THE SHELL MIDDLE DISTILLATE SYNTHESIS PROCESS (SMDS)

Since the early 1970s Shell's research has been involved in syngas chemistry with special focus on routes to convert (remote) natural gas into easily transportable liquid hydrocarbons. This has resulted in the development of the SMDS process. The world's first commercial SMDS plant is being constructed on a site adjoining the Bintulu LNG plant in Sarawak, Malaysia, and will come on stream in the last quarter of 1992. The heart of SMDS is an enhanced Fischer-Tropsch process. However, direct FT synthesis does not allow the selective production of materials of narrow carbon number range. To overcome this limitation the flexible two-stage concept of SMDS has been developed, which combines the chain-length-independent FT chain-growth reaction with a chain-length-dependent cracking process. Naphtha, kerosene and gas oil yield ratios can be varied from 15:25:60 to 25:50:25. Both the kerosene and gas oil show excellent combustion properties: the smoke point of the kerosene can be over 45 mm and the gas oil has a cetane number in excess of 70. Further attention is paid to the production of the synthesis gas because of its impact on overall process efficiency, to the selection of multitubular FT reactors, and to the environmental merits of the SMDS process and its clean, aromatics-free products. © 1991 J.C. Baltzer A.G., Scientific Publishing Company.