Transformation of Isobutyl Alcohol to Aromatics over Zeolite-Based Catalysts

Abstract

One-step transformation of isobutyl alcohol to aromatics (benzene, toluene, and xylene) has been studied in a gas phase, fixed-bed reactor system over several purely acidic zeolites and zeolite-supported metal catalysts. ZSM-5 zeolites give higher aromatics yields (∼42 wt %) among the evaluated zeolites, and the Si/ Al ratios (Si/Al = 13−43) of ZSM-5 slightly influence their catalytic performances. During the transformation of isobutyl alcohol, large amounts of short alkanes (mainly propane and butane isomers) are also generated on the acidic ZSM-5. To improve the conversion to aromatics, several metal species (Zn, Ga, Mo, La, Ni, Ag, and Pt) are supported on the ZSM-5. The enhancements in aromatics yields (∼60 wt %) are observed only on the Zn/ZSM-5 catalysts. The incorporation of Zn species preferentially decreases the strong-strength Brønsted acidity and, thus, suppresses the cracking to C 3 fragments. Moreover, mainly the Zn species at the exchange sites facilitate the recombinative desorption of H 2 and, hence, enhance the reactions toward aromatics. Through these effects, Zn/ZSM-5 catalysts exhibit the remarkably promoted formation of toluene and xylene and inhibit the generation of undesired alkanes products.

Effect of Zn/ZSM-5 and FePO4Catalysts on Cellulose Pyrolysis

“…In good agreement with the results [23,31], different Lewis acid sites were also formed in our Zn/ZSM-5 samples, which were evidenced by the two new IR bands of pyridine adsorption (Figure 4). These Zn/ZSM-5 catalysts with different Zn contents might exhibit various selectivity toward furan derivatives such as furfural and 5-methyl-2-furancarboxaldehyde, together with the different degradation activity of anhydrosugars during the catalytic pyrolysis of cellulose.…”

“…cations, multinuclear oxygenated Zn clusters, and bulk ZnO aggregate [23,31]. In good agreement with the results [23,31], different Lewis acid sites were also formed in our Zn/ZSM-5 samples, which were evidenced by the two new IR bands of pyridine adsorption (Figure 4).…”

“…Figure 2 presents the NH 3 -TPD results of H-ZSM-5 and Zn/ZSM-5 catalysts with different Zn contents. Two desorption peaks around 215 and 440 ∘ C were observed for H-ZSM-5, which were assigned to weak acid sites and strong acid sites, respectively [31]. After loading Zn ions, the peaks at 215 and 440 ∘ C decreased for the three catalysts.…”

“…Figure 3 shows the IR spectra in the range of 1400-1600 cm Zn/ZSM-5 at different desorption temperatures. Three strong peaks are observed at 1450, 1490, and 1540 cm −1 , which are attributed to pyridine adsorbed on Lewis acid sites, Lewis and Brønsted acid sites, and Brønsted acid sites, respectively [31]. The Brønsted acid sites of the catalysts are derived from charge compensated hydrogen protons located at cationic ion-exchange sites of zeolite [31].…”

“…Three strong peaks are observed at 1450, 1490, and 1540 cm −1 , which are attributed to pyridine adsorbed on Lewis acid sites, Lewis and Brønsted acid sites, and Brønsted acid sites, respectively [31]. The Brønsted acid sites of the catalysts are derived from charge compensated hydrogen protons located at cationic ion-exchange sites of zeolite [31]. It is obvious that the three bands are relatively stable even at temperature greater than 400 ∘ C, which is consistent with the NH 3 -TPD results.…”