Research On High-value Utilization Of Biomass Pyrolytic Carbon

In view of the present energy situation of"lean oil"in China,it is an inevitable trend to vigorously develop the fast/flash pyrolysis technology of biomass,and the by-product of pyrolytic carbon is also needed to be fully utilized,which will be of great significance to improve the overall utilization efficiency and environmental sustainability of biomass resources.Therefore,the methods of high-value utilization of biomass pyrolytic carbon were studied in this paper.Firstly,a new method of high-value conversion and utilization of pyrolytic carbon was explored.A bio-mesoporous material was prepared directly after the extraction of silica from pyrolytic carbon using a sequential stepwise method,in which pyrolytic carbon was obtained as the by-product from the pyrolysis of rice husk.This mesoporous material?designated Bio-MCM-41?had a high BET surface area of 782 m²/g.At the same time,the alkali-rich char residue was activated directly to obtain activated carbon?AC?with a BET surface area of 442m²/g,and microporous and mesoporous structures coexisted in it.To test the feasibility of Bio-MCM-41 as a catalyst support,Bio-MCM-41-supported Cu-based catalyst?Cu/Bio-MCM-41?was prepared for use in the hydrogenation of methyl acetate?MA?for ethanol production.The probe reaction test of MA hydrogenation showed that the Cu/Bio-MCM-41 catalyst had superior or comparable catalytic performance to a similar catalyst?Cu/Com-MCM-41?prepared from commercial Mobil composition of matter 41?MCM-41?.A high MA conversion of 91.5%with an ethanol selectivity of 96.4%was achieved under the optimum reaction conditions(513K,2 MPa,n?H₂?/n?MA?=60,liquid hourly space velocity=0.8 h^-1).Then the structure and surface properties of pyrolytic carbon were modified by nitrogen doping.In this part,N-doped carbons with a high nitrogen content and tuned pore structure were obtained from biomass?Pinus sylvestris?by an in-situ pyrolysis process with simultaneous doping nitrogen and activation using urea as a nitrogen precursor and NaHCO₃ as the activator.To test the feasibility of N-doped carbon as a catalyst support,N-doped carbon-supported Ru-based catalyst?Ru/N-ABC-x?was prepared for use in the CO₂ methanation.The probe reaction test of CO₂ methanation showed that the catalytic activity can be improved by introducing nitrogen atom into the support,especially with the increase of pyridinic-N content,the performance of the catalyst is improved to a certain extent.The Ru/N-ABC-600 catalyst with the highest pyridinic-N?37.7%? content achieved the best catalytic activity at a lower temperature?380°C?,and the CO₂ conversion was 93.8%,CH₄ selectivity was 85.2%.Moreover,nitrogen-enriched carbons were prepared from biomass with a high nitrogen content,whose surface and internal structures were all uniformly nitrogen-doped.More specifically,a microalga with a high nitrogen content,namely Spirulina platensis,was used as both the carbon and nitrogen precursors in the synthesis of sponge-like nitrogen-enriched carbons via a one-step activation method with NaHCO₃ as a green activator.A series of tests were performed to investigate the electrochemical characteristics of the obtained carbons to determine their potential use as supercapacitors.The results show that sponge-like nitrogen-enriched carbon activated at 700°C,which has a large BET surface area of 865 m²/g and a high nitrogen content of 7.5 wt%,gave the largest specific capacitance of 234.0 F/g at a current density of 1 A/g in a 6M KOH electrolyte.