On the basis of thermodynamic analysis for the synthesis of propylene carbonate from urea and 1,2-propylene glycol (PG), the catalytic properties of zinc acetate have been studied. The optimal reaction conditions are as follows: molar ratio of urea to PG, 2:8; reaction time, 3 h; reaction temperature, 170 °C; molar ratio of zinc acetate to PG, 1:148. The highest yield of propylene carbonate is 94%. Then the immobilization of zinc acetate is investigated in order to facilitate recovery and reuse of the catalyst. The suitable support is activated carbon, and the optimal load of zinc acetate is 15 wt %; the highest yield of propylene carbonate is 78%. The analysis of X-ray photoelectron spectroscopy, X-ray diffraction, Brunauer-Emmett-Teller surface area analysis, and atomic absorption spectroscopy for the catalysts used both before and after reaction shows that both some changes and severe loss of zinc acetate have taken place during the process of the reaction.

No abstract

A reaction integration of aldol condensation–hydrogenation for the direct synthesis of 2-ethylhexanol from n-butanal was realized.

The catalytic synthesis of methylene diphenyl-4,4′-diisocyanate (MDI) consists of three steps. Starting from the catalytic reaction of aniline and dimethyl carbonate (DMC), methyl phenyl carbamate (MPC) is formed. Then MPC condenses with formaldehyde to produce dimethyl methylene diphenyl-4,4′-dicarbamate (MDC). Last, MDC is decomposed to MDI. For the first step, the properties of supported zinc acetate catalysts on different supports have been examined. Supported zinc acetate catalyst on activated carbon (AC) or R-Al 2 O 3 shows good catalytic properties. Over Zn(OAc) 2 /AC catalyst, MPC yield reaches 78% and the selectivity is 98%. For the second step, when zinc chloride is used as a catalyst and nitrobenzene as a solvent, MDC yield can reach 87.4%. The catalytic activity of AC-supported ZnCl 2 catalyst, which is calculated based on 1 mol of ZnCl 2 , is much higher than that of homogeneous ZnCl 2 . For the third step, zinc powder and its organic salts show higher catalytic activity; MDI yield is 87.3% over zinc powder catalyst.