GB710537A - Process for the polymerization of olefins - Google Patents

Abstract

Lower olefins are polymerized to polymers of gasoline boiling range in the presence of a finely divided, solid polymerization catalyst maintained as an agitated suspension in a hydrocarbon phase, at least part of said catalyst being subjected to mechanical action to reduce the particle size and provide fresh surfaces for exposure to the reactants, said mechanical <PICT:0710537/IV (b)/1> action being controlled to maintain the activity of the catalyst substantially constant. The size reduction may be effected by continuously or periodically subjecting at least part of the catalyst to mechanical attrition, grinding or pulverizing means. Catalysts effective at about 350-600 DEG F., and pressures of, e.g. 20-1000 p.s.i.g. or more, according to whether the hydrocarbon is in a true vapour or liquid or liquid and vapour phase, are used and include "solid" phosphoric acid, preferably made by drying and calcining a mixture of silica hydrogel and the acid, copper pyrophosphate, zirconia, thoria and activated alumina, if desired with supports. The fresh catalyst has a particle size of 40-600 microns, and may be reduced to a final size of 2-150 microns depending on the efficiency of the separating means for treating the effluent. The surface area of the particles should increase at 0.5-10, preferably 2-6 per cent per hour. The feed may contain 30-90 per cent or more of olefins, ethylene generally being low. The reactor 11 has a stirrer 13 with vertical vanes 16 inclined at an angle to the edges of support 17. A speed of 200 r.p.m. keeps the catalyst of 70-450 microns size in suspension, while baffles 18 serve to settle particles larger than 3 microns, the product leaving at 21. The stirrer speed is increased by 50-100 r.p.m. as needed to maintain the conversion by pulverizing catalyst. When a point is reached at which increased speed does not suffice, part of the catalyst slurry is withdrawn to pulverizing means 26 and recycled by line 28. Fresh catalyst is added and slurry withdrawn as necessary. In modifications, the pulverizing means is located within the reactor or the feed is jetted at high velocity against an anvil, the slurry being inducted and catalyst disintegrated. In a hindered settler type of polymerizer, conditions may be adapted to give liquid and gas phases in contact, the liquid phase containing catalyst being drawn off and recycled lower down where it is jetted against an anvil. Examples illustrate the rate of attrition and surface area increase of catalyst and the relationship with activity in the polymerization of C3 feeds, using phosphoric acid-silica gel with and without nickel phosphate, and phosphoric acid-kieselguhr-active carbon.