| Biomass resources have the advantages of abundant reserves and renewability,and it has the prospect of development and application to prepare biofuels by pyrolysis or liquefaction of biomass.The pyrolysis oil(bio-oil)obtained from biomass rapid pyrolysis mainly consists of acids,esters,furans,phenols and aldehydes,which will lead to poor quality of pyrolysis oil with high viscosity,low calorific value,poor thermal stability and strong corrosion.In order to improve the quality of bio-oil,Hydrodeoxygenation(HDO)is an effective technology.Hydrogenation(hydrogenation)and hydrogenolysis occur simultaneously in the process of catalytic hydrodeoxygenation.The components of bio-oil are complex.In order to understand the hydrogenation mechanism of bio-oil components,many researches are carried out with model compounds,and the research focuses on the development of hydrodeoxidation catalyst.Due to the complexity of hydrogenation products of bio-oil or its model compounds,there are few related thermodynamic studies.Because the development of biofuels involves a wide range of technologies,a variety of raw materials and complex products.Therefore,based on the hydrodeoxygenation process in the development of biofuels and their by-products,the thermodynamics of hydrodeoxygenation processes are studied by selecting typical alcohols,phenols and acids: glycerin,guaiacol and mixed acid components based on bio-oil,and the high value of products was emphasized to achieve the comprehensive effect of ‘biomass production fuel and high value chemicals'.There is component of glycerin in the bio pyrolysis oil,and glycerin is also a byproduct of biodiesel.It is of great significance to prepare 1,2-propanediol and 1,3-propanediol by high value conversion of glycerol.Guaiacol is an important component of bio-oil phenols,and also a typical product of lignin liquefaction degradation.In addition,to improve the quality of bio-oil,the acid value of bio-oil must be reduced.The results of process simulation can provide reference for industrial application.Research content of this paper and main conclusions are as follows:(1)The process of producing high value product diols by hydrogenolysis of glycerol was studied by thermodynamics.According to the principle of Gibbs minimization,the hydrodeoxygenation processes of glycerol based on different reaction mechanisms were simulated.The thermodynamic parameters of each reaction equation of glycerol hydrogenation were calculated,and the effects of reaction conditions on the equilibrium products of glycerol hydrogenation were emphatically analyzed.The results show that temperature has a great influence on the selectivity of the products.(a)For the reaction system with diols as the main product,1,2-propanediol is more easily formed in thermodynamics.(b)For the hydrogenation of glycerol and the further hydrogenolysis of diols and the reaction system containing methane,methane has the highest selectivity,hydroxyacetone also has a high selectivity,isopropanol has a certain degree of selectivity at low temperature,and the selectivities of other substances are very low.(c)For the reaction system of glycerol hydrogenation to diols and monohydric alcohol,the main products are hydroxyacetone and isopropanol.(d)For the glycerol hydrogenation to diols and the system containing intermediate products,the main products are hydroxyacetone and1,2-propanediol;the optimum conditions for the production of 1,2-propanediol are as follows: temperature: 400-450 K,pressure: 5.0-6.0 MPa,the molar ratio of hydrogen to glycerol of 1.0-1.4.The calculated results are consistent with the related experimental results.(2)Industrial crude glycerin contains other alcohols and more water,so it is of great significance to study liquid-phase in-situ hydrogenation of glycerin.In this paper,the coupling processes of hydrogen production by water reforming with different hydrogen donors(methanol,ethanol and glycerin)and liquid-phase in-situ hydrogenation of glycerin were thermodynamically demonstrated by comparative studies.The results show that the hydrogen production by water reforming of methanol /ethanol has better reaction coupling adaptability with in-situ hydrogenation of glycerol.(a)For the in-situ hydrogenation coupling system containing methane,the main products are methane and carbon dioxide.(b)For the in-situ hydrogenation coupling system without methane,the selectivity of propylene glycol is high.The optimum temperature for the formation of 1,2-propanediol is 350-400 K,and theoptimum temperature for the formation of 1,3-propanediol is 400-450 K.The best material ratios of the three liquid-phase in-situ hydrogenation coupling processes are as follows: the molar ratio of water: methanol: glycerin is 5.0: 1.0: 1.0,the molar ratio of water: ethanol: glycerin is 5.0: 0.5: 1.0,and the molar ratio of water: glycerin is 2.0:1.0.(3)The high value processes of guaiacol hydrodeoxygenation were studied by thermodynamics.Based on the different hydrodeoxidation mechanism of guaiacol,the reaction equations in the corresponding hydrogenation system were determined,and the thermodynamic calculations of guaiacol hydrodeoxidation process were carried out by using the Gibbs reactor model in Aspen Plus software.The effects of reaction conditions on the reaction equilibrium system were mainly discussed.(a)The results show that for the reaction system containing benzene and methane,benzene,methane and phenol have high selectivity,and the other products have low selectivities.(b)For the reaction system containing benzene and cyclohexane,benzene,phenol and cyclohexane have high selectivity,while the other products have low selectivities.(c)For the simplified reaction system of hydrogenation of guaiacol to cyclohexanol and cyclohexanone,the optimum conditions for the preparation of cyclohexanol are as follows: temperature 400-450 K,pressure 6.0-7.0 MPa,the molar ratio of hydrogen to guaiacol of 5.0-6.0.The calculated results are compared with the relevant experimental results.(4)The components of mixed acid based on bio-oil,such as acetic acid,levulinic acid,propionic acid,lactic acid,malonic acid,butyric acid,succinic acid,valeric acid and benzoic acid,were selected.The hydrodeoxidation thermodynamics and technological process of two kinds of mixed acid simulants were analyzed.(a)For the thermodynamics of mixed acid hydrogenation,the effects of reaction temperature and pressure on the conversion rate of each raw material component,the yield of each product and the deoxidization rate of the model compound were investigated.The optimal conditions for the hydrotreating upgrading of biomass pyrolysis oil are450-550 K and 1.0-2.0 MPa.Under this conditions,the transformations of various acids are relatively complete,and the deoxidization rate is higher than 44%.(b)The hydrogenation process of mixed acid simulant was established,and each equipmentmodel in the process,material ratio and flow rate were selected.The material and energy analysis of the technological process were carried out.The results show that the conversions of the two kinds of mixed acids are all completely transformed under the process conditions,and the compressor consumes the most energy in the whole process,accounting for 54.1%(Simulant A)and 50.8%(Simulant B)of the total energy consumption. |
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