GB798018A - Improved hydroforming process - Google Patents

Abstract

In hydroforming naphthas in the presence of a platinum-group metal catalyst the naphtha feed is separated into a first fraction boiling below 200 DEG F. and a second fraction boiling above 200 DEG F. and each fraction is separately hydroformed, the first fraction being hydroformed under conditions of lower hydrogen partial pressure and lower total pressure than the second fraction. It is preferred that one or more of the following conditions are also employed during the hydroforming of the lower boiling fraction as compared to conditions when hydroforming the higher boiling fraction. The hydrogen-containing recycle gas has a higher heat capacity due to the presence of a higher volume content of hydrocarbons; this may be accomplished by the extraneous addition of hydrocarbons, this also reduces the partial pressure of the hydrogen, alternatively the effluent from the hydroforming may be condensed at a higher temperature, e.g. at 200-325 DEG F. instead of 90-115 DEG F., whereby less hydrocarbon content is removed by condensation. The hydrogen-containing gas is fed at a lower rate to the system, in which case the total reaction pressure is preferably less, this prevents the necessity of increasing the energy requirements for circulating the recycle gas. Using a platinum or palladium catalyst suitably supported the following conditions are preferred for the hydroforming of the higher boiling fraction, corresponding figures for the lower boiling fraction being given in parentheses: Inlet temperature DEG F. 900-1000 (900-1000) Total pressure, p.s.i.g. 350-600 (50-300) Residence time, sec. 4-20 (8-25) Recycle gas feed to reactor, SCF/barrel oil 4,000-10,000 (1500-3000) Density of recycle gas relative to air . 0.1-0.4(0.4-1.0) Concentration of H2 in recycle gas, mol. per cent . . . 70-95 (55-75) Temperature of condensation of products DEG F. . . 90-115 (200-325) Specification 742,563 is referred to.