The interaction characteristics controlling dispersion mode-catalytic functionality relationship of silica–modified montmorillonite-anchored Ni nanoparticles in petrochemical processes

Abstract

This study has dealt with different interaction events during the synthesis of silica-modified montmorillonite (SMM) nanocomposites. TEOS precursor was intercalated into the clay (M) gallery (in M/TEOS mass ratios = 1:2 and 1:6), assisted by dodecylamine (DDA) or CTAB driving agents (at constant surfactant/M ratio = 1.8). Ni NPs (of 2, 4, 6 wt%) were immobilized into the gallery of H-SMM sample (M/TEOS = 1:6). Various characteristics were studied via XRD, EDX, FTIR, N2 physisorption, H2-pulse titration, DSC-TGA, TEM and DLS techniques. The formed Silica NPs were attached on platelet surface through the interaction with edge aluminol sites in octahedral sheet. Considerable delamination of clay platelets was observed by increasing the M/TEOS ratio and in presence of CTAB, exhibiting higher surface area and pore parameters. Ni NPs were anchored onto the bonded silica at clay layer edges through interactions involving DDA, interlayer sites and silica NPs. Ni nanocatalysts were tested in ethyl benzene (EB) conversion, considering possible reaction pathways according to various interaction events affecting the catalytic behavior. TOF of the reaction to selectively produce styrene remained constant with Ni loadings, suggesting that dehydrogenation pathway is structure insensitive. The constancy of TOF to produce optimized quantities of benzene favored the involvement of edge interlayer acid sites in cracking pathway, independent of Ni NPs content. TOF to selectively produce ethane in cracking pathway increased with Ni loading, where enlarged surface Ni NPs (reaching to 202 nm) seemed to control this structure sensitive pathway.