Zhenzhen Miao

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.

Aerobic oxidation of 5-hydroxymethylfurfural (HMF) effectively catalyzed by a Ce0.8Bi0.2O2−δ supported Pt catalyst at room temperature

The oxidation of 5-hydroxymethylfurfural (HMF) to 2,5-furandicarboxylic acid (FDCA) was efficiently catalyzed when Pt nanoparticles (NPs) were supported onto a Ce0.8Bi0.2O2−δ solid solution. 98% yield of FDCA was achieved within 30 min at room temperature and the catalyst was reused five times without much loss of FDCA selectivity. It is the first report on the oxidation of HMF, an alcohol and an aldehyde, effectively catalyzed by a ceria-based material supported Pt catalyst. The individual properties of the Pt NPs and the ceria-based support were retained and not affected after their combination. The superior oxygen activation ability of the Bi-doped ceria thoroughly changed the performance of the ceria supported Pt catalyst. Pt NPs were responsible for the formation of the Pt–alkoxide intermediate, followed by β-H elimination with the help of hydroxide ions. Bi-containing ceria accelerated the oxygen reduction process because of the presence of a large amount of oxygen vacancies and the cleavage of the peroxide intermediate promoted by bismuth. These specific functions were well incorporated during the catalytic oxidation cycle, leading to the generation of the highly efficient Pt/Ce0.8Bi0.2O2−δ catalyst for HMF oxidation at room temperature.

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.

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.

The redispersion behaviour of Pt on the surface of Fe2O3

The redispersion behaviour of Pt on ferric oxides under cyclic oxidizing/reducing conditions was observed and studied using several analysis techniques. Pt in a Pt/Fe2O3 catalyst sintered after treatment under a single oxidative or reductive atmosphere at 600 °C and the average size of the Pt nanoparticles increased from the original 3.2 nm to 6.8 and 14.6 nm, respectively. In contrast, the average size decreased to 1.1 nm when the catalyst was treated under an alternating oxidizing and reducing atmosphere. It is proposed that the Pt–O–Fe bond formed under an oxidative atmosphere and the related defects or oxygen vacancies formed under a reductive atmosphere play an important role during the redispersion of Pt. In addition, the effect of temperature on the redispersion of Pt is also noted and discussed.