Promoting effect of dual modification of H-ZSM-5 catalyst by alkali treating and Mg doping on catalytic performances for alkylation of benzene with ethanol to ethylbenzene

Abstract

Alkali-treated HZSM-5 zeolite (AT) was modified with Mg species to produce combined modified HZSM-5 catalyst (Mg-AT) for alkylation of benzene with ethanol to ethylbenzene. The catalysts were tested and characterized by X-ray diffraction (XRD), NH 3 -Temperature Programmed Desorption (NH 3 -TPD), Nitrogen adsorption-desorption, Magic angle spinning nuclear magnetic resonance (MAS NMR) andScanning Electron Microscope (SEM) techniques. The characterization results showed that for the combined modified HZSM-5 sample, the ratio of surface area of mesopores to the total surface area was the highest. The Mg (1 wt%)-AT catalyst was found to exhibit the highest activity (30% of the conversion of benzene) and selectivity to EB (92%) for the reaction, which was confirmed to be due to the proper L/B acid proportion (3.79) and the improvement of the mesopores of the catalyst.

Insights into the production of upgraded biofuels using Mg‐loaded mesoporous ZSM‐5 zeolites

“…[26] As mentioned above, (Mg 2 + OH À ) + species are significantly decreased for MgHZ25-5, since these species could condense to form MgO at high Mg loadings. [26] Therefore, although the number of Mg species available at specific exchange sites in the internal zeolitic structure are decreased for MgHZ25-5, MgO species could be formed within the internal mesoporosity. This is in agreement with XPS data, where an internal zeolite structure enriched in Mg 2 + species was detected (see Table 1).…”

“…[24a,25] 4-coordinated Al is found within the zeolite framework (Framework Al, FAL), whereas the 6coordinated species belong to extra framework Al species (Extra Framework Al, EFAL). [26] Therefore, the 27 Al NMR spectra of HZ25 would suggest, that whilst there are no EFAL species in the parent zeolite, these species are formed by means of a dealumination process after Mg impregnation, [17,27] and they are more apparent for MgHZ25-1. This agrees with XRD data, where a framework distortion is observed for this sample, and also with N 2 adsorption results, since mesoporosity is preserved or even slightly increased in comparison to the parent mesoporous acidic zeolite (from 0.38 to 0.41 cm 3 /g).…”

“…This agrees with XRD data, where a framework distortion is observed for this sample, and also with N 2 adsorption results, since mesoporosity is preserved or even slightly increased in comparison to the parent mesoporous acidic zeolite (from 0.38 to 0.41 cm 3 /g). It should be pointed out, that since EFAL can account for both Bronsted and Lewis acidity, [26] the acidity of this sample will be significantly modified. In the case of the HZ40 series, both 6-coordinated EFAL and 4-coordinated FAL species are present in the unmodified zeolite, being their intensity reduced as Mg loading was increased.…”

“…These results agree with the results from MAS NMR and further strengthen the argument that the presence of (Mg + OH À ) + at the specific exchange sites results in a decrease of the number of Brønsted acidic sites. [17,26] Table 2 summarizes the number of Lewis (C L ) and Brønsted acidic sites (C B ) of some key zeolite catalysts. In line with TPD-NH 3 data, the HZ25 acidic zeolite was characterized by a marked quantity of C B , having the highest value of 244 μmol/g, about two-fold that found for HZ40 (105 μmol/g).…”

Electrophilic aromatic substitution over zeolites generates Wheland-type reaction intermediates

“…Moreover, if aromatics can also be derived via depolymerization of lignocellulosic biomass materials (instead of fossil fuel) in future, then the complete EB process would be absolutely renewable 19 . Thus, the zeolitecatalysed EB process has recently captured renewed attention in both academia [16][17][18][19][20][21][22][23][24][25][26] and industry 16,[27][28][29][30] . In this work, we establish a fundamental understanding on the reaction mechanism of the commercially relevant, zeolite-catalysed, …”