JPS6115857A - Aldol condensation - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to the production of alpha, beta ethylenically unsaturated monocarboxylic acid compounds, the method comprising:
A saturated aliphatic monocarboxylic acid compound and a formaldehyde compound are mixed under gas phase conditions at a temperature of about 280° C. to 350° C. on a silica support and on a dry solids weight basis.
00 g of at least one cation of a Group 1 or Group II metal at a concentration of approximately 0.010 cation equivalents.

The literature is rich on the reaction of aliphatic monocarboxylic acid compounds with formaldehyde to produce alpha, beta ethylenically unsaturated aliphatic monocarboxylic acids that have one more carbon than the saturated carboxylic acid compound.

Kirk Osmer, Volume 15, 3rd Edition (1,981,) pages 364 and 374 indicate that the propionate-formaldehyde route has been considered for the production of methacrylic acid and methyl methacrylate. . Rikiichi Osmer states that a suitable catalyst must provide high selectivity and conversion and have a lifetime of at least 6 months. Effective catalysts include alkali metal or alkaline earth metal aluminosilicates, pyrogenic silica treated with potassium or cesium hydroxide, alumina, and lanthanum oxide. Although Kirk Othmer shows that their results include a range of conversions and selectivities and that generally the best results are conversions of about 50 and selectivities above 80, these The conversions and selectivities for formaldehyde are considered to be excessively high, unless one mentions a method using a substantial molar excess of propionic acid to formaldehyde, and these conversions and selectivities are based on formaldehyde. It is said that When propionic acid is used in molar equivalents with polardehyde and conversion and selectivity are based on propionic acid, both selectivity and percent conversion are low. Kirk Osmer notes that these data were obtained in short-term experiments and that additional development of catalysts would be required for the concept to be attractive. A careful review of the art does not fail to disclose work examples in equivalent quantities in which reactions lasted for more than one or two days.This is not surprising, since in our experience ``Catalyst life is generally short and tends to cause coke deposits on the catalyst, resulting in reduced catalytic activity. It is not uncommon for coke deposition to reach unacceptable levels within 24 to 48 hours. That's not typical.

Our studies have shown that silica-supported catalysts give relatively high conversions and selectivities on a propionic acid basis when using approximately equimolar concentrations of propionic acid and formaldehyde. Generally, the higher the reaction temperature, the greater the percent conversion of propionic acid and the lower the selectivity of the catalyst. Our studies also showed that silica supports tend to deteriorate over time, in the sense that the catalyst surface area decreases while the average pore size increases. As the surface area decreases from about 10 to 20 m2/g and the number of pores with a diameter smaller than 1200 λ decreases, the catalytic activity falls off rapidly. Moreover, the alkali metal or alkaline earth metal cations tend to volatilize from the catalyst support, resulting in a decrease in catalytic activity (percent conversion and percent selectivity) over long periods of time, as pointed out by Kirk-Othmer. There is a need for a catalyst system that allows operation over a wide range of applications. Although Kirk Osmer states that the catalyst life should be at least 6 months, we are not aware of any prior art example disclosing a condensation reaction between 24 and 48 hours.

Therefore, there remains a need for suitable catalysts and process conditions for converting propionic acid compounds to methacrylic acid compounds that can be utilized over extended periods of time without substantial catalyst degradation.

Our studies showed that one of the byproducts of alkali metal or alkaline earth metal supported silica catalysts is unsaturated cyclic ketones. The formation of this by-product is disadvantageous in the sense that it reduces the yield of the methacrylic acid compound, but it is important in the purification of the methacrylic acid product.
Further downstream, approximately 4 mole percent of The conversion of propionic acid to a cyclic ketone is not uncommon. Of course, this is an unacceptable height.

Therefore, there is a need for methods using silica catalysts that produce lower levels of unsaturated cyclic ketones.

Unless otherwise specified, pore volume 2 surface area and average pore diameter were determined by the BET nitrogen adsorption method (desorption test).

The general object of the present invention is to provide a new method for producing alpha, beta ethylenically unsaturated monocarboxylic acid compounds.

A more specific object of the present invention is to provide a new method for producing methacrylic acid compounds from propionic acid compounds using a silica-supported catalyst. Other objects will become apparent hereinafter.An object of the present invention is to combine a saturated fatty acid monocarboxylic acid compound, preferably a propionic acid compound (acid or methyl ester), and a formaldehyde compound under gas phase conditions.
Silica gel containing at least one cation of a Group 1 or Group II metal and the metal on a dry solids basis. from about 280°C to about 350°C utilizing a catalyst comprising a silica support present at a concentration of at least about 0.01.0 equivalents per 0g
We have now discovered that this can be achieved by aldol-type condensation at temperatures of .degree. Prior art has shown that it is possible to carry out these reactions at temperatures as low as 300°C using various catalysts; are not specifically disclosed.

In the conventional method, (1) the amount of undesired cyclic ketone byproducts is reduced from 4 molar ratio at 390°C to 35°C by lowering the reaction temperature for the reaction of the propionic acid compound;
About 2.5 molar or less at 0°C (332°C
or (2) 24
The loss of cations over 80 days of repeated condensation times followed by 24 hours of decoking was reduced from a level of 75 degrees or higher at 390°C with an attendant reduction in catalyst activity to about 10 degrees at 350°C. There is no indication that activity can be reduced to a constant level. Therefore, reaction temperatures of about 280°C to 350°C are critical.

In summary, the silica support of the present invention can be prepared by gelling an aqueous silica colloid, drying the composition to remove substantially all moisture other than water of hydration, and burning.

The alkali metal and/or alkaline earth metal cations of the catalyst are used in a concentration of 0.010 to 0.20 equivalents, preferably 0.010 to 0.10 equivalents of cation per 100.9 of silica support on a dry solids basis. Be able to do that. At lower cation concentrations, temperatures in excess of 350°C are required to obtain relatively high conversions. 0
．． Is the catalyst life short at cation equivalents of 10 or more?
Become.

Suitable sources of alkali metal and alkaline earth metal cations are sodium hydroxide, potassium hydroxide.

Cesium hydroxide, lithium hydroxide, rubidium hydroxide,
Strontium hydroxide, magnesium hydroxide, lineium phosphate, monosodium phosphate, cesium phosphate, sodium borate, barium hydroxide, sodium carbonate, cesium fluoride,
Contains cesium nitrate, etc. Of course, alkali metal cations are preferred 0 Although any commercially available colloidal silica can be used, it has a surface area of 20 to 275 m2/! g, pore volume from 0.1 to 0.8 CC7 g, average particle size from 40 to 1000^, especially from about 50 to 2 to produce a porous silica-supported catalyst with an average pore size of about 75 to 200^.
Preferably, commercially available colloidal silica with a particle size of 50^ is used (which is incorporated herein by reference). , N, A (C, N, 24,056). As pointed out in S, N, (C0N, 24,056), a silica catalyst consisting of at least one cation of Group 1 or Group I metal and a silica support has a surface area of 20 to 275 m27g, a fine They have a pore volume of 0.1 to 0, sec/g and an average pore diameter of 75 to 200λ, but with a relatively high activity capacity (percent conversion and selectivity) and a relatively long lifetime. Pore volume 9 surface area and average pore size are interdependent variables. Other things being equal and holding one variable constant, increasing surface area increases pore volume, increasing surface area decreases average pore size, and increasing pore volume increases average pore size.

S, N, (C, N, 24,056
) is important.

For example, if the catalyst has a porosity greater than 0.8 CC/g, the catalyst will lack the abrasion strength necessary for long-term use. Porosity is 0. IOC/,! If it is less than 9, the surface area is too low and/or the average pore size is too large. However, as explained above, the catalyst loses activity as pores with a diameter of 1200 Å or less disappear. Therefore, it is desirable to use a catalyst with a substantially smaller average pore size to ensure that the catalyst has an adequate lifetime. The average pore size of the starting material is 200
If it is substantially thicker than Å, there is a substantial reduction in catalyst life. A pore size of at least 75^ is necessary to allow gas diffusion of the reactants and reaction products.

The silica can be treated with cations before drying or after combustion. Catalysts made by adding cations to colloidal silica before or during gelation are disclosed in co-dated application S. Kadak et al., incorporated herein by reference.

N, (C,N, 23.072) can be viewed as a simultaneous formation catalyst. Questions S, N, (C,
N., 23°072), co-formed catalysts are more resistant to water and impregnated, other things being equal, than catalysts made by treating combusted silica with an aqueous cationic solution. The catalyst prepared by the above method is advantageous in that it does not generate a large amount of heat and is therefore easy to decoke. This is apparently due to a more uniform distribution of cations in the carrier.

The silica supports of the present invention are preferably made by forming an aqueous composition of about 10 to 60 parts by weight, on a dry basis, of colloidal silica and an alkali metal and/or alkaline earth metal cation. Colloidal silica is gelled by adjusting the pH to a range of about 3 to 10 degrees, preferably about 6.0 to about 90 degrees. NH, NO
Salts such as No. 3 can be used to promote gelation. Although the silica hydrogel can be aged for two weeks or more, aging does not appear to affect the properties of the catalyst, so aging is not necessary.

The composition is then dried by suitable means, such as in a microwave bath, to constant weight and to apparent dryness, eg, about 4 to 5% moisture on a dry solids basis. Apparently, only the water of hydration is retained by the silica gel after constant weight drying. Silica gel is then added to about 300 s o
'c, preferably about 300 to 600°C. S, N. (C, N.

As pointed out in 24.056), at combustion temperatures above about 800°C, there is a tendency for the surface area to decrease, the pore volume to decrease, and the pore diameter to increase;
The catalyst is outside the required range in S,N, (C,N, 24..056). However, such catalysts can be used in the present invention.

The process of the present invention can be used for the Hairdol type condensation of saturated aliphatic monocarboxylic acid compounds to alpha, beta ethylenically unsaturated monocarboxylic acid compounds having one more carbon atom than the starting saturated aliphatic carboxylic acid compound. Suitable aliphatic monocarboxylic acid compounds that can be converted in aldol-type condensation reactions include acetic acid, propioic acid, methyl acetate, methyl propionate, ethyl propionate, acetonitrile, propionitrile, and the like. Preferred saturated monocarboxylic acid compounds are propionic acid compounds and especially propionic acid, since the catalyst of the present invention is primarily designed for large-scale production of methacrylic acid.

Any suitable source of formaldehyde compounds can be used, including formalin, paraformaldehyde, methanolic formaldehyde, trioxane, etc.
It is preferred to use substantially anhydrous formaldehyde, especially decomposed monomeric gaseous substantially anhydrous formaldehyde.

In summary, alpha, beta ethylenically unsaturated monocarboxylic acid compounds have a molecular weight of about 280 to 350
a saturated aliphatic monocarboxylic acid compound and a formaldehyde compound at a temperature of 0.degree. silica catalyst, preferably in a concentration of 20 to 275 m2/!
g surface area, 0.1 to 0.8 CC/! It can be made by condensation in the presence of a catalyst consisting of a support having a pore volume of J and an average pore diameter of from 75 to 200^. □This reaction may be advantageously carried out in the presence of a water-immiscible hydrocarbon or hydrocarbon diluent containing from 6 to 12 carbon atoms, as herein incorporated by reference. Joint application S filed on the same date in Smith's name
, N, (C,N, 23,094).

As noted in S,N, (C,N, 23,094), the diluent is about 10S (e.g. 30 to 33%
) is advantageous in that it increases the yield. Moreover, as explained below, the diluent has an additional function in the overall process of producing methacrylic acid to propionic acid. Suitable diluents include n-hexane, rheuhebutane, rheuoctane, 2-ethylhexane, n-decane, n-dodecane, O,P, m-xylene, benzene, toluene, sodium, and the like. The concentration of diluent can range from about 10 to 50 parts by weight of reactants in the main reactor.

The molar ratio of monocarboxylic acid compound to formaldehyde is 2
It can range from 5:1 to 1:25. However, best results with this catalyst in methacrylic acid production can be obtained using a molar ratio of propionic acid compound to formaldehyde of about 0.5-2.0 to 1. Generally, the lower the molar ratio, the higher the conversion based on the amount of converted propionic acid.

In some detail, this one-step process for the production of methacrylic acid involves (1) feeding propionic acid and a formaldehyde compound to a reactor containing the silica catalyst of the present invention, and (2) reacting formaldehyde and propionic acid under gas phase conditions. Condensate with water and formaldehyde.

(3) distilling the reaction product to remove water, unreacted formaldehyde and at least some propionic acid from the reaction product; (4) producing a distillate. contacting the water and at least some formaldehyde overhead with a co-distilling agent comprising a water-immiscible diluent to remove the water and at least some formaldehyde overheads.

In a more preferred form of this method, the distillation column is
A sidewall withdrawal tube is placed in the middle of both cases to remove a composition comprising substantially all of the propionic acid and at least some formaldehyde. Joint application S registered in the names of et al.

O8. As pointed out in No. 1, (C,N, 23,004), this sidewall withdrawal tube facilitates the removal of a portion of the formaldehyde from the aqueous mixture rising to the top of the column, thereby reducing formaldehyde concentration at the top of the column. polymerization, thereby eliminating or reducing the possibility of filter blockage at the top of the distillation column. Regardless of whether or not a side wall extraction pipe is used, formaldehyde is extracted from a formaldehyde aqueous solution collected at the top of the tower, which is reacted with an alcohol having 6 to 12 carbon atoms to form hemiacetal, and water is extracted from this hemiacetal. The hope is to distill the substantially anhydrous hemi-secur and then decompose the substantially anhydrous hemi-secur to recover formaldehyde.

Formaldehyde can be extracted advantageously from the alcohol by adding a water-immiscible diluent containing 6 to 12 carbon atoms at the top of the column to facilitate the removal of formaldehyde from the alcohol used to form the hemiacetal. separated into The formaldehyde and diluent are then recycled to the main reactor.

The process of the invention can be carried out at a weight hourly space velocity of about 0.1 to 10, preferably 0.5 to 6.5. Generally, the lower the weight hourly space velocity, the lower the required reaction temperature. The higher the weight hourly space velocity, the higher the required reaction temperature.

The catalyst of the present invention is preferably used after 12 to 72 hours of operation, preferably after 12 to 72 hours of operation. 24,039). To prevent sintering of the silica and/or loss of cations, dilute oxygen (1 to 5 volumes of oxygen and 95 to 99 volumes of inert gas) is added to the catalyst bed and approximately
32 to 343°C), preferably 450 to 550'
F (232 to 288°C) while maintaining the exotherm to below about 10 to 30'F (5.5 to 16.7°C), and the oxygen content to a temperature below about 10 to 30'F (5.5 to 16.7°C). Increase the temperature in small increments with a mixture of 20% oxygen and 80% inert gas until the exotherm disappears while keeping the temperature at 75"F (1,3"F).
9 to 41.78C) and increase the fever by about 10 to 3
Decoking to below 0 (5.5 to 16.7℃) approximately 650℃
to 800'F (343 to 427C) until completion.

In the following examples, all percent conversion, percent yield, and percent selectivity are based on propionic acid (PA) unless otherwise noted.

Example 1 This example has a surface area of 1.19 m27g containing 1.97 weight coefficient of cesium based on the dry weight of silica, and a porosity of 0.604cc//! 9 and a co-formed cesium phosphate silica gel catalyst with an average pore size of 168^ to produce methacrylic acid in a pilot plant. A slurry of 29 parts by weight of paraformaldehyde, 106 parts by weight of propionic acid (PA:FA molar ratio of 3:2) and 47 parts by weight of hebutane was continuously evaporated to 400" parts of paraformaldehyde.
Pyrolysis to monomeric formaldehyde at F (204°C). This composition was then applied to a 1 inch (2,
54cm), inner diameter 0.834 inch (2.12cm),
A 6 ft (180 crn) long Inconel tube with a 0.25 in. (0.63 crn) outside diameter thermowell containing 200 g catalyst and a 1 in.
The reactor was transferred to a reaction system consisting of a 4 foot (120 m) long catalyst zone containing a Denstone backing zone of 54 crn). This thermowell has 6 inches (
Electric heating means were placed along the reactor with thermocouples inserted at 15,3 Crn) intervals. The conversion to methacrylic acid with propionic acid toformaldehyde was carried out at a pilot plant temperature of 660'F (35oC), 10 psig.
(0,7~) and maintained at a weight hourly space velocity of 1.55 for 24 hours. The reaction products were collected and condensed in a heat exchanger. After 24 hours, the feed to the reactor was interrupted and the reactor temperature was lowered to below 550°C (232°C). The heat generation during decoking of the second group of oxygen in nitrogen is approximately 20% lower (
11.1° C.) to the reactor. After the exotherm had ended, the oxygen content was increased to 10 parts, and after limiting the exotherm to below 20 degrees Celsius (11.1 DEG C.), the nitrogen-oxygen mixture was replaced with air. After each exotherm ended, the reactor temperature was increased by 50'F (27.8°C) by precisely controlling the exotherm until the reactor was below 700°C (371°C). This decoking process typically takes 2 to 4 hours and involves continuously passing zero air through the reactor for 70 minutes.
It was flowed for a total of 24 hours at 0"F (371°C). The air was interrupted, the reactor temperature was lowered to 660"F, and the condensation of propionic acid and formaldehyde was initiated. Repeated operations of condensation and decoking were carried out for 80 days, of which 40 days were spent producing methacrylic acid and 40 days were decoking. PA:
The molar ratio of FA changed from 1.51 to 1.34:1. The physical properties of the catalyst before and after 80 days of operation are shown in Table I. The yield after the first day and the average over the first 66 days are shown below in Table 3.

Table ■ Analysis of product averages for initial catalyst, final catalyst, and day 1 product Analysis values Cesium content 1.97% by weight 1.76 Weight-related surface area 11.9 m2/959 m2/9
Pore volume 0.604 CC/fi O,57
0Cc/g Average pore diameter 168＾ 3
02^PA:FA molar ratio 1.5 1
．． Conversion rate based on 34% PA 32. lchi 3
Selection rate based on 2.1-chi PA standard 91.3-chi 8
Section 5, 9 MA/PA yield 29.3% 27.
Section 6 FA standard conversion rate 51.9% 50.
0% FA standard selection rate 84.9 Section 74.
2nd section MA/FA yield 44.1% 37.1%
The catalyst used in this example was 10302.9. ! 9 Narcoag, 1034
- Intense stirring for olO minutes made by vigorously stirring a solution of A colloidal silica (particle size of 34 solids 200^) and a solution of 111.66 g of cesium phosphate (with an average of 5 molecules of water per molecule). A solution of 100 g of ammonium nitrate in 1509 deionized water was then added to the sol and the mixture was stirred for 2 minutes at which point it began to thicken. This silica gel was allowed to solidify after being left at room temperature overnight. The gel was dried to constant weight in a microwave bath, sized from 20 to 40 mesh, and smoked according to the following heating rate: 165° C. for 2 hours. It was then gradually raised to 540°C over 4 hours and then kept at 540°C for a further 8 hours. All steps were carried out in flowing air.

2% by weight of cesium phosphate as hydroxide or carbonate
Substantially the same result can be obtained by replacing the cesium with cesium.

Example ■ The method described in Example 1 was repeated for 24 hours, except that the condensation reaction was (1) below 620 (327'C);
(2) 630 below (332°G), (3) 650”F (3
41'C), (4) below 660 (349°C) and (5)
Conducted at 735'F (390C). the result,
(1) Approximately 1%, (2) Approximately 1.7 inches, (3) Approximately 2.5 inches,
(4) about 2.5%, and (5) about 4% molar conversion of propionic acid to unsaturated cyclic ketones.

Example ■ Example I was repeated over 24 hours, but the cesium content of the cesium phosphate catalyst was increased to 4% by weight and a 1=1 molar ratio of propynoic acid to formaldehyde was used.
Omit the diluent and the pressure is 7.9 psig (0.55Y
! -gage), the weight hourly space velocity was 1.0, and the reaction temperature was 620'F (327°C). 30.
9% of the propionic acid was converted with a selectivity to methacrylic acid of 96.1 moles, a selectivity to the unsaturated cyclic ketone of 1 mole, and a yield of methacrylic acid of 29.7 moles.

Claims (1)

Claims: 1) a saturated aliphatic monocarboxylic acid and a formaldehyde compound under gas phase conditions at a temperature of about 280°C to 350°C on a silica support and at least about 0.010 g per 100 g of silica support on a dry solids basis; 1. A process for the production of alpha, beta ethylenically unsaturated monocarboxylic acid compounds, comprising condensation in the presence of a catalyst comprising at least one cation of a Group I or Group II metal at a concentration of . 2) The method according to claim 1, wherein the saturated aliphatic monocarboxylic acid compound comprises a propionic acid compound. 3) The method according to claim 2, wherein the propionic acid compound comprises propionic acid. 4) The method of claim 1, wherein the cation comprises an alkali metal. 5) The method of claim 4, wherein said alkali metal comprises cesium. 6) The method of claim 4, wherein the molar ratio of propionic acid compound to formaldehyde is in the range of about 0.5-2.0:1.