Catalyst

A new kinetic model for the fluid catalytic cracking (FCC) riser is developed. An elementary reaction scheme, for the FCC, based on cracking of a large number of lumps in the form of narrow boiling pseudocomponents is proposed. The kinetic parameters are estimated using a semi-empirical approach based on normal probability distribution. The correlation proposed for the kinetic parameters' estimation contains four parameters that depend on the feed characteristics, catalyst activity, and coke forming tendency of the feed. This approach eliminates the need of determining a large number of rate constants required for conventional lumped models. The model seems to be more versatile than existing models and opens up a new dimension for making generic models suitable for the analysis and control studies of FCC units. The model also incorporates catalyst deactivation and two-phase flow in the riser reactor. Predictions of the model compare well with the yield pattern of industrial scale plant data reported in literature. ᭧

Abstract: The extensive demand for cleaner environment is forcing chemical industry to use less hazardous materials. In this regard, heteropolyacids attracted considerable amount of interest due to the less toxic behavior in addition of possessing higher acidity. Heteropoly acids have been used as catalysts for the reaction of salicylic acid with acetic anhydride. The performance of different forms of heteropoly acids in the presence of acetic anhydride as acetylating agent for acetylation of salicylic acid was compared. The best conditions were observed using Preyssler and Silica-supported Preyssler Nanoparticles as catalysts. The catalyst is recyclable and reusable.

Rechargeable lithium-air battery is studied using Pd/mesoporous ␣-MnO 2 air composite electrode. In the present work, we have studied the preparation and electrochemical performance of ordered mesoporous ␣-MnO 2 as a cathode catalyst for rechargeable Li-air batteries. ␣-MnO 2 was prepared by reduction of KMnO 4 solution in acidic aqueous solution followed by successive proton and alkali-ion exchange method. ␣-MnO 2 with high surface area of 33-133.0 m 2 g −1 was successively synthesized and used as an electrode catalyst for Li-air battery. It was found that the mixture of Pd and mesoporous ␣-MnO 2 electrode shows the high activity to oxidation and reduction of Li to form Li 2 O 2 or Li 2 O. Application of Pd/mesoporous ␣-MnO 2 , which is mixed with teflonized acetylene binder (TAB), for air electrode is effective for decreasing the charge potential and also improved the energy efficiency as well as cyclability.

Abstract—People today are increasingly health conscious and therefore shopkeepers tend to dispose of fatty chicken and pork skin. Chicken and pork skins thus are sources of solid waste that are usually not utilized. This paper deals with the production of useful biodiesel from utilizing the waste chicken and pork skins. Fat from the waste chicken and pork skins (sourced from local shops), was first extracted and subjected to transesterification. The products of transesterification were FAME (Fatty acid methyl esters) and glycerol. The FAME produced was tested for five parameters namely calorific value, pour point and cloud point when compared to ASTM E2515-11 standard values. Comparison of the obtained values of the five parameters with the standard values for diesel was performed to determine the viability of the biodiesel produced. The results of this experiment showed that the calorific values of FAME produced from chicken skin and pork skin fat were close to that of petroleum de...

Cavitation can be effectively used for intensification of chemical processing applications and the degree of intensification depends on operating parameters. A mathematical model has been developed for prediction of cavitational intensity quantified in terms of collapse pressure and temperature. Effect of different solvents and catalyst particles, which are the key controlling parameters for hydrogenation reactions, on cavitational intensity has been investigated. The observed trends have been compared with the experimental investigations. The importance of present work lies in the fact that it provides a pathway for optimization of operating parameters and establishes guidelines for the selection of the same.

A synthetic clay (TS-1) was modified with a nonionic surfactant (IGEPAL CO-720) and magnesium oxide. The resulting solid was used as a support of Pt, Mo, and Pt-Mo catalysts. The catalysts were prepared by wet impregnation with aqueous solutions of H 2 PtCl 6 •6H 2 O and (NH 4) 6-Mo 7 O 24 •4H 2 O. In both monometallic and bimetallic catalysts, the molybdenum content was 3 wt% and the platinum content was 0.5 or 1 wt%. The surface area of the starting material was 454 m 2 /g and after the modification treatment with IGEPAL it increased up to 649 m 2 /g, while platinum and molybdenum catalysts showed surface areas between 495 and 550 m 2 /g. The reduction profiles showed different Pt and Mo species and the existence of metal-support interactions. The reduced catalysts were more active than those in the unreduced form. The most active catalysts for the ethylbenzene dehydrogenation were those of monometallic Pt (0.5 and 1 wt%) with a maximum styrene conversion around 50%. The presence of Mo species masked Pt atoms and reduced the activity.

The synthesis of fullerenes was carried out using dc arc discharge technique. The separation and identification of higher fullerene C 84 was done by high performance liquid chromatography (HPLC). The raw soot collected from the high temperature region was dissolved in toluene and then toluene-extracted soot dissolved in n-hexane and kept in laboratory environment for more than one month. The peaks of C 60 and C 70 along with C 84 were observed. The existence of C 84 was confirmed by using linear regression between capacity factor log [k′] and the carbon number.

The structure of copper iron pyrophosphate catalysts prepared with various atomic ratios of metals and different pretreatment conditions was studied by using XRD, FT-IR, DR UV-vis and H 2 -TPR techniques. The preparation methods modify the phase composition, oxidation state and reducibility of the patterns. The catalytic properties in the selective oxidation of methane to formaldehyde and methanol were examined in both, pulse and flow reactors, using O 2 and/or N 2 O oxidizing agents. The oxidants used impact the onset of methane conversion, the primary oxidation products formation and the methane conversion. The highest single-pass yield of useful oxygenates (1.8%) was achieved with N 2 O over the Cu/Fe ∼ = 1:2 pyrophosphate catalyst which consists mainly of the crystalline Fe II Fe III 2 (P 2 O 7 ) 2 and copper containing nanodomains. Enhanced interaction and cooperation between these phases leading to a synergic effect of Cu and Fe has been emphasized. The Cu II and Fe III species of the above structure can be reduced more easily but at similar temperatures than those in the crystalline CuFe 2 (P 2 O 7 ) 2 . Pulse reaction studies indicate that the lattice oxygen of the catalyst could react with methane molecules producing formaldehyde and methanol and replenishment of the lattice oxygen by N 2 O takes place rather readily and rapidly. The nature of active species, methane conversion and oxygenates selectivity remained almost unchanged during the time on stream.

Hydrogen evolution was observed from the noble-metal-free catalyst systems, comprising Rose Bengal, BF xbridged cobaloximes, and triethylamine, in an aqueous solution under irradiation of visible light. Two types of BF x -bridged cobaloximessnamely, the annulated cobaloximes [Co(dmgBF 2 ) 2 (H 2 O) 2 ] (1, dmgBF 2 ) (difluoroboryl)dimethylglyoximate anion) and [Co(dpgBF 2 ) 2 (H 2 O) 2 ] (2, dpgBF 2 ) (difluoroboryl)diphenylglyoximate anion), and the clathrochelated cobaloximes [Co(dmg(BF) 2/3 ) 3 ](BF 4 ) (3) and [Co(dpg(BF) 2/3 ) 3 ](BF 4 ) (4)swere used as catalysts. Among the four cobalt complexes, complex 1 displayed the highest hydrogenevolving efficiency, with turnovers up to 327. Complexes 2 and 4 that bear the diphenylglyoximate ligands exhibited much lower efficiencies as compared with their analogues 1 and 3 that have the dimethylglyoximate ligands. The hydrogen-evolving efficiency of the annulated cobalt(II) complex 1 that contains two labile axial ligands is more than three times as high as that of the encapsulated cobalt(III) complex 3 that has a single macrobicyclic ligand. The different pathways for formation of the cobalt(I) species from these two types of cobaloximes are discussed on the basis of the results obtained from fluorescence and laser flash photolysis spectroscopic studies.

ABSTRACT  Stable, active, and highly selective bifunctional Ni/Al-MCM-41 catalysts were developed for the one-pot synthesis of menthols from citral. The liquid-phase hydrogenation of citral to citronellal was studied on silica-supported noble (Pt, Pd, Ir) and nonnoble (Ni, Co, Cu) metals. It was found that citronellal is selectively formed at the beginning of the reaction only on Pd and Ni catalysts. The consecutive ene-cyclization of citronellal to isopulegols was investigated on solid acids containing exclusively Lewis (ZnO/SiO2) or strong Brönsted (CsHPA) acid sites, and also on catalysts containing both Lewis and Brönsted acid sites of either strong (zeolites, SiO2–Al2O3) or moderate (Al-MCM-41) strength. The isopulegol formation rate was higher on samples exhibiting dual Lewis/Brönsted acidity, such as SiO2–Al2O3, Al-MCM-41, and zeolite HBEA. Based on these previous results, bifunctional catalysts containing Pd or Ni supported on SiO2–Al2O3, Al-MCM-41, or zeolite HBEA were prepared and tested for citral conversion to menthols. The catalyst stability and the effect of hydrogen pressure and metal loading on menthol productivity were also investigated. The best catalyst was Ni(8%)/Al-MCM-41, which yielded more than 90% menthols at 2026.0 kPa and showed no significant deactivation after two consecutive catalytic tests.

NiS-P zeolite was prepared by ion exchange and precipitation procedures and it was characterized by FT-IR, SEM and thermal methods. The prepared composite was used as a catalyst in the photodecolorization process of Eriochrome Black T (E.B.T.) dye in aqueous solution under UV irradiation. The effect of key operating parameters such as catalyst dosage, temperature, initial concentration of the dye and initial pH of the solutions were studied on the decolorization process of dye. The primary objective was to determine the optimal conditions for each of the parameters. UV-vis spectrophotometric measurements were performed for the determination of decolorization and mineralization extents. The optimal operation parameters were found as follows: pH 9.1, 0.8 g L −1 of catalyst loading and 40 ppm of dye concentration. The NiS particles out of zeolite framework did not show significant decolorization efficiency. The decolorization process obeyed first-order kinetics.

This work demonstrates the high potential of a new class of catalytic materials based on nickel for the oxidative dehydrogenation of ethane to ethylene. The developed bulk Ni-Nb-O mixed oxides exhibit high activity in ethane ODH and very high selectivity (∼90% ethene selectivity) at low reaction temperature, resulting in an overall ethene yield of 46% at 400 • C. Varying the Nb/Ni atomic ratio led to an optimum catalytic performance for catalysts with Nb/Ni ratio in the range 0.11-0.18. Detailed characterization of the materials with several techniques (XRD, SEM, TPR, TPD-NH 3 , TPD-O 2 , Raman, XPS, electrical conductivity) showed that the key component for the excellent catalytic behavior is the Ni-Nb solid solution formed upon the introduction of niobium in NiO, evidenced by the contraction of the NiO lattice constant, since even small amounts of Nb effectively converted NiO from a total oxidation catalyst (80% selectivity to CO 2 ) to a very efficient ethane ODH material. An upper maximum dissolution of Nb 5+ cations in the NiO lattice was attained for Nb/Ni ratios 0.18, with higher Nb contents leading to inhomogeneity and segregation of the NiO and Nb 2 O 5 phases. A correlation between the specific surface activity of the catalysts and the surface exposed nickel content led to the conclusion that nickel sites constitute the active centers for the alkane activation, with niobium affecting mainly the selectivity to the olefin. The incorporation of Nb in the NiO lattice by either substitution of nickel atoms and/or filling of the cationic vacancies in the defective nonstoichiometric NiO surface led to a reduction of the materials nonstoichiometry, as indicated by TPD-O 2 and electrical conductivity measurements, and, consequently, of the electrophilic oxygen species (O − ), which are abundant on NiO and are responsible for the total oxidation of ethane to carbon dioxide.

Five kraft lignins from softwood and hardwood and one softwood lignin from the organocell process were convened into an oil-like product by hydrotreatment at 400°C for 40 minutes in the presence of different catalysts. The total oil yields varied in the range 49-71% wt of the original lignin feedstock. The highest yield was obtained for organosolv lignin using a catalyst mixture of sulfided NiMo on aluminosilica (M8-81) : CreO 3 (M9-10) (1:1). Detailed GLC analysis of the low-molecularweight components in the oil products (the total amounts of 14-38% wt of the original lignin) indicated the presence of various alkyl benzenes, phenols, and polycyclic aromatics.

In previous work, steady-state isotope switching was conducted on Pt/ceria with H 2 O and D 2 O, and a normal kinetic isotope effect was observed. Diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) indicated that the surface coverage of H-formate was more limited by the WGS rate than that of D-formate, linking the rate limiting step to the breaking of the formate C-H bond.

The theory of a globular grain model was used to construct an algorithm for analysing the problem of how the porous structure of heterogeneous catalysts affects their efficiency in model reforming reactions. Our analysis has substantiated the undeniable advantage of applying the bidispersive grain structure since its effectiveness is many times as high as the effectiveness of the monodispersive grain structure. Apparently, the method described in the present paper will be equally efficient when applied to heterogeneous catalysts made use of in other technological processes.

Photocatalytic reduction of mercury in aqueous solutions using PW 12 O 40 3or SiW 12 O 40 4as photocatalysts has been studied as a function of irradiation time, concentration of Hg(II), polyoxometalate, and organic substrate in the presence or absence of dioxygen. The photocatalytic cycle starts with irradiation of polyoxometalate, goes through the oxidation of, for instance, propan-2-ol (used as sacrificial reagent), and closes with the reoxidation of reduced polyoxometalate by Hg 2+ ions. Mercury(II) is reduced to mercury(I) and finally to Hg 0 giving a dark-gray deposit, following a staged one-by-one electron process and a firstorder kinetics in [Hg 2+ ]. The process is slightly more efficient in the absence of dioxygen, while the increase of either catalyst or propan-2-ol concentration results in the augmentation of the rate of reduction till a certain point where it reaches a plateau. The results show that this method is suitable for a great range of mercury concentration from 20 to 800 ppm achieving almost complete recovery of mercury up to nondetected traces (<50 ppb). In addition, this homogeneous process demonstrates advantages such as the lack of necessity for separation of the zero state metal from the catalyst and ensures that the precipitation of metal will not poison the catalyst or hinder its photocatalytic activity.

Quinoxaline derivatives have been synthesized in high yields in the presence of cellulose sulfuric acid as an inexpensive, recyclable and biodegradable solid acid catalyst in H 2 O or EtOH at room temperature. To cite this article: A. Shaabani et al., C. R. Chimie 12 (2009). #

The potential eco-toxicity of nanosized titanium dioxide (TiO2), silicon dioxide (SiO2), and zinc oxide (ZnO) water suspensions was investigated using Gram-positive Bacillus subtilis and Gram-negative Escherichia coli as test organisms. These three photosensitive nanomaterials were harmful to varying degrees, with antibacterial activity increasing with particle concentration. Antibacterial activity generally increased from SiO2 to TiO2 to ZnO, and B. subtilis was most susceptible to their effects. Advertised nanoparticle size did not correspond to true particle size. Apparently, aggregation produced similarly sized particles that had similar antibacterial activity at a given concentration. The presence of light was a significant factor under most conditions tested, presumably due to its role in promoting generation of reactive oxygen species (ROS). However, bacterial growth inhibition was also observed under dark conditions, indicating that undetermined mechanisms additional to photocatalytic ROS production were responsible for toxicity. These results highlight the need for caution during the use and disposal of such manufactured nanomaterials to prevent unintended environmental impacts, as well as the importance of further research on the mechanisms and factors that increase toxicity to enhance risk management.

A highly enantioselective Michael reaction of aromatic ketones with nitroolefins was accomplished in the presence of a chiral bifunctional primary amine-thiourea catalyst and 4-nitrobenzoic acid as the co-catalyst; the corresponding adducts were obtained in excellent enantioselectivities (up to 99 % ee) and yields (up to 98 %). The catalytic mechanism of the Michael reaction was confirmed through the ESI-MS

The application of dielectric heat transfer in the catalytic cracking and hydrocracking of gas oils has been investigated. A three-phase spouted-bed catalytic reactor has been designed and operated using dielectric radio frequency (RF) heating. The electromagnetic power was transferred to the reactor by a 27.12 MHz RF generator acting through two capacitor plates. In this technique, heat is generated to the catalyst held in the electromagnetic field and thermal energy dissipated to the surroundings of the catalyst volume preventing carbon formation by eliminating secondary reactions. Energy transfer from the RF filed to the reaction was solely dependent on the dielectric properties of solids in the reactor, effectively the catalyst or transient carbon. Three zeolitic catalysts have been tested. These catalysts were 13X, 5A and Ammonium Y Zeolite. Two different gas oils have been used as feedstocks for the experiments. Saudi Light Vacuum Gas Oil (SALVGO) supplied by Saudi Aramco Oil and North Sea Light Gas Oil (BPLGO) supplied by BP Oil. A comparative study of the two gas oils cracked over 13X zeolitic catalyst has been presented. The analysis of the feedstocks have shown that SALVGO contains hydrocarbons in the range C 11 -C 30 with average molecular weight of 294, while BPLGO contains hydrocarbons in the range C 11 -C 25 with average molecular weight of 243. The analysis of cracked products have shown a production of lower olefins such as propene and butene with hydrogen sulphide from SALVGO at a conversion of 87% and aromatics such as benzene and toluene from BPLGO at a conversion of 72%. The successful use of zeolitic catalyst in producing lower olefins and aromatics with an RF dielectric reactor suggests exploring this type of reactor for objectives such as the production of reformulated gasoline, in which butene is used as feedstock for production of high-octane gasoline components such as MTBE and alkylate. D

This review focuses on the importance of coupling of catalytic reactions which involves dehydrogenation
and hydrogenation simultaneously and the study of catalytic materials that are designed, adopted
and/or modified for these reactions. The special features of these reactions are minimization of H2 utilization
and reduction in production cost. Structural and textural properties also play a decisive role in this kind of
coupled reactions. This particular review although not comprehensive discusses the significant progress made
in the area of coupled reactions and also helps future researchers or engineers to find out the improvements
required in areas such as advancements in catalytic material preparation, design of the new reactors and the
application of new technologies.

Hydrogen production from waste tires was investigated using a two-stage pyrolysis-gasification reactor and Ni-Mg-Al (1:1:1) as a catalyst. In addition, the elastomer constituents most commonly used in tires, natural rubber (NR), styrene-butadiene rubber (SBR), and butadiene rubber (BR), were also investigated. Experiments were conducted at a pyrolysis temperature of 500°C and gasification temperature of 800°C. The results showed that the gas and hydrogen yield were increased for the tire and elastomer constituents during pyrolysis-gasification. However, there was a dramatic increase in H 2 and CO concentrations as well as a consequent decrease in CH 4 and C 2 -C 4 concentrations when the Ni-Mg-Al catalyst was applied to the pyrolysis-gasification process. For example, hydrogen production increased from 0.68 to 5.43 wt % for the catalytic steam pyrolysis-gasification of waste tire in the presence of Ni-Mg-Al catalyst. The highest hydrogen production (15.26 wt %) was obtained for the BR feedstock. Reacted catalysts were characterized using a variety of methods, including temperature-programmed oxidation (TPO) and scanning electron microscopy (SEM) with energy dispersive X-ray spectrometry (EDXS). The SEM results showed that large amounts of filamentous carbons were observed for the reacted Ni-Mg-Al catalysts derived from all the feedstocks. The total amount of coke deposition on the reacted catalyst, calculated from TPO experiments, was lowest for the BR feedstock (7.0 wt %) and was 31, 21.8, and 18.4 wt % for the waste tire, NR, and SBR samples, respectively.

This paper describes the pervaporation performance of film-like zeolite NaA membranes synthesized in our laboratory by template-free seeded hydrothermal towards the dehydration of n-pentanol/water and n-pentanol/water/DNPE mixtures (DNPE = din -pentyl ether, C 10 H 22 O). DNPE is a linear symmetric ether that can be used as blending additive in reformulated diesel fuels and that can be produced from C 4 feedstocks via n-pentanol, obtained in its turn by selective hydroformylation of linear butenes. The membranes showed selectivities up to 3000 in the dehydration of n-pentanol/water binary mixtures, and water/DNPE and n-pentanol/DNPE selectivities approaching infinity (i.e. DNPE does not pervaporate) in the dehydration of n-pentanol/water/DNPE ternary mixtures. On the basis of the separation results presented in this work, and using experimental reaction kinetics data, we discuss the feasibility of zeolite NaA membrane reactors to carry out the liquid-phase etherification reaction of n-pentanol to din -pentyl ether (DNPE) catalyzed by ion-exchange sulfonated resins. These catalysts suffer from strong deactivation in the progress of the reaction due to the generation of water.

Some new 1,4-distyrylbenzene derivatives were synthesized by using immobilized palladium nanoparticles on silica-bonded N-propyl morpholine (PNP-SBNPM) as a heterogeneous catalyst. These one-pot reactions afforded a range of stereoselective, symmetrical (E)-1,4-distyrylbenzene derivatives with high yields (78-90%). The green catalyst system is recyclable and allows facile product isolation. The recycled catalyst could be reused six times without appreciable loss of catalytic activity.

Carbon nanofiber/graphite-felt composite with desirable shape and size has been synthesized by the method of catalytic chemical vapor deposition (CCVD) through the growth of carbon nanofibers (CNFs) on the surface of the graphite microfibers of the felt. Scanning electron microscopy (SEM), N 2 -physisorption, and a mechanical strength test have been used to characterize the morphology, the texture properties, and the mechanical strength of the CNF/graphite-felt composites, aiming at a detailed understanding of the relationship between structure and property. The physico-chemical properties, especially the mechanical strength of the composites, have been investigated as a function of the ratio (w/w) between the CNFs and the graphite felt. Both the compressive strength and the apparent density of the composites were found to vary with the CNF yield (w/w). Their maximum values are reached at a CNF yield of about 6. Very few fragments are desquamated from the composite with a CNF yield below 5 under vigorous agitation, indicating stable anchorage of CNFs on the graphite microfibers. A distinct mesoporous character, a large external surface area and high mechanical strength make CNF/graphite-felt composites attractive as a catalyst for the oxidative dehydrogenation of ethylbenzene to styrene (ODE). An optimized ratio of 4.5 between the CNF and graphite felt in the composites exists for the catalyst in the ODE reaction with respect to both the styrene yield and mechanical strength. Moreover, the composite exhibits much greater catalytic stability than activated carbon.

Hydrogen-to-metal (H/M) ratios exceeding unity for Pt and Rh and exceeding 2 for Ir were measured for highly dispersed Pt, Rh, and Ir catalysts supported on A&O, and SiOZ. Since the coordination of hydrogen to metal atoms is unknown for such highly dispersed catalysts, the metal surface area of these catalysts cannot be calculated from the hydrogen chemisorption values. Therefore EXAFS (extended X-ray absorption fine structure) measurements were performed to determine the metal particle size and thereby to calibrate hydrogen chemisorption results. The H/M ratio determined by hydrogen chemisorption is a linear function of the average metal coordination number determined by EXAFS. This linear relationship is independent of support but varies with the metal with the H/M ratio increasing in the order Pt < Rh < Ir. Several hypotheses for the high H/M values are discussed. Spillover and subsurface hydrogen are excluded as explanations and only multiple adsorption of hydrogen on metal surface atoms is shown to be capable of explaining all experimental observations. The HiMsurface stoichiometry differs among Pt, Rh, and Ir in the order H/Pt < HiRh < H/k, analogous to the order of stability of corresponding metal polyhydride complexes and of theoretical expectation. 0 1987 Academic press, II-C.

Binderless beta zeolite has been anchored on a silicon carbide foam with a monolithic shape. The catalytic activity of the resulting composite was evaluated for a Friedel-Crafts reaction carried out in a fixed-bed configuration: the benzoylation of anisole to p-methoxybenzophenone. The results obtained were compared with those of a commercial beta zeolite. Significantly higher product yields along with a stable activity were obtained with the BEA/SiC composite. It has been suggested that the opened structure of the ␤-SiC foam and the absence of any binder allow a fast desorption of the p-ketone which is the main product of the reaction but also the major source of deactivation due to strong adsorption and/or coke formation inside the microporosity of the zeolite.

Photocatalytic degradation of nitrobenzene has been studied using a semiconductor as photocatalyst and an artificial UV source. The effect of catalyst loading, pH and anions on the photocatalytic degradation of nitrobenzene has been investigated. A kinetic model for the photocatalytic process was investigated. Two types of commercial catalysts Degussa P-25 and Aldrich-TiO 2 (anatase TiO 2 having surface area 250 m 2 g −1 ) have been compared. Also the degradation has been studied using two different lamps of different λ max . A comparison of photocatalytic degradation of nitrobenzene with phenol showed that nitrobenzene degrades more rapidly than phenol. Further, photochemical degradation of nitrobenzene using hydrogen peroxide and artificial UV lamp has been studied and found to be inferior to the photocatalytic degradation.

Ethanol steam reforming has been studied over Ni/SiO 2 catalysts under a wide range of operating conditions, and the effect of Ni loading on catalyst properties and H 2 yield and selectivity has been analyzed. Surface area and pore volume significantly decrease with nickel content, but there is only a slight decrease in mean pore diameter. XRD patterns show peaks corresponding to NiO but no evidence of nickel silicate species has been found. Ni/SiO 2 catalysts are active for H 2 production by ethanol steam reforming over 400 ºC. Ethanol conversion and H 2 yield considerably increase with temperature and Ni loading. Up to 3.9 mol H2 /mol EtOH is obtained at 600 ºC and 8.3 g catalyst min/g EtOH , although lower temperatures (500 ºC) are more suitable for minimizing CO selectivity. An improvement in catalyst performance is observed for high values of time-on-stream, which is explained by coke deposition in the form of carbon fibers.

a b s t r a c t Implantable glucose fuel cells are a promising approach to realize an autonomous energy supply for medical implants that solely relies on the electrochemical reaction of oxygen and glucose. Key advantage over conventional batteries is the abundant availability of both reactants in body fluids, rendering the need for regular replacement or external recharging mechanisms obsolete. Implantable glucose fuel cells, based on abiotic catalysts such as noble metals and activated carbon, have already been developed as power supply for cardiac pacemakers in the late-1960s. Whereas, in vitro and preliminary in vivo studies demonstrated their long-term stability, the performance of these fuel cells is limited to the W-range. Consequently, no further developments have been reported since high-capacity lithium iodine batteries for cardiac pacemakers became available in the mid-1970s. In recent years research has been focused on enzymatically catalyzed glucose fuel cells. They offer higher power densities than their abiotically catalyzed counterparts, but the limited enzyme stability impedes long-term application. In this context, the trend towards increasingly energy-efficient low power MEMS (micro-electro-mechanical systems) implants has revived the interest in abiotic catalysts as a long-term stable alternative. This review covers the state-of-the-art in implantable abiotically catalyzed glucose fuel cells and their development since the 1960s. Different embodiment concepts are presented and the historical achievements of academic and industrial research groups are critically reviewed. Special regard is given to the applicability of the concept as sustainable micro-power generator for implantable devices.

A broad set of N-arylprolinamides 1-8 with increasing NH acidity and steric crowding has been synthesized and its catalytic activity explored for enantioselective aldol reactions. In DMF containing 10 mol-% of TFA, all arylamides are found to catalyze the reaction between cyclohexanone and a variety of electrophilic aldehydes leading to aldols in excess of 90 % yield and Ͼ95 % enantioselectivity. The perfluorophenyl catalyst 8 is found to perform best with a broad substrate scope as compared to all other N-arylamides 1-7. It is shown that 8 can indeed be employed in highly nonpolar as well as polar solvents including brine to afford high yields of aldols with excellent diastereo-as well as enantioselectivity. The results observed for 8 are amongst the best reported so far for prolinamides that do not contain additional stereogenic center(s) and hydrogen-bonding site(s). The mo-[a

Fructone (2-methyl-2-ethylacetoacetate-1, 3-dioxolane), a flavouring material, has been synthesized from ethyl acetoacetate and glycol using five water-soluble Brønsted acid ionic liquids as catalysts for the first time. The used Brønsted acid ionic liquids include [Hmim]Tfa, [Hmim]Tsa, [Hmim]BF4, [Bmim]HSO4, [Bmim]H2PO4, and [Hmim]BF4 showed the highest catalytic activity for the preparation of fructone. After reaction, the product could be isolated from the reaction system automatically, and the ionic liquid could be directly reused without dehydration.

Biodiesel has been produced by transesterification of canola oil with methanol in the presence of highly Brønsted acidic ionic liquids based on 1-benzyl-1H-benzimidazole, and the effect of reaction temperature, type and amount of catalyst, molar ratio and reaction time investigated. The results show that the 4B ionic liquid has the highest catalytic activity and best recyclability under the optimised reaction conditions. Thus, this ionic liquid is able to catalyze the transesterification of canola oil to its methyl esters in 5 h with yields of more than 95%. Density functional calculations (B3LYP), using the 6-311G basis set, have been performed to have a better understanding on the reactivity of these catalysts. The catalytic activity of 4B for the transesterification of other vegetable oils and alcohols has also been studied.

Biomass-derived methane-rich gases such as landfill gas (LFG), biogas and digester gas are promising renewable resources for near-future production of hydrogen. The technical and economical feasibility of hydrogen production via catalytic reforming of LFG and other methane-rich gases is evaluated in this paper. The thermodynamic equilibrium calculations and experimental measurements of reformation of methane-rich CH 4-CO 2 mixtures over Ni-based catalyst were conducted. The problems associated with the catalyst deactivation due to carbon lay down and effects of steam and oxygen on the process sustainability were explored. Two technological approaches distinguished by the mode of heat input to the endothermic process (i.e., external vs autothermal) were modeled using AspenPlus TM chemical process simulator and validated experimentally. A 5 kW th pilot unit for hydrogen production from LFG-mimicking CH 4-CO 2 mixture was fabricated and operated. A preliminary techno-economic assessment indicates that the liquid hydrogen production costs are in the range of $3.00-$7.00 per kilogram depending upon the plant capacity, the process heat input option and whether or not carbon sequestration is included in the process.

Suppose that a random process Z(s; t), indexed in space and time, has a spatio-temporal stationary covariance C(h; u), where h 2 IR d (d 1) is a spatial lag and u 2 IR is a temporal lag. Separable spatio-temporal covariances have the property that they can be written as a product of a purely spatial covariance and a purely temporal covariance. Their ease of de nition is counterbalanced by the rather limited class of random processes to which they correspond. In this article, we derive a new approach that allows one to obtain many classes of nonseparable, spatio-temporal stationary covariance functions and we t several such to spatio-temporal data on wind speed over a region in the tropical western Paci c ocean.

In the present research, differential evolution (DE) method has been used to optimize the operating conditions of a radial flow spherical reactor containing the naphtha reforming reactions. In this reactor configuration, the space between the two concentric spheres is filled by catalyst. The dynamic behavior of the reactor has been taken into account in the optimization process. The achieved mass and energy balance equations in the model are solved by orthogonal collocation method. The goal of this optimization is to maximize the hydrogen and aromatic production which leads to the maximum consumption of the paraffins and naphthenes. In order to reach this end, the inlet temperature of the gas at the entrance of each reactor, the total pressure of the process, as well as the catalyst distribution in each reactor have been optimized using the differential evolution (DE) method. The results of the optimization of the spherical reactor have been compared with the non-optimized spherical reactor. The comparison shows acceptable enhancement in the performance of the reactor.

The interaction of CO 2 and H 2 /CO 2 with pure β-Ga 2 O 3 and Pd/β-Ga 2 O 3 (1 wt% Pd) was studied by temperature-programmed reaction, between 323 K and 723 K at 0.1 MPa, using in situ FTIR spectroscopy. Under CO 2 (g), bicarbonate, bidentate, and polydentate carbonate species are formed over the surface of gallia at 323 K. When β-Ga 2 O 3 is exposed to H 2 /CO 2 only polydentate carbonate reacts with hydrogen, at T > 473 K (i.e., after the dissociative adsorption of H 2 on gallia), to give bidentate and monodentate formate species (b-HCOO and m-HCOO, respectively) which are further hydrogenated to methoxy groups, just over 523 K. It is proposed that the addition of Pd to the oxide support only increases the hydrogenation rate of all the carbon-containing species bonded to the β-Ga 2 O 3 surface, by spillover of atomic H from metallic Pd to gallia: (i) at 323 K (bi)carbonate groups are hydrogenated to m-HCOO and b-HCOO, and (ii) from 423 K upwards m-HCOO is further transformed to methoxy. A strong evidence of the interconversion between m-HCOO and b-HCOO was also found.  2004 Elsevier Inc. All rights reserved.

While transition metal catalyzed cross-couplings have been successfully employed with a wide range of halides and organometallics, 1 some substrate classes still pose significant challenges. This is the case with 2-pyridyl organometallics, whose frequent instability and difficult synthesis severely limits their application. For example, while the coupling of 2-halopyridines with aryl boronic acids is well precedented, 2 the inherent instability of 2-pyridyl boronic acid makes successful cross-couplings with this nucleophile rare. 3 Given the importance of 2-arylpyridines in materials 4 and medicinal chemistry, 5 the development of a readily available, bench-stable replacement for 2-pyridyl organometallics in cross-coupling reactions would find significant use in the preparation of this class of molecule.