CuO-WO_3-ZrO_2的结构和性质对苯甲醛加氢反应催化性能的影响

采用共沉淀法制备了不同CuO和WO_3含量的CuO-WO_3-ZrO_2催化剂.利用X射线衍射(XRD)、扫描电子显微镜(SEM)、X射线荧光光谱(XRF)、N2气物理吸附、氢气程序升温还原(H2-TPR)、X射线光电子能谱(XPS)及程序升温脱附(TPD)等手段对催化剂的结构和表面性质进行了表征.结果表明,WO_3的引入可以调变ZrO_2的晶型,从而使催化剂的比表面积和孔径发生变化,促进CuO在催化剂表面的分散,并影响催化剂的酸碱性.在苯甲醛加氢制备苯甲醇反应中,以CuO质量分数为18%,WO_3质量分数为10%的CuO-WO_3-ZrO_2为催化剂时苯甲醛单程转化率达到92. 03%,产物苯甲醇的选择性为94. 76%.

CeO_2-ZrO_2-La_2O_3-Al_2O_3 composite oxide and its supported palladium catalyst for the treatment of exhaust of natural gas engined vehicles

Composite supports CeO2-ZrO2-Al2O3（CZA） and CeO2-ZrO2-Al2O3-La2O3（CZALa） were prepared by co-precipitation method. Palladium catalysts were prepared by impregnation and their purification ability for CH4, CO and NOx in the mixture gas simulated the exhaust from natural gas vehicles （NGVs） operated under stoichiometric condition was investigated. The effect of La2O3 on the physicochemical properties of supports and catalysts was characterized by various techniques. The characterizations with X-ray diffraction （XRD） and Raman spectroscopy revealed that the doping of La2O3 restrained effectively the sintering of crystallite particles, maintained the crystallite particles in nanoscale and stabilized the crystal phase after calcination at 1000 ℃. The results of N2-adsorption, H2-temperatnre-programmed reduction （H2-TPR） and oxygen storage capacity （OSC） measurements indicated that La2O3 improved the textural properties, reducibility and OSC of composite supports. Activity testing results showed that the catalysts exhibit excellent activities for the simultaneous removal of methane, CO and NOx in the simulated exhaust gas. The catalysts supported on CZALa showed remarkable thermal stability and catalytic activity for the three pollutants, especially for NOx. The prepared palladium catalysts have high ability to remove NOx, CH4 and CO, and they can be used as excellent catalysts for the purification of exhaust from NGVs operated under stoichiometric condition. The catalysts reported in this work also have significant potential in industrial application because of their high performance and low cost.

The Effect of Platinum on Stability of the B_2O_3/TiO_2-ZrO_2 Catalyst for Beckmann Rearrangement of Cyclohexanone Oxime

The addition of platinum over the B2O3/TiO2-ZrO2 remarkably enhanced its catalytic stability in the vapor phase Beckmann rearrangement of cyclohexanone oxime under the carder gas of H2. The content of coke deposited on catalyst surface was decreased from 1.92% over the B2O3/TiO2-ZrO2 to 1.14% over the platinum promoted B2O3/TiO2-ZrO2 after reaction of six hours. This result indicates that the platinum added on the B2O3/TiO2-ZrO2 catalyst plays an important role in reducing the coke formation on the catalyst surface.

Catalytic Partial Oxidation of Methane over Ni/CeO_2-ZrO_2-Al_2O_3

Nickel catalysts supported on CeO2-ZrO2-CeO2,ZrO2-Al2O3 and Al2O3 were prepared and characterized by means of X-ray diffraction（XRD）,BET areas,H2 temperature-programmed reduction（H2-TPR）,and X-ray photoelectron spectroscopy（XPS）.Through the test of catalytic partial oxidation of methane（CPOM）,Ni/CeO2-ZrO2-Al2O3 displayed the highest activity,which resulted from its largest BET area and best NiO dispersion.Furthermore,Ni/CeO2-ZrO2-Al2O3 maintained a long-time stability in CPOM,which was attributed to its best coking resistance among all the prepared catalysts.

Partial oxidation of methane on Ni/CeO_2-ZrO_2/γ-Al_2O_3 prepared using different processes

The influences of CeO2-ZrO2 and γ-Al2O3 mixing methods on the catalytic activity and stability of partial oxidation of methane （POM） were investigated over Ni/Ce0.7Zr0.3O2-Al2O3 catalysts. The catalysts were characterized by XRD, TPR, H2-chemsorption, and TG-DTA. For fresh catalysts, the results showed that the salt precursor mixing catalyst （ATOM） presented better performance than the catalysts prepared by the precipitator mixing method （MOL） and the powder mechanically mixing method （MECH）. The result of XRD suggested that the interaction between CeO2-ZrO2 and Al2O3 in ATOM sample was stronger than the others, which led to more lattice defects and thereby better initial activity. Moreover, the MECH sample had the best stability and the least coke deposition in 24 h stability tests. The results of TPR and H2-chemsorption indicated that the intimate contact of Ni-Al in MECH sample enhanced the ability of resisting coke deposition and metal sintering.

Effects of CuO-CeO₂Addition on Structure and Catalytic Properties of Three Way Catalysts

The noble metals (Pt, Pd, Rh) supported on Cu-Ce mixed oxides with γ-Al2O3 washcoat/FeCrAl substrate were investigated as catalytic performance of Three Way Catalysts (TWC) under simulated automotive exhaust feed gas. The structural, morphological features and catalytic activity were observed by X-ray diffractometry (XRD), scanning electron microscopy (SEM), Brunauer-Emmett-Teller (BET), X-ray photoelectron spectroscopy (XPS) and GC-TCD (Varian CP-4900). The catalytic performance of noble metals (Pt, Rh, Pd) supported on Cu-Ce mixed oxides with γ-Al2O3 washcoat/FeCrAl substrate was be compared with noble metals (Pt, Rh, Pd) supported on Ce-Zr mixed oxides with γ-Al2O3 washcoat/FeCrAl substrate and only γ-Al2O3 washcoat/FeCrAl substrate at various stoichiometric ratio of oxygen. The results showed that the addition of Cu-Ce mixed oxides improved CO oxidation reaction at lower temperature during stable lambda of 1, the highest CO conversion of 99% is observed for the noble metals (Pt, Pd, Rh) support on Cu-Ce with γ-Al2O3 washcoat/FeCrAl substrate. The results also showed that, the addition of Cu-Ce mixed oxides promoted released oxygen, thus it improved strongly CO and C3H8 conversion at lean oxygen stoichiometric operation.

Catalytic combustion of toluene over Pd-based monolithic catalysts with a novel washcoat Ce_(0.8)Zr_(0.15)La_(0.05)O_δ

Two novel washcoats Ce0.8Zr0.15La0.05Oδ and Ce0.8Zr0.2O2 was prepared by an impregnation method, which acted as a host for the active Pd component to prepare Pd/Ce0.8Zr0.15La0.05Oδ/substrate and Pd/Ce0.8Zr0.2O2/substrate monolithic catalysts for toluene combustion. The washcoats was characterized by X-ray diffraction (XRD), Raman spectroscopy, Brunauner-Emmett-Teller (BET), and H2-temperature-programmed reduction (H2-TPR). The result indicated that both the washcoats had strong vibration-shock resistance according to ultrasonic test. Doping La3+ into CeO2-ZrO2 solid solution could generate more oxygen vacancies, and could inhibit the sinter of CeO2-ZrO2 solid solution when calcined at high temperatures (800, 900 and 1000 °C). The washcoat Ce0.8Zr0.15La0.05Oδ had much better redox properties. The reductive temperature of Ce4+ species shifted to low temperature by 60 °C when the washcoats calcined at high temperatures (800, 900 and 1000 °C). The Pd/Ce0.8Zr0.15La0.05Oδ/substrate monolithic catalyst calcination at 500 °C had the best catalytic activity and the 95% toluene conversion at a temperature as low as 190 °C. When calcined at low temperature (500 and 700 °C), the catalytic activity has little improvement, however, when calcined at high temperature, the catalytic activity of Pd/Ce0.8Zr0.15La0.05Oδ/substrate monolithic catalysts had significant improvement. As catalyst washcoat, the Ce0.8Zr0.15La0.05Oδ had better thermal stability than the washcoat Ce0.8Zr0.2O2, the developed Pd/Ce0.8Zr0.15La0.05Oδ/ substrate monolithic catalyst in this work was promising for eliminating Volatile organic compounds.

Synthesis of neodymium modified CeO_2-ZrO_2-Al_2O_3 support materials and their application in Pd-only three-way catalysts

Ce-Zr-Al-Nd2O3 （CZAN） support materials were prepared by co-precipitation and impregnation methods, respectively. They were characterized by X-ray diffTaction （XRD）, low temperature nitrogen adsorption-desorption, oxygen pulsing technique, H2-temperamre programmed reduction （H2-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 Nd2O3, and the addition of Nd203 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 Ce3＋ 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.

Effects of La_2O_3 contents on the Pd/Ce_(0.8)Zr_(0.2)O_2-La_2O_3 catalysts for methanol decomposition

The catalytic behaviors of Pd （1.4 wt.%） catalysts supported on CeO2-ZrO2 promoted with La2O3 were investigated for methanol decomposition. The measurements of inductively coupled plasma emission spectroscopy （ICP）, N2 adsorption-desorption （BET）, powder X-ray diffraction （XRD）, X-ray photoelectron spectroscopy （XPS）, temperature-programmed reduction （TPR） and oxygen storage capacity （OSC） were used to characterize the properties of catalysts. The catalysts＇ activities were tested in a fixed bed continuous flow reactor operating under atmospheric pressure. The Pd/Ce0.8Zr0.2O2-5 wt.%La2O3 catalyst exhibited the best activity. The reasons for this were twofold： （1） doping of La improved effectively textural properties of CeO2-ZrO2 oxygen storage materials, and （2） Pd/Ce0.8Zr0.2O2-5 wt.%La2O3 possessed super oxygen storage property and reducibility due to the existence of lattice defect oxygen or mobile oxygen, which helped to re-oxidize zerovalent Pd0 to a partly oxidized Pdδ＋. By introducing 5 wt.%La2O3, the specific surface area of the sample increased, but declined if further increasing the content of La2O3 to 10 wt.%.