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1.
Biodiesel production by the transesterification of cottonseed oil by solid acid catalysts 总被引:2,自引:0,他引:2
Chen He Peng Baoxiang Wang Dezheng Wang Jinfu 《Frontiers of Chemical Engineering in China》2007,1(1):11-15
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] 相似文献
2.
Bernard Coq Christian Walter Ronald Brown Gordon McDougall François Figuéras 《Catalysis Letters》1996,39(3-4):197-203
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-SO4/2– supports this proposal. 相似文献
3.
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. 相似文献
4.
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. 相似文献
5.
6.
W. Y. Liu Z. M. Zhao L. Zhang L. Wang 《International Journal of Self-Propagating High-Temperature Synthesis》2009,18(3):180-185
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. 相似文献
7.
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. 相似文献
8.
《Ceramics International》2017,43(10):7531-7536
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. 相似文献
9.
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. 相似文献
10.
Katsutoshi Nagaoka Kulathuiyer Seshan Kazuhiro Takanabe Ken-ichi Aika 《Catalysis Letters》2005,99(1-2):97-100
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. 相似文献
11.
《Ceramics International》2020,46(3):3043-3050
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. 相似文献
12.
Subramaniyan Vasanthavel Sanjeevi Kannan 《Journal of the American Ceramic Society》2014,97(12):3774-3780
This study has been aimed at the phase stabilization of tetragonal Zirconia (t‐ZrO2) by the additions of Ca2+ and PO43? through an in situ synthetic approach. A wide range of variations have been attempted in which the precursor concentrations of Ca2+ and PO43? 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 PO43? in the ZrO2 system at 900°C. Pure ZrO2 system without the additions of Ca2+ and PO43? 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 PO43? 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. 相似文献
13.
L. Renuka K.S. Anantharaju Y.S. Vidya H. Nagabhushana B. Uma S. Malini Sunil S. More Praveennath Koppad 《Ceramics International》2021,47(10):14845-14861
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. 相似文献
14.
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. 相似文献
15.
《国际聚合物材料杂志》2012,61(14):733-736
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. 相似文献
16.
Di Wu Yao Yao Xiao Shan Huangyue Cai Lingyue Hu Xiaofeng Zhao 《Journal of the American Ceramic Society》2021,104(11):6029-6043
In this contribution, the ZrO2-doped YTaO4 (ZrxY0.5−x/2Ta0.5−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. 相似文献
17.
V. I. Strakhov Ya. V. Klyucharov G. G. Sergeev 《Refractories and Industrial Ceramics》1972,13(3-4):260-263
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. 相似文献
18.
Na Liu Zhongshan Yuan Congwei Wang Shudong Wang Chunxi Zhang Shujuan Wang 《Fuel Processing Technology》2008
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. 相似文献
19.
Tianchi Wang Zihao Zhang Changhao Dai Qi Li Yicong Li Jian Kong Chingping Wong 《Ceramics International》2019,45(6):7120-7126
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. 相似文献
20.
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. 相似文献