چكيده به لاتين
Abstract
Recently, considerable attention has been paid to synthesis gas production by dry reforming of methane (DRM). In view of the environmental protection as well as potential industrial application aspects. The major drawback of this process up to now remains the rapid deactivation of the catalysts originating from the sintering of the metal active sites as well as the carbon deposition. Due to nickel's availability and lower price compared with that of noble metals, it is most frequently reported metal in DRM. In this thesis, Ni-MgO-Al2O3 nanocatalysts with MgO/Al2O3 = 1 (for MgAl2O4 formation) prepared by co-precipitation method was employed in DRM for the production of syngas and the effect of nickel content, feed ratio and GHSV on the activity of different catalysts were investigated. The characteristic properties of the prepared catalysts indicated that the samples possessed high specific surface area (about 190 m2.g-1) and nanocrystalline structures. The results demonstrated that methane and carbon dioxide conversion and coke formation are significantly increased with increasing the nickel content and conversion and coking of 15 wt.% Ni-MgO-Al2O3 was higher than that of other catalysts. In addition, all these prepared catalysts (except 15 wt.%) exhibited a very high stability without any decline in CH4 and CO2 conversion over the 700 min time on stream. The loss in CH4 conversion for 15 wt.% NMA catalyst is about 3% during the time on stream. To compare the synthesis method, 12.5 wt.% Ni/MgAl2O4 catalysts was prepared by impregnation and employed in DRM. The results revealed that impregnation method improved the catalytic activity and reduced the stability. In this work, the effect of CeO2 loading and synthesis method of the 12.5 wt.% NMA promoted catalysts were studied. The obtained results showed that the CeO2 reduced the coke formation of the prepared catalysts and the 3CeO2-12.5NMA (prepared by impregnation) catalyst exhibited the minimum coke formation.
Key words: synthesis gas, dry reforming, nickel catalyst, co-precipitation, impregnation, coke formation, promoter, cerium oxide
