Mechanistic insight to acidity effects of Ga/HZSM-5 on its activity for propane aromatization

Abstract

Mechanistic insight to the synergistic effect between Brønsted acidity and strong Lewis acidity of Ga/HZSM-5 on propane aromatization activity.

A strategy to convert propane to aromatics (BTX) using TiNp4 grafted at the periphery of ZSM-5 by surface organometallic chemistry

“…1A). 1,[31][32][33][34] The fresh catalyst [Ti/ZSM-5] (1) was further analyzed by multinuclear solid-state NMR to provide detailed information on the molecular structure of the grafted Ti complex. 35 The 1 H NMR spectrum exhibited a significant broad signal at 1.2 ppm arising from protons of the neopentyl ligand: the methyl (-CH 2 C(CH̲ 3 ) 3 ) fragments of the neopentyl ligand and the methylene protons (-CH̲ 2 C(CH 3 ) 3 ) ( Fig.…”

“…† [37][38][39] Table 2 summarizes the calculated concentration of BAS and LAS obtained after the FT-IR pyridine adsorption for the [Ti/ZSM-5] and [H-ZSM-5 300 ] catalysts. 37,[40][41][42] Table 2 shows that the number of Brønsted acid sites (BAS) increases from 69 µmol g −1 for [H-ZSM-5 300 ] to 146 µmol g −1 for the grafted catalysts Ti. The increase of the number of Brønsted acid site maybe due to the generation of new acid species after the grafting of TiNp 4 .…”

“…Aromatics, especially Benzene, Toluene and Xylenes (BTX), are important chemicals, which are extensively used in the production of styrene, phenol, polymers, plastics, medicines, rubbers and others. Catalytic cracking/reforming of naphtha can lead to aromatics processes using ZSM-5 catalysts [1][2][3][4][5] The aromatization reaction of light alkanes, such as ethane, propane or n-butane, are important catalytic reactions for the academic community as it represents an example of a complex and multistep reaction requiring a multi-functional catalyst. This process is also used industrially to upgrade light alkanes such as ethane, propane and butane in the petroleum refinery.…”

Aromatization over nanosized Ga-containing ZSM-5 zeolites prepared by different methods: Effect of acidity of active Ga species on the catalytic performance

“…Ausavaukhi et al [13] prepared a series of Ga-containing ZSM-5 zeolites via impregnation and physical mixing and determined that the GaO + species act as stronger Lewis acid sites. Xiao et al [14,15] also reported that the extraframework GaO + species in impregnated ZSM-5 samples can react with the acidic protons of the zeolite framework and contribute to a strong Lewis acidity, which is favorable for dehydrogenation during propane aromatization under a N 2 atmosphere. Rodrigues et al [16,17] studied the nature and activity of gallium species for the aromatization of propane under H 2 and concluded that the reduced gallium species, which were obtained via hydrogen reduction of GaO + species (GaH 2 + ), in the impregnated ZSM-5 zeolites serve as the actual active sites for propane activation.…”

“…Rodrigues et al [16,17] studied the nature and activity of gallium species for the aromatization of propane under H 2 and concluded that the reduced gallium species, which were obtained via hydrogen reduction of GaO + species (GaH 2 + ), in the impregnated ZSM-5 zeolites serve as the actual active sites for propane activation. Therefore, to promote the formation of more active Ga species with a high dehydrogenation activity, several methods have been developed (e.g., reduction/oxidation cycles, acid impregnation and treatment with steam), and the results indicate that samples modified via these approaches produced higher aromatic yield [14][15][16][17][18][19] . Recently, Lai et al [20,21] adopted an optimized combination of mesostructuring and Ga impregnation to increase the GaO + concentration in ZSM-5 channels and promote the outward diffusion of products, which was beneficial for methanol conversion to aromatic compounds.…”