Process for hydrogenating aromatic compounds over a solid catalyst in the presence of a hydrogen-containing gas comprising a first reactor operated in loop mode, a second reactor operated in straight pass, at least part of the output of the first reactor is supplied to the second reactor, characterized in that the first reactor is configured as a trickle bed reactor and is operated in trickle bed mode and the second reactor is operated such that the catalyst present therein is partially flooded.

Methods for simultaneously determining the concentrations of transition metal compounds in solutions containing two or more transition metal compounds are described. Polymerization reactor systems providing real-time monitoring and control of the concentrations of the transition metal components of a multicomponent catalyst system are disclosed, as well as methods for operating such polymerization reactor systems, and for improving methods of preparing the multicomponent catalyst system.

A process for polymerizing olefin monomer(s) in a gas-solids olefin polymerization reactor comprising a top zone; a middle zone, which comprises a top end in direct contact with said top zone and which is located below said top zone, the middle zone having a generally cylindrical shape; and a bottom zone, which is in direct contact with a bottom end of the middle zone and which is located below the middle zone; comprising the following steps: introducing a fluidization gas stream into the bottom zone; polymerizing olefin monomer(s) in the presence of a polymerization catalyst in a dense phase formed by particles of a polymer of the olefin monomer(s) suspended in an upwards flowing stream of the fluidization gas in the middle zone; introducing a jet gas stream through one or more jet gas feeding ports in a jet gas feeding area of the middle zone at the dense phase in the middle zone of the gas-solids olefin polymerization reactor; wherein the kinetic energy (E.sub.JG) input in the reactor by the jet stream is between 1.5 and 50 times higher than the kinetic energy (E.sub.FG) input in the reactor by the fluidization gas stream (FG).

Methods for simultaneously determining the concentrations of transition metal compounds in solutions containing two or more transition metal compounds are described. Polymerization reactor systems providing real-time monitoring and control of the concentrations of the transition metal components of a multicomponent catalyst system are disclosed, as well as methods for operating such polymerization reactor systems, and for improving methods of preparing the multicomponent catalyst system.

Polymerization processes and reactor systems for producing multimodal ethylene polymers are disclosed in which at least one loop reactor and at least one fluidized bed reactor are utilized. Configurations include a loop reactor in series with a fluidized bed reactor and two loop reactors in series with a fluidized bed reactor.

Polymerization processes and reactor systems for producing multimodal ethylene polymers are disclosed in which at least one loop reactor and at least one fluidized bed reactor are utilized. Configurations include a loop reactor in series with a fluidized bed reactor and two loop reactors in series with a fluidized bed reactor.

Methods for simultaneously determining the concentrations of transition metal compounds in solutions containing two or more transition metal compounds are described. Polymerization reactor systems providing real-time monitoring and control of the concentrations of the transition metal components of a multicomponent catalyst system are disclosed, as well as methods for operating such polymerization reactor systems, and for improving methods of preparing the multicomponent catalyst system.

Metathesis of olefins in a loop reactor having liquid reaction medium circulated therein that contains reactant olefins and homogeneous metathesis catalyst system in liquid phase. Recovery of product olefin(s) occurs after removing a liquid reactor effluent from the loop reactor, and unreacted reactant olefin(s) recovered from the liquid reactor effluent can be recycled to the loop reactor.

A method of producing bimodal ethylene-based polymer includes reacting ethylene monomer and C.sub.3-C.sub.12 α-olefin comonomer in the presence of a first catalyst in an agitated reactor to produce a first polymer fraction, and outputting effluent from the agitated reactor. A second catalyst is added to the effluent downstream of the agitated reactor and upstream from a non-agitated reactor, the second catalyst facilitates production of a second polymer fraction having a density and melt index (I.sub.2) different from the first polymer fraction. The second catalyst and effluent are mixed in at least one mixer. The second catalyst, second polymer fraction, and the first polymer fraction are passed to the non-agitated reactor; and additional ethylene monomer, additional C.sub.3-C.sub.12 α-olefin comonomer, and solvent are passed to the non-agitated reactor to produce more second polymer fraction and thereby the bimodal ethylene-based polymer.

An exemplary reactor system may include a first reactor, a second reactor, a third reactor, and a fourth reactor. The first reactor may be in parallel with the second reactor and the third reactor. The second reactor and third reactor may be in series. The fourth reactor may be configured to receive reduced oxygen carriers from the other reactors, generate oxidized oxygen carriers, and provide the oxidized oxygen carriers back to the other reactors. Carbonaceous feedstock may be used within one or more reactors.