Mixed Oxides

Heat capacity and enthalpy increments of ternary strontium bismuth(III) oxides SrBi 2 O 4 and Sr 2 Bi 2 O 5 were measured by the relaxation time method (2–210 K), DSC (253–352 K) and drop calorimetry (570–1072 K). Temperature dependencies of the molar heat capacity in the form C pm = 161.97 + 45.936 × 10 −3 T – 1.7862 × 10 6 /T 2 J K −1 mol −1 and C pm = 197.48 + 87.463 × 10 −3 T – 1.9282 × 10 6 /T 2 J K −1 mol −1 for SrBi 2 O 4 and Sr 2 Bi 2 O 5 , respectively, were derived by the least-squares method from the experimental data. The molar entropies at 298.15 K, S • m (298.15 K) = 206.1 ± 1.1 J K −1 mol −1 for SrBi 2 O 4 and S • m (298.15 K) = 261.2 ± 1.4 J K −1 mol −1 for Sr 2 Bi 2 O 5 , were evaluated from the low temperature heat capacity measurements.

Hydrodesulfurization (HDS) and Hydrodearomatization (HDA) of a real Straight Run Gas Oil (SRGO) were investigated over CoMo-S sulfide catalyst in a high-pressure fixed-bed integral reactor. The effect of the key process parameters on the quality of product was studied by varying the temperature (200-370oC), pressure (20 to 50 bar) and space velocity (1 to 4.7h-1). Experimental results revealed that HDS,% activity improved up to 81% when the temperature was
increased up to 370oC but reduced to 60% with increase of space velocity up to 4.7 h-1. It has been also found that the rate of HDA, % activity enhanced up to 40.6% by increasing pressure up to 50 bar. The Cetane index underwent an increase of 1-3 degrees and gravity increased by 1-1.7 oAPI.
The implication of these results on refining industry is that mild hydrotreating of diesel fuels using the single-stage technology will not enable local refineries to produce diesel fuel meeting the current specifications (<15 ppmwt) except with severe/deep once-through desulfurization or two stage once- through desulfurization with or without splitting the first reactor effluent.

^Äëíê~ÅíK Hydrodesulfurization (HDS) and Hydrodearomatization (HDA) of a real Straight Run Gas Oil (SRGO) were investigated over CoMo-S sulfide catalyst in a high-pressure fixed-bed integral reactor. The effect of the key process parameters on the quality of product was studied by varying the temperature (200-370 o C), pressure (20 to 50 bar) and space velocity (1 to 4.7h -1 ). Experimental results revealed that HDS,% activity improved up to 81% when the temperature was increased up to 370 o C but reduced to 60% with increase of space velocity up to 4.7 h -1 . It has been also found that the rate of HDA, % activity enhanced up to 40.6% by increasing pressure up to 50 bar. The Cetane index underwent an increase of 1-3 degrees and gravity increased by 1-1.7 o API. The implication of these results on refining industry is that mild hydrotreating of diesel fuels using the single-stage technology will not enable local refineries to produce diesel fuel meeting the current specifications (<15 ppmwt) except with severe/deep once-through desulfurization or twostage once-through desulfurization with or without splitting the first reactor effluent. = hÉóïçêÇëW Diesel fuel; hydrodesulfurization; hydrodearomatization; CoMo-S/ Al2O3 catalyst =^Ä ëíê~âK Penyahsulfuranhidro (dirujuk sebagai HDS) dan penyaharomatikanhidro (dirujuk sebagai HDA) bagi Minyak Mentah Ringan telah dijalankan menggunakan pemangkin sulfida CoMo-S di dalam reaktor integral mangkin padat bertekanan tinggi. Kesan daripada parameterparameter proses utama terhadap kualiti produk telah dikaji dengan mempelbagaikan suhu (200-370 o C), tekanan (20 ke 50 bar) dan halaju ruang (1 hingga 4.7 h -1 ). Keputusan eksperimen menunjukkan, % aktiviti HDS dipertingkatkan sehingga 81% apabila suhu dinaikkan sehingga 370 o C tetapi berkurang sehingga 60% dengan pertambahan halaju ruang sehingga 4.7 h -1 . Selain itu, keputusan juga menunjukkan bahawa kadar % aktiviti HDA dipertingkatkan sehingga 40.6% apabila tekanan dinaikkan hingga mencecah 50 bar. Indeks setana menunjukkan peningkatan 1&2

Reactions of phenol and methanol catalyzed by MgO have been explored by kinetic measurements and in situ IR spectroscopy combined with computational studies of sorbed molecules. On MgO, methanol partly transforms to formaldehyde above 250°C. Adsorbed phenol forms phenolate species, and the energetically preferred mode of adsorption leads to an almost orthogonal orientation of the aromatic ring with respect to the catalyst surface. All molecules involved adsorb preferably at the corner sites of MgO (three-co-ordinated Mg atoms). The main reaction products are anisole and o-cresol, the latter dominating above 300°C. At very low conversions, salicylic aldehyde is observed as primary reaction product, being rapidly transformed to o-cresol. It is only observed during the initial accumulation of adsorbed species on the catalyst surface, but not under steady-state conditions on a fully covered catalyst surface. Therefore, o-cresol formation starts with the reaction between phenol and formaldehyde to salicylic alcohol, which in turn is rapidly transformed to salicylic aldehyde and subsequently to o-cresol. Salicylic aldehyde may also form via the bimolecular disproportionation of salicylic alcohol to o-cresol and aldehyde. The parallel reaction to o-cresol, not involving the formation of salicylic aldehyde as intermediate, proceeds via the reduction of salicylic alcohol to o-cresol by formaldehyde. The identified mechanism may open new synthetic approaches for the production of functionalized phenol derivatives and, even more importantly, for the defunctionalization of substituted phenols potentially available at large scale from deconstructed lignin.

The biorelated degradability and clearance of siliceous nanomaterials have
been questioned worldwide, since they are crucial prerequisites for the
successful translation in clinics. Typically, the degradability and
biocompatibility of mesoporous silica nanoparticles (MSNs) have been an
ongoing discussion in research circles. The reason for such a concern is
that approved pharmaceutical products must not accumulate in the human
body, to prevent severe and unpredictable side-effects. Here, the biorelated
degradability and clearance of silicon and silica nanoparticles (NPs) are
comprehensively summarized. The influence of the size, morphology, surface
area, pore size, and surface functional groups, to name a few, on the
degradability of silicon and silica NPs is described. The noncovalent organic
doping of silica and the covalent incorporation of either hydrolytically stable
or redox- and enzymatically cleavable silsesquioxanes is then described for
organosilica, bridged silsesquioxane (BS), and periodic mesoporous organosilica
(PMO) NPs. Inorganically doped silica particles such as calcium-,
iron-, manganese-, and zirconium-doped NPs, also have radically different
hydrolytic stabilities. To conclude, the degradability and clearance timelines
of various siliceous nanomaterials are compared and it is highlighted that
researchers can select a specific nanomaterial in this large family according to
the targeted applications and the required clearance kinetics.

Mixed oxides with large surface area and high thermal stability can be obtained by thermal treatment of the layered double hydroxides (LDH). Mg-Al-Fe mixed oxide samples with varying Mg/Al ratio and 5 mol.% of Fe were prepared in this way and the iron oxidation state (Fe ox ) in these compounds was studied by X-ray photoelectron spectroscopy (XPS), using a calibration based on the relation of Fe ox to the splitting between the O 1s and Fe 2p 3/2 centroids. The XPS results confirm Fe 3+ as a dominant oxidation state in the studied mixed oxides. A vacuum-induced reduction of iron in the Fe 2 O 3 and Mg-Al-Fe oxide samples has been observed and an influence of the Mg:Al ratio on this effect in mixed oxides has been detected. The role of the local variations of the electron density distribution in the close neighbourhood of the surface oxygen atoms in the mixed oxides in the reduction processes is discussed. #

A B S T R A C T The present study addresses the synthesis of manganese-nickel oxide thin films via potentiodynamic anodic electrodeposition as supercapacitor electrodes. We study in particular the effect of the deposition scan rate and of the Ni(II) to Mn(II) molar ratio in the deposition bath on the capacitive behaviour of mixed oxide electrodes. The increase of the nickel content in oxide thin films of composition Ni x Mn 1-x O y (with x in the range from 0 to 0.17) results in the increase of specific capacitance up to a maximum for about 10 at% Ni. The deposition scan rate affects the capacitive behaviour of mixed oxide electrodes through its effects on layer morphology and surface structure. In particular, thin film electrodes at about 10 at% Ni show a maximum in the specific capacitance for deposition scan rate of 600 mV s À1 , which is shown to be related to the attendant modifications in surface morphology and topography. After annealing at 200 C, 6 h, partial crystallization of the amorphous structure of the as-grown mixed oxide takes place with formation of dispersed nanocrystalline domains. The annealed electrode at 10 at% Ni, with mass loading of 0.30 mg cm À2 , show the highest specific capacitance (250 F g À1 , at 0.1 A g À1), and specific energy and power as high as 34.5 Wh kg À1 (at 50 W kg À1), and 4.3 kW kg À1 (at 15.7 Wh kg À1). Mixed oxide of the same composition and mass loading reveal a 122% capacitance retention after 10,000 cycles in 1 M Na 2 SO 4 at 20 A g À1 .

Water splitting using sunlight is an important process for future energy supplies. TiO2 is widely used as photoanode, but has a limited light absorption range. Here, ternary Ti–Mo–Ni mixed oxide nanotube arrays were fabricated via electrochemical anodization of Ti–Mo–Ni alloy in formamide-ethylene glycol-based electrolytes, to extend the absorption range into visible light. The electrolyte composition and anodization time were found crucial in controlling the structural features of the nanotubes. By tuning these parameters, arrays of thin walled (∼9 nm) and ∼8 μm long nanotubes were obtained. In photoelectrochemical water splitting, the mixed oxides showed incident photon conversion efficiency (IPCE) up to 65% for wavelengths from 300 nm to 450 nm. This enhancement in the IPCE of the mixed oxide nanotubes, compared with pure titania, can be related to synergistic effects of Mo and Ni oxides as well as to the unique structural properties of the fabricated mixed oxide nanotubes.

Nano Co 3 O 4-CuO-ZrO 2 mixed oxides were synthesized by wet chemical method by mixing of equimolar solutions of cobalt chloride, copper sulphate and zirconium oxychloride in aqueous sodium hydroxide and refluxed at elevated temperature. The prepared mixed nano oxides were characterized by FT-IR, XRD, UV-DRS, TEM, SAED, SEM, EDAX and AFM. The FTIR spectra exposed the presence of M-O bonds (M = Co, Cu, Zr). From XRD studies, the size of the Co 3 O 4-CuO-ZrO 2 NPs are found to be 12.93-23.83nm through Scherrer's formula. The XRD patterns also reveal that the nanoparticle size is drastically increased with increasing concentration of the precursors. From UV-Vis diffuse reflectance spectra (DRS), band gap energy of the (0.1-0.5M) Co 3 O 4-CuO-ZrO 2 NPs are found to be in the range of 3.13-3.24eV. The TEM, SEM and AFM micrographs of 0.1MCo 3 O 4-CuO-ZrO 2 NPs display irregular shape with size ranging from 10-40nm. SAED pattern confirms the crystalline nature of these nanoparticles. EDAX analysis indicates the presence of Co, Cu, Zr and O.

Vapor phase nitration of benzene has been carried out, using dilute nitric acid as the nitrating agent, over Fe/Mo/SiO 2 solid acid catalyst with more than 80% benzene conversion and 99% selectivity for mononitrobenzene. A series of Fe/Mo/SiO 2 catalysts with various compositions were prepared using a sol-gel technique and characterized using X-ray diffraction analysis (XRD), BET specific surface area analysis, temperature-programmed desorption (TPD) of ammonia, and FTIR spectroscopic analysis of adsorbed pyridine. The results are correlated with structure and acidity of the catalysts.

Some empirical methods for the estimation of standard molar heat capacity (C pm) of solid mixed oxides are reviewed and the reliability of the obtained data in phase equilibria calculations is examined. Following the comparison of predicted values of C pm (298.15 K) with more than 300 experimental data the most widely used Neumann±Kopp rule (NKR) is found to be very universal but in some cases the mean deviation of 3.3% is too high, giving rise to a relatively large error in equilibrium calculation results. On the other hand, the method based on binary oxide contributions proposed by Berman and Brown [Contrib. Mineral. Petrol. 89 (1985) 168] for the estimation of temperature dependencies C pm (T) of silicates and other minerals formed by is less general, but more accurate. In comparison with the NKR, the most pronounced drawback of this method is the necessity to know the experimental values of C pm for a set of mixed oxides, so that the individual contributions of constituent binary oxides can be evaluated.

Vapor phase nitration of benzene has been carried out, using dilute nitric acid as the nitrating agent, over Fe/Mo/SiO 2 solid acid catalyst with more than 80% benzene conversion and 99% selectivity for mononitrobenzene. A series of Fe/Mo/SiO 2 catalysts with various compositions were prepared using a sol-gel technique and characterized using X-ray diffraction analysis (XRD), BET specific surface area analysis, temperature-programmed desorption (TPD) of ammonia, and FTIR spectroscopic analysis of adsorbed pyridine. The results are correlated with structure and acidity of the catalysts.

The performance of Ti0.3W0.7 and Nb thin films as diffusion barriers for Au was investigated by Rutherford Backscattering Spectrometry (RBS) and Auger Electron Spectroscopy(AES). The films were sputter deposited in Ar:N2 (70:30 vol%) or pure Ar on amorphous SiO2. They were annealed in air at temperatures ranging from 250 °C up to 750 °C for several hours. In‐depth profiles revealed an onset of oxidation of the barriers at 520 °C for Nb and about 600 °C for TiW. Barrier oxidation and extensive diffusion could be correlated. Distinct diffusion behavior as a function of temperature was established between TiW and Nb. A Nb multilayer structure was found to provide the best reliability as the barrier and as the adhesion layer.

© 1984 American Vacuum Society
Received 15 September 1983 Accepted 31 October 1983
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Silica-supported binary and ternary phosphides, MoP/SiO 2 , Ni 2 P/SiO 2 , and Ni-Mo-P/SiO 2 have been prepared and characterized by X-ray diffraction (XRD), BET surface area, CO chemisorption, transmission electron microscopy (TEM), and infrared spectroscopy (IR). The hydrodesulfurization (HDS) activities of dibenzothiophene (DBT) were measured and compared at 593 K and 3.0 MPa for MoP/SiO 2 , Ni 2 P/SiO 2 , and Ni-Mo-P/SiO 2 catalysts with different Mo and Ni loadings. The activities of the phosphides follow the order Ni 2 P/SiO 2 > Ni-Mo-P/SiO 2 > MoP/SiO 2 . The Ni sites in the Ni-Mo-P/SiO 2 catalysts play a major role in the conversion of DBT, and the activity of the catalysts increases with increasing Ni content. This is different from sulfides, nitrides, and carbides, as no synergetic effect is observed between the phosphided Ni and the Mo atoms. The surface of these phosphide catalysts is partially sulfided forming a surface phosphosulfide phase, while the bulk structure of the phosphides is maintained in the HDS reactions.