GB790476A - Catalytic reforming - Google Patents

Abstract

Hydrocarbon fractions having a boiling range of about 60-450 DEG F. are reformed in the presence of a catalyst having a surface area of about 100-650 square metres per gram and containing about 0.05-2 per cent by weight of platinum and/or palladium deposited on silica containing about 0.025-7 per cent by weight of alumina, the surface area and the alumina content being correlated for maximum reforming activity (see Group III). Reforming conditions are a temperature of about 700-1000 DEG F., a hydrogen pressure of about 100-1000 p.s.i.g., a liquid hourly space velocity of about 0.1-10, and a molar ratio of hydrogen to hydrocarbon of about 1-20. The fraction treated may be a straight-run or cracked naphtha, gasoline, or kerosene, and may contain up to 0.4 per cent by weight or more of sulphur, and up to 30 per cent by volume or more of olefines. The process may use a fixed, moving, or fluidized bed of catalyst.ALSO:A catalyst suitable for reforming hydrocarbons (see Group IV (b)) has a surface area of about 100-650 square metres per gram and comprises about 0.05-2 per cent by weight of platinum and/or palladium deposited on silica which contains about 0.025-7 per cent by weight of alumina; the amount of alumina is correlated with the surface area to define a point falling within a specified area of a graph. Fig. 8 (not shown). The alumina can be incorporated with the silica by cogelation, by impregnation, or by both cogelation and impregnation. The silica-alumina carrier may be prepared: (a) by dispersing silica hydrogel in an aqueous solution of an aluminium salt and adding aqueous ammonia; (b) by mixing silica hydrogel with alumina hydrogel; (c) by mixing an acidic aqueous solution of an aluminium salt with a solution of sodium silicate to form hydrogel beads; (d) by forming silica hydrogel beads and ion exchanging with an acidic aqueous aluminium salt solution; (e) by dispersing calcined silica or silica-alumina gel in an aqueous solution of an aluminium salt and adding ammonia; (f) by mixing calcined silica or silica-alumina gel with wet alumina hydrogel; (g) by calcining silica or silica-alumina hydrogel beads and impregnating with an aluminium salt solution. The hydrogel beads used in the above methods may be prepared as described in Specification 576,058. Reduction of the surface area of the carrier may be effected by steaming at 900-1400 DEG F. under pressure, by heating at 1600-1800 DEG F., or by treatment with water at 300-800 DEG F. under pressure, and may take place before incorporation of the platinum or palladium or before impregnation of the carrier with alumina. The dried carrier is impregnated with an aqueous solution of chloroplatinic or chloropalladic acid or of the ammonium salts of these acids, then dried and reduced with hydrogen. In examples (1)-(3) a sodium silicate solution is mixed in a mixing nozzle with solutions containing sulphuric acid and various concentrations of aluminium sulphate; the mixture falls through a column of oil to form gel beads which are aged in water at 40 DEG F. and then base exchanged by nine treatments with ammonium sulphate solution; after drying and calcining, the carrier is heated for 17 hours with chloroplatinic acid solution at 230 DEG F., then heated in nitrogen, reduced with hydrogen, and cooled in nitrogen. Example 6 describes the preparation of silica gel by mixing ammonia solution with a solution containing ethyl orthosilicate, ethanol, methanol, and aqueous nitric acid; the gel is washed and dried and impregnated with chloroplatinic acid solution. In Examples (8)-(11) silica gel containing 0.05 per cent cogelled alumina is leached with dilute sulphuric acid, washed, dried, impregnated with aluminium nitrate solutions of various concentrations dried, calcined and impregnated with chloroplatinic acid solutions. In examples (13)-)17) silica gel containing 0.05 per cent cogelled alumina is impregnated with aluminium nitrate solutions of various concentrations, and then with chloroplatinic acid solutions of varying strength. Examples 4, 5, 11, 15 and 17 describe hydrothermal treatment to reduce the surface area; the carrier is suspended in an autoclave over distilled water and heated to 375-600 DEG F. at pressures of 100-900 p.s.i.g. The catalysts are tested by contacting with a mixture of normal heptane, cyclohexane, and hydrogen under reforming conditions and determining the yield of heptane isomer and benzene. The results are used to plot graphs showing, for catalysts of varying surface area and platinum content, the relations (a) between the temperature, heptane isomer yield, and benzene yield; and (b) between the alumina content of the catalyst, the maximum heptane isomer yield, and the benzene yield at maximum heptane isomer yield. From these graphs, the graph of Fig. 8 is obtained which shows the relation between alumina content and surface area for good reforming. The catalyst may be reactivated by treatment at 900-950 DEG F. with a gas of low oxygen content, increasing the oxygen concentration, and then treating with hydrogen at 1000 DEG F.