Process for the production of carboxylic acids.

The invention relates to a process for the preparation of carboxylic acids from olefins by catalytic carbonylation and hydration in the presence of zeolites as catalysts.

Among the carboxylic acids, the neocarboxylic acids are of great importance in chemical engineering. Neopentanoic acid (pivalic acid) is further processed, for example, to give tert-butyl peroxipivalate, which is widely used as a polymerization initiator for styrene, vinyl chloride and vinyl acetate.

Low molecular weight monoesters of neocarboxylic acids can be used as scents in detergents, and the polyesters in lubricating oils. The esters also serve as solvents. Neocarboxylic acids also have biological activity in the prevention of putrefaction, eg neodecanoic acid as a worm control agent.

The production of carboxylic acids by reacting olefins with a C number lower by 1 than the desired carboxylic acid with carbon monoxide in the presence of mineral acids, Lewis acids, "super acids", metal carbonyls or metal complexes as catalysts with subsequent hydrolytic workup of the reaction mixture is known. The use of conc. Sulfuric acid, phosphoric acid, hydrofluoric acid or boron fluoride as catalysts is described in DE-PS 942 987, US-PS 2 876 241, US 3 167 585, US 3 282 993 and GB 1 174 209. Pd complexes (DE-PS 2 124 718 and EP-PS 55 875), rhodium and iridium complexes (US Pat. No. 3,637,833), tungsten and molybdenum-nickel complexes (GB.) Are used as metal complex catalysts -PS 2 099 430) and cobalt carbonyls (DE-PS 2 503 996). All these known processes have in common that they are carried out homogeneously catalytically and in two stages.

In US Pat. No. 3,733,362 the carbonylation of 2 to 6 C-olefins is protected in the gas phase. The catalyst used here is a metal of the 8th main group complexed with, for example, phosphorus or arsenic ligands, this original homogeneous catalyst being heterogenized by application to SiO₂ or Al₂O₃.

The essential by-products in this reaction are oligomers of the olefins used, higher acids by carbonylation and hydration of the oligomers and carboxylic acid esters by reaction of the acids formed with olefins.

The disadvantages associated with the homogeneous production method result from the difficulties in separating and disposing of the catalyst.

When using metal complex catalysts, special measures must be taken due to their toxicity, and the thermal stability and thus activity of these catalysts is only given in a narrow temperature range.

The invention relates to a process for the preparation of carboxylic acids of the formula<chemistry id="chem0001" num="0001"><img file="EP0249976A1_D0001.tif" /></chemistry> in which R¹ to R⁴ alkyl and / or alkenyl radicals having 1 to 12 carbon atoms and / or aryl and / or aralkyl radicals, which in turn may be substituted or R³ and R⁴ are hydrogen or R¹ and R³ are part of a cyclic system, by Implementation of olefins of the formula<chemistry id="chem0002" num="0002"><img file="EP0249976A1_D0002.tif" /></chemistry> in which R¹ to R⁴ have the meaning given above, with CO and H₂O in the presence of zeolites as catalysts.

The disadvantages described above can be avoided by the process according to the invention, in particular when the reaction is carried out in the gas phase or under supercritical conditions.

Examples of olefins are isobutene, 2-methylbutene-1, 2-methylbutene-2, 2-methylpentene-1, 2-methylpentene-2, 2,4-dimethylbutene-2, 2-methylhexene-1, 2-methyloctene-1 , 2-methylnonen-1, 2-methyldecene-1, 2,4,4-trimethylpentene-1, 2,4,4-trimethylpentene-2, cyclopentene, cyclohexene, 1-methylcyclopentene, 1-methylcyclohexene, 1,4-dimethylcyclopentene , 1,4-dimethylcyclohexene, 1,3-dimethylcycloheptene, 1-methyl-4-phenyl-cyclohexene, 1-methyl-4-benzyl-cyclohexene, α-methylstyrene, Use 1-phenyl-2-methylpropene-1 or 1,1-diphenylethene.

Acidic zeolitic catalysts are suitable as catalysts. Zeolites are crystalline aluminosilicates, which have a highly ordered structure with a rigid three-dimensional network of SiO₄ and AlO₄ tetrahedra, which are connected by common oxygen atoms. The ratio of Si and Al atoms to oxygen is 1: 2. The electrovalence of the tetrahedra containing aluminum is compensated for by the inclusion of cations in the crystal, for example an alkali metal or hydrogen ion. A cation exchange is possible. The spaces between the tetrahedra are occupied by drying or calcining water molecules before dehydration.

According to their structure, zeolites are divided into different groups. In the case of the mordenite group, chains or in the case of the chabasite group, layers of tetrahedra form the zeolite structure, while in the faujasite group the tetrahedra are arranged in polyhedra, for example in the form of a cubo-octahedron which is built up from four rings or six rings. Depending on the connection of the cubo-octahedron, which creates voids and pores of different sizes, a distinction is made in zeolites of type A, L, X or Y.

In the zeolite, other elements such as B, Ga, Fe, Cr, V, As, Sb or Be can be built into the lattice instead of aluminum, or the silicon can be replaced by a tetravalent element such as Ge, Ti, Zr, Hf .

Zeolites from the mordenite group or narrow-pore zeolites of the erionite or chabasite type or zeolites of the faujasite type, for example Y-, X- or L-zeolites, are suitable as catalysts for the process according to the invention. The so-called "ultra-stable" zeolites of the faujasite type, ie dealumized zeolites, also belong to this group of zeolites. Methods for producing such zeolites are described, for example, in US Pat. No. 4,512,961.

Zeolites of the pentasil type are used particularly advantageously. As a basic building block, they share a five-membered ring made of SiO T tetrahedra. They are characterized by a high SiO₂ / Al₂O₃ ratio and by pore sizes between those of type A zeolites and those of type X or Y. These zeolites can have different chemical compositions. These are alumino, boro, iron, beryllium, gallium, chromium, arsenic, antimony and bismuth silicate zeolites or their mixtures, as well as alumino, boro, gallium and iron germanate zeolites or their mixtures.

The alumino, borosilicate or iron silicate zeolites of the pentasil type are particularly suitable for the process according to the invention. The aluminosilicate zeolite is, for example from an aluminum compound, preferably Al (OH) ₃ or Al₂ (SO₄) ₃ and a silicon component, preferably highly disperse silicon dioxide in aqueous amine solution, in particular in polyamine, such as 1,6-hexanediamine or 1,3-propanediamine or triethylene tetramine solution with or in particular without addition of alkali or alkaline earth at 100 to 220 ° C under autogenous pressure. The aluminosilicate zeolites obtained contain, depending on the choice, an SiO₂ / Al₂O₃ ratio of 10 to 40,000. This also includes the isotactic aluminosilicate zeolites as described in DE-OS 30 06 471, EP 34727. Such aluminosilicate zeolites can also be synthesized in an ethereal medium such as diethylene glycol dimethyl ester, in an alcoholic medium such as methanol or 1,4-butanediol or in water.

The borosilicate zeolites can be synthesized, for example, at 90 to 200 ° C. under autogenous pressure by using a boron compound, for example H₃BO₃, with a silicon compound, preferably highly disperse silicon dioxide in aqueous amine solution, especially in 1,6-hexanediamine or 1,3-propanediamine. or triethylenetetramine solution with and in particular without addition of alkali or alkaline earth metal to react. Borosilicate zeolites are also obtained if the reaction is carried out in an ethereal solution, for example diethylene glycol dimethyl ether or in an alcoholic solution, for example 1,6-hexanediol, instead of in an aqueous amine solution.

The iron silicate zeolite is obtained, for example, from an iron compound, preferably Fe₂ (SO₄) ₃ and a silicon compound, preferably highly disperse silicon dioxide in aqueous amine solution, in particular 1,6-hexanediamine, with or without the addition of alkali metal or alkaline earth metal at 100 to 200 ° C. under autogenous pressure.

The silicon-rich zeolites used (SiO₂ / Al₂O₃ ≧ 10) include, for example, the following types: ZSM, ferrierite and NU-1, as crystalline zeolites and Silicalite® as a molecular sieve, a so-called silica polymorph, which is detailed in US Pat. No. 4,061,724 is described.

The alumino, borosilicate and iron silicate zeolites thus produced can, after their isolation, drying at 100 to 160 ° C., preferably 110 ° C. and calcination at 450 to 550 ° C., preferably 500 ° C., with a binder in a ratio of 90:10 to 40:60% by weight to be shaped into strands or tablets. Various aluminum oxides, preferably boehmite, amorphous aluminosilicates with an SiO₂ / Al₂O₃ ratio of 25:75 to 90: 5, preferably 75:25, silicon dioxide, preferably highly disperse SiO₂, mixtures of highly disperse SiO₂ and highly disperse Al₂O₃ and clay are suitable as binders. After shaping, the extrudates or compacts are dried at 110 ° C / 16 g and calcined at 500 ° C / 16 h.

Advantageous catalysts are also obtained if the isolated aluminum or. Borosilicate zeolite is deformed immediately after drying and is only subjected to calcination after the deformation. The alumino and borosilicate zeolites produced can be used in pure form, without binders, as strands or tablets, with extrusion or peptizing aids, for example Ethyl cellulose, stearic acid, potato starch, formic acid, oxalic acid, acetic acid, nitric acid, ammonia, amines, silicic acid esters and graphite or mixtures thereof can be used.

If the zeolite is not in the catalytically active, acidic H form but, for example, in the Na form due to the nature of its production, then this can be completely or partially converted into the desired form by ion exchange, for example with ammonium ions and subsequent calcination or by treatment with acids H-shape can be transferred. If, when using the zeolitic catalysts, a deactivation due to coke separation occurs, it is advisable to regenerate the zeolites by burning off the coke deposit with air or with an air / N₂ mixture at 400 to 550 ° C, preferably 500 ° C . This gives the zeolites their initial activity. By partial coking (pre-coke) it is possible to adjust the activity of the catalyst for an optimal selectivity of the desired reaction product.

In order to achieve the highest possible selectivity, high turnover and long service life, it is advantageous to modify the zeolites. A suitable modification of the catalysts is, for example, that the undeformed or deformed zeolite is doped with metal salts by ion exchange or by impregnation. The following metals are used: alkali metals such as Li, K, Cs, alkaline earth metals such as Be, Mg, Ca, metals of the 3rd, 4th and 5th Main group such as Ga, Ge, Sn, Pb, Bi, transition metals of the 4th to 8th subgroup such as Ti, Zr, V, Nb, Cr, Mo, W, Mn, Re, Fe, Ru, Os, Co, Rh, Sr , Ni, Pd, Pt, transition metals of subgroups 1 and 2 such as Cu, Ag, Zn and rare earth metals such as Ce, La, Pr, Nd, Dy, Yb, Lu, Er and U.

The doping is expediently carried out in such a way that, for example, the deformed zeolite is placed in a riser tube and, for example, an aqueous or ammoniacal solution of a halide or a nitrate of the above-described metals is passed at 20 to 100 ° C. Such an ion exchange can be carried out, for example, on the hydrogen, ammonium and alkali form of the zeolite. A further possibility of applying metal to the zeolite is given by impregnating the zeolitic material with, for example, a halide, a nitrate or an oxide of the above-described metals in aqueous, alcoholic or ammoniacal solution. Both an ion exchange and an impregnation are followed by at least one drying step, optionally a further calcination.

A possible embodiment is, for example, that Cu (NO₃) ₂ × 3 H₂O or Co (NO₃) ₂ × 6 H₂O or Ce (NO₃) ₃ × 6 H₂O or La (NO₃) ₃ × 6 H₂O or Cs₂CO₃ is dissolved in water. With this solution, the deformed or undeformed zeolite is soaked for a certain time, about 30 minutes. Any excess solution is freed of water on the rotary evaporator. The impregnated zeolite is then dried at about 150 ° C. and calcined at 550 ° C. This impregnation process can be carried out several times in succession to set the desired metal content.

It is also possible, for example, to produce an aqueous Co (NO₃) ₂ solution or ammoniacal Pd (NO₃) ₂ solution and to slurry the pure powdered zeolite at 40 to 100 ° C. with stirring for about 24 hours. After filtering off, drying at about 150 ° C. and calcining at about 500 ° C., the zeolitic material obtained in this way can be processed further with strands, pellets or fluidized material with or without a binder.

An ion exchange of the zeolites present in the H form or ammonium form or alkali form can be carried out in such a way that the zeolites are introduced in strands or pellets in a column and an aqueous Co (NO₃) ₂ solution or ammoniacal Pd ( NO₃) ₂ solution at a slightly elevated temperature between 30 and 80 ° C in the circuit for 15 to 20 h. It is then washed out with water, dried at approximately 150 ° C. and calcined at approximately 550 ° C.

In the case of some metal-doped zeolites, for example in the case of Pd-, Cu-, Ni-doped zeolites, an aftertreatment with hydrogen is advantageous.

Another possibility of modification consists in subjecting the zeolitic material - deformed or undeformed - to treatment with acids such as hydrochloric acid, hydrofluoric acid and phosphoric acid and / or water vapor. The procedure is advantageously such that zeolites in powder form are treated with 1N phosphoric acid at 80 ° C. for 1 hour. After the treatment, it is washed with water, dried at 110 ° C. for 16 hours and calcined at 500 ° C. for 20 hours. According to another procedure, zeolites are treated with binders before or after their shaping, for example for 1 to 3 hours at temperatures from 60 to 80 ° C. with a 3 to 25% by weight, in particular 12 to 20% by weight, aqueous hydrochloric acid. The zeolite thus treated is then washed with water, dried and calcined at 400 to 500 ° C.

A particular embodiment for the acid treatment consists in that the zeolitic material is deformed with hydrofluoric acid before it is deformed at elevated temperature, generally from 0.001 n to 2 n, preferably from 0.05 n to 0.5 n, by heating under reflux for a period of time from 0.5 to 5, preferably 1 to 3 hours. After isolation of the zeolitic material, e.g. by filtering and washing out, it is expediently dried at temperatures from 100 to 160 ° C. and calcined at temperatures from 450 to 600 ° C. Another preferred embodiment for the acid treatment consists in the zeolitic material being deformed with binder at temperatures of 50 to 90 ° C., preferably 60 to 80 ° C., for a period of 0.5 to 5, preferably 1 to 3 Hours with 3 to 25 wt .-% hydrochloric acid treated. The zeolitic material can then be washed out, dried at 100 to 160 ° C and calcined at 450 to 600 ° C. According to a different procedure, zeolites can be modified by applying phosphorus compounds such as trimethyl phosphate, trimethoxyphosphine, primary, secondary or tertiary sodium phosphate. Treatment with primary sodium phosphate has proven to be advantageous. Here, the zeolites are in the form of strands, tablets or fluidized materials, for example impregnated with aqueous NaH₂PO₄ solution, dried at 110 ° C and calcined at 500 ° C.

In general, the catalysts can optionally be used as strands of 2 to 4 mm in length, as tablets with 3 to 5 mm in diameter or as fluidized material with a particle size of 0.05 to 0.5 mm. The fluidized material can be produced, for example, by crushing and screening strands or by spray drying.

The inventive reaction of the olefins with CO and H₂O is preferably carried out in the gas phase or in the supercritical range and generally at 50 to 500 ° C, preferably 200 to 400 ° C and a pressure of 10 to 700 bar, preferably 200 to 500 bar . The molar ratio of olefins to CO and to H₂O can be between 1: 1: 1 and 1:10:10, in particular between 1: 2: 2 and 1: 6: 6, the ratio of CO to H₂O also varying within these limits can. The load WHSV can be chosen between 0.1 and 40 h⁻¹, preferably 0.5 to 5 h⁻¹ (g olefin / g catalyst and h).

It is also possible to carry out the reaction in the liquid phase, for example in suspension, trickle or bottoms mode.

Non-volatile or solid starting materials are used in dissolved form, for example in THF, toluene or petroleum ether solution. In general, the starting materials can be diluted with solvents or inert gases such as N₂, Ar.

The reaction products can be worked up and isolated in a manner known per se, for example by distillation. Unreacted olefins, CO and H₂O can be separated off and used again for the reaction according to the invention.

Examples

The batchwise production of the carboxylic acids is carried out in a stirred autoclave with a filling volume of 300 ml. The catalyst is initially introduced together with water and then the olefin and carbon monoxide are pumped in. After heating to the desired reaction temperature, carbon monoxide is injected to the desired pressure. The reaction conditions are given in Examples 1 to 4, and the work-up and further characterization are carried out as described above.

The continuous production of the carboxylic acids is carried out in a high-pressure tubular reactor (6 mm inside diameter, 1 m length). The olefin is fed into the reactor via a high pressure pump. At the same time, water is added separately at the reactor inlet using a second high-pressure pump or carbon monoxide (gaseous). The reaction conditions are given in the individual tables. The reaction product is relaxed, separated and characterized as indicated. The quantitative determination of the reaction products and the starting materials is carried out by gas chromatography.

Catalyst A

A borosilicate zeolite of the pentasil type is in a hydrothermal synthesis from 640 g of highly disperse SiO₂, 122 g of H₃BO₃, 8000 g of an aqueous 1,6-hexanediamine solution (mixture 50:50 wt.%) At 170 ° C under autogenous pressure in one Stirred autoclaves manufactured. After filtering off and washing out, the crystalline reaction product is dried at 100 ° C./24 h and calcined at 500 ° C./24 h. This borosilicate zeolite is composed of 94.2 wt.% SiO₂ and 2.3 wt.% B₂O₃.

2 mm strands are produced from this material by shaping with a shaping aid, which are dried at 110 ° C./16 h and calcined at 500 ° C./24 h.

Catalyst B

Catalyst B is obtained by shaping the borosilicate zeolite (cf. Catalyst A) with boehmite (weight ratio 60:40) into 2 mm strands which are dried at 110 ° C./16 h and calcined at 500 ° C./16 h.

Catalyst C

An aluminosilicate zeolite of the pentasil type is under hydrothermal conditions at autogenous pressure and 150 ° C from 650 g of highly disperse SiO₂, 203 g Al₂ (SO₄) ₃ × 18 H₂O and 10 kg of an aqueous 1,6-hexanediamine solution (mixture 50:50 % By weight) in a stirred autoclave. After filtering off and washing out, the crystalline reaction product is dried at 110 ° C./24 h and calcined at 500 ° C./24 h. This aluminosilicate zeolite contains 91.6 wt.% SiO₂ and 4.6 wt.% Al₂O₃. The catalyst is shaped into 2 mm strands with a shaping aid, dried at 110 ° C./16 h and calcined at 500 ° C./24 h.

Catalyst D

An iron silicate zeolite of the pentasil type is dissolved under hydrothermal conditions at autogenous pressure and 165 ° C. from 273 g of water glass, dissolved in 253 g of an aqueous 1,6-hexanediamine solution (mixture 50:50% by weight) and 31 g of iron sulfate synthesized in 21 g of 96% sulfuric acid and 425 g of water in a stirred autoclave for 4 days. The zeolite is filtered off, washed out, dried at 100 ° C./24 h and calcined at 500 ° C./24 h. An iron silicate zeolite with an SiO₂ / Fe₂O₃ ratio of 17.7 and an Na₂O content of 1.2% by weight is obtained. The zeolite is extruded with highly disperse SiO₂ in a weight ratio of 80:20 to 2.5 mm strands, dried at 110 ° C / 16 h and calcined at 500 ° C / 24 h.

Catalyst E

The catalyst is produced from iron silicate zeolite, such as catalyst D, by shaping with shaping aids into strands and subsequent calcination at 500 ° C./16 h. The strands are subjected to an ion exchange with a 20% aqueous NH₄Cl solution at 80 ° C, dried and calcined at 500 ° C / 24 h. The process is repeated several times until the Na content of the catalyst has dropped below 0.03% by weight.

Catalyst F

The catalyst is prepared like catalyst C, but the 1,6-hexanediamine is replaced by 1,3-propanediamine. The aluminosilicate zeolite obtained contains 90.6 wt.% SiO₂ and 3.4 wt.% Al₂O₃.

The powder obtained is shaped with boehmite in a weight ratio of 60:40, dried at 110 ° C./16 h and calcined at 500 ° C./24 h.

Catalyst G

Catalyst G is prepared by impregnating catalyst B with aqueous Cr (NO₃) ₃ solution, drying at 130 ° C / 2 h and calcining at 540 ° C / 2 h. The Cr content is 2.8% by weight.

Catalyst H

like catalyst G, only Cu (NO₃) ₂ solution. The Cu content is 3.5% by weight.

Catalyst I

like catalyst G, only Cu (NO₃) ₂ solution. The Cu content is 1.4% by weight.

Catalyst J.

Catalyst J is prepared by impregnating catalyst A with aqueous La (NO₃) ₃ solution, drying at 130 ° C / 2 h and calcining at 540 ° C / 2 h. The La content is 1.65% by weight.

Catalyst K

like catalyst J only Ce (NO₃) ₂ solution. The Ce content is 1.65% by weight.

Catalyst L

like catalyst G only Co (NO₃) ₂ solution. The Co content is 1.7% by weight.

Catalyst M

like catalyst G only Co (NO₃) ₂ solution. The Co content is 0.45% by weight.

Catalyst N

like catalyst G, only a solution of Cu (NO₃) ₂ and Co (NO₃) ₂. The Cu content is 1.8% by weight and the Co content is 1.6% by weight.

Catalyst O

like catalyst G, only a solution of Ca (OH) ₂ and Co (NO₃) ₂. The Ca content is 0.1% by weight and the Co content is 1.1% by weight.

Catalyst P

Catalyst P is prepared by impregnating catalyst C with aqueous Co (NO₃) ₂ solution, drying at 130 ° C / 2 h and calcining at 540 ° C / 2 h. The Co content is 3% by weight.

Catalyst Q

like catalyst P only a mixture of Mg (OH) ₂ and Co (NO₃) ₂ solution. The Mg content is 1% by weight and the Co content is 1.5% by weight.

Catalyst R

like catalyst G only Co (NO₃) ₂ solution. The Co content is 3.6% by weight.

Examples 1 to 3

Catalysts B, F and R are tested in a batch test. 5 g of catalyst, 54 g of isobutene and 20 g of water are added to the autoclave and the pressure is adjusted to 50 bar with CO. After heating to 300 ° C, the pressure is adjusted to 500 bar with further carbon monoxide and kept constant during the reaction by successively adding carbon monoxide. After a reaction time of 11 to 15 hours<tables id="tabl0001" num="0001"><img file="EP0249976A1_D0003.tif" /></tables> received in the discharge.

Example 4

Like Examples 1 to 3, but 41 g of cyclohexene are used and the reaction is carried out at 300 bar. After a reaction time of 48 h, 14% by weight of cyclohexane carboxylic acid are found in the discharge.

Examples 5 to 22

Examples 5 to 22 are carried out continuously with isobutene as described above. The reaction conditions and results are summarized in Tables 1 and 2.

Examples 23-24

Long-term experiments on the reaction of isobutene with CO and H₂O over catalyst N and L over 110 h and 82 h at 300 ° C, 300 bar, WHSV = 2.5 h⁻¹ and a molar ratio of 1: 5: 5 and 1: 3: 3 show the runtime behavior described in Tables 3 and 4.<tables id="tabl0002" num="0002"><img file="EP0249976A1_D0004.tif" /></tables><tables id="tabl0003" num="0003"><img file="EP0249976A1_D0005.tif" /></tables><tables id="tabl0004" num="0004"><img file="EP0249976A1_D0006.tif" /></tables>