Activity Of ZSM-5 Zeolites Research Articles

Catalytic hydrocracking reactions of tetralin biomass tar model compound to benzene, toluene and xylenes (BTX) over metal-modified ZSM-5 in ambient pressure reactor

The tetralin hydrocracking process into benzene, toluene, and xylenes (BTX) was investigated over metal-modified (Ga, Nb, Ni, NiMo, Sn, W, Zr or H3[P(W3O10)4])/ZSM-5 zeolite catalysts without sulfidation procedures, mechanism was analyzed, and compared with a pristine microporous material in a packed bed reactor under applied atmospheric pressure (p). This experimental study presents an investigation of the metal-promoted ZSM-5 for the BTX production under the ambient p for the first continuously-operated time. It is demonstrated that metal-wise there are no significant improvements in the formation of BTX. The yield of 43.1 mol% towards BTX over the parent HZSM-5 (SiO2/Al2O3 = 30) at 420 °C after 4 h on time on stream (TOS) was achieved, while methane, ethylene, ethane, propylene and propane were main gas products. The outstanding functional performance of HZSM-5 was mainly ascribed to structure, its high dealkylation and a measured large amount of the solid surface area in tandem with the porosity, protonating total Brønsted (BAS)/Lewis (LAS) acidity and BAS/LAS ratio. However, BTX dropped drastically with increasing TOS due to coke. It was found that HZSM-5 was the most affected within studied reaction conditions, but could be easily regenerated with preserving realistic catalytic chemistry. The pathway of cracking was proposed. Simultaneously, the 5wt%Zr/ZSM-5 catalyst possessed the highest selectivity (SBTX = 24.2 mol%; TOS = 25 h; 370 °C) due to the low diffusion thermomigration of the Zr species into framework compared to parent zeolite under the same reaction conditions after a long TOS. Influence of metal loading on the activity of ZSM-5 zeolite was systematically studied and the complex relationship between physicochemical properties and catalytic activity of bifunctional catalysts was observed. All these findings shed light, on how the incorporation of different metals affects BTX selectivity.

Pressure Boosts the Aromatization Activity of Zsm-5 Zeolite During Lignocellulose Catalytic Pyrolysis

Pressure Boosts the Aromatization Activity of Zsm-5 Zeolite During Lignocellulose Catalytic Pyrolysis

The influence of molybdenum loading on activity of ZSM-5 zeolite in dehydroaromatization of methane

Mo/ZSM-5 type catalysts prepared by different methods of loading the same quantity of molybdenum were tested by methane dehydroaromatization. The catalyst samples were impregnated with ammonium molybdate in different ways: by standard wet impregnation method (WIM), by wet impregnation combined by the treatment in rotavapour (RV), by wet impregnation assisted by ultrasound (US) or by microwave (MW) irradiations. The fifth catalyst was prepared by mechanical mixing of zeolite with ammonium molybdate (MM). Prepared catalysts were characterized by X-ray diffraction (XRD), Fourier-Transform Infra-Red Spectroscopy (FTIR), Temperature Programmed Desorption of Ammonia (TPDA), Scanning Electron Microscopy (SEM), Field-Emission Scanning Electron Microscopy (FESEM), Transmission Electron Microscopy (TEM) and by physical adsorption of nitrogen. The strength of the acid sites was compared in the n-hexane cracking. It has been revealed that the sample impregnated with assistance of microwaves had the highest activity in methane conversion. For this sample the finest dispersion of molybdenum species was observed in TEM-pictures, and other characteristics showed the highest intrusion of molybdenum into zeolite pores and their association with Brønsted acid sites. The lowest activity showed the catalyst prepared by mechanical mixing (MM), followed by the catalyst prepared by simple wet impregnation method (WIM). Samples RV and US had higher activities as sample WIM but lower than MW.

On the nature of acid centers in Mg-containing ZSM-5 zeolites

The catalytic activity of ZSM-5 zeolites containing Mg cations in various concentrations has been studied in the alkylation of toluene by ethylene. The concentration of acid centers of different nature in these zeolites was characterized by IR spectroscopy of OH-groups and adsorbed CO. The state of Mg cations in the samples was studied by15N NMR of the adsorbed N2O. The increase of Mg content was shown to decrease both the concentration of non-protic acid sites of medium strength and the activity of samples, which is related to the increase of association degree of Mg cations in the zeolite.