Organic compounds -- part of the class 532-570 series – Organic compounds – Carboxylic acids and salts thereof
Reexamination Certificate
2001-10-31
2002-12-24
Parsa, Jafar (Department: 1621)
Organic compounds -- part of the class 532-570 series
Organic compounds
Carboxylic acids and salts thereof
C562S534000, C562S531000
Reexamination Certificate
active
06498270
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a process of preparing a catalyst for use in production of methacrylic acid and the catalyst and also relates to a process of preparing methacrylic acid in the presence of the catalyst, more particularly, to the process of preparing the catalyst and the same which is suitable for preparing methacrylic acid by gas phase oxidation and/or oxidative dehydrogenation of at least one compound selected from the group consisting of methacrolein, isobutyraldehyde and isobutyric acid and the process for preparing methacrylic acid in the presence of the catalyst.
2. Description of the Prior Art
There have been many proposals concerning a catalyst for preparing methacrylic acid by gas phase oxidation of methacrolein, isobutyraldehyde and unsaturated aldehyde and a process thereof. For example, in the case of using methacrolein, there have been also many proposals about improving a catalyst such as heteropoly-acids. These proposals were divided into two categories. One is concerning a composition of a catalyst and the choice of the composition and another is concerning a regulation of catalyst properties and a process thereof with good reproducibility. According to the later, for example, it is described that the preferred specific surface area of a catalyst ranges from 0.01 to 5 m
2
/g and 0.01 to 50 m
2
/g in Japan Open-Laid No.49-116022 and Japan Open-Laid No.50-37710, respectively. In spite of these specification, this catalyst is not suitable for industrial use because of excessively high reaction temperature and low selectivity.
Many proposals concerning the control of pore structure of a catalyst have been one. For example, Japan Open-Laid No.51-136615 and Japan Open-Laid No.55-73347 propose a catalyst which is achieved by adding organic substances such as ultivalent alcohol and polyvinyl alcohol and then curing them. However, the organic substances, which is used as additive and has a high decomposition temperature, will bum by heat treatment and thereby cause sintering and reduction of a catalyst and a problem such as low reproducibility of a catalyst still remains. Japan Open-Laid No.4-367737 proposed a process, wherein an organic polymer such as polymethylmethacrylate and polystyrene, which decomposes into a monomer and vaporizes at a relatively low temperature, is added, this method is also insufficient in the reproducibility of a catalyst.
In addition, a molding process, where a dried powder containing catalytic composition with the particle size adjusted in the range of 1 to 250 &mgr;m is used as a raw material, was proposed for the preparation of a catalyst in Japan Open-Laid 8-10621. However this process is not insufficient for industrial use, since this process has a problem of low reproducibility and also needs a more complicated drying process.
A catalyst for industrial use is generally used as a molded article. A molded article is produced by the process such as press molding, extrusion molding, rolling molding, Marumerizer molding, fluidized granulation, centrifuge fluidized coating process and the like. However, it is very hard to mold without lowering performance of a catalyst, and performance of the obtained catalyst is usually insufficient in reproducibility. For example, examples using press molding process were disclosed in Japan Open-Laid No.63-315148, Japan Open-Laid No.8-10621, Japan Open-Laid No.10-258233 and Japan Patent Gazette No.3-58776. According to all examples of them, a process of a press molding was not investigated in detail and these disclosures were insufficient from the view point of the reproducibility.
SUMMARY OF THE INVENTION
An object of the invention is to provide a process of preparing a catalyst for use in production of methacrylic acid and the catalyst. Another object of the invention is to provide a process for preparing methacrylic acid in the presence of the catalyst. The present inventors found that the above mentioned object can be achieved by molding a raw material including a powder containing phosphorus and molybdenum at the specific range of pressure and have accomplished the invention.
In other words, this invention provides a process for preparing a catalyst and the same for use in production of methacrylic acid by gas phase oxidation and/or oxidative dehydrogenation of at least one compound selected from the group consisting of methacrolein, isobutyraldehyde and isobutyric acid. The process comprises:
molding a raw material including a powder containing phosphorus and molybdenum at the pressure of 50 kgf/cm
2
to 5000 kgf/cm
2
into an article; and
calcining the molded article to obtain a catalyst
The invention also provides a process for preparing methacrylic acid characterized by gas phase oxidation and/or oxidative dehydrogenation of at least one compound selected from the group consisting of methacrolein, isobutyraldehyde and isobutyric acid with molecular oxygen or a gas containing molecular oxygen in the presence of the catalyst produced by a method of the invention.
DESCRIPTION OF THE PREFERRED EMBODIMENT
The process for preparing the catalyst of the invention is characterized by molding a raw material including a powder containing phosphorus and molybdenum as an essential component at the pressure of 50 to 5000 kgf/cm
2
into an article and calcining the molded article to obtain a catalyst.
First, the raw material used for the invention will be described. The raw material includes a powder containing phosphorus and molybdenum(hereinafter referred as P/Mo containing powder).
The P/Mo containing powder may contain other elements, for example vanadium, copper, zinc, silver, arsenic, antimony, zirconium, cerium, alkali metal, alkaline earth metal and the like besides phosphorus and molybdenum.
Preferably, a weight of the P/Mo containing powder is reducible from 0 to 40%, preferably 2 to 35%, more preferably 4 to 30% by weight with respect to the weight of the P/Mo containing powder while the P/Mo containing powder is heated at 300° C. in the atmosphere or an inert gas. The weight of the P/Mo containing powder will be substantially constant after an elapse of 2 hours of heat treatment. The weight loss of the P/Mo containing powder can be determined at that time if a weight of the P/Mo containing powder will be substantially constant after an elapse of 30 mins. or an hour. When a weight of the P/Mo containing powder is reduced over 40% by weight with respect to the weight of the powder, the fluidity of the powder deteriorate because the powder becomes sticky.
Preferably the P/Mo containing powder substantially comprises of particles having a diameter of 150 to 1500 &mgr;m, preferably 250 to 1000 &mgr;m, more preferably 250 to 800 &mgr;m. In the case of particle size below 150 &mgr;m, the fluidity of the P/Mo containing powder and runnability of molding conducted by the following molding process deteriorate and the selectivity for COx of the resultant catalyst is liable to increase because a pore size of the molded article becomes smaller. On the other hand, in the case of particle size over 1500 &mgr;m of the P/Mo containing powder, the amount of the P/Mo containing powder sucked into the mortar of a molding apparatus is variable and it causes to vary the molding pressure. As a result, mechanical properties of the resultant molded article and performance of the catalyst therefrom are liable to be lower because a pore size of the molded article becomes larger.
The P/Mo containing powder is prepared by a conventional method for a catalyst known to those of ordinary skill in the art. For example, compounds which contain phosphorus and molybdenum respectively are dissolved and dispersed into the medium usually into water to obtain a solution or slurry (hereinafter referred to as suspension).
The suspension is condensed, dried and calcined where necessary to prepare a powder. The suspension can be prepared by a conventional method such as evaporating concentration process, oxide mixing process and coprecipitation process and the like known to those sk
Kase Yuichi
Kimura Naomasa
Onodera Hideo
Nippon Shokubai Co. , Ltd.
Parsa Jafar
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