Study On The Preparation Of Bio-Oil By Catalytic Co-Pyrolysis Of Rice Oil Clay And Food Packaging Soft Plastic

The cereal and oil food industry is an important part of China’s grain and oil food industry,which can strongly guarantee the major material needs of the national healthy life.In the production process of fats and oils,white clay is used as decolorization adsorbent.Therefore,a large amount of spent bleaching clay will be generated.The oil content of spent bleaching clay is 20%-40%,which is usually discarded or landfilled to cause environmental pollution and has not been fully and reasonably exploited.By pyrolysis,grease is heated to high temperatures to produce liquid and gaseous products,which can be used as chemical raw materials.However,the products of grease pyrolysis may have a large number of oxide-containing and other unstable substances,these substances lead to a decrease in the stability of the product,its storage and use are subject to certain restrictions.Food packaging plastics are an integral part of modern society,and their large use has led to environmental problems.The use of pyrolysis of waste plastics can also transform them into products with high added value.However,the pyrolysis of plastics has the problem of poor thermal conductivity.Spent bleaching clay has microwave absorption properties,and pyrolysis in a microwave field can provide heat energy for plastics,thus solving the problem of low heat transfer rate of plastics.Therefore,this study uses microwave copyrolysis to overcome the shortcomings of spent bleaching clay and waste plastic pyrolysis to prepare bio-oil rich in monocyclic aromatic hydrocarbons,which not only helps to protect the environment and save resources but also brings economic benefits.The main work and conclusions are as follows:(1)The synergistic effect of co-pyrolysis between spent bleaching clay and LDPE was investigated by thermogravimetric experiments.And the best conditions were obtained by analyzing the TG and DTG curves and kinetics under different raw material ratio conditions and applied to Py-GC/MS pyrolysis experiments.The synergistic effect of co-pyrolysis of spent bleaching clay with LDPE was verified by thermogravimetric experiments and GC/MS results together.The results showed that the same pyrolysis temperature interval existed between SBC and LDPE,while co-pyrolysis promoted the degree of degradation.For the pyrolysis products,the co-pyrolysis of SBC and LDPE has a synergistic effect to increase the yield of the target product monocyclic aromatic hydrocarbons as well as to decrease the yield of oxygenated compounds.(2)Guided by the data in(1),a suitable pyrolysis temperature interval was selected for microwave pyrolysis experiments,and the effects of different pyrolysis temperatures,catalytic temperatures,feedstock ratios,and catalytic amounts,on the product distribution and liquid product composition were investigated.The optimum pyrolysis conditions were found to be 550 °C for pyrolysis and 450 °C for catalysis,at SBC/LDPE=40:28.5 and catalytic amount=7g.The results showed that after optimizing the microwave pyrolysis conditions,the yield of monocyclic aromatic hydrocarbons reached 69.89%,which is higher than that of 53.90% without optimization.The yield of polycyclic aromatic hydrocarbons reached 15.48%,which is lower than that of 23.21% without optimization,and the yield of oxygen-laden compounds was 2.83% lower than that of 5.56% without optimization.(3)The pyrolysis products of different plastics(LDPE,PP,PS,and mixed plastics)with SBC were initially predicted by Py-GC/MS for their co-pyrolysis synergy.And then combined with the optimal pyrolysis conditions for microwave experiments in(2).The effects of electric heating and conventional heating on the products were compared to verify the microwave absorption characteristics of SBC,and the synergistic effects of co-pyrolysis between mixed plastics and SBC under different heating methods were discussed in detail.The results showed that the product components obtained by co-pyrolysis of different types of plastics were different,and the co-pyrolysis of mixed plastics with SBC further promoted the yield of monocyclic aromatic hydrocarbons.Compared with conventional electric heating,the non-thermal effect of microwave pyrolysis increased the yield of monocyclic aromatic hydrocarbons from 53.64% to 71.11%,and the yield of oxygenated compounds decreased from 6.08% to 0.84% for the co-pyrolysis of mixed plastics with SBC.