Organic compounds -- part of the class 532-570 series – Organic compounds – Carboxylic acids and salts thereof
Reexamination Certificate
2000-12-22
2002-05-07
Griffin, Steven P. (Department: 1754)
Organic compounds -- part of the class 532-570 series
Organic compounds
Carboxylic acids and salts thereof
C562S533000, C562S534000
Reexamination Certificate
active
06384275
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a catalyst for acrolein oxidation, more particularly, to production of the catalyst containing molybdenum, vanadium, and tungsten as essential components.
2. Description of the Related Technology
In producing of acrylic acid, oxidation reactions of acrolein with oxygen molecules in the presence of a catalyst have been widely used. The preparation of the catalyst has been researched to obtain a high yield of the acrylic acid, which are primarily directed to the components of the catalyst and the composition thereof. Also, some methods of producing a carrier-retained catalyst have been provided in the prior art.
Japanese Patent Application Laid-Open Nos. Showa 49-117419, Showa 58-166939, and Showa 64-63543, and European Patent Application Laid-Open No. 293,859/1988 disclose methods for producing a carrier-retained catalyst, in which aqueous solutions of metallic salts of catalyst components are mixed and coprecipitated to produce a suspension of a catalyst. An inert carrier, which has a small surface area and a large aperture ratio, such as round or cylindrical silicon carbide, silica, and silica-alumina, is added to the suspension, and water is evaporated by heating the suspension with agitation to produce a catalyst retained within the structure of the inert carrier.
Further, in U.S. Pat. Nos. 4,157,987, 4,259,211 and 4,892,856; and Korean Patent Application Laid-Open No. 7409/1993, a suspension of a catalyst is heated to evaporate water while being stirred. Anhydrous solid of the catalyst is obtained and is ground to powder, which is coated on an inert carrier, such as aldundum, by using a coater.
The inert carriers retain the catalyst in their structures and prevent the release of the catalyst at a time. Accordingly, occurrence of excessive oxidation reactions, which may be caused by supply of abundant catalyst, can be avoided. Also, the inert carrier functions as heat buffer by absorbing the heat generated during the oxidation reaction.
Korean Patent Application Laid-Open No. 7409/1993 and U.S. Pat. No. 4,892,856/1990 disclose that physical properties, such as non-surface area, pore volume, and pore diameter distribution, vary in the catalysts prepared even from the identical component metallic salts and composition thereof. The variance in the physical properties of catalysts results in the variance in the catalytic performance of catalysts, i.e., the acrolein turnover ratio and acrylic acid yield. This means the physical properties and accordingly the catalytic performance of the catalysts change, depending on the preparational manipulations as well as the conditions thereof, which also causes the lack of reproducibility in preparing the catalyst. In addition, these variances of the catalytic performance sometimes exceed those by the changes in the components and the composition of the catalyst.
However, there has not yet been a report, which satisfactorily addresses that the physical properties and accordingly catalytic performance of a catalyst change, depending on the process of producing the catalyst including the preparation of a suspension or powder therefrom.
Meantime, in the preparation of the aqueous solution of metallic salts, an excessive amount of water is required to dissolve some metallic salts having low solubility in water, such as ammonium metavanadate and ammonium paratungstate. The amount of water in the suspension of the catalyst is from about 5 to about 10 times by weight of the salts. The solubility improves when the temperature of water increases, but heating of the aqueous solution of the salts deteriorates the catalytic performance.
The water used to prepare the suspension has to be completely removed to form a powder catalyst. Accordingly, the amount of energy and time required to remove the water has a direct relation to the amount of water used. Further, in the case where an inert carrier is added to the suspension to produce a carrier-retained catalyst, additional time is required to remove the water within the carrier structure.
SUMMARY OF THE INVENTION
One aspect of the present application provides a method of producing an acrylic acid. The method comprises preparing a suspension of catalyst particles in a supporting liquid; breaking the catalyst particles into smaller pieces while suspended in the liquid; applying thus-formed smaller catalyst particles in suspension to a carrier; drying the carrier and the catalyst particles applied thereto, thereby forming a carrier-retained catalyst; and reacting acrolein with a gas containing oxygen in the presence of the carrier-retained catalyst. The catalyst comprises metallic components of molybdenum, tungsten and vanadium.
The preparation of the suspension advantageously comprises dissolving molybdate, vanadate and tungstate in water to obtain a first aqueous solution of the metallic salts; and adding to the first aqueous solution additional metallic salts comprising salts of metal A and metal. A is at least one element selected from the group consisting of iron, copper, bismuth, chromium, tin, antimony, nickel, cobalt, manganese, cerium and thallium, and B is at least one element selected from the group consisting of an alkali metal and an alkali earth metal.
The catalyst is represented by a following chemical formula: Mo
a
W
b
V
c
A
d
B
e
O
x
. Here a, b, c, d, e and x respectively indicate the atomic ratio for Mo, W, V, A, B and O. When a=10, then b=1.5 to 4, c=1 to 5, d=1 to 4, and e=0 to 2 and x is determined according to oxidation states of the other elements.
The carrier is at least one selected from the group consisting of aldundum, silicon carbide, silica, and silica-alumina. The application of the catalyst particles to the carrier and drying thereof comprises spraying the suspension of the catalyst particles to the carrier while heated air is supplied to dry and obtain a carrier-retained catalyst. The particles of the catalyst are broken by at least one selected from the group consisting of ball mill, attrition mill, dynamo mill, homogenizer, and supersonic homogenizer.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
The inventors of the present invention have discovered that properties of a catalyst suspended in the water solution change when the suspension of the catalyst is heated to a high temperature. In addition, the properties of the catalyst change when the catalyst suspension is heated for a long period of time. The property changes cause deterioration of the catalytic activity or performance later. This also leads to a reduction in the reproducibility of the catalyst, and the performance of the powder catalyst or the carrier-retained catalyst becomes hard to control.
However, as noted above in the background of the invention supra, to reduce the heat application to the catalyst suspension, it is required to minimize the amount of water needed to dissolve the metallic salts. In this regard, the inventors also have discovered that some metallic salts dissolve in water better when they dissolve in an aqueous solution mixture of other metallic salts than when they dissolve in water separately. Specifically, molybdate, vanadate and tungstate, which are essential to produce a highly active catalyst, dissolve in water and form a concentrated aqueous solution mixture with higher solubility than each of the separate aqueous solutions thereof.
In accordance with one aspect of the present invention, first metallic salt components of the catalyst, which have low water-solubility, are dissolved together in water to form an aqueous solution of the salts. Each metallic salt dissolves in the aqueous solution more than it dissolves in water alone. The remaining metallic salt components of the catalyst, which have high water-solubility, or the aqueous solution thereof are added to the aqueous solution prepared above to form a catalyst suspension. The amount of water required to prepare the suspension of the catalyst can be drastically reduced, which in turn reduces the time a
Byun Young-Chang
Kang Kyung-Hwa
Ko Dong-Hyun
Lee Won-Ho
Knobbe, Martens Olson, and Bear, LLP.
LG Chem Ltd.
Nguyen Cam N.
LandOfFree
Method of producing acrylic acid using a catalyst for... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method of producing acrylic acid using a catalyst for..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method of producing acrylic acid using a catalyst for... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2862039