Co-reporter:Mao Ye, Yongfan Zhang, Lida Li, Rongrong Liu, Mei Qiu, Chengzhi Xu, Xiaohui Chen
Applied Surface Science 2015 Volume 346() pp:165-171
Publication Date(Web):15 August 2015
DOI:10.1016/j.apsusc.2015.03.084
Highlights
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We explored possible configurations of isolated copper(I) species on γ-Al2O3 (1 1 0) surface by DFT.
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The adsorption energy of thiophene and benzene were compared with the experimental results.
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Different adsorption modes of thiophene on the configurations were discussed.
Co-reporter:Yijun Pang; Xiaohui Chen;Dr. Chengzhi Xu;Yangjun Lei ; Kemei Wei
ChemCatChem 2014 Volume 6( Issue 3) pp:876-884
Publication Date(Web):
DOI:10.1002/cctc.201300811
Abstract
MoO3-Bi2SiO5/SiO2 catalysts with a Mo/Bi molar ratio of 5, prepared by a two-step hydrothermal and simple impregnation method, were investigated for the epoxidation of propylene by O2 and characterized by XRD, N2 absorption–desorption isotherms, thermogravimetric analysis (TGA), temperature-programmed reduction, NH3 temperature-programmed desorption (TPD), and IR, Raman, and X-ray photoelectron spectroscopy (XPS). On MoO3-Bi2SiO5/SiO2 with Mo/Bi=5 calcined at 723 K, a propylene conversion of 21.99 % and a propylene oxide selectivity of 55.14 % were obtained at 0.15 MPa, 673 K, and flow rates of C3H6/O2/N2=1/4/20 cm3 min−1. XRD, IR spectroscopy, and XPS results show that Bi2SiO5 and MoO3 are crystalline nanoparticles. NH3-TPD results indicate that the surface acid sites are necessary for the high catalytic activity. The results of TGA and N2 absorption–desorption isotherms reveal that a reasonable calcination temperature is 723 K. The reaction mechanism of propylene epoxidation on MoO3-Bi2SiO5/SiO2 catalysis is hypothesized to involve an allylic radical generated at the molybdenum oxide species and the activation of O2 at the bismuth oxide cations.
Co-reporter:Cheng-zhi XU, Mei-qin ZHENG, Keng CHEN, Hui HU, Xiao-hui CHEN
Journal of Fuel Chemistry and Technology (August 2016) Volume 44(Issue 8) pp:943-953
Publication Date(Web):1 August 2016
DOI:10.1016/S1872-5813(16)30042-1
In this work, the impact of CeOx doping on a TiO2-SiO2 supporter on the Ag based adsorptive desulfurization for China's standard diesel was studied. The dispersion and valence states of Ce, Ti and Ag species were characterized, and the impact of Ce doping was investigated. The results indicated that Ce species and Ti species were dispersed evenly on the surface of SiO2 via a novel co-impregnation method. Following CeOx doping, the Ag species were in the form of oxides (about 5 nm) instead of metallic Ag particles (about 35 nm), which is due to the large amount of coordinative unsaturated sites provided by the interaction between CeOx and TiO2, as well as the oxidation-reduction property of CeOx. The Ag in the active oxide state (Ag2O2) and dispersed evenly on the supporter could interact with sulfur compounds more favorably, and therefore showed a good performance in the adsorptive desulfurization. In both static batch and dynamic breakthrough desulfurization tests, Ag-CeOx/TiO2-SiO2 was proved to be a more efficient adsorbent compared with Ag-TiO2-SiO2. It was found that the desulfurization performance of Ag-TiO2-SiO2 exhibited an excellent improvement (22.5%) after being doped with CeOx. In the static equilibrium tests, the equilibrium sulfur capacity of Ag-CeOx/TiO2-SiO2 was up to 5.38 mg/g for CN-II diesel (sulfur content 952.9 mg/kg) and the sulfur content of the CN-IV diesel (sulfur content 39.0 mg/kg) after desulfurization was less than 10 mg/kg, which could meet the CN-V standard.
Co-reporter:Li-da LI, Cheng-zhi XU, Mei-qin ZHENG, Xiao-hui CHEN
Journal of Fuel Chemistry and Technology (August 2015) Volume 43(Issue 8) pp:990-997
Publication Date(Web):1 August 2015
DOI:10.1016/S1872-5813(15)30028-1
Ag/TiO2-B2O3-Al2O3 adsorbents with different B2O3 loadings (e.g. 5%–20% (w)) were prepared by impregnation. Static adsorption tests were carried out by contacting the adsorbents with commercial diesel containing 245.36 mg(S)/L sulfur at ambient conditions to investigate the adsorption desulfurization activity. The results show that Ag/TiO2-Al2O3 modified by B2O3 exhibits a great enhancement for the adsorption desulfurization activity. When B2O3 (15% (w)) was loaded, 2%Ag/4%TiO2-15%B2O3-Al2O3 (w) could achieve the best desulfurization activity with a saturation capacity of 2.36 mg(S)/g adsorbent. This is a significant achievement regarding the desulfurization efficiency, especially for commercial diesel without pretreatment. The effects of B2O3 on the textural properties, crystal structure and surface acidity properties of the adsorbent were studied by N2-physisorption, O2-chemisorption, X-ray diffraction (XRD), temperature-programmed desorption of ammonia (NH3-TPD), Fourier transform infrared spectrometer (FT-IR spectra) and 11B nuclear magnetic resonance (11B-NMR) techniques. Correlating the characterizations with the desulfurization activity, it is found that the adsorption desulfurization activity is well related with the amounts of weak acid sites on the adsorbents. B2O3 modification induces larger amounts of BO4 species and improves the surface weak acidity, resulting in a higher adsorption desulfurization activity.
