Tuning of acidic and catalytic properties of IWR zeolite by post-synthesis incorporation of three-valent elements

• Acidity of germanosilicate IWR zeolite can be modified post-synthetically.
• Accurate selection of treatment condition is required to preserve IWR framework.
• pH, temperature and nature of 3-valent element govern isomorphous incorporation.

Post-synthesis alumination and galliation of borogermanosilicate IWR zeolite in acidic medium (pH 0.5–2.0) was shown to be an efficient approach for tuning its acidic and catalytic properties. The concentration of Al(NO3)3, pH, and the temperature of the treatment of IWR zeolite were varied and related to the structural and acidic properties of the obtained materials. The concentration of Al incorporated in the framework of IWR increased with increasing concentration of applied Al(NO3)3 solution (in the range 0.1–1.0 M), pH (0.5–2.0), or the temperature (25–95 °C) of the treatment. Obtained Ga- and Al-containing IWR zeolites are characterized by a higher concentration of strong Brønsted acid sites (117 and 82–277 μmol/g vs. 24 μmol/g) and superior catalytic performance in benzoylation of p-xylene in comparison with parent B-IWR zeolite. The balanced strength of acid centers in Ga-IWR enabling sufficient activation of benzoyl chloride as well as efficient desorption of formed ketone results in the highest yield of target product over Ga-IWR among isomorphously substituted IWR zeolites: B-IWR (5%) < Al-IWR (33%) < Ga-IWR (99%).

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