Preparation Of The Doped Modification Of Porous Carbon By Humic Acid And Research Its Adsorption And Dehydrogenation Properties

Humic acid was extracted from lignite by using low rank coal as raw material,and it was further modified and doped to make porous carbon carrier.The preparation method of humic acid based porous carbon and the effects of different preparation conditions on the properties of porous carbon carriers were investigated.A series of porous carbon with high specific surface area and different pore diameter were prepared by activation methods,and the influence of B,N doping modification on physical and chemical properties of the porous carbon carriers were also investigated.Moreover,the porous carbons which modified or not were used as carriers to support the iron and cerium metal oxides.The adsorption of Congo red and propane dehydrogenation both were used as probe experiments to studied the adsorption and catalytic performance of different porous carbon samples and thier composite materials.It is hoped that the above basic research on the preparation and modification of porous carbons may provide inspiration for the future application of humic acid and the high value-added clean utilization of lignite and other low-rank coal resources.The mainly study results were showed as follows:(1)Using lignite as raw material,humic acid was extracted from lignite and it was further used to prepare porous carbon by activation method.The effects of different preparation conditions on the structure and properties of porous carbon were studied.The experimental results showed that the porous carbon sample presented the largest specific surface area and the best adsorption effect when the amount of activator added was three times that of humic acid.For different porous carbons prepared in the same proportion,the C-3(porous carbon based humic acid without direct centrifugal drying)exhibited the largest specific surface area with 1578 m2/g,but its adsorption effect was relatively not optimal.Compared with other samples,the fulvic acid based porous carbon C-3-U presented the best adsorption properties of Congo red,and it also displayed the largest microporous specific surface area and the microporous pore volume,which were 982 m2/g,0.46 cm3/g,respectively.Therefore,it showed that the adsorption performance of porous carbon samples were directly proportional to thier specific surface area and pore volume of micropores.The catalytic activity of propane dehydrogenation was investigated by selecting the porous carbon C-3 supported metal cation iron and cerium catalyst C-3-Fe-Ce,and the experimental results showed that the prepared catalyst greatly reduced the reaction temperature of propane dehydrogenation from 500 °C to 250 °C,which greatly reduces energy consumption.(2)Based on the same preparation method as C-3 above,N and B atoms were doped.As a result,it was found that the specific surface area of C-3 was 752 m2/g,and the pore volume of micropores was 0.39 cm3/g,and the N-doped porous carbon C-3-N had a specific surface area of 841 m2/g and a micropore volume of 0.73 cm3/g.Therefore,the doping of N increased micropore specific surface area and pore volume of the porous carbon,which greatly enhanced the adsorption properties of N-doped porous carbons for Congo red.The results showed that the adsorption performance of N-doped porous carbon was proportional to their micropore pore surface area and micropore pore volume.However,the B-doped porous carbon presented smaller micropore pore surface area and micropore pore volume than that of N-doped one,and it showed poor adsorption effect on Congo red.The composite catalyst was prepared by using B-,N-diatomic doped porous carbons as carrier to support iron and cerium metal oxides,and the catalytic properties of composite catalyst on propane dehydrogenation were also investigated.It was found that the presence of catalyst can reduce the reaction temperature to a minimum of 300 °C.Compared with N-doped porous carbon carriers,B-and N-diatomic doped composite(C-3-B-N-Fe-Ce)not only showed the enhaced catalytic activity on the dehydrogenation of propane,but presented both high propylene selectivity and propane conversion at same time.The results showed that the B-and N-doped porous carbon retains the conversion of propane at 300°C while controlling the propane carbon bond fragmentation and proceeding toward the production of propylene.