Methanol aromatization over Ga-doped desilicated HZSM-5

Abstract

Desilication improves mesoporosity, facilitating migration of hydrated gallium ions into cavities of desilicated Ga/HZSM-5 to form (GaO)+-Brønsted phases. The bifunctional sites promote methanol conversion to aromatics.

Optimizing the Aromatic Product Distribution from Catalytic Fast Pyrolysis of Biomass Using Hydrothermally Synthesized Ga-MFI Zeolites

“…Due to the creation of mesopores in ZSM-5 by NaOH desilication, the catalytic activity and diffusion properties of the zeolites are improved, favoring the production of valuable monoaromatics over undesired polyaromatics relative to the conventional microporous ZSM-5 [19][20][21]. Further impregnation of desilicated HZSM-5 with gallium can promote dehygrogenation and aromatization in methanol to gasoline process [22]. Because Ga-containing MFI zeolite via hydrothermal synthesis produced more valuable monoaromatics than conventional HZSM-5 zeolite impregnated with gallium, we anticipated that direct desilication of Ga-containing MFI zeolite may provide an effective way to enhance biomass conversion and optimize product distribution in CFP.…”

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

“…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.…”

The Role of Non-Framework Lewis Acidic Al Species of Alkali-Treated HZSM-5 in Methanol Aromatization

“…However, this is not the case: with increasing contact time, ABs increased and C 4 -C 7 hydrocarbons decreased for HZ-D and HZ-DA, whereas HZ showed an opposite trend. A possible explanation for the former trend of HZ-D and HZ-DA is that the promotion of secondary dehydrogenation of C 4 -C 7 hydrocarbons, forming dihydrogen and olefins, and subsequently transformed the yielded olefins into ABs [19,20]. As for the latter trend of HZ, the cracking of ABs is imperative.…”

“…TPD of methanol was also conducted on the AutoChem II, but was recorded using a quadrupole mass gas analysis system (ThermoStar GSD 320 T, Pfeiffer Vacuum, Aßlar, Germany). Detailed pretreatment and operating conditions of temperature-programmed analyses can be found in recent studies [19,20].…”

“…Mesopores and total volumes increased substantially (more than 100%) for HZ-D and HZ-DA, compensating with minor losses of the total surface area (<5%), the micropore surface area (<17%) and the micropore volume (<17%). Such a trade-off allows the diffusivities of reactants and products to be improved greatly, and is known to have positive effect in aromatics yield in MTA [18][19][20]. Figure 1 displays N 2 isotherms and Barrett-Joyner-Halenda (BJH) mesopore size distributions.…”