There is a process for the preparation of polypropylene carbonate having the step of copolymerization of propylene oxide and carbon dioxide (CO.sub.2) in the presence of a catalytic system including: at least one catalyst selected from complexes of a transition metal having general formula (I):

##STR00001## at least one co-catalyst selected from: (a) ionic compounds having general formula (II):

##STR00002## and (b) ionic compounds having general formula (III)

##STR00003##

A method for C—H bond activation and/or C—N coupling reaction comprises using a metal catalyst to catalyze the C—H bond activation and/or C—N coupling reaction; wherein the metal catalyst represented by the following formula a metal catalyst for C—H bond activation and/or C—N coupling reaction, and a method using the same and application thereof. Specifically, a metal catalyst represented by the following formula: ##STR00001##
wherein Q is a 5 or 6 membered aromatic ring; W, X, and Y are the same or different, and are independently N, S, P, or O; M is Ni, Pd, Fe, Co, Cr, Mn, Cu, Pt, Ir, or Ru; Z is halide (F, Cl, Br, or I), acetate, water, or hydroxyl; R.sub.1 and R.sub.2 are the same or different, and are independently alkyl, aryl, alkylaryl or cycloalkyl.

The disclosure provides a catalyst system and a method for ethylene oligomerization using this. The catalyst system contains: ligand a, containing carbene groups of imidazole ring type; transition metal compound b, that is one of IVB˜VIII group metal compounds; activator c, that is a compound containing III A group metals; the ligand a contains at least one group as shown in general formula I: ##STR00001##
in which, bridging group A contains a main chain including alkyl, alkenyl, aryl groups or the combination of them and the first heteratom; E is a linear or cyclic group containing the second heteroatom; R is a hydrocarbyl group. The catalyst system is especially used for trimerization and tetramerization of ethylene. The catalyst system has high selectivity for 1-hexene and 1-octene, low selectivity for 1-butene and 1-C.sub.10+, and the total percent content of C.sub.6˜C.sub.8 linear □α-olefin in the product is more than 90% by mass.

Supported chromium catalysts with an average valence less than +6 and having a hydrocarbon-containing or halogenated hydrocarbon-containing ligand attached to at least one bonding site on the chromium are disclosed, as well as ethylene-based polymers with terminal alkane, aromatic, or halogenated hydrocarbon chain ends. Another ethylene polymer characterized by at least 2 wt. % of the polymer having a molecular weight greater than 1,000,000 g/mol and at least 1.5 wt. % of the polymer having a molecular weight less than 1000 g/mol is provided, as well as an ethylene homopolymer with at least 3.5 methyl short chain branches and less than 0.6 butyl short chain branches per 1000 total carbon atoms.

Catalyst systems suitable for tetramerizing ethylene to form 1-octene may include a catalyst including a chromium compound coordinated with a ligand and a co-catalyst including an organoaluminum compound. The ligand may have a chemical structure: (R.sub.1)(R.sub.2)A-X—C(R.sub.3)(R.sub.4). A and C may be phosphorus. X may be B(R.sub.5), Si(R.sub.5).sub.2, N(R.sub.5), wherein R.sub.5 is an aryl group substituted with a halogen, halogenated alkyl or a silyl group, and wherein B, or N, or Si is bound to A and C. R.sub.1, R.sub.2, R.sub.3, and R.sub.4 may be independently chosen hydrocarbyl groups or heterohydrocarbyl groups.

The invention relates to the field of oligomerization of olefins to produce linear α-olefins, in particular hexene-1, with the use of a catalyst system. The catalyst system comprises a chromium source compound, a nitrogen-containing ligand, alkylaluminum, and a zinc compound, wherein catalyst system is activated during its preparation by 1) heating some and SHF irradiation (microwave irradiation) of alkylaluminum or a mixture of the alkylaluminum and the zinc compound, or by 2) heating alkylaluminum or a mixture of the alkylaluminum and the zinc compound, followed by holding (aging) the prepared catalyst system for a certain period of time.

A method for preparing a homogenous catalyst for use in preparing a linear alpha olefin includes: preparing a first pre-catalyst solution by mixing a chromium source and a ligand in a first solvent, wherein the first pre-catalyst solution is stored in a first vessel; preparing a second pre-catalyst solution by mixing an organoaluminum compound and a modifier in a second solvent, wherein the second pre-catalyst solution is stored in a second vessel; and simultaneously feeding the first pre-catalyst solution and the second pre-catalyst solution directly into a reaction vessel, wherein the reaction vessel includes a third solvent.

The present disclosure provides a method and a catalyst for selective oligomerization of ethylene. The raw material for the catalyst consists of a dehydropyridine annulene-type ligand, a transition metal compound, and an organometallic compound in a molar ratio of 1:0.5-100:0.1-5000. The present disclosure also provides a method for selective oligomerization of ethylene accomplished by using the above-mentioned catalyst. The catalyst for selective oligomerization of ethylene has high catalytic activity, high selectivity for the target products 1-hexene and 1-octene, and low selectivity for 1-butene and 1-C.sub.10.sup.+.

According to one embodiment, a catalyst system that reduces polymeric fouling may include at least one chromium compound, at least one aluminum compound, and at least one antifouling agent or a derivative thereof. The antifouling agent may have a structure including a central aluminum molecule bound to an R1 group, bound to an R2 group, and bound to an R3 group. One or more of the chemical groups R1, R2, and R3 may be antifouling groups having the structure —O((CH.sub.2).sub.nO).sub.mR4, a phosphonium or phosphonium salt, a sulfonate or sulfonate salt, a sulfonium or sulfonium salt, an ester, an anhydride, a polyether, or a long-chained amine-capped compound, where n is an integer from 1 to 20, m is an integer from 1 to 100, and R4 is a hydrocarbyl group. The chemical groups R1, R2, or R3 that do not include an antifouling group, if any, may be hydrocarbyl groups.

A halogen-containing compound as shown in a formula I can be used as a ligand for an ethylene oligomerization catalyst composition. The ethylene oligomerization catalyst composition containing the halogen-containing compound can be used to catalyze ethylene oligomerization, trimerization and tetramerization reactions. As a ligand of a catalyst for ethylene oligomerization, a fluoropolymer can effectively improve the catalytic performance of a catalyst system, and particularly exhibits improved activity and selectivity in an ethylene oligomerization reaction. ##STR00001##