چكيده به لاتين
The reduction of fossil fuels, in addition to increasing environmental concerns, has led to great interest in efficient conversion and use of renewable energy sources. In this study, acetone steam reforming on Ni/Al2O3 catalysts with nickel content of 5, 7.5, 10, 12.5, 15, 17.5, and 20% by weight, which was inoculated on industrial alumina base (g5/m2) /157) have been loaded, it was examined. With the increase of nickel content from 5% by weight to 20% by weight, the specific surface area of the catalyst decreased from 145.8 m2/g to 126.9 m2/g and the crystal size of the particles increased from 5.3 nm to 6 nm. Nickel loading affects catalyst activity, stability and carbon formation on the catalyst surface. 20 wt% nickel catalyst based on alumina with 86% acetone conversion rate and 74% hydrogen yield at 550°C temperature was selected as the optimal catalyst. Then, loading of 5% by weight of chromium, cobalt, manganese and cerium metals was done to determine the appropriate enhancing metal and chromium was selected as the enhancing metal. Amounts of 3, 5 and 7% by weight of chromium were loaded on the catalyst of 20% by weight of nickel based on alumina. By increasing the chromium content from 3 wt% to 7 wt%, the specific surface area of the catalyst decreased from 123.6 m2/g to 112.7 m2/g. The catalyst with 5 wt% chromium content with 96% acetone conversion and 76% hydrogen yield at 550 °C temperature was selected as the optimal catalyst. Choosing chromium as an enhancer improved the stability of the catalyst and reduced the amount of carbon formed compared to the 20 wt% nickel catalyst based on alumina. Process tests were performed at different reduction and calcination temperatures, as well as space velocity (GHSV) and different steam-to-acetone ratio with 20 wt.%Ni/Al2O3 catalyst and the results were analyzed. To investigate the effect of calcination temperature, the samples were synthesized at three temperatures of 600, 700 and 800 °C under the same conditions. The result of process tests showed that the sample calcined at 600°C shows the best performance with 100% conversion at 550°C. From the results of BET analysis, it was found that the specific surface area of the catalyst decreases with the increase of calcination temperature. To investigate the effect of regeneration temperature, the samples were regenerated at 500, 600 and 700°C for 2 hours and the regenerated catalyst showed better performance at 700°C regeneration temperature with 86% acetone conversion. The performance of the catalyst was compared with steam to carbon molar ratios of 4, 6, and 8, and the best performance was obtained in the molar ratio of 8 with 100% conversion at 550 °C. Also, the activity of the catalyst was investigated in three space velocities of 12000, 18000 and (mL/g.h) 24000. The performance of the catalyst was higher at a space velocity (mL/g.h) of 12000 with 90% conversion at a temperature of 550°C. XRD, TPR, TPO and BET analyzes were used to determine the physical and chemical characteristics of the synthesized catalysts.
