use,

[0074] - catalysts dispersed in a liquid (generally in a heavy alcohol). In this In this case, the catalyst is usually already in reduced, and therefore active, form, and it is not necessary to activate it by reduction before use.

[0075] Thus, the process may include, prior to reaction a), the steps of:

[0076] a) supplying a catalyst comprising copper, aluminum and a transition metal selected from zirconium and manganese, said catalyst being in at least a partially oxidized form,

[0077] a2) activation of the catalyst in a form at least partially oxidized by reduction with a reducing agent, preferably with hydrogen.

[0078] Step a2) leads to the reduction of the catalyst into a form at least partially oxidized to form the catalyst in reduced and active form, and thus to the activation of the catalyst.

[0079] Preferably, the reducing agent used is hydrogen, which allows the catalyst activation step to be carried out "in situ," that is, the catalyst activation by contact with hydrogen is carried out in the same reactor as that used for reaction a) of furfural. Alternatively, activation can take place in another reactor. The activated catalyst is then preferably kept in wet form or dispersed in a solvent, for example in an organic solvent, before use in step a), to prevent it from oxidizing again.

[0080] The activation a2) of the catalyst is carried out by conventional methods, well known to those skilled in the art. For example, the activation a2) of the catalyst can be carried out in a reducing atmosphere, in particular in a hydrogen stream at a temperature between 150°C and 450°C, for example from 160°C to 350°C, preferably from 170°C to 300°C. reaction conditions a)

[0081] Reaction a), or even the process as a whole, is generally carried out continuously.

[0082] Reaction a) of the process according to the invention is carried out under pressure, preferably from 1.05 bara to 10 bara, in particular from 1.1 bara to 5 bara, where bara is the unit of absolute pressure (it being understood that when reaction a) is in the gas phase, the temperature is adjusted so that it is in the gas phase).

[0083] During step a) of the process, the molar ratio of hydrogen to furfural is generally from 2 to 10, preferably from 2 to 8, more preferably from 2.5 to 7, particularly preferably from 2.5 to 5.

[0084] Reaction a) of the process can be carried out at a temperature between 150 and 240°C, in particular between 190°C and 240°C, preferably between 200°C and 238°C, and more preferably between 210°C and 235°C (it being understood that when reaction a) is in the gas phase, the pressure is adjusted to ensure that it is in the gas phase). A temperature below 150°C can lead to a decrease in the conversion of reaction a) from furfural to 2-methylfuran. The formation of furfurol (an intermediate product) can then be observed, suggesting that it is the conversion of the hydrogenolysis of furfurol to 2-methylfuran that decreases when the temperature is too low. A temperature above 240°C can lead to a drop in selectivity with the formation of by-products such as furan (resulting from decarbonylation). Selectivity refers to the molar ratio between the amount of 2-methylfuran formed and the amount of furfural introduced.

[0085] The weight hourly space velocity (WHSV) of furfural, corresponding to the mass of furfural passing in Ih over the mass of catalyst used, can be from 0.2 to 1.5 h', preferably from 0.3 to 0.8 h'. The lower the WHSV, the longer the residence time of the furfural on the catalyst (and therefore the lower the productivity for a given quantity of catalyst), and vice versa. Lowering the temperature generally requires increasing the WHSV. Purification of 2-methylfuran

[0086] The 2-methylfuran obtained at the end of reaction a) is mixed with water formed by the reaction.

[0087] The process may include, after reaction a), the purification of the 2-methylfuran obtained, typically by distillation possibly preceded by decantation to remove water.

[0088] Installation for implementing reaction a)

[0089] Reaction a) can be carried out by passing the gaseous mixture comprising furfural and hydrogen through one or more fixed beds of catalyst. The fixed beds can comprise one or more layers of catalyst. In the case of a catalytic bed comprising several layers of catalyst, the metal concentration (for example, Cu) can increase from the inlet to the outlet of the reactor, the number of layers varying according to the length of the catalytic bed. The catalyst can be diluted in an inert material (glass, quartz, ceramic).

[0090] Reaction a) can be carried out in one or more tubular or multitubular reactors in series or in parallel.

[0091] The reactor temperature can be maintained by means of a heat transfer fluid which can be heated by steam, electrically or by any other known means and which can be cooled by means of a water and / or ethylene glycol refrigeration circuit or any other known refrigeration fluid.

[0092] The gas-phase reactor can be fed by first passing the furfural, initially in liquid form, through an evaporator (for example, one heated by steam or any other known means). The evaporator temperature is set to ensure that the furfural changes from a liquid to a gaseous state under the operating pressure conditions. The resulting gaseous furfural can then be drawn towards the reactor inlet, for example with the hydrogen stream, and brought into contact with the catalyst.

[0093] According to a second object, the invention relates to the use of a catalyst comprising nickel supported on alumina comprising 5 to 22% by weight of nickel relative to the total weight of the catalyst for the preparation of 2-methyltetrahydrofuran from 2-methylfuran.

[0094] The embodiments described above for the first object are of course applicable.

[0095] The following examples illustrate the invention. EXAMPLES

[0096] Example 1 - step a): Preparation of 2-methylfuran from furfural

[0097] Reaction a) for the preparation of 2-methylfuran from furfural was carried out in the presence of various catalysts, the composition of which is given in Table 1.

[0098] [Tables 1] Catalyst Main elements Chemical composition after calcination (% by weight) CuCr (HyMax220 Clariant) Cu: 37.5 Cr: 31.5 CuAlMn (HySat200 Clariant) Cu: 45 Al: 18 Mn: 6.5 CuAlZr (HySat320 Clariant) Cu: 29.5 Al: 20 Zr: 17.5 CuZn (HySat350 Clariant) Cu: 26 Zn: 53.5

[0099] Table 1: Chemical composition of the catalysts after calcination (mass %)

[0100] A double-jacketed tubular reactor was filled with 50.2 g of dry catalyst and heated with a ramp of 2 °C / min under a flow of 45 NL / h of argon to 190 °C. The argon flow was stopped and the reactor was placed under a hydrogen flow (flow rate: 45 NL / h). Furfural was then introduced at a flow rate of 0.39 mL / min.

[0101] The start of the tests is counted from the stabilization of temperatures inside the reactor. Each sample was taken after at least 45 minutes of stable conditions.

[0102] Table 2 below provides the compositions of the samples taken, in particular the mass yields of 2-methylfuran (RR MeF), determined by GC-FID (Shimadzy GC-FID 2010 pro) in methanol as solvent and n-nonane as external standard as a function of the temperature during the reaction, the nature of the catalyst, the H2 / furfural molar ratio and the WHSV.

[0103] The identified by-products are methyltetrahydrofuran, gama-valerolactone, 2-pentanone, 1-pentanol and 2-pentanol.

[0104] Other unidentified compounds are present according to the equation: TT-SRR measured. They are not visible in GC-FID, because they are heavy compounds or degradation compounds.

[0105] [Tables2] Cat P (bara) (°C) WHSV (h') Ratio H2 / fu rfural TT furf ural RR Me F RR furfu roi RR secondary products i identified CuCr 1.2 225 0.7 3 >99 92 3 1 CuCr 1.2 225 0.5 3 >99 92 3 1 CuAlMn 1.2 235 0.5 3 >99 87 2 8 CuAlMn 1.2 225 0.5 3 >99 84 3 8 CuAlZr 1.2 225 0.7 3 >99 89 2 8 CuAlZr 1.2 225 0.5 3 >99 84 2 9 CuZn 1.2 235 0.5 7 >99 82 1 8 CuZn 1.2 225 0.5 5 >99 79 2 7

[0106] RR = yield on reactant

[0107] TT = transformation rate

[0108] Table 2: Yields of 2-methylfuran and by-products on the quantity of furfural committed and determined by GC FID %vs standard under optimized conditions

[0109] With the CuZn catalyst, the maximum yield under optimized conditions (82%) was lower than those obtained with the other catalysts (87% or more).

[0110] With CuCr as the catalyst, making the reaction conditions harsher by increasing the WHSV did not alter the results (neither the conversion rate nor the yields obtained). However, using CuAlMn or CuAlZr as the catalyst, making the reaction conditions harsher by increasing the WHSV improves the yield of 2-methylfuran.

[0111] The 2-methylfuran produced in these examples can be used to prepare 2-methyltetrahydrofuran as described in Example 2 below.

[0112] Evolution of catalyst performance in the presence of CO

[0113] During step a), traces of furan are observed. The furan is formed by Decarbonylation of furfural. This decarbonylation leads to the release of carbon monoxide. On an industrial scale, excess hydrogen can be recycled, which would also lead to an accumulation of carbon monoxide. It is therefore necessary to ensure that the chosen catalyst generates very little CO and is not affected by the presence of CO.

[0114] To determine the resistance of the catalysts to CO, tests were carried out by incorporating 5% v / v of CO into the hydrogen stream. The performance obtained was compared to a reference test performed before the addition of CO and to a return point performed after the passage of CO.

[0115] With the CuCr catalyst, a 3% decrease in 2-methylfuran yield and a 2% increase in furfurol yield are observed within the first hour under 5% v / v CO. The initial performance is therefore not recovered after the CO introduction is stopped. The compatibility of the CuCr catalyst with carbon monoxide is therefore insufficient for industrial use.

[0116] With the CuAlZr catalyst, the presence of 5%v / v CO in the gas stream did not have a significant influence on the observed performance, which was similar before, during, and after the passage of CO. CuMnAl also maintains performance even in the presence of CO.

[0117] Example 2: step b): Preparation of 2-methyltetrahydrofuran from 2-methylfuran

[0118] A double-jacketed tubular reactor was filled with 20.8 g of catalyst and placed under 30 NL / h of argon at 20°C for 15 minutes under 1.5 bar. The argon flow was then stopped and replaced with 65 NL / h of hydrogen. The reactor was then heated with a ramp of 6 °C / min up to 100°C. 2-Methylfuran was then introduced at a flow rate of 0.4 mL / min.

[0119] The start of the tests is counted from the stabilization of temperatures inside the reactor. Each sample was taken after at least 30 minutes of stable conditions.

[0120] With this process, depending on the catalysts, the pressure, temperature, hourly spatial velocity, weight of 2-methylfuran, and H2 / 2-methylfuran ratio conditions were optimized to obtain the highest possible conversion to 2-methylTHF. The optimized conditions and the composition of each catalyst are shown in Table 3.

[0121] Table 3 below provides the compositions of the samples taken, in particular the mass yields of 2-methyltetrahydrofuran (RR MeTHF), determined by GC-FID (Shimadzy GC-FID 2010 pro) in methanol as solvent and n-nonane as external standard as a function of the temperature during the reaction, the nature of the catalyst, the molar ratio H2 / MeF (2-methylfuran) and the WHSV.

[0122] The identified by-products are 2-pentanone, 2-pentanol, 1-pentanol and n-pentane.

[0123] Other unidentified compounds are present according to the equation: TT-SRR measured. They are not visible by GC-FID, because they are heavy compounds or degradation compounds.

[0124] [Tables3] Catalyst P (bara) 'T'O J- avg (°C) WHSV (h') Ratio H2 / MeF TT MeF RR MeT HF RR secondary products i identified Ni / Al2O3 60% Ni (comp.) 1.5 110 1.0 10 91 8 7 Ni / Al2O3 25-30%Ni (comp.) 1.5 108 1.0 10 93 70 13 Ni / Al2O3 10%Ni (inv.) 1.5 110 1.0 10 71 63 2 Ni / Al2O3 60% Ni (comp.) 1.5 105 0.5 20 91 76 7 Ni / Al2O3 25-30%Ni (comp.) 1.5 106 0.5 10 >99 85 9 Ni / Al2O3-SiO2 52%Ni (comp.) 1.5 107 0.5 10 73 63 2 Ni / Al2O3-SiO2 52%Ni (comp.) 1.5 127 0.5 10 95 82 6 Ni / Al2O3 10%Ni (inv.) 1.5 130 0.5 10 98 91 7 Ni / Al2O3 14-18% Ni (inv.) 1.5 128 0.5 10 95 90 3 Ni / Al2O3 10%Ni (inv.) 1.5 118 0.5 10 99 93 4 Ni / Al2O3 5 123 0.5 10 >99 88 9 14%Ni (inv.) Ni / Al2O3 14-18% Ni (inv.) 5 125 0.5 10 >99 97 2

[0125] TT = transformation rate

[0126] Table 3: Yields of 2-methyltetrahydrofuran and by-products under optimized conditions

Claims

Demands

1. Process for preparing 2-methyltetrahydrofuran comprising a step b) of hydrogenating 2-methylfuran in the presence of hydrogen and a catalyst comprising nickel supported on alumina comprising from 5 to 22% by weight of nickel relative to the total weight of the catalyst, by which 2-methyltetrahydrofuran is formed.

2. A process for preparing 2-methyltetrahydrofuran according to claim 1, wherein step b) takes place in the gas phase.

3. A process for preparing 2-methyltetrahydrofuran according to claim 1 or 2, wherein the amount of nickel in the catalyst is 7 to 20% by weight, relative to the total weight of the catalyst.

4. A process for preparing 2-methyltetrahydrofuran according to any one of the preceding claims, wherein step b) takes place at a temperature of 110°C to 170°C.

5. A process for preparing 2-methyltetrahydrofuran according to any one of the preceding claims, wherein the molar ratio of hydrogen to 2-methylfuran is 2 to 25.

6. A process for preparing 2-methyltetrahydrofuran according to any one of the preceding claims, wherein the hydrogenation takes place under a pressure of 1.1 bar to 12 bar

7. A process for preparing 2-methyltetrahydrofuran according to any one of the preceding claims comprising, before step b), a step a) of preparing 2-methylfuran by reacting furfural in the presence of hydrogen.

8. A process for preparing 2-methyltetrahydrofuran according to claim 7, wherein step a) is carried out in the presence of a catalyst comprising copper, aluminum and a transition metal selected from zirconium, manganese, and a mixture thereof, preferably zirconium.

9. A process for preparing 2-methyltetrahydrofuran according to claim 8, wherein: the amount of copper in the catalyst of step a) is 15 to 55% by weight, relative to the total weight of the catalyst, and / or the amount of aluminum in the catalyst of step a) is 8% to 29% by weight, relative to the total weight of the catalyst, and / or 17 the amount of transition metal in the catalyst of step a) is 0.5% to 30% by weight, relative to the total weight of the catalyst.

10. A method according to any one of claims 7 to 9, wherein step a) takes place at a temperature from 150°C to 240°C.