共查询到20条相似文献,搜索用时 31 毫秒
1.
Petr Kluson Hana Luskova Libor Cerveny Tomas Cajthaml 《Reaction Kinetics and Catalysis Letters》2005,86(2):281-289
Summary Unexpected photocatalytic properties of templated precursors of nanostructured TiO2(titania) were observed in the development of a generally applicable method for the synthesis of a truly nanocrystalline titania
at temperatures compatible with plastic catalytic supports. It specifically comprised the “self-activation”feature of the
TiO2nanostructured precursor (produced within the non-ionic surfactant template) likely induced by the preparation method “imprinted”photoactivity.
Such behavior complied with the principal aim to develop the photocatalytic material without recourse to any significant thermal
step. 相似文献
2.
Alvaro de Jesús Martínez-Gómez Sorin O. Manolache Víctor Gónzalez-Álvarez Raymond A. Young Ferencz Sandor Denes 《Cellulose (London, England)》2009,16(3):501-517
The surface functionalization process was accomplished in a consecutive 3 step process including: (1) Argon- and oxygen-plasma
enhanced generation of free radical sites on cellophane surfaces; (2) “In situ” gas phase derivatization in the absence of
plasma using hydrazine, ethylene diamine, or propylene diamine; (3) Second “in situ”, gas phase derivatization in the absence
of plasma using oxallyl chloride or “ex situ” derivatization in the presence of glutaraldehyde. The presence of free radical
sites on the plasma exposed cellophane surfaces was demonstrated using “in situ” sulfur dioxide and nitric oxide labeling
techniques. It was shown that the free radical sites readily react under “in situ” conditions with the stable chain-precursor
components and generate the desired spacer-chain molecules. ESCA, ATR-FTIR analysis and dying techniques were used to monitor
the cellophane surface changes. A factorial design was used for selecting the optimal plasma parameters. Functionalized cellophane
substrates were used for immobilization of α-chymotrypsin in the presence of spacer-chain molecules. The activity of the immobilized
α-chymotrypsin was found to be lower in comparison to the activity of the free enzyme and the presence of virgin cellophane
in the free enzyme solution also reduced significantly the activity of the enzyme. It is suggested that the swollen state
of the cellophane plays a significant role in the decrease of the immobilized enzyme activity. 相似文献
3.
Jiaqiang Wang Hua Fang Ying Li Junjie Li Zhiying Yan 《Journal of molecular catalysis. A, Chemical》2006,250(1-2):75-79
Cobalt-doped mesoporous titania with a crystalline framework synthesized by surfactant templating method presented highly selective (99%) and reasonable conversion rate (49%) of catalytic oxidation of para-chlorotoluene to para-chlorobenzaldehyde in acetic acid using aqueous hydrogen peroxide as oxidant for the first time. Recycling of the catalyst indicates that the catalyst can be used a number of times without losing its activity to a greater extent. By contrast, cobalt-doped mesoporous titania without a crystalline structure and cobalt doped the commercial titania, Degussa P25 prepared by impregnation method with the similar concentration of cobalt were found inactive. The effects of catalyst concentration, reaction time, reaction temperature, and solvents on the performance of the catalyst were also investigated. 相似文献
4.
Mesoporous titania has been successfully synthesized by photodegradation removal of cetyltrimethylammonium bromide as the surfactant, after slow hydrolyzation of titanium(IV) isopropoxide. Fourier transform infrared spectra proved that photodegradation has successfully decreased the peak areas of the alkyl groups from the template. The nitrogen adsorption analysis showed that the pore size and the specific surface area of the mesoporous titania were 3.7 nm and 203 m2 g−1, respectively, proving the mesoporosity of the titania obtained with the existence of the interparticle mesoporosity which was confirmed by transmission electron microscopy. Based on X-ray diffraction results, the mesoporous titania obtained was in the form of crystalline anatase phase. Furthermore, results from the diffuse reflectance ultra violet-visible spectra showed that the composition of tetrahedral titanium(IV) was more than the octahedral titanium(IV). When the mesoporous titania obtained was used as a catalyst in the oxidation of styrene, an improvement in the conversion of styrene (38%) was observed when compared to those obtained using Degussa P25 TiO2 (14%) as the catalyst. 相似文献
5.
Dudchenko V. K. Shabalin E. U. Arkatov O. L. Maier E. A. 《Russian Journal of Applied Chemistry》2010,83(3):529-538
On the basis of R&D results on laboratory and pilot levels the possibility of production and expansion of “Tomskneftekhim”
Ltd. brand assortment of polyolefin plastics with the use of contemporary titaniummagnesium catalysts (TMC) is analyzed. The
production results of “Tomskneftekhim” Ltd. polypropylene output, reached due to the use of catalyst systems of I (aluminothermal
TiCl3) and II (MSK-TiCl3) generations, and forecasting results for system of IV generation (TMC) are presented in the report. The experimental testing
of propylene polymerization kinetic features, raw material quality, and influence of catalyst system composition and conditions
of formation on exploitation characteristics of TMC was carried out by the example of two trade marks of TMC. The conclusion
was drawn that the realization by “Tomskneftekhim” Ltd. of a complex program of R&D activities for implementation of the IV
generation catalyst system in the suspension technology of the polypropylene production will increase the competitiveness
of the process. 相似文献
6.
Yurong Bian Xiaohong Wang Zhigang Zeng Zhiyu Hu 《Surface and interface analysis : SIA》2013,45(9):1317-1322
Ordered mesoporous titania thin films were synthesized by evaporation induced self‐assembly process in the presence of Pluronic block copolymers P123 (EO20‐PO70‐EO20). The influence of several experimental parameters, including aging humidity, aging temperature, substrate properties and methods for organic templates removal, on the mesostructure of titania thin films was investigated in details. The mesoporous titania thin film supported Pt catalyst was prepared, and its methanol catalytic combustion performance was studied. The results showed that mesoporous titania thin film is an active support for catalyst. Mesoporous titania thin film supported platinum catalysts yields 70% methanol conversion at room temperature and 100% conversion at 100 °C. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
7.
An efficient, mild, and environmental friendly method has been developed for the synthesis of dicoumarols in water over Lewis and Bronsted acid catalyst sulfated titania (TiO2/SO42−). The method involves the condensation of various aromatic and aliphatic aldehydes with 4-hydroxycoumarin. It affords the corresponding product in high yield with short reaction times employing a very low loading of catalyst. The catalyst was reused several times without significant change in activity. 相似文献
8.
In this work, palladium complexes nanoparticles in titania are prepared by a pH‐controlled adsorption and without pH‐controlled adsorption method. This method results in high‐dispersion palladium on the titania surface. We demonstrate the use of the titania‐supported palladium as an efficient catalyst for Suzuki and Heck reactions of a representative range of aryl bromides and chlorides. The reusability of catalyst was tested, and deactivation process of the catalyst was not observed after four recycles. The catalysts were characterized by FT‐IR, NMR, elemental analysis, field emission scanning electron microscopy, transmission electron microscopy and X‐ray diffraction. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
9.
P. Padmaja K. G. K. Warrier M. Padmanabhan W. Wunderlich 《Journal of Sol-Gel Science and Technology》2009,52(1):88-96
Alumina–titania mixed oxide nanocatalysts with molar ratios = 1:0.5, 1:1, 1:2, 1:5 have been synthesized by adopting a hybrid
sol–gel route using boehmite sol as the precursor for alumina and titanium isopropoxide as the precursor for titania. The
thermal properties, XRD phase analysis, specific surface area, adsorption isotherms and pore size details along with temperature
programmed desorption of ammonia are presented. A specific surface area as high as 291 m2/g is observed for 1:5 Al2O3/TiO2 composition calcined at 400 °C, but the same composition when calcined at 1,000 °C, resulted in a surface area of 4 m2/g, while 1:0.5 composition shows a specific surface area of 41 m2/g at 1,000 °C. Temperature programmed desorption (of ammonia) results show more acidic nature for the titania rich mixed
oxide compositions. Transmission electron microscopy of low and high titania content samples calcined at 400 °C, shows homogeneous
distribution of phases in the nano range. In the mixed oxide, the particle size ranges between 10–20 nm depending on titania
content. The detailed porosity data analysis contributes very much in designing alumina–titania mixed oxide nanocatalysts. 相似文献
10.
二氧化钛负载氧化物催化剂上CO的氧化反应 总被引:4,自引:1,他引:3
对浸渍法和共沉淀法制备以的各种TiO2负载氧化物催化剂进行了活性组分的筛选,结果发现,两种方法得到的CuO催化剂均具有优良的CO氧化催化性能。在此基础上,考察不同TiO2载体,活性组分含量以及催化剂焙烧温度对其催化能力的影响。结果表明,具有高比表面、大孔体积的TiO2载体负功的CuO催化剂具有较好的催化性能,活性组分CuO的最佳含量范围在10%~15%之间,催化剂最佳焙烧温度为400℃。 相似文献
11.
A model of dissociative chemisorption on a surface with a square lattice was studied using the Monte Carlo method. The model
is based on two chemisorption pathways: “direct”—nucleation of adsorption islands, and “indirect”—their growth. The development
of the surface distribution picture of chemisorbed particles was found to depend significantly on the contribution of these
two pathways (Sindir/Sdir). 相似文献
12.
Ren J Qin H Wang J Luedtke NW Wang E Wang J 《Analytical and bioanalytical chemistry》2011,399(8):2763-2770
In this study we have used two fluorescent probes, tetrakis(diisopropylguanidino)-zinc-phthalocyanine (Zn-DIGP) and N-methylmesoporphyrin IX (NMM), to monitor the reassembly of “split” G-quadruplex probes on hybridization with an arbitrary
“target” DNA. According to this approach, each split probe is designed to contain half of a G-quadruplex-forming sequence
fused to a variable sequence that is complementary to the target DNA. Upon mixing the individual components, both base-pairing
interactions and G-quadruplex fragment reassembly result in a duplex–quadruplex three-way junction that can bind to fluorescent
dyes in a G-quadruplex-specific way. The overall fluorescence intensities of the resulting complexes were dependent on the
formation of proper base-pairing interactions in the duplex regions, and on the exact identity of the fluorescent probe. Compared
with samples lacking any “target” DNA, the fluorescence intensities of Zn-DIGP-containing samples were lower, and the fluorescence
intensities of NMM-containing samples were higher on addition of the target DNA. The resulting biosensors based on Zn-DIGP
are therefore termed “turn-off” whereas the biosensors containing NMM are defined as “turn-on”. Both of these biosensors can
detect target DNAs with a limit of detection in the nanomolar range, and can discriminate mismatched from perfectly matched
target DNAs. In contrast with previous biosensors based on the peroxidase activity of heme-bound split G-quadruplex probes,
the use of fluorescent dyes eliminates the need for unstable sensing components (H2O2, hemin, and ABTS). Our approach is direct, easy to conduct, and fully compatible with the detection of specific DNA sequences
in biological fluids. Having two different types of probe was highly valuable in the context of applied studies, because Zn-DIGP
was found to be compatible with samples containing both serum and urine whereas NMM was compatible with urine, but not with
serum-containing samples. 相似文献
13.
M. Zamora T. López R. Gómez M. Asomoza A. GarcÍa-Ruiz X. Bokhimi 《Journal of Sol-Gel Science and Technology》2004,32(1-3):339-343
The effect on titania of doping with lithium and rubidium titania gels has been studied in samples prepared with titanium (IV) tetra-n-butoxide co-gelling with the alkaline metal precursors. Titania and doped titania were characterized by X-Ray diffraction, which showed that the catalysts were nanostructured. In samples calcined at 400°C, the crystallite size of the anatase phase was 17 and 14 nm, and 78 and 38 nm for samples calcined at 600°C, for Li/TiO2 and Rb/TiO2, respectively. The specific surface areas of doped samples (400°C) are lower in Li/TiO2 (90 m2/g) than in Rb/TiO2(125 m2/g). Evaluation of their basic properties has been carried out in the acetone condensation reaction. It was found that the activity strongly depended on the Li and Rb ionic radii. 相似文献
14.
Multivariate analysis of HT/GC-(IT)MS chromatographic profiles of triacylglycerol for classification of olive oil varieties 总被引:1,自引:0,他引:1
Cristina Ruiz-Samblás Luis Cuadros-Rodríguez Antonio González-Casado Francisco de Paula Rodríguez García Paulina de la Mata-Espinosa Juan Manuel Bosque-Sendra 《Analytical and bioanalytical chemistry》2011,399(6):2093-2103
The ability of multivariate analysis methods such as hierarchical cluster analysis, principal component analysis and partial
least squares-discriminant analysis (PLS-DA) to achieve olive oil classification based on the olive fruit varieties from their
triacylglycerols profile, have been investigated. The variations in the raw chromatographic data sets of 56 olive oil samples
were studied by high-temperature gas chromatography with (ion trap) mass spectrometry detection. The olive oil samples were
of four different categories (“extra-virgin olive oil”, “virgin olive oil”, “olive oil” and “olive-pomace” oil), and for the
“extra-virgin” category, six different well-identified olive oil varieties (“hojiblanca”, “manzanilla”, “picual”, “cornicabra”,
“arbequina” and “frantoio”) and some blends of unidentified varieties. Moreover, by pre-processing methods of chemometric
(to linearise the response of the variables) such as peak-shifting, baseline (weighted least squares) and mean centering,
it was possible to improve the model and grouping between different varieties of olive oils. By using the first three principal
components, it was possible to account for 79.50% of the information on the original data. The fitted PLS-DA model succeeded
in classifying the samples. Correct classification rates were assessed by cross-validation. 相似文献
15.
一种TiO2修饰的Pd/Al2O3选择性加氢用催化剂的研究 总被引:8,自引:0,他引:8
研制了一种用TiO2修饰的Pd/Al2O3(Pd/Al2O3-TiO2)选择性加氢催化剂,并采用N2吸附,XRD,SEM,FT-IR,TPD和TPR等手段对催化剂进行了表征,考察了催化剂的催化性能. 结果表明,Pd/Al2O3-TiO2催化剂具有较小的比表面积; 低的表面酸性,且以弱酸中心为主; TiO2在Al2O3表面呈高度分散,并集中于载体到一定的深度; 用含钛溶液浸渍次数以1次为佳. 载体中TiO2的添加使得PdO更易于被还原. 用这种复合氧化物作载体制备的催化剂表现出更高的加氢活性和选择性,优于单纯以Al2O3作载体的催化剂. 相似文献
16.
HanQing Ge Yan Leng FuMin Zhang JiaRui Piao ChangJiang Zhou Jun Wang 《中国科学B辑(英文版)》2009,52(8):1264-1269
Pyridine(Py)-modified Keggin-type vanadium-substituted heteropoly acids (Py
n
PMo10V2O40, n=1 to 5) were prepared by a precipitation method as organic/inorganic hybrid catalysts for direct hydroxylation of benzene
to phenol in a pressured batch reactor and their structures were detected by FT-IR. Among various catalysts, Py3PMo10V2O40 exhibits the highest catalytic activity (yield of phenol, 11.5%), without observing the formation of catechol, hydroquinone
and benzoquinone in the reaction with 80 vol% aqueous acetic acid, molecular oxygen and ascorbic acid used as the solvent,
oxidant and reducing reagent, respectively. Influences of reaction temperature, reaction time, oxygen pressure, amount of
ascorbic acid and catalyst on yield of phenol were investigated to obtain the optimal reaction conditions for phenol formation.
Pyridine can greatly promote the catalytic activity of the Py-free catalyst (H5PMo10V2O40), mostly because the organic π electrons in the hybrid catalyst may extend their conjugation to the inorganic framework of
heteropoly acid and dramatically modify the redox properties, at the same time, pyridine adsorbed on heteropoly acids can
promote the effect of “pseudo-liquid phase”, thus accounting for the enhancement of phenol yield.
Supported by the National Natural Science Foundation of China (Grant Nos. 20476046 and 20776069) and the “Qinglan” Project
of Jiangsu Province for Young Researchers 相似文献
17.
We have used X-ray phase analysis, temperature programmed desorption of argon, and IR spectroscopy to study the conditions
and characteristics of formation and the adsorption and acidic properties of mesoporous phosphated zirconium dioxide. We have
established that treatment of a mesostructural and mesoporous hydrogel of zirconium hydroxide with a solution of orthophosphoric
acid not only promotes stabilization of the mesostructure and the texture when detemplated, but also functionalization of
the zirconium dioxide surface.
__________
Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 42, No. 1, pp. 49–54, January–February, 2006. 相似文献
18.
J. J. Calvino M. A. Cauqui G. Cifredo J. M. Rodríguez-Izquierdo H. Vidal 《Journal of Sol-Gel Science and Technology》1994,2(1-3):831-836
The influence of the preparation method on the microstructure and catalytic behavior of Rh and Ni dispersed on TiO2-SiO2 aerogels is investigated.The autoclave method has been followed to prepare titania-silica aerogels with TiO2 contents ranging between 0 and 10 mole %. These aerogels have been used as matrices to disperse catalytically active metals: Rh and Ni. The metals can be deposited by impregnation of aerogels, or alternatively, can be added into the hydrolysis water used in the synthesis of gels. The resulting catalysts present surface areas higher than 550 m2·g–1.The percentage of titania, the method followed for the introduction of the metal, and the nature of the metal itself affect both the activities and selectivities of the catalysts in the hydrogenolysis of n-butane. Thus, the presence of titania in Rh catalysts increases the activity values, and the samples prepared by impregnation present selectivities towards ethane higher than 80%. Whereas, the rhodium catalysts in which the metal has been introduced before gelling, do not orientate the reaction in favor of a definite product. For the case of Ni, it is quite frequent to obtain high selectivities towards the breakdown of the C-C terminal bonds. In summary, the preparation methods allow to modulate into very broad limits the catalytic behavior of the samples. 相似文献
19.
So Hee Yoon Jeong Hee Moon Myung Soo Kim 《Journal of the American Society for Mass Spectrometry》2010,21(11):1876-1883
In-source decay (ISD) and post-source decay (PSD) of a peptide ion ([Y6 + H]+) and a preformed ion (benzyltriphenylphosphonium, BTPP) generated by matrix-assisted laser desorption ionization (MALDI)
were investigated with time-of-flight mass spectrometry. α-Cyano-4-hydroxycinammic acid (CHCA) and 2,5-dihydroxybenzoic acid
(DHB) were used as matrices. For both ions, ISD yield was unaffected by delay time, indicating rapid termination of ISD. This
was taken as evidence for rapid expansion cooling of hot “early” plume formed in MALDI. CHCA was hotter than DHB for [Y6 + H]+ while the matrix effect was insignificant for BTPP. The “early” plume temperature estimated utilizing previous kinetic results
was 800–900 K, versus 400–500 K for “late” plume. The results support our previous finding that the temperature of peptide
ions interrogated by tandem mass spectrometry was lower than most rough estimates of MALDI temperature. 相似文献
20.
Phosphated tungstate as a new, reusable and efficient solid phosphoric acid catalyst was synthesized and used to promote the reaction of diaminoglyoxime with various aromatic aldehydes. The prepared phosphated tungstate was characterized using various techniques including X‐ray diffraction, scanning electron microscopy, energy‐dispersive X‐ray spectroscopy, Fourier transform infrared spectroscopy and thermal analysis. A wide variety of heterocyclic nitrones were obtained under mild reaction conditions and in high yields by using the prepared catalyst. 相似文献