Process for dehydrating alcohol-containing feedstocks for the production of alkenes - Patent Application 20070122997

Abstract

The present invention relates to compounds of the formula R-CH2-OH, where R is a compound of the general formula C n H 2n+1 (wherein n is an integer from 3 to 20) is a non-linear alkyl group, the process comprising isomerizing and dehydrating a feedstock comprising at least one primary monoalcohol of the formula (I), wherein n is an integer from 3 to 20, at a weighted average temperature of 200 to 300°C, a pressure of 0.1 to 1 MPa, and a weight hourly space velocity (PPH) of 1 to 25 h , in the presence of a catalyst comprising at least one zeolite. -1 The zeolite has at least one series of channels with pore openings defined by eight oxygen rings (8MR) and a mesopore volume of 0.10 ml / g or greater.

Description

[Technical Field]

[0001] The present invention relates to an improved process for the preparation of alkenes from a feedstock containing at least one primary monoalcohol of formula R-CH2-OH, wherein R is a compound of the general formula C n H 2n+1 where n is an integer between 3 and 20. The feedstock may be obtained by chemical or fermentation methods, which use a dehydration reaction in the presence of a zeolite-based catalyst with specific textural and morphological characteristics.

[0002] The resulting alkenes, such as butenes, in particular isobutene, 1-butene and 2-butene, are of great interest in the petrochemical industry and in the field of organic synthesis. [Background technology]

[0003] Butenes are key molecules in petrochemistry, especially for the synthesis of gasoline additives such as ETBE and MTBE. The majority of scientific publications concern the production of isobutene from n-butanols, which are more readily produced than isobutanol by conventional fermentation routes (ABE). Recent developments, however, have made it possible to significantly improve the fermentation yield of isobutanol, making this feedstock available and available at an attractive cost.

[0004] The conversion of branched alcohols into alkenes, such as the conversion of isobutanol into butenes, is of great interest in the field of petrochemistry. The selectivity of the dehydration reaction in the presence of a solid catalyst and the stability of the catalyst in the presence of water produced by the reaction remain parameters that those skilled in the art constantly strive to improve. Furthermore, during alcohol dehydration, the resulting alkenes can undergo oligomerization reactions, especially at the acid sites of the dehydration catalyst, leading to the deactivation of the catalyst (coking, pore blockage, and acid site poisoning). This well-known phenomenon must be strictly limited in the presence of zeolite catalysts and in the absence of hydrogen in order to improve the catalyst's service life and thus the profitability of the alcohol dehydration process.

[0005] Furthermore, alcohols produced by fermentation of biomass or syngas contain impurities in the form of oxygen- and nitrogen-containing compounds formed during the yeast metabolism of the feedstock to alcohols. These compounds can have a detrimental effect on catalytic processes using biobased alcohols or their products, particularly by forming undesirable species that cause deactivation of dehydration or oligomerization catalysts or by poisoning active sites. If these compounds are basic, they can neutralize the acid sites of catalysts commonly used in dehydration, oligomerization, or polymerization reactions. Oxygen-containing compounds, such as aldehydes, esters, and ethers, can be partially removed by various pretreatments, particularly during the separation of alcohol from the fermentation medium. Additional steps can be taken to remove oxygen-containing compounds not separated during distillation. Due to their Bronsted or Lewis basicity, basic nitrogen-containing compounds (amines, pyrazines) can poison the acid sites of the catalyst, causing its deactivation. Therefore, their removal is preferable to increase the catalyst cycle time and maintain process selectivity. Moderately acidic catalysts are at greater risk of deactivation in the presence of strongly basic molecules.

[0006] Patent document 1 describes the modification of a zeolite of structural type FER in the form of a powder by treatment or ion exchange in the presence of an organic acid, which makes it possible to reduce the ratio of strong to weak acid sites to less than 1. The catalyst is used for the simultaneous reactions of dehydration and skeletal isomerization of isobutanol. This treatment makes it possible to slightly limit the formation of coke on the catalyst and, in particular, to modify its properties (C / H) while maintaining a good activity and good selectivity for butenes, without improving them.

[0007] Chadwick et al. (Non-Patent Document 1) test various zeolites: theta-1, ZSM-23, ferrierite (Si / Al=10 or 22.5), and ZSM-5 (10MR) for the simultaneous dehydration and isomerization of n-butanol to give isobutene at 400 °C. They demonstrate a loss of isomerization activity of ferrierite for isobutene formation over time and attribute it to the adverse effect of water formed by the dehydration reaction, leading to its dealumination. This is not observed in the other zeolites tested, and ferrierite is the least stable of the zeolites tested.

[0008] Patent Document 2 describes the molding of ferrierite zeolite with an alumina binder and its use in low-temperature alcohol dehydration reactions. Patent Document 2 shows that when a tested ferrierite with a Si / Al ratio of 20 is molded with alumina, the performance is improved compared to when it is molded with silica: the conversion achieved with a catalyst based on ferrierite and alumina is 250°C, WHSV 7h -1 The ratio of normal butenes to total butenes is about 87%, whereas the catalyst based on ferrierite and silica binders provides a WHSV of over 90% at 7h. -1 It is 72.5%, and the ratio of normal butenes to total butenes is about 82%. No mention is made of the stability of the catalyst.

[0009] Van Daele et al. (Non-Patent Document 2) attempted to elucidate the mechanism of the dehydration of isobutanol over various zeolites differing in Si / Al, particularly over ferrierite zeolite. Their objective was to understand the exceptional selectivity for n-butenes obtained from the branched C4 alcohol isobutanol. For this purpose, the ratio (surface acidity / total acidity) and the nature of the acidity (Lewis acidity / Brønsted acidity) were modified by different ferrierite treatments. Ferrierites with different morphologies were synthesized to adjust the amount of crystalline pores, surface area, and external acidity. The effect of the external acidity of the zeolite on activity was demonstrated, but a clear correlation with selectivity for n-butene or catalyst stability could not be established. For zeolites with an external surface area of ​​240 m 2 A 15% loss of activity was observed in 4 hours for ferrierite in the form of nano-acicular ferrite with an external surface area of ​​42 m / g. 2 The ferrierite nanosheets were found to be 33% of the total ferrierite nanosheets / g. -1 Studies have been carried out on WHSV; the conversion level is less than 60%.

[0010] The object of the present invention is to overcome the drawbacks of the prior art processes for the dehydration of branched alcohols to alkenes using zeolites by providing a process which is improved, in particular in terms of: - the stability of the dehydration catalyst and its service life by limiting its deactivation; - Profitability of the dehydration process in terms of catalytic activity, selectivity and yield of target products: linear alkenes. [Prior art documents] [Patent documents]

[0011] [Patent Document 1] International Publication No. 2016 / 046296 [Patent Document 2] International Publication No. 2018 / 087031 [Non-patent literature]

[0012] [Non-Patent Document 1] Chadwick et al., Chem. Commun., 2010, Vol. 46, pp. 4088-4090 [Non-patent document 2] Van Daele et al., Applied Catalysis B: Environmental, 2021, No. 284, p. 119699 Summary of the Invention [Means for solving the problem]

[0013] (Summary of the Invention) The present invention relates to a process for the isomerization dehydration of a feedstock comprising at least one primary monoalcohol of formula R-CH2-OH, wherein R is a compound of the general formula C n H 2n+1 (wherein n is an integer of 3 to 20), and the method includes a vapor phase isomerization dehydration step, which is carried out in the presence of a catalyst, at a weighted average temperature of 200 to 300°C, a pressure of 0.1 to 1 MPa, and an hourly space velocity (WHSV) of 1 to 25 h -1 and the catalyst comprises at least one zeolite, wherein the zeolite has at least one series of channels, the pore openings of the channels being defined by rings of eight oxygen atoms (8MR), and has a mesopore volume of 0.10 mL / g or greater.

[0014] The advantage of the process according to the invention lies in the fact that the use of a catalyst comprising a zeolite according to the invention and having particular textural properties makes it possible to obtain improved performance, notably in terms of stability, but also in terms of selectivity for linear alkenes and conversion of the feedstock.

[0015] The catalyst remains active and stable at temperatures lower than those normally used. The possibility of operating at temperatures below 300°C while maintaining full conversion of the alcohol is also an advantage of the present invention.

[0016] The resulting linear alkenes are of great interest in the petrochemical industry and in organic synthesis. Controlled oligomerization of these alkenes may make it possible to produce aviation fuel and thus obtain BioJet.

[0017] The Applicant has surprisingly demonstrated that the use of a catalyst comprising a zeolite according to the invention and having particular textural properties in a process for the isomerization dehydration of a feedstock containing primary monoalcohols makes it possible to obtain a conversion of said alcohol that is much higher than that obtained with the zeolites used in the processes of the prior art, together with low deactivation of the zeolite catalyst.

[0018] The applicant has surprisingly demonstrated that the use of a catalyst comprising a zeolite according to the invention and having particular textural properties (especially a particular mesopore volume) makes it possible to capture basic nitrogen impurities present in the alcoholic feedstock in the isomerization dehydration reaction, thereby producing an alkene effluent with a low content of nitrogen-containing compounds, particularly upstream of the oligomerization step, and thus also protects the catalyst downstream of the isomerization dehydration, in particular the oligomerization catalyst, from deactivation. The advantage of using a highly active catalyst according to the invention is that it allows simultaneous capture of basic nitrogen-containing molecules and isomerization dehydration of alcohols at the temperature of the dehydration reaction. This makes it possible to avoid an intermediate step of purifying the effluent containing alkenes obtained upstream of the oligomerization step. DETAILED DESCRIPTION OF THE INVENTION

[0019] (Description of the embodiment) According to the present invention, the expressions "of between A and B" and "between A and B" are synonymous and mean that both limits of the interval (A, B) are included in the range of values ​​stated. If this is not the case and if both limits are not included in the range stated, such details will be provided by the present invention.

[0020] Within the meaning of the present invention, ranges of various parameters for a given process, such as pressure ranges and temperature ranges, may be used alone or in combination, for example, a range of pressure values ​​that is preferred within the meaning of the present invention may be combined with a range of temperature values ​​that is more preferred.

[0021] In the following, specific embodiments of the present invention will be described, which may be implemented separately or in combination with each other, and there is no limitation on this combination, provided that the combination is technically feasible.

[0022] (Feed material) According to the invention, the feedstock to be treated in the process according to the invention has the formula R-CH2-OH, where R is a compound of the general formula C n H 2n+1 (wherein n is an integer from 3 to 20)), alone or in mixtures, the feedstock preferably comprises, and preferably consists of, at least one primary monoalcohol (e.g., isobutanol).

[0023] In the remainder of this specification, the term alkyl refers to a group of the general formula C n H 2n+1 in which n is an integer between 3 and 20, preferably between 3 and 10, preferentially between 3 and 5, or equal to 4.

[0024] In one embodiment, the feedstock comprises a minimum of 40 wt. % primary monoalcohol relative to the total weight of said feedstock.

[0025] In one embodiment, the feedstock comprises a minimum of 70 wt. % primary monoalcohol relative to the total weight of said feedstock.

[0026] In one embodiment, the feedstock comprises at least 90% by weight of primary monoalcohols relative to the total weight of said feedstock.

[0027] As primary monoalcohols according to the invention, mention may be made of isobutanol, 2-methylbut-1-ol, 2,2-dimethylpropan-1-ol, 2-methylpentan-1-ol, 2,2-dimethylbutan-1-ol, and 2-ethylbutan-1-ol, either alone or in mixtures.

[0028] The primary monoalcohol is preferably isobutanol or 2-methyl-1-butanol, used alone or as a mixture. Highly preferably, the primary monoalcohol is isobutanol. Preferably, the feedstock comprises 40% to 100% by weight, preferably 70% to 100% by weight, and preferentially 90% to 100% by weight of isobutanol.

[0029] The feedstock may originate from a chemical or biochemical process, such as a fermentation process, in particular from at least one biomass fermentation process, in particular from lignocellulosic biomass.

[0030] The feedstock may contain water, in particular up to 60% by weight of water, preferably up to 30% by weight of water, preferentially up to 10% by weight of water. It may also contain inorganic impurities (e.g., Na, Ca, P, Al, Si, K, SO4) and organic impurities (e.g., methanol, ethanol, n-butanol, aldehydes, ketones, and the corresponding acids, e.g., furoic acid, acetic acid, isobutyric acid).

[0031] The feedstock may contain nitrogen impurities, particularly total nitrogen, at 5 to 100 ppm.

[0032] (method) According to the present invention, the process comprises a step of isomerization dehydration of a feedstock containing at least one primary monoalcohol of formula R-CH2-OH, preferably carried out in the gas phase in the presence of a dehydration catalyst at a weighted average temperature of 200-300°C, preferably 210-280°C, and highly preferably 230-270°C, at a pressure of 0.1-1.0 MPa, preferably 0.3-1.0 MPa, and highly preferably 0.5-1.0 MPa, and at a weight hourly space velocity (WHSV) of 1-25 h -1 , preferably 1 to 20 hours -1 , preferably 1 to 18 hours -1 and in the presence of a dehydration catalyst.

[0033] Advantageously, the dehydration is carried out in one or a series of reactors containing at least one catalyst bed.

[0034] WHSV is understood to correspond to the weight hourly space velocity (WHSV), which means the mass flow rate of the primary monoalcohol feedstock (considered dry) at the reactor inlet divided by the mass of catalyst in said reactor.

[0035] The weighted average temperature (denoted WAT) means the average of the temperature in a catalyst bed, a bed being a set of beds present in a reactor in which a catalytic reaction takes place, calculated along the axis of flow in said bed. For a bed of length L and surface area S, with the reactive mixture flowing along the longitudinal axis x of the bed, the inlet to the catalyst bed forming the origin of the axis (x=0), the weighted average temperature (denoted WAT) is expressed according to the following formula:

[0036]

number

[0037] Since the reaction is endothermic and the reactor operates in either isothermal or adiabatic mode, the weighted average temperature will represent the reaction temperature.

[0038] The reaction is advantageously carried out in one or more reactors, for example isothermal or adiabatic reactors, which are arranged in particular in series or in parallel, preferably in series, each reactor being operated under specific or identical conditions. Those skilled in the art will be able to adjust the selection of operating conditions (pressure, temperature WAT, residence time) for each reactor depending on the feedstock in order to obtain the optimum conversion and the desired selectivity for linear olefins.

[0039] Preferably, the dehydration catalyst is disposed in one or more fixed beds, which may be operated in upflow, downflow or radial flow mode.

[0040] Since the dehydration reaction is endothermic, the dehydration step advantageously includes the input of heat, which may be achieved by any heating means known to those skilled in the art.

[0041] Preferably, prior to contact with the feedstock to be treated, the dehydration catalyst is activated by any means known to those skilled in the art, for example, by heat treatment in air.

[0042] The process according to the invention makes it possible to operate at low temperatures, in particular at temperatures below 300°C, preferably below 270°C. The advantage of operating at low temperatures in the process according to the invention is that it makes it possible to avoid local overheating of the alcohol (excessive temperatures on contact with the metal surfaces of the reactor or the feed transport lines), with the potential risk of decomposition of the primary monoalcohol, e.g., isobutanol; and to reduce utility consumption and operating costs. The process according to this embodiment is therefore very economically advantageous.

[0043] (Dehydration catalyst) According to the present invention, the dehydration catalyst used comprises at least one zeolite having at least one series of channels, the pore openings of which are defined by rings of eight oxygen atoms (8MR), and a mesopore volume of at least 0.10 mL / g.

[0044] According to one embodiment, the zeolite may advantageously have at least one series of channels whose pore openings are defined by rings containing 10 oxygen atoms (10MR), as defined in the classification "Atlas of Zeolite Framework Types", Ch. Baerlocher, LB McCusker, DH Olson, 6th edition, Elsevier, 2007, Elsevier.

[0045] The zeolite is advantageously chosen from zeolites with channels of 8 and 10 MR, such as zeolites of structural type FER and MFS, used alone or as a mixture. More advantageously, in the FER type, the zeolite is chosen from ferrierite, FU-9, ISI-6, NU-23 and ZSM-35 zeolites, and for the MFS type, it is ZSM-57 zeolite, used alone or as a mixture. The zeolite is highly advantageously of the FER type, preferably ferrierite. Preferably, the zeolite consists of ferrierite.

[0046] In one embodiment, the mesopore volume of the zeolite is 0.15 mL / g or greater.

[0047] In one embodiment, the mesopore volume of the zeolite is 0.18 mL / g or greater.

[0048] In one embodiment, the mesopore volume of the zeolite is greater than or equal to 0.20 mL / g, preferably greater than or equal to 0.22 mL / g, and preferentially greater than or equal to 0.24 mL / g.

[0049] Preferably, the mesopore volume of the zeolite is less than or equal to 0.50 mL / g, preferably less than or equal to 0.40 mL / g, preferentially less than or equal to 0.35 mL / g, and suitably less than or equal to 0.30 mL / g.

[0050] In one embodiment, the mesopore volume of the zeolite is 0.18 to 0.50 mL / g.

[0051] In one embodiment, the mesopore volume of the zeolite is 0.20 to 0.40 mL / g.

[0052] In one embodiment, the mesopore volume of the zeolite is 0.22 to 0.35 mL / g.

[0053] In one embodiment, the mesopore volume of the zeolite is 0.24 to 0.30 mL / g.

[0054] In one embodiment, the zeolite has a Si / Al molar ratio of 5-45.

[0055] In one embodiment, the zeolite has a Si / Al molar ratio of 5-30.

[0056] In one embodiment, the zeolite Si / Al molar ratio is 8-20.

[0057] In one embodiment, the zeolite has a Si / Al molar ratio of 9-15.

[0058] In one embodiment, the zeolite has a Si / Al molar ratio of 11-13.

[0059] In one embodiment, the micropore volume of the zeolite is 0.100 to 0.150 mL / g.

[0060] In one embodiment, the micropore volume of the zeolite is 0.110 to 0.145 mL / g.

[0061] In one embodiment, the micropore volume of the zeolite is 0.120 to 0.140 mL / g.

[0062] In one embodiment, the micropore volume of the zeolite is 0.130 to 0.140 mL / g.

[0063] In one embodiment, the micropore volume of the zeolite is 0.133 to 0.138 mL / g.

[0064] In one embodiment, the external surface area of ​​the zeolite is between 10 and 70 m 2 / g.

[0065] In one embodiment, the external surface area of ​​the zeolite is between 20 and 65 m 2 / g.

[0066] In one embodiment, the external surface area of ​​the zeolite is between 30 and 60 m 2 / g.

[0067] In one embodiment, the external surface area of ​​the zeolite is between 35 and 55 m 2 / g.

[0068] In one embodiment, the external surface area of ​​the zeolite is 45 to 50 m 2 / g.

[0069] In one embodiment, the zeolite average crystal size is less than or equal to 100 nm.

[0070] In one embodiment, the average crystal size of the zeolite is 10 to 100 nm.

[0071] In one embodiment, the average crystal size of the zeolite is 30 to 95 nm.

[0072] In one embodiment, the average crystal size of the zeolite is 40 to 90 nm.

[0073] In one embodiment, the average crystal size of the zeolite is 50 to 85 nm.

[0074] In one embodiment, the average crystal size of the zeolite is 60 to 80 nm.

[0075] In one embodiment, the BET surface area of ​​the zeolite is 400 m 2 / g or more.

[0076] In one embodiment, the BET surface area of ​​the zeolite is 405 to 450 m 2 / g.

[0077] In one embodiment, the BET surface area of ​​the zeolite is 410 to 440 m 2 / g.

[0078] In one embodiment, the BET surface area of ​​the zeolite is 415 to 430 m 2 / g.

[0079] The crystals of the zeolite according to the invention have a rounded elongated shape, in particular an oval or spheroidal shape.

[0080] Advantageously, the zeolite crystals according to the invention are not in the form of needles or platelets.

[0081] The crystals of the zeolite according to the invention, unlike the zeolites used in the prior art methods, are arranged in the form of aggregates, preferably spherical.

[0082] The catalyst may be in powder form or may be molded.

[0083] Advantageously, the zeolite content of the dehydration catalyst is at least 50% by weight, preferably between 55% and 90% by weight, highly preferably between 60% and 80% by weight, relative to the total weight of said dehydration catalyst.

[0084] In one embodiment, the dehydration catalyst is metal-free.

[0085] "Metal free" means that there are no metals added during preparation.

[0086] According to one particular embodiment of the present invention, the catalyst is shaped with a binder, which is advantageously inert to the target reaction (isomerization dehydration of primary monoalcohols). Shaping the catalyst with a binder allows a person skilled in the art to obtain a catalyst of macroscopic size whose physical properties (geometry, pore mass volume, etc.) can be tailored. Indeed, if zeolites cannot be used industrially in powder form, the binder allows the final solid to have the mechanical strength necessary for industrial use and to have increased strength in the presence of water. The binder also allows the catalyst thus configured to be used in a fixed bed in a reactor without excessive pressure loss.

[0087] The binder is preferably selected from silicate binders, such as silica, alumina binders, such as gamma alumina, AlPO4, clay, zirconia, Ti oxide, SiC, or mixtures thereof.

[0088] Preferably, the binder is a siliceous or aluminous binder. Preferably, the binder is a siliceous binder and consists essentially of silica, which means that the siliceous binder consists of silica except for impurities, which do not have a catalytic effect. In particular, the silica is amorphous silica.

[0089] Preferably, the binder content of the dehydration catalyst is between 10% and 45% by weight, preferably between 20% and 40% by weight, relative to the total weight of said catalyst.

[0090] The dehydration catalyst may be shaped in the form of extrudates, according to the geometric shape, for example cylindrical or multilobal, in particular trilobal, or quadrilobal.

[0091] The process according to the invention, which uses a dehydration catalyst comprising a zeolite having such morphological and textural characteristics, makes it possible to obtain optimized performance in the isomerization dehydration of primary alcohols, in particular with respect to alcohol conversion and selectivity towards linear alkenes. Furthermore, such a dehydration catalyst also exhibits improved deactivation stability and therefore extended service life, which makes it possible to achieve advantageous profitability of the isomerization dehydration process.

[0092] (Explanation of analysis method) To determine the micropore volume, the t method (of Lippens and De Boer) is used, as described in the periodical Journal of Catalysis (Studies on pore systems in catalysts V. The t method, J. Catal., 1965, 4(3), p. 319). It is based on a comparison between an experimental isotherm of a microporous solid and a reference isotherm of the same chemical nature (a non-porous solid). From the Lippens-De Boer equation, the thickness t of the multilayer can be calculated by the following formula (called t plot):

[0093]

number

[0094] where P / P0 is the relative pressure of nitrogen.

[0095] The micropore volume is calculated by the following formula:

[0096]

number

[0097] where Y is the y-axis at the origin of the t-plot curve and D is the density conversion factor (D = 15.468 × 10 -4, a coefficient that ensures the conversion from gas volume to liquid volume). The range of t chosen corresponds to the plateau on the nitrogen adsorption volume versus thickness t curve, which is 0.4–0.8 nm.

[0098] The mesopore surface area, also called the external surface area, is calculated here using the t-plot curve by the following formula:

[0099]

number

[0100] In the formula, S is the slope of the t-plot line, and D is the concentration conversion coefficient (D = 15.468 × 10 -4 , the coefficient for converting gas volume to liquid volume).

[0101] The mesopore volume is considered here to be equal to the total volume of nitrogen adsorbed at P / P0max minus the mass micropore volume.

[0102] The specific surface area or BET surface area is determined by the BET method (Brunauer, Emmett and Teller) described in the periodical "The Journal of American Chemical Society", 1938, 60, 309. It is based on the specificity of physical adsorption: multimolecular adsorption on sites of the same energy. Based on all the assumptions made in this theory (equivalent sites, no lateral interactions between the adsorbed molecules, each adsorbed molecule can function as an adsorption site), the specific surface area can be estimated from the volume Vm of nitrogen adsorbed in a monolayer by the following formula:

[0103]

number

[0104] The average size of zeolite crystals is measured by bright-field transmission electron microscopy or TEM. A histogram of crystal sizes was created from photographs taken by transmission microscopy in bright-field mode. The average size was determined from measurements of 200 crystals. The crystals observed for the zeolites according to the invention are preferably oval or spheroidal in shape. The representation of the crystals in the photograph is their projection along the beam axis. The dimensions used are estimates of the size of the crystals along the axis intersected by the beam as shown in FIG. 1, and the average is calculated for a sample of 200 crystals.

[0105] The following examples and figures are illustrative of the present invention, more particularly of certain embodiments of the present invention, and are not intended to limit the scope of the present invention.

[0106] (List of drawings) FIG. 1 shows a schematic representation of a crystal and the axis through which an electron microscope beam travels to calculate the size of the crystal.

[0107] FIG. 2 represents a scanning electron microscope (SEM) image of solid B according to the invention.

[0108] FIG. 3 shows a scanning electron microscope (SEM) image of comparative solid C.

[0109] (Example) Example 1: Testing of different catalyst samples in the process of dehydration of isobutanol to n-butenes The dehydration process is carried out in a catalyst testing EHD multi-reactor unit. This unit contains a fixed-bed reactor operated in downflow mode. The tested dehydration catalysts each contain 100 wt. % zeolite. Several zeolites were tested (see Table 2).

[0110] The catalysts are loaded separately into the reactor in the form of powders, pre-pelletized, crushed, and then sieved to retain the 300-500 μm fraction. The catalysts are packed into a quartz reactor with an internal diameter of 4 mm between two SiC beds. The catalysts are then activated at 450 °C for 6 hours under an air purge, after a temperature increase of 5 °C / min. The temperature is then reduced to the test temperature under nitrogen, and the air present in the system is removed before the injection of the isobutanol feedstock. The test is carried out at atmospheric pressure (i.e., approximately 0.1 MPa).

[0111] Different WHSV: 9, 6 and 3 hours at two temperatures: 240 and 250°C -1 Evaluated at 240℃, WHSV9h -1 A return point was made at the end of the test at 0°C. Each condition was maintained for 9 hours, which made it possible to obtain five chromatograms and evaluate the deactivation of the zeolite. The test lasted for 72 hours. The sequence of conditions was as follows; these were applied to all catalysts in exactly the same way:

[0112] [Table 1]

[0113] The feedstock is a mixture of isobutanol / water in a mass ratio of 99 / 1. It is vaporized at the top of the reactor in a SiC bed before contacting the catalyst bed.

[0114] The analysis of the entire effluent is carried out at the reactor outlet on an in-line gas chromatograph equipped with two capillary columns, which makes it possible to determine the conversion of isobutanol, the selectivity for different products, in particular the selectivity for butenes, and the proportion of normal butenes in the butene fraction, the aim being to maximize this proportion.

[0115] The zeolites tested are listed in the table below.

[0116] [Table 2]

[0117] The textural properties of the zeolites evaluated are shown in the table below.

[0118] [Table 3]

[0119] The catalytic results obtained for the various zeolites tested at reaction times of 8-9 hours and 70-72 hours after the test are shown in Table 4 below. The catalytic results presented include the conversion of isobutanol, the percentage of N-butene in total butenes (N-butene / total butene) at the start of the test and after at least 70 hours under load, and the conversion under iso conditions (240°C, WHSV 9h -1 ) is the loss of activity (or inactivation) as a percentage per unit time between conversion at the initial point (i.e., about 8-9 hours) and conversion at the end point (i.e., about 70-72 hours).

[0120] [Table 4]

[0121] It is noted that of the four ferrierites tested (A, B, C, and D), those according to the invention with mesopore volumes greater than 0.10 mL / g (i.e., zeolites A and B) exhibit much higher activity after 8-10 hours under load than those with mesopore volumes less than 0.10 mL / g (C and D). For example, at similar molar ratios (Si / Al=10), ferrierite A has a higher initial activity than ferrierite C (99.5% conversion in about 9 hours for zeolite A and 22.7% conversion in about 8 hours for zeolite C).

[0122] From the standpoint of stability, it is preferred that the mesopore volume is 0.265 mL / g (thus more than 200 mL / g, even more than 0.22 mL / g) and that the external surface area is advantageously between 35 and 55 m 2 / g, and even 45-50m 2Ferrierite B according to the present invention, with a Si / Al molar ratio of 12.5 and a Si / Al molar ratio of 12.5, provides the optimum conversion of isobutanol, as it converts 100% of isobutanol over 72 hours regardless of temperature and WHSV. This zeolite combines high initial and final conversions, selectivity for normal butenes that is improved and metastable over the test period compared to the other zeolites tested, and low deactivation (or even zero deactivation over 72 hours). Ferrierites C and D show little deactivation, but the initial conversion of isobutanol for these solids is less than 50% at 240°C.

[0123] Example 2: Testing the ability of the catalyst to capture nitrogen-containing compounds In this example, the feedstock is a 95 / 5 mass ratio mixture of isobutanol and water, containing 6 ppm of acetonitrile. The same equipment is used. The feedstock is vaporized at the top of the reactor in a SiC bed and then contacts the catalyst bed. Various catalysts were tested: zeolites A, B, C, D, E, and F as described in Example 1, and gamma alumina (see Table 6). Gamma alumina has a low total NH3 acidity (300 μmol / g). The catalyst preparation is as described in Example 1. The catalysts were tested under exactly the same conditions as in Example 1 (except for the presence of nitrogen-containing compounds).

[0124] The table below shows the nitrogen, carbon and hydrogen content of the different catalysts analyzed after 72 hours of reaction for the different catalysts tested:

[0125] [Table 5]

[0126] It is noted that zeolites A-F have nitrogen contents significantly higher than that measured for gamma alumina, from which it can be inferred that the zeolites capture at least a portion of the nitrogen impurities of the isobutanol feedstock.

[0127] Furthermore, the nitrogen contents of ferrierites A and B (0.115% and 0.212%, respectively) are higher than those of ferrierites C and D, which appear to be less than 0.10%. This indicates that the catalyst of the present invention, ferrierite B, has a significantly greater ability to capture nitrogen-containing compounds than the ferrierite zeolites used in prior art processes. [Brief explanation of the drawings]

[0128] [Figure 1] 1 shows a schematic representation of a crystal and the axis through which an electron microscope beam travels to calculate the size of the crystal. [Figure 2] 1 shows a scanning electron microscope (SEM) image of solid B according to the present invention. [Figure 3] 1 shows a scanning electron microscope (SEM) image of comparative solid C.

Claims

1. Formula R-CH ２ 1. A process for the isomerization dehydration of a feedstock comprising at least one primary monoalcohol of —OH, wherein R is a monoalcohol of the general formula C ｎ H ２ｎ＋１ wherein n is an integer from 3 to 20, and the process includes a vapor phase isomerization dehydration step carried out in the presence of a catalyst comprising at least one zeolite, at a weighted average temperature of 200 to 300°C, at a pressure of 0.1 to 1 MPa, and at a weight hourly space velocity (WHSV) of 1 to 25 h. －１ wherein the zeolite has at least one series of channels, the pore openings of the channels being defined by rings of eight oxygen atoms (8MR), and the mesopore volume is 0.10 mL / g or greater.

2. 2. The method of claim 1, wherein the zeolite has a Si / Al molar ratio of 5 to 45.

3. The external surface area of ​​the zeolite is 10 to 70 m ２ / g, preferably 20 to 65 m ２ / g, highly preferably 35 to 55 m ２ The method according to claim 1 or 2, wherein the saturation is 0.05 to 0.15 g.

4. The method according to any one of claims 1 to 3, wherein the micropore volume of the zeolite is from 0.100 to 0.150 mL / g.

5. The method according to any one of claims 1 to 4, wherein the zeolite also has a series of channels with openings of 10 oxygen atoms (10MR).

6. 6. The method of claim 5, wherein the zeolite is of structural type FER or MFS.

7. The method of claim 6, wherein the zeolite is ferrierite.

8. 8. The process according to any one of claims 1 to 7, wherein the feedstock comprises from 90% to 100% by weight of primary monoalcohol relative to the total weight of the feedstock.

9. 9. The method according to claim 1, wherein the primary monoalcohol is isobutanol.

10. The method of any one of claims 1 to 9, wherein the feedstock is derived from at least one lignocellulosic biomass fermentation process.

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