Controllable Synthesis And Properties Of Biochar Based Metal-organic Frameworks (MOFs) Composite

In this paper,biochar and solid acid catalyst were prepared from grape skin,and metal organic framework materials MIL-101(Cr)and bimetallic MOFs were prepared.The solid acid catalyst and MIL-101(Cr)were mixed to prepare composite catalyst.Biochar was used as adsorbent to adsorb methyl orange,and other materials were used as catalysts respectively to study its catalytic effect on the conversion of glucose to 5-hydroxymethylfurfural.The results are as follows:Firstly,biochar was prepared from biomass waste grape skins by oxygen-limited constant temperature carbonization method.The optimal activation conditions were confirmed by designing orthogonal experiments with three factors and three levels.Biomass activated carbon was prepared and applied to the adsorption of methyl orange.Samples were analyzed by SEM and FT-IR spectra.The effects of reaction temperature,biochar addition and initial concentration of methyl orange on adsorption were investigated.The adsorption process was studied by adsorption thermodynamics,isotherm and kinetics.The adsorption of methyl orange by biochar was more suitable for fitting the quasi-second-order kinetic equation.The adsorption process was studied by adsorption thermodynamics,isotherm and kinetics.The adsorption of methyl orange by biochar was more suitable for fitting the quasi-second-order kinetic equation.The fitting data of adsorption thermodynamics prove that the adsorption reaction process is spontaneous and endothermic.Secondly,the biomass activated carbon is sulfonated with concentratedsulfuric acid to prepare a solid acid catalyst,terephthalic acid and chromium nitrate nonahydrate are reacted through hydrothermal reaction to prepare MIL-101(Cr),and MIL-101(Cr)and solid acid are doped and modified to prepare a composite catalyst with double catalytic sites,which is applied to glucose conversion 5-HMF to study the catalytic performance.Solid acids contain sulfonic acid groups,which can be used as Br?nsted acidic catalytic sites and can effectively promote fructose dehydration to generate 5-HMF.However,the metal organic framework structure contains Lewis acidic catalytic sites,which can catalyze glucose to isomerize to fructose.Therefore,solid acid catalyst and MIL-101(Cr)can effectively catalyze glucose to5-HMF.However,solid acid MIL-101(Cr)contains both Br?nsted acidic catalytic sites and Lewis acidic catalytic sites,so the conversion efficiency is greatly improved to 47%.The solid acid group MIL-101(Cr)is regulated and controlled by different solid acid doping amounts,so that the catalytic performance reaches the strongest.Solid acid MIL-101(Cr)was used as catalyst to investigate the effect of different reaction conditions on the conversion experiment.The optimal reaction conditions were designed as130? reaction temperature,glucose dosage 0.1g,catalyst dosage 0.05 g,and reaction time 120 min.Finally,the reusability of the catalyst was investigated.After five cycles,the catalyst still retained certain catalytic activity.Bimetallic MOF was prepared by doping MIL-101(Cr)with metal and hydrothermal reaction.Different bimetallic MOF catalysts were prepared by doping different metal nitrate salts cobalt nitrate,nickel nitrate,manganese nitrate and ferrous nitrate with chromium nitrate through hydrothermal method and modification before synthesis.The catalytic performance was investigated through the conversion of glucose into 5-HMF.MIL-101(Cr,Cu)has the best catalytic effect,and its catalytic performance has been improved compared with that of single metal MIL-101(Cr).MIL-101(Cr,Cu)isregulated by different doping ratios of Cr and Cu,and the catalytic performance reaches the strongest when the doping ratio is 6:4.MIL-101(Cr,Cu)was used as catalyst to investigate the influence of different reaction conditions on the conversion experiment.The optimal reaction conditions were designed as 130°C reaction temperature,glucose dosage 0.1g,catalyst dosage 0.05 g,and reaction time 120 min.Finally,the reusability of the catalyst was investigated.After five cycles,the catalyst still retained certain catalytic activity.