Active Component Of Catalyst Research Articles

Characteristics of Vanadium-Based Coal Gasification Slag and the NH3-Selective Catalytic Reduction of NO

In order to realize the resource utilization of coal gasification slag (CGS) and to effectively control the emission of nitrogen oxides (NOx) in coke oven gas, the effect of the reaction conditions and vanadium loading over the CGS catalysts was carried out for the selective catalytic reduction (SCR) of NO by NH3. The various vanadium loaded CGS catalysts were prepared using impregnation methods. The addition of 1% vanadium to the CGS catalyst (V1/CGS) significantly enhanced the NO conversion at a wide temperature range of 180–290 °C. The catalysts were characterized by N2 adsorption/desorption, X-ray photoelectron spectroscopy, H2-temperature programmed reduction, NH3-temperature programmed desorption, Inductively coupled plasma optical emission spectrometer (ICP-OES), thermo gravimetric analyses (TGA), Fourier Transform infrared spectroscopy (FTIR), Scanning electron microscope-Energy dispersive spectrometer (SEM-EDS), and X-ray powder diffraction (XRD). The experimental results show the following: That (1) the NO removal efficiency of the sample CGS3 was the best, and it could be up to 100% under the experimental conditions; (2) The NO removal efficiency of the catalysts was higher in the atmosphere with SO2 than that without SO2; (3) The XRD results indicated the active component of vanadium was homogeneously dispersed over CGS and the active component of catalyst was V2O5 according to the XPS results. In particular, the NH3-TPD spectra of the vanadium loaded CGS catalyst showed that vanadium produced more acid sites, and the Lewis acid sites on the vanadium species were the active sites for the catalytic reduction of NO at 240–290 °C.

Physical mixture of MCM-41/ZSM-5 as an active catalyst component for maximization of propylene in Catalytic cracking of VGO

ABSTRACTThe performance of a novel catalyst additive containing highly porous MCM-41 and ZSM-5 zeolite was investigated using a commercial equilibrium FCC catalyst in catalytic cracking of vacuum gas oil. The catalytic tests were assessed in a fixed-bed microactivity test unit at reaction temperatures 500–620 °C. The highest propylene yield of 23.8 wt% was achieved at 600 °C. The propylene yield increased from 14.49 wt% to 23.8 wt% when the temperature rose from 500 to 600 °C; however the gasoline yield fell from 22.47wt% to 16.49 wt% by increasing the temperature from 580 °C to 620 °C, respectively.

In-situ synthesis of Ag-Pi oxygen-evolving catalyst in phosphate environment for water splitting

An efficient Ag-Pi oxygen-evolving catalyst was fabricated in situ in a phosphate electrolyte solution (pH 12.4). The catalyst approaches an amorphous structure, unlike the reported Ag-based oxygen-evolving catalysts. The catalytic activity for water oxidation of the Ag-Pi catalyst is 11.1 μmol h−1 cm−2 and it has a modest oxygen-evolution overpotential of 457.0 mV at 1 mA cm−2 in 0.1 M K3PO4 electrolyte. The effects of different electrolytes on the formation of the Ag-Pi catalyst were investigated. The active component of the Ag-Pi oxygen-evolving catalyst as a water-splitting catalyst is the AgO phase as determined by X-ray diffractometry and X-ray photoelectron spectroscopy analysis. A Ag-Pi mechanism that includes the Ag(I) and Ag(III) cycles is proposed to explain the electrocatalytic oxygen evolution.

Highly Effective Catalysts Supported on Metal Foams for Reforming Hydrocarbons for SOFCs

The development of highly efficient modular power generation units is of great importance. Solid oxide fuel cells (SOFC) are currently considered as the most efficient devices for the conversion of hydrocarbons, (natural gas, LPG, JP or diesel) into electric power. To provide stable SOFC operation, initial fuel, before feeding to the SOFC anode, should be converted to synthesis gas with high hydrogen content. Catalytic steam, combined steam-dry, partial oxidation or autothermal reforming are the most appropriate reactions for this purpose. The optimum temperature for these reactions is 550 − 900 °C, which falls within the SOFC working temperature range. The development of a catalyst system that can act as a combined catalytic reformer and heat exchanger (to remove or supply heat at the reaction zone) is very promising for efficient power generation. The combined catalytic reformer and heat exchange catalyst should have the following characteristics: high intrinsic activity with respect to its weight and volume (due to size limitations of the reformer); coking resistance; high intrinsic heat conductivity (in order to provide uniform temperature and reaction rate distribution across the reformer); low pressure drop. The present report summarizes the results obtained during a systematic study of several new nickel- and rhodium- based catalyst compositions supported on metal foams, their performance, and fundamental principles of the above mentioned reactions for conversion of various common hydrocarbon fuels. A procedure for deposition of active catalyst components onto metal foams has been developed. It was systematically verified on Ni, Ni-Fe, FeCrAlY-steel foams with porosity from 10 to 70 pores per inch (ppi), obtained from various manufacturers. The catalytic performance of the coated metal foam substrates was studied in a fixed-bed continuous flow reactor. Total feed flow rate (GHSV − gas hourly space velocity) ranged from 3,000 to 30,000 hr-1. The reaction temperature varied from 500 to 800 °C. The catalysts (as-synthesized and used) were characterized by BET, XRD, XPS, TEM, EDX, SEM, TPR and TPD techniques.

KINETICS OF OXIDATIVE CHLORINATION OF METHANE

Heterogeneous oxidative chlorination of methane was investigated. The target product is methyl chloride. The investigated terms and conditions of oxychlorination of methane: process temperature 400°C, pressure 0.1-0.9 MPa, catalyst (% weight.): copper chloride (II) 1-8%; potassium chloride 2.5%; lanthanum chloride 1%; carrier - aluminosilicate. Powder X-ray diffractometry and electron microscopy showed that the active catalyst components (CuCl2, KCl, LaCl3) are unevenly distributed on the support surface (α-Al2O3·SiO2) and form agglomerates with a high salt content, including binary chlorides such as KCuCl3, K2CuCl3 or K2CuCl4, hydrates K2CuCl4·2H2O and CuCl2·2H2O and hydroxychlorides Cu3Cl4(OH)2 and Cu2Cl(OH)3. The kinetics of methane oxychlorination was studied in a gradientless reactor at 400°C and pressure 0.1 - 0.9 MPa by varying the partial pressures of the reactants. Analysis of the products was carried out by GC. An equation of the reaction rate including partial pressures of methane, hydrogen chloride and water to the 0.77, 0.01 and 0.64 power, respectively, but of zero order by oxygen and chlorine provides an adequate description of methyl chloride formation rate. Significant influence of water partial pressure is proved for the reaction under consideration.

(Invited) Alkaline Fuel Cells (AFCs) and Alkaline Membrane Fuel Cells ( AMFCs)

I was fortunate to have many technical discussions with Russ Kunz over the years and learnt a lot from him. Russ was a rarely encountered combination of scientist and technologist , a combination which is prerequisite for being a leader, as he was, in the field of fuel cell development. I chose the subject of this talk having been a common theme in our technical discussions, as Russ was the house expert at UTC for the alkaline fuel cells (AFCs) used in space applications, whereas I got intrigued in recent years by the potential of alkaline membrane fuel cells ( AMFCs) which share key features with the AFC while aiming to operate with no liquid electrolyte. The talk will accordingly review first some interesrting key features of materials and processes in AFCs about which I learnt to large degree from discussions with Russ. The first subject is the ORR in highly alkaline electrolytes and why gold is actually the active catalyst component in AFCs , being used as a AuPt alloy with the Pt serving basically just to harden the metal catalyst particles. The high activity of gold as ORR catalyst in alkaline media, does not fit the extensively taught volcano shaped relationship between M-O bond strength and ORR rate at a metal M. Gold is way down on the descending branch of the volcano plot in acid electrolyte, but is more active than Pt in alkaline media. This has been explained by the stabilization of a peroxide anion intermediate formed in alkaline electrolytes (HO2- or O2=) on the electrolyte side of the metal electrolyte interface, thereby removing the need of significant M-O interaction to stabilize the HOOads intermediate formed in acid. This opens the door for metals of very low affinity to oxygen to become very active ORR electrocatalysts thanks to the low overpotential they require to generate oxide free metal sites. In the case of the AMFCs, this high activty of coinage metals in alkaline environment is the basis for the possible choice of silver as ORR electrocatalyst, having activity in alkaline electrolyte comparable to Pt, at a market price which is about 1% that of Pt. One central aspect which is quite different in AFCs and AMFCs, is water managment. The AMFC presents a significant challenge of combined tendencies for cathode dry-out and anode flooding, originating form the cell water product forming in the anode ( fuel side) and consumed by the electrode process in the cathode ( air side). The resulting demands of water diffusivity through the cell membrane as well as electrode structures required to achieve passive control of the water profile in the AMFCs , staisfying the ORR consumption and ionomer hydration demands, will be described. Finally, the HOR in alkaline media in general and in the AMFC in particular has received significant attention recently. The rate of the HOR at Pt in 0.1-1MKOH solutions is significantly lower vs. the rate in acid. However, AMFC polarization curves to be presented show a performance that is not much below that of PEMFC in operation on hydrogen and air. This is achieved with HOR catalyzed by very low loadings of Pt in the form of alloy ( or other combination ) with an oxophilic metal component which facilitates completion of the HOR process and, securing optimized cell hydration under current.

Carbon-containing catalysts for the hydroprocessing of oil fractions: A review

Over the last 20 years, carbon-containing catalysts prepared using carbonized aluminum oxide and various carbon-based materials as carriers, along with metal carbides as active components, have been widely studied in the hydroprocessing of oil fractions. In this work, the properties of different groups of carbon-containing catalysts are discussed. The difficulties of using carbon-based carriers caused by their need for chemical pretreatment (oxidation and leaching), and the application of water–organic infiltrating solutions to form active catalyst components in finely dispersed form, is shown.

Adsorption properties of palladium particles supported on aluminum oxides with varied acidity in hydrogenation of butadiene-1,3

Influence exerted by acid-base modifiers of aluminum hydroxide on the texture and acid characteristics of the aluminum oxide support was studied. The effect of the modified aluminum oxides on the charge state of the active component of aluminum-palladium catalysts was determined. It was found that catalysts based on a support with high concentration of strong acid centers are characterized by low conversion of butadiene-1,3 due to the firm chemisorption of the diene on electron-deficient palladium particles. Their formation is due to the strong metal-support interaction. By contrast, catalysts synthesized with supports having a small number of acid centers provide a high conversion of butadiene-1,3.

OBTAINING ACTIVE COMPONENTS (Tа, Rа) of BIMETALLIC CATALYSTS ON γ-Al2O3 AND TiO2 MATRICES

Tantalum methylate of general formula Ta2(OMe)10 was synthesized by electrochemical synthesis as a precursor for obtaining oxomethylate complexes of tantalum and rhenium. The complex is used to prepare catalysts in reactions of cross-condensation and reductive dehydration of alcohols. The catalysts are based on γ-Al2O3 and TiO2. Ultradisperse and nanosized TiO2 is obtained by the supercritical fluid technology. The sample is characterized by different methods (DTA, XRD, DSC). It is shown that annealing at 340°C allows obtaining anatase modification of TiO2 with a specific urface of 27.3 sq.m/g which can serve as a matrix for drawing active components of catalysts. It is shown that the Ta-Re/Al2O3 catalyst allows transforming ethanol and mixtures of ethanol with glycerin into aliphatic hydrocarbons C3-C11. A technological scheme for obtaining active components of the catalysts for cross-condensation and reductive dehydration of alcohols is suggested.

SELECTIVE GAS PHASE OXIDATION OF MONOCHLOROTOLUENES OVER MODIFIED OXOVANADIUM SYSTEMS SUPPORTED ON Al2O3 AND SiO2

V-Mo-O/SiO 2 materials were prepared by the impregnation techniques and characterized by Scanning Electron Microscopy (SEM), FT-IR, Thermal analysis, N 2 adsorption/desorption and X-ray powder diffraction (XRD) to determine the phase structure and loadings of vanadium species. This material was tested for solvent-free catalytic oxidation of monochlorotoluene under chosen conditions. The result shows that V-Mo-O/SiO 2 is effective catalysts, exhibiting conversion of monochlorotoluene and selectivity monochloromaleic anhydride 75–85%, 24–32% respectively. Furthermore, the catalyst can be easily recovered and reused for 20-25 hours without a significant loss in its activity and selectivity. The oxidation rate and direction determined by the temperature (315-450 0 C), proportions between the reagents (1:1–1:15 mol/l), bond dissociation energies, the effects of active components of catalyst and contact time.

Improving catalytic activity and stability by in-situ regeneration of Ni-based catalyst for hydrogen production from ethanol steam reforming via controlling of active species dispersion

Nickel is an active component of catalyst for hydrogen production from ethanol steam reforming (ESR). However, Ni based catalyst usually meets severe deactivation due to coking. Normally, Ni catalyst regeneration could be achieved by heating coked catalyst in the oxygen contained atmosphere gas to remove coked carbon by oxidation of carbon. During this regeneration process, dispersed Ni particles are easily segregated because burning of carbon generates huge amount of heat and leads to uncontrollable temperature increase. In this paper, a new regeneration method of Ni catalyst was developed by re-deposition of another portion of Ni on deactivated Ni/SiO2 catalyst (denoted as catalyst 2) instead of O2 combustion of the deactivated catalyst (denoted as catalyst 1). H2-TPR results indicated that the metal-support interaction of catalyst 2 was stronger than that of catalyst 1, leading to higher metal dispersion and smaller Ni particles size over catalyst 2. The H2 chemisorption and HRTEM results indicated the dispersion of catalyst 2 reached 19.3%, much higher than 9.4% of catalyst 1. The dimension of late-loaded Ni particle was around 9.5 nm, even smaller than that of catalyst 1 (17.5 nm), corresponding to the high catalytic activity and stability of catalyst 2. The ethanol conversion of catalyst 1 and catalyst 2 were 76.5% and 94.6% at 500 °C, respectively. After short term of 20 h test, the ethanol conversion of catalyst 2 still remained, while that of the catalyst 1 decreased to about 40% of initial activity under same reaction condition (T = 550 °C, S/C = 7.5, LHSV = 4.1 h−1 and P = 1 atm.).

Effect of polyamide on selectivity of its supported Raney Ni catalyst

A newly-developed polyamide supported Raney Ni catalyst, which is suitable for use in fix-bed reactions with high selectivity, was studied in this paper. Selective hydrogenation of acetone to isopropanol was chosen as a probe reaction. It has been found that clean preparation of isopropanol could be achieved, that is to say, the two main byproducts (isopropyl ether and methyl- iso-butyl carbinol) could be eliminated with the newly-developed polyamide supported Raney Ni catalyst. The elimination of these side reactions was attributed to the adsorption effect of polyamide support and a model was proposed. The proposed model was further proved by hydroamination reaction of acetone. According to this model, catalyst support can play an important role in chemical reactions. Different products could be produced when different catalyst support is used, the main reaction and side reactions can even be reversed sometimes when the chemicals, active component of catalyst and reaction condition are the same. This model could help to improve catalytic selectivity of many Raney metal catalysts used routinely in chemical and oil refining industry, and is also useful for hydrogenation reactions in pharmaceutical and food industry.

Methanation of Carbon Supports of Ruthenium Catalysts for Ammonia Synthesis. Review

Methanation of carbon supports in a hydrogen-containing medium results in degradation of the support and sintering of the active component of ruthenium catalysts for ammonia synthesis. In the review, key publications on approaches to inhibiting methanation are analyzed. It is demonstrated that the solution algorithm is, in general, determined. This is graphitization of the carbon supports at high temperatures (up to 2000 °C) and addition of promoter such as alkali (Cs, K) and alkali-earth (Ba) oxides to modify the ruthenium electron state and to prevent the carbon surface from interaction with active hydrogen. The most effective catalyst that does not suffer from methanation at temperature up to 700 °C and hydrogen pressure of 100 atm is identified. The analysis can be useful to choose and prepare Me/C catalysts, where Me is a 8 group metal.

NiFe2O4 as an active component of a platinum group metal-free automotive three-way catalyst

To develop a platinum group metal (PGM)-free automotive three-way catalyst (TWC), we investigated the structure–activity relationship for Fe–Ni oxide catalysts and found NiFe2O4 with a spinel structure is an active component of the three-way catalytic reaction (NO–C3H6–CO–O2).

Studies of the Stability of Catalysts for Oxidative Chlorination of Methane

The studies were focused on the influence of various factors on the stability of catalysts for oxidative chlorination of methane due to evolution of the active catalyst components (copper chlorides). The volatility of copper chlorides was shown to depend mainly on the catalyst composition and temperature. When the average temperature in the reactor was 350 °C, 0,45 % and 0,72 % of copper chlorides escaped, respectively, the catalyst containing copper and nickel oxides and the catalyst containing lanthanum chloride as the activating impurity after 5 hours. Another way to improve the catalyst stability, apart from diminishing the copper chloride volatility, is to feed hydrogen chloride bearing copper chloride solutes isolated from the outlet reaction gas in order to abstract the reaction heat and to feed back the unreacted hydrogen chloride.

Bimetallic Pd—Pt/γ-Al2O3 catalysts for complete methane oxidation: the effect of the Pt: Pd ratio

Alumina-supported bimetallic Pt—Pd catalysts proved to be more active in the complete oxidation of methane than monometallic systems (Pt/Al2O3, Pd/Al2O3). The maximum activity of the bimetallic catalysts was achieved at ~40 at.% Pt in Pd on the catalyst surface. After the oxidation reaction, redistribution of platinum and palladium was observed in the active component of the catalysts with the degree of redistribution depending on the initial Pt: Pd ratio.

Core-shell bifunctional catalyst for steam methane reforming resistant to H2S: Activity and structure evolution

Results of studies on the activity of the Ni-containing catalyst in the steam reforming of methane (SRM) process are presented. It is established that the catalyst shows high activity in SRM, stability to coke formation and resistance to H2S presence in the reaction gas mixture. The catalyst was prepared on the basis of mixed oxides separated from layered vermiculite. The structure and the phase composition of catalytically active components were investigated by XAFS, XRD, EDX, TEM and Moessbauer spectroscopy. It is found that the active components of catalyst are represented by clusters with core-shell configuration where FeNi alloy is a core (∼10 nm) surrounded by superparamagnetic γ-Fe2O3 shell (1–4 nm). These clusters are distributed in the mixed spinel Mg(Fe,Al)2O4 matrix. It is suggested that clusters of FeNi alloy are active in SRM while superparamagnetic γ-Fe2O3 particles are active in the oxidative decomposition of H2S.

Microwave assisted heterogeneous vapor-phase oxidation of 3-picoline to nicotinic acid over vanadium–titanium oxide catalytic system

Binary vanadium–titanium oxide catalysts as well as pure V2O5 and TiO2 (anatase) were studied in microwave assisted vapor-phase oxidation of 3-picoline by oxygen in the presence of nitrogen and water vapors. The main product of the reaction over all catalysts was nicotinic acid. 3-pyridinecarbaldehyde, 3-cyanopyridine, and CO2 were obtained at smaller amounts. The highest rate of the reaction calculated per square meter of the catalyst surface was observed over pure vanadium oxide. Decrease in vanadium oxide content in the binary catalysts led to decrease in the rate of 3-picoline conversion. Titanium dioxide (anatase) demonstrated the lowest activity. Much more energy was necessary to heat pure titanium oxide to the reaction temperature when compared to the pure vanadium oxide. The microwave heating effect can be located on the V2O5 catalyst active component. Due to specific temperature distribution, the lattice oxygen in the microwave effective dielectric vanadium oxide becomes more mobile inducing the rate of 3-picoline oxidation to nicotinic acid. The data obtained under microwave heating were compared to the results produced over the same catalysts by applying classical conventional energy.

Study on Noble Metal Catalyst for Selective Catalytic Reduction of NOx at Low Temperature

The method of selective catalytic reduction (SCR) to removal NOx is very mature. However, its initial investment and operation cost are still high, which limits the development of SCR technology. Low temperature SCR catalysts can significantly reduce the cost. Catalyst active component and its carrier is the key to the efficiency of denitration. This paper summarizes the research progress of noble metal catalyst of low temperature SCR.

XAFS structural study of specific features of the active component of model palladium catalysts

Model low-percentage metal oxide palladium catalysts are prepared from acetate complexes of Pd and Mn to study the nature of the activity and the genesis of nanostructured membrane catalyst Pd-Mn systems. A comprehensive study of the prepared model precursor compounds; specific features of their metal components in gels and oxides; and the genesis of the active component, local structure, and charge state is performed by EXAFS and XANES. Possible versions of structural models for the stabilization of metals on oxide supports aare discussed.