Catalyst – solid sorbent – or support therefor: product or process – Catalyst or precursor therefor – Metal – metal oxide or metal hydroxide
Reexamination Certificate
1998-09-23
2001-01-09
Dunn, Tom (Department: 1754)
Catalyst, solid sorbent, or support therefor: product or process
Catalyst or precursor therefor
Metal, metal oxide or metal hydroxide
C502S311000, C502S312000, C502S315000, C502S316000, C502S321000, C502S324000, C502S353000, C502S439000
Reexamination Certificate
active
06171998
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. 4,157,987/1976, 4,259,211/1981, and 4,892,856/1990; 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 alundrum, 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 acrolein 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 invention provides a method of preparing a suspension of a catalyst for a use in gas phase acrolein oxidation reaction. Metallic salt components of the catalyst comprising essentially of molybdate, vanadate and tungstate are dissolved in water to obtain a first aqueous solution of the metallic salts. An additional metallic salt component of the catalyst is added to the first aqueous solution of the salts to form a suspension of the catalyst. In the suspension, the total weight of water is about 0.8 to about 5 times of the total weight of the metallic salts in the catalyst.
This method of preparing suspension minimizes the amount of water required to dissolve the metallic salts, which reduces the amount of time and energy to be used in evaporating water from the suspension in the following step of obtaining catalyst. Additionally, in obtaining catalyst from the suspension prepared by this method, it is possible to avoid the deterioration of the catalytic performance since less heat is required to evaporate the water.
Another aspect of the present invention provides a catalyst produced from the suspension. The catalyst for a use in gas phase acrolein oxidation reaction is represented by a following chemical formula:
Mo
a
W
b
V
c
A
d
B
e
O
x
,
wherein, A is at least one element selected from the group consisting of iron, copper, bismuth, chromium, tin, antimony, nickel, cobalt, manganese, cerium and thallium; B is at least one element selected from the group consisting of an alkali metal and an alkali earth metal; 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.
Still another aspect of the present invention provides a method of producing a carrier-retained catalyst. Metallic salt components of the catalyst comprising essentially of molybdate, vanadate and tungstate are dissolved in water to obtain a first aqueous solution of the metallic salts. An additional metallic salt component of the catalyst is added to the first aqueous solution of the salts to form a suspension of the catalyst. In the suspension, the total weight of water is about 0.8 to about 5 times of the total weight of the metallic salts in the catalyst. Catalyst particles suspended in the water are split or ground into smaller particles to maintain homogeneous suspension. The suspension is sprayed to an inert carrier while applying heated air to remove water and obtain a carrier-retained catalyst.
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 th
Byun Young-Chang
Kang Kyung-Hwa
Ko Dong-Hyun
Lee Won-Ho
Dunn Tom
Knobbe Martens Olson & Bear LLP
LG Chemical Ltd.
Nguyen Cam N.
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