Chemistry: fischer-tropsch processes; or purification or recover – Group viii metal containing catalyst utilized for the...
Reexamination Certificate
1999-12-02
2002-01-29
Padmanabhan, Sreeni (Department: 1621)
Chemistry: fischer-tropsch processes; or purification or recover
Group viii metal containing catalyst utilized for the...
C518S700000
Reexamination Certificate
active
06342538
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a catalyst for hydrogenation of carbon monoxide and/or carbon dioxide and also to a method for the synthesis of methanol from carbon monoxide and/or carbon dioxide using the hydrogenating catalyst.
Synthesis of methanol from synthetic gas was industrialized in 1923 in Germany by means of a gas phase reaction process using a zinc-chromium catalyst under the reaction condition of 200 atmospheres and 400° C. In 1959, a copper-zinc catalyst (CuO—ZnO) was developed in England and, in 1966, synthesis of methanol under the condition of reaction pressure of 50 atmospheres was industrialized.
After that, improvements in the copper-zinc catalyst and the reaction process have made a progress and, at present, operation is carried out under the reaction condition of 50-100 atmospheres and not higher than 300° C. Particularly for increasing the methanol concentration at the outlet of the reaction and for making the costs for equipment and operation advantageous, reaction pressure of 80-100 atmospheres is most preferred. However, in order to keep such a high reaction pressure, motive power for increasing the pressure is necessary and there is a problem that the cost therefor is high.
Therefore, in reducing the operation cost, the reaction is to be carried out at lower pressure but, in case the reaction pressure is 20 atmospheres for example, when an operation is carried out using a starting gas consisting of 33% by volume of carbon monoxide and 67% by volume of hydrogen, the equilibrium conversion rate of methanol is only 21% at the reaction temperature of 250° C. and that is not practical while, at the reaction temperature of 200° C., the equilibrium conversion rate is 60% but, since the catalytic activity is not sufficient, quite a large amount of catalyst is necessary and that is not practical as well. Accordingly, in the prior art, it has not been possible to make the reaction pressure lower than 50 atmospheres.
With regard to a catalyst other than the copper-zinc catalyst for the synthesis of methanol, it has been reported that a palladium catalyst prepared by means of an impregnation method using a rare earth metal oxide as a carrier is active for the synthesis of methanol (
Journal of the Chemical Society, Chemical Communications,
1982, no. 12, page 645). However it has a disadvantage that the reactivity is low and, in addition, it exhibits a low selectivity of methanol because methane is by-produced.
As such, the catalysts for the synthesis of methanol up to now have no sufficient reactivity at the reaction temperature of around 200° C. and, therefore, they are unable to lower the reaction pressure.
SUMMARY OF THE INVENTION
An object of the present invention is to offer a catalyst for hydrogenation of carbon monoxide and/or carbon dioxide having a high activity (especially the activity at low temperature) and particularly having a selectivity to methanol or, in other words, to offer a catalyst for the synthesis of methanol and also to offer a method for the synthesis of methanol having a high reaction efficiency.
The present inventors have carried out various experiments and studies for such an object and have found that, in a catalyst where palladium is carried on a metal oxide type carrier including cerium type oxide, dispersibility (particle size) of palladium affects the activity at low temperature and selectivity as the catalyst for hydrogenation and, when a catalyst having a high dispersibility of palladium is used for hydrogenation of carbon monoxide and/or carbon dioxide, high activity at low temperature and selectivity to methanol are achieved and that a catalyst having a high dispersibility of palladium can be prepared by a specific method, whereupon the present invention has been accomplished.
The present invention offers a catalyst for hydrogenation of carbon monoxide and/or carbon dioxide, a catalyst for the synthesis of methanol, a method for the synthesis of methanol and, a method for the hydrogenation of carbon monoxide and/or carbon dioxide which will be mentioned as follows.
The catalyst for hydrogenation of carbon monoxide and/or carbon dioxide according to the present invention is that where palladium having a particle size of 5 nm or less is carried on a metal oxide type carrier containing cerium type oxide.
The above catalyst for hydrogenation can be prepared as a coprecipitate of a precursor of a metal oxide type carrier containing cerium oxide type oxide (such as a hydroxide containing cerium) with palladium.
The catalyst for hydrogenation can also be prepared by mixing a solution where a metal oxide type carrier containing cerium oxide type oxide is dispersed with a solution of palladium compound and an alkaline solution whereby palladium is separated as a hydroxide. Further, the said catalyst for hydrogenation may be in such a form that, if necessary, the palladium hydroxide is converted to an oxide by heating the said catalyst or that, if furthermore necessary, a reduction treatment is carried out whereby the palladium oxide is converted to palladium metal.
The above-mentioned catalyst for hydrogenation can be used as a catalyst for the synthesis of methanol from carbon monoxide and/or carbon dioxide.
The method for the synthesis of methanol according to the present invention is that carbon monoxide and/or carbon dioxide are/is made to react with hydrogen in the presence of any of the above-mentioned catalysts for hydrogenation.
It is preferred that, usually, the above reaction is carried out in a gas phase preferably under 10-100 atmospheres and preferably at 150-300° C.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Catalyst for Hydrogenation (Catalyst for Synthesis of Methanol)
The catalyst for hydrogenation according to the present invention is a catalyst (Pd/CeO
2
type catalyst) where palladium is carried on a metal oxide type carrier containing cerium type oxide and can be used as a catalyst for the hydrogenation of carbon monoxide and/or carbon dioxide and also as a catalyst for the synthesis of methanol.
The metal oxide type carrier includes cerium type oxide, a mixture of two or more cerium type oxides, and a mixture of one or more cerium type oxide(s) and one or more metal oxide(s) other than the cerium type oxide.
The cerium type oxide includes cerium oxide (CeO
2
) and compounded oxides of cerium and of one or more metal(s) other than cerium. The metal oxide other than cerium type oxide includes an oxide of metal other than cerium and compounded oxides of two or more metals other than cerium.
Examples of the metal other than cerium are titanium, zirconium and iron. Examples of the metal oxide other than the cerium type oxide are TiO
2
, ZrO
2
and Fe
2
O
3
.
In preferred embodiments, 70% by weight or more, particularly 80% by weight or more, or still particularly 90% by weight or more cerium type oxide is included and, as a cerium type oxide, a metal oxide type carrier containing 70% by weight or more, particularly 80% by weight or more, or still particularly 90% by weight or more cerium oxide (CeO
2
) is used.
The catalyst for hydrogenation according to the present invention includes a catalyst where palladium is carried as palladium metal and a catalyst where palladium is carried as a palladium compound such as oxide or hydroxide. In a catalyst where palladium is carried as a palladium compound, activity as a catalyst for hydrogenation can be improved by converting the palladium compound into palladium metal. For example, when palladium hydroxide is heated at high temperature (such as 300-600° C.), it can be converted to palladium oxide and the palladium oxide can be converted to palladium metal by means of reduction (such as reduction with hydrogen).
The carrying amount of palladium in the catalyst for hydrogenation according to the present invention in terms of Pd to the sum of palladium and the metal oxide type carrier is that examples of the lower limit are 1% by weight or more, preferably 2% by weight or more, more preferably 5% by weight or more and, particularly preferab
Matsumura Yasuyuki
Shen Wen-Jie
Agency of Industrial Science & Technology
Padmanabhan Sreeni
Parsa J.
Rader & Fishman & Grauer, PLLC
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