FR2994973A1 - PROCESS FOR THE PRODUCTION OF METHACRYLIC ACID - Google Patents

Abstract

The present invention relates to a process for synthesizing methacrylic acid consisting in a first charge-loading step comprising a compound of formula R-CH (CH) -CH OH where R is either CH OH (2-methyl-1) , 3-propanediol), or CHO (3-hydroxy-2-methyl-propanaldehyde) to a dehydration reaction, optionally in the presence of a dehydration catalyst, then in a second step to subject the first stage effluent to a oxidation reaction in the presence of an oxidation catalyst leading to methacrylic acid. The process according to the invention uses as raw material a co-product or an intermediate product of the 1,4-butanediol synthesis process by hydroformylation of the allyl alcohol.

Description

The present invention relates to a process for the synthesis of methacrylic acid from 2-methyl-1,3-propanediol. Processes for the synthesis of methacrylic acid, known for more than a century, were originally used as raw material cyanohydrin compounds. Firstly, ethylene cyanohydrin (2-cyanoethanol of formula CNCH 2 -CH 2 OH) was used, followed by cyanohydrin of acetone (2-cyano-2-propanol of formula CH 3 -C (CN) OH- CH3 also known as acetone cyanohydrin) which is the conventional method in the field.

For a description of this process, reference may be made to the techniques of the Engineer, Process Engineering Processes, J 6400 1-6. After the synthesis of acetone cyanohydrin by reaction of acetone on hydrogen cyanide, it is reacted with sulfuric acid, which gives rise by a strongly exothermic reaction to the formation of -oxyisobutyramide monosulfate, which is converted into sulfuric methacrylamide.

The latter is then hydrolysed to form methacrylic acid. In another form of the process via acetone cyanohydrin, illustrated by patent EP 407 811, the latter is hydrated to α-hydroxyisobutyramide [(H 3 C) (OH) (CH 3) C-CO-NH 2], which, reacting with methyl formate [H0000H3], produces methyl [(H3C) (OH) (CH3) -0000H3] ahydroxyisobutyrate which is dehydrated to methyl methacrylate yielding by hydrolysis with methacrylic acid. Methacrylic acid can also be obtained by transiting methacrolein as an intermediate product which is oxidized to methacrylic acid. Methacrolein can come from the oxidation of isobutylene (patent applications EP 1 994 978 and EP 1 995 231). It can also be obtained from propylene hydroformylated in the presence of hydrogen and carbon monoxide to form methacrolein precursor isobutyraldehyde (GB Patent 2,094,782). It can also be obtained by decomposition of the Mannich base of propionaldehyde, formaldehyde or dimethylamine. Finally, it is proposed in FR 2137827 to synthesize methacrolein from 2-methylene-1,3-propanediol. It has also been proposed in US Pat. No. 2,811,545 to use isobutane of natural gas as raw material. Isobutane is in a first step oxidized to isobutylene glycol of formula CH3-C (CH3) OH-CH2OH. In a second step isobutylene glycol is oxidized to yield 2-hydroxyisobutyric acid CH3-C (CH3) OH-COOH (or 2-hydroxy-2-methyl-propionic acid) which in a third step is dehydrated to methacrylic acid.

Very recently, it has been proposed a novel route of synthesis of methacrylic acid using as raw material 2-methyl-1,3-propanediol. An article by Sang-Hyun Pyo et al. was published on April 20, 2012 on the web by the Royal Society of Chemistry entitled "A new route for the synthesis of methacrylic acid from 2-methyl-1,3-propanediol by integrating biotransformation and catalytic dehydration".

In this paper, the authors describe a process in which in a first step 2-methyl-1,3-propanediol is oxidized by bio-conversion to 3-hydroxy-2-methyl-propionic acid via 3-hydroxy aldehyde. -2-methyl-propionic in the presence of a microorganism consisting of "Gluconobacter oxydans" cells carrying alcohol dehydrogenase (ADH) and aldehyde dehydrogenase (ALDH) enzymes. In the second step 3-hydroxy-2-methyl-propionic acid is dehydrated to methacrylic acid in the presence of a titanium dioxide catalyst. It is an object of the present invention to provide a novel process for the synthesis of methacrylic acid using as raw material 2-methyl-1,3-propanediol or 3-hydroxy-2-methyl-propanal (also referred to as 3-hydroxy -2-methylpropanaldehyde) which are, inter alia, a co-product or an intermediate product in the process of synthesizing 1,4-butanediol by hydroformylation of the allyl alcohol. This type of process must, to go to the industrial stage, be able to be implemented under conventional operating conditions. It differs from the usual processes by the use of a different raw material and naturally by a different reaction scheme. Moreover, this new process makes it possible to overcome the bioconversion step described above which poses delicate problems when looking for industrial productions. Indeed, the bioconversion stage requires specific investments and further leads to a salt because of the pH of the fermentation close to 7, which must then be converted back into acid, generally using sulfuric or hydrochloric acid. thus generating, stoichiometrically, as much salt as hydroxyisobutyric acid, to obtain the acid which must still be dehydrated in a specific plant using a heterogeneous catalyst.

The proposed new process combines a dehydration reaction and an oxidation reaction into a single industrial plant without the generation of inorganic salts. These reactions can be carried out in a single two-stage reactor or two consecutive reactors. The process of the invention differs from that of US Pat. No. 2,811,545 because of a different raw material, the choice of the oxidant used as well as the order of the steps, oxidation then dehydration in the case of US Pat. No. 2,811,545. The subject of the invention is thus a process for the synthesis of methacrylic acid consisting in a first charge-loading step comprising a compound of formula R-CH (CH 3) -CH 2 OH where R is either CH 2 OH (2-methyl-1, 3-propanediol), or CHO (3-hydroxy-2-methyl-propanaldehyde) to a dehydration reaction, optionally in the presence of a dehydration catalyst, then in a second step to subject the first-stage effluent to a reaction. oxidation in the presence of an oxidation catalyst leading to methacrylic acid.

The overall reaction scheme can be summarized as follows, depending on whether the reactive product is 2-methyl-1,3-propanediol, or 3-hydroxy-2-methyl-propanaldehyde: (1) CH2OH-C (CH3) H- CH2OH 4 CH2 = C (CH3) -CH2OH + H2O (2) CH2 = C (CH3) -CH2OH + O2 -) CH2 = C (CH3) -000H + H2O Or (1) CHO-C (CH3) H-CH2OH CH 2 = C (CH 3) -CHO + H 2 O (2) CH 2 = C (CH 3) -CHO +1/2 024 CH 2 = C (CH 3)-000H The operating conditions of the process are as follows: Step 1 dehydration is conducted at a temperature T such that 200 T 350 ° C, preferably between 250 and 320 ° C, and under a pressure of between 0.5 and 5 bar absolute, preferably between 1.5 and 3.5 bar absolute preferably in the presence of a solid acid catalyst. The term solid acid catalyst means a solid consisting of a porous material insoluble in the reaction medium having a specific surface area greater than 5 m 2 / g and preferably greater than 30 m 2 / g and having few basic surface such that the acidic solid catalyst has an adsorption of less than 20 micromole 502 / g.

The catalyst will generally be made from a substantially acidic solid material, which may optionally include basic sites due for example to surface impurities. It may also be manufactured from an amphoteric solid material comprising both acidic and basic sites, and even from a basic solid material. In the latter two cases, the materials will be treated so as to minimize (limit) the amount of basic surface sites. It is clear that those skilled in the art would be deterred from choosing in the dehydration process used in the process of the invention the latter two types of materials as catalyst without prior modifications. In order to obtain this partial or total elimination of the basic sites, the amphoteric or basic solid material will be subjected to cycles (contact with solutions of acidic precursors - neutralization acid base) / drying / calcination prior to the implementation of the catalyst in the process and also, if necessary, during the regeneration of the catalyst. The basicity of a material may be related to its composition, for example its crystalline structure or to surface defects such as the presence of impurities such as alkali or alkaline earth metals. The presence of basic sites and their amounts can be determined by any known method, for example by adsorption of an acid compound such as CO2 or SO2 and by micro-calorimetric measurements of the adsorption energy. The presence of acid sites and their amounts can in turn be measured by adsorption of a basic compound such as ammonia for example. As examples of basic or amphoteric materials that can be used in the process of the invention, mention may be made of mixed oxides such as zirconium / lanthanum oxide, metal hydroxides such as hydroxyapatite or lamellar hydroxides such as hydrotalcites. Using the SO 2 adsorption method, the materials considered basic or amphoteric are those achieving adsorption greater than 20 micromoles SO 2 / g.

When the material used is an acid but having basic sites (amphoteric or acidic solids with basic impurities), the acidity can be measured by NH3 adsorption or the Hammett acidity measurement method.

The amphoteric or basic materials, modified by impregnation of acid compounds, neutralizing all or part of the basic contribution of the solid material, which are suitable are homogeneous or multiphase materials, insoluble in the reaction medium, which have an adsorption of less than 20 micromole SO 2 / g , an ammonia adsorption of greater than 20 micromoles of NH 3 / g and preferably greater than 100 micromoles / g of NH 3 / g, or have a Hammett acidity, denoted H 0, as indicated in US Pat. No. 5,387,720 which refers to paper by K. Tanabe et al in "Studies in Surface Science and Catalysis", Vol 51, 1989, Chapters 1 and 2, Hammett's acidity is determined by amine titration using indicators or by adsorption of a base in the gas phase. The materials at the base of these catalysts can be chosen from natural or acidic siliceous materials, acidic zeolites, inorganic supports, such as oxides, coated with inorganic acids, mono, di, tri or polyacids, oxides. or mixed oxides, often basic or amphoteric, which can also be covered by inorganic acids, mono, di, tri or polyacids or (preferably) hetero-polyacids or hetero-polyacids salts solid catalyst hetero-polyacids which can themselves be deposited on supports. These catalysts may be constituted by a heteropoly acid salt in which protons of said heteropoly acid are exchanged with at least one cation selected from the elements belonging to Groups 1 to 16 of the Periodic Table of Elements, these heteropoly acid salts containing at least one element chosen from the group comprising VV, Mo and V. Among the mixed oxides, mention may be made especially of those based on iron and phosphorus, those based on vanadium and phosphorus, those based on aluminum and phosphorus, boron and phosphorus, phosphorus or silicon and tungsten and those containing cesium, phosphorus and tungsten. The catalysts may in particular be chosen from zeolites, Neon® composites (based on fluorinated polymers sulphonic acid), chlorinated aluminas, acids and salts of phosphotungstic and / or silicotungstic acids, and various solids of the metal oxide type. such as tantalum oxide Ta205, niobium oxide Nb205, alumina A1203, titanium oxide TiO2, zirconia ZrO2, tin oxide 5nO2, silica 5iO2 or silicoaluminate 5iO2-Al2O3, impregnated with acidic functions such as borate B03, sulfate SO4 , WO03 tungstate, PO4 phosphate, SiO2 silicate or Mo03 molybdate or a mixture of these compounds. The foregoing catalysts may further comprise a metal promoter such as Au, Ag, Cu, Pt, Rh, Pd, Ru, Sm, Ce, Yt, Sc, La, Zn, Mg, Fe, Co, Ni.

The preferred catalysts are zirconium phosphates, tungsten zirconias, zirconia silicones, titanium, zirconium, aluminum or tin oxides impregnated with tungstate, silicotungstate or phosphotungstate, phosphated aluminas or silicas, heteropolyacids or sodium salts. heteropolyacids, iron phosphates and iron phosphates comprising a promoter, mixed vanadium-phosphorus oxides. The oxidation stage 2 is carried out in the gaseous phase using oxygen as an oxidizing agent at a temperature of between 200 and 350 ° C. under a pressure of between 0.5 and 5 bar absolute, preferably between 1 and 3. bars, and in the presence of solid oxidation catalysts, especially in the presence of solid catalysts containing Mo as the main active element. The oxidation catalysts that can be used in the process of the invention will comprise molybdenum and at least one element chosen from P, Si, VV, Ti, V, Nb, Ta, Cr, Mn, Fe, Co, Ni, Cu, Zn. , Ga, In, Tl, Sb, Ag, As, Ge, B, Bi, La, Ba, Sb, Ce Te, Pb, selected from the group consisting of mixed oxides containing molybdenum and heteropolyacids containing molybdenum. These catalysts may be represented by the following general formula. Wherein A is at least one cation selected from Groups 1 to 16 of the Periodic Table of Elements and the lanthanides, preferably a cation of an alkali metal such as Cs, Rb or K, X is P or Si and preferably PZ is at least one member selected from the group consisting of VV, Ti, Zr, V, Nb, Ta, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, In, Tl, Sn, Ag, As, Ge, B, Bi, La, Ba, Sb, Te, Ce and Pb and preferably Cu, Fe, Bi, Co, Ni, VV, V, Cr, Sb, Mn, Ce, 0 is oxygen a, b, c and d are indices consisting of integers or decimals satisfying the following ranges 0 to 9 and preferably 0 <a 9 0 b 2 and preferably 0.1 b 1.5 0 <c 12 and preferably 5 <c 12 0 d 12 and preferably 0 <d 4 such that a + b + d> 0, and e is a number determined by the total degree of oxidation of the elements. The catalyst used during this oxidation step may be a type of catalyst Fe-Mo-0 doped or not generally used during the oxidation of methanol to formaldehyde. Examples of iron molybdate catalysts (Fe-Mo-O) are described in Catalysis Review, Vol 47 (2004), pp 125-174. These catalysts are commercially available. For example, Süd Chemie supplies several grades of these catalysts under the FAMAX® brand name: FAMAX J5, FAMAX MS, FAMAX HS, FAMAX TH.

The propylene oxidation catalysts could be used as described in patents EP 900774, EP 1125911, EP 1987877, EP1074938, US Pat. No. 6,268,529 and US Pat. No. 4,837,940. The catalyst then comprises molybdenum and at least one element selected from P, Si, VV, Cr, Mn, Fe, Co, Ni, Bi, Sb, Ce. Examples of particularly effective catalysts are mixed oxides and heteropoly acid salts each based on FeMo, CsPMo, CsPVVMo. The solid catalysts that can be used in this step of the process can be prepared from techniques well known to those skilled in the art, for example those described in application VVO 09/128555 (heteropolyacids) or in "Catalysis Review, Vol 47 ( 2004), pp. 125-174 "and references thereto.

The solid component of the catalyst thus obtained is then generally calcined before being used in the process. The calcination may be carried out in air or under an inert gas such as nitrogen, helium and argon or in a mixed atmosphere of oxygen and an inert gas. This calcination is usually conducted in an oven such as a muffle furnace, a rotary kiln or a fluidized bed furnace. The combustion temperature is generally between 150 and 900 ° C, preferably between 200 and 800 ° C and more preferably between 200 and 600 ° C. The duration of the calcination is generally between 0.5 and 10 h. The oxidation catalysts may be in bulk form and used in this case without support. The catalysts can also be deposited on an inactive support whose amount represents from 30 to 90% and preferably at least 50% of the total weight of the catalyst.

It is possible to use as support any material such as silica, alumina, magnesia, titania, zirconia, silicon carbide, silicates, diatomaceous earths, borates or carbonates provided that the materials are stable to the operating conditions to which the catalysts are subjected. The bulk catalyst or the supported catalyst may be in the form of a granule or powder and may be in any form such as sphere, grain, trilobe and quadrilobe hollow cylinders, and in the form of cylinders, extruded or compressed optionally using a pelletizing agent. The particle size will be, for example, 0.1 to 10 mm for use in a fixed bed and less than 1 mm for a fluidized bed.

Preferably, catalysts supported for the second step of the process according to the invention are used. The following examples illustrate the present invention without, however, limiting its scope.

Example 1 Manufacture of Methacrylic Acid from 2-Methyl-1,3-Propanediol The catalysts used in this example are as follows: For the first step, a tungsten zirconia (90.7% ZrO 2 -9.3% WO 3) from Daiichi Kigenso (supplier reference H1417) is used. The catalyst has a loss on ignition at 1000 ° C of 1.75% and a specific surface area of 47.4 m 2 / g (BET, 1 point). The catalyst of step 2 is prepared according to the method described below: In 1000 ml of deionized water, 167 g of molybdenum oxide, 7.37 g of vanadium pentoxide and 14.675 g of acid are added. 85% phosphoric, and the solution is refluxed (90-100 ° C) for 5 hours, to obtain a clear dark red solution. Then 5.06 g of antimony trioxide was added and refluxing was continued at 90-100 ° C for 2 hours to dissolve the antimony trioxide. During this step, a succession of redox reactions takes place during which the oxidation states of the different elements adjust each other. It operates in an inert atmosphere of nitrogen. The resulting solution is a very dark blue. Then the solution is cooled to room temperature. To the resulting solution is added a solution of cesium acetate containing 11.11 g of Cs acetate in 120 ml of pure water and a solution of 12.85 g of ammonium acetate in 120 ml of water. pure while maintaining vigorous agitation. A suspension is formed, to which a solution containing 9.25 g of cupric acetate in 140 ml of pure water is added. The resulting suspension is left to mature for 1 hour at room temperature with stirring. She takes a blue-green color. Finally, the water is evaporated in a water bath to obtain a solid, which will be calcined under a stream of air at 310 ° C. for 5 hours. The solid obtained has the following molar composition Mo / V / P / Cu / Sb / Cs: 10 / 0.7 / 1.1 / 0.4 / 0.3 / 0.5. The measurements of the acidity and the basicity of the catalyst were carried out by adsorption of SO2 (basicity) and NH3 (acidity) and by micro-calorimetric measurements of the adsorption energy. The operating conditions were as follows. The tests were carried out at 150 ° C. in a calorimeter (Setaram 080) connected to a conventional volumetric apparatus equipped with a Barocel capacitive pressure gauge for pressure measurements. The samples were pretreated in a quartz cell by heating overnight under vacuum at 300 ° C. This temperature was reached by increasing the temperature at a rate of 1 ° C / min. The differential adsorption heats were measured as a function of the repetitive rate of recovery of small doses of the respective gases on the sample until an equilibrium pressure of about 67 Pa was reached. The sample was degassed for 30 minutes. at the same temperature and a second similar adsorption series was carried out until an equilibrium pressure of about 27 Pa was reached. The difference between the amounts adsorbed between the first and second adsorption (at 27 Pa) represents the irreversibly adsorbed amount of the respective gases which provides an estimate of the number of strong sites respectively acid or base.

The process according to the invention is carried out according to the following procedure: Two series reactors 2.54 cm in diameter and 1 m long immersed in baths of molten salt at temperatures of 300 and 315 ° C respectively are fed with a VVH of 1000 h -1 with a mixture of O 2/2-methyl-1,3-propanediol / H 2 O / N 2 in the molar proportions 2/1/10/12 (the reactor is supplied with a 30% aqueous solution). % by weight of 2-methyl-1,3-propanediol). The first reactor is charged with Daiichi Kigenso tungsten zirconia, having an acidity of 150 micromoles of ammonia per gram, and a basicity of 17 micromoles of SO 2 per gram, and the second of the MoN / P / Cu / Sb / Cs catalyst. described above. The hot spot in the second catalyst bed reaches 330 ° C.

After 3 hours of operation, the conversion of 2-methyl-1,3-propanediol is 99%, and the yield of methacrylic acid is 37.5%. Example 2 Manufacture of methacrylic acid from 2-methyl-1,3-propanediol without a first-stage catalyst. The procedure is as above, but in the absence of catalyst for the first step. This catalyst is replaced by chemically inert steatite beads. The contact time in the steatite bead zone maintained at 275 ° C. is 20 seconds. The yield of methacrylic acid is 24%.

Claims (12)

1) A process for synthesizing methacrylic acid consisting in a first charge-loading step comprising a compound of formula R-CH (CH 3) -CH 2 OH wherein R is either CH 2 OH (2-methyl-1,3-propanediol) or CHO (3-hydroxy-2-methylpropanaldehyde) to a dehydration reaction, optionally in the presence of a dehydration catalyst, then in a second step to subject the first stage effluent to an oxidation reaction in the presence of an oxidation catalyst leading to methacrylic acid. 2) Process according to claim 1 characterized in that the dehydration step is conducted at a temperature T such that 200 T 350 ° C, preferably between 250 and 320 ° C and at a pressure between 0.5 and 5 bar absolute, preferably between 1.5 and 3.5 bar absolute. 3) Process according to claim 1 or 2 characterized in that the dehydration reaction is carried out in the presence of a solid catalyst of acid type. 4) Process according to one of the preceding claims characterized in that the dehydration catalyst consists of a porous material insoluble in the reaction medium having a specific surface greater than 5 m 2 / g and preferably greater than 30 m 2 / g and having few basic surface sites such that the solid acid-type catalyst has an adsorption of less than 20 micromoles SO 2 / g and an adsorption of ammonia greater than 20 micromoles NH 3 / g and preferably greater than 100 micromoles NH 3 / g . 5) Method according to one of the preceding claims characterized in that the catalyst is selected from zeolites, Neon® composites (based on sulfonic acid fluoropolymers), chlorinated aluminas, acids and salts of phosphotungstic acids and / or silicotungstics, and various metal oxide solids such as tantalum oxide Ta205, niobium oxide Nb205, alumina A1203, titanium oxide TiO 2, zirconia ZrO 2, tin oxide SnO 2, silica SiO 2 or silicoaluminate SiO 2 -Al 2 O 3, impregnated acid functions such as borate B03, sulfate SO4, tungstate WO3, phosphate PO4, silicate SiO2 or molybdate MoO3 or a mixture of these compounds. 6) Method according to one of the preceding claims characterized in that the catalyst is selected from phosphated zirconia, tungsten zirconia, zirconia silicones, titanium oxides, zirconium, aluminum or tin impregnated with tungstate, silicotungstate or phosphotungstate, phosphated aluminas or silicas, heteropolyacids or heteropolyacid salts, iron phosphates and iron phosphates comprising a promoter, vanadium-phosphorus mixed oxides. 7) Method according to one of the preceding claims characterized in that the oxidation step is conducted in the gas phase using oxygen as an oxidizing agent at a temperature between 200 and 350 ° C under a pressure between 0 , 5 and 5 absolute bar, preferably between 1 and 3 bar. 8) Method according to one of the preceding claims characterized in that the oxidation step is conducted in the presence of solid oxidation catalysts containing Mo as the main active element. 9) Method according to one of the preceding claims characterized in that the oxidation catalysts comprise molybdenum and at least one element selected from P, Si, VV, Ti, V, Nb, Ta, Cr, Mn, Fe, Co , Ni, Cu, Zn, Ga, In, Tl, Sb, Ag, As, Ge, B, Bi, La, Ba, Sb, Ce Te, Pb, in the form of mixed oxides containing molybdenum or d heteropolyacids containing molybdenum. 10) Method according to one of the preceding claims characterized in that the oxidation catalysts can be represented by the following general formula. A, Xb MO c Zd Oe A is at least one cation selected from the elements of Groups 1 to 16 of the Periodic Table of Elements and the lanthanides, preferably an alkali metal cation such as Cs, Rb or K, X is P or Si and preferably PZ is at least one member selected from the group consisting of VV, Ti, Zr, V, Nb, Ta, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, In, Tl , Sn, Ag, As, Ge, B, Bi, La, Ba, Sb, Te, Ce and Pb and preferably Cu, Fe, Bi, Co, Ni, VV, V, Cr, Sb, Mn, Ce, 0 is oxygen a, b, c and d are indices consisting of integers or decimals satisfying the following ranges 0 to 9 and preferably 0 <a 9 0 b 2 and preferably 0.1 b 1.5 0 <c 12 and preferably 5 <c 12 0 d 12 and preferably 0 <d 4 such that a + b + d> 0 and e is a number determined by the total degree of oxidation of the elements. 11) Method according to one of the preceding claims characterized in that the oxidation catalysts are used in bulk form. 12) Method according to one of the preceding claims characterized in that the oxidation catalysts are deposited on a support whose amount is from 30 to 90% and preferably at least 50% of the total weight of the catalyst.