Research On The Selective Production Of Chemicals By Catalytic Pyrolysis From Biomass

With the depletion of fossil,biomass has caused the attentions of many researchers as the unique substance which can realize carbon circulation.The technology of selective preparation of the model compound by biomass catalytic pyrolysis can convert biomass into resources,which is widely concerned.Firstly,model chemicals are selectively obtained through catalytic pyrolysis,and then by coupling or condensation of these chemicals to acquire proper carbon-chain compound and at last get fuel by hydrodeoxygenation.High selectively obtaining chemicals from biomass catalytic pyrolysis is the key problem in this route.Hence,we conduct researches in model chemicals seletively including furfural,2,3-dihydrobenzofuran and aromatic compounds.The main research contents and results are as follows:1 Lewis acid ionic liquids could realize biomass pretreatment and catalytic process at the same time.The selectivity of furfural and 2,3-dihydrobenzofuran of pyrolysis oil by bagasse catalytic pyrolysis with Lewis-acid ionic liquids was significantly improved.The difference of metal salts of Lewis-acid ionic liquids could affect the acid strength of ionic liquid and impact the selectivity of furfural and2,3-dihydrobenzofuran.When the strength of Lewis-acid reached a certain value,which could improve the selectivity of furfural.On the contrary,under the condition of weak acid,it could effectively improve the selectivity of 2,3-dihydrobenzofuran.When the content of[BMIM]Cl/ZnCl₂ reached 2 mmol and the molar ratio of ZnCl₂to[BMIM]Cl/ZnCl₂ was 0.67,the selectivity of furfural was high up to 23.92 wt%,but with only 2.35 wt%2,3-dihydrobenzofuran.And when the molar ratio of ZnCl₂ of[BMIM]Cl/ZnCl₂ was 0.55,the 2,3-dihydrobenzofuran had the seletivety of 15.38wt%,but with only 4.12 wt%furfural.2 Under the pretreatment of Br?nst-Lewis acid ionic liquids,the selectivity of furfural of biomass pyrolysis oil could be improved obviously than the single Lewis-acid ionic liquids,which could also reduce the pyrolysis temperature of biomass.In this paper,four different Bronst-Lewis ionic liquids were investigated,including[n-Bu₃P⁺?CH₂?₄-HO₃S]Cl/ZnCl₂,[HO₃S-?CH₂?₄-NEt₃]Cl/ZnCl₂,[HO₃S-?CH₂?₄-Py]Cl/ZnCl₂,[HO₃S-?CH₂?₄-MIM]Cl/ZnCl₂.When the content of[HO₃S-?CH₂?₄-MIM]Cl/ZnCl₂ reached 0.3 mmol,and the molar ratio of[HO₃S-?CH₂?₄-MIM]Cl to ZnCl₂ was 1:2,the furfural selectivity achieved 29.04 wt%,and the pyrolysis temperature of bagasse was also reduced from 310??without catalysts?to 235?.3 The difference of aromatic selectivity between HZSM-5 zeolite with different SiO₂/Al₂O₃ was also obvious.HZSM-5?38?zeolite had the best catalytic effect on aromatic compounds,including phenol,methylphenol,catechol,2,3-dihydrobenzofuran and 2,6-dimethoxyphenol.Moreover,the addition of Pt could effectively improve the selectivity of aromatic compounds,and catalytic performance of Pt/HZSM-5 could also be influenced by its preparation methods.The catalytic effect of Pt/HZSM-5 prepared by ion exchange method which was superior to the impregnation method.With the catalyst of Pt/HZSM-5?38?iex,the total selectivity of the six aromatic compounds was up to 86.3 wt%,while the 2,3-dihydrobenzofuran selectivity was as high as 43.5 wt%.