JPS6115858A - Regeneration of methacrylic acid catalyst - 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 Field of the Invention The field of the invention relates to a method for producing an alpha-mono-terethylenically unsaturated carboxylic acid compound, which method comprises: (1) a rostral aliphatic monocarboxylic acid compound and formaldehyde; (2) Condensate the above saturated monocarboxylic acid compound with formaldehyde under gas phase conditions to form an alpha (-terethylenically unsaturated compound) which has one more carbon atom than the above saturated carboxylic acid compound. A saturated monocarboxylic acid compound is produced in the presence of a solid catalyst, and (3) coke is deposited on the solid □ catalyst in the above reactor, and then an aliphatic monocarboxylic acid compound and polyaldehyde 9 are produced.
The feed of compound to the reactor is stopped and diluted oxygen is applied over the catalyst at a temperature not exceeding 650°F (343°C), preferably 550°F (288°C), with an exotherm of about 10 to 30°C. The exotherm is raised to about 10 to 30 °F (5.6 to 167 °C) with restraint until the exotherm disappears with a mixture of about 20% oxygen and 80% inert gas, such as air. , 6 to 16.7 °C) and then from 25 to 75 °C.
Incrementally increase the temperature in increments of 10 to 3''°F (13,9 to 41,7°C) to increase the exotherm until decoking is complete at about 650 to 800°F (34,3 to 427°C).
0°F (5.6 to 16.7°C).

More particularly, the field of the invention is the production of methacrylic acid in one or more reactors from propionic acid and formaldehyde in a gas phase aldo-9-type condensation reaction in the presence of a solid catalyst. The process relates to a process in which, after the coke has been deposited on the solid catalyst in the first reactor, the feed of propionic acid-formaldehyde 9 is diverted to the second reactor or completely stopped and the diluted oxygen is transferred to the coke. Decoking the catalyst by passing it over the deposited solid catalyst at a temperature below 5506 F'' (288 C). The solid catalyst preferably consists of at least one cation of a Group 1 or Group II metal and a silica support; The carrier preferably has a surface area of 20 to 275 m2/j;
1 to 0.8 CC/, pore volume of 9, and 75A
It has an average pore size of 20OA.

BACKGROUND OF THE INVENTION Unsaturated acids such as methacrylic acid and acrylic acid, acrylonitrile, and esters of such acids such as methyl methacrylate are widely used in the preparation of corresponding polymers, resins, and the like. Various methods and catalysts have been proposed for converting alkanoic acids, such as acetic acid or propionic acid, and formaldehyde by a Heraldol-type reaction with monocarboxylic acids such as methacrylic acid.

-S-wise, the reaction between acid and formaldehyde takes place in the vapor or gas phase in the presence of a basic or acidic catalyst.

There is a wealth of literature disclosing the reaction of an aliphatic carboxylic acid compound with formaldehyde to form an alpha beta ethylenically unsaturated aliphatic monocarboxylic acid compound having one more carbon than the saturated carboxylic acid compound.

Kirk Osmer Volume 5, 3rd Edition (1981), 36
On pages 4 and 374 it is stated that the propionate-formaldehyde route is being considered in the production of methacrylic acid or methyl methacrylate. Kirk Osmer states that a suitable catalyst should provide high selectivity and conversion and have a lifetime of at least 6 months.

Effective catalysts include alkali metal or alkaline earth metal aluminosilicates, silica treated with potassium or cesium hydroxide, alumina, and lanthanum oxide. Although Kirk-Othmer shows that their results span a range of conversions and selectivities and that generally the best results are >80% selectivity at about 50% conversion, these The conversions and selectivities of p would be too high unless Kirk-Osmer mentions a method using a substantial molar excess of propionic acid over formaldehyde, and those conversions and selectivities are based on formaldehyde. Both selectivity and percent conversion are low when propionic acid is used in molar equivalents with formaldehyde and conversion and selectivity are based on propionic acid. A careful review of the prior art does not provide equivalent examples of operations in which the reaction lasted for more than one day or more than two days. This is not surprising, since our experience has shown that catalyst lifetimes are generally short and coke deposits on the catalyst, resulting in a rapid drop in catalyst activity.

Our studies on coke-deposited catalyst surfaces show that coke deposition reduces the activity capacity of certain areas of the catalyst surface, and that the continued catalytic activity capacity depends not only on the amount of coke deposited on the catalyst surface but also on the catalyst composition. has been done. 2g or 3g of coked silica catalyst bed can be heated to 1000°F with air.
Although it can be regenerated at (538 °C), even larger coked silica catalyst beds will cause sintering under these regeneration conditions. , silica-supported catalysts were shown to provide relatively high conversions and selectivities based on propionic acid. Generally, the higher the reaction temperature, the
The percent conversion of propionic acid is high and the selectivity of the catalyst is low. Our studies also showed that silica supports tend to degrade over time in the sense that the catalyst surface area decreases while the average pore size increases. The surface area drops to about 10 to 20 m2/g to 1200 Å
Catalytic activity falls rapidly as the number of pores with diameters below decreases. This deterioration is also a function of the water content of the reaction medium. The more water present, the faster the silica gel carrier deteriorates. Although substantially anhydrous reactants can be used, there is one molecule of product water per molecule of product. On top of that,
There is a tendency for alkali metal or alkaline earth metal cations to volatilize from the catalyst support, resulting in a decrease in catalytic activity (
% conversion and/or % selectivity) falls rapidly.

As Kirk Othmer points out, there is a need for catalyst systems that can operate for longer periods of time. Although Kirk Osmer states that the catalyst life should be at least 6 months, we are unaware of any prior art process that discloses condensation reactions lasting longer than 24 to 48 hours. Accordingly, there is a need for suitable catalysts and/or processes for converting propionic acid compounds to methacrylic acid compounds that can be used for extended periods of time without substantial catalyst deterioration.

A general object of the present invention is to provide a new catalyst regeneration process suitable for use in the catalytic condensation of saturated aliphatic monocarboxylic acid compounds and formaldehyde compounds to alpha-terethylenically unsaturated monocarboxylic acid compounds. It is to be. Other purposes will become clear later.

The object of the present invention can be achieved by a method for producing a monoterethylenically unsaturated carboxylic acid compound, which method includes (1) supplying a saturated aliphatic monocarboxylic acid compound and formaldehyde to a reactor; ,(2)
The saturated monocarboxylic acid compound and formaldehyde are condensed under gas phase conditions to produce a flufurabator ethylenically unsaturated monocarboxylic acid compound having one more carbon atom than the saturated carboxylic acid compound in the presence of a peripheral catalyst. ,
(3) After the coke is deposited on the solid catalyst in the reactor, stop feeding the aliphatic monocarboxylic acid compound and formaldehyde compound to the reactor, and add diluted oxygen onto the catalyst at 650 °C. Exotherm at temperatures not exceeding 343 °F (343 °C), preferably not exceeding 550 °F (288 °C).
6.7℃), about 20% oxygen and 80%
The oxygen content is increased incrementally with reduced exotherm from about 10 to 30°F (5.5 to 16.7°C) until the exotherm disappears with a mixture of an inert gas, such as air, and then 25°C.
Incrementally increase the temperature by 75°F (13.9 to 41.7°C) and decoking from about 650 to 800'F (
343 to 427°C) until completion at approximately 1
Control from 0 to 30°F (5.5 to 16.7°C),
It consists of decoking by

By suppressing the exotherm during regeneration, it is possible to prevent catalyst loss and/or sintering of the catalyst bed and reduce changes in the pore structure and surface area of the silica catalyst. Therefore, the catalyst can be used repeatedly even after multiple regenerations.

On a commercial basis, the process involves diverting the flow of alpha ether-ethylenically unsaturated monocarboxylic acid compound and formaldehyde from a first reactor to a second reactor while the first reactor undergoes regeneration. This can be advantageously implemented by If regeneration is carried out for half the time that aldol-type condensation is being carried out, three reactors and two downstream processing sections are employed, one reactor undergoing regeneration and two It is possible to produce terethylenically unsaturated monocarboxylic acid compounds using the following reactions.

In summary, the silica supports of the present invention can be made by gelling an aqueous silica colloid, drying the composition to remove substantially all water other than water of hydration, and firing.

The alkali metal and/or alkaline earth metal cation of the catalyst is 0 per 100 g of silica support on a dry solids basis.
Cation concentrations from 0.001 to 0.2 equivalents (Dulham atoms) can be used. Generally, silica support 10% on a dry solids basis
0. ! It is preferred to have about 0.004 to 0.1 equivalents of cation per 9, since the higher the cation concentration, the lower the temperature required for the condensation of the saturated aliphatic monocarboxylic acid compound and the formaldehyde compound. The selectivity and life of the catalyst are large. Photo with low cation concentration,
The condensation temperature required to obtain the desired conversion to alpha beta ethylenically unsaturated monocarboxylic acid compounds is high, and the catalyst has low selectivity and short life.

Suitable sources of alkali metals and alkaline earth metals are hydroxides, potassium hydroxide, cesium hydroxide,
Includes lithium hydroxide, ruhicium hydroxide, strontium hydroxide, magnesium hydroxide, lithium phosphate, trisodium phosphate, cesium phosphate, sodium borate, barium hydroxide, sodium carbonate, cesium fluoride, cesium nitrate, and the like.

Among these, alkali metal cations are preferred.

Any commercially available colloidal silica can be used, particularly those with an average particle size of 40 to 100 OA, a surface area of 20 to 275 m2/g, a pore volume of 0.1 to 0.8 CC/11, and an average fineness of 40 to 100 OA. Commercially available colloidal silica having a particle size of about 50 to 250 Å is preferably used to create a silica-supported catalyst having a pore size of about 75 to 20 OA, as described in the co-pending application S, N (C
, N, 24,056) (filed in the name of Hagen et al., same date), which is incorporated herein by reference. S,N.

As pointed out in (C, S, 24,506), the weekly rate table of elements (Handbook of Che
mistry and physics, 46th edition,
Chemjcal Rubber Co.

A silica catalyst comprising at least one cation of a Group 1 or Group II metal and a silica support, the back cover of ``Creepland, Ohio'';
with a surface area of 0.01 to 0.8 CC/g, a pore volume of 0.1 to 0.8 CC/g, and an average pore diameter of 75 to 2 ooi'), but with a relatively high activity capacity (conversion and selectivity) and a relatively long lifetime. There is. Pore volume, surface area and average pore size are interdependent variables. Holding one variable constant, as surface area increases, pore volume increases, as surface area increases, average pore size decreases, and as pore volume increases, average pore size increases. S, N, (C
,N.

24.056), it is important that the catalyst satisfies each of the pore volume, surface area and average pore diameter.

For example, if the catalyst has a porosity greater than 0.8 CC/9, the catalyst lacks the abrasion strength necessary for long-term use. Porosity is 0. ICC/,! If it is less than 9, the surface area is too small and/or the average pore size is too large. However, as explained above, the catalyst is 1
It loses activity as pores with diameters smaller than 200 pores disappear. Therefore, it is desirable to fabricate a catalyst with a substantially smaller average pore size so that the catalyst has an adequate lifetime. A substantial reduction in catalyst life occurs if the average pore size of the starting catalyst is substantially greater than 20 OA.

A pore size of at least 75 A is required to allow gas diffusion of the reactants and reaction products.

The silica can be treated with cations either before drying or before firing. Catalysts made by adding cations to colloidal silica before or during gelation can be viewed as co-formed catalysts, and these are published in applications filed on the same date named Kadassoku et al.
(C,N,23,072) (7) subject matter, this application is incorporated herein by reference. Application S,N, (C,N.

23.072), meaning that co-formed catalysts are substantially more water resistant and easier to decoke than catalysts made by treating calcined silicas with cationic aqueous solutions. is advantageous because, other things being equal,
This is because catalysts made by impregnation do not generate heat. This is apparently due to a more uniform distribution of the cations in the carrier.

The silica supports of the present invention are preferably made by forming an aqueous composition of about 20 to 60% by weight, on a dry basis, of colloidal silica and alkali metal and/or alkaline earth metal cations. Silica has a pH in the range of about 3 to 10, preferably about 6.0.
to about 9.0 with alkali metal or alkaline earth metal cations.

Salts such as NH4NO3 can be used to promote gelation.

Silica hydrogels can be aged for two weeks or more, but aging appears to have a significant effect on the properties of the catalyst.
Therefore, aging is not necessary. The composition is then dried by any 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. After drying to a constant weight, it is clear that only water of hydration is retained by the silica gel. The silica gel is then heated to about 300°C to 800°C, preferably about 300°C to 6°C.
Partially fired at 00℃. S, N, (C, N
, 24, 0.56), about 80
At baking temperatures of 0°C, the surface area tends to decrease, the pore volume decreases, and the pore diameter increases, so that the catalyst becomes S,N, (C,N.24,056
) outside the required range. However, such catalysts can be used in the present invention.

The process of the invention is used for the aldol-type condensation of a saturated aliphatic monocarboxylic acid compound to an alpha beta ethylenically unsaturated monocarboxylic acid compound having one more carbon atom than the starting saturated aliphatic carboxylic acid compound. can.

Suitable aliphatic monocarboxylic acid compounds that may be converted in aldol-type condensation reactions include acetic acid, propionic acid, methyl acetate, methyl propionate, ether propionate, acetonitrile, propionitrile, and the like. Preferred saturated monocarboxylic acid compounds are propionic acid compounds, 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 compound, e.g. tJf
, formalin, paraformaldehyde, methanolic formaldehyde, trioxane, etc., but it is preferred to use substantially anhydrous formaldehyde, particularly decomposed monomeric gaseous substantially anhydrous formaldehyde.

In summary, alpha beta ethylene (ILE unsaturated monocarboxylic acid compound) is produced by combining a saturated aliphatic monocarboxylic acid compound and a formaldehyde compound under gas phase conditions.
Approximately 0.001 per 100 g of silica support on a dry solids basis
a silica catalyst, preferably with at least one cation of a Group N metal, at a concentration of 0.2 equivalents from 20
From 275 m27fl surface area 0.1 to 0.8 CC
/9 pore volume and a catalyst consisting of a support having an average pore size of 75 to 200×(7).

This reaction can be carried out in the presence of water-immiscible hydrocarbons or hydrocarbons containing from 6 to 12 carbon atoms with an azeotropic point of about 95°C or less; Smith's name S, N, filed on the same date.
(C,N, 23,094), which is incorporated herein by reference.

Since the product stream contains significant amounts of unreacted propionate, unreacted formaldehyde, and water, selection of an appropriate solvent in the preferred method of distilling the reactor effluent to separate the components is difficult. , determined by the boiling point of the azeotrope of propionic acid and methacrylic acid. Both pro-1-ionic acid and methacrylic acid form a water azeotrope with a boiling point of 99°C.

Distillative separation of C6-C12 hydrocarbons in the presence of water requires that the water:hydrocarbon azeotrope formed have a boiling point below the boiling point of the water azeotrope with propionic acid and methacrylic acid. Preferably, the boiling point of the water:hydrocarbon azeotrope is 95°C or less.

Representative hydrocarbon:water azeotrope boiling points and percent water are: n-hexane 5 - n-hebutane 13 79 n-octane 23 90 n-nonane 40 95 Boiling points below 95°C Motsumizu: mono-branched C6-Ctzl'M aliphatic hydrocarbons forming a hydrocarbon azeotrope, aromatic hydrocarbons containing from 6 to 12 aliphatic hydrocarbons, and containing from 6 to 12 carbon atoms. 12 cycloalkanes, and mixtures thereof can also be used.

As pointed out in S,N, (C,N, 23,964), diluents are advantageous in that they increase the product yield by about 3 (mol)% without reducing the selectivity of the catalyst. be. Moreover, as explained below, the diluent has an additional function in the overall unitary process of producing methacrylic acid from propionic acid. Suitable diluents include n-hexane, n-heptane, n-octane, 2
-ethylhexane, n-decane, n-dodecane, 0. p
, or m-xylene, benzene, toluene, cycloalkanes and mixtures thereof. The concentration of diluent can range from about 10 to 50% by weight of the reactants in the main reactor.

The molar ratio of monocarboxylic acid compound to formaldehyde V 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 rate based on the amount of converted propionic acid.

The aldo-9-type condensation can be carried out at about 280 to 500°C, but it is preferably operated at about 280 to 350°C, since the lower the reaction temperature, the higher the selectivity. Co-pending application S registered on the same date in Smith's name
, N, (C,N, 23,133), the amount of undesired unsaturated cyclic ketone byproducts that are catalysts for the polymerization of (1) alpha(-terethylenically unsaturated monocarboxylic acids) is , from 4 mol % at 390°C based on the starting propionic acid compound, to 35
Approximately 2.5 mol% at 0°C or more
(approximately 1% at 25°C); alternatively, over 80 days of repeated condensation for 2+24 hours followed by decoking for <24 hours, the loss of cations is 75% at 390°C and at the same time Catalytic activity decreases, 35
At 0°C, it has a constant activity of 10%.

In some detail, this integrated method of producing methacrylic acid involves (1) feeding propionic acid and formaldehyde compounds into a reactor containing a silica catalyst, and (2) condensing formaldehyde and propionic acid under gas phase conditions. water,
producing a composition consisting of formaldehyde 9, propionic acid and methacrylic acid; (3) distilling the reaction product to remove water, unreacted formaldehyde and at least some propionic acid from the reaction product; (4)
This distillate is contacted in a distillation column with a co-distilling agent consisting of a water-immiscible diluent having an azeotropic boiling point of about 95°C or less to remove at least some of the water and formaldehyde overheads. , consisting of.

In a more preferred form of this method, a side wall extraction pipe is disposed at least in the middle of the distillation column to take out the composition comprising propionic acid and formaldehyde. The use of side wall extraction tubes is discussed in common application S,N, (C,N,2) registered in the name of Valeiko, which is incorporated herein by reference.
No. 3,004). S,
As pointed out in No. 1, (C,N, 23,004), this sidewall withdrawal tube facilitates the removal of a portion of the formaldehyde 9 from the aqueous mixture rising to the top of the column, thereby removing the bulk of the distillation column. Eliminating formaldehyde polymerization at the top, thereby eliminating or reducing the possibility of 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 column by reacting it with an alcohol having 6 to 12 carbon atoms to form hemiacetal. It is expected that water will be distilled from the hemiacetal and then the substantially anhydrous hemiacetal will be decomposed to recover formaldehyde. The formaldehyde can be removed from the alcohol by adding a water-immiscible diluent with an azeotrope of about 95° C. or less overhead to facilitate the removal of formaldehyde from the alcohol used to form the hemiacetal. It is separated from the attached sum.

The process of the invention can be carried out at a weight hourly space velocity (WH8V) of about 0.1 to 10, preferably o5 to 6.5. - For injection, the lower the weight-time space velocity, the lower the required reaction temperature. The higher the weight hourly space velocity, the higher the required reaction temperature.

The catalyst is decoked after about 12 to 72 hours of operation.

To prevent sintering of the silica gel, dilute oxygen to about 450 to 650°F (232 to 343°C), preferably 45°C.
Catalyst and exotherm at 0 to 550°F (232 to 288°C) approximately 10 to 30'F'' (5.5 to 16.7°C)
], increasing the oxygen content incrementally until the exotherm is reduced from about 10 to 306 F (5.5 to 16.7 C) until the exotherm disappears from the force of about 20% oxygen and about 80% inert. Increase the temperature with a mixture of gases, such as air, and then increase the temperature from 25 to 75°F (13.9 to 41.7
'C) Incrementally raise and decoke the heat generation by about 650
from about 10 to 30°F (5.5 to 16.7°C) to completion at 800°F (343 to 427°C)
hold back.

Generally, the present invention relates to a method for producing an alpha, ter, f-terenic unsaturated carboxylic acid compound, which method comprises (1) reacting a saturated aliphatic monocarboxylic acid compound with formaldehyde. (2)
The above saturated monocarboxylic acid compound and formaldehyde are condensed under gas phase conditions to produce an alpha beta ethylenically unsaturated monocarboxylic acid having one more carbon atom than the above saturated carboxylic acid in the presence of a solid catalyst from about 280°C. (3) After the coke is deposited on the solid catalyst, the supply of the aliphatic monocarboxylic acid compound and the formaldehyde compound to the reactor is stopped, and the oxygen-containing gas is transferred to the catalyst. Approximately 800°F (
427° C.) and repeating steps (1) and (2).

More specifically, the present invention relates to a method for producing an alpha bezer ethylenically unsaturated carboxylic acid compound, which comprises: (1) supplying a saturated aliphatic monocarboxylic acid compound and formaldehyde to a reactor; ) The above saturated monocarboxylic acid compound and formaldehyde are condensed under gas phase conditions to form a carbon atom containing 1 carbon atom from the above saturated carboxylic acid compound.
(3) After coke is deposited on the solid catalyst in the reactor, aliphatic monocarboxylic acid compounds and formaldehyde compounds are formed. to the reactor and pass diluted oxygen over the catalyst at a temperature not exceeding 650°F (343°C) with an exotherm of about 10 to 30°F (5.5 to 167°C); Increase the oxygen content incrementally, increasing the exotherm from about 10 to 30 °F (5.5 to 167 °C) until the exotherm disappears, and then gradually increasing the oxygen content to a mixture of about 20% oxygen and 80% inert gas, e.g., air. then increase the temperature from 25 to 75
Incremental increases in increments of 13.9 to 41.7 °F (13.9 to 41.7 °C) and decoking from about 650 to about 800 °F (343 to 42 °C)
Exotherm approximately 10-306°C until complete at 7'C)
F (from 5.5 to 16.7°C) and decoking.

In the following examples, all conversions, yields and selectivities are based on propionic acid (PA) unless otherwise specified.

Example 1 This example has a surface area of 119 m27E/ containing 1.97% by weight of cesium based on the dry weight of silica, and a porosity of 0.
．． Using a co-formed cesium phosphate, silica gel catalyst with 604CC/jj and an average pore size of 16si,
It explains the production of methacrylic acid in a pilot plant. A slurry of 29 parts by weight/ξ la-formaldehyde and 9.106 parts by weight of propionic acid (PA:FA molar ratio 3:2) and 47 parts by weight of hebutane was continuously evaporated to produce 7ξ la-formaldehyde at 400°.
The composition was then pyrolyzed to monomeric formaldehyde 9 at 204°F (204°G).
2,54CIrL), inner diameter 0834 inches (2,12C
TL), Inconel tubing with a length of 6 feet (180 cIrL) and an outside diameter of 0.25 inch (0.63 crrL).
) with a 200g catalyst and 1 on each side.
Inch (2,54cm) (7) 4 feet (including 120CIrL)
The reactor was transferred to a reaction system consisting of a tube with a catalyst zone of length. The thermowell was equipped with thermocouples inserted at 6 inch (15.3 crrL) intervals and electrical heating means were placed along the reactor.

The conversion of propionic acid and formaldehyde to methacrylic acid was carried out at a pilot plant temperature of 660°F (350'
C), 10 psig (9Ax2 to 0,7) and 1.
The test was carried out for 24 hours while being maintained at a weight hourly space velocity of 55.

The reaction products were collected and condensed in a heat exchanger. After 24 hours, the feed to the reactor was discontinued and the reactor temperature was increased to 550°F.
288°C). 2% oxygen in nitrogen was added slowly to the reactor to limit the exotherm during decoking to about 20'PC11,1°C). After the exotherm has ended, increase the oxygen content to 10% and reduce the exotherm to 20°F (11,1
After restriction to 'C), the nitrogen-oxygen mixture was replaced with air. After each exotherm, increase the reactor temperature to 50°F.
(27,8℃) and the reactor is 700'F (371'C).
This was achieved by precisely controlling heat generation until This decoking step typically takes 2 to 4 hours.

Air was continuously flowed through the reactor at 700°F (371°C) for a total of 24 hours.

The air was interrupted, the reactor temperature was lowered to 660'F (349°C), and the condensation of propionic acid and formaldehyde was initiated. Repeated condensation and decoking operations were performed for 80 days, 40 of which were 40 days were decoking in methacrylic acid production.The molar ratio of PA:FA was changed from 1.5:1 to 1.34:1.The physical properties of the catalyst before and after 80 days operation are shown in Table I. The yield after the first day and the first 66
The daily averages are shown below in Table I.

Table I Product Average Analysis of Initial Catalyst and Final Catalyst and Day 1 Product Analytical Values Cesium Content 197% by weight 1.76% by weight
Surface area 119m1ji 59rn
2/ji pore volume 0.604cc/,! il
O, 570C (Ill average pore diameter 168
A 302A,.

PA: FA molar ratio 1.5 1.3
4PA-standard conversion rate 32.1% 32.1
%PA standard selection rate 91.3% 85.9%
MA/PA yield 293% 276%FA
Standard conversion rate 519% 50.0% FA standard selectivity 84.9% 742% MA/FA yield 44.1% 37.15 The catalyst used in this example was 103% in 500cc of deionized water.
02.9 g of Nalcoag, 1034-A colloidal silica (made by vigorously stirring a solution of 34% solids 20OA and a solution of 111.66, P of supersium phosphate (with an average of 5 molecules of water per molecule) After 10 minutes of vigorous stirring, a solution of 100 g ammonium nitrate in 150 g deionized water was added to the sol and the mixture was stirred for 2 minutes at which point it began to thicken.The silica gel was left at room temperature overnight. The gel was dried to constant weight in a microwave bath, the particle size was adjusted from 20 to 40 meshes, and baked according to the following heating rate: 165°C for 2 hours, then gradually raised to 540°C. It was raised for 4 hours and then kept at 540° C. for a further 8 hours. All steps were carried out in flowing air.

Example ■ Commercial colloidal aphrodisiac, Ludotux (trademark) As −
40 brands [Tsilmin, Prauea] / +7) E, 1.
du Pont, de Nemours and
Go, (Inc,).

Industrial Chemical,s Dep
t,] was placed in a beaker. The temperature was 25°C.

This material was an aqueous colloidal dispersion of silica particles with a large specific surface area. The properties were as follows: specific surface area, 1307712/F; average particle size, 21 mμ.

Silify (as Si02), 40% by weight; 7) H(
25℃).

8.00 While stirring, lower the pH of the sample from approximately 10.5 to 3.
．． 0 by dropwise addition of concentrated nitric acid (0,16N).

The pH was then raised to about 6.0 by dropwise addition of concentrated ammonium hydroxide (0.15N) (D). The mixture was stirred for 8 hours at 25° C. at which point a viscous gel had formed. The gel was dried in a drying bath at a temperature of 120'C for 2
It was dried for an hour, then ground and sieved into 18/40 mesh grains (US sieves). The generated catalyst carrier was then heated to VC for 16 hours at 52
It was baked at 5°C. A, A.

Spectroscopy analysis results for aluminum:
400 ppm, sodium = 210 oppml:) ruconium: (100 ppm, titanium: (100 ppm,
Iron by Edasochus Spectroscopyni: (200p
p.m.

Met.

Initial wetness (incj, p) of IJium solution
It was added to the catalyst support using the ientwetness method. The resulting catalyst contained 6000 ppm of SoIJium.

The reaction system was a 1 inch (2,546 nl) OD with a 0.25 inch (0,636 In) OD thermowell.
Consists of heated Inconel tubing 0834 inches (2,12cx) by 6 feet (180Crn) inside diameter. The catalyst zone is typically 4 feet long (120 CT
L) and typically contains 200 g of catalyst.

The thermocouple inserted into the thermowell is 6 inches (15,3
Measure and control the temperature at CnL) intervals. The feed system is designed to handle a slurry of propionic acid-paraformaldehyde 9.

This slurry is transported into an evaporator in which paraformaldehyde is added in 4. Pyrolysis to monomeric formaldehyde 9 at OO°F (204°C). This system allows the use of lower reactor temperatures than feed systems using trioxane and propionic acid. Trioxane is 750
This is because at temperatures below .degree. F. (399.degree. C.), it will not completely decompose into monomeric formaldehyde.

The reaction conditions were: contact time: 3.2 seconds, reaction temperature = 390°C.
(734°F).

The reactor was filled with 4-8 mesh (American sieve) (3A) containing 96,000 ppm of IJ as described above.
24 inches (103.1 g) of AS-40 trisodium phosphate were charged. A two day test was carried out with a ratio of propionic acid to formaldehyde 9 of 1:1. The catalyst was regenerated as follows.

At a temperature of 550°F (288°C), 0.058C
Low flow rate air at FH was fed to the reactor along with 0.58 CFH nitrogen at approximately 20°F (11,
This resulted in an exotherm of 1°C). Gradually reduce the nitrogen flow while increasing the temperature by '20°F (11,,1°C) to 650°F.
(343°C), then 50°F (27,8°C) increments of 7
Raised to 50°F (399°C).

There was no exotherm above 30"FC (16,7°C) during this process. The catalyst was then heated to 750°F (750°C) for 48 hours.
399°C). Following regeneration, the reaction conditions used during the two-day test described above were repeated. The results are shown in Table 2. Table 2 shows that mild regeneration has minimal impact on catalyst performance.

Table 2 PA conversion rate % 37.3 37.0M
A selectivity mol% 58.4 55.5MA
Yield Mol% 21.8 20.8 Operating time after decoking 45 Note: All results are at 734″F (390°C); Contact time, 3.2 seconds; PA/FA≧1=1 , 4
-8 mesh using 6000 ppm Na Na3PO4'' silica gel catalyst. The selectivity is 5 and the yield is PA
It is a standard.

This regeneration method was repeated, but with the air heated to 1000°F.
(538°C). A large fever developed.

At an air flow of 250 ml/min and a temperature of 1000°F (538°C), the front of the catalyst bed experienced an exotherm of 430°F (221°C) during the first 10 minutes. The rate of temperature rise during this exotherm is also large, approximately 30'F/min (16,7
°C/min). 350°F (17
There was an exotherm (7°C) and a maximum temperature of 1350°F (750°C) was obtained. This occurred after 2 hours on air.

Table 3 shows the catalyst performance before and after decoking. The data is 6
Both the -8 mesh catalyst and the 18-40 mesh catalyst show a large yield loss after decoking.

The catalyst used in these experiments contained 6700 ppm Na and was prepared using an incipient wetness method.
It was a Na3PO4 catalyst made by The catalyst was then removed from the reactor in three portions and analyzed. These three catalytic cleavages have an initial uniform urine concentration of 670
3500ppm compared to 0ppm.

It contained 6,800 ppm and 17,600 ppm. Pore structure changes in silica gel probably occurred as well.

The results are in Table 3.

Table 3 1-1/1 36,565,123.81-2/2
29.777.823.111-3/3 29.0
70.320.448 hr replay-4/4 1.1,556.96.61-575
13.685,711.56-8 Mesh removal 18-407 Nunyu loading 2-1/6 40.2 5
9,1 23.72-2/7
36,5 66.4 24.248hr Regeneration 2-3/8 27.9 1
8.5 5.22-4/9
31.0 42.0 13.0 <Note):
CPA has a conversion percentage of hapropionic acid.

SPA is the selectivity mole % of methacrylic acid based on converted propionic acid.

YPA is the mole percent yield of methacrylic acid based on the propionic acid feed rate.

Claims (1)

[Claims] 1) A method for producing an alpha beta ethylenically unsaturated carboxylic acid compound, comprising: (1) reacting a feedstock consisting of a saturated aliphatic monocarboxylic acid compound and formaldehyde in a reactor; (2) condensing the above saturated monocarboxylic acid compound and formaldehyde in the presence of a solid catalyst under gas phase conditions,
(3) After the coke is deposited on the solid catalyst, the aliphatic monocarboxylic acid compound and the formaldehyde compound are formed. and (4) introducing oxygen-containing gas to the catalyst at about 800°F (427°F).
decoking at a temperature below ℃) and step (1
) and (2) repeatedly. 2) Place the oxygen-containing gas on the catalyst at 550°F (28
The exotherm is approximately 10°F (5.5°F) at temperatures not exceeding 8°C.
6°C) to about 30°F (16.7°C);
5.6°C) to about 30°F (16.7°C) with a mixture of about 20% (by volume) oxygen and 80% (by volume) inert gas until no exotherm occurs. increase;
Adjust the temperature of the above gas from 25°F (13.9°C) to approximately 75°C.
F (41.7°C) increments and reduce the above fever to about 10°F.
(5.6°C) to about 30°F (16.7°C),
and decoking increases the temperature of the gas by about 65
2. The method of claim 1, repeated to completion at temperatures from 0<0>F (343<0>C) to about 800<0>F (427<0>C). 3) A method according to claim 2, wherein said 20% (by volume) and 80% (by volume) mixture of oxygen and inert gas is air. 4) The method according to claim 1, wherein the alpha beta ethylenically unsaturated monocarboxylic acid compound is methacrylic acid. 5) converting the raw material feed from the first reactor to a second reactor or a multi-stage reactor, and decoking the catalyst in the first reactor in step (4); The method described in Section 1. 6) The method according to claim 5, wherein the catalyst in the second reactor or the multi-stage reactor is decoked by steps (3) and (4). 7) A method according to claim 1, wherein said saturated monocarboxylic acid is selected from the group consisting of acetic acid and propionic acid. 8) A method for producing an alpha beta ethylenically unsaturated carboxylic acid compound, comprising: (1) reacting feedstocks consisting of a saturated aliphatic monocarboxylic acid compound and formaldehyde in a reactor; (2) under gas phase conditions; The above-mentioned saturated monocarboxylic acid compound and formaldehyde are condensed to form a compound in which one carbon atom is removed from the above-mentioned saturated carboxylic acid in the presence of a solid catalyst comprising at least one cation of a group I or group II metal and a silica support. (3) after coke is deposited on the solid catalyst, stopping the supply of the aliphatic monocarboxylic acid compound and formaldehyde compound to the reactor; and (4) introducing an oxygen-containing gas onto the catalyst at approximately 800°F (42°F).
7° C.) and repeating steps (1) and (2). 9) Heat the oxygen-containing gas onto the catalyst at 650°F (34°F).
Reduces heat generation by approximately 10°F (5.6°C) at temperatures below 3°C
) to about 30°F (16.7°C); .7
with a mixture of about 20% (by volume) oxygen and 80% (by volume) inert gas; the temperature of the gas is increased from 25°F (13.9°C) to Approximately 75°F
(41.7°C) increments to reduce the above heat generation to about 10°F (5.0°C).
6°C) to about 30°F (16.7°C) and the increase in temperature of the gas to about 650°F (16.7°C).
9. The method of claim 8, wherein the method is repeated until completion at a temperature of from 343<0>C to about 800<0>F (427<0>C). 10) The method of claim 9, wherein said 20% (by volume) and 80% (by volume) mixture of oxygen and inert gas is air. 11) Claim 9, wherein the alpha beta ethylenically unsaturated monocarboxylic acid compound is methacrylic acid.
The method described in section. 12) Converting the raw material supply from the first reactor to a second reactor or a multistage reactor, and decoking the catalyst in the first reactor by step (4).
The method described in section. 13) The method according to claim 12, wherein the catalyst in the second reactor or multi-stage reactor is decoked by steps (3) and (4). 14) The method of claim 8, wherein said saturated monocarboxylic acid is selected from the group consisting of acetic acid and propionic acid. 15) The method of claim 8, wherein the catalyst is a co-formed catalyst.