Study On Porous Carbon Solid Acid Prepared By Phosphoric Acid Activation And Applied To Cellulose Conversion

The rational development and utilization of renewable resources based on cellulose is a powerful mean to achieve sustainable development for people.Biomass carbon-based solid acid is widely used in cellulose conversion for its advantages,like low cost and easy availability,abundant surface functional groups and environmental friendly.However,traditional biomass carbon-based solid acids still have natural defects in the aspects of dense lamellar structure,acid stability,acid accessibility,and mass transfer efficiency.To solve the above defects of carbon-based solid acid,the preparation and characterization of phosphorus-containing porous biomass carbon solid acid and metal ruthenium supported catalyst,and study on the conversion of cellulose to glucose,sorbitol,levulinic acid were investigated using waste bamboo powder from agricultural and forestry processing as raw materials and concentrated phosphoric acid as an activator in this paper.The main contents of the paper are as follows:1.Using bamboo powder as raw material,P-containing porous biomass carbon(PBC)was prepared in a step by activating carbonization with concentrated phosphoric acid,and then Ru/PBC bifunctional catalyst was obtained by loading Ru nanoparticles(Ru NPs).A series of characterization and determination results indicated that the obtained PBC-1.5-300 in optimized condition possessed optihad stable,abundant micro-mesoporous and high specific surface area(S_BET,896 m²·g^-1)and some strong acidity(0.28 mmol·g^-1)as well as strong affinity on cellulose?-1,4-glycosidic bond thus showing superior activity in catalyzing the hydrolysis of cellulose to glucose.More importantly,the above materials could be used as an excellent acidic carrier for the load of Ru NPs ascribe to the high specific surface area that makes the load of Ru NPs uniform and narrow in distribution(1-6 nm).The prepared 5%Ru/PBC-1.5-300bifunctional catalyst showed excellent catalytic activity in the one-step hydrolysis and hydrogenation of cellulose to sorbitol obtaining 89%of sugar alcohol yield and 98%selectivity of sorbitol under the optimal reaction conditions.Besides,the catalyst showed great reusability in hydrolyzed hydrogenation of cellobiose and direct hydrogenation of glucose.2.In order to further improve the pore structure and acidity of PBC,and the loading efficiency of Ru NPs,the study on porous biomass carbon(PSBC)containing P,Si gained under activated carbonization with concentrated phosphoric acid after intercalation on bamboo powder using silica sol and Ru/PSBC bifunctional catalyst loading Ru NPs were researched.A series of characterization and determination results showed that the prepared PSBC-3-60-400 in optimized conditions had more abundant mesoporous structure,higher surface area(S_BET,1617 m²·g^-1)and improved strong acidity(0.42 mmol·g^-1)compared with PBC-1.5-300showing superior catalytic activity in the hydrolysis of cellulose to glucose reaction.Additionally,having thinner and narrower Ru NPs,1%Ru/PSBC-3-60-400 performed better catalytic efficiency on the one-step conversion of hydrolysis and hydrogenation of cellulose to sorbitol achieving 83.2%sorbitol yield and high Ru conversion numbers(ca.312.6)which was 9.6 times than 5%Ru/PBC-1.5-300 catalyst along with superior reuse performance under the optimal reaction conditions.3.The investigation of porous biomass carbon catalyst containing P,N,Si prepared via introducing carbamate and intercalation of silica sol,activated carbonization by concentrated phosphoric acid was tested.The tested characterization and determination displayed that PSNBC-1-400gained under optimized conditions had abundant mesoporous channel and high specific surface area(S_BET,1237 m²·g^-1)accompanying with bigger aperture(5.88 nm).The prepared PSNBC-1-400 with phosphorus-containing strong acid groups and nitrogen-containing basic groups possessing acid-base bifunctional catalysis could efficiently achieve cellobiose conversion to levulinic acid,reaching pleased yield of levulinic acid(43.2%)under optimized reaction conditions.By the way,the above material still had satisfying catalytic activity after repeately using for four times.