Haldor Topsoe A/s

Allan Skov

Jens R Rostrup-Nielsen

Synthetic hydrocarbons, especially high octane gasoline, are prepared by catalytic conversion in two steps of a synthetic gas containing hydrogen and carbon oxides. In the first step the synthesis gas is converted at 10-80 bar and 200.degree.-300.degree. C. into an intermediate containing methanol and/or dimethyl ether. Useful catalysts for methanol synthesis are oxides of chromium, aluminium and/or copper, and zinc; and for dimethyl ether synthesis certain zeolites. In the second step the entire intermediate from the first step is converted at the same pressure as in the first step and an inlet temperature of 300.degree.-340.degree. C. while supplying heat to obtain an outlet temperature of 410.degree.-440.degree. C.; the difference between inlet and outlet temperature being at least 30.degree. C. higher than the temperature increase caused by the conversion reaction. As catalyst in the second step one can use any conventional catalyst for converting methanol and/or dimethyl ether into hydrocarbons, especially synthetic zeolites. The raw product stream from the second step is cooled and thereby separated into a condensed hydrocarbon product stream and a gaseous recycle stream, the latter being recycled without further separation to the inlet of the first stream and here combined with fresh synthesis gas feed. There is obtained a low rate of deactivation of the catalyst used in the second step and a high quality hydrocarbon product.

Process for the preparation of synthetic hydrocarbons

The invention relates to an improved catalytic methanation process wherein a feed gas containing predominantly hydrogen and being rich in carbon oxides (CO and/or CO.sub.2) is divided into two part streams of which the first is methanated partially in an adiabatic methanation reactor by a methanation catalyst whereafter the effluent from the adiabatic methanation reactor is united after cooling with the second feed gas part stream and the thus-combined stream is methanated in a cooled methanation reactor by a methanation catalyst, preferably the same as that used in the adiabatic methanation reactor. It is possible, but not always necessary, to recycle part of the recycle gas to the adiabatic methanation reactor to keep the temperature therein at a moderate level. The process is useful in connection with transport of energy from a nuclear reactor. It is advantageous because it can be operated to produce superheated steam, for use, e.g. for producing electricity, in connection with the cooling of the effluent from the adiabatic reactor, whereby energy losses can be reduced to a very low level; and because the amount of recycle gas is reduced, possibly to nil, whereby energy is saved.

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Lyngby, Denmark

Allan Skov