Catalytic Enhancement of Cyclohexene Hydration by Ga-Doped ZSM-5 Zeolites

Abstract

Ga-doped ZSM-5 zeolites were directly synthesized by a facile one-step hydrothermal method without organic templates and calcination and then investigated in the cyclohexene hydration reaction. The structure, component, textural properties, and acidity of the as-prepared samples were examined by X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray fluorescence (XRF), Brunauer–Emmett–Teller (BET), ammonia temperature-programmed desorption (NH 3 -TPD), pyridine-chemisorbed IR (Py-IR), and 71 Ga, 27 Al, 29 Si, and 1 H magic-angle spinning (MAS) NMR techniques. The characterization results showed that the introduction of Ga atoms into the ZSM-5 zeolite framework is much easier than Al atoms and beneficial to promote the formation of small-sized crystals. The number of Brønsted acid sites of Ga-doped ZSM-5 samples obviously increased compared with Ga0-ZSM-5. Additionally, the highest cyclohexanol yield (10.1%) was achieved over the Ga3-ZSM-5 sample, while the cyclohexanol yield of the Ga0-ZSM-5 sample was 8.6%. This result indicated that the improved catalytic performance is related to its larger external surface area, smaller particle size, and more Brønsted acid sites derived from Si–OH–Al and Si–OH–Ga of Ga3-ZSM-5. Notably, the green route reduces harmful gas emission and provides a basis for doping other heteroatoms to regulate the catalytic performance of zeolites, especially in industrial production.

Support Effect of Ga-Based Catalysts in the CO2-Assisted Oxidative Dehydrogenation of Propane

“…According to the literature [1,12,13,15,19,20], Ga-modified zeolites with low SiO 2 /Al 2 O 3 ratio were beneficial for the preparation of olefins over short-chain hydrocarbon dehydrogenation. Therefore, in order to further understand the catalytic role of supports, as can be expected, Ga-modified Na-SSZ-13 (27), Na-SSZ-39(9), Na-ZSM-5 (28), silica and γ-Al 2 O 3 were prepared.…”

“…As shown in Figure 3, all samples displayed major diffractive indices that were identical to the bare zeolites. This signified that the zeolite's crystalline structure of Na-ZSM-5 (27), Na-SSZ-39 (9) and Na-SSZ-13 (28) was not affected by the loading of Ga species and the absence of any structural alteration upon metal incorporation. Ga/Na-ZSM-5 (28) Na-ZSM-5(28)…”

“…In recent years, Ga-based catalysts have attracted considerable attention for their enhancement of dehydrogenation activity [22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38][39]. The dehydrogenation reaction is generally considered to be catalyzed by the synergistic effects of metal sites and support.…”

Effect of Ga substitution with Al in ZSM-5 zeolite in methanethiol-to-hydrocarbon conversion

“…Such a spherical shape has been reported in Ga-substituted ZSM-5. 14,15 This morphology could be attributed to the deposition of small crystals from secondary nucleation on top of the initially formed larger units, retaining the contours of the original morphology. 16 When Si/Ga exceeded 200, the particle size gradually decreased to around 0.8 mm and the shape became a typical-hexagonal crystals of MFI-type zeolite.…”

Synthesis of Hierarchical ZSM‐11 Nanorods Aggregates and Catalytic Properties in Cyclohexene Hydration to Cyclohexanol

“…ZSM-11 nanorods aggregates was synthesized from a mixture with the molar composition of 4Na 2 O: 100SiO 2 : 2.9 Al 2 O 3 : 0.15TBAOH: 2.5S-2: 2500H 2 O: xCTAB (x = 0, 0.5, 1, 1.5, 2 and 2.5). In a typical [37] 10.8 99.0 ZSM-5-0.5 [34c] 13.0 99.3 Ga3-ZSM-5 [38] 10.1 99.0 ZSM-5-0.2 [39] 12.8 99.3…”