Effects of Modified Beta Zeolites with Acid on Anisole Acetylation in a Fixed Bed Reactor

Abstract

A beta zeolite sample (Si/Al = 30) was modified by citric acid, tartaric acid, and hydrochloric acid. The catalytic performances of these zeolite together with another beta zeolite (Si/Al = 12.5) were tested in the anisole acetylation in a fixed-bed configuration. The zeolites were characterized by powder X-ray diffraction, FT-IR of adsorbed pyridine, and temperature programmed desorption of ammonia. The ratios of Si/Al, the specific surface areas, and the pore sizes were also measured. The results showed that the most active and stable behavior was achieved on the HCl treated zeolite. The strong acid sites as many as possible but with an appropriate concentration and strength were needed in order to obtain an optimum activity and stability.

Determination of different acid sites in Beta zeolite for anisole acylation with acetic anhydride

“…2 Theta (degree) acylation [1]. According to the physicochemical properties and catalytic performances of x%K/Beta zeolite catalysts, the specific surface area and micropore volume of the samples should not be responsible for the difference in their acylation performances, since the textural properties of x%K/Beta samples changed slightly with K + loadings, as mentioned in Section 3.1.1.…”

“…4. Zhao et al [1] reported that an optimal acid catalyst for the acylation of AN should possess the concentration of strong acid sites as high as possible. In our present case, AN conversion increased with the concentration of strong acid sites in the form of a quadratic function as presented in Fig.…”

“…Friedel-Crafts acylation of aromatics is one of the most important synthetic reactions in manufacturing aromatic ketones, which are the key intermediates in fine chemicals, agrochemicals, pharmaceuticals, and fragrance industrial processes [1][2][3]. The conventional method of preparing aromatic ketones is acylation of aromatics with an acylation reagent, such as acid halides and anhydrides, and in the presence of Lewis acids (e.g., AlCl 3 ) or strong protonic acids (e.g., HF) [4,5].…”

“…However, these traditional catalysts have some limitations, such as environmental pollution arising from the disposal of spent catalysts and toxic wastes, reactor corrosion, and product isolation [2,3,6,7]. Moreover, more stoichiometric quantity of catalyst is required, as the metal halide itself has a tendency of complexation with the ketone product [1,3,5]. In order to overcome these drawbacks, considerable efforts have been made to explore heterogeneous solid acid catalysts, including solid superacid, heteropolyacid, and zeolite [8][9][10].…”

“…On the other hand, only weak and moderate acid sites were found to play an important role in the acylation of AN with acetic anhydride (AA) over Cr-doped Beta zeolite [3]. In addition, many researchers suggested that Brönsted acid sites were responsible for Friedel-Crafts acylation [1,[15][16][17][18]. Whereas Sartori et al [19] reported that the acylation of dimethoxyarenes with acyl chlorides over HY zeolite required a delicate balance between Lewis and Brönsted acid sites.…”