State of platinum in zirconia and sulfated zirconia catalysts

Platinum is present in a metallic state following activation in air at 725C of both 5 wt% Pt/ZrO₂ and 5 wt% Pt/SO ₄ ^2– /ZrO₂. Reduction of either catalyst at 725C produces a Pt-Zr alloy, and these reduced catalysts, upon recalcination in air at 725C, form metallic Pt crystallites. Likewise, reduction of these uncalcined catalysts at 725C in H₂ leads to a Pt-Zr alloy formation. However, treatment of these uncalcined catalysts in H₂ at 450C does not produce Pt crystallites large enough to detect by XRD.     

Catalytic behaviour and characterisation of CuO1−z(La2O3)z/2 based catalysts deposited on γ-Al2O3 and prepared in situ with 0.0 ⩽z⩽1.00, without and with addition of Pd

(CuO)_1–z(La₂O₃)_z/2 based catalysts with 0.0z1.0 supported on -Al₂O₃ have been prepared in situ and the phases formed have been identified by XRD, SEM and TEM/EDS studies. The catalyst with z=0.5 exhibited the best catalytic activity for oxidation of CO (T ₅₀=295 and 390C with degrees of conversions of 93 and 92% at 450C under rich and lean conditions, respectively) and C₃H₆ (291 and 414C; 93 and 83%) and reduction of NO (405C; 60 and 0%). This catalyst contained appreciable amounts of the perovskite phase LaAl_1–xCu_xO₃ and the enhanced catalytic properties are ascribed to the presence of this phase. Addition of Pd to this catalyst implied that the degree of conversion of NO increased and that the light-off temperatures for all involved gas species decreased. Ageing experiments revealed that LaAl_1–xCu_xO₃ decomposed and that Cu containing Pd particles were formed during this procedure which in turn deteriorated the catalytic properties of the catalyst.     

Catalytic decomposition of nitrous oxide on strontium-substituted La2CuO4 materials

Catalytic decomposition of nitrous oxide (N₂O) to N₂ and O₂ has been studied on a series of solid oxide solutions of La, Sr and Cu according to the nominal formula La_2–x Sr _x CuO₄ (0x1). The reaction has been carried out in a fixed bed, glass static reactor with gas-recirculation facility. The kinetics of decomposition has been studied in the temperature range 250–480C. Among the catalysts studied,x=0.15 andx=1.0 showed higher catalytic activity (in terms of %conversion). The enhanced activity of the above systems has been explained on the basis of mixed valency of copper (Cu²⁺/Cu³⁺) and anion vacancies respectively.     

Hydroxylation of phenol with H2O2 over transition metal containing nano-sized hollow core mesoporous shell carbon catalyst

The catalytic performance of transition metal (Fe²⁺ or Cu²⁺) containing nano-sized hol low core mesoporous shell carbon (HCMSC) heterogeneous catalysts for the hydroxylation of phenol with hydrogen peroxide (H₂O₂) in water was investigated in a batch reactor. The metal-containing HCMSC catalyst showed higher activity than the same metal ion-exchanged zeolites. The nature of the metal and its content in the HCMSC had remarkable influence on the reaction results under the typical reaction conditions (PhOH/H₂O₂=3, reaction temperature=60 ‡C). Fe²⁺ containing HCMSC catalyst showed high catalytic activity with phenol conversion of 29%, selectivity to catechol (CAT) and hydroquinone (HQ) about 85%, H₂O₂ effective conversion about 70% and selectivity to benzoquinone (BQ) below 1% in the batch system.     

Phenol alkylation with methanol: effect of sodium content and ammonia selective poisoning of an HY zeolite

Sodium exchange and ammonia selective poisoning of the acid sites of an HY zeolite (Si/Al=20) were carried out and their effects on the catalytic properties for the alkylation of phenol with methanol (200C, 1 atm and N₂/reactants molar ratio of 4) were evaluated. Results show that the reaction is highly sensitive to the number and strength of the acid sites of the catalyst. A decrease in the number of acid sites by sodium exchange of the protons or by ammonia selective poisoning produces important changes in the selectivity of the reaction. In fact, a high increase in the anisole/cresol ratio is observed as the percentage of exchanged sodium in the zeolite increases, while the ammonia selective poisoning shows that at low desorption temperatures (250C) only anisole is formed while at higher desorption temperatures both anisole and cresols were observed. These results show that anisole formation requires sites with lower acid strength compared to those necessary for cresol formation.     

Spalling resistance of corundum refractories

Conclusions Refractories based on electromelted corundum with an alumina binder are marked by comparatively low spalling resistance. The refractoriness-under-load of 2 kg/cm² is above 1800.The replacement of the alumina binder in these refractories by 10 – 20% kaolin, which causes crystallization of the mullite, helps to improve the spalling resistance. But the softening point here is reduced to 1700.Replacement of the fine-grain electro-melted corundum by finely dispersed alumina promotes active crystallization of the mullite and is accompanied by a further increase in the spalling resistance. The softening point remains low (1670).     

Initial activity/selectivity of H-gallosilicate (MFI) in propane aromatization: influence of H+ exchange and thermal/hydrothermal pretreatments

Initial activity/selectivity of H-gallosilicate (MFI) zeolite with different degrees of H⁺ exchange and pretreated under different thermal and hydrothermal conditions in propane aromatization (at 500C) has been determined using a pulse microreactor connected to GC. It is found to be strongly influenced by the degree of H⁺ exchange, calcination temperature and hydrothermal treatment at different temperatures and concentrations of steam. There exists a close relationship between the acidity (measured in terms of pyridine chemisorbed at 400 C) of the gallosilicate and its initial propane conversion and aromatization activity. Presence of strong acidic sites (attributed to FW Ga) at high concentration is essential for the well dispersed non-FW Ga oxide species to be active for dehydrogenation in the propane aromatization over the zeolite.     

Effect of acid/hydrocarbon ratio,temperature and contact time on the isobutane-isobutylene alkylation with trifluoromethanesulfonic acid

The effect of the acid-hydrocarbon ratio and temperature on the isobutane-isobutylene alkylation with trifluoromethanesulfonic acid was studied over the temperature range of 40CT–80C. The effect of acid/hydrocarbon ratios and temperature passes through a maximum giving high quality alkylate of approximately 70% branched C₈ products at –30C, with a catalyst/hydrocarbon ratio of 0.5. The optimum reaction conditions also depend on the induction period and the effect of secondary reactions influenced by contact time. TFSA is a readily recyclable acid without the need for any purification or regeneration.     

Production of BL-0.5 lightweight brick with combustible additives

Conclusions Lightweight brick with a bulk density of 0.5 g/cm² made with combustible additives is an effective refractory insulating material and can be used for purposes of insulation at 1000 – 1200.The use of BL-0.5 lightweight refractory for insulating blast furnace blowpipes at a blast temperature of 930 – 950, apart from preserving the ends of the blowpipe and saving heat, creates better conditions for servicing the furnace in the tuyere zone.     

Highly active polymer-alumina dually supported palladium catalysts for the carbonylation of allyl halides under atmospheric pressure

Polymer-alumina dually supported palladium catalysts (PVP-Pd/Al₂O₃, PVP = poly(N-vinyl-2-pyrrolidone); PPPO-Pd/ Al₂O₃, PPPO = phosphinated poly(phenylene oxide)) were used to catalyze the carbonylation of allyl halides to form butenoic acid under the mild conditions of 40C and 0.1 MPa. These catalysts exhibit high activity and stability towards the carbonylation of allyl halides. The maximum turnovers (mol CO/mol Pd) of PPPO-Pd/Al₂O₃ are up to 8.2×10⁵ and 4.6×10⁵ for the carbonylation of allyl bromide and allyl chloride respectively in an aqueous NaOH/benzene medium.     

Reduction of NO by H2 and CO on Pt/TiO2/SiO2

Different catalysts based on platinum and a silica, titania or mixed titania/silica support were studied in NO reduction reactions by CO and H₂ in the temperature range of 25–400C. The mixed oxide catalysts showed considerably lower onset temperatures in NO/CO reactions but this coincided with a maximum in N₂O formation. In NO/H₂ reactions all titania containing catalysts produced more N₂O than silica supported platinum at low temperatures but were more selective to N₂ at high temperatures.     

Cr2O3/SiO2催化苯酚与碳酸二乙酯邻位烷基化反应

以Cr(NO₃)₃?9H₂O为前体,采用等体积浸渍法制备了一系列不同Cr₂O₃负载量的Cr₂O₃/SiO₂催化剂;在固定床连续微反装置上,考察了Cr₂O₃/SiO₂催化剂对苯酚与碳酸二乙酯邻位烷基化反应的催化性能;采用XRD、NH₃-TPD、CO₂-TPD和吡啶吸附、红外等手段对催化剂进行了表征。实验结果表明,随着Cr₂O₃负载量的增加,苯酚的转化率和邻乙基苯酚的选择性均逐渐增加;当Cr₂O₃负载量达到7.5%时,苯酚的转化率和邻乙基苯酚的选择性均达到最大值,分别为48%和67%。催化剂的表征结果表明,L酸中心是苯酚邻位烷基化反应的活性中心,苯酚转化率和邻乙基苯酚选择性的变化主要是由催化剂的酸、碱中心数目变化引起的。     

Low temperature,efficient synthesis of new As(V)-silicate molecular sieves with MFI topology and their catalytic properties in oxidation reactions

New MFI type arseno-silicate molecular sieves (As(V)-MFI), synthesized for the first time, can be crystallized at lower temperature (70–90C) in 1–3 days under hydrothermal conditions. Interestingly, these As(V)-MFI molecular sieves can be synthesized even faster than the As-free silicalite-1 under identical conditions. Further, the crystallization becomes faster with the increase in As content of the reaction mixture, contrary to the observations made on all the other high silica molecular sieves, so far. These microporous As(V)-silicates exhibit significant catalytic activity in (i) phenol hydroxylation using 30% aq. H₂O₂ (ca. 55% H₂O₂ efficiency) and (ii) oxidative dehydrogenation of 2-butanol and benzyl alcohol using air under fixed bed vapor phase reaction conditions exhibiting ca. 75–85% selectivity towards 2-butanone and benzaldehyde+benzoic acid, respectively.     

Steam Reforming of Methanol Over Cu/CeO2 Catalysts Studied in Comparison with Cu/ZnO and Cu/Zn(Al)O Catalysts

A series of Ce_1-xCu_xO_2- mixed oxides were synthesized using a co-precipitation method and tested as catalysts for the steam reforming of methanol. XRD patterns of the Ce_1-xCu_xO_2- mixed oxides indicated that Cu²⁺ ions were dissolved in CeO₂ lattices to form a solid solution by calcination at 773K when x < 0.2. A TPR (temperature-programmed reduction) investigation showed that the CeO₂ promotes the reduction of the Cu²⁺ species. Two reduction peaks were observed in the TPR profiles, which suggested that there were two different Cu²⁺ species in the Ce_1-xCu_xO_2- mixed oxides. The TPR peak at low temperature is attributed to the bulk Cu²⁺ species which dissolved into the CeO₂ lattices, and the peak at high temperature is due to the CuO species dispersed on the surface of CeO₂. The Ce_1-xCu_xO_2- mixed oxides were reduced to form Cu/CeO₂ catalysts for steam reforming of methanol, and were compared with Cu/ZnO, Cu/Zn(Al)O and Cu/AL₂O₃ catalysts. All the Cu-containing catalysts tested in this study showed high selectivities to CO₂ (over 97%) and H₂. A 3.8wt% Cu/CeO₂ catalyst showed a conversion of 53.9% for the steam reforming of methanol at 513K (W/F = 4.9 g h mol^-1), which was higher than that over Cu/ZnO (37.9%), Cu/Zn(Al)O (32.3%) and Cu/AL₂O₃ (11.2%) with the same Cu loading under the same reaction conditions. It is likely that the high activity of the Cu/CeO₂ catalysts may be due to the highly dispersed Cu metal particles and the strong metalsupport interaction between the Cu metal and CeO₂ support. Slow deactivations were observed over the 3.8wt% Cu/CeO₂ catalyst at 493 and 513K. The activity of the deactivated catalysts can be regenerated by calcination in air at 773K followed by reduction in H₂ at 673K, which indicated that a carbonaceous deposit on the catalyst surface caused the catalyst deactivation. Using the TPO (temperature-programmed oxidation) method, the amounts of coke on the 3.8wt% Cu/CeO₂ catalyst were 0.8wt% at 493K and 1.7wt% at 513K after 24h on stream.     

Life of silicon carbide heaters in argon at high temperatures

Conclusions The electrical heating elements made from silicon carbide in argon age slowly and may operate for more than 300 h at a temperature on the surface of 1700C and more than 200 h at 1800C.The service life of the heating elements made from silicon carbide at 2000C in argon is less by a factor of 20 than at 1800C. At 2000C sublimation of the SiC from the heating element is observed.The presence in the argon atmosphere of up to 11% oxygen does not have a marked influence on the rate of oxidation of the heating elements at 1600C at the surface.Translated from Ogneupory, No. 3, pp. 33–36, March, 1967.     

Effect of Rare Earth Doping on the Catalytic Activity of Copper‐Containing Hydrotalcites in Phenol Hydroxylation

The copper‐containing hydrotalcites (Cu‐HTLcs) are synthesized under microwave irradiation, the effect of rare earth elements (RE) on the synthesis of Cu‐HTLcs, wherein RE stands for rare earth elements, e.g., La, Y, Sm and Ce, is also investigated in the present work. The hydrotalcite structure of the synthesized samples is verified by XRD and FT‐IR. The results of their catalytic performances in phenol hydroxylation show that the doped rare earth elements can promote the catalytic activity of Cu‐HTLcs, exhibiting a good trend as follows: La>Y>Sm>Ce. XPS results show that the Cu⁺ species are produced after the interaction of La‐Cu‐HTLcs with H₂O₂. Combining with the catalytic test results, we propose a new mechanism about the generation of HO ^. radicals in phenol hydroxylation, it is assumed that HO‐Cu⁺‐OH species are first formed by the reduction of HO‐Cu²⁺‐OH located in hydrotalcites in the presence of H₂O₂, and then react with H₂O₂ to give rise to HO^. radicals.     

Excess molar enthalpies of ternary and constituent binary systems {1,2-dichloropropane+2-propanol+2-butanol} at T=298.15 K

Ternary excess molar enthalpies at T=298.15 K and P=101.3 kPa for the system of {1,2-dichloropropane+2-propanol+2-butanol} and their constituent binary systems {1,2-DCP+2-propanol}, {1,2-DCP+2-butanol}, and {2-propanol+2-butanol} have been measured over the whole composition range using an isothermal micro-calorimeter with flow-mixing cell. All of the binary and ternary systems, including three pseudobinary systems, show endothermic behavior except for the binary mixture {2-propanol+2-butanol}, which shows small exothermicity. The Redlich-Kister equation was used to correlate the binary H _{m, ij} ^E data, and the Morris equation to correlate the ternary H _{m, 123} ^E data. Comparisons between the Morris and Radojkovi equations for the prediction of H _m,123 ^E have been also made. The experimental results have been qualitatively discussed in terms of self-association, isomeric effect and chain length among molecules.     

Crystal structure and size distribution of Pt-Cu-Fe alloy clusters supported on carbon black

Carbon supported alloy electrocatalysts based on Pt, Cu and Fe (atomic ratios PtCuFe=211 and 611) are prepared at various alloying temperatures and are characterized by XRD and TEM techniques. Powder XRD analyses show that Pt₆CuFe clusters form a face-centered cubic structure (AuCu₃ type), while Pt₂CuFe clusters form an ordered alloy with a facecentered tetragonal structure (AuCu type) at higher temperature than 700C. Transmission electron micrographs reveal that the size of metal clusters increases gradually and size distribution becomes broader, as alloying temperature increases from 500 to 1100C.     

Density, ultrasonic velocity, viscosity and their excess parameters of the binary mixtures of N,N-dimethylaniline+1-alkanols (C3-C5), +2-alkanols (C3-C4), +2-methyl-1-propanol, +2-methyl-2-propanol at 303.15K

The density, ultrasonic velocity of sound and viscosity of binary mixtures of N,N-dimethyl aniline (N,NDMA) with 1-propanol, +2-propanol, +1-butanol, +2-butanol, +1-pentanol, +2-methyl-1-propanol, +2-methyl-2-propanol were measured at 303.15 K. These experimental data have been used to calculate excess volume V ^E , excess ultrasonic speeds u ^E , excess intermolecular free length L _f ^E , excess acoustic impedance Z ^E , excess isentropic compressibility κ _s ^E , deviation in viscosity Δη and excess Gibbs free energy of activation of viscous flow (G* ^E ). The values of L _f ^E and κ _s ^E are negative over the wide range of composition for all the binary mixtures, while the values of Z ^E are positive. These results have been used to discuss the nature of interaction between unlike molecules in terms of hydrogen bonding, dipole-dipole interaction, proton-acceptor interaction and dispersive forces. The viscosity data have been correlated using three equations: Grunberg and Nissan, Katti & Chaudhri and Hind et al. The excess/deviations were fitted by a Redlich-Kister equation and the results were analyzed in terms of specific interactions present in these mixtures.     

CO and NO adsorption on copper-containing zeolite. A theoretical ab initio study

Ab initio calculations were performed to simulate the interaction between CO or NO and copper-containing zeolite at the SCF level. The zeolite catalysts were modelled by a molecular cluster of composition H₈Si₃AlO₄Cu⁺ with = 0, 1. For = 0 the oxidation state of the Cu atom corresponds to 1+ in Cu⁺/zeolite, while for° = 1 it is equal to 2+ in Cu²⁺/zeolite. It was found that only Cu⁺/zeolite should be responsible for CO and NO adsorption from the gas phase. The calculated heats of adsorption compare well with available experimental data and together with adsorption geometries allow us to interpret the observed IR data.