Research On Classified Separation And Catalytic Hydrotreatment Of Bio-oil

In recent years, search for the renewable, clean resources has boosted researchers’ interest. Biomass flash pyrolysis oil, also known as bio-oil, is considered to be a promising alternative fuel. However, bio-oil cannot be directly used in the traditional engine s to replace fossil fuels due to its shortcomings, including low heating value, high corrosiveness, high viscosity, and high water content etc. It is necessary to upgrade the bio-oil to obtain high-quality liquid fuels. In this paper, a method of classified separation of bio-oil prior to the upgrading was proposed, which was good for the enrichment of compounds with similar properties. And then different upgrading methods were conducted for each type of material according to their properties. Light distillates separated from bio-oil were performed two-stage hydrotreatment with a Pd/C catalyst. And the kinetics for hydrotreatment was researched. One-pot catalytic hydrocracking of the middle and heavy distillates separated from bio-oil was investigated with the catalysts of Co Mo S/Al2O3 and HZSM-5. Finally the bimetallic catalyst of Pd-In/C was prepared for the hydrogenation.Flash pyrolysis oil was effectively separated into four groups of substances by extraction and vacuum distillation, and they were water soluble fraction, crude saccharides, phenolic compounds, and residues. The separation process was discussed in detail. The optimal separation condition was temperature 50°C, 1:1 of water-to-oil ratio, and 20 min of contacting time. At this optimal separation condition, 4.1 wt.% of levoglucosan accounted for the bio-oil could be obtained. And the yield of water soluble fraction, crude saccharide s, phenolic compounds and residues was about 31 wt.%, 30 wt.%, 30 wt.% and 9wt.%, respectively. The compounds with similar properties were enriched by classified separation. And this method is a promising route for efficiently making use of bio-oil.Light distillates obtained from bio-oil could be converted into oxygenated liquid fuels through a two-stage hydrotreatment process with Pd/C catalyst. The goal of the first hydrotreatment stage was to stabilize the highly active components, which contained carbon–carbon double bonds and aldehyde groups. The second hydrotreatment stage aimed to saturate the components with benzene rings and keto groups to obtain saturated oxygenated compounds. The main products after the two-stage hydrotreatment were C5–C9 alcohols. The hydrotreatment reaction went through ketone/aldehyde isomerization, dehydration, hydrogenation, open rings reaction based on the hydrogenated model compounds. The blending experiments of hydrogenated products and 93# gasoline were conducted. And the octane number of blending fuels was increased by 0.6 units compared to 93# gasoline.The kinetics of the second hydrotreatment stage was investigated to predict the product distribution and establish a reaction model. The influence of external and internal mass transfer on reaction rate was explored, respectively. The total hydrogen content was applied to describe the hydrogenated kinetics equation. The effect of internal and external mass transportation on reaction rate could be negligible and the order of hydrotreatment reaction was 2.0 at experimental conditions.One-pot catalytic hydrocracking of middle and heavy distillates separated from bio-oil was investigated with the catalysts of Co Mo S/Al2O3 and HZSM-5. The yield of liquid, gas and solid phase was 87.0 wt.%, 11.9 wt.% and 1.15 wt.% at the conditions of 390 oC, 6.0MPa H2, 180 min and 800 rpm. The compositions of liquid phase were C7-C14 hydrocarbons. The high heating value of liquid products was 42.35MJ/kg, which was close to that of petroleum fuels. The energy efficiency could reach up to 84% without adding any solvent. This method provides an economically feasible route for the preparation of biofuels.The bimetallic catalyst of Pd-In/C was prepared by means of wet impregnation. The preparation conditions of p H value, stirring speed, contacting time and drying temperature were investigated in detail. The desired catalyst was obtained under the conditions of p H = 6.0, 500r/min, 90 min and 100 oC. And the desired catalyst was used to hydrogenate catechol at the conditions of 200 oC, 5.0MPa H2, 2.0h and 0.25 g Pd-In/C. After reaction, the catechol could be completely converted into alcoholic compounds. The bimetallic catalyst provides a new choice for bio-oil hydrogenation.