Patent GB-720406-A (GB)
Title: Improvements in or relating to polymerization of olefins with slurried catalysts
IPC: C07C2/18
Filed: 1952-03-14
Abstract: Normally gaseous olefins are polymerized to polymers of gasoline boiling range by forming an agitated suspension of finely divided solid phosphoric acid catalyst in a "dense phase" hydrocarbon fluid containing said olefins, continuously introducing feed containing said olefins and less than 1 p.p.m. of fixed nitrogen at a space velocity of 0.1-2.5 U.S. gallons/hr./lb. catalyst, a temperature of 350-600 DEG  F. and a pressure above 450 p.s.i.g. being maintained, continuously withdrawing substantially solid-free fluid effluent including polymers, withdrawing part of the deactivated catalyst and replacing with fresh catalyst as needed.  "Dense phase" means a true liquid phase or the phase intermediate-true gas and true liquid which exists at or near critical temperatures and pressures.  A feed containing less than 4 p.p.m. of fixed nitrogen may be used in a multi-stage process as above, each stage comprising a suspension of the catalyst and withdrawn effluent from each stage being introduced into the next.  Water is preferably injected at a rate which increases as reaction progresses, e.g. 0.1-0.4 gals. per 1000 gals. of feed increasing to 0.45-0.6 gal. after 10-50 hours.  The feed is preferably at such a temperature below that of reaction as to absorb the exothermic heat while in multi-stage operation interstage cooling of effluent is utilized.  The feed, preferably containing 30-90 per cent olefins, passes through a guard chamber containing silica gel or caustic alkali to remove nitrogen compounds and reduce the nitrogen content below the stated figure.  It then passes, at least in part, through a water saturator which is maintained at p  about 50-110 DEG F. and which may later be increased to 150 DEG  F. to give the desired water content.  After heating to the required temperature, it passes upwards through the suspended catalyst in a reactor of the hindered settler type.  The catalyst is of 20-200 mesh per linear inch and the superficial velocity of the hydrocarbon through the reactor 1-5 ft./min. to maintain a slurry of catalyst from the upper portion of which catalyst falls back through gravity.  Effluent is withdrawn at the top and is distilled to recover polymers, if necessary after filtration or further settling.  Slurry is withdrawn from the bottom of the reactor and fresh catalyst, slurried in polymer or other hydrocarbon, added to the upper portion.  Pressure is usually 900 p.s.i.g. or above, preferably near the critical pressure. Stirrers are preferably used.  In a three-stage process using a C3 feed, 50 per cent propylene, the feed is at 270 DEG  F., the reactors at 450 DEG  F., and interstage cooling of effluent to 340 DEG  after stage 1 and 300 DEG  after stage 2 is effected. Preferably, catalyst and feed flow in counter-current.  When overall conversion reaches 85 per cent., the first reactor may be withdrawn and a reactor containing fresh catalyst added at the other end.  The catalyst should contain about 50-90 per cent phosphoric acid by weight.  With feeds containing ethylene and propylene, space velocities will generally be below 1.5 gals/hr./lb.  Experimental results are given illustrating the deactivating effect of nitrogen compounds, the effects of pressure, feed rate, and controlled water addition, and the advantages of multistage operation.