| The development ofrenewable resources for the production of energy-safe fuels and chemicals is becoming increasingly important due to the depletion of fossil fuels and the increase in demand for fuels.Lignocellulosic biomass is a major renewable resource available for its wide range of sources,large reserves,and no competition for food.Lignocellulosic biomass can be transformed into many products,such as biofuels(bio-diesel,bio-ethanol and bio-gas)and chemicals(acetic acid,acetone and lactic acid)by chemical or biological means,and now these products are mainly from petroleum.At present,biofuel and high value-added chemicals such as ethanol and other high-value chemicals have become the main processes by converting acid carbohydrates from lignocellulose into soluble monosaccharides by acid hydrolysis or directly by two-stage indirect conversion.The solid acid catalyst has the advantages of high activity,good selectivity,long catalyst life and easy recycling,and can convert the lignocellulosic biomass into biofuel well,replacing many conventional liquids acid in the process of hydrolysis and pretreatment.Magnetic solid acid as a complex catalyst,not only has a high activity of solid acid,but also has the magnetic-separated feature.To simplified the separation step and saved the cost in the hydrolysis process.In this paper,Fe3O4 particles were synthesized by coprecipitation method.The magnetic solid acid Fe3O4/C-SO3H was synthesized by carbonization and sulfo nation process.The yield of xylose produced by catalytic hydrolysis of biomass corn cob was investigated.The four preparation conditions of Fe3O4/C-SO3H were simulated and optimized.The Fe3O4/C-SO3H(Fe3O4,Fe3O4/C)magnetic solid acid was analyzed by FT-IR,XRD,VSM,TG/DTG,BET and other methods.The other is the preliminary discussion on the recycling and use of the catalyst.The mechanism of hydrolysis of cellulose and hemicellulose by magnetic solid acid was proposed,which provided the theoretical basis for the hydrolysis of lignocellulosic biomass by magnetic solid acid.(1)Fe3O4 particles were synthesized under the condition of NaOH solution at 80? for 8 h.The Fe3O4/C-SO3H was prepared by using Fe3O4 particles as the magnetic carrier.The optimum conditions were the carbonization temperature is 450?,the carbonization time is 3 h,the sulfo nation temperature is 100? and the sulfonation time is 9 h.The optimum conditions of four kinds of preparation conditions of Fe3O4/C-SO3H were as follows?carbonization temperature 455?,carbonization time 4.8h,sulfonation temperature 107? and sulfonation time 10.0 h,The main factors affecting the activity of the magnetic catalyst are:sulfonation time>carbonization time>carbonization temperature>sulfonation temperature.(2)The Fe3O4/C-SO3H(Fe3O4?Fe3O4/C)were studied by a variety of analytical methods.The results showed that the saturation magnetization was 7.78 Am2/kg and the specific surface area was 4.26 m2/g,a particle size of about 20 nm,a total acid content of 1.66 mmol/g and a chemical formula of CH0.689O0.443S0.021Fe0.124.The solid acid catalyst can be stably dispersed in the reaction system,and the effect of the external magnetic field can be quickly separated from the reaction system and repeated several times.(3)The optimum reaction conditions for the catalytic hydrolysis of corncobs were as follows:reaction time was 10 h,reaction temperature was 140?,catalyst dosage is 1.5 g,solid/liquid ratio is 2:50 g/mL(corncob content is 0.5 g).The yield was 51.01%.The hydrolysis process and mechanism of lignocellulose catalyzed by magnetic solid acid were summarized,which provided guidance for the synthesis of monosaccharides and the synthesis of lignocellulose by selective hydrolysis of lignocellulose. |
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