Syngas Reactions Research Articles

Manganese-rhodium nanoparticles: Adsorption on titanium oxide surfaces and catalyst for syngas reactions.

Manganese-rhodium (Mn-Rh) nanoparticles have emerged as a promising candidate for catalytic applications in the production of syngas, a critical precursor for a wide range of industrial processes. This study employs a comprehensive, theoretical, and computational approach to investigate the structural and electronic properties of Mn-Rh nanoparticles, with a specific focus on their interaction with titanium oxide (TiO2) surfaces and their potential as catalysts for syngas reactions. The density functional theory calculations are employed to explore the adsorption behavior of Mn-Rh nanoparticles on TiO2 surfaces. By analyzing the adsorption energies, geometries, and electronic structure at the nanoscale interface, we provide valuable insights into the stability and reactivity of Mn-Rh nanoparticles when immobilized on TiO2 supports. Furthermore, the catalytic performance of Mn-Rh nanoparticles in syngas production is thoroughly examined. Through detailed reaction mechanism studies and kinetic analysis, we elucidate the role of Mn and Rh in promoting syngas generation via carbon dioxide reforming and partial oxidation reactions. The findings demonstrate the potential of Mn-Rh nanoparticles as efficient catalysts for these crucial syngas reactions. This research work not only enhances our understanding of the fundamental properties of Mn-Rh nanoparticles but also highlights their application as catalysts for sustainable and industrially significant syngas production.

ChemInform Abstract: Mn‐, Fe‐, and Co‐Catalyzed Radical Hydrofunctionalizations of Olefins

AbstractReview: 476 refs.

Mn-, Fe-, and Co-Catalyzed Radical Hydrofunctionalizations of Olefins.

Cofactor-mimetic aerobic oxidation has conceptually merged with catalysis of syngas reactions to form a wide range of Markovnikov-selective olefin radical hydrofunctionalizations. We cover the development of the field and review contributions to reaction invention, mechanism, and application to complex molecule synthesis. We also provide a mechanistic framework for understanding this compendium of radical reactions.

Computational Identification of Descriptors for Selectivity in Syngas Reactions on a Mo2C Catalyst

A microkinetic model containing 53 elementary steps based on extensive Density Functional Theory calculations is developed to describe syngas reactions on a Mo2C catalyst under high temperature and pressure conditions, with the aim of determining the elementary steps that control reaction selectivity. The effects of adsorbate–adsorbate interactions are found to be strong, so these interactions are described using the quasi-chemical approximation. Agreement with experimental observations of selectivity for syngas reactions at P = 30 bar and T = 573 K was found to be good without parametrizing the model in any way to the experimental reaction data. The activation energies of the elementary steps in the model were estimated using a Bronsted–Evans–Polanyi relation, and sensitivity analysis is used to examine the impact of uncertainties in this relation on the selectivity-determining steps of the reaction network. Our results are a useful example of identification of key elementary steps in a complex reaction ...

CFD modeling using heterogeneous reaction kinetics for catalytic dehydrogenation syngas reactions in a fixed-bed reactor

A comprehensive 2D computational fluid dynamics (CFD) model was developed to simulate the flow behavior and catalytic dehydrogenation reaction of syngas in a heterogenous fixed-bed reactor (FBR). The model combined the porous medium CFD model with a reaction kinetics model. To acquire an accurate reaction kinetics model, a comprehensive reaction mechanism was studied for the heterogeneous catalytic dehydrogenation reaction of syngas over a supported metal catalyst. Based on the reaction mechanism and a statistical test, a reliable kinetics model was proposed. The CFD model combined with the above kinetics model was validated with one set of experimental data. The CFD model was also used to predict key reaction variable distributions such as the temperature and the component concentrations in the reactor.

Elementary steps of syngas reactions on Mo2C(0 0 1): Adsorption thermochemistry and bond dissociation

Density functional theory (DFT) and ab initio thermodynamics are applied in order to investigate the most stable surface and subsurface terminations of Mo2C(001) as a function of chemical potential and in the presence of syngas. The Mo-terminated (001) surface is then used as a model surface to evaluate the thermochemistry and energetic barriers for key elementary steps in syngas reactions. Adsorption energy scaling relations and Brønsted–Evans–Polanyi relationships are established and used to place Mo2C into the context of transition metal surfaces. The results indicate that the surface termination is a complex function of reaction conditions and kinetics. It is predicted that the surface will be covered by either C2H2 or O depending on conditions. Comparisons with transition metals indicate that the Mo-terminated Mo2C(001) surface exhibits carbon reactivity similar to transition metals such as Ru and Ir, but is significantly more reactive toward oxygen. This explains some previous observations for Mo2C catalysts and suggests that Mo2C may exhibit unique and potentially useful reactivity or selectivity patterns.

ChemInform Abstract: Syngas Reactions. Part 14. Amidocarbonylation as a Route to α- Amidocarboxylic Acids.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Step sites in syngas catalysis

Step sites play an important role in many catalytic reactions. This paper reviews recent results on metal catalysts for syngas reactions with emphasis on steam reforming. Modern characterization techniques (STEM, HREM...) and theoretical calculations (DFT) has allowed a more quantitative explanation of the impact of step sites on catalyst activity and side reactions such as carbon formation. This leads to a discussion of principles for catalyst promotion.

Mixed iron-rhodium carbidocarbonyl clusters on oxide supports: chemistry and catalysis of syn-gas reactions

Genesis of silica-supported [Fe 5RhC(CO) 16] − and [Fe 4RhC(CO) 14] − clusters with interstitial carbon atoms have been investigated in CO, syn-gas and Ar media. Complete conversion of the former cluster to the latter was obtained at 50°C in any medium, with [Fe 4RhC(CO) 14] − cluster yielding Fe 4Rh 2C(CO) 16 and [Fe 3Rh 3C(CO) 15] − mixtures at 100–150°C. Simultaneously, Fe 2+ ions emerged on the SiO 2 surface. Mössbauer and electron microscopic studies on the silica-deposited clusters showed that at treatment in any medium in the range of 250–350°C highly dispersed FeRh particles are located on the silica surface, where Fe atoms exist mainly in the oxidized state even after H 2 reduction. Silica-supported catalysts derived from a family of FeRh carbidocarbonyl clusters were found to exhibit increased activity and selectivity toward oxygenates in CO hydrogenation and C 3H 6 hydroformylation compared to those of monometallic cluster-derived catalysts. Possible explanations are discussed.

Synthesis of C1–C5 alcohols on modified Co−Cu−Y based catalysts

Syngas reactions have been performed under pressure (6 MPa) on Co−Y and Co−Cu−Y catalysts with the intent to obtain good conversions and high C2−C5 alcohol selectivities. The addition of MoOx promotes the alcohol production and stabilizes the catalysts. TPR experiments indicate clearly the strong interaction between Co, Cu and Mo and XRD data show that MoOx prevents structural damage during the ageing.

Syngas reactions over Rh/SiO2 at high pressure and temperature studied by Fourier-transform infrared spectroscopy

In situ FTIR spectra are reported of Rh/SiO2 at 473, 503, 523 and 553 K exposed to CO–H2 mixtures with CO : H2 ratios of 1 : 14 and 14 : 1 and a total pressure of 1.5 MN m–2 and also with a CO : H2 ratio of 1 : 2 and a total gas pressure of 0.3–5.0 MPa. The dominant detectable products were adsorbed CO on Rh, OMe and OEt groups on silica, CH4(g) and adsorbed higher hydrocarbon. Selectivities varied widely from ca. 100% to methoxy/methanol for the 1 : 14 ratio at 473 K to ca. 100% to higher hydrocarbon for the 14 : 1 ratio at 523 K. The dominant factor influencing selectivity was the CO : H2 ratio, although temperature, total gas pressure and time of reaction also had an effect. Selectivity to methanol rather than ethanol was favoured by low temperature and high pressure.

有機金属錯体の合成と反応による合成ガス反応機構の解明

Mechanisms of syngas reactions which produce a wide variety of organic compounds including hydrocarbons and oxygenates and consist of multi-step elementary transformations have been studied by employing organometallic model compounds. Since the three plausible reaction mechanisms proposed on the basis of previous catalytic studies may be recognized as combinations of two reaction stages, that is, (1) reduction of coordinated CO into CHx and CHxO species and (2) carbon-chain elongation step, model reactions have been reviewed according to the two aspects. In addition, results of the reduction of organometallic compounds using hydrosilanes or hydrostannanes in place of dihydrogen are also briefly summarized. Such reducing agents turn out to be effective for the reduction of oxygen-containing intermediates and, as a result, new model systems for production of alkanes, alcohols, aldehydes, and ethylene have been established.

Syngas reactions: XIV. Amidocarbonylation as a route to α-aminocarboxylix acids

The amidocarbonylation of olefin and aldehyde substrates has been applied to the synthesis of a variety of amidocarboxylic acids, including surface active agents (e.g. C 14C 16 N-acyl-α-amino acids), specialty surfactants (such as the sarcosinates), intermediates for sweeteners (e.g. aspartame), food additives (e.g. glutamic acid), and certain chelating agents. Homogeneous cobalt and rhodium-based catalysts, modified, for example, with sulfoxide and bidentate phosphine ligands, have been tailored to the synthesis of each individual class of product. Process studies, including examinations of reaction rate, product selectivity, as well as catalyst stability, have been undertaken for N-acetylglycine and amino acid surfactant syntheses.

Promotion and support effects in syngas reactions

A short review is presented on the problems of selectivity in the syngas reaction. Attention is mainly given to the role of promoters in these reactions. Several mechanisms of promotion are critically reviewed and analyzed.

Syngas reactions XII. The selective preparation of acetaldehyde, alkanols, esters and acetic acid from synthesis gas

AbstractSeveral classes of commercially important oxygenates, including acetaldehyde, ethanol, methyl acetate, ethyl acetate and acetic acid as well as C1–C3alcohol/acetate ester mixtures, may each be selectivelygenerated from synthesis gas through the application of novel classes of ruthenium‐containing bimetallic catalysts particularly those of ruthenium and cobalt (RuCo). A particular feature of these versatile catalysts is that all precursors are iodidefree. Products are formed through a combination of carbon monoxide hydrogenation, methanol homologation, methyl acetate homologation and methanol carbonylation reaction sequences.

ChemInform Abstract: On Some Problems of Selectivity in Syngas Reactions on the Group VIII Metals

ChemInformVolume 19, Issue 33 Reviews ChemInform Abstract: On Some Problems of Selectivity in Syngas Reactions on the Group VIII Metals G. VAN DER LEE, G. VAN DER LEE Gorlaeus Lab., State Univ., 2300 RA Leiden, NetherlandsSearch for more papers by this authorV. PONEC, V. PONEC Gorlaeus Lab., State Univ., 2300 RA Leiden, NetherlandsSearch for more papers by this author G. VAN DER LEE, G. VAN DER LEE Gorlaeus Lab., State Univ., 2300 RA Leiden, NetherlandsSearch for more papers by this authorV. PONEC, V. PONEC Gorlaeus Lab., State Univ., 2300 RA Leiden, NetherlandsSearch for more papers by this author First published: August 16, 1988 https://doi.org/10.1002/chin.198833364Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume19, Issue33August 16, 1988 RelatedInformation

On Some Problems of Selectivity in Syngas Reactions on the Group VIII Metals

Abstract There are probably very few other systems in industrial chemistry which equal the CO/H2 reaction system in the variety of possible products. When using pure Ni or Co catalysts one can produce almost pure CH, or a mixture of saturated hydrocarbons; a promoted (K2O) iron catalyst produces, in addition to these products, also alcohols, aldehydes, and other oxygen-containing products (oxygenates); and almost pure CH3OH can be obtained when applying Cu/ZnO/Al2O3 or Pd-MgO promoted SiO2 catalysts. Some catalysts (Rh/V2O3) can lead the reaction of syngas toward C2-oxygenates, and others to a mixture of C2+-alcohols and aldehydes (Co, K, Cr, Fe multicomponent catalysts). All this is schematically shown in Fig. 1. It is a remarkable, but not unusual, situation that while the economic interest follows the order (Fig. 1) III > II > I, the fundamental knowledge on the reactions mentioned follows just the reverse order: I > II > III. Although the leading ideas for preparing selective catalysts are onIy slowly emerging from the experimental material published recently, it nevertheless seems appropriate to review the preliminary information already available on the selective behavior of various group VIII metals.

Selectivity of Rh catalysts in the syngas reactions. On the role of supports and promoters

Catalysts selective for C 2-oxygenates can be prepared based on rhodium. However, a support and/or promoter is essential. It is shown that with V 2O 3 as a support, selective catalysts are only obtained when during preparation (wet steps, high temperature reduction) species are formed which finally appear on the metal surface. Blocking of the Rh surface has been observed by IR spectra of adsorbed CO and by determination of the CO/Rh ratio. UV/VIS and ESR spectra show that by interaction of V 2O 3 with various chlorides or HCl, VOCl 2·5H 2O is formed. This compound can be reduced into VOCl which is rather stable. Selective catalysts can also be prepared by adding VOCl 2 to a non-selective Rh/Aerosil catalyst.

Manipulation of the selectivity of rhodium by the use of supports and promoters

An attempt is made to classify the promotion effects in catalysis by metals. The example of rhodium catalysts is used to show how the selectivity can be manipulated by using supports and promoters. The results presented demonstrate how the promoter can be created from the support during the impregnation process. In syngas reactions the main function of the promoter thus formed, or of a promoter added to the metal carried by an inert support, is to activate CO for insertion and/or to stabilize intermediates formed by this insertion.

ChemInform Abstract: On the Selectivity of Rh Catalysts in the Formation of Oxygenates.

AbstractIn order to gain information on the factors which determine the selectivity ofcatalysts in the syngas reactions, a number of Rh catalysts with various carriers have been studied.