A series of Ni/SBA-15 catalysts was prepared by impregnation method. Effect of NiO content (3060 mass%), calcination time (0.52 h at 800°C), and reduction time (12 h at 800°C) on catalytic performance in combined steam and CO 2 reforming of CH 4 (CSCRM) was studied. N 2 physisorption measurements, powder X-ray diffraction, Hydrogen temperature-programmed reduction, CO 2-temperature-programmed desorption, and transmission electron microscopy were used to investigate physico-chemical properties of the catalysts. The catalytic performance of Ni/SBA-15 in CSCRM was assessed in the temperature range of 550800°C. The results revealed suitable time for calcination and reduction being 0.5 h and 1.5 h, respectively. After these treatments, 40 mass% NiO/SBA-15 catalyst was more active and exhibited higher activity than others. At 750°C, conversion of CH 4 and CO 2 on this catalyst in CSCRM was 91.05% and 78.11%, respectively. High surface area, better reducibility, and good affinity with CO 2 contribute to the high performance of this catalyst.
In this work, 31.4 wt.% Ni/SBA-15 (Ni/SBA-15) nonpromoted and alkalized with ammonia solution and by MgO promoter catalysts were prepared and used for combined steam and CO2 reforming of CH4 (bireforming). Effect of concentration of ammonia solution (NH3(aq)) (10–25 vol.%) and Mg content (3–12 wt.%) on the properties of the Ni/SBA-15 catalysts was investigated by low-angle and powder X-ray diffraction (XRD), N2-BET isothermal adsorption, SEM, TEM, EDS mapping, H2-TPR, and CO2-TPD methods. The performance of the catalysts in bireforming was assessed in the temperature range of 550–800°C. The enhancement of dispersion of NiO particles, reducibility, and basicity of alkalized Ni/SBA-15 catalysts were responsible for improving the catalytic performance of this catalyst. The results revealed that the Ni/SBA-15 treated with 15-25% NH3(aq) solution and promoted with 3-9% Mg exhibited high activity for CH4 conversion. Meanwhile, Ni6Mg/SBA-15 showed the highest CO2 conversion. Among tested catalysts, Ni/SBA-15-20NH3 and Ni9Mg/SBA-15 samples had an almost equal activity with a CH4 conversion of nearly 97% and a CO2 conversion of about 84% at 700°C thanks to its moderate affinity with both CO2 and CH4. However, the H2/CO ratio of the product mixture remained at 2.02 on the Ni/SBA-15-20NH3 catalyst and almost 1 on the Ni9Mg/SBA-15 sample. These results might be related to the fact that the alkalization of the Ni/SBA-15 catalyst by NH3(aq) solution had an advantage over using MgO because side reactions were unlikely to occur.
In this work, a series of 10 wt% NiO/CeO2 catalysts (Ni/Ce) promoted by V2O5 with content varying in the range of 0–0.5 wt% was prepared by the co-impregnation method. The characteristics of the catalysts were investigated by several techniques including N2 physisorption (BET), X-ray diffraction (XRD), Raman spectroscopy, transmission electron microscopy (TEM), EDS mapping, carbon dioxide temperature-programmed desorption (CO2-TPD), and hydrogen temperature-programmed reduction (H2-TPR). The activity of the catalyst was studied in the micro-flow system in a temperature range of 550 °C–800 °C, the feedstock composition CH4/CO2/H2O of 3.0/1.2/2.4 and the weight hourly space velocity (WHSV) of 30,000 ml.h−1.g−1. Adding V2O5 additive, on the one hand increases the reducibility and basicity of Ni/Ce catalyst, on the other hand reduces oxygen vacancies and increases the crystal size of CeO2, leading to various effects on catalyst activity depending on its content. Ni/Ce catalyst promoted with 0.3 wt% of V2O5 was the best among tested ones, on which at reaction temperature of 700 °C, the conversion of CH4 and CO2 reached 97% and 77% respectively, and the molar ratio of H2/CO was 2.1. Meanwhile, on non-promoted Ni/Ce catalyst, the corresponding quantities were 83%, 62% and 1.9, respectively. It is important to note that performance of both was stable for more than 30 h thanks to the better resistance to coke deposition and structural stability.
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