Mechanistic Studies on the Coupled Reaction of n-Hexane and Ethanol Over HZSM-5 Zeolite Catalyst

Abstract

The coupled reaction of n-hexane and ethanol over HZSM-5 zeolite has been, for the first time, investigated with a pulse-reaction system. The catalytic reaction results showed an improvement of the initial conversion activity of n-hexane when ethanol was introduced as co-reactant. The FT-IR analysis revealed that the ethanol molecules adsorbed on Brønsted acidic sites were immediately transformed into surface ethoxy groups, which were active species for converting n-hexane and improving the initial conversion activity of n-hexane by a bimolecular hydride transfer mode. Also, the catalytic tests suggested that alkenes resulting from the transformation of ethanol could not enhance the initial conversion of n-hexane compared to active ethoxy groups at the shortest contact time. A mechanism involving the ethoxy groups was proposed to understand the coupled reaction of ethanol and n-hexane.

Catalytic Compatibility of Methanol with Petroleum Naphtha in Mixed Feeds Used in the Thermal-Catalytic/Steam-Cracking (TCSC) Process for the Production of Propylene and Ethylene

“…This interpretation was in perfect agreement with those given by other authors who investigated the cracking of mixtures of hydrocarbons with methanol [10] or ethanol [13]: methanol or ethanol was adsorbed prior to n-hexane and immediately transformed into surface methoxy or ethoxy groups. According to the same authors, these species acted as the active sites for the conversion of n-hexane and consequently improved the initial activity of n-hexane [12,13].…”

“…According to the same authors, these species acted as the active sites for the conversion of n-hexane and consequently improved the initial activity of n-hexane [12,13].…”

“…In recent years, results of the cracking reaction over ZSM-5 type zeolite that was carried out with ''hydrocarbons-alcohol'' mixed feeds were reported: methanol and hydrocarbons [9], methanol and n-hexane [10], methanol and n-butane [11], methanol and 1-butene [12], ethanol and n-hexane [13]. Two papers on the TCSC of mixtures of gas oil and a short chain alcohol (and particularly methanol) [14], and of light naphtha and methanol [15], were already published by our group.…”

Catalytic Upgrading of Light Naphtha to Gasoline Blending Components: A Mini Review

“…The selective C−C bond formation between methanol/DME and light alkane co-feeds is an attractive option for the upgrading of light naphtha. Liu and co-workers used a pulse reaction system to elucidate the reaction mechanism of n-hexane coupling with methanol 122 or ethanol 123 over MFI (16) at 200−350 °C. Intermediate products (methoxy or ethoxy groups) from the conversion of methanol or ethanol activated n-hexane conversion via a bimolecular hydride transfer.…”

Roles of ethanol in coke formation and HZSM-5 deactivation during n-heptane catalytic cracking

“…Inspired by the success of coupled methanol and hydrocarbon cracking, the co-conversion of ethanol and hydrocarbon has become a hot topic. 23,24 Wan et al 25 studied coupled ethanol and n -hexane cracking over HZSM-5 zeolites with a pulse-reaction system. The adsorbed ethanol at the acid site was readily transformed into surface ethoxy groups, triggering hydride transfer and promoting n -hexane conversion.…”