Ethanol Conversion Catalyzed by MCM-22 and Its Dealuminated and Delaminated Forms

The conversion of ethanol into hydrocarbons, particularly into light olefins, was studied over MCM-22 zeolite in their acid form (HMCM-22) and its derived forms obtained by dealumination with oxalic acid (HMCM-22(OA)) and delamination (HITQ-2). The treatment with oxalic acid did not affect zeolite textural properties but reduced the total density and strength of the acid sites. As to the delamination process, HITQ-2 zeolite presented the highest Brunauer, Emmett and Teller (BET) specific area, mesopore volume, and external area, but the microporosity was not affected. This sample showed a lower SiO₂/Al₂O₃ ratio than the precursor HMCM-22, resulting in the highest acid site density but with the predominance of acid sites with weak and intermediate strength. Both dealumination and delamination led to an increase in the number of structural defects in the samples. The comparison of the catalytic performance at 500 ºC showed that despite the differences in the acidic and textural properties of the samples, they were active for ethanol conversion and highly selective for ethylene production. Ethanol conversion, followed by in situ diffuse reflectance spectroscopy (DRIFTS), was also investigated. It showed that, for both samples, the “coke band” intensity was already significant after 1 min of reaction, similar to what was detected for HMCM-22.

Keywords:
ethanol conversion; MCM-22; ethylene; DRIFTS in situ; coke; ITQ-2