Studies On The Novel Catalyst Systems For The Carbonylation And Oxidation Reaction Of Arenes

Aromatics are abundant in oil and natural gas, they are important materials in chemical industry. It is of obvious advantage if direct carbonylation reaction can carry out from cheap aromatics to corresponding aldehydes, ketones, acids and esters, instead of via functionalization.In the dissertation, the carbonylation reaction of arenes, such as benzene and toluene, were studied. There are mainly two types of catalyst systems investigated. Firstly, cobalt complex catalyst system, such as Co(OAc)₂/CCl₃COOH/O₂/pyridine. Secondly, super acid ionic liquids, not only as solvents but also as the catalyst.In the thesis, the carbonylation reaction of benzene to benzaldehyde was investigated. Benzene was converted to benzaldehyde with relatively high yield (37.3%) and selectivity (80 %) under mild conditions catalyzed by the catalyst system Co(OAc)₂/CCl₃COOH/O₂/N-containing or P-containing additive. In the catalyst system, Co(OAc)₂ was used to replace Pd(OAc)₂, CCl₃COOH instead of CF₃COOH, oxygen instead of K₂S₂O₈, the N-containing or P-containing additives in the catalyst system such as pyridine, 2, 2'-bipyridine, triphenylphosphine, were important in changing the selectivity of the products from benzoic acid to benzaldehyde, the main product was benzaldehyde, phenol, chloride benzene and benzoic acid were the byproducts. The influence of various reaction conditions on reaction performance was shown. A possible reaction mechanism was proposed.A series of ionic liquids were synthesized, the organic cation was mainly based on the 3-alkyl-1-methyl-imidazole and 1- alkyl pyridine, the anion was mainly halide, BF₄^-, PF₆^- and Al₂Cl₇^-, etc. The acidity was characterized with acetonitrile as the probe molecule, and the order of the Lewis acidity of ionic liquids based on the 3-butyl-1-methyl-imidazole was: [bmim]Cl/ZnCl₂＜[bmim]Cl/FeCl₃＜[bmim]Cl/ AlCl₃＜[bmim]Br/AlCl₃.In the thesis, the carbonylation reaction of arenes such as benzene, toluene and naphthalene, was investigated in the ionic liquids based on 3-alkyl-1-methyl-imidazole/AlCl₃. For toluene, it was converted to p-tolualdehyde via selective carbonylation reaction, under the optimum reaction condition, catalyzed by [bmim]Br/AlCl₃, toluene was converted to p-tolualdehyde with the convertion of 96 % and yield of 86 %; Benzene was converted to benzaldehyde with relatively high yield (91%)and selectivity (96 %) catalyzed by the super acid ionic liquids. The recycle of the ionic liquids was investigated. The selective carbonylation reaction of other arenes such as naphthalene,β-methyl naphthalene and chloride benzene can also carry out in the catalyst system, naphthalene was converted to a-naphthalene aldehyde with, the yield of 71 %. The influence of acid strength of the ionic liquids, reaction temperature, reaction time, and CO pressure was studied. It is found that the catalytic activity of the super acid ionic liquids was obviously high than the B-L acid and solid super acid. A possible reaction mechanism was proposed.In the thesis, the oxidation reaction of toluene to benzoic acid was investigated using oxygen as oxidant. The catalyst system was composed of N-hydroxyphthalimide (NHPI) and cobalt salts, such as NHPI-Co(acac)₂ and NHPI-Co(OAc)₂. The experimental results revealed that the yields of benzoic acid catalyzed by NHPI-Co(acac)₂ and NHPI-Co(OAc)₂ can reach 55.5 % and 41.2 %, respectively. The influences of oxygen pressure, reaction temperature and time on the yields of benzoic acid were discussed. A possible reaction mechanism was proposed.