چكيده به لاتين
Reframing fossil fuels to convert natural gas into synthesis gas is an important process in the refining industry. Combined steam and dry reforming of methane is an alternative operation for producing synthesis gas with a suitable ratio of H2/CO, which has advantages such as avoiding the additional costs required for separating O2 from air or separating CO2 from biogas and reducing the formation of carbon on the catalyst..The active metal nickel has been chosen as the catalyst of this process due to its high activity, suitable selectivity, availability, cheapness, and long life, along with aluminum oxide, which contributes to thermal and mechanical stability and high absorption.
In this research, 10 wt% nickel catalyst based on alumina has been synthesized by 4 methods: mechanical-chemical, co-precipitation, impregnation and combustion. Mechanical-chemical method with specific surface area of 229.14 m2/gr and methane conversion percentage of 85% at 750 °C and feed ratio of 5/0/5/0/1 H2O=/CH4/CO2 has the highest catalytic activity and has been chosen as the suitable synthesis method for further work. Then different amounts of 5, 10, 15 and 20% by weight of nickel were loaded on the alumina base by mechanical-chemical method. 15%Ni/Al2O3% catalyst showed the highest activity at 750°C with a methane conversion rate of 91%. Then, in order to improve the performance, the amount of 5% by weight of iron, chromium and manganese metals as enhancers along with 15% nickel, in the feed ratio of 0.5/0.5/1 H2O=/CH4/CO2 was investigated. Among these compounds, chromium promoter was chosen as a suitable promoter due to less carbon formation. Then different amounts of chromium loading (5,3 and 7) were investigated. The loading of 7% by weight of chromium showed the best performance with less coke formation and the highest methane conversion with a rate of 80.74 at a temperature of 750 degrees Celsius. The chemical and physical characteristics of the prepared catalysts were determined using TPR, TPO, XRD and BET analyses. In addition, the optimal catalysts were examined under operating conditions such as gas space velocity, feed ratio, reduction temperature, calcination temperature and also stability.
Key words: reforming, synthesis gas, nickel active metal, nickel alumina catalyst, mechanical-chemical, co-precipitation, impregnation and combustion
