Tantalum-containing SiBEA zeolite with isolated framework mononuclear Ta(V) doped with Ag, Cu and Zn were prepared and characterized by XRD, XPS, DR UV-VIS and FTIR (with 2 of additional dehydrogenation sites. Such modification allows accelerating ethanol dehydrogenation to acetaldehyde and subsequent steps of the ethanol-to-butadiene process.Ethanol conversion and butadiene selectivity over the catalysts increase in the order: TaSiBEA < ZnTaSiBEA < AgTaSiBEA < CuTaSiBEA. Higher selectivity to butadiene (73 %) was achieved over CuTaSiBEA (at 88% ethanol conversion, T = 598 К, WHSV = 0.5 h -1 ). 22ASSOCIATED CONTENT Supporting Information. The details of the calculations of the amount of recycled CO 2 in 1,3-butadiene production from biomass, XP spectra, TEM images and diffraction patterns, additional catalytic results. This material is available free of charge via the Internet at http://pubs.acs.org. AUTHOR INFORMATION Corresponding Authors* E-mails: pavlo_kyriienko@ukr.net (P.K.) and stanislaw.dzwigaj@upmc.fr (S.D.).

Effect of ZnO on ethanol conversion to 1,3-butadiene (BD) on ZnO/MgO-SiO 2 catalysts consists in the enhancement of selectivity and yield of BD due to higher rate of ethanol dehydrogenation to acetaldehyde. It has been shown that two types of Lewis acid sites formed in the contact zones of MgO-SiO 2 and ZnO-SiO 2 in the catalysts play an important role in BD synthesis from ethanol. The highest BD yield is achieved at ratio of MgO:SiO 2 = 1:1. Graphical Abstract

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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