Study On Microwave Assisted Heterogeneous Catalytic Synthesis Technology Of Lactide

As the exhaustion of oil resources, and the environmental problems caused by petroleum based plastics, searching for substitute of petroleum resources is the current hot research in the field of plastic production. PLA is a kind of bio-surfactant fully-degradable plastic, which has rich resources of raw materials and green degradation process, the use of PLA is beneficial to achieve the virtuous cycle of environment system, and it is an effective way to alleviate the oil crisis and eliminate the "white pollution".To realize the large-scale production and application of PLA, we investigated the microwave-assisted modification of MMT and synthesis of lactide, in order to develop a environment-friendly synthesis technologyof lactide with high productivity and low energy consumption.Acid MMT (H-MMT) was prepared by activating Na-MMT with acid under microwave irradiation, and then the technological conditions of preparing H-MMT was investigated systematically. The structure and characters of H-MMT were studied by the use of XRD,BET,TG,NH₃-TPD, The results revealed that acid activation did not affect the layer structure, the surface area and pore volume was larger, and the acid amount was increased. Thus, the acidity and catalytic activity (tested in terms of ester yield of n-butyl lactate) were significantly improved.By using H-MMT as catalyst supporters, environmentally friendly SnO/HMMT solid catalyst was prepared through impregnation-evaporation method. The structure and characters of SnO/HMMT were studied by the use of XRD,XPS,TG,NH₃-TPD, the results revealed that there is a chemical reaction between MMT supporter and SnCl₂, the existing form of Sn was SnO, the mechanical and thermal properties of catalyst were very stable within 200℃. meanwhile, the racid center and acid amount was significantly improved. SnO/HMMT has both the active centers of catalyzing polycondensation and depolymerization, thus, it exhibits highly catalytic activity in synthesis of lactide.Using SnO/HMMT as catalyst,microwave irradiation as heating method,the technological conditions of was systematically investigated. And then, methods of product purification were discussed. The results showed that the crude productivity was 90%,the pure productivity was 42.9%. Microwave assisted heterogeneous catalytic synthesis of lactide was a environment-friendly technology with high productivity and low energy consumption.