Study On Influence Factors On The Reaction Between Magnesium-Based Hydrogen Stroage Material And Thiophene

Magnesium-based hydrogen storage material, when heated at certain temperature, will release active hydrogen that could react with thiophene, which is called hydrodesulfurization. In this paper, Mg-based hydrogen storage material 70Mg30C made from magnesium and crystallitic carbon by mechanochemistry method was used to the hydrogenation reaction of thiophene. The effect of temperature, constant temperature time as well as the hydrogen pressure on the reaction products of 70Mg30C and thiophene were studied. Scanning electron microscope (SEM), energy disperse spectroscopy (EDS), X-ray diffraction (XRD), fourier infrared spectroscopy and mass spectrum (MS) were used to characterize and analyze the prepared hydrogen storage material and hydrogenation products.The research result indicated that as the temperature increased, the hydrogen release rate and capacity of the hydrogen storage material was improved, both of which had a sharp increase within 250～350℃due to the decomposition of MgH2. When the temperature was higher than 350℃, the dehydrogenation velocity and capacity reached the maximum. Meanwhile, with the growth of temperature, the plateau pressure of absorption and desorption hydrogen of the hydrogen storage material was also raised, which was between 0.1～0.3 MPa at 300℃. When the temperature reached 400℃, the plateau pressure was almost disappeared. Actually, the plateau pressure of absorption and desorption hydrogen were two curves that did not coincide, and had lag.At 250℃, the hydrogen storage material did not react with thiophene. As the temperature increasing to 300℃, H2S and MgS were found in the reaction products, which indicated that the hydrogen storage material had reacted with thiophene. As the temperature further increase, the quantity of H2S decreased while the MgS increased, which implied that a higher temperature facilitated the generation of MgS whose chemical equation is H2S+Mgâ†'MgS+H2.Every temperature had a homologous reaction time. When the temperature was low, the dehydrogenation velocity was slow which led to the reaction between hydrogen storage material and thiophene needing a long time. Therefore the reaction time should be determined in reference to the dehydrogenation velocity of the hydrogen storage material. When the temperature was constant, we could detect different hydrogenation product at different reaction time. The result showed that H2S was first generated from the hydrogen in the material and thiophene, and then MgS was generated from the former H2S and magnesium from the heated material. When there was hydrogen atmosphere in the high-pressure reaction kettle, the hydrogen pressure had a great effect on the hydrogenation product. When the hydrogen pressure was lower than the plateau pressure of absorption and desorption hydrogen, the hydrogen storage material tended to be a desulfurizer whose principal product was MgS. When the hydrogen pressure was higher than the plateau pressure, the hydrogen storage material tended to act as a catalyst for the hydrodesulfurization of thiophene whose reaction product was mainly H2S. Therefore, the reaction products could be controlled by change the hydrogen pressure in the reactor.