(181c) Conversion of Synthesis Gas to Gasoline

High and sustaining oil and energy prices have spurred a renewed interest in manufacture of synthetic fuels and chemicals from gas, coal and other sources. The TIGAS (Topsoe Integrated Gasoline Synthesis) process for the conversion of synthesis gas into gasoline was developed and demonstrated on a T/d scale in the mid-eighties using natural gas as feedstock. A subsequent demonstration program based on coal gasification was initiated, but later abandoned due to plummeting oil prices and lack of interest in the market. Today, we are back to the situation where alternative sources for production of liquid fuels and increasing the degree of self-supply is high in demand. The basic principle in the TIGAS process is that of integrating a methanol/dimethyl ether synthesis and the subsequent conversion into gasoline in a single synthesis loop, i.e., without the isolation of intermediate MeOH or DME. Due to the flexibility of the MeOH/DME synthesis a variety of synthesis gas compositions may be applied. For CO-rich gases as obtained by gasification of coal, coke or biomass the integrated process offers a particular advantage due to the high efficiency that may be obtained in the synthesis of the MeOH/DME intermediate at the low (< 1) H2/CO ratios characteristic to gasification. As opposed to methanol synthesis, where a module ? the effective H2/CO ratio ? adjustment to 2 is required, the ideal stoichiometry with respect to the combined MeOH/DME synthesis is at H2/CO = 1, making DME by far the dominant intermediate. In addition to improving the conversion efficiency less steam is required for module adjustment. Finally, CO2 removal as well as module adjustment may be carried out inside the synthesis loop, minimizing the recycle of unconverted synthesis gas. The virtues of the integrated process and recent developments will be highlighted.