CONVERSION OF GAS TO TRANSPORTATION FUELS

Abstract

There is a widespread interest in the utilisation of the world's gas reserves, a considerable volume of which are located in remote areas and cannot be transported economically by pipeline. In addition the traditional market for such gas has been liquefied natural gas, but currently the market appears to be saturated. Consequently Bechtel Petroleum Inc. made a technical and economic analysis of processes which could be used to convert natural gas to transportation fuels. It was found that there is a number of new technologies which could be considered commercial and a considerable number that look promising but are not yet commercial.

This paper presents the results of the economic analysis of the following five commercial or near commercial processes.

Natural gas to methanol,Natural gas to methanol and gasoline,Natural gas to gasoline and diesel via the Fischer Tropsch process,Natural gas to gasoline and distillate (via extracted liquified petroleum gas), andOlefins direct to gasoline and distillate.

For comparison purposes the economics of liquified natural gas were also developed.

This comparison indicated that the conversion of olefins to transport fuels has a distinct economic advantage over the others. In addition this process has the flexibility of yielding varying percentages of gasoline and diesel according to market demand whereas some of the processes can produce only a single product. One disadvantage is that the olefins feedstock must be priced on a heating value basis comparable to natural gas and not for its alternative value in the manufacture of petrochemicals. There are situations in the world where refinery and chemical offgases containing olefins in dilute form could be priced competitively with natural gas.

The conversion of extracted liquified petroleum gas from natural gas also looks promising, but it must be priced competitively with natural gas.

The economic comparison highlighted the need for future basic research into the conversion of natural gas directly to transportation fuels rather than going through intermediate steps. Considerable research is currently being directed to these conversion processes. In addition there is also research being conducted to improve the economics of the commercial Fischer Tropsch conversion process.