Enhanced Transfer And In Situ Catalytic Pyrolysis Of Biomass By Using Hydrate Molten Salt

Facing the global energy crisis and environmental pollution,it was urgent to find new green,renewable and clean energy.As the only carbon-based renewable energy in the world,biomass energy had the advantages of large production and wide distribution.Biomass catalytic pyrolysis technology was an important way for biomass conversion and utilization.Its main product,bio-oil,was an excellent alternative energy source for fossil energy and had broad development prospects.However,at present,most of the catalytic processes of biomass catalytic pyrolysis technology were non in-situ catalysis,which had weak catalytic effect on biomass.Moreover,the high synthesis cost and easy coking of the catalyst seriously hindered the development of this technology.The hydrate molten salt had good dissolution and swelling ability to the biomass,and could penetrate into the biomass uniformly.Moreover,it had a certain acidity and alkalinity,which could realize the catalytic pyrolysis of biomass in situ.Based on this,a method of fast pyrolysis of biomass catalyzed by hydrate molten salt in situ was proposed in this paper.This method took advantage of the characteristics of hydrate molten salt to realize the in-situ catalysis of biomass itself,thereby improving biological quality and reducing the complexity of bio-oil components.Firstly,in order to investigate the effect of hydrate molten salt on the pyrolysis of pine（PW）,the influence of hydrate molten salt cation and anion change on the catalytic pyrolysis process of PW was compared.The results of thermogravimetric（TGA）showed that the pyrolysis temperature of the biomass was significantly reduced by the in situ catalytic pyrolysis of the hydrate molten salt,and the degree of reduction depended on the overall acidity and alkalinity of the hydrate molten salt.The maximum weight loss temperature of pine loaded with 5.6 wt%Fe Cl₃ hydrate molten salt decreased by about 100 ^oC.In addition,the kinetic and thermodynamic results show that the activation energy,enthalpy change and entropy change could be significantly reduced by acidic hydrate molten salt,while the alkaline and neutral hydrate molten salt had little effect on them.The activation energy,enthalpy change and entropy change of pine pyrolysis catalyzed by Fe Cl₃,which was more acidic,were 54.33 k J/mol,56.58 k J/mol and-196.8 J/（mol·K）,respectively.The results of Gas chromatography-Mass spectrometry（GC-MS）showed that the hydrate molten salt had a great influence on the composition of bio-oil.The acidic hydrate molten salt could significantly promoted the production of furans in bio-oil,and the relative content of furans in bio-oil was up to 35%,while the alkaline hydrate molten salt could increase the content of acids in bio-oil,and the relative content was up to 20.73%.On this basis,the Zn Cl₂ hydrated molten salt was selected as the catalyst to explore the feasibility of in-situ catalytic synthesis of bio-oil from biomass under mild conditions,and its specific catalytic process was studied.The application of pyrolysis solid residue was further explored through adsorption experiments on phenol containing wastewater.The results of TGA and pyrolysis experiments indicated that in-situ catalysis of Zn Cl₂ hydrate molten salt could significantly reduce the pyrolysis temperature of cellulose in biomass.At350°C,Zn Cl₂ hydrate molten salt could catalyze the pyrolysis of PW to obtain 47 wt%bio oil yield,which is 84.31%higher than non-catalytic pyrolysis.The results of kinetic and thermodynamic fitting showed that the activation energy and enthalpy-change of cellulose pyrolysis were significantly reduced by Zn Cl₂ hydrate molten salt（activation energy decreased from 304.8 k J/mol to 112.5 k J/mol;enthalpy change from 298.05 k J/mol to 112.29k J/mol）,but had little effect on lignin pyrolysis.The results of GC-MS showed that the Zn Cl₂hydrate molten salt simplified the composition of bio-oil and significantly increased the furfural content in bio-oil.The furfural content in bio-oil catalyzed by 5 wt%Zn Cl₂ hydrate molten salt reached 34.5%at 350 ^oC.After the pyrolysis carbon slag was further doped with Zn Cl₂ hydrate molten salt and re-carbonized at 600 ^oC,the activated carbon with good performance could be obtained,and the phenol adsorption capacity could reach 165 mg/g.This study could provide guidance and reference for the development of efficient in situ catalytic pyrolysis technology for biomass.