Yaoqiang Chen

Synthesis and Characterization of TiO2/YFeO3 and Its Photocatalytic Oxidation of Gaseous Benzene

利用共沉淀法和柠檬酸法制备YFeO3,并以其为载体,将TiO2溶胶负载在其表面,制备了复合光催化剂TiO2/YFeO3.在紫外灯的照射下,考察对气相苯的降解效果并利用N2吸附、X射线衍射（XRD）、拉曼光谱、X射线光电子能谱（XPS）、扫描电子显微镜（SEM）、透射电子显微镜（TEM）、UV-Vis漫反射光谱等手段对催化剂进行了表征.结果表明,以共沉淀法制备的YFeO3为载体的复合催化剂,180min内苯的降解率达到44.7%,表现出更好的光催化活性.两种方法制备的YFeO3均为斜方晶相,TiO2分散在载体的表面,并与YFeO3存在一定的相互作用;两种复合催化剂均具有较窄的带隙能.YFeO3 was prepared by coprecipitati on method and citric acid method, and TiO2/YFeO3 heterosystem photocatalysts were synthesized by loading TiO2 sol on the surface of YFeO3 via sol-gel method. Their photocatalytic activities were evaluated by the decomposition of gaseous benzene under UV light illumination. The prepared photocatalysts were characterized by nitrogen adsorption-desorption, X-ray diffraction (XRD), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and UV-Vis diffuse reflectance spectroscopy. Results revealed that the heterosystem photocatalysts prepared by coprecipitati on method showed higher activity, and the maximum conversion of benzene could reach 44.7% within 180 min. The YFeO3 samples prepared from coprecipitation method and citric acid method were absolutely in orthorhombic phase. The deposited titania was dispersed on the surface of carrier and a certain interaction existed between TiO2 and YFeO3. The two heterosystems photocatalysts had narrow band-gap energies.

Effect of Y on improving the thermal stability of MnOx-CeO2 catalysts for diesel soot oxidation

Abstract A series of MnO x -CeO 2 -Y 2 O 3 catalysts with different Y loadings (0, 1, 3, 6, and 10 wt%) were prepared by a co-precipitation method and investigated for NO x -assisted soot oxidation. The thermal stabilities of these catalysts were evaluated by treating them at 800 °C for 12 h under dry air flow. The catalysts were characterized by X-ray diffraction, N 2 adsorption-desorption, Raman spectroscopy, H 2 temperature-programmed reduction, oxygen storage capacity, NO temperature-programmed oxidation, X-ray photoelectron spectroscopy, and soot temperature-programmed oxidation. The addition of Y led to decreased BET surface areas and poor low-temperature reduction abilities and oxygen storage capacities, which affected NO and soot oxidation activities. However, after aging, the doping of Y had effectively enhanced the stability of the catalytic activities for NO and soot oxidations, where the addition of 6%–10% Y achieved the optimum result because the maximal soot oxidation rate temperature was increased by only 34–35 °C. Additionally, the catalytic activity and deactivation of MnO x -CeO 2 -containing catalysts were closely related to the presence of Mn 4+ and oxygen species on the surface.

Kerosene cracking over supported monolithic Pt catalysts: Effects of SrO and BaO promoters

Abstract The cracking of RP-3 fuel over supported monolithic Pt catalysts was studied at atmospheric pressure. The influence of BaO and SrO additives on the cracking reaction was examined. The effect of reaction time on the amount of carbon deposited during cracking was investigated. The catalysts were characterized using an automatic adsorption instrument (for Brunauer-Emmett-Teller analysis), temperature-programmed reduction, X-ray photoelectron spectroscopy, X-ray diffraction, and scanning electron microscopy. The results show that the total amount of gaseous products produced in catalytic cracking over a monolithic Pt/CA(CeO2-Al2O3)-La-Al2O3 (CA is a support) catalyst increased by 39.7% compared with that produced by thermal cracking. The addition of BaO or SrO improved the total amount of gaseous products by 25.6% and 37%, respectively. If BaO and SrO were simultaneously added to the monolithic Pt/CA-La-Al2O3 catalyst, the catalytic effect improved significantly, and the total amount of gaseous products increased by 96.5%. The addition of BaO or SrO effectively inhibits carbon deposition, and the synergistic effect of BaO and SrO additives improves the cracking reaction.

Monolith Manganese-Based Catalyst Supported on ZrO2-TiO2 for NH3-SCR Reaction at Low Temperature

Monolith catalysts were prepared using TiO2 and ZrO2-TiO2 as supports with MnO2 as active component and Fe2O3 as promoter. The catalytic activities at low temperature and stability at high temperature for selective catalytic reduction of NOx with NH3 (NH3-SCR) in the presence of excessive O2 were studied after the catalysts calcined at different temperatures. The catalysts were characterized by X-ray diffraction (XRD), specific surface area measurements (BET), oxygen storage capacity (OSC), and temperature programmed reduction (H2-TPR). The results indicated that the catalyst supported on ZrO2-TiO2 had excellent stability at high temperature, and possessed high specific surface area and oxygen storage capacity, and had strong redox property. The results of the catalytic activities indicated that the monolith manganese-based catalyst using ZrO2-TiO2 as support had evidently improved the activity of NH3-SCR reduction reaction at low temperature, and it showed great potential for practical application.以MnO2为活性组分,Fe2O3为助剂,制备了以TiO2及ZrO2-TiO2为载体的整体式催化剂.考察了它们在不同温度焙烧后应用于富氧条件下,NH3选择性催化还原（NH3-SCR）氮氧化物的低温反应性能和高温稳定性.用X射线衍射（XRD）实验、比表面积测定（BET）、储氧性能测定（OSC）及程序升温还原（H2-TPR）等方法对催化剂进行了表征.结果表明,以ZrO2-TiO2为载体的催化剂具有很好的高温热稳定性,并具有较高的比表面积和储氧能力,同时具有较强的氧化能力.催化剂的活性测试结果表明,以ZrO2-TiO2为载体的整体式锰基催化剂明显地提高了NH3-SCR反应的低温活性,具有良好的应用前景.

Influence of Mn/(Mn+Ce) Ratio of MnOx-CeO2/WO3-ZrO2 Monolith Catalyst on Selective Catalytic Reduction of NOx with Ammonia

Abstract A series of monolith MnO x -CeO 2 /WO 3 -ZrO 2 catalysts with different mass ratios of Mn/(Mn+Ce) were prepared and used for the selective catalytic reduction (SCR) of NO x with NH 3 in the presence of excess O 2 . The catalysts were characterized by N 2 adsorption, oxygen storage capacity, X-ray diffraction, X-ray photoelectron spectroscopy, NH 3 /NO temperature-programmed desorption, and H 2 temperature-programmed reduction. The best catalyst had the mass ratio of Mn/(Mn+Ce) = 0.5. It gave 90% NO x conversion in the range of 173-355 °C at the gas hourly space velocity of 10000 h −1 , and characterization results showed that a higher oxidation activity of NO to NO 2 , more surface Ce and Mn with a larger Ce 3+ /Ce 4+ ratio, lower NH 3 and NO desorption temperatures, and excellent redox ability were together responsible for its best NH 3 -SCR performance.

Novel promoting effects of cerium on the activities of NOx reduction by NH3 over TiO2-SiO2-WO3 monolith catalysts

Abstract A series of catalysts were prepared by doping different loadings of CeO2 over TiO2-SiO2-WO3 and used for the selective catalytic reduction of NOx by NH3. The experimental results showed that the selective catalytic reduction (SCR) performance and SO2-resistant ability of TiO2-SiO2-WO3 were greatly enhanced by the introduction of cerium. The catalyst containing 10% CeO2 showed the highest NO conversion in a wide temperature range and good N2 selectivity with broad operation temperature window at the gas hourly space velocity (GHSV) of 30000 h−1, which was a very promising catalyst for NOx abatement from diesel engine exhaust. The catalysts were characterized by X-ray diffraction (XRD), scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDS), N2 adsorption-desorption (BET) and X-ray photoelectron spectroscopy (XPS). The characterization results showed that the bigger pore radius, higher surface atomic concentration and dispersion of Ce and the abundant adsorbed oxygen on the surface of catalyst contributed to the best NH3-SCR performance of CeO2/TiO2-SiO2-WO3 catalyst containing 10% CeO2.

Synergetic effect of thermo-photocatalytic oxidation of benzene on Pt-TiO2/Ce-MnOx

Abstract Pt-TiO 2 /Ce-MnO x catalysts were obtained by depositing TiO 2 and platinum, respectively, on the Ce-Mn oxides prepared by co-precipitation method. The phases of CeO 2 and anatase TiO 2 were observed in the catalysts from X-ray diffraction (XRD) patterns. X-ray photoelectron spectroscopy (XPS) revealed that lattice oxygen and surface active oxygen were found to be the major components of O1s. The experiment results showed that the kinetic constant of thermo-photocatalysis was 7.6 times of the kinetic constant of single photocatalysis, and was 2.29 times of the kinetic constant sum of photocatalytic and thermal catalytic reaction.

Synthesis of neodymium modified CeO2-ZrO2-Al2O3 support materials and their application in Pd-only three-way catalysts

Abstract Ce-Zr-Al-Nd 2 O 3 (CZAN) support materials were prepared by co-precipitation and impregnation methods, respectively. They were characterized by X-ray diffraction (XRD), low temperature nitrogen adsorption-desorption, oxygen pulsing technique, H 2 -temperature programmed reduction (H 2 -TPR) and X-ray photoelectron spectroscopy (XPS). The Pd-only three-way catalysts (Pd-TWC) supported on these materials were prepared by incipient wetness method and studied by activity tests. The results demonstrated that the CZAN supports obtained by the two methods showed better structural, textural and redox properties than the CZA without Nd 2 O 3 , and the addition of Nd 2 O 3 improved the catalytic activity of TWC. Especially, the CZAN-i support prepared by impregnation method had better thermal stability and redox property. Meanwhile, the Pd/CZAN-i catalyst exhibited the best catalytic performance. XPS measurements indicated that the Nd-modified samples possessed more Ce 3+ and oxygen vacancies on the surface of samples, which led to a better redox property. The excellent redox property of support materials helped to improve the catalytic activity of TWC.

Effect of Zirconium Precursor on Performance of Pd/Ce0.45Zr0.45La0.1O1.95 Three-Way Catalyst

Abstract Three types of Ce 0.45 Zr 0.45 La 0.1 O 1.95 mixed oxides were prepared by H 2 O 2 -assisted precipitation using ZrOCO 3 , ZrO(NO 3 ) 2 , and Zr(NO 3 ) 4 as precursors. The Pd/Ce 0.45 Zr 0.45 La 0.1 O 1.95 three-way catalysts were prepared by the wet impregnation and characterized by X-ray diffraction (XRD), Raman spectroscopy, nitrogen adsorption, X-ray photoelectron spectroscopy (XPS), temperature-programmed reduction (TPR), and oxygen storage capacity. XRD and Raman results showed that the use of ZrOCO 3 or ZrO(NO 3 ) 2 gave a CeO 2 -ZrO 2 mixed oxide with a cubic phase of high thermal stability, while an extra t″-phase was observed in the aged Pd/Ce 0.45 Zr 0.45 La 0.1 O 1.95 catalyst prepared using Zr(NO 3 ) 4 . The activities of the three catalysts were evaluated using simulated exhaust gas under working conditions. The Pd/Ce 0.45 Zr 0.45 La 0.1 O 1.95 catalyst prepared using ZrOCO 3 as precursor gave the best activities for C 3 H 8 , CO, and NO conversion. The use of ZrOCO 3 as precursor was better suited for the formation of Ce 3+ and more favorable for the homogeneous insertion of Zr 4+ and La 3+ into the CeO 2 lattice, which resulted in better thermal stability and enhanced redox properties of the Pd/Ce 0.45 Zr 0.45 La 0.1 O 1.95 catalyst.

The performance of Pt/ZrxTixAl1–2xO2 as Kerosene cracking catalysts

Abstract ZrxTixAl1–2xO2 composite oxides for use as supports were prepared by coprecipitation and assessed with regard to their catalytic performance during the kerosene cracking reaction. The catalysts were characterized by N2 adsorption-desorption, scanning electron microscopy-energy dispersive spectrometry, X-ray diffraction, and temperature-programmed desorption (NH3-TPD). The results showed that a support composed of ZrO2:TiO2:Al2O3 in the ratio of 1:1:3 exhibited the highest surface area and pore volume, and had the strongest surface acidity and highest acidic density. Energy dispersive spectroscopy results showed that catalysts from which carbon deposits were removed by heating under oxygen changed very little, and additional experimental data confirmed that these catalysts are readily regenerated while retaining their functionality. The gaseous reaction products produced over ZrO2:TiO2:Al2O3 (1:1:3)-supported Pt catalyst generated during catalytic cracking was 2.1 times and 1.4 times higher than that obtained with thermal cracking at 650 °C and 700 °C, respectively. An examination of the catalytic performance of Pt catalyst supported on composite oxides calcined at 1000 °C for 5 h indicated that these materials lost much of their catalytic activity.