查看更多>>摘要：The storage of hydrogen in liquid organic hydrogen carriers (LOHCs) represents a safe and easy to handle storage solution for energy from renewable sources. Dibenzyltoluene (H0-DBT)/perhydro-dibenzyltoluene (H18-DBT) is a promising LOHC system due to its low flammability, wide liquid range and high storage density for hydrogen. However, this LOHC system requires high temperature heat (typically > 250 ?) for hydrogen release, which lowers the efficiency of the storage cycle if no appropriate source of waste heat is available. This disadvantage can be mitigated by transfer of the hydrogen onto an acceptor molecule such as acetone at mild temperatures, forming isopropanol which can be used as fuel in direct fuel cell concepts or represents a valuable chemical product. Herein, we present the development of an active and selective platinum on silica (Pt/SiO2) catalyst for the transfer hydrogenation of acetone using perhydro-dibenzyltoluene as the sole source of hydrogen. Relevant catalyst design parameters, such as the optimal pore size, Pt loading, reduction and oxidation temperatures/ times, are identified and their influence on the catalyst morphology and performance is discussed.
查看更多>>摘要：The surface reactive oxygen species over Y2O3-ZrO2 supports were tuned by regulating the interaction between Y and Zr via modulating the zirconium precursors. It was revealed that the content of the surface adsorbed oxygen species (SAOS) over the catalyst with ZrO2 precursor was the highest, followed by the catalysts with Zr(OH)(4) and ZrO(NO3)(2)center dot 2H(2)O precursors. The difference of the Y-Zr interaction influenced the reactive oxygen species and the support structure and morphology. However, Ni dispersion was determined by the existence of the isolated Y2O3 due to the enhanced metal-support interaction. High Ni dispersion and abundant surface adsorbed oxygen species were beneficial to promote CH4 and CO2 reactivity. Nevertheless, CH4 dissociation facilitated by the SAOS was more remarkable than CO2 activation at low temperature. Thus, the improvement of the SAOS on carbon-resistant ability of the catalyst was only achieved at high temperature through balancing the carbon formation and elimination.
查看更多>>摘要：A thorough catalytic combustion toward diluted ethylene oxide (EO) is demonstrated. The Pt active phase and CeO2 support were selected to introduce a synergistic effect. As a result, a superior catalytic activity and less severe coking trend were observed on the Pt/CeO2 catalyst when compared with another widely-used Pt/Al2O3 catalyst. The XPS spectra and H-2-TPR profiles evidenced that the Pt/CeO2 catalyst has both stronger metal support interaction and more abundant oxygen vacancies, which is believed at the heart of its excellent performance. Finally, the degradation pathways of EO were explored by in-situ DRIFTS. The weak H2O affinity of Pt/ CeO2 catalyst can inhibit the polycondensation reaction and result in the favorable degradation of EO. In contrast, abundant hydroxyl species were present on the hydrophilic Pt/Al2O3 catalyst surface, which may serve as acid sites and complicate the EO degradation, and therefore various side products and carbon deposits would appear in this case.
查看更多>>摘要：We explored here the possibility to use CO desorption kinetics monitored by IR spectroscopy as a tool to characterize the mixing of Au and Pt atoms at the surface of supported nanoparticles. CO desorption of CO monitored at 50 C showed that a bimetallic sample exhibited an intermediate behavior between those of monometallic Au and Pt samples, reflecting the alloyed nature of the nanoparticles. Our data also show that alumina-supported Au nanoparticles led to the formation of surface carbonates at 50 ?, possibly formed through Boudouard reaction (2 CO -> C + CO2), in contrast to the case of the Pt-based sample.
查看更多>>摘要：Four types of alkali metals Li, Na, K and Cs carbonate doped CuMgCe catalysts were prepared by an incipient wetness impregnation method, and the effect of alkali metals doping on the catalytic performance of catalyst for isobutanol synthesis from syngas was studied. Only the doping of K and Cs improved isobutanol selectivity, and the catalytic performance of K-CMC was better. All the catalysts characterized by XRD, BET, SEM, TEM, XPS, H-2- TPR, CO-TPD, CO2-TPD and NH3-TPD to further reveal the effect of alkali metals on catalysts for isobutanol synthesis. We found that the alkali metals doping reduced the reducibility of the catalysts, but increased the strength and density of basic sites and reduced the density of acidic sites, thereby leading to diverse catalytic performance of the catalysts for isobutanol synthesis. Compared with K-CMC, the insufficient performance of Cs-CMC was attributed to CO2 oxidation of Cu and CO2 neutralization of basic sites.
查看更多>>摘要：Ligand-coordinated supported catalysts (LCSCs) with highly-dispersed metal centers are of growing interest to bring the high selectivity and metal utilization efficiency of isolated, well-defined metal centers to a solid support for recyclability and stability. Pt LCSCs with bidentate N-based ligands have shown high activity, selectivity, and stability in hydrosilylation catalysis. Here, we tuned Pt LCSCs with carboxylic acid-based ligands as "anchoring ligands" with bidentate N-based ligand or as "coordination ligand." X-ray photoemission spectroscopy and inductively coupled plasma mass spectrometry were performed after the test reaction, hydrosilylation of 1octene, to evaluate the leaching of Pt. Using trimesic acid (TMA) as the "anchoring ligand" reduced Pt leaching from 34% after only 1 batch to ~25% after 4 batches. Using TMA as the "coordination ligand" creates a catalyst with 7 times higher turnover number than previous LCSCs. Two other carboxylic acid-based ligands were explored, both creating active and selective Pt hydrosilylation LCSCs.
查看更多>>摘要：A series of Pd/gamma-Al(2)O(3 & nbsp;)with different degrees of sulfur poisoning have been successfully prepared by in-situ thermal decomposition of (NH4)(2)SO4. The influence of sulfur poisoning on toluene combustion was evaluated. The samples were characterized by XRD, N-2 adsorption/desorption, HRTEM, FT-IR, TG, XPS, NH3-TPD and H-2- TPR. The results indicated that the no-poisoned Pd/gamma-Al2O3 showed the highest activity, which was attributed to the cooperation of Pd0 and Pd2+ species. However, all sulfur-poisoned catalysts showed a decline in activity, which was quantitatively related to the amount of (NH4)(2)SO4. It was found that the Pd0 active sites were more easily contaminated by sulfur species than the Pd2+ active sites, resulting in the deactivation of the catalysts. In addition, gamma-Al2O3 also reacted with sulfur to produce aluminum sulfur, which led to a significant increase in the strong acid site of the catalyst, while no beneficial effect was observed during our study.
查看更多>>摘要：Nowadays, MnO2-based catalysts have been widely applied in environmental fields, especially the removal of HCHO at room temperature. However, the moisture resistance of the catalyst is still a challenge. In this study, a series of MnTix/gamma-Al2O3/Al catalysts were prepared by the methods of redox precipitation and impregnation, which showed excellent HCHO removal efficiency under humid conditions. When the catalyst accumulatively treated ca. 25 ppm of HCHO, there was still a HCHO conversion of 87.5% and the activity can be restored by washing and drying. DFT calculations, XPS, and TG results showed that Ti-modification could inhibit the adsorption of physisorbed water on the catalyst surface, thereby weakening the competitive adsorption between H2O and HCHO. This study provides a feasible strategy for the removal of HCHO under humid conditions.
NSTL
Elsevier