Catalytic Removal of Toluene over Co3O4–CeO2 Mixed Oxide Catalysts: Comparison with Pt/Al2O3

The catalytic oxidation of toluene, chosen as VOC probe molecule, was investigated over Co₃O₄, CeO₂ and over Co₃O₄–CeO₂ mixed oxides and compared with the catalytic behavior of a conventional Pt(1 wt%)/Al₂O₃ catalyst. Complete toluene oxidation to carbon dioxide and water was achieved over all the investigated systems at temperatures below 500 °C. The most efficient catalyst, Co₃O₄(30 wt%)–CeO₂(70 wt%), showed full toluene conversion at 275 °C, comparing favorably with Pt/Al₂O₃ (100% toluene conversion at 225 °C).     

Reactivity of LaNi1−y Co y O3−δ Perovskite Systems in the Deep Oxidation of Toluene

In the present work we have evaluated the oxidation of toluene over different lanthanum perovskites with a general composition of LaNi_1?y Co _y O_3?δ. These catalysts, prepared by a spray pyrolysis method, have been characterised by XRD, BET and FE-SEM techniques. Additional experiments of temperature programmed desorption of O₂, reduction in H₂ and X-ray absorption spectroscopy were also performed in order to identify the main surface oxygen species and the reducibility of the different perovskites. The catalytic behaviour toward the oxidation of toluene (as a model for VOCs compounds) was evaluated in the range 100–600 °C, detecting a total conversion for all the samples below 400 °C and higher activities for the cobalt-containing perovskites. The catalytic behaviour of these samples is consistent with a suprafacial mechanism, with the α-type oxygen playing an active role in the oxidation reaction.     

Vapor phase nitration of toluene over CuFe0.8Al1.2O4

Vapor phase nitration of toluene by using CuFe_0.8Al_1.2O₄ as a catalyst was studied by varying strength of nitric acid (10–69%) as a nitrating agent. Water vapor generated during the reaction acts as a diluent for the exothermic process. Varying the reaction temperature in the range of 100–200 °C revealed that below 125 °C lower conversion of toluene to mono-nitro toluene was obtained while above 125 °C dinitro and oxidation byproducts were obtained. The maximum conversion of toluene to mono nitro toluene was 58% with 77% selectivity towards para nitro toluene.     

Sintering‐induced aromatization during n‐heptane reforming on Pt/Al2O3 catalysts

A platinum/alumina catalyst was sintered in oxygen and hydrogen atmospheres using two metal loadings of the catalyst: 0.3% Pt and 0.6% Pt. After sintering, the aromatization selectivity was investigated with the reforming of n‐heptane as the model reaction at a temperature of 500 °C and a pressure of 391.8 kPa. The primary products of n‐heptane reforming on the fresh platinum catalysts were methane and toluene, with subsequent conversion of benzene from toluene demethylation. To induce sintering, the catalysts were treated with oxygen at a flow rate of 60 mL min^?1, pressure of 195.9 kPa and temperatures between 500 and 800 °C. The 0.3% Pt/Al₂O₃ catalyst exhibited enhanced aromatization selectivity at various sintering temperatures while the 0.6% Pt/Al₂O₃ catalyst was inherently hydrogenolytic. The fact that aromatization was absent on the 0.6% Pt/Al₂O₃ catalyst was attributed to the presence of surface structures with dimensionality between two and three as opposed to essentially 2‐D structures on the 0.3% Pt/Al₂O₃ catalyst surface. On the 0.3% Pt/Al₂O₃ catalyst, the reaction product ranged from only toluene at a 500 °C sintering temperature to predominantly cracked product at a sintering temperature of 650 °C and no reaction at 800 °C. For sintering at about 650 °C, subsequent conversion of n‐heptane was complete and dropped thereafter. The turnover number was observed to change from 0.07 to 2.26 s^?1 as the dispersion changed from 0.33 to 0.09. The Koros–Nowark (K–N) test was used to check for the presence of internal diffusional incursions and Boudart's criterion was used for structural sensitivity determination. The K–N test indicated the absence of diffusional resistances while n‐heptane reforming was found to be structure sensitive on the Pt/Al₂O₃ catalyst. Copyright © 2006 Society of Chemical Industry     

Container molecules and their guests. By Donald J. Cram & Jane M. Cram,Royal Society of Chemistry,Cambridge, 1994, xiv + 223 pp., price £49.50. ISBN 0 85186 972 6

Hydroconversion of n-heptane and toluene has been studied over a commercially proven Ni–W/SiO₂–Al₂O₃ amorphous base hydrocracking catalyst (suitable for maximizing middle distillates production from heavier feedstocks) under a wide range of operating conditions (pressure: 400–1200 psig; temperature: 315–360°C, liquid hourly space velocity (LHSV) ? 1 h^?1 and molar hydrogen/hydrocarbon feed ratio: 6–8) to assess the hydrogenation and cracking activities of the catalyst screening. Hydroisomerization followed by hydrocracking, ad hydrogenation followed by isomerization have been found to be the major reaction with n-heptane and toluene respectively as the feeds. The hydroconversion of toluene gives a very high selectivity of hydrogenated product. With n-heptane, a very high selectivity of hydroisomerized product, together with a high ratio of hydroisomerized to hydrocracked product, is obtained.     

Influence of iron on the occurrence of primary mullite in kaolin based materials: A semi-quantitative X-ray diffraction study

Iron-enriched reference kaolins (KGa-1b, KGa-2 and KF) were used to study the effect of iron on the development of mullite phases during the sintering of kaolin-based materials. Up to 1050 °C, primary mullite formation occurred at earlier temperature within iron-enriched kaolins than in the case of iron-free kaolins. At 1150 °C, the presence of ferric ions tended to promote the transformation of the spinel (γ-Al₂O₃-like) phase into primary mullite. This action was correlated with an enhancement of the diffusion mechanism of the main constitutive species of the samples (Al, Si). In the range 1300–1400 °C, iron-enriched kaolins exhibited an abnormal grain growth of secondary mullite crystals and a partial reduction of hematite (Fe₂O₃) into magnetite (Fe₃O₄). These two iron compounds reacted with mullite and cristobalite, leading to the occurrence of eutectic liquids as expected from phase equilibrium diagrams.     

The impact of Al2O3 amount on the synthesis of CASH samples and their influence on the early stage hydration of calcium aluminate cement

In this work the impact of Al₂O₃ amount on the synthesis (200?°C; 4–8?h) of calcium aluminium silicate hydrates (CSAH) samples and their influence on the early stage hydration of calcium aluminate cement (CAC) was examined. It was found that the amount of Al₂O₃ plays an important role in the formation of calcium aluminate hydrates (CAH) because in the mixtures with 2.7% Al₂O₃ only calcium silicate hydrates (CSH) intercalated with Al³⁺ ions were formed. While in the mixtures with a higher amount of Al₂O₃ (5.3–15.4%), calcium aluminate hydrate – C₃AH₆, is formed under all experimental conditions. It is worth noting that the largest quantity of mentioned compound was obtained after 4?h of hydrothermal treatment, in the mixtures with 15.4% of Al₂O₃. It was proved that synthesized C₃AH₆ remain stable up to 300?°C and at higher temperature (945?°C) recrystallized to mayenite (Ca₁₂Al₁₄O₃₃), which reacted with the rest part of CaO and amorphous structure compound, resulting in the formation of gehlenite (Ca₂Al₂SiO₇). Moreover, the synthesized C₃AH₆ addition induced the early stage of CAC hydration. Besides, in the samples with an addition, the induction period was effectively shortened: in a case of pure CAC (G70) paste, hydration takes about 6–6.5?h, while with addition – only 2–2.5?h. The synthesized and calcinated compounds was characterized by using XRD and STA analysis.     

Wetting,surface tension,and work of adhesion of As<Subscript>2</Subscript>S<Subscript>3</Subscript> and As<Subscript>2</Subscript>Se<Subscript>3</Subscript> glass melts to quartz glass

The contact angles of the quartz glass surface by the As₂S₃ and As₂Se₃ glass melts and surface tension of these glass melts in the temperature range of 325–370°С have been experimentally measured. The polytherms are linear and possess negative slope in the mentioned temperature range. The work of the adhesion of As₂S₃ and As₂Se₃ glass melts to the quartz glass surface has been calculated and compared to the data on the adhesion strength of the As₂S₃–SiO₂ and As₂Se₃–SiO₂ boundaries of the solid phases.     

Thermal evolution of Al2O3–CaO–Cr2O3 castables in different atmospheres

Al₂O₃–CaO–Cr₂O₃ castables are required for various furnaces linings due to their excellent corrosion resistance. However, toxic and water-soluble Cr(VI) could be generated in these linings during service. In this study Al₂O₃–CaO–Cr₂O₃ castables were prepared and heated at 300–1500 °C in air and coke bed to simulate actual service conditions. The formations of various phases were investigated by XRD and SEM-EDS. The Cr(VI) compounds CaCrO₄ and Ca₄Al₆CrO₁₆ formed in air at 300–900 °C and 900–1300 °C respectively, while C₁₂A₇ and CA₂ were generated rather than forming Cr(VI) compounds in coke bed at 700–1300 °C. However, at 1500 °C, nearly all the chromium existed in the form of (Al_1-xCr_x)₂O₃ solid solution in both atmosphere. As a result, the specimens treated in air contained 185.0–1697.8 mg/kg of Cr(VI) at 500–1300 °C but only 17.2 mg/kg of Cr(VI) at 1500 °C, whereas specimens treated in coke bed exhibited extremely low Cr(VI) concentration in the whole temperature range studied. Moreover, in coke bed, the mutual diffusion between Cr₂O₃ and Al₂O₃ was suppressed and a trace of Cr₂O₃ would even be reduced to form chromium-containing carbides on its surface, which would hindered the sintering process and hence lower the density as well as strength of the castables.     

Suzuki Cross-Coupling Reaction Catalyzed by the Palladium Complex Pd[N-MorphC(S)NP(O)(OiPr)2-O,S]2

Suzuki cross-coupling reaction between phenyl bromide and phenylboronic acid, catalyzed by the palladium complex Pd[N-MorphC(S)NP(O)(OiPr)₂-1,5-O,S)]₂ in acetonitrile, toluene, THF or DMF has been investigated. Bases employed for the reaction were Na₂CO₃, K₂CO₃ or Cs₂CO₃. Varying largely the experimental conditions we found that excellent yields of the product were obtained using toluene and K₂CO₃ at 100 °C at the catalyst amount of 0.02 mmol.     

Tuning the Activity and Selectivity of CuCl2/γ-Al2O3 Ethene Oxychlorination Catalyst by Selective Promotion

CuCl₂/γ-Al₂O₃ catalysts with and without promoter metal chlorides (Cu5.0, K3.1Cu5.0, La10.9Cu5.0, Li0.5Cu5.0, Cs10.4Cu5.0, Mg1.9Cu5.0, Ce5.5La5.45Cu5.0, and K1.55La5.45Cu5.0) were studied for the ethene oxychlorination reaction in a fixed-bed reactor at 503 and 573 K, with C₂H₄:HCl:O₂:He = 1.0:1.1:0.38:14.4 (mole ratio), P(tot) = 1 atm and weight hourly space velocity (WHSV) = 1.5 g g^?1 h^?1 (based on ethene). It was found that all promoter metals enhanced the activity of the catalyst, as well as its selectivity towards the target product 1,2-dichloroethane (1,2-EDC). Co-promoted catalysts (K1.55La5.45Cu5.0 and Ce5.5La5.45Cu5.0) gave even higher activity and product selectivity than the single metal promoted catalysts. The activity of the CuCl₂/γ-Al₂O₃ catalyst, as well as the γ-Al₂O₃ support, both with and without metal chloride promoter(s), were further tested for 1,2-EDC conversion to byproducts in a fixed-bed reactor at 503 K, under a feed stream of 1,2-EDC:Ar = 1:11.5 (mole ratio), at P(tot) = 1 atm and WHSV = 1.5 g g^?1 h^?1 (based on 1,2-EDC). Prior to testing, the catalysts were pretreated in flowing ethene, HCl and/or O₂. It was observed that Lewis and Brønsted acid sites on the alumina surface were main reaction sites for conversion of 1,2-EDC to chlorinated byproducts: vinyl chloride monomer (VCM), 1,1-EDC, 1,2-dichloroethene (1,2-DCE) and ethyl chloride (EC) as well as dimerisation (butadiene) and aromatisation reactions (toluene), both with and without the presence of the Cu phase. The Cu phase was shown to contribute mainly to CO₂ and trichloroethane formation from 1,2-EDC via VCM. Co-promotion (K1.55La5.45Cu5.0) was found to enhance the activity of the Cu phase, and to mask acid sites on the alumina surface, thereby promoting ethene oxychlorination while at the same time hindering undesired conversion of the target product 1,2-EDC.     

Phase equilibria and stability of intermediate phases in the Sm2O3–BaO–Fe2O3 system

Phase equilibria in the ½ Sm₂O₃–BaO–½ Fe₂O₃ system were systematically studied at 1100°C in air. Two individual compounds: Sm_1.875Ba_3.125Fe₅O_15-δ and Ba₃SmFe₂O_7.5+δ have been detected in the studied system at 1100°C in air. One more complex oxide with double perovskite structure SmBaFe₂O_5+w has been obtained under reduced oxygen partial pressure. Thermodynamic stability of SmBaFe₂O_5+w and its thermal stability in metastable state in air were determined. The subsolidus phase diagram for the ½ Sm₂O₃ – BaO – ½ Fe₂O₃ system at 1100°C in air has been constructed.     

Glycerol Hydrogenolysis to 1,2-Propanediol by Cu/ZnO/Al2O3 Catalysts

The effect of preparation methods on the Cu/ZnO/Al₂O₃ catalyst structure and catalytic activity on liquid glycerol hydrogenolysis to 1,2-propanediol has been investigated. The physicochemical properties of the catalysts were characterized by BET, XRD, TG/DTA, NH₃-TPD and TPR. The experimental results showed that the catalyst prepared by an oxalate gel–coprecipitation had the highest activity. At 200 °C and 400 psi hydrogen pressure, the glycerol conversion and 1,2-propanediol selectivity catalyzed by the Cu/ZnO/Al₂O₃ catalyst prepared via oxalate gel–coprecipitation were 92.3 and 94.5 % respectively. It was found that the 1,2-propanediol selectivity was dependent on hydrogen pressure and the un-desired by-products were mainly due to the side reactions caused by the presence of the intermediate acetol.     

Modification of jute by acrylic acid in the presence of Na3PO4 and K2S2O8 as catalysts under thermal treatment

Jute fabric was modified using acrylic acid (AA) as the finishing agent in the presence of K₂S₂O₈ and Na₃PO₄ catalysts separately or in selected combinations, employing a pad–dry–cure technique. Treatment with 10% acrylic acid at 30°C and at pH 7 produced optimum effects: a batching time of 45–60 min at 30°C, followed by drying of the batched fabric at 95°C for 5 min and curing of the dried fabric at 140°C for 5 min produced most balanced improvements in the textile related properties. Na₃PO₄ catalyst allowed esterification of AA with cellulosic, hemicellulosic, and lignin constituents of jute, and K₂S₂O₈ catalyst allowed radical polymerization of free acrylic acid or jute-bound acrylic acid moieties; the said processes ultimately lead to some degree of crosslinking of the chain polymers of jute. Examination of the surface morphology of untreated and treated jute fabrics by scanning electron microscopy revealed a good degree of masking effect on the unit cells of jute and intercellular regions by a cohesive film of polyacrylic acid or its salts, particularly when K₂S₂O₈ was used either alone or in combination with Na₃PO₄ as catalyst. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 68:63–74, 1998     

Surface strengthening of Ti3SiC2 through magnetron sputtering of Mo and Zr and subsequent annealing

Magnetron sputtering deposition of Mo and Zr and subsequent annealing were conducted with the motivation to modify the surface hardness of Ti₃SiC₂. For Mo-coated Ti₃SiC₂, Si diffused outward into the Mo layer and reacted with Mo to form molybdenum silicides in the temperature range of 1000–1100 °C. The MoSi₂ layer, however, cracked and easily spalled off. For Zr-coated Ti₃SiC₂, Si also diffused outward to form Zr–Si intermetallic compounds at 900–1100 °C. The Zr–Si compounds layer had good adhesion with Ti₃SiC₂ substrate, which resulted in the increased surface hardness.     

Treatment of Volatile Organic Compounds with a Pt/Co3O4‐CeO2 Catalyst

For emission control of volatile organic compounds (VOC), e.g., in the painting and printing industries, conventional Pt/Al₂O₃ and Co₃O₄‐CeO₂ catalysts are used. On the Pt/Al₂O₃ catalyst, aromatic hydrocarbons containing a benzene ring such as toluene can be oxidized at a lower complete oxidation temperature than on Co₃O₄‐CeO₂, under typical treatment conditions. However, ethyl acetate and isopropyl alcohol can be oxidized at a lower complete oxidation temperature on Co₃O₄‐CeO₂ than on Pt/Al₂O₃. In this study, platinum was directly supported on Co₃O₄‐CeO₂. Using chloroplatinic acid, the platinum cohered and the catalytic activity did not improve. But when the platinum was supported using platinum colloid coated with dispersant, high‐dispersion support of the platinum on the Co₃O₄‐CeO₂ surface was achieved, and toluene, ethyl acetate, and isopropyl alcohol could be oxidized at less than 250 °C.     

Vapor Phase Ketonization of Acetic Acid on Ceria Based Metal Oxides

The activities of CeO₂, Mn₂O₃–CeO₂ and ZrO₂–CeO₂ were measured for acetic acid ketonization under reaction conditions relevant to pyrolysis vapor upgrading. We show that the catalyst ranking changed depending on the reaction conditions. Mn₂O₃–CeO₂ was the most active catalyst at 350 °C, while ZrO₂–CeO₂ was the most active catalyst at 450 °C. Under high CO₂ and steam concentration in the reactants, Mn₂O₃–CeO₂ was the most active catalyst at 350 and 450 °C. The binding energies of steam and CO₂ with the active phase were calculated to provide the insight into the tolerance of Mn₂O₃–CeO₂ to steam and CO₂.     

Optimization of the two-stage hydrotreatment for a coal liquid heavy distillate using some commercial catalysts at each stage

Catalytic up-grading of a coal liquid heavy distillate was examined using several commercial catalysts under variable conditions at hydrogen pressure of 150 atm (15.2 MPa). Some particular catalysts (Ni-Mo/Al₂O₃) exhibited much higher activities for denitrogenation in the two-stage hydrotreatment of 380°C for 3 h and 420°C for 3 h, although all Ni-Mo catalysts examined had similar activities for the cracking of paraffins in the distillate. Combinations of a Ni-Mo catalyst in the first stage (380°C for 3 h) with a silica-alumina or with a Co-Mo/Al₂O₃ in the second stage (420°C for 3 h) exhibited the highest activities for paraffin cracking (conversion 61%) or denitrogenation (96% removal), respectively. By optimization of the two-stage hydrotreatment, especially in terms of catalyst combination and reaction temperature, the total reaction time could be reduced to a practically acceptable one (3 h) by achieving satisfactory levels of paraffin cracking and denitrogenation.     

Direct Conversion of Glycerol into 1,3-Propanediol over Cu-H4SiW12O40/SiO2 in Vapor Phase

Using a SiO₂ supported copper and H₄SiW₁₂O₄₀ catalyst, it is demonstrated that glycerol can be directly converted to 1,3-Propanediol (1,3-PD) through vapor-phase process under pressure below 0.54 MPa, without employing environmentally harmful organic solvent. The formation of 1,3-PD is proved to proceed through the designed reaction pathway: (step 1) dehydration of glycerol to 3-hydroxypropanal on acid site of supported H₄SiW₁₂O₄₀ (step 2) hydrogenation of 3-hydroxypropanal on supported copper metal. The effect of temperature, weight hourly space velocity, pressure, and initial water content was investigated to obtain the optimum conditions. The glycerol conversion and products distribution greatly depended on these factors. Both the 1,3-PD and 1,2-Propanediol selectivity improved with increasing hydrogen pressure. At 210 °C, 0.54 MPa and 83.4% conversion, the selectivity of 1,3-PD was up to 32.1%, together with a 22.2% selectivity of 1,2-Propanediol. The cyclic acetal, an important kind of byproducts, was identified by Gas Chromatogram–Mass Spectrometer (GC–MS).     

Hot corrosion behavior of V2O5-coated Gd2Zr2O7 ceramic in air at 700–850 °C

Gd₂Zr₂O₇ ceramic was prepared by solid state reaction at 1650 °C for 10 h in air, and exhibited a defect fluorite-type structure. Reaction between molten V₂O₅ and Gd₂Zr₂O₇ ceramic was investigated at temperatures ranging from 700 to 850 °C using an X-ray diffractometer (XRD) and scanning electron microscopy (SEM). Molten V₂O₅ reacted with Gd₂Zr₂O₇ to form ZrV₂O₇ and GdVO₄ at 700 °C; however, in a temperature range of 750–850 °C, molten V₂O₅ reacted with Gd₂Zr₂O₇ to form GdVO₄ and m-ZrO₂. Two different reactions observed at 700 °C and 750–850 °C could be explained based on the thermal instability of ZrV₂O₇.