Microbial Cracking Of Cotton Straw To Prepare Bio-oil And Its Upgrading Technology

With the development of human society, and the gradual increase of the consumption of fossil fuels, and the price of fossil fuels is also increased gradually. Additionally, the problems of energy shortage and environmental pollution have restricted the development of China’s economy. Therefore, the demand for alternative fuel is becoming more and more impendency. Biomass resource is a kind of clean and renewable resource, which can be converted into bio-fuel or high-value added chemicals by biomass pyrolysis and liquefaction technology. China, as one of the biggest agriculturalproduction country,there are abundantbiomass resourcesof crop strawand the development and utilization of biomass resources in crop straw attracts more and more attention from researchers. Therefore, the biomass microwave pyrolysis and liquefaction on cotton straw were researched respectively in this paper, and the products were analyzed.The main component of the products were determined.And the optimal conditions of catalytic hydrogenation deoxidation experiments of model compounds were determined,therefore, the quality of bio-oil has been improved.Ithas far-reaching significance for the mitigation ofdependence of fossil fuels and protection of ecological environment1.In this study, response surface methodology(RSM) based on central composite rotatable design(CCRD) was applied to determine the optimum condition for pyrolysis of Cotton stalk using microwave-assisted pyrolysis(MAP) system. Three operating variables, namely microwave power(W),reaction temperature(℃) and reaction time(min) with a total of 17 individual experiments were conducted to optimize the combination effects of the variables. The optimal liquefaction conditions were estimated as: the microwave power of 1800 W, the reaction time of 24 min, the reaction temperature of 550 ℃with the liquefaction yield of 32.47%. The bio-oils were mainly composed of phenols and benzenecarboxylic acid.2.Optimal process of preparing bio-oil from cotton stalk by microwave pyrolysis was studied. The effects of sulfanilic acid,clay, nickel chloride were investigated on the yields of bio-oil. Then the effects of magnesium chloride, sodium chloride, zinc chloride, nickel chloride were investigated on pyrolysis of cotton stalk by phosphoric acid pretreatment. The results show that the highest yield of 45% of bio-oil was obtained under the conditions of pyrolysis time of 30 min, pyrolysis temperature of 500 ℃and microwave power of 1900 W. Phosphoric acid,the mass fraction of 10%, is used to preprocess.Sodium chloride was used as the catalyst in the experiment.The compositions of the cotton stalk bio-oil were analyzed by FT-IR and GC-MS. It was proved that the prepared cotton stalk bio-oil is a complex organic compounds, including phenol, aldehyde, ester, acid, ketone,alcohol,furan,etc., The phenols had the hightest relative content of the bio-oil.3.The macromolecular substances in cotton stalk can be transformed into chemical constituents by using the method of direct liquefaction of biomass. In order to obtain high yield and high quality of bio-oil, cotton stalks were used as raw materials and ethylene glycol was used as the reaction medium in this article. The optimal proportion of sulfuric acid and phenol as catalyst has been determined. EG-to-feedstock ratio, Microwave power and content of catalyst were chosen as independent variables for a central composite rotatable design(CCRD) based on the results of single factor experiments. The optimal liquefaction conditions were estimated as:the cotton stalks particles of 0.25 mm in diameter, EG-to-feedstock ratio of 13:1(w/w), microwave power of 500 W,the catalyst content of 23%(catalyst/EG, w/w%), The amount of concentrated sulfuric acid is 3 times the dosage of phenol in catalyst dosage, the reaction temperature of 150 ℃and the reaction time of 25 mins. The liquefaction rate of bio oil was 90.26% under the optimum conditions. And then, the bio oil is analyzed by GC-MS and FT-IR. The results showed that the main chemical substance in the bio-oil include acids, esters, phenols and hydrocarbons, etc.4.The solvent separation method is used for the bio-oil products separatedThrough GC-MS analysis, that the main compounds of the bio-oil were determined as phenols, ketones, acids, esters, aliphatic compounds, aldehydes, etc., the highest proportion of phenol compounds.The acidity, oxygen content and quality of the bio-oil were not suitable for application. Upgrading of bio-oil should be processed further to improve its quality just to reduce high oxygen content in bio-oil.5.Catalytic hydrogenation deoxidization experiment was carried out in a fixed bed, and phenol was used as model compounds.The effects of factors on phenol catalytic hydrogenation deoxidization are researched through the single factor experiment,and the phenol conversion and selectivity of cyclohexane as the goals for experiment.The optimal reaction conditions:20% Ni/HZSM 5 as catalyst, the reaction temperature of 220 ℃, the hydrogen pressure of 4 MPa, the feeding velocity of 0.1 mL/min.And the optimal phenol conversion rate of 99.93%, cyclohexane selectivity of 98.07%.