Xiqiang Pan

Superior catalytic performance of Ce1−xBixO2−δ solid solution and Au/Ce1−xBixO2−δ for 5-hydroxymethylfurfural conversion in alkaline aqueous solution

Porous Bi-doped ceria (Ce1−xBixO2−δ solid solution) was prepared by the easy citrate method and then used as a supporting material for Au nanoparticles (NPs) obtained by deposition–precipitation. In the presence of O2, Ce1−xBixO2−δ (0.08 ≤ x ≤ 0.5) efficiently catalyzed the conversion of 5-hydroxymethylfurfural (HMF) to 5-hydroxymethyl-2-furancarboxylic acid (HFCA) and 2,5-bishydroxymethylfuran (BHMF) in alkaline aqueous solution without degradation of HMF. The excellent catalytic activity was attributed to the oxygen activation and hydride transfer enhanced by Bi doping and the large amount of oxygen vacancies. After Au NPs were supported on Ce1−xBixO2−δ (x ≤ 0.2), the presence of Auδ+ facilitated the activation of the C–H bond in the hydroxymethyl group and then the production of 2,5-furandicarboxylic acid (FDCA) as an end product, inhibiting the generation of BHMF.

Hydrothermal Method Prepared Ce-P-O Catalyst for the Selective Catalytic Reduction of NO with NH3 in a Broad Temperature Range

Selective catalytic reduction of NOx with ammonia (NH3-SCR) is a widely used process for the abatement of NOx from flue gases and exhaust gases of diesel trucks. The well-known commercial catalysts used for this process are V2O5-WO3/TiO2 or V2O5-MoO3/TiO2 which function within a relatively narrow temperature window of 300–400 8C. As the temperature rises above 400 8C, V-based catalysts exhibit a rapid decrease in activity and selectivity in the reduction of NOx due to the oxidation of SO2 into SO3. [2] Furthermore, the emissions of toxic vanadium lead to health problems. In addition, deactivation by poisoning is another problem because flue gases contain metal oxides (e.g. , K2O) that deactivate V-based catalysts. Therefore, alternative NH3-SCR catalysts with only nontoxic components and stable under harsh operating conditions are required. Low-temperature SCR catalysts, such as amorphous MnOx, [5] Fe–Mn–Ox, [6] MnOx–CeO2, [7] Mn/TiO2, [8] are urgently needed for the abatement of NOx from flue gases to avoid reheating of the gas and thus decrease the capital cost. In the medium temperature range, Fe-based catalysts, such as Fe2O3– WO3/ZrO2, [9] and crystallite iron titanate, exhibit excellent SCR activity. However, these catalysts regularly have problems with low N2 selectivity, H2O and SO2 deactivation, and especially the loss of activity at high temperature and high space velocity. For the high temperature range, some zeolite catalysts, such as Fe-ZSM-5 reported by Long et al. and Carja et al. , have shown highly catalytic performance in the range of 400– 500 8C. However, their applications are greatly restricted by poor hydrothermal stability of the zeolite support. A comprehensive overview of the NH3-SCR reaction mechanism shows that both surface acidity and redox property are necessary for the NH3-SCR reaction. Herein, several metal phosphate catalysts containing different multivalent ions, (M–P–O; M = Cu , Fe + , Mn + , Ce), were prepared. The most promising catalyst, Ce-P-O, is emphasized herein due to its high deNOx activity. The results showed that Ce-P-O(h), prepared by a hydrothermal method (see the Supporting Information), is a novel and efficient catalyst for NH3-SCR with NO conversions above 90 % within the range of 200–550 8C. For comparison, the Ce-P-O catalyst was also prepared by a coprecipitation method and denoted as Ce-P-O(c). Figure 1 shows the comparison of deNOx activities of Ce-P-O catalysts as a function of reaction temperature. Ce-P-O catalysts prepared by hydrothermal and coprecipitation methods exhibited different deNOx performance in low temperatures

A novel PdNi/Al2O3 catalyst prepared by galvanic deposition for low temperature methane combustion

Galvanic deposition method was used to prepare the Pd/Ni-Al2O3-GD catalyst for the combustion of methane under lean conditions. The new catalyst and compared catalysts (Pd/Al2O3-IW, Pd-Ni/Al2O3-IW, Pd/Ni-Al2O3-IW) prepared by incipient wetness impregnation were characterized by N2-physisorption, XRD and TEM to clarify particle size and size distribution of palladium species. Combined O2-TPD and XPS results with the catalytic data, it shows that the surface palladium species with low valence exhibits better combustion performance due to their stronger interaction with support. The results indicate that the galvanic deposition method is an effective route to prepare efficient catalyst for methane combustion, and it also provides useful information for improving the present commercial catalyst.

Investigation of the Redispersion of Pt Nanoparticles on Polyhedral Ceria Nanoparticles

Redispersion of platinum nanoparticles (Pt NPs) on ceria is an important route for catalyst regeneration and antisintering. Here, we investigate the redispersion of Pt on ceria nanoparticles with defined surface planes including cubes ({100}) and octahedra ({111}). It is observed that Pt redispersion takes place only on ceria cubes in an alternating oxidation and reduction atmosphere. A quicker alternation rate is beneficial for such redispersion. On the basis of our experimental results and understandings toward this process, we proposed that the redispersion takes place at the moment of alternation of oxidation and reduction.

A Novel Ce-P-O Catalyst for the Selective Catalytic Reduction of NO with NH3

A novel Ce-P-O catalyst for the selective catalytic reduction of NO with NH3 was synthesized. The Ce-P-O catalyst was calcined at 500 °C and showed higher deNOx activity (NO conversion > 90%) with the temperature range of 300–550 °C and at GHSV = 20 000 h−1. The NO conversion was not significantly affected by the presence of H2O and SO2. By comparison with the commercial V-W-Ti catalyst, the Ce-P-O catalyst exhibited better resistance to deactivation due to K2O poisoning.

BiMnO3 Perovskite Catalyst for Selective Catalytic Reduction of NO with NH3 at Low Temperature

A perovskite was used for selective catalytic reduction of NO with NH3 (NH3-SCR) at low temperature in the presence of excess oxygen. The BiMnO3 perovskite catalyst showed high activity in NH3-SCR at 100-240 degrees C. Experiment and DFT calculation showed that more Lewis acid sites and a high concentration of surface oxygen on BiMnO3 as compared with LaMnO3 were responsible for its better performance. In addition, BiMnO3 was also resistant to water vapor and a mixture of H2O and SO2.

Influence of electronic effect on methane catalytic combustion over PdNi/Al2O3

A series of PdNi/Al2O3 catalysts with different compositions was prepared by co-reduction method. The influence of Ni amount on the catalytic combustion of methane was studied. X-ray diffractometry and X-ray photo-electron spectroscopy were employed to characterize the dispersion and electronic state of the active phase. Temperature-programmed oxidation was carried out to study the thermal stability affected by Ni doping. It has been demonstrated that Ni addition changed particle size and oxidation state of PdOx. The results indicate that the promotion of Ni to the Pd/Al2O3 resulted from both size effect and electronic effect. In addition, the thermal stability of the Ni-doped catalysts were enhanced.

Synthesis of p-hydroxybenzaldehyde by liquid-phase catalytic oxidation of p-cresol over PVDF modified cobalt pyrophosphate

The influence of the wettability of a catalyst on the performance of the liquid phase oxidation of p-cresol was investigated. It was found that the surface hydrophobicity of a catalyst, which can be changed by modification with various loadings of polyvinylidene fluoride(PVDF), has a promotion effect on the catalytic performance. At the same time, the reaction parameters such as oxygen pressure, molar ratio of NaOH to p-cresol, reaction temperature and time on the catalytic performance in the liquid-phase oxidation of p-cresol were optimized. As a result, 10%(mass fraction) PVDF modified cobalt pyrophosphate gave the highest conversion of 94.2% of p-cresol with a selectivity of 94.4% for p-hydroxybenzaldehyde at 348 K and a molar ratio of 4:1 of NaOH/p-cresol and an oxygen pressure of 1.0 MPa for 3 h.