Enhancing the Catalytic Properties of Mordenites via an Alkali–Acid Treatment and by Loading Nickel–Cerium during o-Ethyltoluene Isomerization

Abstract

The catalytic performance of the selective isomerization of oethyltoluene (O-ET) is crucial to increasing the m-ethyltoluene (M-ET) and pethyltoluene (P-ET) yields. During the isomerization of O-ET, traditional (commercial) mordenites (HM) are generally limited by a high reaction temperature (235 °C), as well as a low yield of the isomerization product (49.0%). In this study, micro-mesoporous mordenites were obtained by treating commercial mordenites with NaOH, NaOH−HNO 3 , and NaOH−mixed acid (HNO 3 −oxalic). Thereafter, their structure, porosity, and acidity were investigated via X-ray diffraction, transmission electron microscopy, inductively coupled plasma, N 2 sorption, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy of pyridine, temperature-programmed desorption of ammonia, and nuclear magnetic resonance. Among the various treated samples, the accessibility of the acidic sites and the B/L value of the alkali− mixed HNO 3 −oxalic one were enhanced, achieving the highest yield (53.6%) and lowest reaction temperature (165 °C), thus significantly reducing the energy consumption of the reaction process. Furthermore, Ni and Ce were successfully loaded via the incipient wetness impregnation of the micro-mesoporous mordenite to significantly prolong the catalytic life. This study affords a new strategy for obtaining high M-ET and P-ET yields from the isomerization of O-ET in mixed C 9 aromatics on an industrial scale.

Comparison of surface passivation modification of two mordenite zeolites and their application on the isomerisation of o-ethyltoluene

“…Possible mechanism for the isomerisation of ethyltoluene. According to the characterization above and catalytic performance results in Table 4, as well as our previous work, 14 the possible mechanism for the isomerisation of O-ET is presented in Fig. 13.…”

“…According to previously reported procedures, 14 the commercial mordenite (labelled as HM) was refluxed in a 0.2 M sodium hydroxide (NaOH) solution for 1.0 h at 75 °C (25 mL solution per 1 g mordenite). The mordenite was filtered, washed to pH 7, and ion-exchanged with 1.0 M ammonium chloride (NH 4 Cl).…”

“…In our previous work, 14 the optimal reaction temperatures for HM and HM-M were 235 °C and 165 °C, respectively. Thus, the discussed temperature of HM and modied zeolite is 235 °C, and that of HM-M and modied zeolite is 165 °C in this study.…”

“…[10][11][12][13] To solve these challenges, low-temperature micro-mesoporous mordenite (HM-M) was prepared via alkali-acid post-treatment by our group previously. 14 HM-M has a large specic surface area, high accessibility of acid sites in the pores, and short diffusion channels, which can achieve high-efficiency conversion of O-ET at low temperatures and improve catalyst deactivation. Therefore, hierarchical-pore mordenite has broad application prospects in O-ET isomerisation.…”

Dealumination and Characterization of Natural Mordenite-Rich Tuffs

“…Several groups have reported on the use of mordenite as a catalyst support, aiming to produce effective catalysts. Cao et al [12] employed alkali-acid treatment to commercial mordenites in order to improve their catalytic properties for the isomerization of ethyltoluene using Ni-Ce as the active species. No structural damage to the zeolite was found after such relatively strong chemical treatment.…”