Self cleaning reactor system

Abstract

This invention relates to a self cleaning reactor and to a process for the oligomerization of ethylene that employs a self-cleaning reactor. The reactor includes a mass of inert, particulate cleaning bodies that are entrained by the liquid in the reactor and scour the internal surfaces of the reactor during normal operation. This scouring action reduces the level of fouling on the reactor surfaces. Foulant material (polyethylene) is removed from the process on a continuous basis but the cleaning bodies remain within the reactor.

1 . A self cleaning, continuous flow reactor, said reactor comprising
 1) at least one inlet line for liquid reactants;   2) at least one outlet line for liquid products;   3) a mixing system to mix liquid contained within said reactor;   4) a mass of cleaning bodies contained within said reactor, with the provisos that
 a) said mixing system provides sufficient liquid velocity to suspend said cleaning bodies within said reactor; 
 b) said cleaning bodies have a particle size of from 2 millimeters to 2 centimeters; and 
 c) said cleaning bodies are retained within said reactor during operation of the reactor. 
   
     
     
         2 . The reactor of  claim 1  wherein said reactor is a continuously stirred tank reactor. 
     
     
         3 . The reactor of  claim 1  wherein said cleaning bodies have a particle size of from about 2 millimeters to about 2 centimeters and a specific gravity that is greater than the specific gravity of said liquid contained within said reactor. 
     
     
         4 . A process for the removal of by-product polyethylene from a continuous flow, mixed, oligomerization reactor, said process comprising:
 a) providing input flows comprising ethylene, solvent, and an oligomerization catalyst system to said reactor;   b) oligomerizing ethylene under continuous flow conditions within said reactor; and   c) providing a discharge stream from said reactor comprising solvent, oligomer product and polyethylene by-product; characterized in that said process is conducted in the presence of a mass of reactor cleaning bodies, with the proviso that substantially all of said cleaning bodies remain within said reactor during said process.   
     
     
         5 . The process of  claim 4  wherein said reactor is a continuously stirred tank reactor. 
     
     
         6 . The process of  claim 4  wherein said continuously stirred tank reactor is operated under stirring conditions that are sufficient to suspend a portion of said cleaning bodies. 
     
     
         7 . The process of  claim 4  wherein said cleaning bodies have a particle size of from about 2 millimeters to about 2 centimeters and a specific gravity that is greater than the specific gravity of said liquid contained within said reactor. 
     
     
         8 . The process of  claim 4  wherein said oligomerization catalyst system comprises a source of active chromium, an activator and a diphosphine ligand defined by the formula (R 1 )(R 2 )—P 1 -bridge-P 2 (R 3 )(R 4 ) wherein R 1 , R 2 , R 3  and R 4  are independently selected from the group consisting of hydrocarbyl and heterohydrocarbyl and said bridge is a moiety that is bonded to both phosphorus atoms. 
     
     
         9 . The process of  claim 4  wherein said solvent is an aliphatic solvent. 
     
     
         10 . The process of  claim 4  wherein the total rate of polymer deposition upon the walls of said oligomerization reactor is less than 1000 ppm per hour, based on [the total amount of oligomer product]. 
     
     
         11 . The process of  claim 4  wherein said cleaning bodies comprise a variety of cleaning bodies having different particle sizes.