Biodiesel production by the transesterification of cottonseed oil by solid acid catalysts

Methyl esters (biodiesel) were produced by the transesterification of cottonseed oil with methanol in the presence of solid acids as heterogeneous catalysts. The solid acids were prepared by mounting H₂SO₄ on TiO₂ · nH₂O and Zr(OH)₄, respectively, followed by calcining at 823K. TiO₂-SO₄ ²⁻ and ZrO₂-SO₄ ²⁻ showed high activity for the transesterification. The yield of methyl esters was over 90% under the conditions of 230°C, methanol/oil mole ratio of 12:1, reaction time 8 h and catalyst amount (catalyst/oil) of 2% (w). The solid acid catalysts showed more better adaptability than solid base catalysts when the oil has high acidity. IR spectral analysis of absorbed pyridine on the samples showed that there were Lewis and Br?nsted acid sites on the catalysts. Translated from The Chinese Journal of Process Engineering, 2006, 6(4): 571–575 [译自: 过程工程学报]     

Infrared spectroscopy and microcalorimetry studies of CO adsorption on sulfated zirconia supported platinum catalysts

Carbon monoxide adsorption has been investigated on Pt particles supported on a high surface area zirconia and sulfated zirconias. The accessibility of the Pt surface determined from the comparison of H₂ chemisorption and transmission electron microscopy depends on two parameters: the temperature of treatment in air used to dehydroxylate sulfated zirconia, and the temperature of reduction. An oxidative pretreatment at 823 K yields a poor accessibility of Pt (0.03 < H/Pt < 0.05) whatever the temperature of reduction, whereas a Pt dispersion of 0.6 can be obtained by oxidation at 673 K followed by a mild reduction at 473 K. FTIR spectroscopy of adsorbed CO on Pt/ZrO₂ shows besides the normal linear species at 2065 cm^–1, a band at 1650 cm^–1 which is attributed to CO bridged between Pt and Zr atoms. On Pt/ZrO₂-SO ₄ ^2– , all bridged species tend to disappear, as well as the dipole-dipole coupling andv _CO is shifted by 57 cm^–1 to higher frequencies. These results are attributed to sulfur adsorption on Pt which decreases the electron back-donation from Pt to the 2 ^* antibonding orbital of CO. The lower initial heat of CO adsorption observed on Pt/ZrO₂-SO^4/2– supports this proposal.     

Low-temperature catalytic combustion on Pt/SO 4 2− /ZrO2 and Pd/SO 4 2− /ZrO2 catalysts

Low-temperature combustion of various organic compounds on Pt/SO ₄ ^–2 /ZrO₂ and Pd/SO ₄ ^–2 /ZrO₂ was studied. For these organic compounds, especially saturated hydrocarbons, the combustion activities of Pt/SO ₄ ^–2 /ZrO₂ are higher than those of Pt/ Al₂O₃. Pt/SO ₄ ^–2 /ZrO₂ combustion catalysts can be used in a wide range of space velocity and oxygen content. The catalytic activity is enhanced with an increase of Pt loading from 0.1 to 1.0 wt%. The superacidity of the support material is responsible for the improvement in activity rather than an increase in catalyst surface area or metal dispersion. Pd/SO ₄ ^–2 /ZrO₂ are less active than Pt/SO ₄ ^–2 /ZrO₂.     

Development of potassium ferrate(VI) cathode material stabilized with yttria doped zirconia coating for alkaline super-iron battery

To improve the stability of potassium ferrate(VI) (K₂FeO₄) cathode and its properties of charge transfer in alkaline battery system, K₂FeO₄ cathodes are coated by yttria (Y₂O₃) doped zirconia (ZrO₂) composites, denoted as Y₂O₃–ZrO₂ composite coatings. These composite coatings are derived from the conversion of yttrium nitrate (Y(NO₃)₃·6H₂O) and Zirconium oxychloride (ZrOCl₂·6H₂O) in ether medium. Examinations by scanning electron microscope (SEM) and Fourier transform infrared spectroscopy (FT-IR) show that K₂FeO₄ cathodes are coated by Y₂O₃–ZrO₂ overlayer. Alternatively, results of discharge properties and electrochemical impedance spectroscopes (EIS) indicate that when the molar ratio between Y₂O₃ and ZrO₂ is 0.09, denoted as Y₂O₃ (9 mol%)–ZrO₂, the stability and charge transfer of Y₂O₃ (9 mol%)–ZrO₂ coated K₂FeO₄ cathodes are improved greatly compared to that of uncoated or ZrO₂ coated K₂FeO₄ cathodes. Therefore, Y₂O₃–ZrO₂ composite coatings are a potential choice to improve the stability and charge transfer of K₂FeO₄ cathodes in alkaline electrolyte.     

Microstructure and properties of large bulk Al2O3/ZrO2 (Y2O3) composites prepared by SHS under high gravity

For Al₂O₃/ZrO₂ (4Y) composites prepared by SHS under high gravity, the correlation between the microstructure and properties of the materials was investigated by adjusting the ZrO₂ (4Y) content. The results indicated that, as the volume fraction of ZrO₂ (4Y) was below 37%, the composite ceramics were mainly composed of the rod-shaped and randomly-orientated colonies in which nano-micrometer tetragonal ZrO₂ fibers were embedded; as the volume fraction of ZrO₂ (4Y) was above 40%, the composite ceramics in the matrix of micrometer sphere-like tetragonal ZrO₂ grains were obtained. The mechanical properties showed that Al₂O₃/33% ZrO₂ (4Y) not only had the maximum values of the relative density and hardness because of the low solidification temperature and the highest volume fraction of the colonies but also the maximum flexural strength value due to the small size of defects and high fracture toughness supported by the crack-deflection and crack-bridging toughening mechanisms.     

Characterization of Supported NiSO4 and Effect of TiO2–ZrO2 Composition on Catalytic Activity for Acid Catalysis

A series of catalysts, NiSO₄/TiO₂–ZrO₂ having different TiO₂–ZrO₂ composition, for acid catalysis was prepared by the impregnation method using an aqueous solution of nickel sulfate. The addition of TiO₂ to ZrO₂ improved the surface area of the catalyst and enhanced its acidity remarkably because of the formation of new acid sites through the charge imbalance of Ti–O–Zr bonding. The binary oxide, TiO₂–ZrO₂ calcined above 600 °C resulted in the formation of crystalline orthorhombic phase of ZrTiO₄. Therefore, NiSO₄/TiO₂–ZrO₂ calcined at 500 °C exhibited a maximum catalytic activity for acid catalysis, and then the catalytic activity decreased with the calcination temperature. The correlation between catalytic activity and acidity held for both reaction, 2-propanol dehydration and cumene dealkylation. NiSO₄ supported on 50TiO₂–50ZrO₂ (TiO₂/ZrO₂ ratio = 1) among TiO₂–ZrO₂ binary oxides exhibited the highest catalytic activity for acid catalysis.     

Interfacial reaction behavior and bonding mechanism between liquid Sn and ZrO2 ceramic exposed in ultrasonic waves

Ultrasound-assisted dipping of ZrO₂ ceramics into molten Sn solder was performed to realize the low-temperature joining of ZrO₂ ceramics in this study. Scanning electron microscopy with energy dispersive spectrometer, X-ray diffraction and X-ray photoelectron spectroscopy were employed to study the effects of ultrasonic vibration on the microstructure of Sn/ZrO₂ interface, and to elucidate the joining mechanism between Sn coating layer and ZrO₂ ceramic. Results showed that, after ultrasonically dipping in molten Sn for 1200 s, a pure Sn solder layer with a thickness of approximately 8–9 µm was coated on the ZrO₂ surface. The Sn coating layer exhibited excellent metallurgic bonding with ZrO₂ ceramic. A nano-sized ZrSnO₄ ternary phase, which was beneficial to the smooth transition of the lattice from Sn solder to ZrO₂ ceramic, was formed at the Sn/ZrO₂ interface. The formation of ZrSnO₄ interlayer was ascribed to the acoustic cavitation induced high-temperature reaction of Sn, O and ZrO₂ at the molten Sn/ZrO₂ ceramic interface. The tested average shear strength of ZrO₂/Sn/ZrO₂ joints was approximately 32 MPa, and the shearing failure mainly took place within the Sn solder layer.     

Monolayer dispersion of oxides and salts on surface of ZrO2 and its application in preparation of ZrO2-supported catalysts with high surface areas

The thermostability of ZrO₂ can be improved by dispersing a layer of an active component onto its surface in advance. The research results of seven kinds of catalysts (ZrO₂-supported MoO₃, WO₃, CuO, SO₄ ^2-, NiO, FeSO₄ and Fe₂O₃) show that the surface areas of the samples prepared by impregnating Zr(OH)₄ with the active components and then calcining at high temperature are much larger than those of the samples prepared with an ordinary method, namely, impregnating ZrO₂ calcined at high temperature. The surface areas of the ZrO₂-supported catalysts obtained in this way are several times that of pure ZrO₂ calcined at the same temperature. The characteristic results show: (1) the active components are dispersed on the surface of ZrO₂ as monolayer; (2) there is a good corresponding relationship between the surface coverage and the surface area of the sample; (3) as the loading of an active component comes up to its utmost dispersion capacity, the surface area of the sample will be the largest. The mechanism responsible for these phenomena has been discussed. This revised version was published online in July 2006 with corrections to the Cover Date.     

Improvement of Pt/ZrO2 by CeO2 for high pressure CH4/CO2 reforming

CH₄/CO₂ reforming over Pt/ZrO₂, Pt/CeO₂ and Pt/ZrO₂ with CeO₂ was investigated at 2 MPa. Pt/ZrO₂, which shows stable activity under 0.1 MPa, and Pt/CeO₂ showed gradual deactivation with time at the high pressure. The deactivation was suppressed drastically on Pt/ZrO₂ with CeO₂ prepared by different impregnation order (co-impregnation of Pt and CeO₂ on ZrO₂, and consecutive impregnation of Pt and CeO₂ on ZrO₂). The amount of coke deposition was found insignificant and similar among all the catalysts (including Pt/ZrO₂ and Pt/CeO₂). Catalytic activity after the reaction for 24 h was in agreement with Pt particle size after the reaction for same period, indicating that the difference of the catalytic stability is mainly dependent on the extent of Pt aggregation through catalyst preparation, H₂ reduction, and the CH₄/CO₂ reforming. Pt aggregation and the amount of coke deposition were least pronounced on (Pt–Ce)/ZrO₂ prepared by impregnation of CeO₂ on Pt/ZrO₂ and the catalyst showed highest stability.     

A tribological investigation of SLM fabricated TC4 titanium alloy with carburization pre-treatment

The tribological properties of SLM fabricated TC4 discs (before and after carburization) sliding against ZrO₂ ball at different loads (0.98–4.94 N) under bovine serum lubricated conditions were investigated by using a Ball-On-Disc (BOD) tribo-meter. In comparison, the friction and wear behaviors of the forging fabricated TC4 disc against a ZrO₂ ball were performed under the same lubricated condition, and the results represented the similar trends with the SLM fabricated TC4 (SLM -TC4). Meanwhile, the friction coefficients of SLM-TC4 and SLM-C-TC4 disc (SLM fabricated TC4 after carburization) against ZrO₂ ball both decreased with the increase of the load. Combined with the worn surface analysis and theoretical analysis, it can be concluded that the friction force of the sliding pairs mainly originated from the resistance of deformation and shear stress, and the friction coefficients are linearly correlated to negative one-third power of the normal load. Furthermore, a hard TiC layer was observed on the surface of SLM-C-TC4 disc, which may provide a certain anti-wear capacity between the sliding pairs because of its effective resistance to deformation and shear stress. Therefore, the SLM-C-TC4/ZrO₂ bearing couple showed significantly lower wear than that of the SLM-TC4/ZrO₂ bearing couple and forged TC4/ZrO₂ sliding pair. So, SLM-C-TC4 may be more suitable for joint prosthesis design.     

Phase Stabilization of ZrO2 Polymorph by Combined Additions of Ca2+ and PO43− Ions Through an In Situ Synthetic Approach

This study has been aimed at the phase stabilization of tetragonal Zirconia (t‐ZrO₂) by the additions of Ca²⁺ and PO₄^3? through an in situ synthetic approach. A wide range of variations have been attempted in which the precursor concentrations of Ca²⁺ and PO₄^3? have been maintained constant for every synthesis. The characterization results from XRD, Raman spectra, FT‐IR spectra, XRF, and the quantitative analysis have confirmed the t‐ZrO₂ stabilization for the selected concentrations ranging from 5% to 20% of Ca²⁺ and PO₄^3? in the ZrO₂ system at 900°C. Pure ZrO₂ system without the additions of Ca²⁺ and PO₄^3? have yielded the mixture of c‐ZrO₂ and m‐ZrO₂ at the investigated temperatures ranging between 800°C and 1000°C with no identified traces of t‐ZrO₂. Thus, the stabilization of t‐ZrO₂ has been mainly attributed to the combined influence of Ca²⁺ and PO₄^3? presence in the ZrO₂ matrix creating oxygen vacancies that has been confirmed from impedance measurements. Heat treatment beyond 900°C had resulted in the phase degradation leading to the formation of mixture of phases comprising of major amount of m‐ZrO₂ and minor amount of t‐ZrO₂.     

Porous network ZrO2/ZnFe2O4 nanocomposite with heterojunction towards industrial water purification under sunlight: Enhanced charge separation and elucidation of photo-mechanism

This work majorly aims to synthesize and also investigate the structural, optical, magnetic and optical features of ZrO₂/ZnFe₂O₄ nanocomposite. Here, different ratios of novel hetero-junction ZrO₂/ZnFe₂O₄ were synthesized by simple and fast solution combustion route. The X-ray diffraction results showed the formation of ZrO₂ and ZnFe₂O₄ nanoparticles and ZrO₂/ZnFe₂O₄ nanocomposites without any impurity. The formation of hetero-junction effectively inhibits the photo-generated charge carrier recombination. The degradation of Indigo Carmine dye by ZrO₂/ZnFe₂O₄ photocatalyst was achieved through synergistic effects with 98% degradation and removal of 77% COD from the industrial dye waste water under Sunlight irradiation. Mixing of ferrites with zirconia greatly improves the photocatalytic activity that has been clearly proposed with the help of mechanism. ZZFO 12 NC exhibits better photocatalytic activity due to the combined facets of photo and Fenton activity. The exposure and enhancement of fingerprints in various surfaces are achieved by a modest, extremely sensitive and eco-friendly method. ZZFO12 NC offer great potential as an active photocatalyst for degradation of 54% of organic pollutant present in industrial waste water under natural Sunlight.     

SELECTIVE CARBON MONOXIDE OXIDATION IN H2-RICH GAS STREAM OVER Co3O4/CeO2/ZrO2, Ag/CeO2/ZrO2, AND MnO2/CeO2/ZrO2 CATALYSTS

Activity and selectivity of selective CO oxidation in an H₂-rich gas stream over Co₃O₄/CeO₂/ZrO₂, Ag/CeO₂/ZrO₂, and MnO₂/CeO₂/ZrO₂ catalysts were studied. Effects of the metaloxide types and metaloxide molar ratios were investigated. XRD, SEM, and N₂ physisorption techniques were used to characterize the catalysts. All catalysts showed mesoporous structure. The best activity was obtained from 80/10/10 Co₃O₄/CeO₂/ZrO₂ catalyst, which resulted in 90% CO conversion at 200°C and selectivity greater than 80% at 125°C. Activity of the Co₃O₄/CeO₂/ZrO₂ catalyst increased with increase in Co₃O₄ molar ratio.     

Conductive,Gas Barrier,and Thermal Resistant Behavior of Poly (methyl methacrylate) Composite by Dispersion of ZrO2 Nanoparticles

Poly (methyl methacrylate)/zirconium dioxide (PMMA/ZrO₂) nanocomposites were prepared by the incorporation of ZrO₂ nanoparticles in various proportions (2, 4, 6, 8, and 10%) with PMMA matrix by in situ emulsifier-free emulsion polymerization technique. The structural property of PMMA/ZrO₂ nanocomposites was studied by X-ray diffraction, field emission scanning electron microscopy, and transmission electron microscopy. The thermal stability of PMMA/ZrO₂ nanocomposites was improved with increasing concentration of ZrO₂. The electrical conductivity of composites was measured as function of ZrO₂ concentration. The oxygen barrier properties of PMMA/ZrO₂ nanocomposites were measured by using gas permeameter.     

ZrO2-doped YTaO4 as potential CMAS-resistant materials for thermal barrier coatings application

In this contribution, the ZrO₂-doped YTaO₄ (Zr_xY_0.5−x/2Ta_0.5−x/2O₂ (x = 0, 0.1, 0.2, 0.28)) are proposed as potential CMAS-resistant materials for TBCs. The corrosion behavior of those materials under CMAS attack are investigated from thermodynamics and kinetics. The results show that all compositions have the much better CMAS resistance than the classical Gd₂Zr₂O₇. After 50 h corrosion at 1300℃, the corrosion depth in ZrO₂-doped YTaO₄ bulks is about 50–80 µm (for a 20 mg/cm² CMAS deposition) in contrast with ~140 µm in Gd₂Zr₂O₇ bulk. The CMAS corrosion mechanism of ZrO₂-doped YTaO₄ is elucidated, and the excellent CMAS resistance is attributed to the rapid formation and followed thickening of dense reaction product layer. Furthermore, the effects of ZrO₂ doping content on CMAS resistance of YTaO₄ is discussed. It is elucidated that ZrO₂ doping can inhibit the precipitation of apatite, decrease the consumption of CMAS melt, and change the morphology of dense reaction layer. In summary, minor doping of ZrO₂ can ensure the excellent short- and long-term CMAS resistance, but heavy doping of ZrO₂ will degrade the long-term CMAS resistance.     

Study of the phase composition and properties of periclase-zircon and spinel-zircon refractories

Conclusions Nd₂O₃ and MgO do not react at temperatures of up to 1600°C. ZrO₂, stabilized with 12% (mole) Nd₂O₃, forms with the MgO a cubic solid solution with limited solubility of periclase: the concentrations in this solid solution of magnesia at 1750° reach 12–13% (mole). It is confirmed that an addition of Nd₂O₃ increases the resistance to decomposition of cubic solid solutions ZrO₂-MgO.With an increase in temperature and in the presence of Nd₂O₃ there is rapid decomposition of MgAl₂O₄, as a result of which neodymium monoaluminate and periclase are formed. The neodymium oxide forming with the ZrO₂ a cubic solid solution does not react with the spinel. We note only a slight (1.5–2%) solubility of ZrO₂ in MgAl₂O₄.Studies were made of some properties of periclase-zircon and spinel-zircon refractories. The composition ZrO₂-MgAl₂O₄ is better in terms of thermal-shock resistance than products made from MgO and ZrO₂, stabilized with Nd₂O₃.Translated from Ogneupory, No. 4, pp. 48–52, April, 1972.     

The role of CeO2–ZrO2 as support in the ZnO–ZnCr2O4 catalysts for autothermal reforming of methanol

Autothermal reforming of methanol for hydrogen production was investigated over ZnO–ZnCr₂O₄ supported on a series of metal oxides (Al₂O₃, CeO₂, ZrO₂ and CeO₂–ZrO₂). CeO₂–ZrO₂ mixed oxides with Ce /Zr molar ratio of 4/1 was found to be the optimal support which showed significant effect on the catalytic activity and selectivity. The ZnO–ZnCr₂O₄/CeO₂–ZrO₂ and ZnO–ZnCr₂O₄ catalysts were characterized by XRD, TEM, H₂-TPR and XPS. The results show that CeO₂–ZrO₂ mixed oxides have significant effect on the catalytic performance and the supported catalyst shows more uniform temperature distribution in the catalyst bed which was mainly due to its reasonable redox properties.     

Amorphous silicon and silicates-stabilized ZrO2 hollow fiber with low thermal conductivity and high phase stability derived from a cogon template

ZrO₂ fibers are used as refractory materials owing to their excellent thermal resistance and thermal stability. Natural cogon fiber is a type of hollow Gramineae fiber, and usually contains a small amount of amorphous silicon and silicates, such as SiO₂, MgSiO₃, CaSiO₄, and Al₂SiO₅, which can effectively avoid the phase transition of ZrO₂. In this study, hollow ZrO₂ fibers with remarkable thermal insulation and phase stability were synthesized using a cogon fiber template. The results showed that the final ZrO₂ fibers successfully inherited the hollow structure and amorphous substance from the cogon template. The hollow structure of the biomorphic ZrO₂ fiber helped prevent heat flow more efficiently compared to solid fibers and reduced the thermal conductivity to a significant extent. In addition, the amorphous silicon and silicates played an important role in the phase stability of tetragonal ZrO₂; the transformation from the tetragonal to monoclinic phase was avoided at room temperature and in humid environment.     

Isomerization and Arylation of Oleic Acid on Anion Modified Zirconia Catalysts

The catalytic performance of anion modified zirconia catalysts, such as sulfated zirconia (SO₄/ZrO₂) and tungstated zirconia (WO₃/ZrO₂), was evaluated for the upgrading of oleic acid (OA). In the presence of an aromatic compound, two main reactions occurred on the catalysts: the skeletal isomerization of OA and the arylation of OA with aromatics. The activity of the SO₄/ZrO₂ was more than triple of that of the WO₃/ZrO₂. At 250 °C, OA/(SO₄/ZrO₂)(wt/wt) = 5, the OA conversion and the arylation selectivity reached their maximal values and the isomerization selectivity was the lowest when the toluene to OA (toluene/OA) molar ratio was about 6. When mesitylene was used instead of toluene, the OA conversion and the arylation selectivity decreased, probably because of a steric effect. An attempt to reuse the SO₄/ZrO₂ by solvent washing after a run was not so successful, while calcination at 630 °C in air recovered the activity completely.