Catalysts Of Different Compositions Research Articles

Multiple active sites for glucose conversion identified in Sn-Beta catalysts by CPMG MAS NMR and operando UV-Vis spectroscopy

Sn-Beta is an emerging heterogeneous zeolite catalyst that displays high activity for the catalytic conversion of glucose to desirable bio-based chemicals. Due to its promising catalytic properties, the synthesis and characterisation of Sn-Beta catalysts of different composition and preparation method have been the subject of a great number of studies. However, development of structure-activity-lifetime relationships for glucose conversion chemistry has been obstructed by several challenges, making the tailored preparation of high performance Sn-Beta catalysts harder to achieve. In this manuscript, we undertake continuous kinetic studies of four different Sn-Beta catalysts for glucose conversion, and pair the kinetic insights obtained with operando UV-Vis spectroscopy and quantitative 119Sn CPMG MAS NMR. In doing so, we reveal that at least two types of Sn species that are active for glucose conversion can exist in Sn-Beta catalysts, but that the two Sn species exhibit different levels of activity, selectivity and stability. In particular, we find that a Sn species resonating at − 690 ppm is characterised by high activity and is primarily selective towards the isomerisation of glucose to fructose, whereas a second Sn species resonating at − 658 ppm is characterised by lower activity for glucose conversion, and preferential selectivity towards alkylation and β-dehydration. Our studies also demonstrate that both Sn sites also possess different levels of stability during continuous operation. Consequently, we reveal that it is the ratio amongst these species that governs the overall catalytic performances of Sn-Beta catalysts for biomass conversion processes.

INVESTIGATION OF THE EFFECT OF Co ON Ni/Al2O3 CATALYST FOR METHANE CARBONATE CONVERSION

In the work, the activated Ni-Co catalyst for the conversion of methane to carbonates was prepared by placing γ-Аl2О3 in solutions of nickel and cobalt nitrates. The time dependence of methane conversion was studied for different catalysts. In these processes, CО2/CH4=1:1,41 1 ratio was obtained. As a result of the research conducted, the methane effect of Co on Ni/Al2O3 catalyst for conversion. The following possible mechanism was proposed. The purpose of the work is to study the effect of Co on the conversion of methane to carbonate, and the dependence of these processes on catalysts of different compositions, time and temperatures.

Increasing electrocatalytic nitrate reduction activity by controlling adsorption through PtRu alloying

Nitrate produced from industrial and agricultural processes has imbalanced the global nitrogen cycle. Electrocatalytic reduction is a sustainable route to remediate nitrate while generating products such as ammonia or N2. Here we report the surface-area normalized activity of platinum-ruthenium (PtxRuy/C) catalysts of different compositions (x = 48–100%) for electrocatalytic nitrate reduction, chosen based on screening using a computational activity volcano plot. The PtxRuy/C alloys are more active than Pt/C, with Pt78Ru22/C six times more active than Pt/C at 0.1 V vs. RHE, and ammonia faradaic efficiencies of 93–98%. Density functional theory calculations predict maximum activity at 25 at% Ru, consistent with experiments. This maximum is due to a transition from nitrate dissociation as the rate determining step to a new rate-determining step at higher Ru content. This study demonstrates how electrocatalyst performance is tunable by changing the adsorption strength of reacting species through alloying.

Mechanism of Pd/C-catalyzed hydrogenation of furfural under hydrothermal conditions

Catalytic hydrogenation of furfural under hydrothermal conditions is of great importance and has recently attracted huge attention as an approach to obtaining a wide range of valuable chemicals from a renewable source. However, the data concerning the reaction mechanism of aqueous-phase furfural hydrogenation are very scarce, and it is still not clear which reactions lead to various carbonyl compounds, such as cyclopentanone, 4-oxopentanal, 5-hydroxy-2-pentanone. Herein, we present the results of an experimental study of the mechanism of reactions occurring in the furfural hydrogenation under hydrothermal conditions over the 1% Pd/CNTs catalyst. The following approaches have been used to study the reaction mechanism: hydrogenation of key intermediates formed upon the furfural conversion, and isotopic labeling experiments using D2O as a tracer in hydrogenation of furfural, which provides direct evidence of the occurring reactions. It was found that the furfural hydrogenation process is realized through four pathways including various reductive and acid-catalyzed furan ring opening reactions. The methods and approaches used in the present work, as well as the results obtained, can be useful in studying the mechanism of aqueous-phase hydrogenation of a wide range of oxygen-containing substrates in the presence of catalysts of different compositions.

Catalytic isomerization of d-glucose to d-fructose over BEA base zeotypes using different energy supply methods

The isomerization of d-glucose (Glu) to d-fructose (Fru) is a key step in the selective conversion of carbohydrate biomass to renewable products and has long been of great importance in the food and beverage industry. Expansion of the Fru market (food, non-food) poses various challenges to enhance productivity, where energy efficiency and use of cheap, robust synthetic catalysts may play important roles. Here, Glu isomerization, using water as the sole solvent, was studied using (i) micro/mesoporous catalysts of different compositions prepared from commercial zeolite Beta, and (ii) different energy supply methods, namely conventional conductive heating, microwave irradiation and ultrasound waves, at 75 °C. The type of energy supply method influenced the initial turnover frequency. Besides catalytic activity, the stability is important, which depended on the catalytic material properties (e.g., composition, textural properties), type of energy supply method and reaction temperature. Favourable results were verified for Glu isomerization using a hierarchical potassium/magnesium-containing Beta catalyst and ultrasound waves, at 75 °C.

(Invited) Hydrogen Overview and AWSM Project Updates

HydroGEN (https://www.h2awsm.org/) Energy Materials Network (EMN) a Fuel Cell Technologies Office (FCTO) consortium that aims to accelerate the discovery and development of advanced water splitting materials (AWSM) for sustainable, large-scale hydrogen production, and to more effectively enable the widespread commercialization of hydrogen and fuel cell technologies, in line with the H2@Scale initiative (https://www.energy.gov/eere/fuelcells/h2-scale), and meet the ultimate cost target for production set by the U.S. Department of Energy (DOE) at $2/kg H2. HydroGEN EMN is a six national laboratories consortium comprises National Renewable Energy Laboratory (NREL) - lead, Lawrence Berkeley National Laboratory (LBNL), Sandia National Laboratory (SNL), Lawrence Livermore National Laboratory (LLNL), Idaho National Laboratory (INL), and Savannah River National Laboratory (SRNL). With the rollouts of fuel cell electric vehicles (FCEVs) by major automotive manufacturers underway, enabling AWS technologies for the widespread production of affordable, sustainable hydrogen becomes increasingly important. The HydroGEN Consortium offers more than 80 materials capabilities nodes to help address RD&D challenges in efficiency, durability and cost. The capabilities span computational tools and modeling, materials synthesis, characterization, process manufacturing and scale-up, and analysis. Detailed descriptions of all the HydroGEN nodes are available in a searchable format on the HydrogGEN website (https://www.h2awsm.org/capabilities), including information such as the host National Lab, the capability experts, and a synopsis of the node’s unique aspects and capability bounds. By design, the nodes are cross-cutting, and any given node may be useful for one or several advanced water splitting (AWS) technologies. Leveraging the HydroGEN consortium’s staff of technical experts and broad collection of resource capabilities is expected to advance the maturity and technology readiness levels in all the AWS technologies, including low- and high-temperature electrolysis, photoelectrochecmical (PEC) and solar thermochemical (STCH) routes, which includes hybridized thermochemical and electrolysis approaches to water splitting. Currently, there are 20 HydroGEN seedling projects, and one project focused on benchmarking advanced water splitting technologies. These 21 new projects utilized over 40 unique capabilities across the six HydroGEN core labs. HydroGEN is indeed a national innovation ecosystem that comprises 11 national labs, 7 companies, and 30 universities. The experimental and computational data generated within HydroGEN are stored and shared within and across projects within the secured HydroGEN Data Hub (https://datahub.h2awsm.org/), which currently comprises 128 users and 3889 data files. The goal is to make the digital data generated within HydroGEN accessible, so the data can be shared and leveraged throughout the EMNs and in future programs. This presentation will provide an overview of the HydroGEN EMN consortium and highlight some low temperature water electrolysis projects. Proton Onsite met and exceeded near-term performance targets of 1.85V (achieved 1.8 V) at 2.0 A/cm2, using Proton-synthesized high activity IrRu oxide catalysts of different compositions. The Proton PEM water electrolysis cell also demonstrated 800 hours of durability at 2 A/cm2, operating at 80°C and 30 bar. This project utilized NREL’s ex-situ characterization node towards a better understanding of IrRu oxide catalysts stability. Proton’s improved cell efficiency is a step towards achieving its PEM water electrolysis cell efficiency goal of 43 kWh/kg (1.7 V at 90°C) and at a cost of $2/kg H2.Collaboratively, LANL, SNL, and NREL demonstrated promising alkaline exchange membrane water electrolysis performance, comparable to iridium oxide, using SNL Anion Exchange Membrane node, LANL-developed PGM-free oxygen evolution reaction perovskite catalyst, and NREL’s expertise in membrane electrode assembly fabrication (Multicomponent Ink Development, High-Throughput Fabrication, and Scaling Studies node) and cell electrolysis testing (In-Situ Testing Capabilities for Hydrogen Generation node).ANL, together with the LLNL Ab Initio Modeling of Electrochemical Interfaces and LBNL Density Functional Theory and Ab Initio Calculations nodes, investigated the factors that may alter the transport property of a cobalt-based oxygen evolution reaction catalyst, developed by ANL for proton exchange membrane electrolysis. The LLNL team found the origin of the discrepancy between the reported experimental and theory-derived electronic structure of cobalt oxide. This resulted in the confidence to choose a specific theory that can provide reliable information about the electronic structure of the cobalt oxide materials family. This is crucial to reliably identify the factors that determine the transport property of this material, which affects the overall catalytic activity. HydroGEN looks forward to growing its membership of industry, university and laboratory collaborators that can partner with member-laboratory experts by way of CRADAs and potential future FOAs. Moving forward, HydroGEN will expand its presence in the AWS community through working group meetings and participation at relevant professional meetings.

Essential Quality Attributes of Tangible Bio-Oils from Catalytic Pyrolysis of Lignocellulosic Biomass.

This review covers the characteristics of pyrolysis and catalytic pyrolysis bio-oils by focusing on the fundamental factors that determine bio-oil upgradability. The abundant works on the subject of bio-oil production from lignocellulosic biomass were studied to establish the essential attributes of the bio-oils for assessment of the oil stability and upgradability. Bio-oils from catalytic pyrolysis processes relating to catalysts of different compositions and structures are discussed. A general relationship between the higher heating value and the oxygen content in the catalytic pyrolysis oils exists, but this relationship does not apply to the thermal pyrolysis oil. Reporting bio-oil yield is meaningful only when the oxygen content of the oil is measured because the pyrolytic oil stability is mainly determined by the oxygen content. Isoenergy plot that associates bio-oil yield with oxygen content is presented and discussed.

Kinetic features of ethylene copolymerization with 1-hexene over titanium-magnesium Ziegler–Natta catalysts: Effect of comonomer on the number of active centers and the propagation rate constant

We present data on the number of active centers (CP) and the propagation rate constant (kP) upon copolymerization of ethylene and 1-hexene over supported titanium–magnesium catalysts of different compositions obtained by polymerization quenching with radioactive carbon monoxide (14CO). The rise in ethylene/1-hexene copolymerization rate as compared to the rate of homopolymerization (the comonomer effect) is found to be related to the increase in the calculated propagation rate constant. Meanwhile, the increased 1-hexene concentration results in a higher calculated kP value. Addition of 1-hexene during ethylene polymerization also increases the polymerization rate by raising the calculated kP value. These findings demonstrate that the comonomer effect is caused by the increase in monomer concentration in the copolymer layer that is formed on a catalyst particle and is characterized by reduced crystallinity as compared to that of homopolymer. The decline in the copolymerization rate with time is caused by reduction of the number of active centers.

The double peaks and symmetric path phenomena in the catalytic activity of Pd/Al2O3-TiO2 catalysts with different TiO2 contents

Physicochemical properties of Pd/Al2O3-TiO2 catalysts with different amounts of TiO2 contents were investigated by XRD, nitrogen adsorption-desorption, FTIR, NH3-TPD, H2-TPR and XPS techniques. Catalysts of different compositions were tested in the ethanol oxidation reaction to study the effects of TiO2 contents. Double peaks and symmetric path phenomena were observed at certain temperatures with the increase in TiO2 contents. The symmetric peak phenomena and the diverse activity fluctuations have been ascribed to the controlling factors such as temperature and compositions. With the increase in TiO2 content, the surface area, adsorbed oxygen contents and surface acid quantity decreased gradually. The large surface area and adsorbed oxygen contents were conducive to the performance, while increased acid amounts were not beneficial for ethanol oxidation. At 150 and 175 °C, Pd/AT(X11Pd/AT(X): Pd/Al2O3-TiO2(X = X wt% of TiO2).) (X < 50) catalysts performed better in ethanol oxidation because of the main factors of surface area and adsorbed oxygen. Owing to the stronger effects of acid quantity compared to other factors, Pd/AT(X) (X < 50) catalysts showed lower catalytic performance at 200 and 225 °C. The higher contents of low-temperature acid in the NH3-TPD results and the larger difference between Pd0 and Pd2+ in XPS analyses were the origins of the double peaks of higher activity for the Pd/AT20 and Pd/AT80 catalysts.

Degradation of diethyl sulfide vapors with manganese oxide catalysts supported on zeolite-13X: The influence of process parameters and mechanism in presence of ozone

Vapour phase catalytic degradation of diethyl sulfide (DES) (simulant of a potential chemical warfare agent: sulfur mustard) at higher concentration (∼1200ppm) is carried out in a fixed bed flow reactor over Mn/zeolite-13X catalysts of different manganese contents. The reaction is studied in the temperature range of 60–180°C using ozone as the oxidizing agent. The influence of various process parameters such as reaction temperature, metal content, gas hourly space velocities (GHSV), ozone-to-DES mole ratio and water vapor are studied for getting maximum activity of the catalysts. Results reveal that reaction temperature and water vapor has significant effect on the conversion of DES and stability of the catalyst. Higher ozone-to-DES mole ratio facilitates the complete mineralization of DES at mild reaction conditions. The major products identified in the gas phase degradation of DES are carbon oxides, ethylene, acetaldehyde, acetic acid, sulfur dioxide and diethyl sulfone. Traces of diethyl sulfoxide, ethanol, thioethanol, methane thiol, formic acid are also identified in GC-MS analyses. The plausible degradation pathway is proposed based on the products identified by analyses results. The Mn/zeolite-13X catalysts of different composition are prepared by wet impregnation method and characterized by different characterization techniques.

Effect of calcination/reduction temperature of Ni impregnated CeO2–ZrO2 catalysts on hydrogen yield and coke minimization in low temperature reforming of ethanol

CeO2–ZrO2 was proven to be a quite effective catalyst support for steam reforming of ethanol (SRE). In this study, properties of Ni impregnated mesoporous CeO2–ZrO2 catalysts of different compositions were optimized by changing the calcination/reduction temperature. Increase of calcination/reduction temperature from 400 °C to 650 °C caused significant decrease in surface area and redox ability of the catalysts, yielding higher coke formation and lower hydrogen yields. Results proved that, very high hydrogen selectivity values with negligible coke formation can be achieved at a SRE reaction temperature of 450 °C, over the Ni impregnated ceria zirconia mixed oxide catalyst, which was also calcined/reduced at 450 °C. Considering its high hydrogen selectivity values with negligible coke formation, the catalyst containing a CeO2/ZrO2 ratio of 6:1 was found as the best catalyst for low temperature SRE. Achievement of high hydrogen yields with negligible coke formation at SRE temperatures as low as 400 °C was quite promising from the point of view of hydrogen economy.

Investigation of defectiveness of multiwalled carbon nanotubes produced with Fe–Co catalysts of different composition

We have performed a study of CVD multiwalled carbon nanotubes (MWCNTs) produced with Fe–Co catalysts with a variable ratio of active metals. The Raman data were considered in combination with the temperature dependence of MWCNT conductivity. The data analysis is based on the point that the value of I2D/ID ratio correlates with the graphene fragment size. The fragments are considered as building blocks of MWCNTs. We showed that MWCNT defectiveness depends on the ratio of bimetallic active components in the Fe–Co catalyst. Thus, the ratio of I2D/ID increases and the D-mode intensity decreases while the Fe content in the catalyst increases. This also points to the reduction of defect number in the bigger graphene fragments. These results correlate with the data on conductivity temperature dependence. Namely, the increase of Fe content in the active component of the Fe–Co catalyst results in the increase of charge carrier concentration, which, in turn, indicates a decrease in MWCNT defectiveness.

Homopolymerization of ethylene and copolymerization of ethylene and 5-ethylidene-2-norbornene with the use of C2-symmetric ansa-zirconozenes catalysts of different composition

The homopolymerization of ethylene and the copolymerization of ethylene and 5-ethylidene-2norbornene were investigated in the presence of C2-symmetric ansa-zirconozenes complexes with various types of bridges and substituents in the indenyl ligand—rac-Et(Ind)2ZrCl2 (1), rac-Et(H4Ind)2ZrCl2 (2), rac-Me2Si(Ind)2ZrCl2 (3), rac-Me2C(Ind)2ZrCl2 (4), and rac-Me2C(tert-BuInd)2ZrCl2 (5)—and with methylalumoxane as an activator. Catalyst 5, which has the Me2C bridge and the tert-Bu substituent in the indenyl ligand of zirconocene, was the most active in the homopolymerization of ethylene. Catalyst 1, which has the Et bridge, was the most active in the copolymerization of ethylene and 5-ethylidene-2-norbornene with respect to the yield of copolymer products. The introduction of the tert-Bu substituent into the ligand of zirconocene (catalyst 5) greatly slowed the incorporation of the cyclic comonomer into the polymer chain. In terms of the product of the calculated copolymerization constants, the trend of comonomer alternation was greater in the case of catalyst 1 (r 1 r 2 = 0.042) than that in the case of catalyst 3 (r 1 r 2 = 0.061). The amorphous copolymers synthesized with catalyst 1 possessed the highest glass-transition temperature.

Kinetic features of ethylene polymerization over titanium-magnesium Ziegler-Natta catalysts: Effect of monomer concentration on the number of active centers and propagation rate constant

It was found that the observed order of the polymerization rate with respect to ethylene concentration at ethylene polymerization over two titanium-magnesium catalysts of different compositions is significantly higher than 1 (1.6–2.1). The data on the effect of ethylene concentration on the number of active centers (CP) and the propagation rate constant (kP) at ethylene polymerization over these catalysts were obtained by method of polymerization quenching with 14CO. An increase in ethylene concentration was found to increase the number of active centers. In some cases the increase of ethylene concentration proceeds to the narrowing of the molecular weight distribution of the resulting polyethylene and an increase in the calculated value of propagation rate constant. These effects were shown to be most pronounced at low ethylene pressure and increased concentration of an activator (AlEt3). Based on the experimental data, we proposed a scheme of reactions to explain the effects of ethylene and AlR3 concentrations on the number of active centers, the average values of propagation rate constant and molecular weight distribution of polymers produced over these multi-site catalysts.

Oxidative coupling of methane on flame-made Mn-Na2WO4/SiO2: Influence of catalyst composition and reaction conditions

Mn-Na2WO4/SiO2 catalysts of different composition were made in a single step by flame spray pyrolysis, a process that can be scaled up to a production rate in the range of kg/h. The multicomponent catalysts containing 0–5wt% Mn and 0–6wt% Na2WO4 were characterized by nitrogen adsorption, XRD, TEM, STEM, EDXS and TPR, and tested in the oxidative coupling of methane (OCM) in a continuous flow microreactor at different reaction conditions (temperature, CH4/O2 feed ratio, space time). As-prepared catalysts showed much higher specific surface area (SSA) and a more homogenous spatial distribution of the constituents than corresponding catalysts prepared by wet-impregnation. Upon exposure to reaction conditions at 810°C the amorphous SiO2 component gradually transformed to crystalline cristobalite, as shown by in situ XRD. However, the cristobalite formation, which was accompanied by a decrease of the SSA had only a marginal influence on catalyst performance. Conversion and selectivity to C2 compounds (ethene, ethane) increased with Mn content up to 1.9wt% and remained virtually constant up to 5wt%, affording a constant C2-yield of 17%. Increasing the Na2WO4 content was most effective up to 1wt%, while at contents higher than 3wt% the conversion declined. Only catalysts containing all metal constituents (Mn, W, Na, Si) afforded good catalytic behavior. Flame-derived catalysts with a composition 1.9%Mn-3%Na2WO4/SiO2 exhibited the highest C2-yield of 18.5% at a selectivity of 70%. Both, the flame-made catalyst and a corresponding wet-impregnated reference catalyst showed stable conversion, but different C2-selectivity behavior with time-on-stream, decreasing with the flame-derived catalyst and increasing with the wet-impregnated counterpart. The initial C2-selectivity as well as that after 6h on stream when a steady-state was achieved was higher for the flame-made catalyst and this at higher conversion, indicating the superior catalytic behavior of this catalyst. The better performance of the flame-derived catalyst is traced back to its more homogeneous spatial distribution of the constituents, which favors their beneficial mutual interaction.

A comparative study of ethylene and propylene polymerization over titanium–magnesium catalysts of different composition

ABSTRACTNew data on the molecular weight characteristics of polypropylene (PP) and polyethylene (PE) were obtained from the polymerization over supported titanium–magnesium catalysts differing in their compositions (presence and absence of internal and external donors). Internal and external donors were found to affect the molecular weight of polymers in a different manner for ethylene and propylene polymerization. The introduction of the internal donor increases the molecular weight of PP and does not affect the molecular weight of PE. The effect of external donor introduced to catalytic system on the polymer molecular weight depends on catalyst composition: for a catalyst without internal donor, the introduction of the external donor increases the molecular weight of PP and does not affect that of PE. In the case of catalyst with the internal donor, the introduction of the external donor increases the molecular weight of PP and substantially decreases that of PE. The data on polymerization degree of the polymers produced under conditions when chain transfer with hydrogen was the dominant reaction were used to calculate the values for ethylene polymerization over the catalysts of different composition. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40658.

Preparation and Characterization of High-Performance Perfluorosulfonic Acid/SiO2 Nanofibers with Catalytic Property via Electrospinning

Polymer nanofiber-supported perfluorosulfonic acid (PFSA)/SiO2 catalysts are successfully fabricated by electrospinning method from polymer/nanoparticle suspensions. This kind of catalyst has a large number of active acid sites and high specific surface area up to 85.6 m2/g. Scanning electron microscope images reveal that the catalysts present high porosity and inner-connected porous structure which varies much with SiO2 loading. Nitrogen adsorption–desorption measurements demonstrate a wide distribution of pore sizes inside the composites. Catalysts of different compositions are evaluated in esterification in a batch reactor under various conditions, and the results indicate that those of 20 wt % PFSA loading have the best activity of unit PFSA. Supporting PFSA by a nanofibrous matrix enhances liquid holdups inside the catalysts and offers accessibility of the acid sites, and therefore improves the activity of the catalysts. Moreover, these catalysts allow recovery at high percentages and regeneration with high activity.

Study of the compositional heterogeneity of ethylene/1–hexene copolymers produced over supported catalysts of different composition

AbstractSeparation into narrow MWD fractions (liquid–liquid fractionation) and preparative TREF (temperature rising elution fractionation) with subsequent analysis of fractions by GPC, FTIR, and 13C NMR spectroscopy were used to study the comonomer distribution of ethylene/1–hexene copolymers produced over highly active supported titanium‐ and vanadium‐magnesium catalysts (TMC and VMC) and a supported zirconocene catalyst. These catalysts produce PE with different MWD: Mw/Mn values vary from 2.9 for zirconocene catalyst, 4.0 for TMC, and 15 for VMC. 1‐Hexene increases polydispersity to 25 for copolymer produced over VMC and hardly affects MWD of the copolymer produced over TMC and zirconocene catalysts. The most broad short chain branching distribution (SCBD) was found for ethylene/1–hexene copolymers produced over TMC. VMC and supported zirconocene catalyst produce copolymers with uniform profile of SCB content vs. molecular weight in spite of great differences in Mw/Mn values (22 and 2.5 respectively). TREF data showed that majority of copolymer produced over supported zirconocene catalyst was eluted at 70–90°C (about 85 wt %). In the case of VMC copolymer's fractions were eluted in the broad temperature interval (40–100°C). Accordingly, TREF data indicate a more homogeneous SCBD in copolymer, produced over supported zirconocene catalyst. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

Electronic and atomic structure of platinum-cobalt nanocatalysts

X-ray diffraction in combination with X-ray emission and EXAFS spectroscopy were used to study the electronic and atomic structure of metal nanoparticles stabilized on a carbon support in novel PtxCo/C catalysts of different composition with the molar ratio Pt:Co (x) of 1 to 3. Cobalt atoms in nanoparticles, which average size was 2–4 nm, were shown to form chemical bonds both with platinum atoms and carbon atoms of the support material.

Production of hydrogen and carbon nanofibers through the decomposition of methane over activated carbon supported Ni catalysts

Hydrogen has been produced by decomposing methane thermocatalytically at 1123 K and volume hourly space velocity (VHSV) of 1.62 L/h g in the presence of activated carbon supported Ni catalysts of different compositions (Samples coded as Ni10, Ni20, Ni30 and Ni40 respectively). The studies indicated that the sample coded Ni30 catalyst (with Ni content of 23.33 wt.%) has the highest catalytic activity among all the catalysts tested. The initial methane decomposition rate, accumulated carbon in 4 h and sustainability factor (SF) of Ni30 catalyst are 0.89 mmol/min.g, 7.92 g C/g Ni and 0.7 respectively. SEM image of Ni30 catalyst after methane decomposition reaction showed formation of degenerated carbon fibers. XRD of the above catalyst revealed, moderately crystalline peaks of Ni which may be responsible for the increase in the catalytic life and the formation of carbon fibers.