Catalyst – solid sorbent – or support therefor: product or process – Catalyst or precursor therefor – Metal – metal oxide or metal hydroxide
Reexamination Certificate
1999-08-16
2001-10-16
Bell, Mark L. (Department: 1755)
Catalyst, solid sorbent, or support therefor: product or process
Catalyst or precursor therefor
Metal, metal oxide or metal hydroxide
C502S328000, C502S330000, C502S331000, C502S332000, C502S333000, C502S339000, C502S340000, C502S344000, C502S345000, C502S178000, C502S183000, C502S184000, C502S185000, C502S243000, C502S244000, C502S245000, C502S251000, C502S252000, C502S253000, C502S255000, C502S262000, C560S243000, C560S245000
Reexamination Certificate
active
06303536
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a preparation process of a catalyst comprising noble metals as main component and other metals as catalysis promoter in combination with an alkali or alkaline earth metal compound, supported on the outer surface of a carrier, and also relates to use of a catalyst prepared according to the process of the present invention, for producing alkenyl acetates through reaction of olefins, acetic acid and oxygen in vapor phase.
BACKGROUND OF THE INVENTION
The industrial production of alkenyl acetates through reaction of olefins, oxygen and acetic acid in vapor phase has been performed in the presence of a heterogeneous catalyst, which comprises noble metals, metals as catalysis promoter in combination with an alkali or alkaline earth metal compound supported on the outer surface of a carrier. This preparation process has been known for a long time and the key point of this process, the evenly distribution of metal components on the surface of a supporting catalyst to provide high yield, also has been widely discussed and studied, mostly based on changing the kind or relative composition of the metal components. However, no matter how the metal composition or its structure has changed, the basic structure of all catalysts for producing alkenyl acetates is essentially a spherical shape catalyst prepared by impregnating on a carrier with the palladium metal, a metal for promoting catalysis, and an alkali or alkaline earth metal compound, wherein the metal for promoting catalysis is preferably gold and copper, and wherein the alkali or alkaline earth metal compound is preferably a potassium compound (U.S. Pat. No. 3,939,199, EP 0361484 and U.S. Pat. No. 4,668,819).
Earlier, the catalyst employed to produce vinyl acetate was prepared by impregnating palladium, gold and the like noble metals on the whole carrier (U.S. Pat. Nos. 3,725,680, 3,743,607); the catalyst employed to produce allyl acetate was prepared by impregnating palladium, copper and the like noble metals on the whole carrier (U.S. Pat. No. 3,917,676). That is, the active noble metals were supported on the interiors and outer surface of a carrier. However, while the catalyst was prepared in this way, it was found in actual reaction that the reactants were scarcely able to efficiently diffuse into inner regions of the carrier, so that the interior active palladium and gold or copper metals were not able to be sufficiently utilized. In order to improve this drawback, in the preparation process of the catalyst for producing alkenyl acetates, usually, instead of impregnating palladium metal and a metal for promoting catalysis on the whole carrier, but to evenly impregnate on the surface of a carrier. That is, to impregnate palladium metal and the metal for promoting catalysis evenly on the surface layer of a carrier to form a spherical shape supported catalyst (U.S. Pat. No. 4,087,622). The preparation method was that the carrier was impregnated with the active metallic materials first, then these metal salts were precipitated by immersing in a solution containing an alkali or alkaline earth metal salts (U.S. Pat. No. 4,048,096, U.S. Pat. No. 3,775,342).
Further, it was known that when preparing the catalyst with palladium and other metals as catalyst promoter in combination with an alkali or alkaline earth metal compound, a special carrier was used. This carrier was washed with acids before the impregnation and treated with bases after the impregnation (EP-A-0519435).
Since palladium and the metal for promoting catalysis were non-homogeneous during the impregnation, which would result in the non-homogenous distribution on the surface of a carrier, therefore, many researches have been made on this problem (U.S. Pat. No. 4,087,622, U.S. Pat. No. 3,822,308 and British Patent 1521652). As a result, in the preparation of the catalyst for producing alkenyl acetates, the catalyst was essentially prepared by impregnating palladium and a metal for promoting catalysis, in combination with an alkali or alkaline earth metal compound on the surface of a spherical shape carrier. The preparation process generally was comprised of the following steps: (1) a carrier was impregnated with an aqueous solution of soluble palladium ions and metal ions for promoting catalysis; (2) the impregnated carrier was immersed in an alkali solution, so that the soluble palladium ions and metal ions for promoting catalysis were precipitated on the surface layer of the carrier and formed into insoluble oxidative state palladium and metal for promoting catalysis; (3) the treated carrier was washed with water to remove soluble ions produced during the precipitation; (4) the oxidative state palladium and metal for promoting catalysis supported on the treated carrier were then reduced to the metallic state; (5) the reduced carrier in (4) was impregnated with a solution of an alkali or alkaline earth metal compound; and (6) the impregnated carrier in (5) was dried. Among these steps, conventionally, the reducing step (4) was performed by a reducing process using liquid reducing agents in liquid phase. However, since non-homogenous nature of palladium and the metal as catalysis promoter on the surface of the carrier, the catalyst prepared by this method is usually unsatisfactory.
In order to resolve the above problem, in the preparation process of the catalyst for producing alkenyl acetates according to the present invention, the conventional reducing process utilizing liquid reducing agents in liquid phase is changed into a reducing process utilizing gaseous reducing agents in gaseous phase. As a result, the catalyst comprising palladium and a metal as catalysis promoter in combination with an alkali and alkaline earth metal compound supported on a carrier prepared by using this present invention has a high metal surface area and exhibits high catalytic activity, thus the catalytic efficiency and life of this heterogeneous catalyst are improved.
SUMMARY OF THE INVENTION
This invention relates to a preparation process of a catalyst which comprises a noble metal and a metal as catalysis promoter in combination with an alkali or alkaline earth metal compound, supported on the outer surface of a carrier. The preparation process comprises impregnating the carrier with a solution containing an oxidative state noble metal as the main catalyst and an oxidative state metal as catalysis promoter, reducing the oxidative state metals into the metallic state in gaseous phase with a gaseous reducing agent under certain temperature, pressure, moisture and gas concentration, then impregnating the reduced carrier with a solution of an alkali or alkaline earth metal compound. The metal components-supporting catalyst prepared by the process according to the present invention has a high surface area and exhibits high catalytic activity, which leads to increase the catalytic efficiency and life of this heterogeneous catalyst. The catalyst prepared in the present invention is suitable for producing alkenyl acetates through reaction of olefins, acetic acid and oxygen in vapor phase.
DETAILED DESCRIPTION OF THE INVENTION
This invention relates to a preparation process of a catalyst which comprises a noble metal as main component and other metals as catalysis promoter in combination with an alkali or alkaline earth metal compound, all of which are supported on the outer surface of a carrier. The examples of the suitable carrier are alumina, silica gel, silica, active carbon, silicon carbide, diatomaceous earth, pumice and the like, while among them silica is preferable. The example of the noble metal is palladium; the examples of the metal as catalysis promoter are gold, copper, molybdenum, cadmium and magnesium, while among them gold and copper are preferable. The examples of the alkali or alkaline earth metal compounds are the hydroxides, acetates, nitrates and bicarbonates of potassium, sodium, cesium, magnesium, barium and the like, while among them potassium salts are preferable, and potassium acetate is even more preferable.
The distinctive
Chen Shien-Chang
Jang Pi-Fwu
Jong Yuh-Lih
Lin Fu-Shen
Bell Mark L.
Dairen Chemical Coorporation
Hailey Patricia L.
Jenkens & Gilchrist
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