Catalytic Conversion Of Organic Volatiles To Syngas And Functional Carbon Materials During The Fast Pyrolysis Of Biomass

Biomass resources have the advantages of large reserves,renewable,and diversified utilization methods,and are ideal substitutes for fossil energy.At present,the methods for value-added utilization of biomass generally have the disadvantages of complicated processes,harsh reaction conditions,low yield of high value-added products,and poor selectivity,which greatly limit the large-scale utilization of biomass resources.Therefore,it is of great significance to develop new efficiently value-added utilization methods of biomass.On the other hand,many solid wastes or pollution systems generated by human activities have the similar thermochemical characteristics to those of biomass.By referring to the thermochemical treatment of biomass,efficient treatment and simultaneous utilization of these pollutants will bring important economic and environmental implications.In order to explore the new biomass utilization strategy,we conducted in-situ catalytic conversion of organic volatiles generated during the fast pyrolysis of biomass.By selecting suitable catalysts,the hydrogen atoms therein are efficiently converted into hydrogen meanwhile the oxygen atoms are converted into CO,and the formation of carbon deposits is regulated,thereby converting the biomass into syngas and functional biochar in one step.In addition,we explored the application performance of functional carbon materials in the field of environmental remediation,and extended this utilization to petroleum-contaminated soil systems with similar pyrolysis characteristics to biomass.The research contents and results of this thesis are as follows:1.Conventional conversion of biomass to syngas typically requires firstly obtaining bio-oil and then adding reforming reagents for catalytic reforming.In this study,Ni/Al layered double hydroxides(Ni/Al-LDHs)were used as precursor to prepare nickel-based catalyst with high specific surface and high Ni dispersion.The secondary catalytic cracking of organic volatile products produced in the process of fast pyrolysis of biomass was achieved without adding any additional reforming reagents.Under the catalysis of Ni/Al,the conversion selectivity of hydrogen atoms reaches 86.88%.In order to make full use of the O in the biomass volatiles to reduce carbon deposition and control its form,we introduced Mg into the LDH precursor to optimize the catalyst.The addition of Mg increases the basic sites in the catalyst,improves the affinity for CO2 in the pyrolysis system,and enables that the CO2 produced by biomass pyrolysis can in-situ participate in the catalytic reforming reactions of organic volatiles,increasing the yield and selectivity of syngas and reducing the carbon deposition.Moreover,by controlling the addition ratio of Mg,the form of carbon deposition is regulated to be present in the form of whisker carbon as much as possible,which reduces the coverage of active sites by carbon deposits.This study provides a new strategy for the conversion of biomass to syngas and the control of carbon deposition.2.Based on the above understanding,we used the carbon deposition generated in the catalytic pyrolysis process to modify the biochar,synthesizing functional carbon materials.FeCl3 is pre-loaded on biomass as a catalyst,by catalyzing the chemical vapor deposition of organic volatiles generated during the pyrolysis of biomass,a new hydrophobic carbon film containing less polar atoms was formed on the biochar surface.Meanwhile,abundant pores were produced in the biochar through the catalytic pore-forming effect of FeCl3 towards biomass,which increased the surface roughness.The combination of hydrophobicity and high roughness results in a superhydrophobic biochar material.The superhydrophobic biochar material exhibited excellent environmental stability and the method has good universality for different biomass wastes.The superhydrophobic biochar material has excellent performance in oil/water separation and self-cleaning surface.The key factor affecting the wetting properties of bio-carbon was investigated and proven to be the ash in biomass.Based on this result,we washed out the ash in maize straw and load FeCl3 by impregnating in the FeCl3 solution.During the pyrolysis process,the polar sites in biochar are covered by chemical vapor deposition of organic volatiles to obtain a highly hydrophobic magnetic carbon aerogel.The carbon aerogel has good oil/water selectivity and high oil absorption capacity,can absorb various oils and organic solvents from the surface of the water body with good recycling performance.This study not only prepared new functional carbon materials,but also expanded the application ranges of biochar,and provided new ideas for the control and utilization of carbon deposition in biomass thermal catalytic conversion.3.Considering the thermochemical behavior of petroleum is similar to that of biomass,we extended the above thermochemical treatment of biomass to the treatment of petroleum-contaminated soil(PCS).Fast pyrolysis technology was implemented to remedy PCS and concurrently recover the oil,and the residual carbon produced in the pyrolysis process was used to improve the water retention performance of the soil.The remediation effect related to pyrolytic parameters,the recovery rate of oil and its possible formation pathway,the physicochemical properties of the remediated PCS,and its suitability for planting were systematically investigated.Both extractable total petroleum hydrocarbons and water soluble organic matters in PCS were completely removed at 500 ? within 30 min.The remaining carbon in remediated PCS was determined to be in a stable and innocuous state,which has no adverse effect on wheat growth.Because the residual carbon has less polar functional groups,the soil is hydrophobic and has excellent soil water retention performance,which is beneficial to the treatment of desertified soil.