The present invention relates to a process for the polymerization of olefin monomers in the presence of a catalyst system, using a tubular pre-polymerization reactor, wherein the tubular pre-polymerization reactor has a length L and the flow of a catalyst system is introduced in the tubular pre-polymerization reactor in the middle (30-70% of L) or the end (70-95% of L) of the tubular pre-polymerization reactor.

A slurry reactor system including a slurry reactor configured to convert, under slurry hydroconversion conditions, a slurry reactor content flowing upwards and containing a feedstock including one or more of fats, oils and greases, a slurry hydroconversion catalyst and a hydrogen stream to a slurry hydroconversion effluent containing a slurry phase effluent including catalyst particles and a liquid product and a vapor phase effluent including a hydroconversion product, and a separation unit internal to the slurry reactor, the separation unit being configured to separate at least a portion of the vapor phase effluent from the slurry hydroconversion effluent to produce a mixture of vapor and the slurry hydroconversion effluent having a reduced vapor phase content. The separation unit is configured to use a pump to recirculate the mixture of vapor and the slurry hydroconversion effluent flowing downwards in the slurry reactor to be combined with the slurry reactor content.

A slurry reactor system including a slurry reactor configured to convert, under slurry hydroconversion conditions, a slurry reactor content flowing upwards and containing a feedstock including one or more of fats, oils and greases, a slurry hydroconversion catalyst and a hydrogen stream to a slurry hydroconversion effluent containing a slurry phase effluent including catalyst particles and a liquid product and a vapor phase effluent including a hydroconversion product, and a separation unit internal to the slurry reactor, the separation unit being configured to separate at least a portion of the vapor phase effluent from the slurry hydroconversion effluent to produce a mixture of vapor and the slurry hydroconversion effluent having a reduced vapor phase content. The separation unit is configured to use a pump to recirculate the mixture of vapor and the slurry hydroconversion effluent flowing downwards in the slurry reactor to be combined with the slurry reactor content.