A series of tungsten promoted alumina supported nickel catalysts has been prepared for the carbon dioxide reforming of methane to synthesis gas. The catalysts have been characterized by means of XRD, TEM, and Laser R...A series of tungsten promoted alumina supported nickel catalysts has been prepared for the carbon dioxide reforming of methane to synthesis gas. The catalysts have been characterized by means of XRD, TEM, and Laser Raman spectroscopy. It is shown that the addition of tungsten to the nickel catalyst can stabilize the catalyst and increase the resistance to carbon deposition. Adding a suitable amount of tungsten can also increase the catalyst activity to be close to that of supported noble metal catalysts. The carburisation of the tungsten modified nickel catalyst decreases the catalyst activity at lower reaction temperatures(<1123K), but has no effect on the catalyst performance at higher reaction temperatures. The alumina supported nickel catalyst modified by 0.67%(mass fraction) WO_3 has the equivalent equilibrium constant of the dry reforming reaction to that of alumina supported 5%(mass fraction) Ru at 873 K, and also has a lower activation energy for dry reforming than the latter.展开更多
Nanocrystalline tungsten carbide thin films were fabricated on graphite substrates by plasma enhanced chemical vapor deposition （PECVD） at H2 and Ar atmosphere, using WF6 and CH4 as precursors. The crystal phase, st...Nanocrystalline tungsten carbide thin films were fabricated on graphite substrates by plasma enhanced chemical vapor deposition （PECVD） at H2 and Ar atmosphere, using WF6 and CH4 as precursors. The crystal phase, structure and chemical components of the films were characterized by X-ray diffraction （XRD）, scanning electron microscopy （SEM） and energy-dispersive spectrometer （EDS）, respectively. The results show that the film prepared at CH4/WF6 concentration ratio of 20 and at 800℃ is composed of spherical particles with a diameter of 20-35 nm. Electrochemical investigations show that the electrochemical real surface area of electrode of the film is large, and the electrode of the film exhibits higher electro-catalytic activity in the reaction of methanol oxidation. The designated constant current of the film catalyst is 123.6 mA/cm^2 in the mixture solution of H2SO4 and CH3OH at the concentration of 0.5 and 2.0 mol/L at 70℃, and the designated constant potential is only 0.306 V （vs SCE）.展开更多
Effect of reaction temperature and pressure on the metathesis reaction between ethene and 2-butene to propene was studied on the WO3/γ-Al2O3-HY catalyst. The activity is found to increase with elevated temperature an...Effect of reaction temperature and pressure on the metathesis reaction between ethene and 2-butene to propene was studied on the WO3/γ-Al2O3-HY catalyst. The activity is found to increase with elevated temperature and reaches a plateau at 150-240 ℃. After that, the activity undergoes a remarkable decrement at too high temperature. The effect of temperature is elucidated by the oxidation state of tungsten species. The evaluation results also indicate that the stability is dependent on this reaction parameter. Medium pressure （0.5-0.8 MPa） is favorable for stability, while atmospheric pressure or too high pressure （〉1.0 MPa） deteriorates the stability. For explanation, UV Vis, FT-IR, O2-TPO, and TG techniques are used to characterize the spent catalysts.展开更多
Pt/WO3/C nanocomposites with parallel WO3 nanorods were synthesized and applied as the cathode catalyst for proton exchange membrane fuel cells （PEMFCs）. Electrochemical results and single cell tests show that an en...Pt/WO3/C nanocomposites with parallel WO3 nanorods were synthesized and applied as the cathode catalyst for proton exchange membrane fuel cells （PEMFCs）. Electrochemical results and single cell tests show that an enhanced activity for the oxygen reduction reaction （ORR） is obtained for the Pt/WO3/C catalyst compared with Pt/C. The higher catalytic activity might be ascribed to the improved Pt dispersion with smaller particle sizes. The Pt/WO3/C catalyst also exhibits a good electrochemical stability under potential cycling. Thus, the Pt/WO3/C catalyst can be used as a potential PEMFC cathode catalyst.展开更多
The main problem of new crude oil reserves is the incipient increase of heavy crude oils in the American continent, i.e. USA, Mexico, Canada and Venezuela. These types of crude oils require several treatments before r...The main problem of new crude oil reserves is the incipient increase of heavy crude oils in the American continent, i.e. USA, Mexico, Canada and Venezuela. These types of crude oils require several treatments before refining. One of these treatments can be hydrocracking. In this petroleum refining process, it is possible to modify the heavy crude oils to light crude oils. In this paper, we try to use hydrocracking to improve the quality of raw heavy crude oil, through some chemical transformations C-H binding rupture using a catalyst containing active metals such as tungsten and zirconium (W-Zr). After the crude oil was hydrocracked in presence of this novel bimetallic catalyst, the hydrocracked products showed lower content of asphaltenes, resins, sulfur and nitrogen. Also positive changes in the viscosity of crude oil measured as a decreasing of this value were observed. The American Petroleum Institute (API) gravity was significantly increased 6 units. Consequently, all these changes confirmed that the upgrading of the heavy crude oil was successful.展开更多
Owing to the increasingly serious environmental issues caused by the sulfur burnt in fuel, desulfurization has become an important topic. In this work, an amphiphilic oxygen-defective tungsten oxide was synthesized by...Owing to the increasingly serious environmental issues caused by the sulfur burnt in fuel, desulfurization has become an important topic. In this work, an amphiphilic oxygen-defective tungsten oxide was synthesized by a colloidal chemistry method. The amphiphilic property and oxygen defects were well characterized, and the structure of the oxygen-defective tungsten oxide catalyst was investigated. In addition, the catalyst was employed in oxidative desulfurization system of fuel,and deep desulfurization was achieved. It was found that the very high oxidative desulfurization performance of oxygendefective tungsten oxide catalyst resulted from both the amphiphilic property and oxygen defects. This work can provide a strategy for preparation of highly active metal oxide catalysts with oxygen defects in oxidative desulfurization reaction of fuel.展开更多
A new type of complex solid superacid catalyst WO_3-ZrO_2-SO_4^(2-)with an acid strength H_0≤-16.04 was prepared by kneading Zr(OH)_4 or amorphous ZrO_2 with tungstic acid(H_2WO_4)(W/Zr=0.15),followed by exposing thi...A new type of complex solid superacid catalyst WO_3-ZrO_2-SO_4^(2-)with an acid strength H_0≤-16.04 was prepared by kneading Zr(OH)_4 or amorphous ZrO_2 with tungstic acid(H_2WO_4)(W/Zr=0.15),followed by exposing this complex hydroxides to 0.5 tool/L H_2SO_4,calcining in air at 700～800℃ for 3h.This catalyst possesses both strong Bronsted acidity and strong Lewis acidity experimentally showed by IR observation of pyridine absorbed on it.XPS and AES techniques were employed to examine the valence states of tungsten, zirconium,sulfur and their interactions.The structure of sulfur species was studied by infrared spectroscopy and a structure model of active site was proposed upon these results.展开更多
Pt-WO3 nanoparticles uniformly dispersed on Vulcan XC-72R carbon black were prepared by an ethylene glycol method.The morphology,composition,nanostructure,electrochemical characteristics and electrocatalytic activity ...Pt-WO3 nanoparticles uniformly dispersed on Vulcan XC-72R carbon black were prepared by an ethylene glycol method.The morphology,composition,nanostructure,electrochemical characteristics and electrocatalytic activity were characterized,and the formation mechanism was investigated.The average particle size was 2.3 nm,the same as that of Pt/C catalyst.The W/Pt atomic ratio was 1/20,much lower than the design of 1/3.The deposition of WO3·xH2O nanoparticles on Vulcan XC-72R carbon black was found to be very difficult by TEM.From XPS and XRD,the Pt nanoparticles were formed in the colloidal solution of Na2WO4,the EG insoluble Na2WO4 resulted in the decreased relative crystallinity and increased crystalline lattice constant compared with those of Pt/C catalyst and,subsequently,the higher specific electrocatalytic activity as determined by CV.The Pt-mass and Pt-electrochemically-active-specific-surface-area based anodic peak current densities for ethanol oxidation were 422.2 mA·mg-1Pt and 0.43 mA·cm-2Pt,1.2 and 1.1 times higher than those of Pt/C catalyst,respectively.展开更多
基金Supported by the National Natural Science Foundation of China
文摘A series of tungsten promoted alumina supported nickel catalysts has been prepared for the carbon dioxide reforming of methane to synthesis gas. The catalysts have been characterized by means of XRD, TEM, and Laser Raman spectroscopy. It is shown that the addition of tungsten to the nickel catalyst can stabilize the catalyst and increase the resistance to carbon deposition. Adding a suitable amount of tungsten can also increase the catalyst activity to be close to that of supported noble metal catalysts. The carburisation of the tungsten modified nickel catalyst decreases the catalyst activity at lower reaction temperatures(<1123K), but has no effect on the catalyst performance at higher reaction temperatures. The alumina supported nickel catalyst modified by 0.67%(mass fraction) WO_3 has the equivalent equilibrium constant of the dry reforming reaction to that of alumina supported 5%(mass fraction) Ru at 873 K, and also has a lower activation energy for dry reforming than the latter.
基金This work was supported by the National Natural Scmnce Foundation of China(Grant Nos.20276069,20476097)
文摘Nanocrystalline tungsten carbide thin films were fabricated on graphite substrates by plasma enhanced chemical vapor deposition （PECVD） at H2 and Ar atmosphere, using WF6 and CH4 as precursors. The crystal phase, structure and chemical components of the films were characterized by X-ray diffraction （XRD）, scanning electron microscopy （SEM） and energy-dispersive spectrometer （EDS）, respectively. The results show that the film prepared at CH4/WF6 concentration ratio of 20 and at 800℃ is composed of spherical particles with a diameter of 20-35 nm. Electrochemical investigations show that the electrochemical real surface area of electrode of the film is large, and the electrode of the film exhibits higher electro-catalytic activity in the reaction of methanol oxidation. The designated constant current of the film catalyst is 123.6 mA/cm^2 in the mixture solution of H2SO4 and CH3OH at the concentration of 0.5 and 2.0 mol/L at 70℃, and the designated constant potential is only 0.306 V （vs SCE）.
基金Financial support by National Natural Science Foundation of China (No. 20303019)National 973 Project of China (No.2003CB615802).
文摘Effect of reaction temperature and pressure on the metathesis reaction between ethene and 2-butene to propene was studied on the WO3/γ-Al2O3-HY catalyst. The activity is found to increase with elevated temperature and reaches a plateau at 150-240 ℃. After that, the activity undergoes a remarkable decrement at too high temperature. The effect of temperature is elucidated by the oxidation state of tungsten species. The evaluation results also indicate that the stability is dependent on this reaction parameter. Medium pressure （0.5-0.8 MPa） is favorable for stability, while atmospheric pressure or too high pressure （〉1.0 MPa） deteriorates the stability. For explanation, UV Vis, FT-IR, O2-TPO, and TG techniques are used to characterize the spent catalysts.
基金financially supported by the National Natural Science Fundation of China(No.51125007)the National Basic Research Program(No.2012CB215500)
文摘Pt/WO3/C nanocomposites with parallel WO3 nanorods were synthesized and applied as the cathode catalyst for proton exchange membrane fuel cells （PEMFCs）. Electrochemical results and single cell tests show that an enhanced activity for the oxygen reduction reaction （ORR） is obtained for the Pt/WO3/C catalyst compared with Pt/C. The higher catalytic activity might be ascribed to the improved Pt dispersion with smaller particle sizes. The Pt/WO3/C catalyst also exhibits a good electrochemical stability under potential cycling. Thus, the Pt/WO3/C catalyst can be used as a potential PEMFC cathode catalyst.
文摘The main problem of new crude oil reserves is the incipient increase of heavy crude oils in the American continent, i.e. USA, Mexico, Canada and Venezuela. These types of crude oils require several treatments before refining. One of these treatments can be hydrocracking. In this petroleum refining process, it is possible to modify the heavy crude oils to light crude oils. In this paper, we try to use hydrocracking to improve the quality of raw heavy crude oil, through some chemical transformations C-H binding rupture using a catalyst containing active metals such as tungsten and zirconium (W-Zr). After the crude oil was hydrocracked in presence of this novel bimetallic catalyst, the hydrocracked products showed lower content of asphaltenes, resins, sulfur and nitrogen. Also positive changes in the viscosity of crude oil measured as a decreasing of this value were observed. The American Petroleum Institute (API) gravity was significantly increased 6 units. Consequently, all these changes confirmed that the upgrading of the heavy crude oil was successful.
基金financial support by Students’ Platform for innovation and entrepreneurship training of Jiangsu Province (201810299008z)the National Nature Science Foundation of China (Nos. 21576122, 21722604, 21766007)+1 种基金Key Laboratory of Tropical Medicinal Plant Chemistry of Ministry of Education, Hainan Normal University (20150376)the Natural Science Foundation of Jiangsu Provincial Department of Education (17KJA150002)
文摘Owing to the increasingly serious environmental issues caused by the sulfur burnt in fuel, desulfurization has become an important topic. In this work, an amphiphilic oxygen-defective tungsten oxide was synthesized by a colloidal chemistry method. The amphiphilic property and oxygen defects were well characterized, and the structure of the oxygen-defective tungsten oxide catalyst was investigated. In addition, the catalyst was employed in oxidative desulfurization system of fuel,and deep desulfurization was achieved. It was found that the very high oxidative desulfurization performance of oxygendefective tungsten oxide catalyst resulted from both the amphiphilic property and oxygen defects. This work can provide a strategy for preparation of highly active metal oxide catalysts with oxygen defects in oxidative desulfurization reaction of fuel.
基金The project was financed by National Natural Science Foundation of China.
文摘A new type of complex solid superacid catalyst WO_3-ZrO_2-SO_4^(2-)with an acid strength H_0≤-16.04 was prepared by kneading Zr(OH)_4 or amorphous ZrO_2 with tungstic acid(H_2WO_4)(W/Zr=0.15),followed by exposing this complex hydroxides to 0.5 tool/L H_2SO_4,calcining in air at 700～800℃ for 3h.This catalyst possesses both strong Bronsted acidity and strong Lewis acidity experimentally showed by IR observation of pyridine absorbed on it.XPS and AES techniques were employed to examine the valence states of tungsten, zirconium,sulfur and their interactions.The structure of sulfur species was studied by infrared spectroscopy and a structure model of active site was proposed upon these results.
基金Funded by the National Basic Research Program of China (No. 2009CB220100)the Beijing Excellent Talent Support Program (No. 20071D1600300396)
文摘Pt-WO3 nanoparticles uniformly dispersed on Vulcan XC-72R carbon black were prepared by an ethylene glycol method.The morphology,composition,nanostructure,electrochemical characteristics and electrocatalytic activity were characterized,and the formation mechanism was investigated.The average particle size was 2.3 nm,the same as that of Pt/C catalyst.The W/Pt atomic ratio was 1/20,much lower than the design of 1/3.The deposition of WO3·xH2O nanoparticles on Vulcan XC-72R carbon black was found to be very difficult by TEM.From XPS and XRD,the Pt nanoparticles were formed in the colloidal solution of Na2WO4,the EG insoluble Na2WO4 resulted in the decreased relative crystallinity and increased crystalline lattice constant compared with those of Pt/C catalyst and,subsequently,the higher specific electrocatalytic activity as determined by CV.The Pt-mass and Pt-electrochemically-active-specific-surface-area based anodic peak current densities for ethanol oxidation were 422.2 mA·mg-1Pt and 0.43 mA·cm-2Pt,1.2 and 1.1 times higher than those of Pt/C catalyst,respectively.
基金supported by the National Basic Research Program of China(973 Program,2009CB226102)the National Natural Science Foundation of China(21376239,21306191,and 21176235)~~
