In-situ Catalytic Upgrading Of Rape Straw Pyrolysis Vapors For Refined Bio-oil Over MCM-41 And HZSM-5

Energy is the basis for development of modern society,reasonable and effective development of clean renewable energy has a great significance to alleviating China's worsening energy and environmental crisis.Biomass has been considered as the only renewable carbon resources that can produce liquid fuel and the catalytic pyrolysis of biomass vapors is the main methods to upgrading bio-oil.In this paper,a series of basic problems in the process of producing bio-oil in the two-stage fixed-bed reactor were studied.During the experiment,the most common agricultural and forestry residues of rapeseed straw were used as biomass materials,the HZSM-5 and MCM-41 molecular sieve were used as catalysts.The specific research works are as follows:(1)The experimental study on the catalytic upgrading of rape straw with MCM-41 catalyst in the two-stage fixed-bed reactor was conducted.The effects of catalyzing temperature,catalyzing bed height and system pressure on the yield of refined organic phase were investigated.Orthogonal method and response surface methodology were employed to optimize the catalytic upgrading process.The results showed that the influence of catalyzing temperature,catalyzing bed height and system pressure on the yield of organic phase was great,besides,there was a significant interaction between catalyzing temperature and system pressure.The results of orthogonal experiment showed that 15.57% of organic phase yield was obtained at catalyzing temperature of 500?,catalyzing bed height of 2.5cm and system pressure of 5kPa.The results of response surface methodology showed that 15.84% of organic phase yield was obtained at catalyzing temperature of 502?,catalyzing bed height of 2.7cm and system pressure of 7kPa.(2)The refined organic phase was prepared via in-situ catalytic cracking of biomass pyrolysis vapors using MCM-41 zeolite at the optimum organic phase yield condition,the physicochemical properties and molecular compositions of refined organic phase were analyzed.Catalysts and organic phase were obtained at different using time,and the quality of organic phase and weight-loss rate of catalysts were analyzed to explore the durability of catalysts.The results showed that the aromatic substances content in organic phase was 58.45%,and there are mainly phenolic compounds which accounts for 64.69%,and aliphatic hydrocarbons accounts for 16.53%;The difference of weight-loss of organic phase between inert and oxidizing atmosphere was obvious,while organic phase had a better burnout effect in the air atmosphere and the final ash residue was only 0.37%.With the prolongation of catalyst using time after 100 min,the quality of organic phase has gradually deteriorated and the activity of catalyst has decreased.(3)The catalyst was arranged in two different schemes(HZSM-5/MCM-41 and MCM-41/HZSM-5)to make respective comparison with MCM-41 and HZSM-5 catalytic alone and the refined organic phase obtained from four different catalyzing methods were analyzed.The results showed that when compared with single catalysis,the yield of liquid phase obtained from synergistic catalysis was slightly lower and the yield of gas phase was higher.Many aromatic hydrocarbons were generated through synergetic catalytic and the oxygen-contained aromatic substances in organic phase have decreased.The synergistic catalysis of MCM-41/HZSM-5 obtained highest hydrocarbon content and the hydrocarbons were mainly monocyclic aromatic hydrocarbons,while the content of C6~C9 hydrocarbons was the highest.(4)The catalysts of single catalysis(MCM-41 and HZSM-5)and synergistic catalysis(HZSM-5/MCM-41 and MCM-41/HZSM-5)have been used to continuously on-line catalyzing the biomass pyrolysis vapors for 200 min and the thermogravimetric analysis of each deactivated catalyst samples was performed at air atmosphere.The results showed that there were two weight-loss intervals of HZSM-5 zeolite at the range of 300?~800?,which indicated that the coke deposited on the HZSM-5 catalyst contained both fibrous amorphous coke and graphite-like coke.There was only one weight-loss interval of MCM-41 zeolite at the range of 300?~800?,which indicated that the coke deposited on the MCM-41 catalyst was fibrous amorphous coke.