Basic Application Research On The Hydrogen Production From Bio-oil And Ethanol By Electrochemical Catalytic Steam Reforming

Biomass is rich and friendly environmentally renewable resource,hydrogen production from biomass is one of the most promising options and it is in the development process.Enhancing hydrogen yield and energy efficiency,decreasing hydrogen production cost and the deactivation of the catalyst,etc.,these key problems are needed to settle.Focused on these problems,this present thesis proposed an efficient reforming approach for production of hydrogen by using the electrochemical catalytic reforming(i.e.,current passing through the catalyst) method.The main and innovation results are:(1) developed an electrochemical catalytic steam reforming method and equipment to produce hydrogen from bio-oil,realized high hydrogen yield(75%-96%) and high carbon conversion(73%-98%) at middle temperature (450-550℃);(2) study on the relationships between the microcosmic structure of the catalyst and conversion of bio-oil,and the mechanism of the electrochemical catalytic steam reforming;(3) study on the electrochemical catalytic steam reforming of ethanol to produce hydrogen;(4) study on the bio-oil reforming catalyst of Ni-Cu-Ce-Mg-Al.Details of the research is as follows:(1).Efficient electrochemical catalytic reforming of bio-oil to produce hydrogen The reforming catalyst of NiO/Al₂O₃ was prepared by the impregnation.We studied the effects of the reforming experiments,including temperatures,current,S/C, GHSV etc.,on the carbon conversion,hydrogen yield and products distribution.In this work,it was observed interestingly that the behavior of the reforming was very sensitive to the current through the catalyst.The carbon conversion and hydrogen yield were both remarkably enhanced by the current.The concentrations of H₂ and CO increased with increasing the current,accompanied by the content decrease of CO₂ and CH₄,e.g.,The carbon conversion significantly increased from 14.7%to 72.7%and hydrogen yield increased from 13.1%to 60.7%at 400℃(other conditions:S/C=5.8,GHSV=6048h^-1,P=1 atom ) with increasing the current from 0 to 3.8 A.Without the current,the content of H₂,CO,CH₄,CO₂was 57.2%,5.8%,3.4%and 26.3%respectively,and the content of H₂ and CO increased to 67.9%å’Œ8.3%, accompanied by the content decrease of CH₄ and CO₂ to 0.4%and 22.6%respectively with increasing the current from 0 to 3.8 A.To make clear the mechanism of the electrochemical catalytic steam reforming, we studied the decomposition of model compounds(e.g.,ethanol) experiments at low-pressure,the electrons desorption were observed from time of flight(TOF) measurements.And we discovered that current enhanced molecule decomposition and reforming have the relationship with the thermal electrons on the surface of the catalyst.The alteration of the catalyst in the bio-oil reforming process were investigated via XRD,XPS,BET,SEM and FT-IR measurements.Based on the above investigation we discussed the thermal electrons in the reforming and decomposition processes significantly promoted the dissociation of the oxygenated organic compounds in the bio-oil,and enhanced the hydrogen yield and carbon conversion.(2).Electrochemical catalytic steam reforming of ethanol to produce hydrogenWe studied the effects of the reforming temperatures and current on the ethanol conversion,hydrogen yield and products selectivity over the Ni-Al₂O₃ catalyst.It was observed that the ethanol conversion and hydrogen yield were remarkably enhanced by the current.And the products were effects by the current.The selectivity of H₂ and CO increased with increasing the current,accompanied by the decrease of the selectivity of CO₂ and CH₄,e.g.,The hydrogen yield and ethanol conversion were 1.66 mol and 98.2%,respevtively,when the current was zero at 400℃(other conditions:water/ethanol=2:1(mol ratio),LHSV=1.8h^-1 P=1 atm),and the selectivity of H₂,CO,CH₄,CO₂ were 48.9%,0.63%,45.7%and 60.3%,respectively.However,the hydrogen yield and ethanol conversion increased to 3.45mol and 99.9%with increasing the current from 0 to 3.2 A,and the selectivity of H₂ and CO increased to 72.7%å’Œ7.65%accompanied by the decrease of the selectivity of CH₄ and CO₂ to 33.3%and 59.3%,respectively.The homogeneous decomposition of ethanol experiments were also studied at atmospheric pressure,the results showed that the current evidently enhanced the hydrogen yield and ethanol conversion,and effects the distribution of the products. The current increased the selectivity of H₂,CO and CH₄,and decreased the selectivity of C₂H₄O,H₂O and C₂H₄.The alteration of the catalyst after the ECR processes or the CSR process were investigated via XRD,XPS,BET and TEM measurements.The mechanism of the electrochemical catalytic reforming of ethanol was discussed based on the above investigation and the decomposition of ethanol at low-pressure and atmospheric pressure.(3) Study on the bio-oil reforming catalyst of Ni-Cu-Ce-Mg-AlWe developed bio-oil reforming catalyst of Ni-Cu-Ce-Mg-Al,the catalyst showed good reforming activity and high BET surface area.The hydrogen yield and the carbon conversion reached 92.4%and 93.6%respectively,under the conditions: T=400℃,I=3.1A,S/C=6.9,GHSV=10500h^-1,P=1atm.The hydrogen yield and the carbon conversion have no obvious change and the carbon deposition is very slight after 20h.The alteration of the catalyst after the ECR processes or the CSR process were investigated via XRD,XPS and BET measurements.