Abstract
The effect of Zn on side-chain alkylation of toluene with methanol over KX zeolite was investigated. It was found that the addition of Zn with a low content over KX could enhance toluene conversion significantly. In addition, the results showed that the conversion of toluene over ZnKX (0.8 wt. %) catalyst was almost twice as high as that over KX. The catalysts were characterized by X-ray diffraction (XRD), N2 physisorption, NH3-temperature-programmed desorption (TPD), pyridine absorption infrared (IR) spectroscopy, CO2-TPD, X-ray photoelectron spectroscopy (XPS) and IR adsorption of reactants. The TPD and XPS results showed that the existence of Zn species could increase the strength of basic sites. The IR adsorption of reactants results suggested that the introduction of Zn could decrease the chemisorbed toluene and increase the relative amounts of unidentate formate. The results indicated that an excellent balance between the acid-base properties of the catalyst and the sorption stoichiometry of methanol-toluene could be achieved, leading to the improvement of catalytic activity.
Highlights
Ethylbenzene and styrene are essential materials for the petrochemical industry
Das and Pramanik found that the addition of Fe-Mo oxide into CsX could facilitate the formation of formaldehyde and improve the activity of side-chain alkylation reaction.[17]
All catalysts are tested for the side-chain alkylation of toluene with methanol to investigate the effect of Zn on the catalytic performances of K-exchanged X zeolite (KX) zeolite
Summary
Ethylbenzene and styrene are essential materials for the petrochemical industry. Currently, they are mainly produced by the catalytic alkylation of benzene with ethylene and followed by the catalytic dehydrogenation of ethylbenzene. Das and Pramanik found that the addition of Fe-Mo oxide into CsX could facilitate the formation of formaldehyde (the true alkylation reagent) and improve the activity of side-chain alkylation reaction.[17] Lacroix et al reported that Cu contributed to the dehydrogenation of reaction intermediates.[18] Compared with copper, zinc possesses a similar electronic structure and is widely used in the reaction of methanol dehydrogenation to formaldehyde. In the situation where the acidic and basic centers are catalytically active sites for the side-chain alkylation, it should be possible to optimize the reaction by introducing reductive Zn species rich in electron into X zeolites. The side-chain alkylation of toluene with methanol was studied over K-exchanged X zeolite (KX) and Zn-modified KX (ZnKX) to study the effect of Zn on catalytic activity. The catalysts were characterized by N2-physisorption, X-ray photoelectron spectroscopy (XPS), NH3-temperature-programmed desorption (TPD), CO2-TPD, and infrared (IR) spectroscopy adsorption to provide insight into the effect of Zn additives
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