JP2000095725A - Production of unsaturated carboxylic acid - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the objective unsaturated carboxylic acid such as acrylic acid and methacrylic acid in increased space-time yield without lowering the selectivity of the objective compound by using a saturated hydrocarbon such as propane and isobutane as a raw material. SOLUTION: An unsaturated carboxylic acid is produced by the vapor-phase catalytic oxidation of a 3-8C saturated hydrocarbon in the presence of molecular oxygen and a catalyst. The catalytic reaction is carried out under a reaction pressure of >=152 Kpa while keeping the contact time to <=10 sec.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a method for producing a compound having 3 to 3 carbon atoms.
8 relates to a method for producing an unsaturated carboxylic acid by subjecting a saturated hydrocarbon of No. 8 to gas phase catalytic oxidation in the presence of molecular oxygen and a catalyst. Specifically, saturated hydrocarbons such as propane and isobutane are oxidized in the gas phase in the presence of molecular oxygen and a catalyst to produce acrylic acid from propane, methacrylic acid from isobutane, maleic anhydride and pentane from normal butane. To a method for producing maleic anhydride and phthalic anhydride.

[0002]

2. Description of the Related Art A process for producing an unsaturated oxygen-containing compound and / or an unsaturated hydrocarbon by subjecting a saturated hydrocarbon having 3 to 8 carbon atoms to gas-phase catalytic oxidation in the presence of molecular oxygen and a catalyst has already been known. Many have been proposed. Some examples have already been industrialized, such as the production of maleic anhydride from normal butane, but there are many that have not yet reached the area of industrialization. For example, a method for producing oxygen-containing compounds such as acrolein and acrylic acid and / or propylene using propane as a raw material is described in, for example, JP-A-55-66-1980.
No. 2041, JP-A-2-83348, JP-A-6-19
9731, JP-A-6-218286, JP-A-6-2
JP-A-79351 and JP-A-7-10801. Methods for producing oxygen-containing compounds such as methacrolein and methacrylic acid from isobutane and / or isobutylene are described in, for example, JP-A-55-6204 and JP-A-3-2.
0237, JP-A-4-59738, JP-A-4-59
739, JP-A-4-128247, JP-A-5-17
8774, JP-A-5-213799, JP-A-6-2
No. 11725, No. 7-33344, No. 7-1
No. 16071, No. 8-5820, No. 8-32
No. 644, Patent No. 2558036 and the like have been proposed. In addition, the applicants have also disclosed Japanese Patent Application Laid-Open No. 3-106839,
JP-A-7-10782, JP-A-8-12606, JP-A-9-12490, and JP-A-9-20700 are reported.

[0003] When an unsaturated oxygen-containing compound and / or unsaturated hydrocarbon is actually produced by using these production methods, the conversion of saturated hydrocarbon, the selectivity of the desired oxygen-containing compound, the space-time yield. (STY: production amount of target product per unit catalyst amount) and catalyst life are important factors. At present, except for the technology for producing maleic anhydride from normal butane, all of these factors must be considered. In fact, no satisfactory reaction method has been developed.

As for the conversion, since the reactivity of the saturated hydrocarbon as the raw material is extremely poor, the production of maleic anhydride from normal butane, in which the product is unlikely to cause sequential oxidation, or the use of unsaturated hydrocarbon as the raw material As in the production method, a catalyst and a reaction method satisfying the yield of the target oxygen-containing compound by only one-pass reaction have not been developed. Therefore, at present, a process of recycling unreacted saturated hydrocarbons must be adopted.However, in such a method, the reaction conditions were made severe, for example, by raising the reaction temperature in order to improve the conversion. In this case, the sequential oxidation of the unsaturated oxygen-containing compound and / or unsaturated hydrocarbon as the target compound proceeds, and the selectivity is extremely lowered. Further, there is an inconvenience that the catalyst life is shortened as the reaction temperature rises.

[0005] One of the important factors that determines the production cost of the target compound is the space-time yield. No matter how high the yield of the catalyst or process, if the space-time yield is low, the amount of catalyst and the reactor required to secure a given production volume will increase,
At the same time, the size of the incidental equipment is increased, so that the manufacturing cost is increased. Conversely, if the space-time yield is high, the production cost will be low, which is advantageous. In particular, in a process in which unreacted raw materials must be recycled, the improvement of the space-time yield has a large effect on the production cost.

[0006] However, in the current production technology, when the concept is referred to as the space-time yield, a very low example is not mentioned. As described above, when the oxidation reaction of these saturated hydrocarbons is performed at a low temperature in order to perform the oxidation reaction with a high selectivity, the conversion rate decreases. In order to improve the space-time yield in the oxidation reaction of these saturated hydrocarbons, the reaction is often performed by increasing the concentration of the raw material saturated hydrocarbon. For example, Tokiko 7-11607
No. 1, Japanese Patent Publication No. 8-5820, and Japanese Patent Publication No. 8-32644, when the isobutane oxidation reaction is carried out at a high isobutane concentration of 60%, the space-time yield is calculated. Despite the high reaction temperature of 340 ° C. or higher, the temperature of the thermostatic chamber containing the reaction tube is 1 mmol / g-cat / hr or lower. Furthermore, even at a constant temperature of 370 ° C., which is the upper limit temperature of use of the Keggin-type heteropolyacid catalyst, 2 m
It is about mol / g-cat / hr. Patent No. 2558
No. 036, in the same isobutane oxidation reaction, 50
Although isobutane concentration is as low as 280 ° C and the reaction temperature is as low as 280 ° C, methacrolein and methacrylic acid are synthesized with high productivity. However, the main product is methacrolein due to the use of a composite oxide catalyst containing phosphorus and vanadium, and further oxidization must be performed to obtain methacrylic acid, which is industrially disadvantageous. It is.

It is a well-known fact that the reaction pressure is increased by increasing the partial pressure of the reaction raw material. However, in the prior art, although there is a teaching of an example in which the concentration of the raw material is increased, the reaction pressure is increased by increasing the reaction pressure. No example of increasing pressure is known. In a normal gas phase oxidation reaction, the reaction rate is improved by increasing the reaction pressure, but it is also a well-known fact that the sequential oxidation from the target product proceeds, and the selectivity is lowered, which is not preferable. . Therefore, it is considered that the lower the reaction pressure is, the more preferable the prior art is. In fact, in the prior art relating to the oxidation of propane and isobutane, although the reaction pressure is described as being possible under pressurized reaction conditions,
The present applicant merely describes that "more preferably 2 atmospheres or less, and more preferably around normal pressure", and does not know any examples using a reaction pressure of 152 KPa or more.

[0008]

In view of such circumstances,
The present inventors use a saturated hydrocarbon such as propane or isobutane as a raw material, and in a method for producing an unsaturated carboxylic acid such as acrylic acid or methacrylic acid from the same without lowering the selectivity of a target product. The purpose of the present invention is to find a production method with a high production amount of the target product per unit catalyst, that is, an excellent space-time yield. They have found that they can be satisfied, and have completed the present invention.

[0009]

The present invention provides a method for producing an unsaturated carboxylic acid by subjecting a saturated hydrocarbon having 3 to 8 carbon atoms to gas-phase catalytic oxidation in the presence of molecular oxygen and a catalyst. A process for producing an unsaturated carboxylic acid, wherein the catalytic reaction is carried out at a contact time of 10 seconds or less and a reaction pressure of 152 KPa or more.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION In the practice of the present invention, a saturated hydrocarbon having 3 to 8 carbon atoms as a raw material for reaction includes propane, isobutane and the like. These are gaseous gas in the presence of molecular oxygen and a catalyst. Catalytic oxidation produces an unsaturated carboxylic acid such as acrylic acid or methacrylic acid. According to the present invention, various catalysts for producing an unsaturated oxygen-containing compound and / or an unsaturated hydrocarbon by subjecting a saturated hydrocarbon having 3 to 8 carbon atoms to gas-phase catalytic oxidation in the presence of molecular oxygen and a catalyst are provided. In the above reaction, while maintaining the optimum contact time under normal pressure reaction conditions or a value close to the holding time, the reaction pressure is increased to 152 KPa or more to carry out the reaction, whereby the number of carbon atoms as a raw material is reduced. Without lowering the conversion and selectivity of the 3 to 8 saturated hydrocarbon target compounds, the space-time yield is improved by the increase in the partial pressure of the raw material due to the increase in the reaction pressure.

The catalyst used in the present invention is obtained by subjecting a saturated hydrocarbon having 3 to 8 carbon atoms to gas-phase catalytic oxidation in the presence of molecular oxygen and a catalyst to convert an unsaturated oxygen-containing compound and / or an unsaturated hydrocarbon. As long as the catalyst is used in the conventional technology for production, regardless of its composition and form, improvement in productivity can be achieved under the reaction conditions proposed by the present invention. Specifically, a heteropolyacid catalyst mainly containing phosphorus and molybdenum, a composite oxide catalyst mainly containing phosphorus and vanadium, a composite oxide catalyst mainly containing phosphorus, molybdenum and vanadium, and a heteropolyacid catalyst , Niobium, molybdenum, vanadium, antimony-based composite oxide catalyst, phosphorus, molybdenum, vanadium, antimony and / or arsenic-based heteropolyacid catalyst, thallium-containing composite oxide catalyst, niobium, molybdenum, A composite oxide catalyst containing vanadium and tellurium as main components; a composite oxide catalyst containing bismuth, vanadium, molybdenum, and silver as main components; Above all, general formula PaMo
bVcXdYeZfOg (where P, Mo, V, and O represent phosphorus, molybdenum, vanadium, and oxygen, respectively, X represents copper,
Silver, bismuth, iron, cobalt, lanthanum, at least one element selected from the group consisting of cerium, Y is at least one element selected from the group consisting of alkali metals, alkaline earth metals and thallium, Z is arsenic, Antimony, boron, germanium, selenium and tellurium are shown, and subscripts a, b, c, d, e, f and g represent the atomic ratio of each element, and when b = 12, a, c and d are (It is a value of 3 or less not including 0 (zero), d, e, and f are values of 3 or less including 0, and g is a numerical value determined by the oxidation state and atomic ratio of each element other than oxygen.) It is recommended to use a catalyst comprising a partially neutralized salt of a Keggin-type heteropolyacid represented by

The reaction pressure that can be reached varies depending on the form and performance of the catalyst used, but it is preferable to always maintain the optimum contact time at normal pressure or a value close to the holding time. That is, the standard conditions (normal pressure, 2
The space velocity, which is the SV (unit / hr) obtained from the relationship between the supply rate and the amount of catalyst at 5 ° C.), should be increased twice if the pressure doubles, and triple if the pressure triples. As a result, the space-time yield is improved twice or three times without substantially changing the conversion and the selectivity, and the present invention can be achieved.

[0013] Regarding the reaction pressure, in a usual fixed bed flow type reactor, a certain amount of pressure rise occurs at the inlet of the reactor due to the charged catalyst. The pressure rise depends on the type of catalyst used, the bed length, and the space velocity of the reaction gas, but the reaction pressure used in the present invention is currently used industrially for gas phase oxidation reactions. This can be achieved by applying a pressure equal to or higher than the pressure increase that can be achieved under the reaction conditions. The pressure is 152 KPa or more when expressed in concrete numbers.

The concentration of the saturated hydrocarbon in the raw material gas supplied to the reaction is 1 to 85 mol%, preferably 3 to 70 mol%.
It can be carried out in mole%. In a reaction for producing an unsaturated oxygen-containing compound and / or an unsaturated hydrocarbon by subjecting a saturated hydrocarbon to gas-phase catalytic oxidation in the presence of molecular oxygen and a catalyst, the reaction rate is determined based on the primary concentration of the saturated hydrocarbon. In that region, the higher the concentration of the saturated hydrocarbon in the raw material gas, the higher the space-time yield and the industrially advantageous.

The concentration of molecular oxygen must be set in consideration of the concentration of the saturated hydrocarbon as the raw material and the fact that the concentration does not fall within the explosion range at that concentration. In addition,
As molecular oxygen, air, pure oxygen, oxygen-enriched air and the like are used.

The raw material gas supplied to the reaction includes, in addition to the raw material, saturated hydrocarbons and molecular oxygen, water vapor, rare gases, nitrogen, saturated hydrocarbons having different carbon numbers and / or structures from the raw materials, carbon monoxide. , Carbon dioxide, and unsaturated oxygenated compounds and unsaturated hydrocarbons as products. In particular, for water vapor, it is not just a diluent to avoid the explosion range and remove the heat of reaction,
The reaction system may be a reaction system or a catalyst system that participates in the reaction and has a favorable influence on the conversion, selectivity, and even the life of the catalyst. In such a system, water vapor is contained in a range of 30 mol% or less. Is preferred.

The present invention can be used not only in a fixed bed, but also in a reaction system such as a fluidized bed and a moving bed.

[0018]

According to the method of the present invention, the number of carbon atoms is 3
When producing unsaturated carboxylic acids by subjecting saturated hydrocarbons of the formulas (1) to (8) to gas-phase catalytic oxidation in the presence of molecular oxygen and a catalyst, it is extremely simple to regulate the contact time (reaction time) of the raw material with the catalyst and the reaction pressure. By the method, even if the same catalyst is used, the desired unsaturated carboxylic acid can be obtained with a higher space-time yield without lowering the selectivity of the target compound, and its industrial utility value is extremely high. Is big.

[0019]

EXAMPLES The present invention will be described more specifically with reference to the following examples, but the present invention is not limited to these examples. In the present invention, the definitions of space velocity, contact time, conversion, selectivity, and space-time yield (STY) are as follows.

Space velocity (1 / hr) = (source gas supply rate (standard state standard (ml / hr)) ÷ (catalyst amount (m
l)) Contact time (sec) = 60 × 60 × (reaction pressure (KP
a) / 100) {(space velocity (1 / hr)) conversion (%) = [(moles of reacted saturated hydrocarbon)}
(Mole number of supplied saturated hydrocarbon)] × 100 Selectivity (%) = [(Mole number of generated unsaturated carboxylic acid) ÷ (Mole number of reacted saturated hydrocarbon)] × 100 Space-time yield (mmol) / Ml / hr) = space velocity (1 / h)
r) × (concentration of raw material saturated hydrocarbon feed gas (%)) × (conversion (%)) × (selectivity (%)) ÷ 22.4 ÷ 10 ⁶

Example 1 85% orthophosphoric acid in 230 g of ion-exchanged water 21.
0g, copper phosphate Cu_Three(PO_Four)_Two・ 3H_TwoO 6.0
5 g, cesium nitrate 38.2 g, 60% arsenic acid aqueous solution
13.3 g was added, and the mixture was stirred and dissolved to form a uniform aqueous solution (referred to as solution A).
To do). Next, put the ion in a 1 liter autoclave.
330 g of exchange water was charged, and the temperature was maintained at 40 ° C.
Then, ammonium molybdate [(NH_Four)₆Mo₇O
₃₂・ 4H _TwoO] 296.5 g was added and dissolved by stirring.
Was. Thereto, the entire amount of solution A was injected to precipitate a slurry,
And then vanadium pentoxide V_TwoO_Five 6.36g
Was added. Heat the internal temperature of the autoclave to 120 ° C,
After performing the aging treatment for 12 hours, the
Was evaporated and a dry solid was removed. Drying of catalyst slurry
100 parts of dry solid, 4 parts of ceramic fiber, ion
Add 19 parts of exchange water, knead and extrude with 3mmφ
went. After the extruded product has been dried,
To decompose salt (deammonium nitrate, denitrifier)
After that, the catalyst was calcined at 435 ° C for 3 hours in a nitrogen stream.
And In this catalyst, the composition excluding oxygen atoms is Mo.₁₂V
_0.5P_1.5As_0.4Cu_0.3Cs_1.4And infrared absorption
From the spectrum and X-ray diffraction, cubic Keggin-type
It was confirmed that it had a lopolyacid structure. 4 ml of this catalyst
Into a glass reaction tube having an inner diameter of 15 mm,
37 mol%, oxygen 37 mol%, water vapor 16 mol%, remaining
At a space velocity (standard state base)
Quasi) Through the reaction tube at 2041 / hr,
Is increased to 200 KPa, and then activated at a reaction temperature of 329 ° C.
A sex test was performed. The contact time was 3.5 seconds.
As a result, the isobutane conversion was 7.1% and the conversion of methacrylic acid was
The selectivity was 55.5%. Based on space-time yield (STY)
The result was 1.33 mmol / ml / hr.

Comparative Example 1 Using the catalyst prepared in Example 1, an activity test was conducted in the same manner as in Example 1. However, the raw material gas was passed through the reaction tube at a space velocity (standard state standard) of 1025 / hr, and the reaction pressure was 100 KPa at normal pressure. The contact time was 3.5 seconds, and the reaction temperature was 33, which was almost the same as in Example 1.
The activity test was performed at 0 ° C. As a result, the conversion of isobutane was 7.6%, the selectivity of methacrylic acid was 57.4%, and the space-time yield (STY) was 0.74 mmol / ml.
/ Hr.

Example 2 Using the catalyst prepared in Example 1, an activity test was carried out in the same manner as in Example 1. However, the source gas passed through the reaction tube at a space velocity (standard state standard) of 2744 / hr, and the reaction pressure was 270 KPa. The contact time was 3.5 seconds, and the activity test was performed at 332 ° C., which was almost the same as the reaction temperature in the comparative example. As a result, the isobutane conversion was 9.0%,
The selectivity of methacrylic acid was 51.9%, and the space-time yield (S
TY) was 2.12 mmol / ml / hr.

Comparative Example 2 Using the catalyst prepared in Example 1, an activity test was conducted in the same manner as in Example 1. However, the amount of catalyst used was 0.5
ml, and the raw material gas has a space velocity (standard state standard) of 20.
The activity test was performed at a reaction pressure of 100 KPa at normal pressure and a contact time of 1.8 seconds at 59 / hr. However, at this time, the temperature of the reactor was set at 3 so that the space-time yield (STY) was maximized.
54 ° C. As a result, the isobutane conversion was 8.3%,
The selectivity of methacrylic acid was 50.4%, and the space-time yield (S
TY) was 1.41 mmol / ml / hr.

Example 3 Using the catalyst prepared in Example 1, an activity test was conducted in the same manner as in Comparative Example 2. However, the source gas passed through the reaction tube at a space velocity (standard state standard) of 7605 / hr, and the reaction pressure was 370 KPa. The contact time was 1.8 seconds, and the reaction temperature was set to 3 in the same manner as in Comparative Example 2.
55 ° C. As a result, the isobutane conversion was 12.0.
%, The selectivity of methacrylic acid is 43.8%, and the space-time yield (STY) is 6.60 mmol / ml / hr.
Met.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Toshiaki Ui 5-1 Sokai-cho, Niihama-shi, Ehime Sumitomo Chemical Co., Ltd. (72) Inventor Koichi Nagai 5-1 Sokai-cho, Niihama-shi, Ehime Sumitomo Chemical F-term (reference) in Kogyo Co., Ltd.

Claims (3)

[Claims] 1. A process for producing an unsaturated carboxylic acid by subjecting a saturated hydrocarbon having 3 to 8 carbon atoms to gas-phase catalytic oxidation in the presence of molecular oxygen and a catalyst to produce an unsaturated carboxylic acid. A method for producing an unsaturated carboxylic acid, wherein the method is carried out at a reaction pressure of 152 KPa or more for seconds or less. 2. The method for producing an unsaturated carboxylic acid according to claim 1, wherein the saturated hydrocarbon having 3 to 8 carbon atoms is propane and the unsaturated carboxylic acid is acrylic acid. 3. The process for producing an unsaturated carboxylic acid according to claim 1, wherein the saturated hydrocarbon having 3 to 8 carbon atoms is isobutane, and the unsaturated carboxylic acid is methacrylic acid.