Catalyst Characterization Studies Research Articles

A More General Approach to Distinguishing "Homogeneous" from "Heterogeneous" Catalysis: Discovery of Polyoxoanion- and Bu4N+-Stabilized, Isolable and Redissolvable, High-Reactivity Ir.apprx.190-450 Nanocluster Catalysts

A more general approach to distinguishing between so-called homogeneous vs heterogeneous catalysts has been developed and intrinsically tested in answering the question {open_quotes}what is the true catalyst in the active hydrogenation system which evolves from cyclohexene, hydrogen, and the discrete, polyoxoanion-supported Ir(I) catalyst precursor (Bu{sub 4}N){sub 5}Na{sub 3}[(1,5-COD)Ir{sm_bullet}P{sub 2}W{sub 15}Nb{sub 3}O{sub 62}]?{close_quotes}. The approach developed and utilized consists of four categories of experiments: (I) catalyst isolation and characterization studies, with an emphasis on TEM; (II) initial kinetic studies, emphasizing whether or not the isolated catalyst can account for the observed kinetics, especially any induction period seen, and whether or not the reaction exhibits a {plus_minus}10% reproducible rate; (III) quantitative phenomenological catalyst poisoning and recovery experiments; (IV) additional kinetic and mechanistic studies and chemical tests, all interpreted with strict adherence to the principle that the correct description of the catalyst (i.e., the correct mechanism) will explain all of the data. The present approach has identified a previously unknown type of hybrid homogeneous-heterogeneous, Ir{sub {approximately}190-450}{sm_bullet}polyoxoanion/Bu{sub 4}N{sup +} catalyst of average composition [Ir(0){sub {approximately}300}(P{sub 4}W{sub 30}Nb{sub 6}O{sub 123}{sup 16{minus}}){sub {approximately}33}](Bu{sub 4}N){sub {approximately}300}Na{sub {approximately}233}.

Production of Hydrogen from Methanol. Part 1. Catalyst Characterization Studies

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTProduction of Hydrogen from Methanol. Part 1. Catalyst Characterization StudiesRaphael O. Idem and Narendra N. BakhshiCite this: Ind. Eng. Chem. Res. 1994, 33, 9, 2047–2055Publication Date (Print):September 1, 1994Publication History Published online1 May 2002Published inissue 1 September 1994https://doi.org/10.1021/ie00033a005RIGHTS & PERMISSIONSArticle Views360Altmetric-Citations38LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (2 MB) Get e-Alerts Get e-Alerts

Characterization studies of plasma-sprayed cobalt and iron catalysts

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTCharacterization studies of plasma-sprayed cobalt and iron catalystsAjay K. Dalai, Narendra N. Bakhshi, and M. Nabil EsmailCite this: Ind. Eng. Chem. Res. 1992, 31, 6, 1449–1457Publication Date (Print):June 1, 1992Publication History Published online1 May 2002Published inissue 1 June 1992https://doi.org/10.1021/ie00006a005RIGHTS & PERMISSIONSArticle Views132Altmetric-Citations7LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (2 MB) Get e-Alerts Get e-Alerts

ChemInform Abstract: Oxidative Coupling of Methane on Alkali Metal‐Promoted Nickel Titanate. Part 1. Catalyst Characterization and Transient Studies.

AbstractThe oxidative coupling of CH4 to give ethane and ethylene is promoted by addition of Li or Na to the rather inactive NiTiO3 catalyst up to yields of ca. 13% with ca. 70% selectivity.

Oxidative coupling of methane on alkali metal-promoted nickel titanate: I. Catalyst characterization and transient studies

Nickel titanate, a mixed oxide with ilmenite structure, develops activity for methane oxidative coupling reaction upon promotion with alkaline metals (Li, Na, K). Typically, higher hydrocarbon yields of ca. 13% with ca. 70% selectivity can be obtained with a 9.7% Li/NiTiO 3 catalyst and C 2 + yields of ca. 8% with ca. 60% selectivity with a 22% Na/NiTiO 3 catalyst. Transient experiments involving steps, pulses, and steady-state isotopic switches indicate that while on a 9.7% Li/NiTiO 3 catalyst the activity is mainly related to lattice oxygen, there is little lattice oxygen involvement in oxidative coupling over sodium-loaded nickel titanate. Isotopic switch results revealed that carbon dioxide interacts strongly with both lithium- and sodium-promoted surfaces, but the concentration of long-lived adsorbed methane is too low to be differentiated from the interaction of argon with the surface. X-ray diffraction and BET results indicate that increasing the degree of alkali metal loading lowers the surface area and creates different phases after pretreatment at elevated temperatures. X-ray photoelectron spectroscopy revealed that different types of carbon and oxygen species are present on the surface.

Mössbauer spectroscopy cell for i n s i t u catalyst characterization and reaction kinetics studies at high pressures

A stainless steel cell with beryllium windows has been used for carrying out in situ Mössbauer spectroscopy studies (with a vertical γ-ray beam) at pressures up to 6.8 MPa and temperatures up to 773 K. The downflow of gas through the powdered catalyst sample minimizes bulk gas phase concentration gradients in the cell above the catalyst layer, and this allows reaction kinetics measurements to be routinely analyzed. Incorporation of a prereactor and/or postreactor makes it possible to model longitudinal variations of catalyst states in a packed catalyst bed.

Catalyst characterization studies on the ZnCrFe oxide system

Basic catalyst characterization studies of the title system were carried out to gain insight into the unique nature of zinc-chromium ferrite for the oxidative dehydrogenation of butene to butadiene. Relative reactivities of the various oxides in hydrogen and butene at temperatures up to 550 °C were determined by measuring catalyst weight loss in a flow, microbalance reactor. The ease of reducibility of oxide in hydrogen decreases in the following order: Fe 2O 3 > ZnFe 2O 4 > ZnCrFeO 4 = FeCrO 3 > ZnCr 2O 4 > ZnO > Cr 2O 3. In butene, Fe 2O 3 and FeCrO 3 are reduced to lower-valence oxides, while ZnFe 2O 4, and ZnCrFeO 4 lose approximately 2 monolayers of oxygen. Noteworthy is the fact that the latter are selective catalysts for butene dehydrogenation. In the presence of both butene and air at 350 °C, the ZnCrFeO 4 catalyst at first rapidly gains weight, and then lines out. A carbonaceous deposit is present during the steady-state catalytic reaction while the catalyst remains essentially in the oxidized state. Regeneration in air returns the catalyst to its original weight. A surface reaction sequence for the oxidation dehydrogenation involving an iron-oxygen radical active center is proposed.