Thermodynamic And Experimental Study On In-situ Hydrogenation Process Of Phenol By Hydrogen Supply From Methanol-Water Reforming

Bio-oil is a renewable liquid fuel converted from biomass.Because of its high oxygen content,bio-pyrolysis oil can not be directly used as ordinary fuel,so it must be deoxidized and purified.Bio-oil hydrodeoxygenation process includes gas phase hydrogenation and liquid phase hydrogenation.In-situ liquid-phase hydrogenation of bio-oil is the coupling of hydrogen production by hydrogen donor and liquid-phase catalytic hydrogenation without external hydrogen source.It has the advantages of simple process,mild reaction conditions and low production cost.Phenol has high content in bio-pyrolysis oil.In this paper,phenol was used as model compound and methanol was used as hydrogen donor.The process conditions of in-situ hydrogenation of phenol on different nickel-based catalysts were studied.Due to the complexity of the"methanol-water-phenol"reaction system,in order to analyze the reaction mechanism better,the thermodynamics of the multiple reactions in the"methanol-water-phenol"three-material system were discussed.This study can provide reference for in-situ catalytic hydrogenation of phenolic components or real bio-oil.The research contents and some conclusions of this paper are as follows.?1?Based on the principle of Gibbs free energy minimization principle,the thermodynamic analysis of the multiple reactions of the"methanol-water-phenol"three-substance system was carried out.Among them,a comparative study of methanol-water reforming and phenol-water reforming was carried out.Thermodynamic calculations for complex and simple systems of alkylation of methanol and phenol were carried out.A comparative study of phenol in-situ hydrogenation systems with and without methane was carried out.The effects of temperature,pressure and material ratio on various equilibrium reaction systems were discussed,and compared with the corresponding experimental results.?2?A preliminary experimental study on the coupling reaction of hydrogen production from methanol water reforming and phenol hydrogenation was carried out using Raney Ni as catalyst.The effects of reaction temperature and pressure,reaction time,molar ratio of materials,amount of catalyst and alkali?NaOH?addition on in-situ hydrogenation of phenol were investigated.The optimum reaction conditions obtained were as follows:reaction temperature 220?,initial pressure atmospheric pressure,catalyst dosage 0.75g,reaction time 7 h and water-methanol-phenol molar ratio 25:10:1.At this time,the conversion of phenol was 97.1%,and the selectivity of cyclohexanol was 85.9%.The in-situ hydrogenation of phenol can be promoted by adding a certain amount of alkali promoter?NaOH?in the system.?3?Nickel-based catalysts modified with different carriers and active components were prepared.The in-situ hydrogenation of phenol for hydrogen supply from methanol-water reforming was carried out using the prepared catalysts.The in-situ hydrogenation performance of different nickel-based catalysts was screened and compared.The results show that the catalyst supported on biomass activated carbon has the best in-situ hydrogenation performance of phenol under reaction conditions.The highest conversion rates of phenol and methanol were 95.7%and81.0%respectively.?4?The nickel catalyst supported on biomass activated carbon?15Ni/AC840?was characterized by BET and other techniques.The in-situ hydrogenation of phenol from methanol-water reforming was studied using the catalyst.The effects of catalyst amount and mixing ratio(15Ni/AC₈₄₀ and Raney Ni),alkali promoter?NaOH?,reaction temperature and reaction time on in-situ hydrogenation of phenol were investigated.The results show that when 15Ni/AC840 is 0.15g,Raney Ni is 0.15g,NaOH-phenol molar ratio is 1:1,reaction temperature is 220?,initial pressure is atmospheric pressure,reaction time is 3-5h,water-methanol-phenol molar ratio is25:10:1,the conversion of phenol can reach more than 95%.In addition,the effects of different hydrogen donors were compared.The experimental results of this paper were compared with the thermodynamic results.Finally,the main reaction pathway of phenol in-situ hydrogenation from hydrogen supply of methanol-water reforming was analyzed based on the results of the experiments and related studies.