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Heterogeneous catalyst

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https://www.readbyqxmd.com/read/30121522/cu-ii-schiff-base-covalently-anchored-to-mil-125-ti-nh-2-as-heterogeneous-catalyst-for-oxidation-reactions
#1
Saba Daliran, Andrea Santiago-Portillo, Sergio Navalón, Ali Reza Oveisi, Mercedes Álvaro, Ramin Ghorbani-Vaghei, Davood Azarifar, Hermenegildo García
MIL-125(Ti)-NH2 has been modified by reaction of salicylaldehyde with the terephthalate amino groups to form a salicylideneimine that act as ligand of Cu2+ . The success of the postsynthetic modification was assessed by FTIR spectroscopy of the MIL-125(Ti)-NH2 -Sal-Cu and by analysis by 1 H NMR spectroscopy of the organic linkers upon dissolution of MIL-125(Ti)-NH2 -Sal-Cu. In comparison with parent MIL-125(Ti)-NH2 and MIL-125(Ti)-NH2 -Sal, that exhibit a poor activity, the presence of the Cu-Schiff base complex in MIL-125(Ti)-NH2 -Sal-Cu catalyst for the oxidation of 1-phenylethanol by tert-butylhydroperoxyde (TBHP, 3 eq...
August 1, 2018: Journal of Colloid and Interface Science
https://www.readbyqxmd.com/read/30121459/iron-catalyzed-wet-air-oxidation-of-biomethanated-distillery-wastewater-for-enhanced-biogas-recovery
#2
Ganesh M Bhoite, Prakash D Vaidya
In the present work, catalytic wet air oxidation (WAO) technique was applied to biomethanated spent wash from a local sugar factory. This wash water exhibited high biological oxygen demand (BOD5  = 8100 mg/L) and chemical oxygen demand (COD = 40,000 mg/L). The objectives of oxidative pre-treatment were two-fold, viz. efficient treatment of wash water and enhanced biogas recovery. For the catalytic oxidation process, two iron-based heterogeneous catalysts were employed, viz. Fe2 O3 and Fe/C. To synthesize the Fe/C catalyst, activated carbon (AC) support was modified either by thermal treatment or chemical treatment with nitric acid; accordingly, the catalyst was named as Fe/AC-T or Fe/AC-N...
August 16, 2018: Journal of Environmental Management
https://www.readbyqxmd.com/read/30118203/recent-developments-in-the-scope-practicality-and-mechanistic-understanding-of-enantioselective-hydroformylation
#3
Anna C Brezny, Clark R Landis
In the nearly 80 years since catalytic hydroformylation was first reported, hundreds of billions of pounds of aldehyde have been produced by this atom efficient one-carbon homologation of alkenes in the presence of H2 and CO. Despite the economy and demonstrated scalability of hydroformylation, the enantioselective process (asymmetric hydroformylation, AHF) currently does not contribute significantly to the production of chiral aldehydes and their derivatives. Current impediments to practical application of AHF include low diversity of chiral ligands that provide effective rates and selectivities, limited exploration of substrate scope, few demonstrations of efficient flow reactor processes, and incomplete mechanistic understanding of the factors that control reaction selectivity and rate...
August 17, 2018: Accounts of Chemical Research
https://www.readbyqxmd.com/read/30118118/rhodium-calix-4-pyrrole-and-rhodium-tetraphenyl-porphyrin-preparation-surface-grafting-and-their-catalytic-application-in-nitro-benzene-reduction
#4
K Anjali, M Ahmed, J Christopher, A Sakthivel
Rhodium containing macromolecules calix[4]pyrrole (RhCP) and tetraphenyl porphyrin (RhTPP) were prepared and grafted on the surface of functionalised molecular sieve materials. 1H and 13C NMR, CHNS and mass spectral analyses were used for the structural elucidation of homogeneous organometallic complexes.1H NMR and CHNS analyses confirm the formation of calix[4]pyrrole (CP) and tetraphenyl porphyrin (TPP). The introduction of rhodium ions into the macromolecule is well evident from the disappearance of the 1H NMR signal characteristic of N-H proton (7...
August 17, 2018: Dalton Transactions: An International Journal of Inorganic Chemistry
https://www.readbyqxmd.com/read/30112528/the-integration-of-experiment-and-computational-modelling-in-heterogeneously-catalysed-ammonia-synthesis-over-metal-nitrides
#5
Constantinos D Zeinalipour-Yazdi, Justin S J Hargreaves, Said Laassiri, C Richard A Catlow
In this perspective we present recent experimental and computational progress in catalytic ammonia synthesis research on metal nitrides involving a combined approach. On this basis, it suggested that the consideration of nitrogen vacancies in the synthesis of ammonia can offer new low energy pathways that were previously unknown. We have shown that metal nitrides that are also known to have high activity for ammonia synthesis can readily form nitrogen vacancies on their surfaces. These vacancies adsorb dinitrogen much more strongly than the defect-free surfaces and can efficiently activate the strong N-N triple bond...
August 16, 2018: Physical Chemistry Chemical Physics: PCCP
https://www.readbyqxmd.com/read/30111675/p-toluenesulfonic-acid-based-deep-eutectic-solvent-as-transesterification-catalyst-for-biodiesel-production
#6
Wei Liu, Fang Wang
In this study, acidic deep eutectic solvents (DESs) have been studied as catalyst in transesterification of soybean oil with methanol to produce biodiesel. p-Toluenesulfonic acid-based deep eutectic solvent (P-DES), composed of p-toluenesulfonic acid and choline chloride (1:3, mol/mol), was found to be an efficient transesterification catalyst for biodiesel production. The optimum conditions for the transesterification process were as follows: 8% P-DES catalyst, 8:1 molar ratio of methanol to oil, reaction temperature of 110℃ and 2 h reaction time...
August 14, 2018: Journal of Oleo Science
https://www.readbyqxmd.com/read/30110534/c-h-activation-and-proton-transfer-initiate-alkene-metathesis-activity-of-tungsten-iv-oxo-complex
#7
Ka Wing Chan, Erwin Lam, Vincenza D'Anna, Florian Allouche, Carine Michel, Olga Safonova, Philippe Sautet, Christophe Copéret
In alkene metathesis, while group 6 (Mo or W) high-oxidation state alkylidenes are accepted to be key reaction intermediates for both homogeneous and heterogeneous catalysts, it has been proposed that low valent species in their +4 oxidation state can serve as pre-catalysts. However, the activation mechanism for these latter species - generating alkylidenes - is still an open question. Here, we report the syntheses of tungsten (IV)-oxo bisalkoxide molecular complexes stabilized by pyridine ligands, WO(OR)2py3 (R = CMe(CF3)2 (2a), R = Si(OtBu)3 (2b) and R = C(CF3)3 (2c); py = pyridine) and show that upon activation with B(C6F5)3, they display comparable alkene metathesis activities as W(VI)-oxo alkylidenes...
August 15, 2018: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/30110402/cerium-promoted-v-g-c-3-n-4-as-highly-efficient-heterogeneous-catalysts-for-the-direct-benzene-hydroxylation
#8
Cheng Wang, Liya Hu, Meiyin Wang, Bin Yue, Heyong He
A series of Ce x -V-g-C3 N4 catalysts with different cerium content were synthesized by a facile co-assembly method. Compared with pure V-g-C3 N4 catalyst, the addition of cerium facilitated the high dispersion of vanadium species as well as the benzene adsorption ability of the corresponding catalysts. Also, the existence of cerium promoted the partial reduction of vanadium species, which improved the redox property of vanadium species as the active centres. The Ce x -V-g-C3 N4 catalysts showed considerably improved activity in the benzene hydroxylation reaction compared with V-g-C3 N4 catalyst...
June 2018: Royal Society Open Science
https://www.readbyqxmd.com/read/30110147/controlling-electrons-and-protons-through-theory-molecular-electrocatalysts-to-nanoparticles
#9
Sharon Hammes-Schiffer
The development of renewable energy sources that are environmentally friendly and economical is of critical importance. The effective utilization of such energy sources relies on catalysts to facilitate the interconversion between electrical and chemical energy through multielectron, multiproton reactions. The design of effective catalysts for these types of energy conversion processes requires the ability to control the localization and movement of electrons and protons, as well as the coupling between them...
August 15, 2018: Accounts of Chemical Research
https://www.readbyqxmd.com/read/30109779/room-temperature-synthesis-of-covalent-organic-framework-cof-lzu1-nanobars-in-co2-water-solvent
#10
Fanyu Zhang, Jianling Zhang, Bingxing Zhang, Xiuniang Tan, Dan Shao, Jinbiao Shi, Dongxing Tan, Lifei Liu, Jiaqi Feng, Buxing Han, Guanying Yang, Lirong Zheng, Jing Zhang
To develop facile, rapid, low-energy and environmentally benign routes for the synthesis of covalent organic frameworks (COFs) is of great interest. Here we demonstrate for the first time the utilization of CO2-dissolved water as a solvent for the room-temperature synthesis of COF. The as-synthesized COF-LZU1 particles combine advantages of good crystallinity, nanoscale size and high surface area, which have shown to be promising support for heterogeneous catalysts. Moreover, the CO2-assisted method is versatile for the room-temperature synthesis of Cu-COF-LZU1...
August 15, 2018: ChemSusChem
https://www.readbyqxmd.com/read/30108716/cu-ii-immobilized-on-fe-3-o-4-aptms-dfx-nanoparticles-an-efficient-catalyst-for-the-synthesis-of-5-substituted-1-h-tetrazoles-with-cytotoxic-activity
#11
Faezeh Taghavi, Mostafa Gholizadeh, Amir Sh Saljooghi, Mohammad Ramezani
Cu(ii) immobilized on deferasirox loaded amine functionalized magnetic nanoparticles (Cu(ii)/Fe3 O4 @APTMS-DFX) as a novel magnetically recyclable heterogeneous catalyst is able to catalyze the [3 + 2] cycloaddition reactions of various organic nitriles with sodium azide. Using this method, a series of 5-substituted-1 H -tetrazoles under mild conditions in DMSO were prepared. The reaction involves mild reaction conditions with efficient transformation capability. The developed catalyst could be easily separated by applying an external magnetic field...
October 1, 2017: MedChemComm
https://www.readbyqxmd.com/read/30106509/low-temperature-continuous-flow-dehydration-of-xylose-over-water-tolerant-niobia-titania-heterogeneous-catalysts
#12
Carmen Moreno-Marrodan, Pierluigi Barbaro, Stefano Caporali, Filippo Bossola
The sustainable conversion of vegetable biomass-derived feeds to useful chemicals requires innovative routes matching environmental and economical criteria. The approach herein pursued is the synthesis of water-tolerant, unconventional solid acid monolithic catalysts based on a mixed niobia-titania skeleton building up a hierarchical open-cell network of meso and macropores, and tailored for use under continuous flow conditions. The materials were characterized by spectroscopic, microscopy and diffraction techniques showing a reproducible, isotropic structure and an increasing Lewis / Brønsted acid sites ratio with increasing Nb content...
August 14, 2018: ChemSusChem
https://www.readbyqxmd.com/read/30106499/perspectives-of-microwaves-enhanced-heterogeneous-catalytic-gas-phase-processes-in-flow-systems
#13
REVIEW
Andrzej Stankiewicz, Farnaz Eghbal Sarabi, Abdul Baubaid, Peng Yan, Hakan Nigar
The paper discusses the currents status and future perspectives of the utilization of microwaves, as a selective and locally controlled heating method, in heterogeneous catalytic flow reactors. Various factors related to the microwave-catalyst interaction and the design of microwave-assisted catalytic reactor systems are analyzed. The analysis clearly shows the superiority of the traveling-wave systems over the mono-mode and multi-mode cavity-based systems when it comes to the design and application of microwave flow reactors at relevant production scales...
August 14, 2018: Chemical Record: An Official Publication of the Chemical Society of Japan ... [et Al.]
https://www.readbyqxmd.com/read/30106487/architectural-designs-and-synthetic-strategies-of-advanced-nanocatalysts
#14
REVIEW
Guowu Zhan, Ping Li, Hua Chun Zeng
Advanced nanocatalysts with high compositional and structural tailorability have emerged as a new class of heterogeneous catalysts exhibiting many new technical merits over their conventional counterparts. Generally, preparation of such catalysts involves the integration of catalyst components with compositional, size, and shape controls into a larger material system in order to bring along collective and synergetic effects of individual components. Herein, a brief review of architectural designs and synthetic strategies for making these nanocatalysts is presented...
August 14, 2018: Advanced Materials
https://www.readbyqxmd.com/read/30105302/subsurface-catalysis-mediated-selectivity-of-dehydrogenation-reaction
#15
Weiting Cai, Rentao Mu, Shenjun Zha, Guodong Sun, Sai Chen, Zhi-Jian Zhao, Hao Li, Hao Tian, Yu Tang, Franklin Feng Tao, Liang Zeng, Jinlong Gong
Progress in heterogeneous catalysis is often hampered by the difficulties of constructing active architectures and understanding reaction mechanisms at the molecular level due to the structural complexity of practical catalysts, in particular for multicomponent catalysts. Although surface science experiments and theoretical simulations help understand the detailed reaction mechanisms over model systems, the direct study of the nature of nanoparticle catalysts remains a grand challenge. This paper describes a facile construction of well-defined Pt-skin catalysts modified by different 3d transition metal (3dTM) atoms in subsurface regions...
August 2018: Science Advances
https://www.readbyqxmd.com/read/30104623/creating-solvation-environments-in-heterogeneous-catalysts-for-efficient-biomass-conversion
#16
Qi Sun, Sai Wang, Briana Aguila, Xiangju Meng, Shengqian Ma, Feng-Shou Xiao
Chemical transformations are highly sensitive toward changes in the solvation environment and solvents have long been used to control their outcome. Reactions display unique performance in solvents like ionic liquids or DMSO, however, isolating products from them is cumbersome and energy-consuming. Here, we develop promising alternatives by constructing solvent moieties into porous materials, which in turn serve as platforms for introducing catalytic species. Due to the high density of the solvent moieties, these porous solid solvents (PSSs) retain solvation ability, which greatly influences the performance of incorporated active sites via concerted non-covalent substrate-catalyst interactions...
August 13, 2018: Nature Communications
https://www.readbyqxmd.com/read/30103128/reutilization-of-iron-sludge-as-heterogeneous-fenton-catalyst-for-the-degradation-of-rhodamine-b-role-of-sulfur-and-mesoporous-structure
#17
Sheng Guo, Zhixiong Yang, Zhipan Wen, Hussain Fida, Gaoke Zhang, Jinyi Chen
Fenton process has gained considerable interest for its application in water treatment. However, the removal of iron sludge which generated during the process makes this method complex and uneconomical. In this study, we report a novel way of modifying iron sludge and use it as heterogeneous Fenton catalyst for the degradation of dye wastewater. It was found that after calcination at 600 °C, the iron sludge (Fe-600) exhibited much enhanced catalytic performance (99%) toward rhodamine B (RhB) in comparison with iron sludge without calcination (10%) in the presence of H2 O2 ...
August 4, 2018: Journal of Colloid and Interface Science
https://www.readbyqxmd.com/read/30102805/surface-modification-on-pd-tio2-hybrid-nanostructures-toward-highly-efficient-h2-production-from-catalytic-formic-acid-decomposition
#18
Panyiming Liu, Zijian Cai, Yang You, Hao Huang, Shuangming Chen, Chao Gao, Zeming Qi, Ran Long, Junfa Zhu, Li Song, Yujie Xiong
Metallic nanocrystals with well-designed surface structures represent a class of model systems for revealing the fundamental physical and chemical processes involved in heterogeneous catalysis. Herein, we show that surface modification can be utilized as an efficient strategy for controlling the surface electronic state of catalysts and thus a knob for tuning their catalytic activity. As model catalysts, the surface-modified Pd tetrahedrons-TiO2 nanostructures modified with different foreign atoms show the varied activity in the catalytic decomposition of formic acid toward H2 production...
August 13, 2018: Chemistry: a European Journal
https://www.readbyqxmd.com/read/30101253/probing-acid-sites-in-solid-catalysts-with-pyridine-uv-vis-spectroscopy
#19
Marjolein E Z Velthoen, Sophie Nab, Bert M Weckhuysen
Solid acids hold widespread applications in the field of heterogeneous catalysis. In this work, we present pyridine UV-Vis spectroscopy as a novel and promising tool to study the acidic properties of such solid acids. It was found that upon interaction with acid sites, the electronic properties of pyridine change significantly. Monitoring of consecutive adsorption and desorption of pyridine revealed absorption bands in the UV-Vis region characteristic for (a) pyridinium ions formed on Brønsted acid sites, (b) pyridine coordinated to Lewis acid sites, (c) pyridine hydrogen-bonded to surface hydroxyl groups, and (d) physisorbed pyridine...
August 13, 2018: Physical Chemistry Chemical Physics: PCCP
https://www.readbyqxmd.com/read/30098083/tuning-gold-nanoparticles-with-chelating-ligands-for-highly-efficient-electrocatalytic-co2-reduction
#20
Zhi Cao, Samson B Zacate, Xiaodong Sun, Jinjia Liu, Elizabeth M Hale, William P Carson, Sam B Tyndall, Jun Xu, Xingwu Liu, Xingchen Liu, Chang Song, Jheng-Hua Luo, Mu-Jeng Cheng, Xiaodong Wen, Wei Liu
We report the capped chelating organic molecules as a design principle for tuning heterogeneous nanoparticles for electrochemical catalysis. Gold nanoparticles (AuNPs) functionalized with a chelating tetradentate porphyrin ligand show a 110-fold enhancement, compared to the oleylamine-coated AuNP, in current density for electrochemical reduction of CO2 to CO in water at an overpotential of 340 mV with Faradaic efficiencies (FEs) of 93%. These catalysts also show excellent stability without deactivation, <5% productivity loss, within 72 hours of electrolysis...
August 10, 2018: Angewandte Chemie
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