Dry (CO2) reforming of propane over bimetallic Mo-Ni/Al2O3 catalyst: catalyst synthesis and reactor operation

摘要

Hydrocarbon reforming using CO2, a greenhouse gas, as a feedstock has attracted increasing attention due to the benefits of chemical valorisation of natural gas and CO2, which have an adverse impact on the environment. For hydrocarbon dry reforming, where the product stream H2: CO ratio is less than 3, synfuel production is more amenable for downstream methanol and other oxygenated synthesis. Dry reforming of propane has attracted much interest because of the associated lower reforming temperature and lower vapour pressure of propane compared with methane at ambient temperature, which makes it more favourable for fuel cell cars with internal reforming. However, the formation of carbon on Ni catalysts is well known, thus the addition of Mo to Ni would help in mitigating carbon deposition through possible conversion of the Mo oxide to a Mo carbide phase. Several authors reported high activity, stability and carbon resilience of the Mo-Ni catalyst during methane steam and dry reforming. Furthermore, it has been shown that potassium promotion also retards the nucleation of carbon. As a result, the present project investigates both reactor operation and the performance of Mo-Ni/Al2O3 catalyst as well as the effect of K-promotion on propane dry reforming at temperatures of 773 -973 K .The catalysts were prepared using wetness co-impregnation method. Alumina supported bimetallic 5(wt%)Mo-10(wt%)Ni was doped with 2.5 (wt%) K. Various characterization techniques were employed to measure the physicochemical properties of the catalysts. Specifically, N2-physisorption, H2-chemisorption, temperature-programmed calcination (TPC), temperature-programmed reduction (TPR), NH3 and CO2- temperature-programmed desorption (TPD), X-ray diffraction (XRD) and Total organic carbon (TOC) analyses were performed. K-promotion enhanced the BET surface area, pore volume, metal dispersion and metal surface area. XRD analysis of calcined catalysts confirmed the presence of metal oxides. TPD experiments revealed the acid : basic site ratio of 8.3 for Mo-Ni , while K-promotion decreased the value to 7.5 ,suggesting that basicity of the catalyst was improved by K addition.Catalytic reaction studies were carried out in a stainless-steel quartz fixed-bed reactor (ID = 15 mm ID) co-axially placed within a temperature-controlled tubular furnace and loaded with 0.5g of catalyst. Both Mo-Ni and K-containing catalysts were found to be promising for dry reforming of propane due to their high activity and stability under different operating conditions.