scholarly journals Near 100% ethene selectivity achieved by tailoring dual active sites to isolate dehydrogenation and oxidation

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Chaojie Wang ◽  
Bing Yang ◽  
Qingqing Gu ◽  
Yujia Han ◽  
Ming Tian ◽  
...  
Keyword(s):  
Oxidative Dehydrogenation ◽  
Selective Oxidation ◽  
Active Sites ◽  
Three Dimensional ◽  
Acid Sites ◽  
Deep Oxidation ◽  
Oxidation Catalysis ◽  
Catalytic Dehydrogenation ◽  
Light Alkane ◽  
Oxidation Of Hydrogen

AbstractProhibiting deep oxidation remains a challenging task in oxidative dehydrogenation of light alkane since the targeted alkene is more reactive than parent substrate. Here we tailor dual active sites to isolate dehydrogenation and oxidation instead of homogeneously active sites responsible for these two steps leading to consecutive oxidation of alkene. The introduction of HY zeolite with acid sites, three-dimensional pore structure and supercages gives rise to Ni2+ Lewis acid sites (LAS) and NiO nanoclusters confined in framework wherein catalytic dehydrogenation of ethane occurs on Ni2+ LAS resulting in the formation of ethene and hydrogen while NiO nanoclusters with decreased oxygen reactivity are responsible for selective oxidation of hydrogen rather than over-oxidizing ethene. Such tailored strategy achieves near 100% ethene selectivity and constitutes a promising basis for highly selective oxidation catalysis beyond oxidative dehydrogenation of light alkane.

Designer Nanostructures Of Catalysts in the Environmental-HREM

1999 ◽  
Vol 5 (S2) ◽  
pp. 686-687
Author(s):  
Pratibha L. Gai
Keyword(s):  
Real Time ◽  
Selective Oxidation ◽  
Active Sites ◽  
High Resolution Electron Microscopy ◽  
Oxidation Catalysis ◽  
Atomic Scale ◽  
Structure Property ◽  
Structure Property Relationships ◽  
Resolution Electron ◽  
Recent Developments

Major advances in the field of in situ environmental high resolution electron microscopy (EHREM) probe selective oxidation catalysis directly on the atomic scale. Dynamic gas-solid surface interactions are studied in real-time and under realistic reaction conditions to unravel atomic level insights into active sites and structure-property relationships in vital chemical and technological processes [1-3]. The recent developments include a pioneering approach with the controlled environmental cell (ECELL) facilities permanently mounted inside the EHREM [2]. Accessories have been added for simultaneous structural and compositional analyses of the reactor contents in real-time, and using atomic resolution imaging with transmission electron diffraction and parallel electron energy loss spectroscopy (PEELS). We are now developing innovative experimental methods that include very high temperature studies and combining in the same instrument facilities for both EHREM and environmental-SEM (ESEM), (EHREM-ESEM), with attractive possibilities for studying the science of selective oxidation catalysis.Alkane Catalysis, Chlorofluorocarbons and Nanotubes:In the domain of transition metal based oxides, discoveries of fundamental mechanisms underlying selective catalyzation have come from EHREM studies.

scholarly journals Heterogeneous Bimetallic Cu–Ni Nanoparticle-Supported Catalysts in the Selective Oxidation of Benzyl Alcohol to Benzaldehyde

Catalysts ◽  
2019 ◽  
Vol 9 (6) ◽  
pp. 538 ◽  
Author(s):  
Lili Liu ◽  
Xiaojing Zhou ◽  
Li Liu ◽  
Shuai Jiang ◽  
Yingjie Li ◽  
...  
Keyword(s):  
Benzyl Alcohol ◽  
Selective Oxidation ◽  
Active Sites ◽  
Supported Catalysts ◽  
Metal Organic Framework ◽  
Acid Sites ◽  
High Yield ◽  
Ni Nanoparticles ◽  
Oxidation Of Benzyl Alcohol ◽  
Ni Supported Catalysts

Three bimetallic Cu–Ni nanoparticle-supported catalysts were synthesized by co-immobilization followed by H2 reduction. A chromium(III) terephthalate metal organic framework (MIL-101), titanium dioxide (TiO2), and carbon (C) with different properties (acidity and Brunauer–Emmett–Teller surface area) were selected as supports for studying the effect of the support nature on the catalytic activity and selectivity in the oxidation of benzyl alcohol. The physicochemical properties of the Cu–Ni-supported catalysts were characterized by XRD, NH3-TPD, nitrogen adsorption/desorption, TEM, EDS, XPS, and ICP-OES. Bimetallic Cu–Ni nanoparticles were highly dispersed on the support. The catalytic activities of CuNi/MIL-101, CuNi/TiO2, and CuNi/C were tested in the selective oxidation of benzyl alcohol to benzaldehyde in the presence of molecular oxygen under mild reaction conditions. The highest benzaldehyde yields were achieved with CuNi/TiO2, CuNi/MIL-101, and CuNi/C catalysts at 100 °C within 4 h under 5, 3, and 3 bar of O2, respectively. The bimetallic Cu–Ni-supported catalysts possessed two types of catalytic active sites: acid sites and bimetallic Cu–Ni nanoparticles. The CuNi/MIL-101 catalyst possessed a high number of acid sites and exhibited high yield during selective benzyl alcohol oxidation to benzaldehyde. Importantly, the catalysts exhibited a high functional group (electron-donating and electron-withdrawing groups) tolerance. Cu–Ni-supported catalysts with an Cu:Ni mole ratio of 1:1 exhibited the highest yield of 47% for the selective oxidation of benzyl alcohol to benzaldehyde. Reusability and leaching experiment results exhibited that CuNi/MIL-101 showed better stability than CuNi/TiO2 and CuNi/C catalysts due to the large porous cavities of MIL-101 support; these cavities can be used to trap bimetallic Cu–Ni nanoparticles and inhibit nanoparticle leaching.

scholarly journals Metal-Organic Frameworks in Oxidation Catalysis with Hydrogen Peroxide

Catalysts ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 283
Author(s):  
Oxana Kholdeeva ◽  
Nataliya Maksimchuk
Keyword(s):  
Hydrogen Peroxide ◽  
Liquid Phase ◽  
Selective Oxidation ◽  
Metal Organic Frameworks ◽  
Short Review ◽  
Catalytic Performance ◽  
Oxidation Catalysis ◽  
Catalyst Stability ◽  
Aqueous Hydrogen Peroxide ◽  
Metal Organic

In recent years, metal–organic frameworks (MOFs) have received increasing attention as selective oxidation catalysts and supports for their construction. In this short review paper, we survey recent findings concerning use of MOFs in heterogeneous liquid-phase selective oxidation catalysis with the green oxidant–aqueous hydrogen peroxide. MOFs having outstanding thermal and chemical stability, such as Cr(III)-based MIL-101, Ti(IV)-based MIL-125, Zr(IV)-based UiO-66(67), Zn(II)-based ZIF-8, and some others, will be in the main focus of this work. The effects of the metal nature and MOF structure on catalytic activity and oxidation selectivity are analyzed and the mechanisms of hydrogen peroxide activation are discussed. In some cases, we also make an attempt to analyze relationships between liquid-phase adsorption properties of MOFs and peculiarities of their catalytic performance. Attempts of using MOFs as supports for construction of single-site catalysts through their modification with heterometals will be also addressed in relation to the use of such catalysts for activation of H2O2. Special attention is given to the critical issues of catalyst stability and reusability. The scope and limitations of MOF catalysts in H2O2-based selective oxidation are discussed.

scholarly journals On the Role of Protonic Acid Sites in Cu Loaded FAU31 Zeolite as a Catalyst for the Catalytic Transformation of Furfural to Furan

Molecules ◽  
2021 ◽  
Vol 26 (7) ◽  
pp. 2015
Author(s):  
Łukasz Kuterasiński ◽  
Małgorzata Smoliło-Utrata ◽  
Joanna Kaim ◽  
Wojciech Rojek ◽  
Jerzy Podobiński ◽  
...  
Keyword(s):  
Active Sites ◽  
Acid Sites ◽  
Bronsted Acid ◽  
Brønsted Acid ◽  
Brønsted Acid Sites ◽  
Protonic Acid ◽  
Brönsted Acid ◽  
Brönsted Acid Sites ◽  
Bronsted Acid Sites

The aim of the present paper is to study the speciation and the role of different active site types (copper species and Brønsted acid sites) in the direct synthesis of furan from furfural catalyzed by copper-exchanged FAU31 zeolite. Four series of samples were prepared by using different conditions of post-synthesis treatment, which exhibit none, one or two types of active sites. The catalysts were characterized by XRD, low-temperature sorption of nitrogen, SEM, H2-TPR, NMR and by means of IR spectroscopy with ammonia and CO sorption as probe molecules to assess the types of active sites. All catalyst underwent catalytic tests. The performed experiments allowed to propose the relation between the kind of active centers (Cu or Brønsted acid sites) and the type of detected products (2-metylfuran and furan) obtained in the studied reaction. It was found that the production of 2-methylfuran (in trace amounts) is determined by the presence of the redox-type centers, while the protonic acid sites are mainly responsible for the furan production and catalytic activity in the whole temperature range. All studied catalysts revealed very high susceptibility to coking due to polymerization of furfural.

scholarly journals Control of zeolite microenvironment for propene synthesis from methanol

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Longfei Lin ◽  
Mengtian Fan ◽  
Alena M. Sheveleva ◽  
Xue Han ◽  
Zhimou Tang ◽  
...  
Keyword(s):  
Active Sites ◽  
Inelastic Neutron Scattering ◽  
Sustainable Manufacturing ◽  
Methanol Conversion ◽  
Acid Sites ◽  
Light Olefins ◽  
Carbon Bond ◽  
X Ray ◽  
Carbon Carbon Bond ◽  
Catalytic Stability

AbstractOptimising the balance between propene selectivity, propene/ethene ratio and catalytic stability and unravelling the explicit mechanism on formation of the first carbon–carbon bond are challenging goals of great importance in state-of-the-art methanol-to-olefin (MTO) research. We report a strategy to finely control the nature of active sites within the pores of commercial MFI-zeolites by incorporating tantalum(V) and aluminium(III) centres into the framework. The resultant TaAlS-1 zeolite exhibits simultaneously remarkable propene selectivity (51%), propene/ethene ratio (8.3) and catalytic stability (>50 h) at full methanol conversion. In situ synchrotron X-ray powder diffraction, X-ray absorption spectroscopy and inelastic neutron scattering coupled with DFT calculations reveal that the first carbon–carbon bond is formed between an activated methanol molecule and a trimethyloxonium intermediate. The unprecedented cooperativity between tantalum(V) and Brønsted acid sites creates an optimal microenvironment for efficient conversion of methanol and thus greatly promotes the application of zeolites in the sustainable manufacturing of light olefins.

scholarly journals Enhanced catalytic ozonation of ibuprofen using a 3D structured catalyst with MnO2 nanosheets on carbon microfibers

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Guhankumar Ponnusamy ◽  
Hajar Farzaneh ◽  
Yongfeng Tong ◽  
Jenny Lawler ◽  
Zhaoyang Liu ◽  
...  
Keyword(s):  
Removal Efficiency ◽  
Active Sites ◽  
Low Cost ◽  
Three Dimensional ◽  
Industrial Applications ◽  
Catalytic Ozonation ◽  
Heterogeneous Catalytic ◽  
Structured Catalyst ◽  
Dimensional Network ◽  
Carbon Microfibers

AbstractHeterogeneous catalytic ozonation is an effective approach to degrade refractory organic pollutants in water. However, ozonation catalysts with combined merits of high activity, good reusability and low cost for practical industrial applications are still rare. This study aims to develop an efficient, stable and economic ozonation catalyst for the degradation of Ibuprofen, a pharmaceutical compound frequently detected as a refractory pollutant in treated wastewaters. The novel three-dimensional network-structured catalyst, comprising of δ-MnO2 nanosheets grown on woven carbon microfibers (MnO2 nanosheets/carbon microfiber), was synthesized via a facile hydrothermal approach. Catalytic ozonation performance of Ibuprofen removal in water using the new catalyst proves a significant enhancement, where Ibuprofen removal efficiency of close to 90% was achieved with a catalyst loading of 1% (w/v). In contrast, conventional ozonation was only able to achieve 65% removal efficiency under the same operating condition. The enhanced performance with the new catalyst could be attributed to its significantly increased available surface active sites and improved mass transfer of reaction media, as a result of the special surface and structure properties of this new three-dimensional network-structured catalyst. Moreover, the new catalyst displays excellent stability and reusability for ibuprofen degradation over successive reaction cycles. The facile synthesis method and low-cost materials render the new catalyst high potential for industrial scaling up. With the combined advantages of high efficiency, high stability, and low cost, this study sheds new light for industrial applications of ozonation catalysts.

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