Conversion of methane to ethylene

1997 ◽  
Vol 75 (4) ◽  
pp. 465-468
Author(s):  
B.K. Miremadi ◽  
K. Colbow ◽  
S. Roy Morrison
Keyword(s):  
Ethylene Production ◽  
Active Sites ◽  
High Selectivity ◽  
Oxidation Catalyst ◽  
Ethylene Oxidation ◽  
Lithium Aluminate ◽  
Co Catalyst ◽  
Conversion Of Methane ◽  
Ethylene Selectivity ◽  
Intermediate Value

A lithium aluminate – MgO catalyst has been found to convert methane to ethylene with a high selectivity. The rate of conversion increased when a MoO3 co-catalyst was used to remove the poisoning products. It is shown that for optimum conversion and selectivity to ethylene, the oxygen pressure should be at an intermediate value, high enough to provide active sites but low enough to avoid ethylene oxidation. Thus the oxygen should be "bled-in" along the catalyst bed. In demonstration of these concepts we have shown a 28.6% CH4 conversion with 63.2% ethylene selectivity and 9.8% ethane, producing a C2 yield of about 21.4%. Keywords: methane oxidation, methane conversion, ethylene production, oxidation catalyst, aluminate catalyst.

The Selective Oxidation of Hydrocarbons on Isolated Iron Active Sites under Ambient Conditions

2019 ◽  
Vol 41 (6) ◽  
pp. 946-946
Author(s):  
Zhengliang Qi Zhengliang Qi ◽  
Junmei Liu Junmei Liu ◽  
Wanwan Guo and Jun Huang Wanwan Guo and Jun Huang
Keyword(s):  
Ionic Liquid ◽  
Activated Carbon ◽  
Carbon Material ◽  
Active Sites ◽  
High Selectivity ◽  
Good Activity ◽  
Ambient Conditions ◽  
Oxidation Of Hydrocarbons ◽  
Fe Catalysts ◽  
Iron Active Sites

The N-doped carbon material supported Fe catalysts were developed for the oxidation of C-H bond of hydrocarbons to ketones and alcohols. The supported Fe catalysts were prepared by pyrolysis of [CMIM]3Fe(CN)6 ionic liquid in activated carbon. And the Fe(Ⅲ)@CN-600 showed good activity and high selectivity for the oxidation of alfa C-H bond of alkylbenzenes. The isolated Fe(Ⅲ) iron active sites should be responsible for the high activity and selectivity for the oxidation of hydrocarbons to ketones. Several ketones were obtained in good to excellent yields. Moreover, cyclohexanone can also be obtained through the oxidation of cyclohexane.

Photocatalytic reforming of glycerol for H2 evolution on Pt/TiO2: fundamental understanding the effect of co-catalyst Pt and the Pt deposition route

2015 ◽  
Vol 3 (5) ◽  
pp. 2271-2282 ◽  
Author(s):  
Xiaoliang Jiang ◽  
Xianliang Fu ◽  
Li Zhang ◽  
Sugang Meng ◽  
Shifu Chen
Keyword(s):  
Active Sites ◽  
H2 Evolution ◽  
Co Catalyst ◽  
Fundamental Understanding

The effects of deposited Pt and its deposition route on the photocatalytic reforming of glycerol for H2 evolution over Pt/TiO2 were investigated. Intimately loaded Pt(0) particles are the key active sites for the reaction, the formation of which was favored by an in situ photo-deposition route.

scholarly journals Highly Selective Au/ZnO via Colloidal Deposition for CO2 Hydrogenation to Methanol: Evidence of AuZn Role

2021 ◽  
Vol 16 (1) ◽  
pp. 44-51
Author(s):  
Hasliza Bahruji ◽  
Mshaal Almalki ◽  
Norli Abdullah
Keyword(s):  
Active Sites ◽  
Au Nanoparticles ◽  
High Selectivity ◽  
Average Diameter ◽  
Co2 Hydrogenation ◽  
Impregnation Method ◽  
Co2 Conversion ◽  
Methanol Production ◽  
Surface Oxygen Vacancy ◽  
Colloidal Method

Gold, Au nanoparticles were deposited on ZnO, Al2O3, and Ga2O3 via colloidal method in order to investigate the role of support for CO2 hydrogenation to methanol. Au/ZnO was also produced using impregnation method to investigate the effect of colloidal method to improve methanol selectivity. Au/ZnO produced via sol immobilization showed high selectivity towards methanol meanwhile impregnation method produced Au/ZnO catalyst with high selectivity towards CO. The CO2 conversion was also influenced by the amount of Au weight loading. Au nanoparticles with average diameter of 3.5 nm exhibited 4% of CO2 conversion with 72% of methanol selectivity at 250 °C and 20 bar. The formation of AuZn alloy was identified as active sites for selective CO2 hydrogenation to methanol. Segregation of Zn from ZnO to form AuZn alloy increased the number of surface oxygen vacancy for CO2 adsorption to form formate intermediates. The formate was stabilized on AuZn alloy for further hydrogenation to form methanol.  The use of Al2O3 and Ga2O3 inhibited the formation of Au alloy, and therefore reduced methanol production. Au/Al2O3 showed 77% selectivity to methane, meanwhile Au/Ga2O3 produced 100% selectivity towards CO. Copyright © 2021 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0). 

scholarly journals CH4-to-CH3OH on Mononuclear Cu(II) Sites Supported on Al2O3: Structure of Active Sites from Electron Paramagnetic Resonance

2021 ◽  
Author(s):  
Jordan Meyet ◽  
Anton Ashuiev ◽  
Gina Noh ◽  
Mark Newton ◽  
Daniel Klose ◽  
...  
Keyword(s):  
Electron Paramagnetic Resonance ◽  
Organometallic Chemistry ◽  
Active Sites ◽  
Spectroscopic Characterization ◽  
Paramagnetic Resonance ◽  
Transition Alumina ◽  
Selective Conversion ◽  
Conversion Of Methane ◽  
Electron Paramagnetic ◽  
Alumina Supports

The selective conversion of methane to methanol remains one of the holy grails of chemistry, where Cu-exchanged zeolites have been shown to selectively convert methane to methanol under stepwise conditions. Over the years, several active sites have been proposed, ranging from mono-, di- to trimeric Cu(II). Herein, we report the formation of well-dispersed monomeric Cu(II) species supported on alumina using surface organometallic chemistry and their reactivity towards the selective and stepwise conversion of methane to methanol. Extensive studies using various transition alumina supports combined with spectroscopic characterization, in particular electron paramagnetic resonance (EPR), show that the active sites are associated with specific facets, which are typically found in gamma- and eta-alumina phase, and that their EPR signature can be attributed to species having a tri-coordinated [(Al<sub>2</sub>O)Cu<sup>II</sup>O(OH)]<sup>-</sup>,T-shape geometry. Overall, the selective conversion of methane to methanol, a two-electron process, involve two of these isolated monomeric Cu(II) sites that play in concert.

Aqueous phase conversion of CO2 into acetic acid over thermally transformed MIL-88B

2021 ◽  
Author(s):  
Waqar Ahmad ◽  
Paramita Koley ◽  
Swarit Dwivedi ◽  
Abhijit Shrotri ◽  
Akshat Tanksale
Keyword(s):  
Acetic Acid ◽  
Aqueous Phase ◽  
Carbon Emissions ◽  
Active Sites ◽  
Catalyst Recycling ◽  
Efficient Catalyst ◽  
Co Catalyst ◽  
Net Zero ◽  
Significant Difference ◽  
Zero Carbon

Abstract Sustainable production of acetic acid (AA) is a high priority due to its high global manufacturing capacity and numerous applications. Currently it is predominantly synthesized via carbonylation of methanol, in which both the reactants are fossil-derived. CO2 transformation into AA is highly desirable to achieve net zero carbon emissions, but significant challenges remain to achieve this efficiently. Herein, we report a heterogeneous catalyst, thermally transformed MIL-88B with Fe0 and Fe3O4 dual active sites, for highly selective AA formation via methanol hydrocarboxylation. This efficient catalyst showed high AA yield (590.1 mmol/gcat.L) with 81.7% selectivity at 150°C in aqueous phase using LiI as a co-catalyst. The reaction is believed to proceed via formic acid intermediate. No significant difference in AA yield and selectivity was noticed during catalyst recycling study up to five cycles. This work scalable and industrially relevant for CO2 utilisation to reduce carbon emissions, especially if green methanol and green hydrogen are used.

scholarly journals Biomimetic Cu/Nitroxyl Catalyst Systems for Selective Alcohol Oxidation

Catalysts ◽  
2019 ◽  
Vol 9 (5) ◽  
pp. 395 ◽  
Author(s):  
Lindie Marais ◽  
Andrew John Swarts
Keyword(s):  
Active Sites ◽  
Alcohol Oxidation ◽  
Galactose Oxidase ◽  
Co Catalyst ◽  
Co Catalysts ◽  
Mechanistic Pathway ◽  
Oxidation Of Alcohols ◽  
Catalyst Systems ◽  
Carbonyl Products

The oxidation of alcohols to the corresponding carbonyl products is an important organic transformation and the products are used in a variety of applications. The development of catalytic methods for selective alcohol oxidation have garnered significant attention in an attempt to find a more sustainable method without any limitations. Copper, in combination with 2,2,6,6-tetramethyl-1-piperidine N-oxyl (TEMPO) and supported by organic ligands, have emerged as the most effective catalysts for selective alcohol oxidation and these catalyst systems are frequently compared to galactose oxidase (GOase). The efficiency of GOase has led to extensive research to mimic the active sites of these enzymes, leading to a variety of Cu/TEMPO· catalyst systems being reported over the years. The mechanistic pathway by which Cu/TEMPO· catalyst systems operate has been investigated by several research groups, which led to partially contradicting mechanistic description. Due to the disadvantages and limitations of employing TEMPO· as co-catalyst, alternative nitroxyl radicals or in situ formed radicals, as co-catalysts, have been successfully evaluated in alcohol oxidation. Herein we discuss the development and mechanistic elucidation of Cu/TEMPO· catalyst systems as biomimetic alcohol oxidation catalysts.

scholarly journals Ethylene Oligomerization over Nickel Supported Silica-Alumina Catalysts with High Selectivity for C10+ Products

Catalysts ◽  
2020 ◽  
Vol 10 (2) ◽  
pp. 180 ◽  
Author(s):  
Lei Chen ◽  
Guangci Li ◽  
Zhong Wang ◽  
Shuangju Li ◽  
Mingjie Zhang ◽  
...  
Keyword(s):  
Reaction Temperature ◽  
Aging Temperature ◽  
Active Sites ◽  
High Selectivity ◽  
Acid Sites ◽  
Ethylene Oligomerization ◽  
Octahedral Coordination ◽  
Activation Temperature ◽  
High Aging Temperature ◽  
Silica Alumina

The nickel (II) loading silica-alumina under various treatments in terms of aging temperature, Si/Al ratio and activation temperature were investigated by XRD, N2 adsorption-desorption, TEM, UV-Vis, NH3-TPD and XRF and then applied to catalyze the ethylene oligomerization. High aging temperature, low Si/Al ratio and high activation temperature were beneficial to high selectivity for C10+ products because of a reasonable match between Ni active sites and acid sites, high Ni loading content and less octahedral coordination Ni2+ species, respectively. Ni loading content was more important than the number of acid sites for high yield of C10+ products, and less octahedral coordination Ni2+ species favored less by-products produced at high reaction temperature. In addition, other experimental conditions, such as reaction temperature, weight hourly space velocity (WHSV) and nickel precursor were discussed in the paper.

scholarly journals Enhanced Photocatalytic Hydrogen Production of the Polyoxoniobate Modified with RGO and PPy

Nanomaterials ◽  
2020 ◽  
Vol 10 (12) ◽  
pp. 2449
Author(s):  
Shiliang Heng ◽  
Lei Li ◽  
Weiwei Li ◽  
Haiyan Li ◽  
Jingyu Pang ◽  
...  
Keyword(s):  
Hydrogen Production ◽  
Active Sites ◽  
High Efficiency ◽  
Solvothermal Method ◽  
H2 Production ◽  
H2 Evolution ◽  
Co Catalyst ◽  
Photocatalytic Hydrogen Production ◽  
Reduced Graphene ◽  
One Step

The development of high-efficiency, recyclable, and inexpensive photocatalysts for water splitting for hydrogen production is of great significance to the application of solar energy. Herein, a series of graphene-decorated polyoxoniobate photocatalysts Nb6/PPy-RGO (Nb6 = K7HNb6O19, RGO = reduced graphene oxide, PPy = polypyrrole), with the bridging effect of polypyrrole were prepared through a simple one-step solvothermal method, which is the first example of polyoxoniobate-graphene-based nanocomposites. The as-fabricated photocatalyst showed a photocatalytic H2 evolution activity without any co-catalyst. The rate of 1038 µmol g−1 in 5 h under optimal condition is almost 43 times higher than that of pure K7HNb6O19·13H2O. The influencing factors for photocatalysts in photocatalytic hydrogen production under simulated sunlight were studied in detail and the feasible mechanism is presented in this paper. These results demonstrate that Nb6O19 acts as the main catalyst and electron donor, RGO provides active sites, and PPy acted as an electronic bridge to extend the lifetime of photo-generated carriers, which are crucial factors for photocatalytic H2 production.

Synthesis, Characterization, and Ethylene Oligomerization and Polymerization by 2-Quinoxalinyl-6-iminopyridine Chromium Chlorides

2008 ◽  
Vol 61 (5) ◽  
pp. 397 ◽  
Author(s):  
Saliu A. Amolegbe ◽  
Maliha Asma ◽  
Min Zhang ◽  
Gang Li ◽  
Wen-Hua Sun
Keyword(s):  
High Selectivity ◽  
Ethylene Oligomerization ◽  
Distorted Octahedral Geometry ◽  
Electronic Effects ◽  
X Ray Diffraction ◽  
Reaction Conditions ◽  
Co Catalyst ◽  
X Ray ◽  
Catalytic Activities ◽  
Distorted Octahedral

A series of chromium(iii) complexes ligated by N^N^N tridentate 2-quinoxalinyl-6-iminopyridine were synthesized and characterized by elemental analysis and infrared spectroscopy. Single-crystal X-ray diffraction analysis for the structure of complex C3 reveals a distorted octahedral geometry. When methylaluminoxane was employed as the co-catalyst, the chromium complexes showed high activities for ethylene oligomerization and polymerization. The distribution of oligomers obtained followed Schulz–Flory rules with high selectivity for α-olefins. Both steric and electronic effects of coordinated ligands affected the catalytic activities as well as the properties of the catalytic products. The parameters of the reaction conditions were also investigated to explore the optimum catalytic potentials of these complexes.

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