Preparation of a hollow HZSM-5 zeolite supported molybdenum catalyst by desilication-recrystallization for enhanced catalytic properties in propane aromatization

Regulation of the Si/Al ratios and Al distributions of zeolites and their impact on properties

“…Thus, alkaline solution treatment of zeolites can remove the Si atoms from the framework, which certainly reduces the Si/Al ratios 142,143 and thus forms the mesopores within the zeolite crystals. 45,[144][145][146][147][148][149][150][151][152] Up to date, the inorganic bases of NaOH 45,100,111,142,[147][148][149][150][151][152][153][154][155] and Na 2 CO 3 145 have been used for the desilication of zeolites. For example, Bjørgen and co-workers produced ZSM-12 with the Si/Al ratios of 13-34 by treating the calcined ZSM-12 (Si/Al = 39) with 0.2 M-0.6 M NaOH solutions at temperatures of 35°C, 65°C, or 85 °C and duration from 15 to 60 min.…”

“…156 Besides inorganic bases, organic bases, such as TBAOH, 154,155 TEAOH, 149,151 and TPAOH, can also be used for the desilication of zeolites and generation of intracrystalline mesopores of zeolites. 146…”

Identifying the Location of Real Active Sites in ZSM-5 Zeolites for Tetralin Conversion into Light Aromatics

“…For a quantitative analysis, the deconvolution of IR spectra has also been carried out, and the absolute areas of each type of hydroxyls are calculated and shown in Table . Five types of −OH moieties in Figure can be discerned, which stand for terminal Si-OH (3735 cm –1 ), Si-OH in the defects (3720 cm –1 ), Al-OH (3680 cm –1 ), Si-OH-Al (3600 cm –1 ), and Si-OH in the silanol nests (mound-shaped peak centering at 3500 cm –1 ), respectively. For the 3735 cm –1 band standing for terminal Si-OH, it is raised from the termination of zeolite matrixes, and its content is related with S ext .…”

Improving the methane aromatization activity and anti-carbon deposition on MCM-22 through nano α-MoO3 modification

“…Mishra et al 10 prepared alkaline modified Mo/HZMS-5, which exhibited an excellent catalytic performance due to the addition of secondary mesoporous pores, promoting the distribution of Mo species in the pores and the generation of more active Mo sites. Xu et al 20 prepared a hollow HZSM-5 supported MoO 3 catalyst with an enhanced diffusion capacity and an optimized acid content, greatly improving the propane conversion, aromatic selectivity, and catalytic stability. Nam et al 21 confirmed that NiO modified Mo/HZSM-5 can enhance the dispersion of MoC x active sites, inhibiting the formation of coke, and improving the catalytic performance.…”