GB662002A - Catalytic hydrocarbon conversion process - Google Patents

Abstract

Substantially olefin-free hydrocarbons of gasoline boiling range are passed in series through at least two substantially adiabatic reaction zones containing beds of successively increasing amounts of reforming catalyst with reheating between reaction zones, the inlet temperature to each zone and the amount of catalyst therein being so correlated that the temperature drop in the last zone is substantially less than D T/n and the temperature drop in each of the preceding zones is greater than D T/4n, where D T is the sum of the temperature drop in each of the zones and n is the number of zones. A naphthenic fraction boiling below about 220 DEG C. may be passed with hydrogen through the said zones containing platinum-alumina, with preheating between zones to the temperature of the charge to the first. The temperature drop in the final reactor is preferably greater than D T/4n for a two zone system, and has a minimum of D T/12n for a three zone, and of D T/24n for a four zone system. In a two zone system, the temterature drop in the first is preferably 68 per cent, and in the second 32 per cent of the sum D T. Preferred charge stocks consist of naphthenes and paraffins although small amounts of aromatics may be present. Pure naphthenes such as cyclohexane and methylcyclohexane may be treated. The temperature of the charge to each of at least two reaction zones containing successively increasing amounts of catalyst may be adjusted so that each catalyst bed is kept at substantially the same effective average temperature, the method of calculating which is described. With the preferred catalysts made by precipitating aluminium hydroxide from its salt solutions, adding halogen, e.g. as HF or HCl or their ammonium salts, admixing a colloidal platinic sulphide, prepared from chloroplatinic acid and H2S, drying, and, if desired, calcining or reducing, reforming is effected at about 425-510 DEG C., 3.5-100 atmos., a weight hourly space velocity of 0.2-40, and addition of 0.5-15 moles of hydrogen per mole of hydrocarbon. Platinum on charcoal, asbestos or silica-alumina, and corresponding palladium catalysts may be used. Removal of sulphur from the charge is necessary. Fluidized catalyst operation may be employed. In an example of working, a straight run gasoline is fractionated into light and heavy naphthas, and the latter passed through three reactors containing respectively 25, 25 and 50 per cent of the catalyst, the inlet temperature being 454 DEG C. and the outlet temperatures 299 DEG , 426 DEG and 443 DEG C. The liquid product is de-ethanized and sent with the original light naphtha to a stabilizer to yield a product of desired vapour pressure.ALSO:Reforming catalysts comprise platinum and alumina and, preferably, minor amounts of a halogen, especially chlorine and fluorine. Aluminium hydroxide may be precipitated from its salt solutions with alkali, halogen added as HF or HC1 or their ammonium salts, a colloidal suspension of platinic sulphide, prepared from chloroplatinic acid, admixed therewith, and the product dried, and calcined or reduced. The platinum content is usually about 0.05-5 per cent, and the halogen is usually less than 3 per cent of the dry alumina.