JP2573597B2 - Solid acid catalyst and method for producing the same - Google Patents

Description

The present invention relates to a solid acid catalyst and a method for producing the same. More specifically, the present invention relates to a solid acid catalyst having excellent solid acidity and a method for producing the same.

[Conventional technology]

Many of the current chemical industry processes use mineral acids such as sulfuric acid and phosphoric acid, and acidic substances such as aluminum chloride and boron trifluoride as catalysts. There are many problems such as use, wastewater treatment, corrosion of equipment, formation of undesirable by-products, coloring of products. For this reason, development of a solid acid catalyst to replace mineral acid, aluminum chloride, and the like is desired.

[Problems to be solved by the invention]

Against this background, solid oxides such as metal oxides and composite oxides such as alumina, silica-alumina or metal sulfates and phosphates have been studied, and their application to chemical industrial processes has been studied. ing. Further, as a solid acid catalyst which can be used in the presence of water, ion exchange resins, hydrated niobium oxide, and the like have been proposed. Among them, ion exchange resin catalysts have drawbacks such as low acid strength, easy disintegration of the resin, and limited application range, particularly temperature. Further, a hydrous niobium oxide catalyst is disclosed in JP-A-60-44.
039 proposes its properties as a solid acid catalyst, but there is a limit to the application temperature range of 400 ° C. or less, preferably 300 ° C. or less, and further improvement in catalytic activity is desired.

[Means for solving the problem]

The present inventors have conducted intensive studies in order to solve the above-mentioned disadvantages of the conventional catalyst, and as a result, prepared tantalum hydroxide by various methods, washed with acid and / or water, and then heat-treated. Tantalum oxide containing water of hydration (hereinafter also referred to as “hydrated tantalum”) exhibits extremely strong solid acidity,
The present invention was found to be effective for various acid-catalyzed reactions, and reached the present invention.

That is, the gist of the present invention is (1) a hydration reaction of an olefin, which is composed of tantalum oxide containing water of hydration, an isomerization reaction of an olefin, an esterification reaction of a carboxylic acid and an alcohol, a Beckmann rearrangement reaction or A solid acid catalyst for the aldol condensation reaction, and (2) an olefin hydration reaction, which comprises subjecting tantalum hydroxide to washing with an acid and / or water and then heat-treating it at a temperature of about 600 ° C. or lower.
Olefin isomerization reaction, carboxylic acid-alcohol esterification reaction, Beckmann rearrangement reaction or aldol condensation reaction.

 Hereinafter, the present invention will be described in detail.

Although the details of the structure of the hydrous tantalum oxide of the present invention are unknown, it is amorphous or has a low degree of crystallization, and is expressed by an empirical formula as Ta ₂ O ₅ .nH ₂ O, where 0
<N ≦ 8, preferably 0 <n ≦ 3.

The method for preparing tantalum hydroxide used for producing the hydrous tantalum hydroxide of the present invention includes the following method. The first method is a pentavalent tantalum halide such as TaCl ₅ , TaBr ₅ , TaI ₅ , TaF ₅ or oxychloride TaOCl ₅
Is a method of hydrolyzing. Specifically, after dissolving TaCl ₅ in concentrated hydrochloric acid, hot water, aqueous ammonia or a solution exhibiting basicity, for example, an aqueous solution such as potassium hydroxide or sodium hydroxide is added to form a precipitate of tantalum hydroxide. Method. The second method is an alkoxide of pentavalent tantalum, for example, Ta (OCH ₃ ) ₅ , Ta (OC ₂ H ₅ ) ₅ , Ta
(OC ₃ H ₇ ) ₅ or an alkoxide containing halogen such as TaCl (OCH ₃ ) ₄ , TaCl ₂ (OCH ₃ ) ₃ TaCl (OC
₂ H _{5) 4} is a method for hydrolyzing such. Specifically, Ta
(OC ₂ H ₅ ) ₅ is dissolved in ethanol, and water, ammonia water or a basic solution, for example, an aqueous solution of potassium hydroxide, sodium hydroxide or the like is added to form a precipitate of tantalum hydroxide. A third method is to hydrolyze a trivalent tantalum halide, for example, TaBr ₃ to produce tantalum hydroxide. A fourth method is to convert tantalum oxide (which does not contain water of hydration) Ta ₂ O ₅ to an alkali metal hydroxide or carbonate, sulfate, pyrosulfate such as KOH, K ₂ CO ₃ , NaOH, In this method, tantalum hydroxide is obtained by hydrolyzing a material obtained by melting with Na ₂ CO ₃ , K ₂ SO ₄ , K ₂ S ₂ O ₇ , and the like.

The tantalum hydroxide obtained as described above does not have sufficient solid acidity as it is, and first requires an operation of washing with acid and / or water. This washing operation is probably effective in removing basic substances such as alkali metals and ammonia used in the preparation of tantalum hydroxide. Washing with an acid and / or water is, specifically,
The obtained tantalum hydroxide is diluted with a dilute acid, preferably 0.1 to 3
It is effective to disperse the mixture in an aqueous solution of a mineral acid such as N, hydrochloric acid, nitric acid, sulfuric acid, or the like, and stir the solution. More preferably, the solution is heated and dispersed and washed under a boiling condition. in this case,
If the aqueous solution of the acid is too thick, a part of the tantalum hydroxide is dissolved and removed, which is not preferable. The washing is repeated several times, and it is effective to separate the tantalum hydroxide and the washing solution each time by excessive or centrifugation. After washing with a dilute acid, it is dispersed in water and washed. This is preferable because the mixing of chlorine is suppressed.

After washing, tantalum hydroxide is separated by filtration or centrifugation, dried, and heat-treated to obtain the solid acid catalyst intended for the present invention. In these operations, the temperature of the heat treatment is important for the solid acidity proposed in the present invention, and in the present invention, it is about 600 ° C. or less, preferably 100 to 50 ° C.
The heat treatment is performed at a temperature of 0 ° C, more preferably 200 to 400 ° C.

Table 1 shows the results of measuring the surface acid strength of hydrous tantalum oxide obtained by heat treatment at various temperatures using a Hammett indicator.

As is clear from Table 1, hydrous tantalum shows an acid strength higher than H ₀ = −8.2 (corresponding to the acid strength of 90% sulfuric acid) in the processing temperature range of 200 ° C. to 400 ° C. The acid strength is higher than H ₀ = −5.6 (corresponding to the acid strength of 71% sulfuric acid), and at 600 ° C. or lower, the acid strength is higher than H ₀ = −3.0 (corresponding to the acid strength of 48% sulfuric acid).

Almost no such metal oxide shows such a strong acid strength in ordinary metal oxides.
It is noted that it shows strong acid strength over a wide temperature range below 0 ° C, especially 200 ° C to 400 ° C. The above-mentioned hydrous niobium oxide has been proposed as a solid acid catalyst exhibiting a strong acid strength at a temperature of 300 ° C. or less.However, at higher temperatures, the acid strength sharply decreases, and therefore, for reactions requiring such high temperatures, I can not use it. The details of the cause of the decrease in acid strength are still unknown, but it is considered that one of the causes may be that crystallization of niobium oxide proceeds. on the other hand,
Since the crystallization temperature of tantalum oxide is higher than that of niobium oxide, it is presumed that the tantalum oxide shows a strong acid strength up to a higher temperature. The temperature at which this crystallization occurs is measured by differential thermal analysis (hereinafter referred to as DTA). The results measured by the present inventors for hydrous tantalum and hydrous niobium are shown in FIGS. 1 and 2, respectively.

Comparing these figures, the hydrous niobium oxide crystallizes to niobium oxide at 587 ° C, whereas the crystallization of hydrous tantalum oxide to tantalum oxide occurs at 730 ° C and is therefore stronger at higher temperatures. It is presumed to show solid acidity.

The hydrous tantalum oxide of the present invention may be used alone or in combination with other components, for example, silica,
Alumina, titanium oxide, zirconium oxide, niobium oxide, or a composite thereof may be used. Furthermore, after pretreatment of hydrous tantalum or a composite of hydrous tantalum and the above-mentioned components with sulfuric acid, phosphoric acid, hydrofluoric acid, or the like, the catalyst performance may be enhanced by heat treatment at a low temperature in some cases. .

The hydrous tantalum catalyst of the present invention can be used as a catalyst in a commonly known acid catalyzed reaction. Further, it can be used for both liquid phase and gas phase reactions. A specific example of such a reaction is the hydration reaction of an olefin. More specifically, carbon number 2
Of the corresponding alcohols by hydration of the olefins from 9

Dehydration reaction of alcohol. More specifically, carbon number 2
Formation of the corresponding olefins by dehydration of the alcohols from 1 to 9.

Olefin isomerization reaction. More specifically, an isomerization reaction of an olefin having 4 to 8 carbon atoms.

Esterification reaction between carboxylic acid and alcohol. More specifically, an esterification reaction of a saturated or unsaturated carboxylic acid having 2 to 5 carbon atoms with a saturated or unsaturated alcohol having 1 to 4 carbon atoms.

 An ester hydrolysis reaction which is the reverse reaction of the above.

Claisen condensation reaction. More specifically, the production of acrylic acid or methacrylic acid by the reaction of acetic acid or propionic acid with formaldehyde.

And the like. In addition, it can be used for an alkylation reaction of an aromatic compound, a polymerization reaction of an unsaturated hydrocarbon, a Beckmann rearrangement reaction, an aldol condensation reaction, and the like.

Although the optimum shape of the catalyst depends on the reaction mode, when a molded catalyst is desired, a usual molding method can be employed.

〔Example〕

Next, the present invention will be described more specifically with reference to examples. However, the scope of the present invention is not limited by the following examples unless it exceeds the gist of the present invention.

Example 1 25 g of tantalum pentachloride (Mitsuwa Kagaku) was added to ethanol 2
Dissolved in 50 ml. In addition, ethanol from which water was removed by a molecular sieve in advance was used. 23.1 g of potassium hydroxide (content 85%) was added to this solution with ethanol 250
The solution obtained by dissolving the solution in ml was added dropwise little by little to produce a white precipitate. The white precipitate was allowed to stand in this ethanol for one day to ripen. Subsequently, a white precipitate and a supernatant were separated by a centrifuge. This precipitate was dispersed in 1N hydrochloric acid aqueous solution 1, and the solution was heated to boiling and held for 1 hour. After cooling to room temperature, the precipitate and the liquid were separated by a centrifuge. Again, boiling dispersion washing in a 1N hydrochloric acid aqueous solution was performed again for 1 hour. Subsequently, boiling dispersion washing in deionized water 1 was repeated three times (each time was one hour). After each washing, centrifugation was performed to separate the precipitate from the liquid. When an aqueous solution of silver nitrate was added dropwise to the solution after the final washing, the solution did not become cloudy and the presence of chloride ions was not recognized.

Next, the precipitate was dried in a vacuum dryer at 120 ° C. for 6 hours. The weight of the white powder after drying was 16.6 g. This white powder is dried at various temperatures (200 ° C, 300
° C, 400 ° C, 500 ° C, 600 ° C and 800 ° C).
After the heat treatment, the acid strength was measured using a Hammett indicator, and the results shown in Table 1 were obtained.

Example 2 After dissolving 5 g of tantalum pentachloride (manufactured by Mitsuwa Chemical Co., Ltd.) in 50 ml of concentrated hydrochloric acid, the solution became cloudy when added dropwise in 500 ml of demineralized water. When this liquid was heated and boiled, the degree of cloudiness of the liquid increased, and the generation of white insolubles increased. It was kept for 2 hours under boiling conditions with occasional addition of water. After cooling, the mixture was aged at room temperature for 1 day. After the white precipitate was separated from the liquid by centrifugation, washing of the precipitate was repeated in the same manner as in Example 1 and subsequently dried. The obtained white powder was heat-treated at various temperatures under flowing dry air. Hammett
The results of the acid strength measurement using the indicator were almost the same as those in Table 1 above.

Comparative Example 1 Hydrous Niobium (AD-38 manufactured by CBMM International)
2) The two kinds of temperature (300 ℃ and 600 ℃) under the flow of dry air
Was heated. Table 2 shows the results of acid strength measurement using the Hammett indicator. This result is in good agreement with that shown in JP-A-60-44039.

Comparative Example 2 Commercially available silica-alumina molded product (N631H manufactured by JGC Chemicals;
The powder obtained by crushing SiO ₂ / Al ₂ O _{3 (} weight ratio: about 70/30) was heat-treated at 400 ° C., which is known to increase solid acidity, in flowing dry air. Table 2 shows the acid strength.

Comparative Example 3 A mixture of SiCl ₄ and TiCl ₄ was thermally decomposed to obtain a silica-titania catalyst (Si / Ti atomic ratio = 95/5). This was heat-treated at 300 ° C. under flowing dry air. The acid strength is shown in Table 2.

Reaction Example 1 The gas phase esterification reaction between methacrylic acid and methanol was taken as a model reaction using a solid acid catalyst, and the performance of the catalyst was evaluated. In this reaction, generated methyl methacrylate (hereinafter, referred to as MMA) is useful as a raw material for a synthetic resin paint and the like, and is one of industrially important reactions. The raw material and the product are easily polymerized. In view of this, it is preferable that the above-mentioned esterification reaction is completed under as mild a condition as possible and in a short time. Therefore, it is desired to develop a highly active catalyst. ing.

1 ml of hydrous tantalum oxide prepared as described in Example 1 and heat-treated at 300 ° C. was placed in a Pyrex glass reactor as a catalyst, and methacrylic acid / methanol = 1/4 (mole) at a reaction temperature of 200 ° C. Ratio) The mixture was introduced with a micro feeder, and reacted at a space velocity of about 2,500 hr ^{-1 using} nitrogen as a carrier gas. The supply amounts of the reactants were 4.15 mmol / hr of methacrylic acid, 16.59 mmol / hr of methanol, and 91.76 mmol / hr of nitrogen. The reaction product was collected in a cooled methyl cellosolve-water (1: 1) solution and analyzed by acid titration and gas chromatography. The result of the reaction was 0.5 hours after the start of the reaction. The amount of MMA produced was 4.05 mmol / hr after the start of the reaction. The amount of MMA produced after 2 hours was 3.99 mmol / hr. The amount of MMA produced after 5 hours from the start of the reaction was 3.74 mmol / hr. The single stream yield for methacrylic acid was 97.7
% (0.5 hr), 96.2% (2 hr), 90.1% (5 hr), and the selectivity was almost 100%. In addition, no dimethyl ether was produced by dehydration of methanol, and more than 99% of methanol was recovered in total with MMA.

When the activity of the catalyst prepared as described above was tested under the same reaction conditions, the results shown in Table 3 were obtained.

From the above results, it is clear that the hydrous tantalum-containing solid acid catalyst of the present invention maintains a high MMA yield and has excellent performance.

Table 3 Evaluation of catalytic performance (gas phase esterification reaction between methacrylic acid and methanol) Reaction temperature: 200 ° C, SV: 2,500 hr ^-1 Catalyst amount: 1 ml Supply amount: methacrylic acid / methanol / nitrogen = 4.15 / 16.59
/91.76 (mmol / hr) Reaction Example 2 In order to clarify the difference in activity between catalysts, Reaction Example 1
The gas phase esterification reaction described in the above was carried out at an increased space velocity. That is, under the same reaction temperature and raw material supply amount as in Reaction Example 1, the space velocity was reduced to about 1/5 of 0.2 ml,
12,500hr ^-1 . The hydrous tantalum oxide prepared as described in Example 1 as a catalyst was treated at various temperatures (200
C., 300.degree. C., 400.degree. C., 500.degree. C., 600.degree. C. and 800.degree.
Heat treated at 0 ° C. and 600 ° C. was used. The reaction results are shown in Table 4. Note that no dimethyl ether was detected in the reaction product, and more than 99% of methanol was recovered in total with MMA.

From the results shown in Table 4, it is clear that hydrous tantalum has a high catalytic activity and that it can be used over a wide temperature range because it has a high catalytic activity even when treated at a higher temperature than hydrous niobium.

Example 3 Precipitate prepared as described in Example 1 (120 ° C.
5 g) was immersed for 1 day in 50 ml of a 1N H ₂ SO ₄ aqueous solution. Next, the solid from which the liquid was separated was dried at 120 ° C. in a vacuum dryer.
Dried for 6 hours. The acid strength of the dried white powder and the powder obtained by heat-treating it at 300 ° C. under flowing dry air at 300 ° C. were as shown in Table 5 using a Hammett indicator.

Reaction Example 3 A reaction for converting cyclohexanone oxime to ε-caprolactam is called a Beckmann rearrangement reaction. The performance of the solid acid catalyst of the present invention for this reaction was evaluated.

Hydrous tantalum hydroxide prepared as described in Example 1 and heat treated at 300 ° C. and sulfuric acid treated hydrous tantalum prepared as described in Example 3 and heat treated at 300 ° C. (H ₂ SO ₄ / 0.35 ml of each catalyst (referred to as hydrous tantalum oxide) was placed in a Pyrex glass reactor as a catalyst, and the reaction temperature was 250
At 0 ° C., a benzene solution of cyclohexanone oxime was introduced by a microfeeder, and reacted at a space velocity of 5800 hr ^{−1 using} nitrogen as a carrier gas. The supply amounts and compositions of the reactants were as follows.

Cyclohexanone oxime: benzene: nitrogen = 0.913: 11.86: 78.52 (mmol / hr) = 1:13:86 (mol%) The reaction product was collected in cooled tetraethylene glycol dimethyl ether and quantitatively analyzed by gas chromatography. . Table 6 shows the reaction results.

Reaction Example 4 The aldol condensation reaction of acetone is a reaction using an acid or a base as a catalyst. The performance of the solid acid catalyst of the present invention for this reaction was evaluated.

Acetone 2 in an autoclave with a stirrer of 100 ml
0 ml, prepared as described in Example 1, 1 g of hydrous tantalum hydroxide heated at 300 ° C. was added as a catalyst, and the mixture was purged with nitrogen gas and reacted at 150 ° C. for 1 hour. After the completion of the reaction, the reaction product was analyzed by gas chromatography, and the following results were obtained.

Acetone conversion 15.9% Mesityl oxide selectivity 84.3% Isomesityl oxide selectivity 6.3% Diacetone alcohol selectivity 2.0% Reaction Example 5 The gas phase isomerization reaction of 1-butene is taken as a model reaction of a solid acid catalyst, The performance of was evaluated.

1 ml of hydrous tantalum oxide prepared as described in Example 1 and heat-treated at 300 ° C. was placed in a Pyrex glass reactor as a catalyst at a reaction temperature of 100 ° C., and 1-butene / nitrogen = 40/60 ( (Molar ratio) mixture, space velocity 1
The reaction was performed at 0,000 hr- ¹ (Reaction Example No. 5-2). When the reaction product was directly subjected to quantitative analysis by gas chromatography connected to the reactor outlet, the composition of butenes was as follows: 1-butene: t-2-butene: C-2-butene = 93.8: 2.8: 3.4 (%) Met. This corresponds to a cis / trans ratio of 1.21 of 1-butene conversion of 6.2% of 2-butene formed. Compounds other than those having 4 carbon atoms were not detected.

In addition, the performance of the catalysts prepared as described above under the same reaction conditions as shown in Table 7 was evaluated (Reaction Examples No. 5-1, 5-3, 5-4 and 5-5). ) And the results shown in Table 7 were obtained.

Reaction Example 6 Synthesis of t-butyl alcohol by a liquid phase hydration reaction of isobutene was taken as a model reaction, and the performance of the catalyst was evaluated.

19.4 g of water in an autoclave with a stirrer having an internal volume of 200 ml,
57.8 g of butyl cellosolve (solvent) and hydrous tantalum hydroxide prepared as described in Example 1 and heat-treated at 200 ° C
After adding 2.5 g and replacing with nitrogen gas, isobutene 51.7
mmol was introduced. The reaction was carried out at 150 ° C. for 16 hours, and the product was analyzed by gas chromatography.
The amount of -butyl alcohol produced was 11.8 mmol. This corresponds to 22.8 mol% of the starting isobutene.

〔The invention's effect〕

The hydrous tantalum catalyst of the present invention exhibits strong acid strength over a wide temperature range and can be suitably used for various acid catalyzed reactions.

[Brief description of the drawings]

FIG. 1 is a differential thermal analysis curve of hydrous tantalum oxide, and FIG. 2 is a differential thermal analysis curve of hydrous niobium oxide.

Continuation of the front page (51) Int.Cl. ⁶ Identification number Reference number in the agency FI Technical indication location C07C 45/72 C07C 45/72 49/17 9049-4H 49/17 E 67/08 9546-4H 67/08 69 / 54 9546-4H 69/54 Z C07D 201/04 C07D 201/04

Claims (2)

(57) [Claims] An olefin hydration reaction, an olefin isomerization reaction, an esterification reaction between a carboxylic acid and an alcohol, a Beckmann rearrangement reaction or an aldol condensation reaction characterized by comprising tantalum oxide containing water of hydration. Solid acid catalyst. 2. An olefin hydration reaction, an olefin isomerization reaction, characterized in that tantalum hydroxide is washed with an acid and / or water and then heated at a temperature of about 600 ° C. or less.
A method for producing a solid acid catalyst for an esterification reaction, a Beckmann rearrangement reaction or an aldol condensation reaction between a carboxylic acid and an alcohol.