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.

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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.

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Self-condensation of n-butyraldehyde to 2-ethyl-2-hexenal is one of the important processes for the industrial production of 2-ethylhexanol. In the present work, several sulfonic acid functionalized ionic liquids (SFILs) were synthesized. Their acid strengths were determined by the Hammett method combined with UV–vis spectroscopy, and their catalytic performances in n-butyraldehyde self-condensation were investigated. The results show that the conversion of n-butyraldehyde correlated well with the acid strength of the SFILs with the same cation. The SFILs with triethylammonium cations showed a better catalytic performance than those with imidazolium cations or pyridinium cations, and [HSO3-b-N­(Et)3]p-TSA (“b”, butyl) exhibited the highest selectivity. Under the optimal reaction conditions of the mass ratio of [HSO3-b-N­(Et)3]p-TSA to n-butyraldehyde = 0.1, reaction temperature = 393 K, and reaction time = 6 h, the conversion of n-butyraldehyde was 89.7% and the selectivity to 2-ethyl-2-hexenal was 87.8%. [HSO3-b-N­(Et)3]p-TSA could be reused four times without a significant loss in its catalytic performance. A kinetic analysis result showed that this is a reversible second-order reaction. Compared with the kinetic parameters from the reaction catalyzed by an aqueous base or acid catalyst, the pre-exponential factor is lower due to the restriction of the high viscosity of [HSO3-b-N­(Et)3]p-TSA. Finally, a possible reaction mechanism for n-butyraldehyde self-condensation catalyzed by [HSO3-b-N­(Et)3]p-TSA was proposed.

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