Aluminum distribution in Ferrierite zeolites influences the performance of methane oxidation

Transition-metal-free aluminosilicate FER-type zeolite has been demonstrated to effectively catalyze methane to methanol using N2O as the oxidant with distorted tetra-coordinated aluminum (AlIV-2) and penta-coordinated aluminum (AlV) as potential active sites. However, the specific effects of Al distribution on the active Al species have not been thoroughly investigated. Herein, aluminosilicate FER-type zeolites with controllable Al distribution were developed. Al distribution, including the arrangement and location of Al atoms, was characterized using 27Al MQMAS/MAS and 29Si MAS NMR spectra. The arrangement of aluminum, particularly the isolated Al and paired Al in as-synthesized samples, influenced the proximity between oxidative and acidic sites in H-type samples. Al locations involved the specific positioning of bifunctional sites and affected the final product. The increased CH4 conversion at 250-275 °C of FER zeolite with Al preferential population at T4 sites confirmed the higher activity of Al species from T4 sites. Additionally, a higher proportion of Al atoms in 10-ring channels facilitated the tandem conversion of methane to methanol on oxidative sites, followed by methanol to hydrocarbons on acidic sites at 300-375 °C. This study corroborated and expanded upon our recent research and highlighted the significant impact of Al distribution in FER zeolite on methane oxidation.