Incorporation of Ti into the framework of aluminium-free zeolite Beta has been achieved in F- medium and has produced hydrophobic selective oxidation catalysts. The Ti−Beta(F) materials have been characterized by X ray diffraction, infrared, Raman, ultraviolet, XANES, EXAFS, 29Si MAS NMR, and 1H→29Si CP MAS NMR spectroscopies, adsorption microcalorimetry, and catalytic testing. At near neutral pH the incorporation of Ti into the framework appears to present an upper limit of ca. 2.3 Ti/uc, beyond which anatase is detected in the calcined materials. However, at higher pH (ca. 11) larger amounts of Ti can be incorporated without anatase formation. After calcination, Ti incorporation in the framework is characterized by an increase in the unit cell volume, the appearance of one Raman band and three infrared bands in the region near 960 cm-1 and the presence of a strong absorption band in the 205−220 nm ultraviolet spectrum. By 29Si MAS NMR, 1H→29Si CP MAS NMR, and infrared spectroscopies it is concluded that upon contact with ambient humidity there is no hydrolysis of Si−O−Ti bonds in Ti−Beta zeolites prepared by the fluoride route, while it is probably a major feature of those synthesized in OH- medium. XANES and EXAFS spectroscopies of calcined dehydrated Ti−Beta zeolites unambiguously demonstrate the tetrahedral coordination of Ti with a Ti−O bond length of ca. 1.80 Å. Upon hydration, the changes in the XANES and EXAFS spectra are consistent with a change in the coordination of Ti to reach a state which depends on the composition and synthesis route and which ranges from a 5-fold coordination for Al-free Ti−Beta synthesized by the F- method to a highly distorted 6-fold coordination in Ti,Al−Beta synthesized in OH- medium. Adsorption microcalorimetry experiments show the strict hydrophobic nature of pure SiO2 zeolite Beta synthesized in F- medium while evidencing a slight increase in the hydrophilicity of the material upon incorporation of Ti to the framework. This is due to the relatively strong adsorption of precisely one H2O molecule per Ti site. On the contrary, the materials synthesized in OH- medium show an enhanced hydrophilicity. Finally, Ti−Beta(F) is an active and selective catalyst for oxidation of organic substrates with H2O2. A comparison of the activities and selectivities of Ti−Beta(F), Ti−Beta(OH) and TS-1 in the epoxidation of 1-hexene using acetonitrile and methanol as solvents demonstrates that the major differences between Ti−Beta and TS-1 catalysts are intrinsic to each zeolitic structure. Because of its high hydrophobicity, Ti−Beta(F) catalyst can advantageously replace Ti−Beta(OH) in the epoxidation of substrates, like unsaturated fatty acids or esters, which contain a polar moiety.

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Non-oxidative methane dehydroaromatization (MDA:6CH 4 ↔ C 6 H 6 + 9H 2 ) using shapeselective Mo/zeolite catalysts is a technology to exploit stranded natural gas reserves by direct conversion into transportable liquids. The reaction, however, faces two major issues: the onepass conversion/yield is limited by thermodynamics, and the catalyst deactivates fast due to the kinetically-favored formation of coke. Here we show that integration of an electrochemical BaZrO 3 -based membrane exhibiting both proton and oxide ion conductivity into an MDA reactor enables high aromatic yields and outstanding catalyst stability. These effects originate from the simultaneous extraction of hydrogen and distributed injection of oxide ions along the reactor length. Further, we demonstrate that the electrochemical co-ionic membrane reactor enables high carbon efficiencies (up to 80%) significantly improving the techno-economic process viability, and sets the ground for its commercial deployment. One Sentence Summary:The integration of a co-ionic membrane in a MDA reactor remarkably enhances aromatics yield and catalyst lifetime. Main text:

This review discusses approaches for tailoring active sites in extra-large pore, nanocrystalline, and hierarchical zeolites and their performance in emerging catalytic applications.

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The development of sustainable active and stable heterogeneous catalysts for the oligomerization of ethylene to replace the unfriendly homogenous systems based on transition metal complexes currently applied in the industry still remains a challenge. In this work we show that bifunctional catalysts comprised of Ni loaded on nanocrystalline zeolite H-Beta can efficiently catalyze the oligomerization of ethylene with high stability and selectivity to liquid oligomers under mild reaction conditions. Ni-Beta catalysts were prepared starting from a commercial nanocrystalline H-Beta sample with Si/Al ratio of 12 via both ionic exchange (1.0-2.5 wt% Ni) and incipient wetness impregnation (1.1-10.0 wt% Ni) using aqueous Ni(NO 3 ) 2 solutions, followed by air-calcination at 550ºC. The Ni-Beta catalysts exhibited no signs of deactivation under the studied conditions (T= 120ºC, P tot = 3.5 MPa, P C2H4 = 2.6 MPa, WHSV= 2.1 h Additionally, most active Ni-Beta catalysts displayed a non-Schulz-Flory product distribution with high selectivity to liquid oligomers ( 60 wt%) and high degree of branching due to the contribution of the hetero-oligomerization pathway involving zeolite Brønsted acid sites.

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