Porosity of CHA Zeolite Driving the Formation of Polyaromatic Coke Species in the Methanol to Olefins Reaction

Abstract

The pore size of the chabazite structure is exceptionally suitable for the methanol to olefins (MTO) reaction. The reaction has an induction period required for the formation of a hydrocarbon pool (HP), usually composed of aromatic compounds of different sizes. HP is alkylated by methanol and afterward cracked, leading to the formation of olefins. Despite the importance of HP, its formation and growth in size are exceedingly dependent on the porosity of the catalyst. The ideal is that the formed HP remains stable throughout the reaction because the growth in its size causes blockage of the small catalyst pores, decreasing its capacity. Herein we studied chabazite zeolites with different porosity and structure, caused by variation in the particle size and pores’ volume. Porosity influenced the formation of HP species in quantity (as revealed by thermogravimetric analysis (TGA)) and polymerization degree (gas chromatography coupled with mass spectrometer (GC-MS) analysis) and, consequently, the MTO reaction’s performance.

Influence of Substrate Concentration on Kinetic Parameters of Ethanol Dehydration in MFI and CHA Zeolites and Relation of These Kinetic Parameters to Acid–Base Properties

“…This assumption is supported by the SEM images of both samples, where the particles of the CHA-14 sample are smaller and more polydisperse than particles of the CHA-7.5 sample. The volume of micropores and the BET area for our samples correspond to previously published values for MFI [42,43] and CHA zeolites [44,45].…”

“…Desorbed compounds in outlet gas were detected using the mass spectrometer OmniStar GSD 320 (Pfeiffer Vacuum GmbH, Aßlar, Germany). Masses m/e = 4, 17,18,26,28,29,31,32,44,45,46,59 and 74 were simultaneously monitored. Response factors for ethanol, ethylene and diethylether to these masses were obtained by syringe calibration doses of pure compounds.…”

Boron Incorporation by Hydrothermal Synthesis Into SAPO-5 and SAPO-11 Molecular Sieves

“…SAPOs are zeotypes that emerged from the introduction of silicon in the structure of aluminophosphates, showing a high tolerance to incorporation of cations that silicoaluminophosphates have, as well as their moderate acidity, highly effective in methanol to olefin (MTO) conversion reactions [5][6][7][8] and hydroisomerization of alkanes [9][10][11][12] .…”

Adsorption of Arsenic, Lead, Cadmium, and Chromium Ions from Aqueous Solution Using a Protonated Chabazite: Preparation, Characterization, and Removal Mechanism

“…The superficial zeolite modification using NH 4 Cl and a subsequent thermal treatment have been utilized to tailor synthetic chabazites for the thermal degradation of high-density polyethylene to low molecular mass hydrocarbons [40] and the adsorption of ethane (41 mg/g) and propane (81 mg/g) [41]. This material had been also employed as a catalyst in the methanol to olefins reaction (forming polyaromatic coke species) [42]. However, this approach has not been applied to improve the chabazite properties for the adsorption of anionic pollutants from water.…”