(621j) Kinetics of Transesterification of Propylene Carbonate to Dimethyl Carbonate

<align="center">Kinetics of Transesterification of Propylene Carbonate to Dimethyl Carbonate

Ziwei Song, Xin Jin, Bala Subramaniam, Raghunath V. Chaudhari,  

Center for Environmentally Beneficial Catalysis, Chemical & Petroleum Engineering,

University of Kansas, Lawrence, KS 66047, USA

Along with increasing concern on environmental friendly and sustainable development, “green chemistry” and “green chemical engineering” aspects are receiving increasing attention in development of new processes. Dimethyl carbonate (DMC) has been categorized as one of the “green chemicals” because of its non-toxicity, biodegradability and a key intermediate to replace phosgene for the synthesis of polycarbonates and urethanes. DMC now is manufactured by oxidative carbonylation of methanol using a homogeneous Cu catalyst at high pressure conditions but direct synthesis by transesterification of organic carbonates, derived from CO₂ is a significant recent development. Transesterification of organic carbonates is a equilibrium limited reaction catalyzed by basic catalysts such as hydrotalcite, MgO and several other forms of heterogeneous catalysts at high temperatures (90-170^oC). CaO based catalysts offer high selectivity to DMC at low temperatures but the mechanism of the reaction and nature of active catalytic species are not well understood. The kinetics of transesterification of PC using CaO catalyst, which is useful for design of suitable reactors is also not well understood from previous work.

In this presentation, results on activity and selectivity of several heterogeneous catalysts will be discussed. CaO showed better performance compared to other catalysts consisting of basic metal oxides. With CaO catalyst in a slurry reactor, an induction period was observed for the transesterification reaction. In this context, the effect of catalyst pretreatment with substrates and products was investigated and it was observed that while pretreatment with propylene carbonate (PC) inhibited the transesterification rates, pretreatment with methanol led to significant irreversible enhancement of catalytic activity. Further, effect of reactant concentrations, CaO loading on the rate and concentration-time profiles was investigated for 20-60^oC, with the goal of developing rate equations and estimate intrinsic kinetic parameters. The experimental rate data were used to develop Langmuir-Hinshelwood type of rate models and the details of model discrimination and parameters estimation will be discussed.