Study On Homogeneous Catalyst System For The Production Of Acetic Acid By Methanol Carbonylation

Acetic acid is an important chemical material, which is produced by methanol carbonylation as the main method. Owing to mild reaction conditions, high activity and high selectivity, iridium-based catalyst has been extensively studied. In the work, the system of iridium-based catalyst based previous research in the laboratory has been investigated comprehensively, and the stability of the catalyst was improved by adding ionic liquid into the homogeneous catalytic system. The reaction conditions of homogeneous catalytic system were discussed further, and the concentration of methyl iodide is 17%, the catalytic activity is improved.The major research contents are as follows:①The conversion rate of methanol was more than 99%, and the selectivity for acetic acid was 80% in the iridium- iodine catalytic system. The catalyst activity reached a higher level by the catalytic reaction of iridium repeatedly m within 2 h, the conversion rate of methanol was more than 99%, the selectivity for acetic acid was 80%, the selectivity for methyl acetatec was 1.7%, the carbonylation rate was 79.7% and the space-time yield of acetic acid was 7.9 mol/(L.h) in the homogeneous iridium- iodine catalytic system.②At the same time, the conversion rate of methanol was above 90%, the selectivity for methyl acetatec was reduced from 87% to 1.5%, the carbonylation rate was decreased range 90% to 9.6%, and the space-time yield of acetic acid was decreased from 5.7 mol/(L.h) to 0.1 mol/(L.h) after catalyzing reaction repeatedly in the iridium- iodine catalytic system.③The conversion rate of methanol, the selectivity and the space-time yield of acetic acid showed a better stability, then the conversion rate of methanol was up to 99%, the selectivity for acetic acid was 80% and the space-time yield of acetic acid could be maintained from 5.0 mol/(L.h) to7.8 mol/(L.h) by adding promoter of RuCl3 into the iridium- iodine catalytic system with the catalysis of 5 times repeatedly.④The methanol carbonylation reaction rate was promoted, the space-time yield of acetic acid was increased from 5.1 mol/ (L.h) to 16.1mol/ (L.h) by adding iodide into the iridium- iodine catalytic system, especially for lithium iodide, then the methanol carbonylation reaction rate and the selectivity for acetic acid were enhanced .⑤The experimental results showed that when the molal ratio of iridium, ruthenium and lithium was 1:5:1, a higher rate of methanol carbonylation reaction was achieved and the space-time yield of acetic acid was 25.6 mol/(L.h) ; besides, the conversion rate of methanol was up to 99.8%, the selectivity for acetic acid was 88% and the carbonylation rate was 88%.⑥The ionic liquid of [Bmim] I was synthesized by microwave radiation, and the structure was characterized by the nuclear magnetic resonance (NMR). The results indicated that the purity of ionic liquid was better, which was good for catalytic reactions. The conversion rate of methanol increased with the increase of ionic liquid content, and the process of catalysis was good for preparing methyl acetate. The selectivity for methyl acetate was remained between 55% and 75% in the iridium -ruthenium catalyst system by the catalysis repeatedly, which tend to be promoted.⑦The methanol carbonylation was carried out for the metal complexes of imidazole, and the results indicated that the catalytic activity of nickel were improved by imidazole ligand to some extent.