An AgSiBEA zeolite has been prepared by a two-step postsynthesis procedure that consists of first creating the vacant T atom sites with associated silanol groups by treatment of TEABEA zeolite with nitric acid and then impregnating of resulting SiBEA zeolite with an aqueous solution of AgNO3. The incorporation of Ag ions into the vacant T atom sites of the framework of SiBEA zeolite as mononuclear Ag(I) has been evidenced by combined use of XRD, NMR, FTIR, diffuse reflectance UV–vis, XPS, and TPR. The consumption of OH groups has been monitored by FTIR. The Brønsted and Lewis acidities of AlBEA, SiBEA, and AgSiBEA have been identified by FTIR spectroscopy of adsorbed pyridine and CO as probe molecules.

International audienceNbSiBEA zeolites contained isolated framework mononuclear Nb(V) (Nb0.7SiBEA) and a mixture of framework mononuclear and extra-framework polynuclear Nb(V) (Nb2.0SiBEA) were prepared by two-step postsynthesis method as evidenced by XRD, NMR, DR UV–vis and FTIR. DR UV–vis showed that two types of framework mononuclear Nb(V) are present in Nb0.7SiBEA, while Nb2.0SiBEA mainly contained isolated mononuclear Nb(V) in the framework of zeolite and polynuclear Nb(V) in the extra-framework position. FTIR with pyridine and 2,6-di-tert-butylpyridine as probe molecules showed that major amount Lewis and weak Brønsted acidic sites are formed by incorporation of niobium in the framework of zeolites as mononuclear Nb(V). The catalytic properties of Nb-containing zeolites were investigated in tandem processes of ethanol conversion into 1,3-butadiene (gas-phase) and synthesis of unsymmetrical ethers from aromatic aldehyde and aliphatic alcohol (liquid-phase). It has been found that Nb0.7SiBEA catalyst, containing only isolated framework mononuclear Nb(V) is more active than Nb2.0SiBEA in the conversion of ethanol and ethanol/acetaldehyde mixture into 1,3-butadiene, MPV reduction of crotonaldehyde with ethanol and etherification of 4-methoxybenzyl alcohol with 2-butanol. The higher specific activity (turnover number/frequency) of Nb0.7SiBEA than Nb2.0SiBEA catalyst has been revealed for gas- and liquid-phase tandem processes

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