Ultrafast surfactant-templating of *BEA zeolite: An efficient catalyst for the cracking of polyethylene pyrolysis vapours

Non-thermal Plasma-Assisted Deconstruction of High-Density Polyethylene to Hydrogen and Light Hydrocarbons over Hollow ZSM-5 Microspheres

“…Coking deactivates zeolites and consequently rises operation costs as either catalyst regeneration or the addition of fresh catalysts is required . Efforts on zeolite catalyst development for gas-phase reactions, in general, have intensively focused on the integration of active metallic sites on zeolites, tuning the Si/Al ratio, and tailoring zeolite acidity properties. − Nevertheless, excited species inside a non-thermal plasma environment have a significantly short life . A catalyst system that can secure an excellent interaction of reactant gases with the catalyst surface/structure is therefore highly desired for plasma-assisted chemical reactions. , In this respect, hollow spheres, in catalytic terms, can offer high specific surface area and discrete voids that deliver abundant accessible surface sites for catalytic reactions. , Further, these so-called “hollow microreactors” can enable excellent reactant diffusion and mass transfer; thus, more reactant molecules can be adsorbed and concentrated on the surface and within the hollow structure to accelerate reactions .…”

Micelle Formation inside Zeolites: A Critical Step in Zeolite Surfactant-Templating Observed by Raman Microspectroscopy

“…Similar findings have also been reported for the mesoporous MCM-41 silica, indicating the presence of micelles in the zeolite crystals. 27 − 29 The sharp resonance at 54 ppm is characteristic of micelled (or trapped) surfactant in the zeolite structure, 28 , 30 whereas the broadening and decrease in the intensity of the peak at ca. 67 ppm is due to the interaction of the surfactant heads with the polar environment inside the zeolitic structure, which changes the chemical environment of the CTAB.…”

“…As expected, the amount of CTA + in the 250−400 °C range was higher in the hydrothermally treated sample, which is related to the formation of the micelles and, subsequently, of the mesoporosity. 12,24 The micellization of the CTA + inside the zeolite and its subsequent effect on the zeolite structure were studied by solid-state 13 C and 29 Si NMR; see Figure 2. The 13 C NMR spectrum of the CTA + -containing zeolite after the hydrothermal treatment is shown in Figure 2A (red).…”

“…(B) Solid-state 13 C NMR of the surfactant-templated zeolite (red) and the CTA + -containing zeolite before the hydrothermal treatment (blue). (C) Solid-state 29 Si spectra of the surfactant-templated zeolite (red), the original NaY (gray), and a physical mixture of NaY and CTAB (black). the CTAB molecules, indicating a similar chemical environment.…”

“…This observation points out the lack of densely packed molecules, suggesting more isolated molecules within the zeolite framework. 30 Solidstate 29 Si NMR spectra were carried out to gain new insights into the changes in the zeolite framework caused by the surfactant-templating treatment (Figure 2C). The original zeolite shows the characteristic peaks associated with the different structural units of the aluminosilicate framework (Si(0Al), Si(1Al), Si(2Al), Si(3Al)) 31 (see Figure 2C), which are very similar to those of the physical mixture.…”