Catalyst – solid sorbent – or support therefor: product or process – Catalyst or precursor therefor – Metal – metal oxide or metal hydroxide
Reexamination Certificate
1999-11-12
2004-02-10
Griffin, Steven P. (Department: 1759)
Catalyst, solid sorbent, or support therefor: product or process
Catalyst or precursor therefor
Metal, metal oxide or metal hydroxide
Reexamination Certificate
active
06689713
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a copper-containing catalyst, a process for the preparation thereof and uses of the same.
BACKGROUND OF THE INVENTION
Copper-containing catalysts, for example, catalysts containing copper and zinc oxide or catalysts containing copper, zinc oxide and alumina, have been used widely in industries as conventional catalysts in many processes such as low temperature transformation, methanol synthesis, hydro/dehydrogenation processes and so on.
Copper-containing catalysts are generally prepared by a coprecipitation method, that is, by adding a basic coprecipitant, for example, an alkali metal salt such as sodium carbonate, sodium bicarbonate and ammonium carbonate, to a mixed solution of a soluble copper salt, zinc salt and aluminum salt to precipitate out copper, zinc and aluminum as insoluble subcarbonates, which is then filtered, washed, dried, calcined, and pressed and moulded into a catalyst. EP 125,689 discloses a process for preparing a copper-containing catalyst used in methanol synthesis process, wherein the catalyst has an atomic ratio of copper to zinc of 2.8-3.8 (corresponding to 26.9-36.5 parts of zinc oxide per 100 parts of copper oxide), and the parts of alumina is 8-12. In the preparation process, copper and zinc are introduced into the catalyst by a coprecipitation method by adding such a precipitant as sodium carbonate to a solution of the metal salts, and alumina is introduced in the form of aluminum hydroxide sol into the catalyst. U.S. Pat. No. 4,876,402 discloses a process for preparing a catalyst containing copper and zinc oxide for the hydrogenation of aldehydes in gas phase by using sodium carbonate as coprecipitant. In the preparation process of the catalyst the resultant precipitate needs to be pulped, washed and filtered for 4 times in order to remove the sodium salt from the coprecipitate. Nevertherness, as admitted in the prior arts including U.S. Pat. No. 3,303,001 have recognized, copper oxide/zinc oxide catalysts prepared by the standard coprecipitation technique of the prior art will still contain a small amount of sodium. However, the presence of sodium in the catalysts is undesirable because alkali metals, in particular sodium, will diminish the activity of the catalysts. In addition, in the prior arts, copper-containing catalysts are prepared by a coprecipitation method with a basic substance, especially, sodium carbonate, as coprecipitant. Such a preparation process is carried out under a basic condition and zinc compound was precipitates first followed by copper compound, thus it is liable to form inhomogeneous coprecipitates, resulting in non-uniform catalyst crystallite sizes (1.0-10 nm) in irregular crystal shapes, of which the larger crystallites are 10 times the size of the smaller. In order to obtain catalysts of excellent activity and stability, the crystallites of copper oxide should be evenly separated by zinc oxide, but this cannot be achieved by the sodium carbonate method of the prior art. Another disadvantage of using sodium carbonate as coprecipitant is that, since the resulting coprecipitate shall be pulped, washed and filtered repeatedly to remove the undesired sodium salt, it consumes large amounts of pure water and as a result, a large quantity of waste water is discharged and needs to be treated or otherwise will pollute the environment, so the complexity of preparation and the production costs of the catalyst are further increased. The last point, but not least in importance, to be mentioned is that, the specific surface area of the catalysts prepared according to the prior art process is not large enough, and the pore volume and bulk specific weight are all relatively low, so, with respect to the catalytic performance, the catalysts exhibit unsatisfactory activity and selectivity and poor stability.
Therefore, there is a need in the art to develop a copper-containing catalyst having uniform crystallite distribution, large specific surface area and pore volume and, high activity and good stability, and a process for the preparation thereof.
After extensive studies and experiments, the inventors have discovered a novel process comprising a coprecipitation method for the preparation of a copper-containing catalyst featuring a uniform crystallite distribution and showing excellent catalytic performances.
SUMMARY OF THE INVENTION
An object of the invention is to provide a copper-containing catalyst featuring a uniform crystallite distribution and showing excellent catalytic performances.
Another object of the invention is to provide a process for preparing a copper-containing catalyst by a coprecipitation method, comprising the step of mixing a working solution containing soluble metal salts for coprecipitation and a solution containing organic acid(s) and/or ammonium salt(s) thereof as coprecipitant to coprecipitate out a mixture of insoluble metal salts containing copper. Said process has overcome the problems of environmental protection existing in the prior art, while the costs for production and starting materials are reduced.
A further object of the invention is to provide a use of the copper-containing catalyst according to the present invention in various chemical processes in which the catalytic action of a copper-containing catalyst is needed, including hydrogenation of aldehydes and/or ketones in gas phase, dehydrogenation of alcohols in gas phase, and a process of methanol synthesis from a mixed gas of CO, CO
2
and H
2
.
These and other objects of the invention will become apparent to the person skilled in the art after reading the specification.
DETAILED DESCRIPTION OF THE INVENTION
The copper-containing catalyst of the present invention is prepared by a novel process comprising a coprecipitation method and has a uniform crystallite distribution wherein the crystallites having a diameter of less than 1.0 nm account for 0-20%, preferably 0-15%, more preferably 0-10% and most preferably 2-5%; those of 1.0-2.0 nm account for 70-99%, preferably 75-98%, more preferably 80-95% and most preferably 85-90%; and those of more than 2.0 nm account for 0-20%, preferably 0-15%, more preferably 0-10% and most preferably 2-5%.
The copper-containing catalyst of the present invention comprises copper oxide of 30-70 wt %, preferably 33-50 wt %; zinc oxide of 30-70 wt %, preferably 50-65 wt %; and alumina of 0-30 wt %, preferably 10-25 wt % based on the weight of the catalyst.
The copper-containing catalyst of the present invention has a specific surface area of 30-50 m
2
/g, preferably 35-45 m
2
/g; a pore volume of 0.10-0.25 ml/g, preferably 0.15-0.20 ml/g; and an average pore diameter of 15-20 nm.
Since sodium salt is not used as a precipitant in the preparation process, sodium can be avoided being introduced into the catalyst. The copper-containing catalyst of the present invention preferably contains no sodium.
The process for preparing the catalyst according to the present invention comprises the steps of:
mixing a working solution containing soluble metal salts for coprecipitation and a solution containing organic acid(s) and/or ammonium salt(s) thereof as coprecipitant to coprecipitate out a mixture of insoluble metal salts; aging and filtering the mixture to obtain a filter cake, drying and calcining to form mixed oxides of catalyst, and then pressing and moulding the mixture to obtain the catalyst which can be in any suitable shape, such as tablet, cylindrical, bar, spherical and the like.
Said soluble metal salts are copper salt(s) and the salt(s) of other metal(s) used as essential metal components of the catalyst, which can be, for example, either copper salt(s), zinc salt(s) and aluminum salt(s), or copper salt(s) and zinc salt(s), selected from the group consisting of chlorides, sulfates, nitrates and acetates. Said organic acid(s) as coprecipitant can be one or more soluble organic acid(s) and may be selected from the group consisting of oxalic acid, malonic acid, succinic acid, and glutaric acid and ammonium salts thereof, preferably malonic acid, oxalic acid and
Chen Yuzhuo
Wang Yuliang
Zhang Lijuan
Zhao Leiping
Anderson Kill & Olick P.C.
China Petro-chemical Corporation
Griffin Steven P.
Johnson Edward M.
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