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Author(s): Dan Zhao [sup.1] [sup.2] , Xinxin Tian [sup.2] [sup.3] , Dmitry E. Doronkin [sup.4] , Shanlei Han [sup.1] [sup.2] , Vita A. Kondratenko [sup.2] , Jan-Dierk Grunwaldt [sup.4] , [...], Propane dehydrogenation (PDH) to propene is an important alternative to oil-based cracking processes, to produce this industrially important platform chemical.sup.1,2. The commercial PDH technologies utilizing Cr-containing (refs. .sup.3,4) or Pt-containing (refs. .sup.5-8) catalysts suffer from the toxicity of Cr(vi) compounds or the need to use ecologically harmful chlorine for catalyst regeneration.sup.9. Here, we introduce a method for preparation of environmentally compatible supported catalysts based on commercial ZnO. This metal oxide and a support (zeolite or common metal oxide) are used as a physical mixture or in the form of two layers with ZnO as the upstream layer. Supported ZnO.sub.x species are in situ formed through a reaction of support OH groups with Zn atoms generated from ZnO upon reductive treatment above 550 °C. Using different complementary characterization methods, we identify the decisive role of defective OH groups for the formation of active ZnO.sub.x species. For benchmarking purposes, the developed ZnO-silicalite-1 and an analogue of commercial K-CrO.sub.x/Al.sub.2O.sub.3 were tested in the same setup under industrially relevant conditions at close propane conversion over about 400 h on propane stream. The developed catalyst reveals about three times higher propene productivity at similar propene selectivity. Propene is obtained through propane dehydrogenation using catalysts that are toxic, expensive or demanding to regenerate with ecologically harmful compounds, but the ZnO-based alternative reported here is cheap, clean and scalable.

The application of Ga-MCM-41-SO3H as a new efficient heterogeneous catalyst for the synthesis of celecoxib and pyrazole derivatives under room temperature is reported. The mesoporous material Ga-MCM-41 was first prepared and then functionalized with the sulfonic acid group by the post-synthetic modification to obtain the final solid acid catalyst. The successful grafting of the -SO3H group onto the Ga-MCM-41 mesoporous walls was asserted by X-ray diffraction, scanning electron microscopy equipped with energy dispersive spectroscopy (SEM/EDS), and acid–base titration. The catalytic application of Ga-MCM-41-SO3H in the synthesis of celecoxib and pyrazole derivatives has resulted in a high yield (up to 95%) under mild conditions. Notably, the Ga-MCM-41-SO3H catalyst was stable and was able to reuse at least five times without losing significant catalytic activity. [ABSTRACT FROM AUTHOR]

Propane dehydrogenation (PDH) to propene is an important alternative to oil-based cracking processes, to produce this industrially important platform chemical1,2. The commercial PDH technologies utilizing Cr-containing (refs. 3,4) or Pt-containing (refs. 5–8) catalysts suffer from the toxicity of Cr(vi) compounds or the need to use ecologically harmful chlorine for catalyst regeneration9. Here, we introduce a method for preparation of environmentally compatible supported catalysts based on commercial ZnO. This metal oxide and a support (zeolite or common metal oxide) are used as a physical mixture or in the form of two layers with ZnO as the upstream layer. Supported ZnOx species are in situ formed through a reaction of support OH groups with Zn atoms generated from ZnO upon reductive treatment above 550 °C. Using different complementary characterization methods, we identify the decisive role of defective OH groups for the formation of active ZnOx species. For benchmarking purposes, the developed ZnO–silicalite-1 and an analogue of commercial K–CrOx/Al2O3 were tested in the same setup under industrially relevant conditions at close propane conversion over about 400 h on propane stream. The developed catalyst reveals about three times higher propene productivity at similar propene selectivity.Propene is obtained through propane dehydrogenation using catalysts that are toxic, expensive or demanding to regenerate with ecologically harmful compounds, but the ZnO-based alternative reported here is cheap, clean and scalable. [ABSTRACT FROM AUTHOR]

Zinc oxide/porous silica (ZnO/SiO2) composite was used as a catalyst to transform glycerol to glycerol carbonate (GC), a chemical intermediate and monomer for the synthesis of new functionalized polymers. The ZnO/SiO2 catalyst was prepared using the direct precipitation method by mixing zinc sulfate solution with Aerosil 300 silica suspension and adding potassium oxalate solution. Catalytic transformation used glycerol and urea (molar ratio = 1:1) at 140 °C, 40 mbar, and various reaction times (1-6 h). The ZnO catalyst exhibited a high percentage of glycerol conversion of 82.38%; however, the yield of GC and selectivity toward GC were relatively low (i.e., 33.33% and 40.46%, respectively). The presence of silica support (ZnO/(x)SiO2 increased the selectivity toward GC and yield of GC to 74.40% to 77.83% and 57.86% to 64.30%, respectively. Furthermore, although its crystallinity decreased, the reused ZnO/(60)SiO2 catalyst still exhibited a high activity. The scanning transmission electron microscopy image indicated the migration of ZnO on the surface of the composite and the possibility of ZnO-glycolate formation, which were also confirmed by FTIR measurement. Nevertheless, these results showed that ZnO/SiO2 is a promising catalyst for the transformation of glycerol to GC. [ABSTRACT FROM AUTHOR]

Ordered mesoporous SBA-15 analogs with different Si/Al ratios were successfully prepared in a two-step process from self-assembly of ZSM-5 nanoseeds at high temperature in mildly acidic media (473 K, pH 3.5). The obtained products were characterized as SAXS, XRD, N2 sorption, FTIR, TEM, NH3-TPD, AAS and ICP. The results show that the initial Si/Al molar ratio of ZSM-5 precursors strongly affects the final materials' properties. A highly condensed, well-ordered mesoporous SBA-15 analog with improved hydrothermal stability and acidic properties can be prepared from low aluminum containing ZSM-5 precursors (Si/Al ≥ 20). Reducing the initial Si/Al molar ratio to 10, however, leads to the formation of a disordered mesoporous SBA-15 type material accompanied by degraded textural and acidic properties. The gas phase cracking of cumene, carried out as probe reaction to evaluate Bransted acidity, reveals that an increased density of Bransted acid sites has been achieved over the SBA-15 analogs compared to conventional Al-SBA-15 due to the preservation of zeolite building units in the mesopore walls of the SBA-15 analogs. [ABSTRACT FROM AUTHOR]

The NO storage properties of MnOx/support materials (5–50 wt% MnOx loading) was experimentally investigated in the presence of O2 and H2O between 50 and 700 °C applying a non-isothermal temperature-programmed method. In dependence on MnOx loading and NO supply, the materials show an intermediate decrease of NO storage capacity between 200 and 300 °C. This effect is caused by decomposition of surface nitrites with release of NO into the gas phase as proved by in situ DRIFT measurement. The interpretation is corroborated by modelling of the underlying adsorption/desorption reaction steps, considering the different thermal stability of nitrite/nitrate surface species. [ABSTRACT FROM AUTHOR]