Patent GB-377716-A (GB)
Title: Improvements relating to the heat treatment of hydrocarbon gases
IPC: C07C2/00
Filed: 1931-01-26
Abstract: Residual gases containing olefines obtained in the thermal treatment of gases containing paraffins and olefines for the production of aromatic hydrocarbon liquids by passing the initial gases at temperatures within an approximate range of from 450-1250 DEG  C. and at high velocity through heated reaction tubes and subsequently through a vessel of large volume which may be lagged to prevent radiation of heat and in which the reactions are allowed to continue for an interval of time before being arrested by cooling, are used for the production of carbon black by heating to a high temperature in a retort, or by combustion with a restricted supply of air. Specification 309,455, [Class 90, Non-metallic elements], is referred to.ALSO:<PICT:0377716/IV/1> In the thermal treatment of gases containing paraffins and/or olefines for the production of aromatic hydrocarbon liquids by passing the gases through heated reaction tubes at high velocities, for example, velocities from 10-30 reciprocal minutes, the gases are maintained for an interval of time after their passage through the reaction tubes at temperatures favourable to the continuance of the reactions.  This may be effected by bringing the gases after passing through the reaction tubes into a vessel of relatively large volume, for example, 10 times that of the reaction tubes, either suitably lagged to prevent outward radiation of heat, or externally heated only to a degree necessary to maintain an effective reaction temperature.  In this vessel carbon may be deposited.  After leaving the large reaction vessel the gases may pass into a second vessel of large volume in which the reactions are arrested by sudden cooling, and in which carbon may also deposit. The temperature in the reaction tubes may range from 450-1250 DEG  C. or higher, the highest temperatures being employed for methane, and the lower for higher members of the paraffin series and for olefines. The temperatures used are in general higher than those indicated in Specification 309,455, [Class 2 (iii), Dyes &c.], as suitable for the corresponding treatments.  The process may be carried out by passing the gases in order through a preheater a, through reaction tubes b mounted in the same setting c, through a vessel d of relatively large volume lagged to prevent radiation of heat, and, if desired, through another large vessel (not shown) in which cooling takes place. Before or after the second large vessel, the gases may pass through a tar separator e.  The gas passes into the preheater a through a pipe f, from which a branch pipe f<1> supplies gas for the burners g which heat the reaction tubes, h being a fan through which combustion air is supplied to the burners.  The gases leaving the separator e pass through a pipe for further treatment in the manner described in Specification 309,455.  The reaction tubes b are preferably of heat-resisting metal which does not favour the deposition of carbon, for example, chrome steel, and should be of small diameter such as from 1 to 4 inches.  They may be arranged in series or in parallel or both, and may discharge into the same or separate reaction vessels. The reaction may be carried out under low or moderately increased pressure, for example, under a pressure of 30 lbs. per square inch, or higher in the case of gases containing olefines. Superheated steam or other inert diluents, such as part of the residual gas from the treatment, may be admixed with the gas before its passage through the reaction tubes as described in Specification 309,455, these additions favouring the production of aromatic bodies when treating paraffins under pressure.  Pyrometer contacts may be provided in the reaction tubes and elsewhere in the plant to ensure precision in temperature control.  When carbon monoxide and hydrogen are present in the residual gas, they may be used for the synthesis of oxygen derivatives of hydrocarbons such as alcohols, aldehydes, ketones, organic acids, &c., by enriching the residual gas to the required extent with carbon monoxide or hydrogen.  The olefines formed may be used for the production of alcohols or esters, and the liquid aromatics and higher olefines may be employed in making antidetonating motor spirit.  The residual gas may be used for the production of carbon black by heating it to a high temperature in a retort, or by combustion with a restricted supply of air.  The reaction and preheater tubes are so mounted in the setting as to be accessible for cleaning by suitable devices or by burning the carbon deposit in a current of air, or by periodically blowing first with steam alone, then with air alone, and finally with steam.  The temperatures to which the gas is heated in the preheater should be substantially below that at which the reactions proceed.  According to examples, (1) a stripped gas containing methane, ethane, propane, butane, and hydrogen sulphide is passed through the apparatus shown, leaving the preheater at a temperature of 660-690 DEG  C., the temperature of the reaction tubes being 1020-1030 DEG  C., and that of the gas leaving the reaction vessel d being 780-850 DEG  C.  A liquid essentially aromatic in character is obtained, together with a residual gas containing ethylene, propylene, butylenes, and butadiene and (2) a refinery gas containing hydrogen, paraffins up to pentane, and olefines up to the butylenes was similarly treated, the temperature of the gas in the reaction vessel not being allowed to fall below 700 DEG  C., and preferably being in the range from 800-1000 DEG  C., the furnace temperatures being 950-1015 DEG  C., and the preheating temperatures 600-650 DEG  C.  Condensible products are obtained.