Continuous process for gas phase coating of polymerization catalyst

A continuous process for the gas phase coating of polymerization catalyst comprising introducing particles of a polymerization catalyst into a gas phase plug flow reactor, which reactor is tubular and is horizontal or is declined with a downward angle formed with a horizontal base line of between 1 and 7°, said tubular reactor having a centrally located and rotatable drive shaft extending longitudinally through the tubular reactor to which are attached a plurality of adjacently located paddles, said paddles being located on said rotatable drive shaft such that they do not cause any backward movement of the catalyst particles as they flow through the reactor and extend transversely within the reactor with respect to the longitudinal direction of the drive shaft to a distance of from 1 to 5 mm from internal surfaces of the reactor and longitudinally along the length of the reactor and are straight, rectangular, and perpendicular to the internal surfaces of the reactor, wherein the catalyst particles are submitted to polymerization conditions in the presence of at least one gaseous monomer to coat the catalyst particles such that at least 95% by weight of the produced coated catalyst particles have a coating yield of between 0.5 to two times the average coating yield.