Maochu Gong

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 yttria in Pt/TiO2 on sulfur resistance diesel oxidation catalysts: enhancement of low-temperature activity and stability

Compared to Pt/TiO2, yttria-doped Pt/TiO2 (Pt/TiO2–YOx) was found to efficiently improve the activity and stability as well as maintain the naturally excellent sulfur resistance of TiO2-based catalysts. The catalysts were prepared by using co-precipitation and impregnation methods, sequentially. The as-prepared catalysts were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), N2 adsorption–desorption, X-ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM). For Pt/TiO2–YOx catalysts, TEM images show that ultrafine platinum nanoparticles (<1 nm) with a narrow size distribution (0.31–1.29 nm) were dispersed on TiO2–YOx supports and XRD measurements confirm that yttria addition could lead to suppression of the anatase crystal growth and phase transition which could consequently enhance the platinum dispersion. SEM and nitrogen adsorption–desorption results further demonstrate that the presence of yttria could stabilize the porous structure and enlarge the specific surface area of TiO2. Hence, this work shows that yttria can act as a dispersion promoter and a structure stabilizer, which is beneficial to low-temperature DOC activity and stability.

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.

Cerium promotion on the hydrocarbon resistance of a Cu-SAPO-34 NH3-SCR monolith catalyst

CuCe-SAPO-34 (CuCe-x) catalysts with 3 wt% Cu and various content of Ce for selective catalytic reduction of NOx by NH3 (NH3-SCR) were prepared by a wet co-impregnation method. The activities of the CuCe-x catalysts were better than that of Cu-SAPO-34 (Cu). In addition, the hydrocarbon (HC) resistance of the CuCe-x catalysts was examined and compared to that of the Cu catalyst. The NH3-SCR performance after C3H6 poisoning of the CuCe-x catalysts was preferable to that of the Cu catalyst, since the C3H6 oxidation performance was improved by the addition of Ce. The XRD, UV-vis-DRS and H2-TPR results confirmed that the addition of Ce could inhibit the aggregation of CuO crystallites and increase the amount of isolated copper ions. Furthermore, the NH3-TPD and TGA results demonstrated that the addition of Ce decreased the amount and strength of strong acid sites, so that the amount of C3H6/O2 adsorption on the CuCe-x catalysts was lower than that on the Cu catalyst. Therefore, the activity and HC resistance of Cu-SAPO-34 was improved by the addition of Ce.

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.

Preparation of Ce0.65Zr0.35O2 by co-precipitation: The role of hydrogen peroxide

Abstract The effect of H2O2 on the properties of Ce0.65Zr0.35O2 was explored by treating cerium nitrate and zirconium nitrate with a mixed aqueous solution of ammonia and ammonia-carbonate in the presence/absence of H2O2. The resultant products were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), nitrogen adsorption/desorption, oxygen storage capacity (OSC) and H2-temperature-programmed reduction (H2-TPR). The presence of H2O2 was found to have profound effect on powder properties such as surface area, crystallite size of the samples. It was also shown that the addition of H2O2 favored the incorporation of Zr4+ into CeO2 lattice, which facilitated the formation of CeO2-ZrO2 solid solution, and enhanced the thermal stability of the samples. OSC and H2-TPR studies indicated that the use of H2O2 enhanced the OSC and redox properties. Catalytic activity tests showed that as a support, the Ce0.65Zr0.35O2 prepared in the presence of H2O2 was more suitable for three-way catalyst. The corresponding Pd-only three-way catalyst demonstrated outstanding performance: wide air to fuel operation window, low light-off and total conversion temperature for the conversion of C3H8, NO and CO.

Effects of ZnO content on the performance of Pd/Zr0.5Al0.5O1.75 catalysts used in lean-burn natural gas vehicles

Abstract Mixed oxides obtained by adding varying amounts of ZnO into Zr0.5Al0.5O1.75 were used as supports to prepare 1.5% Pd catalysts. The catalyst activity and H2O tolerances of the catalysts were evaluated in a gas mixture simulating the exhaust of lean-burn natural gas-fueled vehicles. The catalysts were further characterized by N2 adsorption-desorption, X-ray diffraction, H2 temperature programmed reduction and X-ray photoelectron spectroscopy. The catalytic activity was greatly influenced by ZnO contents in Zr0.5Al0.5O1.75 support. The catalyst containing 15% ZnO exhibited a light-off temperature and complete conversion temperature for CH4 in the absence of H2O of 278 and 314 °C, respectively; while these same values in the presence of H2O were 342 and 371 °C, respectively. These results indicate that this combination of materials offers excellent catalytic activity at low temperature and also exhibits significant H2O tolerance.

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.