Process for producing 2-methylfuran

Abstract

The present invention relates to a process for preparing 2-methylfuran, comprising a step a) of reacting furfural in the presence of hydrogen and a catalyst comprising copper, aluminum and a transition metal chosen from zirconium, manganese, and a mixture thereof, whereby 2-methylfuran is formed, and to a process for preparing 2-methyltetrahydrofuran from furfural, comprising said step a) and a step b) of hydrogenation of the 2-methylfuran obtained in step a) in the presence of hydrogen, whereby 2-methyltetrahydrofuran is formed.

Description

[0001] TITLE: Process for the preparation of 2-methylfuran

[0002] The present invention relates to a process for preparing 2-methylfuran from furfural, also called 2-furfuraldehyde, in the presence of hydrogen and a Cu-Al catalyst containing zirconium and / or manganese.

[0003] Biomass can be transformed into a wide variety of products of industrial interest. In particular, furfural, derived from biomass, is a platform compound providing access to numerous products of interest such as furfurol, 2-methyltetrahydrofuran, or pentanediol isomers.

[0004] The transformation of furfural in the presence of hydrogen and a catalyst presents a challenge in terms of selectivity. Indeed, furfural exhibits various reactive sites, such as the carbonyl group at position 2, which can lead to hydrogenation, hydrogenolysis, or decarbonylation. The C-O bonds of the aromatic ring are also susceptible to hydrogenolysis, as is the aromatic ring itself, which can be dearomatized.

[0005] US patent application 2018 / 0297015 describes the use of Cu-Al catalysts and a transition metal for the hydrogenation of organic compounds containing a carbonyl group. In the examples, methyl laurate was converted to the corresponding alcohol. The use of the catalyst for the hydrogenation of other compounds, including aldehydes such as furfural, is also envisaged.

[0006] US patent application 2022 / 0401928 describes the use of a Cu-Al-Zr catalyst for the hydrogenation of compounds with a carbonyl group, specifically aldehydes, to alcohols. In the examples, methyl laurate was converted to the corresponding alcohol, and oxoaldehydes were converted to oxoalcohols.

[0007] 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 undergoes lysis by the action of hydrogen. Thus, the hydrogenation of furfural yields furfurol, not 2-methylfuran.

[0008] Numerous metals have been tested to catalyze the reduction 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. However, the toxicity of chromium, particularly in its chromium VI form, necessitates increasingly strict regulations on its use. It is therefore essential to find a chromium-free alternative to this catalyst at the industrial level.

[0009] For efficient industrial implementation (easy and economical), it is necessary to use a catalyst allowing high conversion of furfural and maximum selectivity in 2-methylfuran.

[0010] Furthermore, this catalyst must be robust under the reaction conditions. Commercial furfural contains impurities, including some acidic ones, which can negatively affect the catalyst, such as deactivating it. Therefore, the catalyst must be resistant to an acidic environment. Under the reaction conditions, carbon monoxide can also be formed as a byproduct of the unwanted decarbonylation of furfural; thus, the catalyst must be compatible with the presence of carbon monoxide in the environment and must not be slowly poisoned by it to ensure a satisfactory industrial lifespan.

[0011] One of the aims of the invention is to provide a catalyst for transforming furfural into 2-methylfuran which has the aforementioned advantages.

[0012] Another object of the invention is to provide a process for preparing 2-methylfuran from furfural.

[0013] Another object of the invention is to provide a method for preparing 2-methyltetrahydrofuran from furfural.

[0014] To this end, the invention has as its first object a process for preparing 2-methylfuran comprising a step a) of reacting furfural in the presence of hydrogen and a catalyst comprising copper, aluminum and a transition metal selected from zirconium, manganese and a mixture thereof, by which 2-methylfuran is formed.

[0015] 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. The invention 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 hydrogenation catalysts are not necessarily capable of carrying out hydrogenolysis and vice versa.

[0016] In reaction a), hydrogenolysis immediately follows hydrogenation, and furfurol (the intermediate product) is generally not isolated. Therefore, the reaction a) of furfural to form 2-methylfuran is carried out in a single step. Generally, the process does not employ any hydrogenolysis catalyst other than the one mentioned above. 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.

[0017] The process of the invention is advantageously easy to implement, selective in 2-methylfuran, economical, industrially viable and allows to obtain a high conversion of furfural.

[0018] Preferably, step a) is carried out in the gas phase.

[0019] By "gas phase" or "gaseous phase" we mean that the hydrogen and the furfural and the furfurol (intermediate product) are in the gaseous state under the temperature and pressure conditions of reaction a). The process typically includes, before step a), a vaporization step of the furfural.

[0020] However, the catalyst remains in solid form during reaction a). Typically, the catalyst is a heterogeneous catalyst.

[0021] The process then employs heterogeneous gas-phase catalysis, which is preferred at the industrial level. It has the advantage of not using a solvent, thus avoiding the costs of solvent recycling and / or waste solvent treatment. Furthermore, a gas-phase process is generally more productive than a liquid-phase process, and therefore more economical.

[0022] Furfural

[0023] Furfural preferably has an acid value below 7 mmol / kg, and in particular below 5 mmol / kg. Such acid values ​​improve the catalyst's longevity. The acid value of furfural can be measured, for example, as follows: 200 mL of deionized water are introduced into an Erlenmeyer flask and stirred. A pH probe is immersed in this water, and once it has 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 the calculation of the amount in mmol of NaOH needed to neutralize 1 kg of furfural.

[0024] 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 to reduce the acid value of furfural, for example by distillation, to a value below 7 mmol / kg.

[0025] Catalyst The process employs 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.

[0026] 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.

[0027] Preferably, the catalyst does not contain chromium, nickel, palladium, ruthenium, or mixtures thereof. Generally, reaction a) of the process is not carried out in the presence of Cr, Ni, Pd, Ru, Ni, or mixtures thereof.

[0028] Preferably, the transition metal is zirconium. Alternatively, the transition metal is manganese.

[0029] The catalyst may also include one or more other additives such as stabilizers and / or shaping aids like lubricants or binders. Lubricants may be graphite, oils, or stearates. Binders may be aluminum oxide, silica, calcium aluminate, calcium silicate, or clay minerals.

[0030] In one 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, metal oxide, or a mixture of metal and metal oxide), and optionally one or more additives, notably as defined above. This / these additive(s) is / are generally free of transition metal(s), or even of any metal other than calcium or aluminum (in any form: metal, metal salt, metal oxide).

[0031] The catalyst is preferably used in the form of a tablet or pellet.

[0032] The weight quantities 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).

[0033] 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 between 15% and 60% by weight, especially between 20% and 55% by weight, preferably between 25% and 50% by weight, and particularly preferably between 28% and 47% by weight, relative to the weight of the catalyst. The amount of aluminum in the catalyst is preferably between 8% and 29% by weight, especially between 15% and 25% by weight, and particularly between 16% and 21% by weight, relative to the weight of the catalyst.

[0034] The quantity of transition metal in the catalyst is preferably between 0.5 and 30% by weight, in particular between 2 and 25% by weight, more particularly between 4 and 20% by weight, especially between 5 and 19% relative to the weight of the catalyst.

[0035] When the transition metal is zirconium, the amount of zirconium is preferably between 0.5 and 30% by weight, in particular between 5 and 20% by weight, more particularly between 10 and 20% by weight, especially between 16 and 19% by weight relative to the weight of the catalyst.

[0036] When the transition metal is manganese, the amount of manganese is preferably between 0.5 and 20% by weight, in particular between 2 and 15% by weight, more particularly between 4 and 10% by weight, especially between 5 and 8% by weight relative to the weight of the catalyst.

[0037] 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.

[0038] 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 be selective.

[0039] Within the catalyst, copper can be present in the form of copper (Cu), copper oxide, particularly in the form of CuO, or a mixture of these.

[0040] Within the catalyst, aluminum can be present in the form of aluminum (Al), aluminum oxide, notably in the form of Al2O3, or a mixture of these.

[0041] Within the catalyst, the transition metal can be present as the metal, the metal oxide, or a mixture thereof. Typically, manganese can be present as the metal (Mn), the oxide, preferably manganese dioxide (MnO2) or Mn3O4, or a mixture of the metal and the oxide. Similarly, zirconium can be present as the metal (Zr), the oxide, particularly ZrO2, or a mixture thereof.

[0042] Copper and transition metals are typically at least partially in oxide form before catalyst activation. By "at least partially in oxide form," we mean that some or all of the metal is in oxide form (or a mixture of oxides).

[0043] 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 mixtures thereof, with an alkaline aqueous solution, particularly a carbonate salt solution, thereby forming a precipitate, which is then calcined. The processes described in US applications 2018 / 0297015 or 2022 / 0401928 can be used, for example. Thus, the process may include, prior to step a), a catalyst preparation step a0).

[0044] 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.

[0045] 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.

[0046] Typically, catalysts are marketed in two forms:

[0047] - solid catalysts which are generally at least partially oxidized and therefore it is best to activate them before use,

[0048] - Catalysts dispersed in a liquid (usually a heavy alcohol). In this case, the catalyst is generally already in a reduced, and therefore active, form, and it is not necessary to activate it by reduction before use.

[0049] Thus, the process may include, prior to reaction a), the steps of: a1) supplying a catalyst comprising copper, aluminum and a transition metal selected from zirconium and manganese, said catalyst being in at least partially oxidized form, a2) activating the catalyst in at least partially oxidized form by reduction with a reducing agent, preferably with hydrogen.

[0050] Step a2) leads to the reduction of the catalyst into at least a partially oxidized form to form the catalyst in a reduced and active form, and thus to the activation of the catalyst.

[0051] Preferably, the reducing agent used is hydrogen, which allows the catalyst activation step to be carried out "in situ," meaning that the catalyst activation by contact with hydrogen is performed in the same reactor used for reaction a) of furfural. Alternatively, the activation can take place in a different reactor. The activated catalyst is then preferably kept in wet form or dispersed in a solvent, for example, an organic solvent, before use in step a), to prevent it from oxidizing again.

[0052] 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.

[0053] reaction conditions a)

[0054] Reaction a), or even the process as a whole, is generally carried out continuously.

[0055] Reaction a) of the process according to the invention is carried out under pressure, preferably of 1.05 bar a at 10 bar a , in particular 1.1 bar a at 5 bar a where Bar a is the unit of absolute pressure (it being understood that when the reaction is in the gas phase, the temperature is adjusted so that it is in the gas phase).

[0056] During reaction 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.

[0057] Reaction a) of the process can be carried out at a temperature between 150 and 240°C, in particular between 190 and 240°C, preferably between 200 and 238°C, and more preferably between 210 and 235°C (it being understood that when reaction a) is in the gas phase, the pressure is adjusted to ensure 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.

[0058] The weight-hourly space velocity (WHSV) of furfural, corresponding to the mass of furfural passing over the mass of catalyst used in 1 h, can range from 0.2 to 1.5 h -1 preferably from 0.3 to 0.8 hours -1 The lower the WHSV, the longer the furfural residence time 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.

[0059] Purification of 2-methylfuran

[0060] The 2-methylfuran obtained at the end of reaction a) is mixed with water formed by the reaction.

[0061] The process may include, after reaction a), the purification of the 2-methylfuran obtained, typically by distillation possibly preceded by decantation to remove water.

[0062] Installation for implementing reaction a) Reaction a) can be implemented by passing the gaseous mixture comprising furfural and hydrogen through one or more fixed beds of catalyst. The fixed beds can consist of one or more layers of catalyst. In the case of implementing a catalytic bed comprising several layers of catalyst, the metal concentration (e.g., 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).

[0063] Reaction a) can be carried out in one or more tubular or multitubular reactors in series or in parallel.

[0064] The reactor temperature can be maintained by means of a heat transfer fluid which can be heated by steam, electricity 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.

[0065] The reactor can be fed with the gas phase by first passing the furfural, initially in liquid form, through an evaporator (for example, one heated by steam or any other known method). The evaporator temperature is set to ensure the furfural transitions from a liquid to a gaseous state under the required 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.

[0066] According to a second object, the invention relates to the use of a catalyst comprising copper, aluminum and a transition metal selected from zirconium, manganese and mixtures thereof for the preparation of 2-methylfuran from furfural.

[0067] The embodiments described above for the first object are of course applicable.

[0068] According to a third object, the invention relates to a process for preparing 2-methyltetrahydrofuran from furfural, comprising the steps of: a) preparing 2-methylfuran by reacting furfural as defined above, whereby 2-methylfuran is formed, b) hydrogenating the 2-methylfuran obtained in step a) in the presence of hydrogen, whereby 2-methyltetrahydrofuran is formed.

[0069] The embodiments described above for step a) of preparing 2-methylfuran by reacting furfural are of course applicable. Step b) of hydrogenating 2-methylfuran to form 2-methyltetrahydrofuran can be carried out by any known method, in the gas or liquid phase.

[0070] Catalyst for step b) of hydrogenation of 2-methylfuran

[0071] Generally, the hydrogenation b) of 2-methylfuran is carried out in the presence of a catalyst, referred to below as the hydrogenation catalyst. For example, the hydrogenation b) of 2-methylfuran can be carried out in the presence of a palladium-based catalyst, such as palladium supported on carbon or alumina, or in the presence of a nickel-based catalyst, particularly nickel supported on silica or alumina.

[0072] In a particularly preferred embodiment, the hydrogenation (b) of 2-methylfuran is carried out in the presence of a catalyst comprising nickel supported on alumina (Ni / Al2O3). The nickel may be in the form of metal (Ni), nickel oxide, or a mixture thereof.

[0073] The amount of nickel in the catalyst can be from 5 to 22% by weight, in particular from 7% to 20% by weight, especially from 8% to 18%, preferably from 10% to 17% by weight relative to the weight of the catalyst.

[0074] 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.

[0075] Such catalysts and their production are accessible to those skilled in the art. Examples include Chang et al., “Reductive amination of polypropylene glycol using Ni-CeO2@Al2O3 with high activity, selectivity and stability”, Catalysis Communications, vol 127, 2019, p.15-19, and Gavrilovic et al., “Ni alumina-based catalyst for sorption enhanced reforming - Effect of calcination temperature”, Catalysis Communications, Vol 185, 2023, p.106800.

[0076] The catalyst preferably has a specific surface area greater than or equal to 70 m² 2 / 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.

[0077] The hydrogenation catalysts described above allow for the 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.

[0078] The catalyst is preferably used in the form of a tablet, bead or extrudate.

[0079] Possible activation of the hydrogenation catalyst b) The process may include, before hydrogenation b), a step of activating the hydrogenation catalyst.

[0080] 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 where 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 moist form or in an organic solvent, for example, in an alcohol, before use in step b). Activation of the catalyst is carried out using conventional methods, well known to those skilled in the art. For example, catalyst activation can be performed in a reducing atmosphere, particularly in a hydrogen stream at a temperature ranging from 100°C to 250°C, for example, from 120°C to 200°C.

[0081] Reaction conditions for the hydrogenation b) of 2-methylfuran

[0082] The hydrogenation of 2-methylfuran to 2-methyltetrahydrofuran takes place in the presence of hydrogen and usually a catalyst, preferably as described above.

[0083] Preferably, it takes place in the gas phase.

[0084] Hydrogenation preferably takes place under pressure, preferably at 1.05 bar a at 15 bar a , in particular 1.1 bar a at 12 bar a preferably 1.2 bar a at 10 bar a (it being understood that when hydrogenation b) is in the gas phase, the temperature is adjusted so that it is in the gas phase).

[0085] The hydrogen / 2-methylfuran molar ratio is preferably from 2 to 25, preferably from 3 to 20, more preferably from 5 to 18.

[0086] Hydrogenation can be carried out at a temperature of 110 to 170°C, in particular from 115°C to 160°C, preferably from 120°C to 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).

[0087] The weight hourly space velocity (WHSV) for furfural, corresponding to the mass of 2-methylfuran passing over the mass of catalyst used in 1 hour, can range from 0.2 to 1.5 h -1 , preferably from 0.3 to 1.0 h- 1 .

[0088] Installation for the implementation of hydrogenation b)

[0089] Hydrogenation is generally carried out using one or more fixed beds of hydrogenation catalyst. Each fixed bed can consist of one or more layers of catalyst. When implementing a catalytic bed with multiple catalyst layers, the concentration of hydrogenation catalyst can increase from the reactor inlet to the outlet. The number of layers can vary depending on the length of the catalytic bed, and the catalyst can be diluted in an inert material (such as glass, quartz, or ceramic).

[0090] Hydrogenation can be carried out within 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, electricity 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] Purification of 2-methyltetrahydrofuran

[0093] 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.

[0094] The following examples illustrate the invention.

[0095] 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] [Table 1]

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

[0100] A double-jacketed tubular reactor was filled with 50.2 g of dry catalyst and heated at a rate 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 testing was counted from the point at which temperatures inside the reactor stabilized. Each sample was taken after at least 45 minutes of stable conditions. Table 2 below provides the compositions of the samples taken, including the mass yields of 2-methylfuran (RR MeF), determined by GC-FID (Shimadzy GC-FID 2010 pro) in methanol as the solvent and n-nonane as the external standard, as a function of reaction temperature, catalyst type, H₂ / furfural molar ratio, and WHSV. The identified byproducts are methyltetrahydrofuran, gamma-valerolactone, 2-pentanone, 1-pentanol, and 2-pentanol.

[0102] Other unidentified compounds are present according to the equation: TT-ZRR assayed. They are not visible by GC-FID because they are heavy compounds or degradation products. [Table 2]

[0103] TT = conversion rate

[0104] 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

[0105] With the CuZn catalyst, the maximum yield under optimized conditions (82%) was lower than those obtained with the other catalysts (87% or more).

[0106] Using CuCr as a 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 CuAIMn or CuAIZr as a catalyst, making the reaction conditions harsher by increasing the WHSV improved the yield of 2-methylfuran.

[0107] Evolution of catalyst performance in the presence of CO

[0108] During step a), traces of furan are observed. Furan is formed by the 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.

[0109] 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 baseline measurement before the addition of CO and to a baseline measurement after the addition of CO.

[0110] 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. Initial performance is therefore not recovered after the CO introduction is stopped. Consequently, the compatibility of the CuCr catalyst with carbon monoxide is insufficient for industrial use.

[0111] With the CuAIZr catalyst, the presence of 5% v / v CO in the gas stream did not significantly affect the observed performance, which was similar before, during, and after the CO passage. CuMnAI also maintains performance even in the presence of CO.

[0112] Example 2: Step b): Preparation of 2-Methyltetrahydrofuran from 2-Methylfuran. 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 to 100°C. 2-Methylfuran was then introduced at a flow rate of 0.4 mL / min.

[0113] 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.

[0114] With this process, depending on the catalysts used, the pressure, temperature, hourly spatial velocity, weight of 2-methylfuran, and H2 / 2-methylfuran ratio were optimized to achieve the highest possible conversion to 2-methylTHF. The optimized conditions and the composition of each catalyst are shown in Table 3.

[0115] Table 3 below provides the compositions of the samples taken, including 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 H2 / MeF (2-methylfuran) molar ratio and the WHSV.

[0116] The identified byproducts are 2-pentanone, 2-pentanol, 1-pentanol and n-pentane.

[0117] Other unidentified compounds are present according to the equation: TT-ZRR assayed. They are not visible by GC-FID because they are heavy compounds or degradation products. [Table 3]

[0118]

[0119] TT = conversion rate

[0120] Table 3: Yields of 2-methyltetrahydrofuran and by-products under optimized conditions

Claims

DEMANDS 1. A process for preparing 2-methylfuran in the gas phase comprising a step a) of reacting furfural in the presence of hydrogen and a catalyst comprising copper, aluminum and a transition metal selected from zirconium, manganese, and a mixture thereof, by which 2-methylfuran is formed.

2. A process for preparing 2-methylfuran according to claim 1, wherein the transition metal of the catalyst is zirconium.

3. A process for preparing 2-methylfuran according to claim 1 or 2, wherein: the amount of copper in the catalyst is 15 to 55% by weight, relative to the total weight of the catalyst, and / or the amount of aluminum in the catalyst is 8% to 29% by weight, relative to the total weight of the catalyst, and / or the amount of transition metal in the catalyst is 0.5% to 30% by weight, relative to the total weight of the catalyst.

4. A process for preparing 2-methylfuran according to any one of the preceding claims, wherein the catalyst does not comprise chromium.

5. A process for preparing 2-methylfuran according to any one of the preceding claims, wherein step a) takes place at a temperature of 150°C to 240°C.

6. A process for preparing 2-methylfuran according to any one of the preceding claims, wherein the molar ratio of hydrogen to furfural is 1.5 to 10.

7. A process for preparing 2-methyltetrahydrofuran from furfural comprising the steps of: a) preparing 2-methylfuran by reacting furfural according to any one of the preceding claims, thereby forming 2-methylfuran, b) hydrogenation of the 2-methylfuran obtained in step a) in the presence of hydrogen, by which 2-methyltetrahydrofuran is formed.

8. Process for preparing 2-methyltetrahydrofuran according to claim 7, wherein hydrogenation b) is carried out in the presence of a catalyst comprising nickel supported on alumina.

9. Process for preparing 2-methyltetrahydrofuran according to claim 8, wherein the catalyst for hydrogenation b) comprises from 5 to 22% by weight of nickel relative to the total weight of the catalyst.

10. A process according to any one of claims 7 to 9, wherein hydrogenation b) takes place at a temperature from 110°C to 170°C.

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