Dang-guo Cheng

Nickel–platinum nanoparticles immobilized on graphitic carbon nitride as highly efficient catalyst for hydrogen release from hydrous hydrazine

Here we demonstrate that the combination of NiPt alloy nanoparticles with a graphitic carbon nitride (g-C3N4) support facilitates H2 production from hydrous hydrazine in an alkaline solution under moderate conditions. Of all the heterogeneous catalysts tested, Ni37Pt63/g-C3N4 shows superior catalytic performance with a maximum initial turnover frequency (TOF) of 570 h−1 at 323 K.

Reaction pathways of β-D-glucopyranose pyrolysis to syngas in hydrogen plasma: a density functional theory study.

In this work, density functional theory (DFT) was employed to investigate the reaction pathways of β-D-glucopyranose for better understanding the pyrolysis mechanism of cellulose in hydrogen plasma. Many possible reactions were considered, and the reaction enthalpies and activation energies of these reactions were calculated using density functional theory (DFT) with a Gaussian method of B3LYP and basic set of 6-31G(d,p). A most possible reaction pathway was brought up. According to this reaction pathway, the main products of cellulose pyrolysis in hydrogen plasma would be syngas, and few light hydrocarbons. CO mainly comes from the decomposition of aldehyde group, while H2 mainly comes from dehydrogenation processes. Active H in plasma are found to play a very important role in many reactions, and they can remarkably lower the energies needed for reactions.

Efficient hydrogen generation from formic acid using AgPd nanoparticles immobilized on carbon nitride-functionalized SBA-15

Bimetallic AgPd nanoparticles were successfully immobilized on graphitic carbon nitride (g-C3N4) functionalized SBA-15 for the first time by a facile co-reduction method. These catalysts were applied in the decomposition of formic acid. The dehydrogenation of formic acid is dependent on the composition of AgPd and the content of carbon nitride (CN). Among all of the AgPd/mCND/SBA-15 catalysts tested, the Ag10Pd90/0.2CND/SBA-15 catalyst exhibits highly superior performance for the decomposition of formic acid into high-quality hydrogen at 323 K with 100% hydrogen selectivity and a turnover frequency of 893 h−1, which is among the maximum values obtained at 323 K in this paper. The improved performance is a promising step towards the utilization of formic acid as a hydrogen storage material.

Synthesis of Pd nanoparticles supported on CeO2 nanotubes for CO oxidation at low temperatures

Developing efficient supported Pd catalysts and understanding their catalytic mechanism in CO oxidation are challenging research topics in recent years. This paper describes the synthesis of Pd nanoparticles supported on CeO2 nanotubes via an alcohol reduction method. The effect of the support morphology on the catalytic reaction was explored. Subsequently, the performance of the prepared catalysts was investigated toward CO oxidation reaction and characterized by Nitrogen sorption, X-ray diffraction, X-ray photoelectron spectroscopy, transmission electron microscopy, and CO-temperature-programmed desorption techniques. The results indicated that the catalyst of Pd on CeO2 nanotubes exhibits excellent activity in CO oxidation at low temperatures, due to its large surface area, the high dispersion of Pd species, the mesoporous and tubular structure of the CeO2-nanotube support, the abundant Ce3+, formation of Pd–O–Ce bonding, and enhanced metal–support interaction on the catalyst surface.

Simple strategies for fabrication of a periodic mesoporous aluminosilicate with crystalline walls.

An alkali-assisted cooperative assembly process of two different templating systems with aluminosilicate precursors is described. A highly ordered mesoporous zeolite with the 2D hexagonal symmetry mesospores and MFI zeolitic framework walls is synthesized. This method also allows the preparation of ZSM-5 with c- or b-axis-aligned mesopores. The materials have promising catalytic activities for organic reactions involving bulky molecules.

Studies on the structure and catalytic performance of S and P promoted Na-W-Mn-Zr/SiO2 catalyst for oxidative coupling of methane

Abstract A series of Na-W-Mn-Zr/SiO2 catalysts promoted by different contents of S or/and P were prepared and their catalytic performance for oxidative coupling of methane was investigated to clarify the effect of S and P on the Na-W-Mn-Zr/SiO2 catalyst. The catalysts were characterized by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). From the characterization results, it is found that the addition of S and P to the Na-W-Mn-Zr/SiO2 catalyst helps the formation of active phases, such as a-cristobalite, Na2WO4, ZrO2, and Na2SO4. Moreover, the addition of S and P increases the concentration of surface-active oxygen species by improving the migration of active components from the bulk phase to the surface of the catalyst. According to the activity test, impressive methane conversion and C2 hydrocarbons yield were obtained at a low temperature of 1023 K over the six-component Na-W-Mn-Zr-S-P/SiO2 catalyst, which contained 2 wt% S and 0.4 wt% P simultaneously. The deactivation of Na-W-Mn-Zr-S-P/SiO2 was due to the loss of surface active components.

Effect of manganese and potassium addition on CeO2-Al2O3 catalyst for hydrogenation of benzoic acid to benzaldehyde

Abstract A series of Mn/CeO2-Al2O3 and K/CeO2-Al2O3 catalysts for hydrogenation of benzoic acid to benzaldehyde were prepared to investigate the effect of Mn, K addition on CeO2-Al2O3 catalyst. X-ray diffraction (XRD) and H2-temperature-programmed reduction (H2-TPR) results suggested that the interaction between CeO2 and MnOx enhanced the reducibility of catalysts and therefore benzoic acid conversion. The addition of K increased the number of basic number on the catalyst which leads to a high selectivity to benzaldehyde, but excessive addition imposed negative effects on the catalyst performance. A Mn-K/CeO2-Al2O3 catalyst was developed and investigated in the reaction. The simultaneous addition of Mn and K enhanced not only the catalytic activity but also the capacity to resist the coke formation over catalyst.

Oxidative dehydrogenation of 1-butene over vanadium modified bismuth molybdate catalyst: an insight into mechanism

BiMoVx catalysts (x = 0–0.3) were prepared by co-precipitation method and investigated in the oxidative dehydrogenation (ODH) of 1-butene to 1,3-butadiene. The results show that the vanadium content has significant effects on the catalyst performance and BiMoV0.15 exhibits the superior activity. X-ray photoelectron spectroscopy (XPS) and temperature programmed re-oxidation (TPRO) indicate that the oxygen mobility of catalysts is one of crucial factors determining catalytic performance in ODH reaction. The mechanism of oxygen migration in ODH reaction is discussed and proposed.

Zeolite growth by synergy between solution-mediated and solid-phase transformations

Understanding of the crystal growth mechanism of zeolites is essential for rational design of zeolite materials with desired physical and chemical properties, but still remains elusive. This paper describes experimental findings of zeolite crystal evolution from sodium-rich hydrogels, revealing that the zeolite nucleation occurs at the equilibrated gel phase of the condensed primary aggregates precipitated from the dissolved (alumino)silicate species. The nuclei produced from the nucleation could be diffused into the liquid–solid interface of the equilibrated gel phase and the liquid phase. The zeolite growth therefore occurs through a synergistic mechanism of two growth processes: a solution-mediated process and a solid-state transformation. In the liquid phase and the liquid–gel (equilibrated gel) interface, the oriented aggregation governs the zeolite growth in early stages. The major driving force for the aggregation is the electrostatic force between the positively charged active Na+ and the negative charges of the (TO−) groups on the surface of the nuclei and growing nanocrystals. In the last few steps the crystal growth by the coalescence and the Ostwald rule becomes predominant.

Characterization and catalytic behavior of Na-W-Mn-Zr-S-P/SiO2 prepared by different methods in oxidative coupling of methane

Abstract Na-W-Mn-Zr-S-P/SiO 2 catalysts for oxidative coupling of methane (OCM) were prepared by incipient wetness impregnation, sol-gel and mixture slurry methods. The catalyst prepared by mixture slurry method showed the best catalytic performance among all samples. In addition, the effects of different addition sequences of Na, W, Mn, Zr, S and P on the catalytic performance were studied. The absence of Na before the addition of Mn and Zr in the catalysts preparation depressed the formation of the active phases of Mn 2 O 3 and ZrO 2 and decreased the activities of the catalysts significantly.