Tolerance of bean seedlings (Vigna spp) to lead (Pb+2)
Abstract/Summary
Methane steam reforming is a well-established process for production of hydrogen a source of clean energy since this process produces a high H2/CO among many methane reforming reactions. However, the high temperature conditions in the industry cause some demerits, and uneconomical due to large energy consumption. Utilizing the right support material for nickel based catalyst may lead to higher conversion at relatively low temperature. In this study, nickel based catalysts on various JRC-zirconia with different surface area as well as ceria addition were prepared and characterized. At the same time, the catalytic activity at low temperature of 600oC in the steam reforming process was studied. The nickel and cerium addition were prepared by wet impregnation method with 10wt.% of nickel loading whereas three concentrations of cerium of 5wt%, 10wt.% and 15wt% of cerium were applied on the zirconia. The catalysts were characterized by BET, EDX, AAS, SEM, XRD and TPD technique to verify the surface area, actual nickel content loading, morphology and structure as well as the acid-base properties of the catalysts. The results showed that wet impregnation was effective to disperse the nickel on the surface of zirconia. Calcination process decreased the surface areas of the catalysts and caused for the agglomeration of nickel on the surface of the samples. XRD results confirmed the presence of two dominant phases tetragonal and monoclinic depending on the type of zirconia. Nickel oxide interacted and incorporated into the surface of support materials. The highest basic sites and acid sites density were found out on the Ni-Z-3 catalyst. The acid sites decreased and basic sites increased in the case of promoted catalysts. Steam reforming reaction was carried out in a micro-quartz tube reactor. The methane reacted catalytically with the steam at the H2O/CH4 ration of 3. Water was ii injected to an evaporator by a syringe pump. The investigation of time-course activity tests were conducted in 5 hours with 20-minute time intervals. Among nickel based catalysts with different zirconia types, Ni-Z-3 gave the highest average percent methane conversion at reaction temperature. The above catalyst was followed by Ni- Z-2 and Ni-Z-4, and Ni-Z-5 performed the poorest among the group. The catalyst having higher activity in term of methane conversion exhibited lower H2/CO selectivity since the side water gas shift reaction occurred. Thus, Ni-Z-5 had the highest H2/CO selectivity of 7.128. And the addition of ceria improved the performance of the catalyst. Regarding three concentration of ceria content, C-10-Ni- Z-3 showed the highest percent methane conversion, followed closely by C-5-Ni-Z-3 and C-15-Ni-Z-3.
