JPS588075A - Preparation of high purity phthalic anhydride - Google Patents

Abstract

PURPOSE:To prepare the titled substance free from phthalide, by contacting crude phthalic anhydride obtained by the vapor-phase catalytic oxidation of o-xylene, with a gas containing molecular oxygen at high temperature in the presence of an Mn-containing alloy composition catalyst. CONSTITUTION:High purity phthalic anhydride is prepared by contacting a crude phthalic anhydride with a gas containing molecular oxygen at 200-300 deg.C for 5-30hr in the presence of an Mn-containing alloy compusition catalyst, and distilling the product. The amount of the molecular oxygen-containing gas is at least 2X10<-4> mole/hour reduced to oxygen gas based on 1kg of the crude phthalic anhydride. The Mn content of the catalyst is at least 0.05wt%, and the catalyst is preferably a Cr-Mn alloy, an Fe-Cr-Mn alloy, etc. Wherein the sum of the contents of Cr and Mn is >10wt%. The contacting area of the catalyst is preferably at least 0.002m<2> per 1kg of the crude raw material, and the contact is preferably carried out by charging the crude raw material in a mesh-type layer packed with the catalyst, and passing the oxygen-containing gas upward through the layer.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing highly pure phthalic anhydride by purifying crude phthalic anhydride obtained by catalytic gas phase oxidation of ortho-xylene. Specifically, the present invention provides the above-mentioned crude anhydrophthalic iI! The present invention relates to a method for producing highly pure phthalic anhydride by efficiently removing impurities such as phthalide, which are difficult to separate, using a catalyst.

Generally, it is widely practiced industrially to produce phthalic anhydride by catalytic gas phase acidification using ortho-xylene as a raw material using a vanadium-based catalyst. The main impurity contained in the by-product phthalide is 0.05 to 1 weight percent, which cannot be sufficiently separated using distillation equipment commonly used in industry, and is negligible in purified phthalic anhydride. It is well known that a significant amount of 7-thallide remains and this tends to degrade product quality.

Therefore, in the production process of phthalic anhydride, the catalytic gas phase oxidation reaction of ortho-xylene must be operated in such a way that the amount of phthalide, which is an impurity in the crude phthalic anhydride, is reduced as much as possible and kept at a low level. become. In other words, in order to suppress the decrease in the conversion rate of ortho-xylene and the increase in the amount of intermediate by-product phthalide due to the decrease in catalyst activity, it is necessary to raise the reaction temperature, which shortens the life of the catalyst. Then you will be especially connected. Even if this is not the case, the presence of by-product phthalide in crude phthalic anhydride is unavoidable, and various methods have been proposed for removing this phthalide in the industrial production of phthalic anhydride.

For example, according to the specification of Japanese Patent Publication No. 45-10333, there is a method of treating crude phthalic anhydride using an alkali metal sulfur compound such as potassium sulfite/hydrogen (KH8C) or potassium pyrosulfite (K2S205). is disclosed, and according to US Pat. No. 4,165,324, sodium hydroxide (Nail()) and potassium hydroxide (KO
A method of treatment using an alkali metal hydroxide such as H) is disclosed. However, it is pointed out that these methods have the following drawbacks and are difficult to be advantageously employed industrially.

First, in the former method, sulfur compounds coexist in the residue during the phthalic anhydride purification process, so a large amount of sulfur oxides are generated during the treatment of this residue (for example, incineration), causing pollution problems. In addition, the sulfur compound itself tends to cause corrosion of distillation equipment, which has the disadvantage that solving these problems requires a large amount of cost. In addition, in the latter method, since the alkali metal hydroxide itself has high reactivity, it becomes extremely dangerous depending on the floating water phthalate to be added.

That is, for example, when water/potassium atomized is added to liquid crude d% hydrophthalic acid, the maleic anhydride contained therein polymerizes explosively to form a coke-like compound. The oxidation is extremely sudden and severe, and cannot be ignored in the operation of the phthalic anhydride production equipment, and the coke-like polymerization that occurs can cause blockages in piping, valves, trays of distillation towers, etc. It has also been pointed out that the rapid reaction between potassium and maleic anhydride also leads to decomposition reactions of phthalic anhydride and other impurities, leading to a large drop in strength.

Further, a method of oxidizing phthalide using sulfuric acid is proposed in US Pat. No. 3,407,216 Mei A4. However, this method suffers from the disadvantage that the phthalic anhydride product is contaminated by sulfuric acid remaining after processing. therefore,
After the treatment, the sulfuric acid must be mixed with a basic substance, such as sodium charcoal, and then distilled to obtain the product.As a result, two treatments using two types of treatment agents are required, so the process is difficult. That in itself becomes complicated. Furthermore, sulfuric acid itself is a chemical that tends to corrode equipment, and sulfur oxides are generated during heat treatment, and the treatment of sulfur compounds that are mixed into the residue after distillation is expensive in terms of pollution prevention. You can also point out flaws.

Furthermore, a method of oxidizing phthalide using a blowing catalyst to obtain high-purity anhydrous phthalide has been proposed. For example, in US Pat. No. 3,208'423, heavy metal bromides such as cobalt bromide and manganese bromide It is added to crude phthalic anhydride and brought into contact with molecular oxygen gas. However, this method is difficult because bromide as a catalyst is expensive and it is extremely difficult to recover and reuse it.
This is a method that cannot be adopted industrially. In addition, in order to achieve the same purpose, West German Patent Publication No. 193500g discloses that a catalyst in which vanadium oxide is supported on a carrier is packed in a packed bed, and crude talic acid (anhydrous) is allowed to pass therethrough while air is passed therethrough. A method for performing the lateral ratio of phthalides is described. However, if you use this method, then! 8! It was found that the tar-like residue present in anhydrous phthalpochloride adheres to the surface of the supported catalyst, causing the activity of the catalyst to decrease in a very short period of time. Supported catalysts are originally formed by effectively dispersing and supporting a catalytically active substance on the surface of a carrier, and it is well known that the preparation method and calcination conditions greatly affect the catalytic activity. The method of packing such a supported catalyst inside a packed column and using it as a fixed bed is therefore difficult to use stably on an industrial scale.

The purpose of the present invention is to eliminate the above-mentioned drawbacks and to oxidize the by-product phthalide directly in split phthalic anhydride using a catalyst that is extremely easy to operate and maintain, thereby producing high-purity phthalic anhydride. VCt/).

The present invention is specified as follows.

11) Soil obtained by catalytic gas phase oxidation of ortho-xylene! #A method for producing high-purity phthalic anhydride, which comprises contacting phthalic anhydride with a molecular oxygen-containing gas at high temperature in the presence of a manganese-containing alloy composition as a catalyst, and then subjecting it to a distillation operation.

12) At least 2x10' of molecular oxygen-containing gas converted to oxygen gas per crude anhydrophthalic acid.
The method described in the above fil, characterized in that contact is carried out at a rate of mol/h, preferably from 4 x 1O to 2 x 10-2 mol/h.

(31 contact treatment at 200-300°C, preferably at 250°C)
The method according to (2) above, characterized in that it is carried out at a temperature range of -300°C for 5 - 30 hours.

+41 Contact area of manganese-containing alloy composition to crude phthalic anhydride IK4 is at least 0-002 rn
The method according to +11, +21 or +31 above, characterized in that N is preferably 0.004 to 4 m2.

・51 The manganese content in the alloy composition is at least 0.
05 weight factor, preferably 0.1 to 50 weight factor.

・6) The above (ri, +2
1, (3), 14) The method described in step (5).

Embodiments of the present invention will be further described below.

Crude phthalic anhydride obtained by catalytic gas phase oxidation of ortho-xylene usually contains 0.05 to 1.0 by weight of by-product phthalide.

Crude phthalic anhydride is stored in liquid form at 130-150°C and sent to a heat treatment process.

Manganese-containing alloys, such as those made of wires knitted into a net, are easily absorbed by molecular oxygen gas! The material used is one that has a large surface area as described above, and which causes no pressure loss. In particular, a method of forming and generating a net-like catalyst packed bed in a gas-liquid contacting device and performing heat treatment while contacting it with the catalyst is a simple and industrial method for carrying out the present invention.

When using a manganese alloy, at least 0.0% manganese is used.
0.05% by weight is preferred. Particularly preferred are chromium-manganese alloys and iron-chromium-manganese alloys, and those in which the total chromium and manganese content exceeds the 1O weight ratio exhibit optimal phthalide reduction ability when used in the method of the present invention.

The molecular oxygen-containing gas used is one containing 2 to 10 volumes of molecular oxygen, with the remainder being an inert gas such as nitrogen. Usually, air is further mixed with nitrogen gas to adjust the molecular oxygen concentration to the above-mentioned range.

Thus, by the method of the present invention, the amount of phthalide in the crude phthalic anhydride is reduced from 1/10 to 1/1000, and the purified phthalic anhydride obtained by distillation is no longer as heavy as phthalide ilO,05 or less. Phthalide, which is mixed into crude phthalic anhydride as a by-product, removes impurities along with its nearby boiling point compounds (the details of which are unknown, but are thought to be oxygen-containing compounds such as aldehydes). However, by reducing these impurity-containing ingredients, mainly phthalides, by the treatment method of the present invention, it is possible to increase the purity of phthalic anhydride, and at the same time improve the melt color and thermal stability of the resulting product. It was found that an improvement in the results was achieved.

The present invention will be explained in more detail below with reference to Examples.

Practical Example 1 Crude phthalic anhydride having the following composition was obtained by catalytic gas phase oxidation using ortho-xylene as a raw material.

Phthalic anhydride 99.7 weight Benzoic acid 0.05 N Maleic acid 0.07 # Phthalide 0.20 # Put the above @ manufactured phthalic anhydride a1~ into a flask, and pour a mixed gas of 5 volume parts of oxygen and 95 volume parts of nitrogen from the bottom. 3ood/
(equivalent to 6 x 10' mol/hour of oxygen) and treated at a temperature of 270°C for 30 hours. A wire-like iron (approximately 70
) - Chromium (approx. lc+1) - Nickel (approx. 9.4)
- Manganese (approximately 0.24, weight 4 each) alloy 200
9 was molded into a disc shape with a contact area of 1 m2 and a porosity of 9-7 m and was fixed.

The thus-treated phthalic anhydride contained 0.045 phthalide by weight.

This treated phthalic anhydride was distilled into a distillation column (inner diameter: 32 mm, height: 500 mm) equipped with 10 perforated plates.
Distilled under 5yHg (absolute) pressure with a reflux ratio of 0.5. As a result, purified phthalic anhydride with APRAIO1 freezing point of 131.12°C was obtained. The thermal stability of APRAl 0 by heating at 250° C. for 2 hours was also of high quality. It should be noted that this purified phthalic anhydride was bound to 0.04 times of phthalide.

Comparative example l 0.2 m wire 2002 with iron content 99.9v-It%
was molded into a disk shape with a contact area of 0-1 m2 and a porosity of 97, and was treated in the same manner as in Example 1. ′
After the treatment, phthalide was present in the phthalic anhydride in an amount of 0.19% by weight.

Then, this anhydrous phthalate was distilled in the same manner as in Example 1, resulting in APHA 20. Freezing point 130.8
'C purified anhydrous phthalate was obtained. Thermal stability after heating at 250° C. for 2 hours was APHA200. And in this phthalic acid sample water, phthalide is o, x8'ti4
It was included.

Practical Examples 2 to 12 and Comparative Example 2 In the operation of Example 1, a manganese-containing alloy of the following shape and composition was used as a catalyst, and its use -! : (Contact area), amount of blown oxygen, treatment temperature, and treatment time were changed in the same manner.

For comparison, a case in which no catalyst was used and a case in which molecular oxygen was not blown were also investigated. The results are shown in Table 1.

Example 13 Contact gas phase of ortho-xylene, +@ obtained by f conversion
The manufactured anhydrophthalic acid had the following composition.

Phthalic anhydride 99.3 times Ibenzoic acid 0.05 # Maleic acid 0.07 # Phthalic acid 0.03 II Phthalide 0.50 1 This crude phthalic anhydride 500 times was made into an inner diameter of 80Prnφ and a height of 120. was placed in a vertical treatment tank. 5 volumes jilt at the bottom
A dispersion plate for blowing 95 volumes of acid into a mixed gas containing one element;
A stirrer is provided on top of it, and after treatment, 500 manganese alloy nets made of the same material as used in Example 1 are used as the actual number of plates.
09 is installed in a plate shape. 150t of mixed gas
/ hour, and was heated to 270°C for 30 hours. After the treatment, a distillation column (inner diameter 3.2
L-n1φ, height 50. -rn) under a pressure of 55 int. Hg (absolute pressure) at a reflux ratio of 0.5 to obtain high purity phthalic anhydride having an APIA of 10, a freezing point of 131.12 DEG C., and a phthalide content of 0.04 wt. Thermal stability of this material after heating at 250'C for 2 hours was APF (A 20).

Claims (1)

[Claims] fil Crude phthalic anhydride obtained by catalytic gas phase oxidation of ortho-xylene is contacted with a molecular oxygen-containing gas at high temperature in the presence of a manganese-containing alloy composition as a catalyst, and then A method for producing high purity phthalic anhydride, the method comprising subjecting it to a distillation operation. (2) At least 2X molecular oxygen-containing gas converted into oxygen gas for the crude anhydrous phthal re i Kg.
A method according to claim fil, characterized in that contact is carried out at 10'mol/hour.・;(1 contact treatment is in the temperature range of 200~300℃, 5~
Claim a, boxed (
1) or the method described in (2). '41 'lA'll Phthalic anhydride a I Kg, the contact area of the manganese-containing alloy composition is at least 0.0
02m''
, (2) still the method described in (3). (5) The manganese content in the alloy composition is at least 0.
05 weight ratio (1)
), (2), (3) or (4). (6) The method according to claim (1), (2), (3), +41 or (5), which contains chromium in addition to manganese and the sum of the two metals is at least 10 parts by weight.