Research On The Hydrogen Production From Acetic Acid By Electrochemical Catalytic Steam Reforming And Its Mechanism

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 acetic acid, realized high carbon conversion and high hydrogen yield at relatively low temperature of 300-400℃; (2) study on the relationships between the microcosmic structure of the catalyst and conversion of acetic acid, and the mechanism of the electrochemical catalytic steam reforming. Details of the research is as follows:(1). Efficient electrochemical catalytic reforming of acetic acid to produce hydrogen and decomposition of acetic acid.The reforming catalyst of NiO/Al₂O₃ was prepared by the impregnation. We studied the effects of the temperatures and the current on the carbon conversion, hydrogen yield and products selectivity. 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 3.5% to 83.1% and hydrogen yield increased from1.9% to 82.1% at 300℃with increasing the current from 0 to 4.0 A(other conditions : S/C=5.8,GHSV=6048h^-1,P=1 atom ).The homogeneous tests under different current over the quartz bed (the quartz powder embedded around the Ni-Cr wire) to study the decomposition of acetic acid, It was observed that the current promotes the decomposition of acetic acid. e.g., at 500℃, the carbon conversion was very low (about 1%) when I = 0 A, However, the carbon conversion increased to 10.8 % for I = 4.0 A at this temperature. (2) To make clear the mechanism of the electrochemical catalytic steam reforming, we studied the decomposition of acetic acid 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 acetic acid reforming process was investigated via XRD and XPS measurements. Based on the above investigation, we discussed the thermal electrons may play an important role in promoting the acetic acid decomposition, its reforming and the catalyst reduction, partly leading to the increase of the carbon conversion and the hydrogen yield in the electrochemical catalytic steam reforming process.On the other hand, the temperature distributions in the catalyst bed and the temperature on the Ni-Cr wire under different conditions were measured. The local temperature near the electrified Ni-Cr wire, also, was higher than the averaged temperature. Accordingly, the activity of the catalyst reforming near the electrified Ni-Cr wire should be significantly higher than other position in the bed, partly, leading to the enhance of the overlap reforming effect.