Dry catalyst feeder for polymerization reactors

Abstract

A device and method allow a dry catalyst to be delivered to a liquid-filled polymerization reactor, thus avoiding problems associated with catalyst-liquid contact or with undesired addition of gases to the reactor. A quantity of dry catalyst is transferred from a catalyst reservoir maintained under dry conditions to a catalyst chamber. An inert fluid then enters the chamber to flush the catalyst charge toward the reactor. Optional embodiments include means for precontacting the dry catalyst with a modifier and for removing gas from the fluid line.

We claim:  
     
         1 . An apparatus for feeding a dry catalyst to a reactor, comprising 
 (a) a liquid-filled reactor;    (b) a first fluid line connected to the reactor;    (c) a second fluid line leading from an upstream connection in the first line to a downstream connection in the first line and thereby constituting a bypass line;    (d) a valve means for directing a flow of fluid alternately through the first line and the bypass line;    (e) a means for venting the bypass line to about atmospheric pressure while fluid is flowing through the first line;    (f) a catalyst reservoir adapted to contain a quantity of dry catalyst under pressurized inert gas;    (g) a catalyst chamber having inlet and outlet fluid connections to the bypass line and having a catalyst line connection to the catalyst reservoir for transferring a quantity of dry catalyst from the reservoir; and    (h) a means for opening the catalyst chamber to communication alternately with the catalyst line and the bypass line.    
     
     
         2 . The apparatus of  claim 1  further comprising a valve-controlled gas line, connected to the bypass line upstream from the catalyst chamber, for injection of inert gas.  
     
     
         3 . The apparatus of  claim 1  in which the catalyst chamber is a plug valve.  
     
     
         4 . The apparatus of  claim 1  further comprising a valve-controlled fluid line, connected to the bypass line upstream from the catalyst chamber, for injection of a modifier.  
     
     
         5 . The apparatus of  claim 1  further comprising a modifier precontact vessel in a line downstream from the catalyst chamber.  
     
     
         6 . The apparatus of  claim 1  further comprising a means, communicating with the line between the catalyst chamber and the reactor, for removing gas from liquid.  
     
     
         7 . The apparatus of  claim 1  further comprising a catalyst feeder in the catalyst line connection between the catalyst reservoir and the catalyst chamber.  
     
     
         8 . The apparatus of  claim 7  in which the feeder is a single-port ball valve.  
     
     
         9 . The apparatus of  claim 7  further comprising a means for providing pressurized inert gas to assist the flow of catalyst from the feeder to the catalyst chamber.  
     
     
         10 . The apparatus of  claim 2  further comprising 
 (a) a feeder in the catalyst line connection between the catalyst reservoir and the catalyst chamber  
 (b) a means for providing pressurized inert gas to assist the flow of catalyst from the feeder to the catalyst chamber  
 (c) a valve-controlled fluid line, connected to the bypass line upstream from the catalyst chamber, for injection of a metal alkyl; and  
 (d) a means, situated in a fluid line between the catalyst chamber and the reactor, for removing gas from liquid.  
 
     
     
         11 . A method of feeding dry catalyst to a polymerization reactor comprising: 
 (a) feeding an inert liquid hydrocarbon to a liquid-filled polymerization reactor through a feed line, the feed line having a connection to a second line which connects again to the feed line at a point downstream thereby defining a bypass loop;    (b) venting the bypass loop to about atmospheric pressure while the hydrocarbon is flowing through the feed line and the hydrocarbon is blocked from entering the bypass loop;    (c) transferring a quantity of dry catalyst through a catalyst inlet which leads from a catalyst reservoir to a catalyst chamber capable of being alternately in communication with the catalyst inlet and with the bypass loop;    (d) flushing the catalyst toward the reactor by blocking the catalyst inlet while allowing the hydrocarbon to flow into the bypass loop and through the catalyst chamber; and    (e) blocking the bypass loop to allow hydrocarbon flow through the feed line.    
     
     
         12 . The method of  claim 11  further comprising introducing an inert gas to the bypass loop while venting the bypass loop.  
     
     
         13 . The method of  claim 12  in which the inert gas is nitrogen.  
     
     
         14 . The method of  claim 11  in which the liquid-filled reactor is a slurry loop reactor.  
     
     
         15 . The method of  claim 11  in which the liquid hydrocarbon is selected from the group consisting of alkanes and aromatic hydrocarbons or mixtures thereof.  
     
     
         16 . The method of  claim 15  in which the liquid hydrocarbon is an alkane is selected from isobutane or hexane.  
     
     
         17 . The method of  claim 16  in which the alkane is isobutane.  
     
     
         18 . The method of  claim 16  in which the alkane is hexane.  
     
     
         19 . The method of  claim 11  in which the catalyst is a Ziegler-Natta catalyst  
     
     
         20 . The method of  claim 11  in which the catalyst is an organometallic single-site catalyst.  
     
     
         21 . The method of  claim 11  in which the catalyst contains chromium.  
     
     
         22 . The method of  claim 19 ,  20  or  21  in which the catalyst is supported on an inorganic oxide support  
     
     
         23 . The method of  claim 22  in which the support is silica.  
     
     
         24 . The method of  claim 11  further comprising contacting the catalyst with a modifier after the catalyst has left the catalyst reservoir and but before the catalyst enters the reactor.  
     
     
         25 . The method of  claim 24  in which the modifier contacts the catalyst in the catalyst chamber.  
     
     
         26 . The method of  claim 24  in which the modifier contacts the catalyst at a point downstream from the catalyst chamber.  
     
     
         27 . The method of  claim 24  in which the modifier is a metal alkyl is selected from the group consisting of triethylaluminum, trimethylaluminum, triisobutylaluminum, methylalumoxane and modified methylalumoxane.  
     
     
         28 . The method of  claim 11  further comprising removing gas from the hydrocarbon at a point in the fluid line downstream from catalyst reservoir and but upstream from the reactor.  
     
     
         29 . The method of  claim 11  further comprising maintaining the catalyst reservoir under an inert gas at superatmospheric pressure.  
     
     
         30 . The method of  claim 11  in which the catalyst chamber is a rotatable valve.  
     
     
         31 . The method of  claim 11  in which the dry catalyst, while passing from the catalyst reservoir to the catalyst chamber, also passes through a catalyst feeder.  
     
     
         32 . The method of claim  30  further comprising the use of pressurized inert gas to transfer the dry catalyst from the catalyst feeder.