Study On The PdCl₂-CuCl₂/Li-Al-O Catalyst For The Synthesis Of Dimethyl Carbonate From Carbon Monoxide And Methyl Nitrite

Dimethyl carbonate is one of the very promising green chemicals as solvents, andphosgene substitute and gasoline additive. It also has broad application prospects,involved in methylation and carbonylation reaction, and the ability to synthesize theextensive used polycarbonateester plastics. Synthesis of DMC by CO and Methylnitrite （MN） is a promising synthetic method. In this paper, a systematic study wascarried out on the preparation and its influencing factors about lithium aluminumspinel support of the Wacker-type catalyst.From the characterization results of the Powder X-ray diffraction, framework IRand SEM, the specific surface of support, the content of lithium aluminum spinel andcrystallinity had a large impact on the catalytic activity. The higher calcinationtemperature would lead to lithium aluminum primitive cubic crystal and low specificsurface. And the lower temperature would also affect the crystallinity of the spinel.The influence of Li content on the support structure was investigated in theceramic method process. There were only alumina and lithium aluminum spinel whenthe Li/Al（molar） ratio was lower than0.15. With the increase of content of LiAl5O8,the catalytic activity was improved. When the Li/Al was above0.15, the crystallinephase of LiAlO₂appeared and increased signally, and the catalystic activity alsodeclined. The lithium aluminum spinel had the strongest electron transport capacity topromote the electron transfer between Pd and Cu. Furthermore, the activities ofcatalysts increased. γ-Al₂O₃and LiAlO₂can not improve the electron transport, andappearance of LiAlO₂would also decline the specific surface. All above were notfavorable for the distribution of Pd2+and Cu2+, and affected the reaction.HCl gas was used in the Wacker-type catalyst system to supplement the loss ofchlorine in the reaction, and at the reaction gases ratio CO: MN=5:15（Vol%） gave abetter space-time yield and stability. Compare the different lithium aluminum spinelpreparation methods, the support prepared at the situations of800oC calcinationtemperature and0.15Li/Al ratio had much LiAl5O8spinel which was beneficial forthe reaction. And this catalyst showed the best activity and selectivity of DMC.