Study On The Zirconia Catalyst For The Synthesis Of Methyl N-Pheyl Carbamate

Methyl N-phenyl carbamate (MPC) is an important precursor for preparing methylene diphenyl diisocyanate (MDI), which is an important intermediate for the synthesis of polyurethane. At present, a new route for the synthesis of MPC from aniline and DMC is proposed. The following research work concerning the catalysts and the process of MPC synthesis from DMC and aniline has been systematically done in this thesis.The reversed-phase high performance liquid chromatographic method for the products from the reaction is described. The products are well separated through Kromasil (TM)^C₁₈. The quantitative analysis is carried out by internal standard method and nitrobenzene is used as internal standard. The good linear relationship of the injected amount of the products verse the peak height is observed.Nano-sized ZrO₂ powders were prepared by sol-gel process using water as solvent, the influence of preparation conditions on crystal and particle size of ZrO₂ have been investigated. Improving the reaction time and acetic acid concentration, reducing ZrOCl₂ concentration were good for the production of tetragonal ZrO₂;decreasing reaction time and n(Urea)/n(ZrOCl₂), increasing acetic acid concentration were good for the growing up of particle size of ZrO₂.From associate the crystal, particle size and catalytic activity of ZrO₂, we found that small particle size, high content of tetragonal ZrO₂ has better catalytic activity, and main product MPC has higher selectivity. The highest aniline conversion is 43.2% and the highest yield of MPC is 9.2% at the following reaction conditions: reaction temperature, 443.15K;reaction time, 7h;n(DMC)/n(Aniline)=20;Amount of catalyst was 1.4g/100mlDMC;For the low specific surface area, we use incipient impregnation process to improve the catalytic activity of ZrO₂. SiO₂ was screened out as the best support. It was found that basic support was not good for the reaction and weakly acidic support exhibited better catalytic activity. The optimal preparation conditions for ZrO₂/SiO₂ catalyst were exploited as follows: loading amount of ZrO₂, 1.0%(wt), calcination temperature, 573.15K, calcination time, 2h.The optimal reaction condition for ZrO₂/SiO₂ are as follows: reaction temperature,443.15K;reaction time, 7h;n(DMC)/n(Aniline)=20;Amount of catalyst was 1.4g/100mlDMC, and the highest yield of MPC is 79.8%, the highest conversion of aniline is 98.6%. The analysis of BET surface area for the catalyst used both before and after reaction shows that blocking of the channels by bulkier molecules from raw materials and products is the reason for deactivation.