JPS6084243A - Preparation of unsaturated carboxylic acid - Google Patents

Abstract

PURPOSE:To obtain the titled substance efficiently by direct conncetion method of first and last stages, by using a catalyst for first-stage oxidation consisting of Mo, Bi, Fe, Co, Ni, Ag, K, P, Ce, O, etc. in a reaction between an olefin having a specific number of C atoms in the straight chain and molecular oxygen. CONSTITUTION:In preparing an unsaturated carboxylic acid (e.g., methacrylic acid) by subjecting an olefin (e.g., isobutylene) having 3 carbon atoms in the straight chain to a vapor phase contact reaction, the vapor phase contact oxidation is carried out by the use of a catalyst for first-stage oxidation shown by the formula (R is K, Rb, Cs, or Tl; S is P, As, or B; T is Ce, Ti, Zn, etc.; a-j are number of atoms of each element), the prepared reaction mixture is neither separated nor purified, and directly subjected to vapor phase contact oxidation by the use of a catalyst for last-stage oxidation, to give the desired substance. EFFECT:Since an unsaturated aldehyde is obtained in high yield and in high selectivity even if conversion ratio of olefin is high, and an amount of by-products is small, the last-stage oxidation can be carried out directly.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a novel method for producing unsaturated carboxylic acids, and particularly to a method for efficiently producing methacrylic acid from inbutylene.

Definitions of terms used in the present invention are as follows.

"Olefin J...Olefin having 5 carbon atoms in a straight chain such as propylene and imbutylene 0 "Preliminary oxidation"...Olefin is subjected to a gas phase catalytic reaction with molecular oxygen at high temperature in the presence of a catalyst. , a reaction that produces the corresponding unsaturated aldehyde.

"Sub-stage oxidation": A reaction in which the unsaturated aldehyde is subjected to a gas phase contact reaction with molecular oxygen at high temperature in the presence of a catalyst to produce the corresponding unsaturated carboxyl group.

"Directly connecting the front and rear stages": A method for producing unsaturated carboxylic acids from olefins by supplying the gaseous reaction mixture produced in the first stage oxidation to the second stage oxidation section and oxidizing the second stage.

"Olefin oxidation catalyst ffj or "first stage oxidation catalyst"...
・Catalyst used in first-stage oxidation.

"Late stage oxidation catalyst"...Catalyst used in the stage oxidation.

Preliminary oxidation of olefins such as propylene and isobutylene to corresponding unsaturated aldehydes such as acrolein and methacrolein;
The subsequent oxidation to the corresponding unsaturated carboxylic acid such as methacrylic acid is well known.In addition, when producing the corresponding unsaturated carboxylic acid from an olefin, the unsaturated aldehyde is separated and purified from the reaction mixture obtained in the first stage oxidation. Two methods are known: a method in which post-stage oxidation is carried out after oxidation, and a method in which the front and rear stages are directly connected and carried out in one step (British Special Edition No. 939713). It has advantages in terms of equipment, operation, and economy due to the fact that it is unnecessary, and is considered to be advantageous from an industrial perspective.

However, in general, the reaction performance of the front-end and front-stage direct coupling method is significantly inferior to that of the case where only the second-stage oxidation is performed independently using purified unsaturated aldehyde as a raw material, and this tendency is particularly high when producing methacrylic acid from imbutylene. Therefore, to date, no proposal has been made to enable industrial production of methacrylic acid by a direct front-to-back process.

The cause is thought to be impurities produced as a by-product in the first-stage oxidation and residual unreacted imbutylene, but the inventors conducted a detailed study on this cause and found that the reaction mixture of the first-stage oxidation contains In addition to unreacted isobutylene and tar-like byproducts, unsaturated hydrocarbons such as diisobutylene, benzene, toluene, xylene, and ethylbenzene are present, and these unsaturated hydrocarbons are combined with unreacted inbutylene and tar-like substances. Similarly, it has been found that this is the main cause of deterioration in reaction performance in post-oxidation.

That is, when producing gold methacrylate from inbutylene by the front-back direct coupling method, it is necessary to develop a new oxidation catalyst that simultaneously satisfies the following two conditions, which are considered to be antinomic requirements.

■ High conversion rate of inbutylene, reducing unreacted inbutylene.

■ Low by-products of unsaturated hydrocarbons such as diisobutylene, benzene, toluene, xylene, and ethylbenzene as well as tar-like substances 0 In addition to these conditions, of course, high selectivity to M A and L It must also satisfy the requirements for industrial applications, such as single-stream yield (which is linked to high quality) and long catalyst life.

Therefore, the present inventors conducted intensive studies to improve the shortcomings of the prior art, and found that when using a first-stage oxidation catalyst with a specific composition, it was surprisingly possible to do so without inhibiting the second-stage oxidation reaction. It was discovered that efficient direct connection between the front and rear stages was possible [7], and the present invention was fully completed.

Therefore, the purpose of the present invention is to create a straight chain! An olefin having one carbon atom and molecular oxygen are represented by the following membrane composition formula [
This is achieved by carrying out vapor phase catalytic oxidation using a pre-stage oxidation catalyst represented by [2], and then subjecting the resulting residue to vapor-phase catalytic oxidation using a post-stage oxidation catalyst.

General composition formula [I]: MOa Bib Feo 00d Ni6 A8f R
g8B.

Ti Oj is \, R1''J: represents at least one element selected from Rb, Cs and Tj, and 8
is a small element selected from P, As, and B; T is Os, Ti, To, Zn, Go,
Sn, Or.

Ga, La, In, AJ, cd, Pd, Mn
, V, Pb, Nb, Zr.

A small number selected from Cu and U (both represent a kind of 5'Q element, '+ ''+ c* d+ j f+ L J '
and j are Mo, B1. Feo CO*'L
The number of atoms of Ag, R, S, T and 0, a=12
In this case, b = o, i~10, c-0,5n4
0. +1-0~12. e=0-12, d+e=0.
5-15. fxo, 1-8. g=0.01-5. h-
0-5. x-0 to 12, and j is the number of oxygen atoms that satisfies the valences of other elements. ) In the above catalyst of the present invention, the preferred component ratio of the catalyst is a
When = 12, b = 0.5~7, c = 1~3
5, a=o~10. θ=0~io, a+θ=05~
12. f=0.1-6. g=0.01-4. h=.

~4. i=takes a value of o to 8, and j is determined by the number of oxygen atoms satisfying the valence of other elements.A more preferable catalyst component ratio is when a=12, b=0.5 to 7 ．． c.
-8P-30, a = 0 to 10. e −0~, 10
゜d 10e = 0.5~12, , f = 0.
1-4. g=0.01-3. h=0-3. i=0~8
, and j is the number of atoms that satisfies the valence of the other 7c atoms.0 Although the exact structure of the catalyst of the present invention is not clear, the composition of the components constituting the catalyst is basically as described above. It is represented by a general formula.

Such pre-oxidation catalysts can be prepared by various methods known in this field, such as evaporation to dryness method, oxide mixing method, coprecipitation method, etc. Any substance that constitutes the catalyst of the present invention by calcination may be used, and examples thereof include ammonium salts of each element, nitrates, carbonates, organic acid salts, salts such as halides, free acids, Examples include acid anhydrides, condensed acids, molybdenum-containing heteropolyacids such as phosphomolybdic acid and silicic monobdic acid, and heteropolyacid salts thereof such as ammonium salts and metal salts. Furthermore, the use of silicon-containing compounds such as silicon molybdic acid does not adversely affect the catalyst activity. The firing process is carried out at 450 to 700°C for about 4 to 16 hours, but if necessary, a primary firing process may be performed at a temperature lower than this firing temperature, followed by a firing process at the above temperature.

The catalyst can be used as is, but it can also be used by attaching it to a carrier of an appropriate shape, or diluting it with a carrier (diluent) in the form of powder, sol, or gel. Any known O carrier may be used,
For example, titanium dioxide, silica gel, silica sol, diatomaceous earth, silicon carbide, alumina, pumice, silica-alumina,
Bentonite, zirconia, zeolite, refractories, etc. are suitable, and carriers containing silicon are particularly preferred. The amount of carrier can be selected appropriately. The catalyst can be in a suitable form such as powder or tablet, and can be used in any of the fixed bed, moving bed, and fluidized bed methods.

The pre-oxidation catalyst of the present invention is useful for the oxidation of prohylene, imbutylene, isobutylene, etc., particularly for the oxidation of isobutylene, but these olefins do not necessarily have to be highly pure and may contain impurities. However, there are many impurities that may include unsaturated hydrocarbons in the reaction gas obtained in the first-stage oxidation (it is not desirable for them to be mixed in). Of course, molecular oxygen can be used alone, but In addition, in this reaction, it is possible to dilute with inert gas, such as water vapor, nitrogen, argon, carbon dioxide, etc., which does not adversely affect the reaction. Dilution is preferred.

The conditions for the first-stage oxidation reaction in the present invention are not limited to (other than the use of a specific first-stage oxidation catalyst), and can be easily determined by experiment if the second-stage oxidation catalyst to be used is given. Therefore, the reaction conditions for the first stage oxidation in the front and rear direct coupling method are not uniquely determined, but the reaction temperature is usually 250 to 700°C, preferably 25°C.
0 to 550°C, reaction pressure is normal pressure to 10 atm, SV of total feed gas is 20 (] to 10,000 hr, preferably 30 (1 to 4,000 hr'-'), olefin concentration is 0
5 to 10 volume ratio, preferably #-i 0.5 to 8 volume ratio, olefin volume to oxygen ratio of 1:1.5 to 7, preferred feed gas composition: olefin:air:steam = 1, 5 to 3
The ratio is 0:5 to 90 (mol).

In the present invention, the first-stage oxidation reaction is carried out under conditions such that substantially no unreacted olefin remains, which would be a factor inhibiting the second-stage oxidation reaction, that is, the olefin conversion rate is at or close to 100%. Even in that case, unsaturated aldehydes can be obtained in high yield and high selectivity, and by-products that would inhibit the subsequent oxidation reaction are not produced.

In particular, when using isobutylene as an olefin, M and AL can be obtained in high yield and with high selectivity, which is not seen with known catalysts, even if only the results of the first stage reaction are considered.

This advantage of the present invention is that Ag during formation of the first stage oxidation catalyst is
This is specifically controlled by the presence of ff1, and in the absence of these components, the catalyst has low activity (and moreover, Mll formation of unsaturated hydrocarbons is intense).

In addition, in the case of known catalysts with similar general composition formulas,
In general, when ν012 is set, good performance is shown in a very narrow range of Fe composition ratio of 05 to 3 (for example, Japanese Patent Publication No. 17253/1983), whereas in the first stage oxidation catalyst of the present invention, the Fe composition ratio is 05 to 3. It shows high activity over a wide range of 40 to 40, and particularly shows excellent performance even when the Fe composition ratio is in a relatively high range of 8 to 30.

The generated gas obtained in the first stage oxidation reaction is then subjected to the second stage oxidation reaction without being condensed, where it is oxidized to an unsaturated carboxylic acid.

The post-oxidation catalyst used may be any catalyst as long as it has a catalytic ability to oxidize unsaturated aldehyde to unsaturated carboxylic acid, and it may be used supported on a carrier or diluted with a diluent, if necessary. Examples of the catalyst include (1) P-Mo
-R (R represents Tj, at least one alkali or alkaline earth metal element) system, or further Si, Or
, Aj, Go, Ti, V, W.

Bi, Nb, B, Ga, Pb, En, Co
, Pa, As, 'Zr, Sb.

To, Fn, Ni, In, Cu, Ag, Mn
, an oxidation catalyst containing at least one element selected from La, Nd, Ta, f3rn, etc., f21P
-M o -A e-based oxidation catalyst, (3) P-M'o-
As-alkali metal element system or further V, W,
An oxidation catalyst containing at least one type of carbon atoms such as Cu, Fe, Mn, Sn, etc.
, Pb, Or, sn, Bi.

Oxidation catalyst containing a small amount of Ou, Ni, Mg, Oa, Ba, Zn, etc.
-Mo-Pd based oxidation catalyst, tel P-Pa-s b
system or further Bi.

pb, Or, Fe, Ni, Co, Mn, Sn, U, Ba
Examples of known catalysts include oxidation catalysts containing at least one element such as oxidation catalysts, and catalysts containing ammonium groups.

The second stage oxidation is carried out under substantially the same conditions as the first stage oxidation, but the specific conditions are selected depending on the catalyst used. The germination process is carried out using the pre-arrangement reaction mixture obtained under the above-mentioned reaction conditions as a feedstock and under reaction conditions suitable for the catalyst used in (a).

According to the present invention, the conversion rate of olefin can be increased.

Even if the concentration of unsaturated aldehyde is increased, the yield and selectivity of unsaturated aldehyde can be obtained with very little by-product of unsaturated hydrocarbons such as diynebutylene, benzene, 1' toluene, xylene, and ethylbenzene. First stage 6 for J. The unsaturated aldehyde produced in the oxidation reaction can be directly converted into an unsaturated carboxylic acid without isolating it, and the conversion rate of the unsaturated aldehyde in the subsequent oxidation reaction, the selection of the unsaturated carboxylic acid, and the convergence are substantially reduced. The present invention will be explained in detail with reference to Examples below.
The reaction rate, selectivity, and single flow yield in the examples are as shown in the following formula. All analyzes were performed by gas chromatography. Furthermore, the representation of oxygen in the catalyst components is omitted for the sake of brevity.

The meanings of the symbols are: i-B is inbutylene, MALi is methacrolein, and MAA is methacrylic acid.0 Also, when using zolobylene instead of inbutylene, the reaction results are calculated using the following formula: 1-B Wopropylene, MAL
k Acrolein, based on the formula where MAA is read as acrylic acid.

[Pre-stage oxidation reaction result calculation formula]

Unsaturated hydrocarbons production rate (%) [Sub-stage oxidation reaction result calculation formula] Unsaturated hydrocarbons conversion rate (%) MAA single flow yield (1-B standard) (%) Example 1 A, Preparation of catalyst Bismuth nitrate 48.5 F, Nit rR Kobal M16.5
Nickel nitrate 291♂, Ferric nitrate 4B 4.8
11 Silver nitrate 1Z01, Nitrate fij < Potassium 10. IS
'f-150d was added to water and heated to obtain liquid iA. On the other hand, ammonium molybdate 212y-f4
The humidified j9'l L and 85% phosphoric acid 5767 were added to 00 ml of water to make an ff3 liquid. Add solution B while heating and stirring solution A, evaporate to dryness while stirring thoroughly,
After drying this at 120°C for 8 hours, it was dried at 600°C for 1 hour.
Calcined in a Matsufuru furnace for 6 hours, the equated solid was pulverized and divided into 4 to 8 meshes.The composition of the catalyst thus produced R1,4 was MO12BiI Fe12 C04N'l Ag1 p
Indicated by tts Kl.

Next, various catalysts having different composition ratios as shown in Table 1 were prepared according to the same procedure.

B0 reaction method The reaction was carried out by the front and rear direct connection method as follows. (1) If forging reaction force method, catalyst 100 m, lf inner diameter 2.5, eccentric length 60 ate.
was charged into a stainless steel reaction tube and heated in a metal bath, and the molar ratio of inbutylene:air:steam was 4:55:4.
A feed gas of 1 was passed at a space velocity of 2DOOhr'.

(2) Post-stage oxidation reaction method As the post-oxidation catalyst, Mo-P-Ol described in Example 1 of Japanese Patent Publication No. 50-10846 1j/fil+%
l-Cr catalyst [Mo:P:Os:Cr=l:U,
16:0.16:016 (atomic ratio), calcined at 450°C, catalyst diameter 4-8 mesh) 10mgl inner diameter 2.5cm x 60cm long stainless steel reaction tube was filled with metal i?
; The reactant gas which had been oxidized by the above-mentioned first stage oxidation was passed through it.

The results of the obtained first-stage oxidation reaction and second-stage oxidation reaction are shown in Table 1.10 In Table 1, the reaction temperature is shown as the metal bath temperature held constant (the same applies hereinafter). No catalyst (experiment numbers 8 and 9)
) and Japanese Patent Publication No. 47-3204 known as a first-stage oxidation catalyst
Catalyst described in Example 1 of Publication No. 4 (Experiment No. 10)
), Catalyst described in Example 1 of the specification of Japanese Patent Publication No. 47-32043-+j (Experiment No. 11), Japanese Patent Publication No. 47-428
Catalyst described in Example 3 of Publication No. 13 (Experiment No. 1
2), and the catalyst described in Example 1 of the specification of Japanese Patent Publication No. 48-17253 (Experiment No. 13) prepared according to the description of each specification (catalyst diameter 4 to 8 mesh), these catalysts were subjected to pre-oxidation. Experiment number 1 except for use in reaction
A direct connection reaction between the front and rear stages was performed using the same material as in ~7.

Furthermore, pre-purified methacrolein (purity 995 wt'5i-%) was supplied to the second stage oxidation catalyst, and the emptying rate was 2000 hr, and the total methacrolein composition was 0.
2:N2:H20=1:1.5:15.0:17.5(
molar ratio], and the results are also listed in Table 1 (Experiment No. 14).

From the results in Table 1, it can be seen that when using a first-stage oxidation catalyst containing Ag, not only is the first-stage oxidation reaction excellent, but also the second-stage oxidation reaction has good results comparable to when purified methacrolein is used. I know how to give. - In the case of a catalyst that does not contain Ag, there is a large difference in the performance of the first-stage oxidation reaction, and the performance of the second-stage oxidation reaction is also poor. Furthermore, it has been found that the pre-oxidation catalyst of the present invention exhibits far superior performance compared to known catalysts having similar compositions. A catalyst was prepared in the same manner as the original catalyst except for adding Ce, Zn, Or, An, Q6, and w6, and a front and rear direct coupling reaction was performed in the same manner as in Example 1. The results are shown in Table 2.

Example 6 Each of the catalysts shown in Example 1 and Example 2 was prepared in the same manner as the original catalyst when the S component was arsenic or boron, and when the R component was rubidium, cesium, or thallium. Then, in the same manner as in Example 1, a direct reaction between the front and rear stages was carried out. All results are shown in Table 3. Example 4 The front and rear direct reactions shown in Examples 1 to 6 were maintained under the same reaction conditions and continued for 1000 hours, and changes in reaction results were investigated. The results are shown in Table 4.

From the results in Table 4, it can be seen that the Ag-containing pre-oxidation catalyst has a high conversion rate and high selectivity in the pre-oxidation (and produces very little unsaturated hydrocarbon by-products, so it is suitable for the direct coupling method). It can be seen that it is suitable as a catalyst.-The catalyst that does not contain the above components (Experiment No. 4) has poor performance in the pre-oxidation stage and produces many by-products of unsaturated hydrocarbons. It can be seen that in the method of directly connecting the front and rear stages as a catalyst, the life of the rear stage oxidation catalyst is shortened.

Example 5 A direct reaction between the front and rear stages was carried out in exactly the same manner as in Example 1, using the front-stage oxidation catalyst used in Examples 1 to 3, except that inbutylene was replaced with furopylene. The obtained reaction results are shown in Table 5. For comparison, in addition to the post-oxidation catalyst used in Example 1, purified acrolein (purity qq, 6M %) was used as acrolein to be supplied to the post-oxidation section. At a space velocity of 2000 hr, the feed gas composition is acrolein:
02: N2: H20=1: 1.5:1
3.0:17.5 (molar ratio), and the reaction was carried out using the same post-oxidation reaction method as in Example 1, and the results are also listed in Table 5 (Experiment No. 4)0

Claims (1)

[Claims] 1. An olefin having three carbon atoms in a linear chain and molecular oxygen are oxidized in a vapor phase using a pre-oxidation catalyst represented by the following membrane composition formula CI], and then the obtained A method for producing an unsaturated carboxylic acid, the method comprising oxidizing the produced gas in a vapor phase catalytic manner using a post-oxidation catalyst. General composition formula [I]: Mo, Bib Fe, cod Nio AgfRg 5
hT1 0j \, R is Rb, Co and T
represents at least one element selected from j, S represents P
, All, and B (both represent a type of element, T is Oe, Ti, Te, Zn, Ge, Sn, Or, Ga, La, In, Aj, Od
, P(1, Mn, V. Pb, Nb, Zr, C! A small number selected from u and U (both represent a type of element, '+ b+ c + d
+ e, f, g, h rl and j are respectively Mo, Bi, Fe, Co, Ni, Ag. It is the number of atoms of R, 8, T and O, and when a-12, b = o, i~10. e-0,5~40. d=0
~12, e = (1-12, d+o = 0.5 ~ 15.
f=o, IP-8, g=0.015. h=0n5.
i=0 to 12, and j is the number of oxygen atoms satisfying the valences of other fluorine atoms. 2. The catalyst according to claim 1, wherein the olefin is pyrene or isobutylene. 6 Claim 1 in which the post-oxidation catalyst contains phosphorus, molybdenum, or phosphorus and palladium as essential components.
The method described in section. 4. When the composition of the first stage oxidation catalyst is a-12, b-
[Go to 1, 5 7. e=1-35. d20~10°e =
O = 10, 6 + e = 0.5-12, f
=0.1~6. g=o, 01-4. h=o~4. i
2. The method according to claim 1, wherein the number of oxygen atoms takes a value from 0 to 8 and satisfies the valences of other elements. 5. When the composition of the first stage oxidation catalyst is a=12, b
= 0.5-7, c = 8 A-ri 0, 6
= O-10. e = 0--1 0, 6 + e = 0.5~
1 2 , f = 0.1A-4, g = 0.01-5.
hi 0-5. The method according to item 1, in which a value of 8 is taken for i-0, and j is determined by the number of oxygen atoms satisfying the valences of other elements.