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.

The invention relates to the production of olefin oligomers by a method of oligomerization of olefins, and, in particular, to a method of isolating olefin oligomerization products and decomposing the oligomerization catalyst residues. The method of isolating products of an oligomerization reaction of olefins including a terminal double bond, in which the reaction is carried out by the action of a catalyst having chromium compounds, a nitrogen-containing ligand and organoaluminum compounds, includes a step of isolating independent olefin products and a step of treating catalyst residues. Further, the method includes the following sequential steps: a) isolating at least one liquid product of the oligomerization reaction of olefins from an output stream of an oligomerization reactor; b) treating a residue with an aqueous solution of an acid; and c) separating an organic layer and an aqueous layer.

A process for the tetramerization of ethylene includes contacting ethylene with a catalyst under ethylene oligomerization conditions. The catalyst comprises a source of chromium, a ligating compound, and an activator. The ligating compound includes a phosphine that forms part of a cyclic structure.

A process for the oligomerization of ethylene to predominantly 1-hexene or 1-octene or mixtures of 1-hexene and 1-octene includes contacting ethylene with a catalyst under ethylene oligomerization conditions. The catalyst comprises a source of chromium, a diphosphine ligating compound, and optionally an activator. The diphosphine ligating compound includes at least one optionally substituted fused cyclic structure including at least two rings, the optionally substituted fused cyclic structure including a 5- to 7-membered aromatic first ring bonded to a phosphorus atom, the aromatic first ring being fused to a 4- to 8-membered heterocyclic second ring, the heterocyclic second ring including a heteroatom which is separated by two ring atoms along the shortest connecting path from the phosphorous atom that is bonded to the first aromatic ring.

A process for the oligomerization, preferably the tetramerization, of ethylene to predominantly 1-hexene or 1-octene or mixtures of 1-hexene and 1-octene includes contacting ethylene with a catalyst under ethylene oligomerization conditions. The catalyst comprises a source of chromium, a diphosphine ligating compound, and optionally an activator. The diphosphine ligating compound includes at least one substituted aromatic ring bonded to a phosphorous atom. The substituted aromatic ring is substituted at a ring atom adjacent to the ring atom bonded to the respective phosphorous atom with a group Y, where Y is of the form AR.sup.EWG, A being O, S or NR.sup.5, where R.sup.5 is a hydrocarbyl, heterohydrocarbyl or organoheteryl group, and R.sup.EWG is an electron withdrawing group.

Disclosed is a method of preparing propylene including the step of irradiating propane in the presence of a catalyst containing a decatungstate salt and a co-catalyst, in which the co-catalyst has cobalt or nickel. Also provided are catalysts and methods of dehydrogenating alkanes.