JPH0261020A - Parts for equipment handling acetic acid and acetic anhydride - 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] [Industrial Application Field] The present invention relates to a member for equipment that simultaneously handles acetic acid and acetic anhydride, and more specifically, to react, cool, evaporate, concentrate, and heat at a high temperature of 300°C or higher. The present invention relates to parts for acetic acid and acetic anhydride handling equipment that exhibit excellent corrosion resistance and durability in equipment used for purification, transportation, and storage purposes.

[Prior art and problems to be solved by the invention] In the field of handling organic acids, for example, the field of synthetic acetic acid production that handles acetic acid, it is necessary to prevent local corrosion such as pitting corrosion, intergranular corrosion, and corrosion cracking in reaction vessels, etc. Therefore, glass lining, aluminum, 5O3316, etc. are used. however,
In a high temperature environment of 300° C. or higher, it is difficult to use various types of stainless steel, and there is currently no suitable material. For example, in the production of aromatic polyester, a diol component is acetylated with acetic anhydride and then subjected to a polycondensation reaction with a dicarboxylic acid component. During this polycondensation reaction, acetic acid is produced as a by-product, and the reaction temperature is 300°C or higher, so
Under these environments, various stainless steels have sufficient corrosion resistance,
Does not exhibit durability. In particular, it is a cause of corrosion cracking in the heat-affected zone, and furthermore, there is a problem of contamination of the product itself due to metal ions eluted by corrosion.

As described above, there is no material that has excellent corrosion resistance and durability in a high-temperature environment of 300° C. or higher, and there is a need for an appropriate material that does not cause corrosion or trouble in this environment.

[Means for Solving the Problems] In view of the above-mentioned current situation, the present inventors have developed a material that has excellent corrosion resistance and durability even in environments where acetic acid and acetic anhydride are handled at high temperatures of 300°C or higher, and even in heat-affected zones. In order to provide equipment for handling acetic acid and acetic anhydride that does not cause corrosion cracking or contamination of the product itself, we have investigated various materials and have found that certain alloys can be used in such environments. This discovery led to the completion of the present invention.

Hereinafter, production of aromatic polyester will be described in detail as an example of handling acetic acid and acetic anhydride.

In melt polycondensation of aromatic polyester, a diol component is reacted with acetic anhydride to synthesize an acetylated product. Subsequently, it is reacted with a dicarboxylic acid component and the combination temperature is 300°C to 300°C.
By-product acetic acid is distilled off while raising the temperature to 50°C. Therefore, acetic anhydride and acetic acid are present in a high-temperature environment, which is extremely corrosive. The present inventors conducted extensive studies on the materials of this reaction vessel, and found that Cr, MO, Fe, and W were used.

consisting of one or more elements selected from the group of Cu and Co, and the remainder substantially Ni, the Cr being 2 to 50% by weight, the MO being 1 to 17fff Q%, An alloy having a composition of 1 to 30% by weight of an element selected from the above group, preferably 50 to 70% by weight of Ni.
Cr10 to 20% by weight, Mo2 to less than 17% by weight, W2
~10% by weight, Fe2~10% by weight, Co1~5% by weight
It has been found that an alloy consisting of the following exhibits good corrosion resistance and durability. Cr is an element that forms a stable passive film even in acetic acid gas and improves corrosion resistance, but this effect is not observed when the amount of polymerization is less than 2%. Moreover, if it exceeds 50% by weight, processability will be impaired.

Mo has no effect on corrosion resistance when it is less than 1%. Moreover, even if it is added in an amount of 17% by weight or more, no effect of improving corrosion resistance is observed, and workability and mechanical properties are impaired.

F e s W % Cu SC, o is an element that forms a stable passive film in a highly oxidizing environment or an element that increases corrosion reaction resistance, but this effect is not seen when less than 1% by weight is added. . Further, even if added in large amounts, no effect of improving corrosion resistance is observed, and workability and mechanical properties are impaired.

In addition to the above-mentioned amounts of limiting ingredients, the alloy of the present invention contains small amounts of Mn5V, S, which are unavoidably mixed from the main raw material, auxiliary raw materials, etc., or added for other purposes.
There is no problem even if iSC, S, P, etc. are contained, and even if these elements are added, the corrosion resistance in an environment where acetic anhydride and acetic acid are present at the target high temperature of 300 ° C. or higher will not be reduced. By using this alloy, local corrosion does not occur even in the presence of acetic anhydride, acetic acid, or even in the presence of the reaction product liquid.
Shows good corrosion resistance and durability.

[Operation] The corrosion resistance of the alloy according to the present invention in the specific corrosive environment of equipment handling co-acetic acid and acetic anhydride at high temperatures is unique and could not be expected from knowledge regarding conventional corrosion-resistant materials.

In other words, the inventors of the present invention conducted extensive studies on many materials in order to find metal materials that meet the purpose of the present invention, and found that most of the materials had pitting or localized corrosion on their surfaces and were unusable. In contrast, the alloy according to the present invention was found to exhibit excellent corrosion resistance, with a small amount of corrosion, no local corrosion, and no contamination of the product itself.

[Examples] Hereinafter, the present invention will be explained in more detail with examples.
The present invention is not limited to these.

(Example 1) Samples for immersion tests (30X40X4tmm
), which was attached to a reaction vessel and subjected to an immersion corrosion test. The environment of the reactor was 300° C., a gas phase of acetic acid and acetic anhydride, and a liquid phase of acetic acid and acetic anhydride. After being immersed in this environment for 3 days, it was taken out from the system and its surface condition was observed.

The results are shown in Tables 2 and 3. As is clear from Tables 2 and 3, in samples No. 1, No. 2, and No. 3, which are equipment materials having the composition of the present invention, only extremely slight general corrosion was observed, and good corrosion resistance and durability were observed. showed that.

However, comparative materials No. 4 and No. 5 (SUS316L)
, No. 6 (Cr) showed local corrosion and could not be used as equipment materials.

Table 2 (gas phase part) Table 1 Table 3 (liquid phase part) (Example 2) In an aromatic polyester polymer manufacturing apparatus, the alloy according to the present invention, that is, sample No. 1 listed in Example 1, was placed in an ION reactor. , No. 2, No. 3, No. 4, No. 5, and No. 6 alloy test pieces were attached.

In this reaction vessel, 3.73 kg of p-hydroxybenzoic acid, 1.20 kg of terephthalic acid, 0.3 kg of isophthalic acid, 4
, 1.67 kg of 4°-hydroxydiphenyl and 5.051 cg of acetic anhydride were added, and after N2 substitution, 150
The mixture was refluxed at ℃ for 2 hours, and acetic acid was distilled off while raising the temperature. Once the temperature reached 350°C, it was held for 1 hour. after that,
The reactant was pulverized while being cooled and solidified to obtain a polymer. After repeating the polymerization described above 10 times, a metal test piece was taken out from the system and its surface condition was observed. The results are shown in Table 4. As is clear from Table 4, samples No. 1, No. 2, and No. 2 are materials having the composition of the present invention.
In No. 3, only extremely slight corrosion was observed on the entire surface, indicating good corrosion resistance and durability. However, comparative material No. 4
, No. 5, and No. 6 showed local corrosion and could not be used as equipment materials.

Table 4 [Effects of the Invention] According to the present invention as is clear from the above explanation, 300°C
Even in an environment where acetic acid and acetic anhydride are present at higher temperatures, it is possible to provide a component that does not cause any local corrosion, has improved corrosion resistance and durability, and does not cause problems with contamination of the product itself. Its industrial value is high.

Claims (1)

[Claims] (1) Consisting of Cr, Mo, one or more elements selected from the group of Fe, W, Cu, and Co, and the remainder being substantially Ni, and the Cr is 2 to 50% by weight %, consisting of an alloy having a composition of 1 to less than 17% by weight of Mo and 1 to 30% by weight of an element selected from the above group, 300
Parts for equipment handling acetic acid and acetic anhydride used at high temperatures above ℃.