共查询到20条相似文献,搜索用时 17 毫秒
1.
Mehdi D. Esrafili Parisasadat Mousavian 《International journal of quantum chemistry》2019,119(7):e25857
Using dispersion-corrected density functional theory (DFT) calculations, a single Cu adatom incorporated nitrogen-doped graphene (CuN3-Gr) is proposed as a new and highly active noble-metal-free catalyst for carbon monoxide (CO) oxidation reaction. According to our results, the Cu adatom can be stably anchored onto the monovavancy site of the nitrogen-doped graphene, and the resulting large diffusion barrier suggests that the metal clustering is avoided in CuN3-Gr. Three possible reaction mechanisms for CO oxidation (ie, Eley–Rideal, Langmuir–Hinshelwood, and termolecular Eley–Rideal) are systematically studied. It is found that the activation energy for the rate-determining step of the termolecular Eley–Rideal mechanism is only 0.13 eV, which is much smaller than those of others. The results of this study may provide a useful guideline for the design of highly active and promising single-metal catalysts for the CO oxidation reaction based on graphene. 相似文献
2.
2,3-Dihydro-1H-1,5-benzodiazepines are synthesized by the condensation of o-phenylendiamine and various ketones in the presence of a versatile solid superacid catalyst ‘sulfated zirconia’ under solvent free conditions. 相似文献
3.
A. V. Timoshok A. F. Bedilo A. M. Volodin 《Reaction Kinetics and Catalysis Letters》1996,59(1):165-171
Benzene dimer cation radicals were detected on sulfated zirconia at low temperature and benzene coverage. Two temperature regions for their transformations were observed. Below 473 K the radical concentration remained stable reflecting the amount of strong surface acceptor sites. Above 623 K it increased drastically. 相似文献
4.
纯四方相硫化氧化锆催化剂的制备及其生物柴油合成应用研究 《燃料化学学报》2017,45(3):311-316
将过硫酸铵浸渍于直接合成的纳米氧化锆晶体表面,经300-500℃高温焙烧处理获得硫化氧化锆催化剂。采用X射线衍射(XRD)、氮气吸附-脱附、氨气程序升温脱附(NH3-TPD)、傅里叶红外光谱(FT-IR)、扫描电镜(SEM)和能谱仪(EDS)等分析手段对催化剂的结构性能进行了表征。结果表明,所有的催化剂均展现出纯四方相结构和高的结晶度。其中,经500℃热处理获得的催化剂拥有最高的硫含量和酸性位,将其应用于大豆油与甲醇酯交换反应合成生物柴油,获得了脂肪酸甲酯收率高达84.6%的催化效果,进一步表明该催化剂表面存在优越的超强酸位。 相似文献
5.
Vera P. Shmachkova Nina S. Kotsarenko Vladislav V. Kanazhevskiy Galina N. Kryukova Dimitri I. Kochubey Jacques Vedrine 《Reaction Kinetics and Catalysis Letters》2007,91(1):177-185
Methods of the preparation of catalysts for alkane skeletal isomerization based on uniform nanoparticles of sulfated zirconia
anchored to different supports were investigated. These catalysts were characterized by using the ICP, HRTEM and BET techniques.
The activities of the catalysts in the reaction of n-butane isomerization were measured and compared with those of bulk catalysts. 相似文献
6.
Didik Prasetyoko Zainab Ramli Salasiah Endud Hadi Nur 《Reaction Kinetics and Catalysis Letters》2005,86(1):83-89
Summary Titanosilicalite-1 (TS-1) in combination with sulfated zirconia efficiently catalyzes the epoxidation of 1-octene with aqueous hydrogen peroxide. The presence of both octahedral zirconium and sulfate species in the catalysts enhances the epoxidation rates. 相似文献
7.
Chong-Jiang Cao Xi-Zhi Yu Chang-Lin Chen Nan-Ping Xu Yan-Ru Wang Chung-Yuan Mou 《Reaction Kinetics and Catalysis Letters》2004,83(1):85-92
Sulfated zirconia catalysts promoted by gallium or aluminium were prepared and tested for n-butane isomerization. Both elements increase and stabilize the isomerization rate. Characterization results showed that the
promoting mechanism of gallium was different from that of aluminium.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
8.
Aleksandra R. Zarubica Milena N. Miljkovic Ern E. Kiss Goran C. Boskovic 《Reaction Kinetics and Catalysis Letters》2007,90(1):145-150
Activities of two catalysts obtained from hydroxide and alkoxide precursors were correlated to their different structural
and textural properties. Activity is mainly determined by the presence of active tetragonal phase, which is more stable at
high temperatures in the catalyst of alkoxide origin than in one from hydroxide. An appropriate structure must be accompanied
with beneficial pore structure, as is the case of mesopores of the catalyst from alkoxide. In the case of very small pores
of the catalyst from hydroxide precursor, activity is negligible due to pores plugged by coke. 相似文献
9.
Shaobin Wang Kazuhisa Murata Takashi Hayakawa Satoshi Hamakawa Kunio Suzuki 《Reaction Kinetics and Catalysis Letters》1999,68(2):265-270
Several metal oxides supported on sulfated zirconia catalysts were tested for the oxidative dehydrogenation of ethane into
ethylene by carbon dioxide. It is found that the catalytic behavior of supported oxide catalysts differ depending on the nature
of metal oxides. Chromium oxide-sulfated zirconia exhibits the highest ethane conversion and medium level of ethylene selectivity,
producing 38% ethylene yield at 50% ethane conversion at 650°C. 相似文献
10.
We studied on the function of the metal in the sulfated zirconia(SO42–/ZrO2) catalyst for the isomerization reaction of light paraffins. The addition of Pt to the SO42–/ZrO2 carrier could keep the high catalytic activity. The improvement in this isomerization activity is because Pt promotes removal of the coke precursor deposited on the catalyst surface. Though this catalytic function was observed in other transition metals, such as Pd, Ru, Ni, Rh and W, Pt exhibited the highest effect among them. It was further found that the Pd/SO42–/ZrO2–Al2O3 catalyst possessed a catalytic function for desulfurization of sulfur-containing light naphtha in addition to the skeletal isomerization. The sulfur tolerance of catalyst depended on the method of adding Pd, and the catalyst prepared by impregnation of the SO42–/ZrO2–Al2O3 with an aqueous solution of Pd exhibited the highest sulfur tolerance.Further, we investigated the improvement in sulfur tolerance of the Pt/SO42–/ZrO2–Al2O3 catalyst by impregnation of Pd. The results of EPMA analysis indicated that this catalyst was a hybrid-type one (Pt/SO42–/ZrO2–Pd/Al2O3) in which Pt/SO42–/ZrO2 particles and Pd/Al2O3 particles adjoined closely. This hybrid catalyst possessed a very high sulfur tolerance to the raw light naphtha that was obtained from the atmospheric distillation apparatus, although this light naphtha contained much sulfur. We assume that such a high sulfur tolerance in the hybrid catalyst is brought about by the isomerization function of Pt/SO42–/ZrO2 particles and the hydrodesulfurization function of Pd/Al2O3 particles. Besides, since the hybrid catalyst also provides high catalytic activity in the isomerization of HDS light naphtha, we suggest that the Pd/Al2O3 particles supply atomic hydrogen to the Pt/SO42–/ZrO2 particles by homolytic dissociation of gaseous hydrogen and also enhance the sulfur tolerance of Pt/SO42–/ZrO2 particles. Finally, we also propose the most suitable location of Pd and Pt in the metal-supported SO42–/ZrO2–Al2O3 catalyst. 相似文献
11.
To maximize the production of esters (E), keto (K) and keto-ester (KE) by esterification and ketalization of levulinic acid (LA) has been reacted using diols such as 1,2-propane diol (PDOL),1,2-ethane diol (EDOL), and 1,2,3-propane triol or glycerol (TRIOL) with desilicated Hβ. This work aims to assess the conversion and selectivity for the production of esters using conventional and microwave-irradiated (MWI) reactors. Catalysts characterizations were performed using NH3-temperature programme desorption, Brunauer, Emmett and Teller surface area (BET), Barrett, Joyner, and Halenda (BJH), scanning electron microscope, transmission electron microscope, and dynamic light scattering. Operating parameters such as reaction temperature (170–180°C), reaction time (20–80 min), feed composition (LA:PDOL/EDOL/TRIOL, 1:8/10/12), and microwave energy (300–500 watt) have been systematically investigated. Note that 99–100% conversion was achieved with the product selectivity of E (40%), K (30%), and KE (30%) with1,2-EDOL; E (56%), K (2%), and KE (17%) with 1,2-PDOL; E (69%), K(0%), and KE (22%) with TRIOL using D-Hβ as a solid catalyst in an MWI reactor. Reaction paths and kinetics were studied using pseudo-homogeneous (PH) model. 相似文献
12.
Hiromi Matsuhashi Masakazu Oikawa Hiromi Shibata Michiko Tanaka 《Reaction Kinetics and Catalysis Letters》1998,65(2):253-258
Reversible formation of F+-centers was observed over platinum promoted sulfated zirconia in the presence and absence of hydrogen. The intensity of ESR
signal of F+-centers was increased by treatment in He stream and it was decreased rapidly by supply of hydrogen in gas phase. This behavior
seems to be related to proton spillover. 相似文献
13.
Density functional theory study of the reactivity and electronic structure of the transesterification of triacetin in biodiesel production via a sulfated zirconia heterogeneous catalysis
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Jesús Muñiz Roger Castillo José B. Robles Enrique Sansores 《International journal of quantum chemistry》2016,116(13):988-999
This DFT study examined the interaction of a sulfated zirconia (SZ) slab model system (heterogeneous catalyst) and triacetin (a precursor in biodiesel production) using explicit methanol solvent molecules. Full geometry optimizations of the systems were performed at the B3LYP level of theory. Gibbs free energies provide insight into the spontaneity of the reactions along a three‐step reaction mechanism for the transesterification of triacetin. Charge decomposition analysis revealed electronic charge transfer between the metallic oxide and the organic moieties involved in the reaction mechanism. Fukui indices indicate the likely locations on the SZ surface where catalysis may occur. The quadratic synchronous transit scheme was used to locate transition structures for each step of the transesterification process. The results are in agreement with the strongly acidic catalytic character of zirconium observed experimentally in the production of biodiesel. © 2016 Wiley Periodicals, Inc. 相似文献
14.
Kaiqing Ren Decun Kong Xuan Meng Xin Wang Li Shi Naiwang Liu 《Journal of Saudi Chemical Society》2019,23(2):198-204
In this work, sulfated zirconia (SZ) was prepared by a solvent-free method, ammonium sulfate ((NH4)2SO4) and sulfamic acid (NH2SO3H) were as sulfur sources, respectively. The resulting catalysts were characterized by powder X-ray diffraction (XRD), thermogravimetric analysis and differential scanning calorimetry (TGA-DSC), N2 adsorption–desorption isotherms, inductively coupled plasma (ICP) and pyridine-FTIR. The characterization of the catalysts revealed that SZ prepared with (NH4)2SO4 as sulfur source contained more Lewis acid sites and less Brønsted acid sites. The effects of sulfur sources on the catalytic activity of catalysts were studied. Catalytic testing showed that SZ prepared with (NH4)2SO4 as sulfur source had a better catalytic performance for removing trace olefins from aromatics. 相似文献
15.
The objective of this research work was to investigate the kinetics of esterification of acetic acid with n-butanol through the variation of experimental parameters. The reaction mixture was catalyzed heterogeneously by a sulfonated catalyst in batch mode of operation. The catalyst was prepared from abundantly available agro-waste, Cajanus cajan husk by chemical activation process, which produces a carbon-based solid catalyst with high surface area. The catalyst was characterized by a Brunauer-Emmet-Teller surface analyzer and Fourier transform infrared spectroscopy to know the surface morphology. Process parameters such as contact time, reaction temperature, and catalyst loading, which can influence the extent of conversion of reactants, were studied. Furthermore, the kinetic investigation was also carried out to estimate the kinetic parameters for uncatalyzed and catalyzed reaction using the second-order pseudo-homogeneous (P-H), Eley-Rideal (E-R), and Langmuir-Hinshelwood (LH) kinetic models for this research work. The kinetic parameters such as activation energy, preexponential factor, and the thermodynamic parameters such as enthalpy and entropy were estimated for uncatalyzed and catalyzed reactions using these three models. The process conditions were optimized for catalyzed and uncatalyzed reactions to obtain the maximum product yield by minimizing root mean square error of each experimental data using the MS-excel solver tool. Thus, this study reveals the high potential of an agro-waste, Cajanus cajan husk as raw material for the synthesis of catalyst. The results show that the E-R model is more appropriate for predicting the dynamic data of an esterification reaction, as the forward rate of reaction estimated using the E-R model are more modified than P-H and L-H models. 相似文献
16.
The electron donating properties of sulfated zirconia were studied from the adsorption of electron acceptors of various electron
affinity. The surface acidity and basicity of the oxides have also been determined by titration method using a set of Hammett
indicators. The data have been correlated with the catalytic activity of the oxide towards esterification of acetic acid usingn-butanol, reduction of cyclohexanol in 2-propanol and oxidation of cyclohexanol with benzophenone. 相似文献
17.
Esterification of carboxylic acids with alkyl halides can be efficiently catalyzed by tetrabutylammonium fluoride (TBAF) generated in situ from tetrabutylammonium hydrogensulfate (TBAHSO4) and KF·2H2O in THF. The general applicability and the characteristic feature of this approach has been amply demonstrated. 相似文献
18.
Edd A. Blekkan Kim A. Johnsen Thomas Løften 《Reaction Kinetics and Catalysis Letters》2005,86(1):149-155
Summary Platinum-promoted sulfated zirconia catalysts active in n-hexane isomerization were prepared in a one-step synthesis and characterized. The crystallinity and sulfur contents depend mainly on the calcination temperature. The stability of the sulphate in the presence of hydrogen is reduced by the presence of Pt. 相似文献
19.
疏水双功能介孔固体酸的合成及其在乙酸乙酯酯化反应中的应用 总被引:2,自引:0,他引:2
通过水热合成法一步合成了具有不同疏水基团-CH3 、-(CH3)2 和-(CH3)3的双功能介孔固体酸SBA-15-SO3H-(CH3)x催化剂。通过X射线粉末衍射(XRD)、N2吸脱附、元素分析等方法对催化剂进行了表征,并在乙酸乙酯酯化反应中进行催化性能评价。结果表明,随着疏水前驱体中甲基数的增加,样品的疏水性增强。SBA-15-SO3H-(CH3)x催化剂的催化活性随着疏水性的增强而提高,而具有较强疏水性的材料SBA-15-SO3H-(CH3)3在反应中具有较高的催化性能。以SBA-15-SO3H-(CH3)3为催化剂,酯化反应的最优条件为:温度为120℃,乙酸与乙醇摩尔比为4∶1,催化剂质量分数为1 %,反应时间为1h。在此条件下,乙醇的转化率和乙酸乙酯的选择性分别为93%和100%。 相似文献
20.
Sulfated zirconias were prepared using two kinds of amorphous zirconia gels, XZO 631 and 632 supplied by MEL Chemicals, and their thermal gravimetrical analyses were carried out. DTG of the former sample showed two peaks based on decomposition of the sulfate species on the surface, the first peak at 680 °C and the second broad one centered at 850 °C. The latter sample indicated only broad peak at 850 °C in the range from 700 to >1000 °C. The first peak for the former sample was ascribed to the decomposition of Zr(SO4)2 remained on the surface, and the broad one at 700 to >1000 °C for the both samples was attributed to the catalytically active species. The acidic character of sulfated zirconia calcined at 1000 °C was examined in acid-catalyzed reactions of cumene, ethylbenzene, and butane together with the adsorption heat of Ar, showing a solid acid with acidity higher than that of silica-alumina. It was indicated from the XPS analysis that the S species are composed of SO42−. The results led to a structural model of the active surface to be polysulfate species containing mainly three or four S atoms with two ionic bonds of SOZr in addition to coordination bonds of SO with Zr, the active site being Lewis sites on the S atoms. 相似文献