Naphtha reforming process

摘要

A gas stream of H2, N2, H2O, CO and CO2 is made by forming a stream at at least 1000 DEG F. by mixing hot naphtha vapour at up to 1000 DEG F., superheated steam, and hot air, allowing the mixture to react for less than 1.0 sec., then contacting the mixture with a reforming catalyst at at least 1400 DEG F. The naphtha consists mainly of straight-chain C5- 9 paraffins; up to 30% naphthenes and up to 10% aromatics and unsaturated hydrocarbons may be present, with some COS and mercaptans. The product stream is free from hydrocarbons, and free carbon deposits do not accumulate. In the Figure, liquid naphtha 1 is vaporized and preheated in heater 2; the naphtha vapour stream 3 may be at 400-800 DEG F. Steam stream 4 which may be at 1500-1700 DEG F. and air stream 5 at 800-1200 DEG F. may be mixed forming stream 6 at at least 1100 DEG F., which is then mixed with stream 3 to form mixed stream 7, at 1000-1700 DEG F., which is then passed into chamber 8, which may be an insulated pipe, or streams 3, 4 and 5 may be separately passed to chamber 8, where reactions take place, and the temperature of the stream rises, e.g. to 1450-1500 DEG F. or above 1600 DEG F. The range of ratios of steam molecules: carbon atoms is 3: 1 to 7: 1. The proportion of air may be that required to produce a H2: N2 molar ratio of 3: 1 in the product. The residence time in 8 is preferably 0.05-0.33 sec., after which the gas stream 9 enters catalytic reformer 10, provided with more than one reformer tube 11 containing reforming catalyst 12, e.g. Ni or Co on a carrier, with or without inert diluent, e.g. porcelain, in the upper part. Preferably stream 9 is divided into a plurality of partial streams which are passed into contact with the catalyst at a plurality of spaced intervals. Tube 11 is heated externally, e.g. by burning fluid hydrocarbon streams 13 with air streams 14, the gases leaving at 15. Temperatures may be not less than 1400 DEG F. where free oxygen is present, and not less than 1600 DEG F. otherwise. The "equivalent velocity" of the stream in 11, i.e. the velocity the stream would have were catalyst 12 absent, is at least 5ft./sec.,preferably 10-30ft./sec. Operating pressure may be 100-300 p.s.i.g. The resulting product stream leaves via 16, containing, by volume, about 50% steam, and on a dry basis 51.4% H2, 22.5% N2, 13.0% CO2, 12.1% CO, 1% CH4 and 0.0% unsaturated hydrocarbons. From this a 3: 1 H2 : N2 gas mixture may be obtained by known means. U.S.A. Specifications 2,660,519 and 2,801,159 are referred to.