Ce-impregnated acid functionalized mesoporous silica as catalyst for ethanol dehydration to ethylene

The catalytic performance of Ce-containing mesoporous silica, functionalized with phenylsulfonic and phenylsulfonic/phosphonic acid groups, was studied for the ethanol dehydration to ethylene reaction in the temperature range of 250 degrees C-500 degrees C. The SBA-15-type materials were prepared using a 'one-pot' hydrothermal method, and for comparison, the performance of a silica gel with grafted alkylsulfonic groups was also studied. The initial silica supports and Ce-containing catalysts were characterized by XRD, XPS, TEM, SEM/EDX, TGA, zeta potential measurements, etc. The characterization results showed that the morphology, structure, thermal and textural parameters of the catalysts remained largely unchanged following the impregnation of 0.1 M Ce3+ ions. The nature, amount, and availability of acid groups in the mesoporous framework were identified as key factors influencing the metal-impregnation process. According to DRIFT-IR spectroscopy, the functionalization with sulfonic groups binding Ce3+ ions led to the generation of Br & oslash;nsted (B) and Lewis (L) acid sites, respectively. Importantly, the thermal stability analysis revealed that the number of strong B-sites rapidly diminished during desorption up to 500 degrees C, resulting in a notable decrease in the B/L ratio after treatment at high temperatures. At the same time, ethanol conversion and selectivity towards ethylene were found to augment with increased reaction temperature to 500 degrees C. The SBA/PhSO3H/Ce catalyst demonstrated superior overall performance, characterized by high ethanol conversion (95 %) and the most favourable kinetic profile, including the lowest activation energy (48.2 kJ/mol) among all materials. In contrast, the Ce-containing SiO2SO3H/Ce catalyst exhibited the highest TON (5223.6 per hour), indicating superior intrinsic efficiency per active site. The reusability of the obtained catalysts in terms of stability and conversion was explained using a range of instrumental methods.