Process for preparing hydrocarbons

Details Process for preparing hydrocarbons Process for preparing hydrocarbons

1998-01-26

1999-09-14

Caldarola, Glenn

Chemistry of hydrocarbon compounds

Saturated compound synthesis

From nonhydrocarbon feed

585638, 518700, 518717, 518719, 518721, 502330, 502336, C07C 100, C07C 2700, B01J 2338

Patent

active

059525401

DESCRIPTION:

BRIEF SUMMARY
BACKGROUND OF THE INVENTION

1. Field of the Invention
This invention relates to a process for preparing hydrocarbons, in particular, to a process for preparing hydrocarbons by hydrogenation of carbon dioxide over Fe-K/Al.sub.2 O.sub.3 catalyst, which is reduced under hydrogen atmosphere after activated in mixture of carbon dioxide and hydrogen.
2. Description of Related Art
Carbon dioxide is the so called `greenhouse gas`. Accumulation of carbon dioxide in the atmosphere caused by a huge amount of the fossil fuel consumption is now regarded as one of the major reasons for Global Warming.
To conserve the environment, it will be necessary to restrict the use of fossil fuel. However, it is expected that it will be necessary to use fuel and materials containing carbon atom continuously. A possible contribution to reducing carbon dioxide accumulation would be the chemical transformation of carbon dioxide into valuable compounds or fuel using suitable catalysts. This would provide a means of recycling carbon dioxide exhausted from combustion of fuel.
The material manufactured from the reduction of carbon dioxide should be consumed in a wide scope because carbon dioxide is exhauted in enormous volume. Therefore, the effective conversion of carbon dioxide to hydrocarbons would be regarded as one of the most promising routes for carbon dioxide fixation by catalytic process.
Processes for preparing hydrocarbons by hydrogenation of carbon monoxide have been studied widely and applied in commercial quantity. Catalysts and technology used for the hydrogenation of carbon monoxide also can be applied to hydrogenation of carbon dioxide. But chemical properties of carbon monoxide and carbon dioxide are quite different from each other, so the yield of hydrocarbons, especially hydrocarbons having 2 or more carbon atoms (hereinafter called "C.sub.2+ hydrocarbons") is extremely low.
It requires emergently new catalyst for preparing hydrocarbons in high yield without forming of by-product such as carbon monoxide.
There are two general methods for preparing C.sub.2+ hydrocarbons using carbon dioxide. The first method is comprised of two- step reactions, that is, conversion of carbon dioxide to methanol and continuous conversion of the methanol to hydrocarbons. The second method is reacting carbon dioxide with hydrogen to obtain hydrocarbons directly.
Conventional methods for preparing C.sub.2+ hydrocarbons using carbon dioxide according to the above first method are as follows.
Japanese patent application No. 89-190,638 discloses a method in which carbon dioxide is reduced at 300.degree. C., 10 atm over catalysts in a fixed bed reactor . The catalysts used in the above reduction are composed of CuO--ZnO--Al.sub.2 O.sub.3 and dealuminated H--Y Zeolite of SiO.sub.2 /Al.sub.2 O.sub.3 molar ratio .ltoreq.10. As the result of reduction, the yield of hydrocarbon was 9.7% and the conversion of carbon dioxide was 20.3%.
Japanese patent application No. 92-120,191 discloses a method in which preparing of methanol from carbon dioxide, and C.sub.2+ hydrocarbons from methanol are performed in two reactors. Carbon dioxide is converted to methanol in the first reactor, and a mixture containing methanol is converted to C.sub.2+ hydrocarbons in second reactor.
The above two reactions are performed under different reaction conditions such as catalyst, temperature, pressure, etc. due to the difference of their optimum conditions at each reaction. The first reaction is performed appropriately at 250.degree. C., 80 atm, 4700 h.sup.-1 of the space velocity over CuO--ZnO--Cr.sub.2 O.sub.3 --Al.sub.2 O.sub.3 catalyst. On the other hand the second reaction is performed appropriately at 300.degree. C. , 1 atm, 1680 h.sup.-1 of the space velocity. As the result of the first reaction, the conversion of hydrocarbon was 32.1%, the selectivities to methanol and carbon monoxide were 24.9% and 7.2% respectively. The mixture passed through the first reactor was introduced into the second reactor. In the second reactor the conversion of carbon dioxide to hydroca

REFERENCES:
patent: 3842113 (1974-10-01), Ichikawa et al.
patent: 5140049 (1992-08-01), Fiato et al.
Lee et al.; Hydrogenation of Carbon Dioxide on Unpromoted and Potassium-Promoted Iron Catalysts Bull. Chem. Soc. Jpn., vol. 62, No. 8, 1989, pp. 2756-2758.
Weatherbee et al.; "Hydrogenation of CO.sub.2 on Group VIII Metals--IV. Specific Activities and Selectivities of Silica-Supported Co, Fe, and Ru" Journal of Catalysis 87, 1984, pp. 352-362.
Dwyer et al.; "Hydrogenation of CO and CO.sub.2 over Iron Foils--Correlations of Rate, Product Distribution and Surface Compositions" Journal of Catalysis 52, 1978, pp. 291-301.

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