Performance of Ni/Si-MCM-41 catalysts in dry methane reforming for H2 generation: analysis of TEOS and rice husk ash as sources of silica in the preparation of the catalytic support

ABSTRACT

Hydrogen is a product of great industrial appeal, especially when it comes from a renewable chain with low environmental impact. Aiming to reduce costs related to the preparation of the catalysts used to obtain H₂, the present work aimed to evaluate the influence of two different supports of Si-MCM-41, synthesized from two different silica sources (one commercial, tetraethyl orthosilicate – TEOS and the other residual, rice husk ash silica – CCA), on the performance of nickel catalysts when applied in the dry methane reforming reaction (RS). The catalysts were synthesized with 20% (w/w) nickel through wet impregnation and were characterized by the techniques of SEM/EDS, physisorption of N₂, XDR, FTIR, TPD–NH₃ and TPR. The reaction essays were conducted in a fixed bed reactor, at 800 ºC for 24 h. The results of the characterization of the material showed that the catalyst synthesis was efficient. The catalysts showed significant structural differences when dealing with the different sources of silica used in the synthesis of the catalytic support, which differences were more evident in the specific area and in the pore diameter of the materials. This difference may be related to the morphological difference of the catalytic support that directly influences the way in which the active phase will be arranged on the surface of the catalyst. The evaluation of gaseous products, carried out by gas chromatography, showed very similar conversion and selectivity results for the two catalysts, leading to conversions of 45% H₂. The formation of coke in the catalyst in which the precursor support was synthesized from CCA was significantly lower. In this sense, CCA stands out as a promising substitute for TEOS in the synthesis of catalytic supports for high performance nickel catalysts when applied in RS.

Keywords
Si-MCM-41; dry methane reform; hydrogen; rice husk ash silica