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Catalysts
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Small Molecule Activation and Catalysis
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Small Molecule Activation and Catalysis

A special issue of Catalysts (ISSN 2073-4344). This special issue belongs to the section "Catalytic Materials".

Deadline for manuscript submissions: closed (15 March 2017) | Viewed by 54209

Special Issue Editor

Prof. Dr. Rajendra S. Ghadwal

E-Mail Website
Guest Editor
Molecular Inorganic Chemistry and Catalysis, Fakultät für Chemie, Universität Bielefeld, Universitätsstr. 25, D-33615 Bielefeld, Germany
Interests: carbon-donor ligands; organometallic catalysis; open-shell (nontransition metals) molecules; molecular materials derived from stable radicals/π-conjugated systems; small molecule activation and functionalization; low-valent main-group chemistry; main-group catalysis; computational calculations; multireference methods
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Small molecules such as N2, O2, and CO2 are ubiquitous and frequently take part in element cycles and various metabolic processes. Moreover, these molecules are abundant reservoirs of chemical energy. Selective functionalization (and derivatization) of such molecules (including CO and CH4) into value-added products, as well as developing energy-efficient strategies for H2 production, holds promise for addressing current sustainability issues.  Such small molecules, however, feature rather inert bonds and their activation depends largely on overcoming often quite significant kinetic barriers. New catalytic approaches of small molecule activation and their efficient utilization are therefore of high interest.

Innovative strategies of small molecule activation and functionalization are very important and highly desired for developing more economic and environmentally more benign synthetic methods. This special issue on “Small Molecule Activation and Catalysis” aims to compile cutting-edge research in small molecule activation and functionalization mediated by molecular species (main group and transition metal compounds), either in a sub-stoichiometric or catalytic fashion. Experimental and theoretical findings underlining the fundamental principles of small molecule activation and functionalization will be emphasized. Topics including (i) functionalization of organic substrates by using CO2 and CO (e.g., carbonylation); (ii) use of CO2 as a C1-feedstock; (iii) selective C–H bond functionalization with O2, N2O, NH3; (iv) N2 (NO and N2O) binding and reduction, (v) O2 binding and activation, and (vi) catalytic H2O splitting will be covered. Original results providing new insights into small molecule activation and catalytic transformations are particularly welcome.

Dr. Rajendra S. Ghadwal
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Catalysts is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2700 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • Small molecules
  • Bond activation and functionalization
  • Synthesis
  • Structure-reactivity
  • Catalysis
  • Theoretical study
  • Mechanistic insight
  • Carbon dioxide reduction
  • CO2 sequestration
  • Carbon monoxide reduction
  • Sustainability
  • Dihydrogen splitting
  • Dihydrogen generation
  • Hydrogenation
  • Hydroamination
  • Oxidation with N2O or O2
  • C–H bond activation/ functionalization of CH4

Published Papers (6 papers)

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Research

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1580 KiB  
Article
Reactivity of Copper Electrodes towards Functional Groups and Small Molecules in the Context of CO2 Electro-Reductions
by Bernhard Schmid, Christian Reller, Sebastian S. Neubauer, Maximilian Fleischer, Romano Dorta and Guenter Schmid
Catalysts 2017, 7(5), 161; https://doi.org/10.3390/catal7050161 - 18 May 2017
Cited by 27 | Viewed by 7690
Abstract
The direct electro-reduction of CO2 to functional molecules like ethene is a highly desirable variant of CO2 utilization. The formation of, for example, ethene from CO2 is a multistep electrochemical process going through various intermediates. As these intermediates are organic [...] Read more.
The direct electro-reduction of CO2 to functional molecules like ethene is a highly desirable variant of CO2 utilization. The formation of, for example, ethene from CO2 is a multistep electrochemical process going through various intermediates. As these intermediates are organic species, the CO2 reducing electro-catalyst has to be competent for a variety of organic functional group transformations to yield the final product. In this work, the activity of an in situ-grown nano-structured copper catalyst towards a variety of organic functional group conversions was studied. The model reagents were selected from the product spectrum of actual CO2 reduction reaction (CO2RR) experiments and from proposals in the literature. The CO2 bulk electrolysis benchmark was conducted at 170 mAcm−2 current density with up to 43% Faradaic Efficiency (FE) for ethene and 23% FE for ethanol simultaneously. To assure relevance for application-oriented conditions, the reactivity screening was conducted at elevated current densities and, thus, overpotentials. The found reactivity pattern was then also transferred to the CO reduction reaction (CORR) under benchmark conditions yielding additional insights. The results suggest that at high current density/high overpotential conditions, also other ethene formation pathways apart from acetaldehyde reduction such as CH2 dimerization are present. A new suggestion for a high current density mechanism will be presented, which is in agreement with the experimental observations and the found activity pattern of copper cathodes toward organic functional group conversion. Full article
(This article belongs to the Special Issue Small Molecule Activation and Catalysis)
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5358 KiB  
Article
Preparation of Rh/Ni Bimetallic Nanoparticles and Their Catalytic Activities for Hydrogen Generation from Hydrolysis of KBH4
by Liqiong Wang, Liang Huang, Chengpeng Jiao, Zili Huang, Feng Liang, Simin Liu, Yuhua Wang and Haijun Zhang
Catalysts 2017, 7(4), 125; https://doi.org/10.3390/catal7040125 - 23 Apr 2017
Cited by 20 | Viewed by 5595
Abstract
ISOBAM-104 protected Rh/Ni bimetallic nanoparticles (BNPs) of 3.1 nm in diameter were synthesized by a co-reduction method with a rapid injection of KBH4 solution. The catalytic activities of as-prepared BNPs for hydrogen generation from hydrolysis of a basic KBH4 solution were [...] Read more.
ISOBAM-104 protected Rh/Ni bimetallic nanoparticles (BNPs) of 3.1 nm in diameter were synthesized by a co-reduction method with a rapid injection of KBH4 solution. The catalytic activities of as-prepared BNPs for hydrogen generation from hydrolysis of a basic KBH4 solution were evaluated. Ultraviolet-visible spectrophotometry (UV-Vis), transmission electron microscopy (TEM), and high-resolution transmission electron microscopy (HRTEM) were employed to characterize the structure, particle size, and chemical composition of the resultant BNPs. Catalytic activities for hydrolysis of KBH4 and catalytic kinetics of prepared BNPs were also investigated. It was shown that Rh/Ni BNPs displayed much higher catalytic activities than that of Rh or Ni monometallic nanoparticles (MNPs), and the prepared Rh10Ni90 BNPs possessed the highest catalytic activities with a value of 11580 mol-H2·h−1·mol-Rh−1. The high catalytic activities of Rh/Ni BNPs could be attributed to the electron transfer effect between Rh and Ni atoms, which was confirmed by a density functional theory (DFT) calculation. The apparent activation energy for hydrogen generation of the prepared Rh10Ni90 BNPs was about 47.2 ± 2.1 kJ/mol according to a kinetic study. Full article
(This article belongs to the Special Issue Small Molecule Activation and Catalysis)
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3741 KiB  
Article
Promotive Effect of Sn2+ on Cu0/Cu+ Ratio and Stability Evolution of Cu/SiO2 Catalyst in the Hydrogenation of Dimethyl Oxalate
by Chuancai Zhang, Denghao Wang and Bin Dai
Catalysts 2017, 7(4), 122; https://doi.org/10.3390/catal7040122 - 19 Apr 2017
Cited by 9 | Viewed by 5518
Abstract
The influence of Sn2+doping on the structure and performance of silica supported copper catalyst was systematically investigated and characterised. Catalytic evaluation showed that the suitable content of Sn2+ introduced into a Cu/SiO2 catalyst evidently improved the catalytic activity and [...] Read more.
The influence of Sn2+doping on the structure and performance of silica supported copper catalyst was systematically investigated and characterised. Catalytic evaluation showed that the suitable content of Sn2+ introduced into a Cu/SiO2 catalyst evidently improved the catalytic activity and stability of ethylene glycol synthesis from dimethyl oxalate. X-ray diffraction and X-ray auger electron spectroscopy indicated that the Cu0/Cu+ ratio gradually increased with increasing Sn2+ content, and an appropriate proportion of Cu0/Cu+ ratio played a very significant role in this reaction. Transmission electron microscopy revealed that the active copper particles in the Cu-xSn/SiO2 catalyst were smaller than those of the Cu/SiO2 catalyst. This result may be due to the introduction of Sn2+ species transformed into SnO2. Furthermore, SnO2 effectively segregated the active copper. These effects are beneficial in inhibiting the aggregation of copper in the catalysts, thereby improving the stability of the catalyst and prolonging the life span. Full article
(This article belongs to the Special Issue Small Molecule Activation and Catalysis)
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5292 KiB  
Article
Reactor Design for CO2 Photo-Hydrogenation toward Solar Fuels under Ambient Temperature and Pressure
by Chun-Ying Chen, Joseph Che-Chin Yu, Van-Huy Nguyen, Jeffrey Chi-Sheng Wu, Wei-Hon Wang and Kamila Kočí
Catalysts 2017, 7(2), 63; https://doi.org/10.3390/catal7020063 - 16 Feb 2017
Cited by 23 | Viewed by 9279
Abstract
Photo-hydrogenation of carbon dioxide (CO2) is a green and promising technology and has received much attention recently. This technique could convert solar energy under ambient temperature and pressure into desirable and sustainable solar fuels, such as methanol (CH3OH), methane [...] Read more.
Photo-hydrogenation of carbon dioxide (CO2) is a green and promising technology and has received much attention recently. This technique could convert solar energy under ambient temperature and pressure into desirable and sustainable solar fuels, such as methanol (CH3OH), methane (CH4), and formic acid (HCOOH). It is worthwhile to mention that this direction can not only potentially depress atmospheric CO2, but also weaken dependence on fossil fuel. Herein, 1 wt % Pt/CuAlGaO4 photocatalyst was successfully synthesized and fully characterized by ultraviolet-visible light (UV-vis) spectroscopy, X-ray diffraction (XRD), Field emission scanning electron microscopy using energy dispersive spectroscopy analysis (FE-SEM/EDS), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and Brunauer-Emmett-Teller (BET), respectively. Three kinds of experimental photo-hydrogenation of CO2 in the gas phase, liquid phase, and gas-liquid phase, correspondingly, were conducted under different H2 partial pressures. The remarkable result has been observed in the gas-liquid phase. Additionally, increasing the partial pressure of H2 would enhance the yield of product. However, when an extra amount of H2 is supplied, it might compete with CO2 for occupying the active sites, resulting in a negative effect on CO2 photo-hydrogenation. For liquid and gas-liquid phases, CH3OH is the major product. Maximum total hydrocarbons 8.302 µmol·g−1 is achieved in the gas-liquid phase. Full article
(This article belongs to the Special Issue Small Molecule Activation and Catalysis)
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3492 KiB  
Article
An Alumina-Supported Ni-La-Based Catalyst for Producing Synthetic Natural Gas
by Daniel E. Rivero-Mendoza, Jessica N. G. Stanley, Jason Scott and Kondo-François Aguey-Zinsou
Catalysts 2016, 6(11), 170; https://doi.org/10.3390/catal6110170 - 31 Oct 2016
Cited by 38 | Viewed by 10233
Abstract
LaNi5, known for its hydrogen storage capability, was adapted to the form of a metal oxide-supported (γ-Al2O3) catalyst and its performance for the Sabatier reaction assessed. The 20 wt % La-Ni/γ-Al2O3 particles were prepared [...] Read more.
LaNi5, known for its hydrogen storage capability, was adapted to the form of a metal oxide-supported (γ-Al2O3) catalyst and its performance for the Sabatier reaction assessed. The 20 wt % La-Ni/γ-Al2O3 particles were prepared via solution combustion synthesis (SCS) and exhibited good catalytic activity, achieving a CO2 conversion of 75% with a high CH4 selectivity (98%) at 1 atm and 300 °C. Characteristics of the La-Ni/γ-Al2O3 catalyst were identified at various stages of the catalytic process (as-prepared, activated, and post-reaction) and in-situ DRIFTS was used to probe the reaction mechanism. The as-prepared catalyst contained amorphous surface La–Ni spinels with particle sizes <6 nm. The reduction process altered the catalyst make-up where, despite the reducing conditions, Ni2+-based particles with diameters between 4 and 20 nm decorated with LaOx moieties were produced. However, the post-reaction catalyst had particle sizes of 4–9 nm and comprised metallic Ni, with the LaOx decoration reverting to a form akin to the as-prepared catalyst. DRIFTS analysis indicated that formates and adsorbed CO species were present on the catalyst surface during the reaction, implying the reaction proceeded via a H2-assisted and sequential CO2 dissociation to C and O. These were then rapidly hydrogenated into CH4 and H2O. Full article
(This article belongs to the Special Issue Small Molecule Activation and Catalysis)
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Review

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1289 KiB  
Review
A Review on Selective Catalytic Reduction of NOx by NH3 over Mn–Based Catalysts at Low Temperatures: Catalysts, Mechanisms, Kinetics and DFT Calculations
by Fengyu Gao, Xiaolong Tang, Honghong Yi, Shunzheng Zhao, Chenlu Li, Jingying Li, Yiran Shi and Xiaomi Meng
Catalysts 2017, 7(7), 199; https://doi.org/10.3390/catal7070199 - 29 Jun 2017
Cited by 191 | Viewed by 13962
Abstract
It is a major challenge to develop the low–temperature catalysts (LTC, <250 °C) with excellent efficiency and stability for selective catalytic reduction (SCR) of NOx by NH3 from stationary sources. Mn-based LTC have been widely investigated due to its various valence [...] Read more.
It is a major challenge to develop the low–temperature catalysts (LTC, <250 °C) with excellent efficiency and stability for selective catalytic reduction (SCR) of NOx by NH3 from stationary sources. Mn-based LTC have been widely investigated due to its various valence states and excellent redox performance, while the poisoning by H2O or/and SO2 is one of the severe weaknesses. This paper reviews the latest research progress on Mn-based catalysts that are expected to break through the resistance, such as modified MnOx–CeO2, multi-metal oxides with special crystal or/and shape structures, modified TiO2 supporter, and novel carbon supporter (ACF, CNTs, GE), etc. The SCR mechanisms and promoting effects of redox cycle are described in detail. The reaction kinetics will be a benefit for the quantitative study of Eley–Rideal (ER) and Langmuir–Hinshelwood (LH) mechanisms. This paper also introduces the applications of quantum-chemical calculation using density functional theory to analyze the physic-chemical properties, explicates the reaction and poisoning mechanisms, and directs the design of functional catalysts on molecule levels. The intensive study of H2O/SO2 inhibition effects is by means of the combination analysis of in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and density functional theory (DFT), and the amplification of tolerance mechanisms will be helpful to design an excellent SCR catalyst. Full article
(This article belongs to the Special Issue Small Molecule Activation and Catalysis)
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