Specific Surface Area Of Catalyst Research Articles

Nickel Metal with Various Morphologies: Synthesis and Performances for Catalytic Carbon Dioxide Reforming with Methane

In this research, nickel metal of three different morphologies including nanostar, icosahedra, and microsphere structures were synthesized. It was found nanostar nickel revealed the Ni(111) crystallographic plane with particle size in the range of 150-200 nm and BET surface area of 13 m2/g. The icosahedra nickel also showed the Ni(111) crystallographic plane with larger particle size (300-400 nm) and BET surface area of 20 m2/g, whereas microsphere nickel exhibited the relatively large cluster size (approximately 3 microm) and BET surface area (114 m2/g) as a result of an aggregation of Ni(101) nanoplates. The obtained nickel catalysts were tested for the activity in carbon dioxide reforming with methane. Based on the similar specific surface area of catalysts, nanostar nickel showed the highest carbon dioxide and methane conversions due to its crystallographic structure. At 700 degrees C, nanostar nickel catalyst exhibited the highest carbon dioxide and methane conversions of 17.6 and 10.5 times higher than those of microsphere nickel catalyst, respectively.

Catalytic CO<sub>2</sub> Reforming of Methane over Perovskite Noble Metals

A series of perovskite-type oxides catalyst LaAl1-xNixO3 (0≤x≤1) and modified by substitute noble metal La0.4Al0.2Ni0.8M0.6O3 (M=Pt, Pd, Ru, Rh, Ir) prepared by the sol-gel method shows high activity, stability, good resistance to carbon deposition and sintering of the catalyst for the reforming of methane reaction. The reaction was studied under continuous flow using a mixture of CH4:CO2=1:1. Catalysts were characterized by using BET, XRD, SEM, EDS, and HR-TEM. The specific surface area of catalysts varied greatly from 3.07 to 10.18 m2/g with the different substitution (x) following calcination at 850°C. XRD analysis of the solids shows LaNiO3 and/or LaAlO3 as the main phases present on the solids depending on the degree of substitution and more intense peaks and cell parameters showed formation of Ni-Al solid solutions. SEM coupled to an energy dispersive X-ray spectrometer (EDS) shows the possibility to obtain a solid solution of LaAl1-xNixO3 (0≤x≤1) with propionic acid as solvent. The obtained results revealed that the Rh and Ru catalysts showed the highest activity and also showed a high catalytic stability without any decrease in methane conversion up to 3000min of reaction.

Electrochemical Studies of Novel Pt/Ceria/C Oxygen Reduction Catalysts for Fuel Cells

Novel Pt/ceria/carbon catalysts with sub-2 nm ceria crystallites embedded in carbon matrixes, recently developed at Los Alamos National Laboratory, were studied in aqueous acidic media using rotating ring disk electrode (RRDE) and voltammetric techniques. The ceria nanophase was either pure or doped with trivalent gadolinium or praseodymium. The catalysts with lower Pt contents (3.8-5%) had higher specific surface areas and performed better than those with higher Pt contents (≥8.5%). The doping with either Pr or Gd was found to improve the catalyst specific surface area, whereas Pr doped catalysts exhibited higher specific activities in oxygen reduction reaction (ORR) than non doped and Gd doped catalysts. The former are also more selective for four-electron ORR. The presence of ceria in the catalyst support was found to increase the catalyst tolerance to CO poisoning.

Study on Cu-Based Catalysts for Synthesis of Indole

A series of Cu-based catalysts for the synthesis of indole by the reaction of aniline and ethylene glycol were prepared and characterized by ICP-AES and XRD. The results indicated that the activity and stability of Cu/SiO2 catalyst was increased after adding Zn, Mn, Cr and Fe promoters. Mn promoter was favorable for the dispersion of Cu, Zn, Cr, Fe and enlarged the specific surface area of catalysts. It could be seen that the catalysts prepared by impregnation method had better stability and higher activity than the catalysts prepared by co-precipitation method. The catalysts with small grain size of Cu had higher activity than those with big grain size. Some catalysts showed excellent performances in this reaction.

CATALYTIC HYDROCRACKING OF WASTE LUBRICANT OIL INTO LIQUID FUEL FRACTION USING ZnO, Nb<sub>2</sub>O<sub>5</sub>, ACTIVATED NATURAL ZEOLITE AND THEIR MODIFICATION

Catalytic hydrocracking of waste lubricant oil into liquid fuel fraction using ZnO, Nb2O5, activated natural zeolite (ZAAH) and their modification has been investigated. The zeolite was produced in Wonosari, Yogyakarta. Activation of the zeolite was carried out by refluxing with HCl 3M for 30 min, produced the activated natural zeolite (ZAAH). The ZnO/ZAAH catalyst was prepared by impregnation of Zn onto the ZAAH by ion exchange method using salt precursor of Zn(NO3)2.4H2O. The Nb2O5/ZAAH catalyst was prepared by mixing the ZAAH sample with Nb2O5 and oxalic acid solution until the paste was formed. The impregnation of Zn onto Nb2O5/ZAAH was carried out using the same method to that of the ZnO/ZAAH catalyst resulted ZnO/Nb2O5-ZAAH catalyst. Characterization of catalyst includes determination of Zn metal by Atomic Absorption Spectroscopy (AAS), acidity by gravimetric method and catalyst porosity by Surface Area Analyzer (NOVA-1000). Catalytic hydrocracking was carried out in a semi-batch reactor system using ZnO, ZAAH, ZnO/ZAAH and ZnO/Nb2O5-ZAAH catalysts at 450 oC under the H2 flow rate of 15 mL/min. and the ratio of catalyst/feed = 1/5. The composition of liquid products was analyzed by Gas Chromatograpy (GC).The results showed that impregnation of ZnO and/or Nb2O5 on the ZAAH increased the acidity and specific surface area of catalyst. The products of the hydrocracking process were liquid, coke and gas. Conversion of liquid products was increased by the increase of catalyst acidity. The highest liquid product was produced by ZnO/Nb2O5-ZAAH catalyst, 52.97 wt-%, consist of gasoline, 38.87 wt-% and diesel, 14.10 wt-%. Keywords: hydrocracking, waste lubricant oil, liquid fuel fraction

Preparation of KF/CaO nanocatalyst and its application in biodiesel production from Chinese tallow seed oil

KF/CaO nanocatalyst was prepared by using impregnation method and used to convert Chinese tallow seed oil to biodiesel. The effects of different preparation conditions on biodiesel yield were investigated and the structure of the catalyst was characterized. Transmission electron microscopy (TEM) photograph showed that the catalyst had porous structure with the particle size of 30–100 nm. Brunauer–Emmet–Teller (BET) analysis indicated that the catalyst specific surface area was 109 m 2 g −1 and average pore size was 97 nm. X-ray diffractometer (XRD) analysis demonstrated that the new crystal KCaF 3 was formed in catalyst, which enhanced catalytic ability. Under the optimal conditions, the biodiesel yield was 96.8% in the presence of as-prepared KF/CaO catalyst, showing potential applications of catalyst in biodiesel industry.

Reduction Behaviors of Nitric Oxides on Copper-decorated Mesoporous Molecular Sieves

‡§ In this study, NO reduction behaviors of copper-loaded mesoporous molecular sieves (Cu/MCM-41) have been investigated. The Cu loading on MCM-41 surfaces was accomplished by a chemical reduction method with different Cu contents (5, 10, 20, and 40%). N2/77 K adsorption isotherm characteristics, including the specific surface area and pore volume, were studied by BET’s equation. NO reduction behaviors were confirmed by a gas chromatography. From the experimental results, the Cu loading amount on MCM-41 led to the increase of NO reduction efficiency in spite of decreasing the specific surface area of catalysts. This result indicates that highly ordered porous structure in the MCM-41 and the presence of active metal particles lead the synergistical NO reduction reactions due to the increase in adsorption energy of MCM-41 surfaces by the Cu particles.

Physico-Chemical Properties of Cobalt–Ruthenium (10% Co–0.5% Ru) Catalysts Supported on Binary Oxides 8.5%ZrO2/Support (SiO2, Al2O3, TiO2) for Fischer-Tropsch Synthesis

The promotion of Fischer-Tropsch catalysts 10%Co/Al2O3, 10%Co/SiO2, 10%Co/TiO2 by 0.5% Ru and the modification of supports by 8.5 wt% ZrO2 have been studied. The following properties: catalyst specific surface area as well as reducibility and dispersion of metallic phase were studied by different techniques: BET, TPR, and H2 chemisorption. The modification of supports by non-reducible ZrO2, results in a decrease of cobalt oxide reduction on Al2O3 and TiO2 but not on SiO2 supports. Additionally the enhancement of cobalt dispersion was found for all catalysts with ZrO2 modified supports. The impact of Ru promotion is likely due to the stabilization of applied supports, prevention or blockage of interaction between surface Co species and support and an increase in cobalt oxide reducibility to the catalytically active metallic cobalt phase.

Influence of Alkaline Earth Metals on Cobalt-Cerium Composite Oxide Catalysts for N<sub>2</sub>O Decomposition

Catalysts of cobalt-cerium composite oxide doped with series of alkaline earth metals were prepared using the citrate method. Results of catalytic activity tests showed that the addition of alkaline earth metals enhanced the efficiency of N2O decomposition according to the following order: Mg <Ca <Sr,Ba. Characterization of these catalysts was done using X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET) surface area measurement, X-ray photoelectron spectroscopy (XPS), oxygen temperature-programmed desorption (O-2-TPD) and hydrogen temperature-programmed reduction (H2-TPR). Results indicated that the addition of alkaline earth metals did not change the crystal structures and specific surface areas of catalysts, but did enhance the electron donation ability of the active site (Co2+). The surface reaction of N2O with Co2+ involved electron donation from Co2+ to the anti-bonding orbital of N2O that resulted in the release of N-2. The desorption of residual oxygen leads to the regeneration of the active site (Co2+) through the donation of electrons back to Co2+. We conclude that the addition of alkaline earth metals promotes surface reactions of N2O with Co2+ by facilitating electron donation from the active site. This process is the rate-determining step for pure cobalt-cerium composite oxide catalysts and the catalytic activity for the decomposition of N2O is thus improved.

Advanced computational tools for PEM fuel cell design: Part 2. Detailed experimental validation and parametric study

This paper reports on the systematic experimental validation of a comprehensive 3D CFD-based computational model presented and documented in Part 1. Simulations for unit cells with straight channels, similar to the Ballard Mk902 hardware, are performed and analyzed in conjunction with detailed current mapping measurements and water mass distributions in the membrane-electrode assembly. The experiments were designed to display sensitivity of the cell over a range of operating parameters including current density, humidification, and coolant temperature, making the data particularly well suited for systematic validation. Based on the validation and analysis of the predictions, values of model parameters, including the electro-osmotic drag coefficient, capillary diffusion coefficient, and catalyst specific surface area are determined adjusted to fit experimental data of current density and MEA water content. The predicted net water flux out of the anode (normalized by the total water generated) increases as anode humidification water flow rate is increased, in agreement with experimental results. A modification of the constitutive equation for the capillary diffusivity of water in the porous electrodes that attempts to incorporate the experimentally observed immobile (or irreducible) saturation yields a better fit of the predicted MEA water mass with experimental data. The specific surface area parameter used in the catalyst layer model is found to be effective in tuning the simulations to predict the correct cell voltage over a range of stoichiometries.

Preparation of Copper-Cobalt Catalyst by Glow Discharge Plasma for Lower Alcohols Synthesis

CuCo/ZrO2 catalysts for lower-alcohol synthesis from syngas were prepared by glow discharge plasma and conventional calcination method. The effects of plasma atmosphere(N2, H2 or first N2 then H2) on the catalyst structure and performance were investigated. These catalysts were characterized using BET, XPS, XRD, TG, and TPR techniques. The experimental results indicated that plasma treatment restrained effectively the production of hydrocarbon and enhanced the selectivity to total alcohols. Compared with the calcined sample, the plasma treated catalyst had higher activity and space time yield (STY). Characterization results showed that the catalyst precursor with plasma treatment was decomposed to active phase under low temperature and the specific surface area of catalyst was significantly improved. Meanwhile, the plasma treatment promoted the grain refining, dispersion of the active component and enrichment of copper on the catalyst surface.

Isomerization Cracking of n-Octane and n-Decane on Regulated Acidity Pt/WOx−SO4−ZrO2 Catalysts

The effect of WO3 loading on the acidity and specific surface area of catalysts composed of Pt supported on ZrO2 and double-promoted with SO42- and WO3 catalysts (PtWSZ) was studied. The catalysts were tested in the isomerization cracking of heavy alkanes, and the objective was to assess their ability to produce branched shorter alkanes, contributing to the gasoline pool. As a consequence, the focus was put on the maximization of the yield of C4−C7 isomers (i-C4-7). The catalysts were characterized by several techniques. The crystalline structure was analyzed by XRD. The acidity of the catalysts was measured by thermal desorption of pyridine. A screening and first selection of the most promising catalysts was done by means of the reaction of n-octane at 300 °C, 0.1 MPa, WHSV = 1 and H2/nC8 = 6 mol/mol. A high yield of i-C8 was obtained with the Pt/WO3−ZrO2 catalyst. The incorporation of SO42- as a promoter increased the acidity and the cracking activity. Pt/SO42-−ZrO2 displayed very strong acid sites and generated the highest amount of light hydrocarbons. Catalysts of regulated acidity combining both promoters yielded the best results. The most promising PtWSZ catalyst was obtained with 5% W and 1.4% S. The test reaction of n-decane at near-industrial conditions (1.5 MPa, 300 °C, WHSV = 4, H2/n-C10 = 6 mol/mol) was used for a further assessment of the catalytic properties. This test confirmed that the double-promoted catalyst (PtWSZ, 5% W, 1.4% S) had high activity and stability and produced an isomerizate with the highest i-C4-7/i-Ctotal molar ratio in comparison to the sulfated zirconia (PtSZ) and tungstated zirconia (PtWZ) catalysts.

Catalytic activity of oxides and halides on hydrogen storage of MgH 2

Hydrogen sorption kinetics of ball milled MgH 2 with and without chemical additives were studied. We observed kinetics and capacity improvement with increasing the number of sorption cycles that contributed to the micro/nano cracking of MgH 2 particles, shown by XRD and SEM studies. In addition, to investigate the proposed specific role of O 2−-based additives on the sorption kinetics of MgH 2, we have undertaken a comparative study evaluating the performances of MgH 2 containing the NbCl 5, CaF 2 or Nb 2O 5 additives. At 300 °C, addition of NbCl 5 and CaF 2 improved the sorption capacity to 5.2 and 5.6 wt% within 50 min, respectively, in comparison to the required 80 min in the case of Nb 2O 5. This suggests the importance of the chemical nature of the catalyst for hydrogen sorption in MgH 2. In addition, the catalyst specific surface area was shown to be very critical. High surface area Nb 2O 5 (200 m 2 g −1), prepared by novel precipitation method, exhibits an excellent catalytic activity and helped to desorb 4.5 wt% of hydrogen from MgH 2 within 80 min at a temperature as low as 200 °C.

Non‐Isothermal Crystallization Behavior of Poly(trimethylene terephthalate) Synthesized with Different Catalysts

AbstractSummary: Non‐isothermal crystallization behavior of PTT resins synthesized with different catalysts was studied by using differential scanning calorimetry (DSC) and polarized light microscopy (PLM). The results showed that with the increase of the cooling rate, the crystallization temperature for poly(trimethylene terephthalate) (PTT) resin decreased, which indicated that the crystallization process was controlled by the nucleation. Catalyst had no effect on the crystallization development process, but had somewhat effect on the non‐isothermal crystallization mechanism. The average values of Avrami exponent, for PTT with different catalysts were between 3 and 4. It was assumed that the non‐isothermal crystallization mechanism for PTT with or without catalyst was the combination of homogenous and heterogeneous nucleation and spherulite growth, but it mainly depended on the latter. For sample 4, the non‐isothermal crystallization underwent secondary crystallization process when cooling rate was over 20 °C/min. At the same cooling rate, the crystallization temperature, the crystallization ability and the crystallization rate of PTT resins followed the sequence as: sample 2 &gt; sample 1 ≈ sample 3 ≈ sample 4, which proved that catalysts could significantly prompt crystallization. The cooling rate had significant effect on the crystallization ability parameters of PTT, i.e., with the increase of cooling rate, the crystallization ability declined. Although catalyst could increase the crystallization ability of PTT, the effect was very limited because the effect of the molecular weight on the crystallization ability would be superior to the catalyst when the molecular weight of PTT was significantly high. The specific surface area of catalyst had also a great influence on the spherulitic morphology of PTT formed in the cooling process. The spherulite dimensions decrease with increasing the specific surface area of catalyst because of an increase in the nucleation rate, which produces more and smaller spherulites that can not grow larger before impinging on each other. magnified image

The catalytic oxidation of aromatic hydrocarbons over supported metal oxide

The catalytic activity of metals (Cu, Mn, Fe, V, Mo, Co, Ni, Zn)/γ-Al 2O 3 was investigated to bring about the complete oxidation of benzene, toluene and xylene (BTX). Among them, Cu/γ-Al 2O 3 was found to be the most promising catalyst based on activity. X-ray diffraction (XRD), Brunauer Emmett Teller method (BET), electron probe X-ray micro analysis (EPMA) and temperature programmed reduction (TPR) by H 2 were used to characterize a series of supported copper catalysts. Increasing the calcination temperature resulted in decreasing the specific surface areas of catalysts and, subsequently, the catalytic activity. Copper loadings on γ-Al 2O 3 had a great effect on catalytic activity, and 5 wt.% Cu/γ-Al 2O 3 catalyst was observed to be the most active, which might be contributed to the well-dispersed copper surface phase. Using TiO 2 (anatase), TiO 2 (rutile), SiO 2 (I) and SiO 2 (II) as support instead of γ-Al 2O 3, the activity sequence of 5 wt.% Cu with respect to the support was γ-Al 2O 3>TiO 2 (rutile)>TiO 2 (anatase)>SiO 2 (I)>SiO 2 (II), and this appeared to be correlated with the distribution of copper on support rather than with the specific surface area of the catalyst. The smaller particle size of copper, due to its high dispersion on support, had a positive effect on catalytic activity. The activity of 5 wt.% Cu/γ-Al 2O 3 with respect to the VOC molecule was observed to follow this sequence: toluene>xylene>benzene. Increasing the reactant concentration exerted an inhibiting effect on the catalytic activity.

Preparation and Characterization of Metal Sulfide Electro-catalysts for PEM Fuel Cells

ABSTRACTRuthenium sulfide samples were prepared by flowing pure hydrogen sulfide into an aqueous solution of ruthenium chloride followed by further sulfidation in hydrogen sulfide. The final products were characterized by X-ray diffraction and crystallite-sizes were estimated from line broadening. The specific surface areas of catalysts were measured using the multipoint BET method and compositions were determined by thermogravimetric analysis. Ruthenium sulfide loaded gas diffusion electrodes were fabricated by a spraying technique and their electrochemical behavior studied. The electrochemical oxidation of hydrogen was investigated in a three -electrode cell using a ruthenium sulfide loaded gas diffusion electrode as the working electrode with humidified hydrogen containing small amounts of carbon monoxide. Results on the activity and the effects of carbon monoxide with reference to a standard platinum electrode measured at the same conditions show that ruthenium sulfide has a lower activity for hydrogen oxidation but is not susceptible to CO poisoning.

Design, modelling and experimentation of a new large-scale photocatalytic reactor for water treatment

Recent literature has demonstrated on a laboratory scale the potential of semiconductor photocatalysis technology to completely destroy organic pollutants present in water. However, to date no viable pilot plant exists using this technology. In this paper, a new reactor design is presented that addresses the two most important parameters, namely, light distribution inside the reactor and high specific surface area of catalyst. The reactor consists of several hollow tubes employed as a means of light delivery to the catalyst present on the outside surface of the tubes. Simple model calculations were performed to evaluate the radial light intensity profile as a function of input light intensity and angle of incidence, diameter, length, wall thickness and surface roughness of tubes. A reactor was designed and constructed based on the modelling results, and when experiments were conducted showed very promising results. The new reactor aims at developing a technical solution to the design of a commercial scale photocatalytic reactor.

Preparation of high loading silica supported nickel catalyst: simultaneous analysis of the precipitation and aging steps

The precipitation and aging steps used for the preparation of high loading silica supported nickel catalysts were simultaneously analyzed with the aid of statistical design of experiments. Empirical models relating catalyst final properties and preparation variables were developed. It was found that the precipitation step determines the final catalyst nickel content, and that at low nickel concentrations high metallic area per gram of reduced nickel may be attained with the precipitated precursor without performing the aging step. When it is performed, the aging step has a strong influence on final catalyst properties, such as specific surface area, metallic area per gram of nickel and degree of reduction. Therefore, catalyst aging may be an effective method to control dispersion, reducibility and active phase accessibility. The importance of the aging step was shown to increase with the aging temperature, which is linked to the larger rates of silicate formation at high temperatures. A semi-empirical model was developed to describe the final catalyst specific surface area as a function of the rate of silicate formation. This model is able to describe changes of the catalyst surface area fairly well and allow the proper manipulation of preparation conditions in order to maximize the catalyst specific area, leading to maximum catalyst activities.

Structure and Texture of Nickel‐Molybdenum Catalysts on Alumina Support Modified with Fluoride or Chloride Ions

AbstractThe performed study involves measurements of a specific surface area via a BET method, of the pore volume, FT‐IR, and a derivatographic study of a series of Al2O3‐supported nickel‐molybdenum catalysts modified with fluoride and chloride ions. It was found that fluoride ions lead to a decrease in the specific surface area of catalysts, whereas chloride ions have a small effect on this parameter. Modification does not change the type of pores of the catalysts, yet it affects their size and increases concentration of OH groups adsorbed on the surface of the catalysts relative to the carrier and the unmodified catalyst. Addition of fluoride ions decreases the thermal stability of the catalyst, whereas chloride ions does not cause any change.

MgCl2·6H2O‐based titanium catalysts for propylene polymerization. Chemical composition and productivity

AbstractMgCl2·6H2O was reacted with dichlorodiphenylsilane to obtain anhydrous magnesium dichloride. MgCl2 thus obtained was solubilized in 2‐ethyl‐1‐hexanol to prepare titanium catalysts for propylene polymerization through regeneration of magnesium dichloride by reaction with titanium tetrachloride. The nature of internal lewis base dialkyl phthalate [Ph(COOR)2, where R = Me, Et, and n‐Bu] and reactants concentration (alcohol and dialkyl phthalate) influence the chemical composition and specific surface area of catalysts. The activity of the catalysts changes in the order ßmethyl &lt; ethyl &lt; butyl. The polymerization parameters such as Al/Ti mole ratios, aging time of catalysts and cocatalysts (triethylaluminium) also control the activity. The concentration of the external Lewis base (dimethoxydiphenylsilane) improves the stereospecifity of the catalyst system.