Study On Liquid-Liquid Equilibria And CaO-based Catalyst For Sythesis Of Glycerol Carbonate

Glycerol carbonate, a green chemical, is a kind of organic chemical raw materialswidely used. It is mainly used as reaction intermediates and solvents, or reacts withisocyanate, acrylic ester products and product polymer to use in coating, adhesive andlubricant and so on. this dissertation is based on the transesterification of DMC andmethanol to produce Glycerol carbonate, and mainly focused on the research forthermodynamics and catalysts aboat this system to lay the foundation for the developmentof subsequent synthesis process of glycerol carbonate.Liquid–liquid equilibria (LLE) data of the ternary system dimethyl carbonate+methanol+glycerol were measured from303.15K to333.15K. The equilibrium data arecorrelated with the NRTL and UNIQUAC model. The reliability of this model is tested bycomparison with the experimental results. On the other hand, LLE and vapor–liquidequilibria (VLE) of the binary system dimethyl carbonate+glycerol were also measuredunder isopiestic pressure (101.3kPa) and predicted using the NRTL model, with theadjusted parameters obtained from the LLE data of the ternary system dimethyl carbonate+methanol+glycerol. The predicted VLE and LLE for the binary system agreed wellwith the experimental data.The extruded CaO-based catalysts were prepared and used for the synthesis of glycerolcarbonate from glycerol and dimethyl carbonate. The effects of binders (diatomite, kaolin,and activated alumina), pore-forming agents (polyacrylamide, activated carbon, andpolyethylene glycol), and calcination temperatures (700oC,800oC, and900oC) on thecatalytic activity and stability of the catalyst were investigated. XRD, FT-IR, BET, andSEM were used for the characterization of the prepared catalyst. It was found that theinitial activity of the fresh extruded CaO-based catalyst is lower than the CaO powder catalyst because of the resistance of the internal diffusion; however, the stability of theformer was far better than the latter. Using activated alumina as the binder andpolyacrylamide as the pore-forming agent, under the3:1of CaO/binder mass ratio,800oCof calcination temperature, and80oC of reaction temperature, the glycerol conversion andglycerol carbonate yield could reach95.39%and90.57%for the fresh catalyst and65.47%and62.53%for the recovered catalyst at the fifth recycling, respectively. Theextruded catalyst also had a certain water-resistance performance. The catalystcharacterization showed that the active site of the prepared catalysts is CaO. The extrudedcatalyst had high BET surface area, high pore volume, and large pore diameter; and itsmechanical strength was also suitable for the industrial reactor.