Process for pretreatment of light hydrocarbons to remove sulfur, water, and oxygen-containing compounds

A catalytic isomerization process in which a feed stream comprising paraffins having from 4 to 6 carbon atoms per molecule and substantially free of sulfur compounds, oxygenates and water is isomerized in a reaction zone in the presence of an isomerization catalyst at isomerization conditions to produce a product having increased octane value compared to the feed, said feed stream having previously been subjected to a pretreatment process which comprises:

• (a) passing a hydrocarbon stream comprising paraffins having 4 to 6 carbon atoms per molecule, mercaptans, carbon disulfide, carbonyl sulfide, oxygenates and water through a first adsorption zone comprising 13X zeolite maintained at a temperature of 25.degree. to 100.degree. C., a pressure less than 3448 kPa (ga), and a space velocity of from 1 to 5 volumes per hour per volume of first adsorption zone;
• (b) thereafter passing the effluent from the first adsorption zone through a second adsorption zone comprising activated alumina maintained at a temperature of from 25.degree. to 100.degree. C., a pressure less than 3448 kPa (ga), and a space velocity of from 1 to 5 volumes of feedstock per hour per volume of second adsorption zone;
• and
• (c) recovering the effluent from the second adsorption zone with the effluent containing less than 1 wt. ppm carbon disulfide.