Thermodynamic Study On Hydrodeoxygenation Of Compounds Containing Aldehyde Groups And Phenols In Bio-oil

Rapid pyrolysis of biomass to produce bio-oil is an important direction of bioenergy development and utilization.However,the pyrolysis bio-oil contains oxygen-containing compounds such as acids,esters,furans,phenols and aldehydes,which has the problems of high viscosity,high acidity,high water content,low calorific value,poor thermal stability and strong corrosivity.It is necessary to improve the quality of bio-oil.Hydrodeoxygenation(HDO)of bio-oil is an important technology for bio oil quality improvement.At present,the research on bio-oil hydrogenation mainly focuses on the improvement of catalyst.Due to the complex reaction and many products in the catalytic hydrogenation process of bio-oil or its model compounds,there are few thermodynamic studies on bio-oil hydrogenation process.In this paper,Aspen Plus analysis software was mainly used.The hydrodeoxygenation thermodynamics of model compounds furfural,aldehyde containing mixed components and phenolic compounds based on bio-oil were studied,and the hydrodeoxygenation reaction thermodynamics and hydrogenation process flow of simulated bio-oil were simulated and analyzed.The optimization results can provide thermodynamic reference for the practical application of bio-oil hydrotreating.The research contents and main conclusions of this paper are as follows.(1)The thermodynamic analysis of gas phase hydrodeoxygenation of furfural was carried out.Furfural is a typical component of bio-oil and an important product of hydrolysis of agricultural and forestry plant wastes.Furfural can be hydrogenated into high value-added chemicals such as 2-methylfuran and 2-methyltetrahydrofuran.Based on the hydrogenation mechanism of furfural,the thermodynamics of gas-phase hydrogenation of furfural was studied in this paper.The thermodynamic parameters of furfural hydrogenation reaction were calculated,and the effect of reaction conditions on the equilibrium products of furfural hydrogenation system was discussed.The calculated results were compared with the relevant experimental results.The results show that the gas phase hydrogenation of furfural is easy to produce cyclopentanone and cyclopentanol,followed by 2-methylfuran and 2-methyltetrahydrofuran.When hydrogen is insufficient,higher furan and tetrahydrofuran products can be produced.(2)The liquid-phase in-situ hydrogenation of furfural was analyzed by thermodynamics.Methanol and ethanol were selected as hydrogen donors respectively.The "alcohol-water-furfural" hydrogenation systems weres simulated and analyzed.In addition,the hydrogenation of furfural with methanol as both hydrogen donor and solvent was studied.The results show that the hydrogen supply from methanol water reforming has a good thermodynamic fit with the in-situ hydrogenation of furfural.When methanol is used as both hydrogen donor and solvent,2-methyltetrahydrofuran has high yield.(3)The hydrodeoxygenation thermodynamics of aldehyde containing mixed components based on bio-oil was analyzed.Typical aldehyde containing compounds:furfural,5-hydroxymethylfurfural,glutaraldehyde,butyraldehyde,cinnamaldehyde,benzaldehyde,p-hydroxybenzaldehyde and p-methylbenzaldehyde were selected to form aldehyde containing mixed components(Abbreviated as mixed aldehydes)in a certain proportion,and the hydrodeoxygenation process was studied thermodynamically.The results show that the hydrogenation reaction of aldehyde containing mixed components are relatively complete when the temperature is 300-600 K.Increasing the pressure is beneficial to improve the conversion of raw materials.However,the significant range of pressure on improving the conversion of aldehyde based raw materials is 0.1-3.0 MPa.(4)The hydrodeoxygenation thermodynamics of phenolic compounds based on bio-oil was analyzed.The hydrodeoxygenation thermodynamics of o-cresol(also known as o-methylphenol)and o-methoxyphenol(also known as guaiacol)based on a certain hydrogenation mechanism were studied respectively.The results show that the reaction temperature,pressure and the ratio of hydrogen to phenolic compound have effects on the product distribution.(5)The hydrodeoxygenation reaction thermodynamics and process flow simulation of simulated bio-oil were analyzed.In order to obtain the comprehensive effect of bio-oil hydrotreating,considering the high content and representative acid,aldehyde,phenol,ketone,alcohol,ester and sugar components in bio-oil,lactic acid,malonic acid,benzoic acid,furfural,cinnamaldehyde,o-cresol,o-methoxyphenol,eugenol,hydroxypropanone,ethylene glycol,ethyl acetate and glucose were selected to form bio-oil simulant.The effects of temperature and pressure on the equilibrium products of bio-oil hydrogenation were studied,and the simulation effect of bio-oil hydrogenation process system was further analyzed at the condition of sufficient hydrogen.The thermodynamic results of bio-oil hydrogenation and deoxidation show that the bio-oil hydrogenation is more complete in the range of 300 ～ 500 K and at a higher pressure of 3.0 MPa.The analysis of various components before and after hydrogenation shows that the mass fraction of alcohol after hydrogenation is about 40%and the content of alkane is about 26%.Hydrogenation can effectively improve the quality of bio-oil.The simulation results of bio-oil hydrogenation process flow show that the main energy consuming equipment in the hydrogenation system are compressor and preheater,which can reduce energy consumption by reducing hydrogen flow,increasing heat exchanger load and improving the recovery and utilization of waste heat.