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Heterogeneous catalyst

Yuqi Sun, Wei Liu, Miao Tian, Liguo Wang, Zhongpeng Wang
The redox pretreatment of samples is one of the crucial ways of altering the catalytic properties of the supported noble metal materials in many heterogeneous reactions. Here, H₂-reducing pretreatment is reported to enhance the thermal stability of Au-CeO₂ catalysts prepared by the deposition⁻precipitation method and calcination at 600 °C for CO oxidation. In order to understand the improved activity and thermal stability, a series of techniques were used to characterize the physico-chemical changes of the catalyst samples...
October 12, 2018: Materials
Lobna Mansouri, Chedly Tizaoui, Sven-Uwe Geissen, Latifa Bousselmi
Several Advanced Oxidation Processes (AOPs) including O3 /H2 O2 , O3 /TiO2 , O3 /activated carbon (AC), O3 /Al2 O3 , O3 /Fe2+ /H2 O2 and UV/TiO2 have been investigated and compared for the removal of diethyl phthalate (DEP), an endocrine disrupting compound, in aqueous solutions. Hydroxyl radicals were the main species responsible for DEP degradation and this was supported by computational chemistry calculation, scavenger experiments, and LC/MS/MS analysis. The change of the abundance of reaction products over time was determined...
October 6, 2018: Journal of Hazardous Materials
Yimei Zhang, Zhuang Chen, Lincheng Zhou, Panpan Wu, Yalong Zhao, Yuxian Lai, Fei Wang
In this study, a multi-component catalyst, β-cyclodextrin (β-CD) and reduced graphene oxide (rGO) co-modified Fe3 O4 , was fabricated via one-pot solvothermal method and used as a synergistic catalyzer for Bisphenol A (BPA) removal. The study found that catalytic reactions of BPA followed the pseudo-first-order kinetics model, and the correlation rate constants (kobs ) were calculated. Compared with Fe3 O4 @β-CD (0.02173 min-1 ), Fe3 O4 /rGO (0.09735 min-1 ) and Fe3 O4 (0.01666 min-1 ), the composite (0...
October 9, 2018: Environmental Pollution
Md Manik Mian, Guijian Liu
Novel TiO2 /Fe/Fe3 C-biochar composite, as a heterogeneous catalyst, has been synthesized by a single-step route, where sewage sludge (SS) and different ratios of nanoparticles (NPs: Fe and Ti) impregnated with chitosan using coagulation and flocculation techniques for subsequent thermal decomposition at 800 °C. The physiochemical properties of samples have been characterized thoroughly and employed in methylene blue (MB) degradation tests. It was found that NPs ratio and chitosan support have significant influences on the properties and catalytic activity of catalysts...
October 6, 2018: Chemosphere
Joshua A Buss, Masanari Hirahara, Yohei Ueda, Theodor Agapie
A new series of low-valent dinuclear molybdenum complexes bearing phosphido or phosphinidene bridging ligands was synthesized as a structural model of heterogeneous metal phosphide catalysts. Addition of acid to a monocationic Mo2-μ-P complex results in phosphide protonation, affording a dicationic Mo2-μ-PH species. Alternatively, reaction of an isoelectronic Mo2-μ-P precursor with LiBEt3H gives a Mo2H-μ-P complex. Mixing these species, one bearing a Mo-H and the other a P-H bond results in facile H2 production at room temperature...
October 12, 2018: Angewandte Chemie
Ayda Elhage, Bowen Wang, Nancy Marina, M Luisa Marin, Menandro Cruz, Anabel E Lanterna, Juan C Scaiano
Heterogeneous catalysis presents significant advantages over homogeneous catalysis such as ease of separation and reuse of the catalyst. Here we show that a very inexpensive, manageable and widely available material - glass wool - can act as a catalyst support for a number of different reactions. Different metal and metal oxide nanoparticles, based on Pd, Co, Cu, Au and Ru, were deposited on glass wool and used as heterogeneous catalysts for a variety of thermal and photochemical organic reactions including reductive de-halogenation of aryl halides, reduction of nitrobenzene, Csp3 -Csp3 couplings, N-C heterocycloadditions (click chemistry) and Csp-Csp2 couplings (Sonogashira couplings)...
September 7, 2018: Chemical Science
Palak Bansal, Anoop Verma, Charu Mehta, Vikas Kumar Sangal
In this study, degradation of a pharmaceutical drug, Phenazone (PNZ) has been carried out via heterogeneous photocatalysis, photo-Fenton and in-situ dual process (photocatalysis + photo-Fenton) in suspension and fixed-mode under artificial UV-A as well as under natural solar radiations. Waste material such as foundry sand (FS) was exploited as a supplement for iron in case of photo-Fenton reaction. The distinct processes including photocatalysis and photo-Fenton were found to be competent for the degradation of PNZ as both processes revealed an almost 90-95% removal of PNZ after 180 min of UV irradiations...
October 8, 2018: Journal of Environmental Management
Md Estak Ahmed Ahmed, Samir Chattopadhyay Chattopadhyay, Lianke Wang, Deborah Brazzolotto, Debajyoti Pramanik Pramanik, Dmitry Aldakov Aldakov, Jennifer Fize Fize, Adina Morozan, Marcello Gennari, Carole Duboc, Abhishek Dey, Vincent Artero
[NiFe]-hydrogenase enzymes are efficient catalysts for H2 evolution but their synthetic models have not been reported to be active under aqueous conditions, so far. Here we show that a close model of the [NiFe]-hydrogenase active site can work as a very active and stable heterogeneous H2 evolution catalyst under mildly acid aqueous conditions. Entry in catalysis is a NiIFeII complex, with electronic structure analogous to the Ni-L state of the enzyme, corroborating the mechanism modification recently proposed for [NiFe]-hydrogenases...
October 11, 2018: Angewandte Chemie
Xuerui Tian, Lin Hou, Jiaojiao Wang, Xing Xin, Heng Zhang, Yuanyuan Ma, Yali Wang, Lina Zhang, Zhangang Han
New Na-bridged phosphomolybdates (H2en)12[{Na0.8K0.2(H2O)}2{Na[Mo6O12(OH)3(HPO4)2(PO4)2]2}2]·7H2O (1), (H2bpp)2[{Sr2(H2O)4}{Na3(H2O)10}{Na[Mo6O12(OH)3(HPO4)3(PO4)]2}]·2H2O (2), and (H2bpp)6 [{Ca2(H2O)4}{Na2(H2O)4}{Na[Mo6O12(OH)3(HPO4)3(PO4)]2}2] (3) (en = ethylenediamine, bpp = 1,3-bi(4-pyridyl)propane), were synthesized by a hydrothermal method and characterized. Single-crystal X-ray diffraction analysis revealed that the three hybrids were composed of fully reduced 'hourglass-shaped' {Na[PV4MoV6X31]2}n- (X = O/OH) clusters and N-containing organic cations...
October 11, 2018: Dalton Transactions: An International Journal of Inorganic Chemistry
Jan-E Bäckvall, Man-Bo Li, Daniels Posevins, Karl Gustafson, Cheuk-Wai Tai, Andrey Shchukarev, Youai Qiu
A highly selective and efficient oxidative carbocyclization-borylation of enallenols catalyzed by palladium immobilized on amino-functionalized siliceous mesocellular foam (Pd-AmP-MCF) was developed for diastereoselective cyclobutenol synthesis. The heterogeneous palladium catalyst, which has both Pd(0) and Pd(II) atoms on the nanoparticle surface, can be recovered and recycled without any observed loss of activity or selectivity. The high diastereo-selectivity of the reaction is proposed to ori-ginate from a directing effect of the enallenol hydroxyl group...
October 11, 2018: Chemistry: a European Journal
Markus Leutzsch, Andrew J Sederman, Lynn F Gladden, Michael D Mantle
Understanding the reactivity and mass transport properties of porous heterogenous catalysts is important for the development of new materials. Whereas MRI has previously been used to correlate chemical kinetics and hydrodynamics under operando conditions, this paper demonstrates that a modern benchtop NMR spectrometer is a suitable alternative to obtain diverse reaction information in porous heterogeneous catalyst materials on a smaller scale. Besides information about the chemical conversion within the pores, it can also be used to study changes of surface interaction by T1 /T2 NMR relaxometry techniques and changes in mass transport by PFG NMR from a single chemical reaction...
October 6, 2018: Magnetic Resonance Imaging
Yu-Hong Hu, Cong-Xue Liu, Jian-Cheng Wang, Xiu-Hui Ren, Xuan Kan, Yu-Bin Dong
A chiral ionic liquid (CIL) moiety of a l-pyrrolidin-2-ylimidazole-decorated homochiral UiO-68-type metal-organic framework, UiO-68-CIL (1), was successfully prepared by the combination of a new premodified chiral CIL ligand (H2 L-CIL) and ZrCl4 via a solvothermal method. The TiO2 -loaded TiO2 @UiO-68-CIL (2) was prepared by impregnating 1 in a toluene solution of Ti(OPri )4 and sequential in situ hydrolysis. The obtained 2 can be a bifunctional asymmetric heterogeneous catalyst to successfully promote the one-pot Morita-Baylis-Hillman reaction starting from aromatic alcohols in a tandem way...
October 9, 2018: Inorganic Chemistry
Changda Li, Haitong Tang, Yu Fang, Zhifeng Xiao, Kunyu Wang, Xiang Wu, Helin Niu, Chengfeng Zhu, Hong-Cai Zhou
In this study, we demonstrate a bottom-up assembly of a monomeric copper complex and a two-dimensional (2-D) heterometallic metal-organic framework (MOF) from a carboxylate-functionalized tridentate Schiff base ligand and metal ions. The obtained 2-D MOF features a unique bimetallic copper center which is different from its monometallic precursor and acts as an efficient heterogeneous catalyst for the Friedel-Crafts reaction and Henry reaction. The MOF catalyst shows a remarkably superior activity compared to its homogeneous counterparts in a wide range of substrates...
October 9, 2018: Inorganic Chemistry
Mahdiyeh Rashki Ghaleno, Mansour Ghaffari-Moghaddam, Mostafa Khajeh, Ali Reza Oveisi, Mousa Bohlooli
A bioinspired iron(III)porphyrinic Zr-MOF, PCN-222(Fe), was modified by post-synthetic cluster metalation with iron(III) chloride, as a cheap, earth-abundant, and environmentally friendly metal precursor, towards formation a new multifunctional MOF, namely Fe@PCN-222(Fe). The MOF consists of bimetallic (Zr-oxo-Fe) nodes linked by Fe(III)porphyrin struts. The cluster metalation and pre-activation treatment of PCN-222(Fe) were performed cooperatively using the FeCl3 . The respective MOF was characterized through various techniques, such as FT-IR, PXRD, ICP-AES, BET surface area, SEM, UV-Vis DRS, TGA/DSC, PL, and XPS analyses...
September 29, 2018: Journal of Colloid and Interface Science
Yan-Xia Zhao, Zi-Yu Li, Yuan Yang, Sheng-Gui He
The increasing supply of natural gas has created a strong demand for developing efficient catalytic processes to upgrade methane, the most stable alkane molecule, into value-added chemicals. Currently, methane conversion in laboratory and industry is mostly performed under high-temperature conditions. A lot of effort has been devoted to exploring chemical entities that are able to activate the C-H bond of methane at lower temperatures, preferably room temperature. Gas phase atomic clusters with limited numbers of atoms are ideal models of active sites on heterogeneous catalysts...
October 5, 2018: Accounts of Chemical Research
Mahmoud Nasrollahzadeh
Carbon‒carbon (C‒C) and carbon‒heteroatom (C‒X) bonds that form via transition-metal-catalyzed processes have been extensively used in the organic synthesis and preparation of natural products and important compounds such as heterocycles, biologically active molecules, and dendrimers. Among the most significant catalysts, magnetic nanoparticles-supported palladium complexes are very effective, versatile, and heterogeneous catalysts for a wide range of C‒C and C‒X coupling reactions due to their reusability, thermal stability, and excellent catalytic performance...
October 4, 2018: Molecules: a Journal of Synthetic Chemistry and Natural Product Chemistry
Sukanya Ramaraj, Mani Sakthivel, Shen-Ming Chen, Kuo-Chuan Ho
Metal chalcogenides with large active sites have been received great attention as an excellent catalyst due to their hierarchical structural properties. Here, we have demonstrated the synthesis of ytterbium-doped molybdenum selenide (YbMoSe2 ) in the form of two-dimensional nanosheets by using a simple ultrasonic method. The formation of the crystal phase of prepared YbMoSe2 nanosheets was studied by using the selective characterization techniques. The reported HRTEM confirmed that the introduction of heterogeneous spin of Yb with MoSe2 creates the lattice distortion...
September 21, 2018: Ultrasonics Sonochemistry
Juan M Venegas, William P McDermott, Ive Hermans
Light olefins such as ethylene and propylene form the foundation of the modern chemical industry, with yearly production volumes well into the hundreds of millions of metric tons. Currently, these light olefins are mainly produced via energy-intensive steam cracking. Alternatively, oxidative dehydrogenation (ODH) of light alkanes to produce olefins allows for lower operation temperatures and extended catalyst lifetimes, potentially leading to valuable process efficiencies. The potential benefits of this route have led to significant research interest due to the wide availability of natural gas from shale deposits...
October 4, 2018: Accounts of Chemical Research
Chelsea Vickers, Feng Liu, Kento Abe, Orly Salama-Alber, Meredith L Jenkins, Christopher Mk Springate, John E Burke, Stephen G Withers, Alisdair B Boraston
Fucoidans are chemically complex and highly heterogeneous sulfated marine fucans from brown macro algae. Possessing a variety of physicochemical and biological activities, fucoidans are used as gelling and thickening agents in the food industry, and have anticoagulant, antiviral, antitumor, antibacterial, and immune activities. Although fucoidan-depolymerizing enzymes have been identified, the molecular basis of their activity on these chemically complex polysaccharides remains largely uninvestigated. In this study, we focused on three glycoside hydrolase family 107 (GH107) enzymes, MfFcnA and two newly identified members, P5AFcnA and P19DFcnA, from a bacterial species of the genus Psychromonas...
October 3, 2018: Journal of Biological Chemistry
Jinhu Dong, Qiang Fu, Zheng Jiang, Bingbao Mei, Xinhe Bao
Strong metal-support interaction (SMSI) has been regarded as one of the most important concepts in heterogeneous catalysis, which has been almost exclusively discussed in metal/oxide catalysts. Here, we show that gold/molybdenum carbide (Au/MoCx) catalysts are featured by highly dispersed Au overlayers, strong interfacial charge transfer between metal and support, and excellent activity in low temperature water-gas-shift reaction (LT-WGSR), demonstrating the active SMSI state. Subsequent oxidation treatment results in strong aggregation of Au nanoparticles, weak interfacial electronic interaction, and poor LT-WGSR activity...
October 3, 2018: Journal of the American Chemical Society
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