News Article | May 24, 2017
The catalyst rearranges propane, which contains three carbon atoms, into other molecules, such as butane (containing four carbons), pentane (with five carbons) and ethane (with two carbons). "Our aim is to convert lower molecular weight alkanes to valuable diesel-range alkanes," said Manoja Samantaray from the KAUST Catalysis Center. At the heart of the catalyst are compounds of two metals, titanium and tungsten, which are anchored to a silica surface via oxygen atoms. The strategy used was catalysis by design. Previous studies showed that monometallic catalysts were engaged in two functions: alkane to olefin and then olefin metathesis. Titanium was chosen because of its ability to activate the C-H bond of paraffins to transform them to olefins, and tungsten was chosen for its high activity for olefin metathesis. To create the catalyst, the team heated silica to remove as much water as possible and then added hexamethyl tungsten and tetraneopentyl titanium, forming a light-yellow powder. The researchers studied the catalyst using nuclear magnetic resonance (NMR) spectroscopy to show that the tungsten and titanium atoms lie extremely close together on the silica surfaces, perhaps as close as ≈0.5 nanometres. The researchers, led by the Director of the center Jean-Marie Basset, then tested the catalyst by heating it to 150°C with propane for three days. After optimizing the reaction conditions— for example, by allowing the propane to flow continuously over the catalyst—they found that the main products of the reaction were ethane and butane and that each pair of tungsten and titanium atoms could catalyze an average of 10,000 cycles before losing their activity. This "turnover number" is the highest ever reported for a propane metathesis reaction. This success of catalysis by design, the researchers propose, is due to an expected cooperative effect between the two metals. First, a titanium atom removes hydrogen atoms from propane to form propene and then a neighboring tungsten atom breaks open propene at its carbon-carbon double bond, creating fragments that can recombine into other hydrocarbons. The researchers also found that catalyst powders containing only tungsten or titanium performed very poorly; even when these two powders were physically mixed together, their performance did not match the cooperative catalyst. The team hopes to design an even better catalyst with a higher turnover number, and a longer lifetime. "We believe that in the near future, industry can adopt our approach for producing diesel-range alkanes and more generally of catalysis by design," said Samantaray. Explore further: A new catalyst to transform propane into propene More information: Manoja K. Samantaray et al. Unearthing a Well-Defined Highly Active Bimetallic W/Ti Precatalyst Anchored on a Single Silica Surface for Metathesis of Propane, Journal of the American Chemical Society (2017). DOI: 10.1021/jacs.6b12970
Zhao J.,Catalysis Center |
Hadjichristidis N.,Catalysis Center
Polimery/Polymers | Year: 2014
In the recent surge of metal-free polymerization techniques, phosphazene bases have shown their remarkable potential as organic promoters/catalysts for the anionic polymerization of various types of monomers. By complexation with the counterion (e.g. proton or lithium cation), phosphazene base significantly improve the nucleophilicity of the initiator/chain-end resulting in rapid and usually controlled anionic/quasi-anionic polymerization. In this review, we will introduce the general mechanism, i.e. in situ activation (of initiating sites) and polymerization, and summarize the applications of such a mechanism on macromolecular engineering toward functionalized polymers, block copolymers and complex macromolecular architectures.
Wahab A.K.,SABIC |
Ould-Chikh S.,Catalysis Center |
Meyer K.,ETH Zurich |
Journal of Catalysis | Year: 2017
The effect of TiO2 phase composition on the photocatalytic hydrogen production of water/ethanol (95/5 volume ratio) has been studied in order to understand the structural effect (and associated electronic properties) on the reaction within the so called "synergistic effect" concept. Within the investigated series of 1wt.% Pt/TiO2 with initial particle dimension of ca. 15nm the highest hydrogen production rate per unit area was observed for catalysts composed of 80% anatase, 18% rutile and 2% brookite. The associated particle sizes for this catalyst were 44, 82 and 33nm for the three phases, respectively. XRD patterns analyzed by the Rietveld method as well as X-ray absorption near-edge spectra (XANES) of the Ti K-edge mapped the phase transformation from anatase/brookite to rutile where it appears that the brookite phase is initially transformed to anatase phase. XRD patterns and Raman shift were found to be more sensitive to subtle changes in phase composition when compared to UV-vis absorbance or XANES of the Ti K-edge. The photocatalytic reaction for the complete series was conducted in identical condition and with excess photon flux in order to extract accurate reaction rates. In addition to the observed multi-phase effects on the reaction rate, other parameters extracted from the Rietveld refinement of the X-ray diffraction patterns were found to be useful. In particular, at the narrow window where the reaction rate was found to be maximum, the c-dimension of the anatase phase had values in the range 9.510-9.515Å. These c-dimension values are between those observed for nanoparticles with less than 20nm in size and those for larger particles with a size above 50nm. Results from this work indicate that the synergism between anatase and rutile on the photocatalytic reaction for hydrogen production, often attributed to increase the charge carrier life time, may be linked to the lattice expansion of the anatase phase which in turn would affect its electronic/catalytic properties. © 2017 Elsevier Inc.
News Article | December 14, 2016
Thuwal, Kingdom of Saudi Arabia - Dec. 13, 2016: Jean-Marie Basset, a distinguished professor of chemical science and director of the Catalysis Center at King Abdullah University of Science and Technology (KAUST) has been named a Fellow of the US National Academy of Inventors (NAI). "Election to NAI Fellow status attests to the innovation and impact of Dr. Basset's discoveries," said KAUST President Jean-Lou Chameau. "This is a well-deserved honor for Dr. Basset, who continues to make outstanding contributions to chemistry in academia and industry." The NAI Fellow program is the highest professional recognition accorded solely to academic inventors who have demonstrated a prolific spirit of innovation in creating or facilitating outstanding inventions that have made a tangible impact on quality of life, economic development and the welfare of society. Basset, who has over 50 patents and has authored more than 500 scientific papers and reports, works to evidence the possible relationships between homogeneous and heterogeneous catalysis. For that purpose, he developed "Surface Organometallic Chemistry", a new field of chemistry that has resulted in the discovery of a number of new catalytic reactions. Basset holds various professional memberships to societies such as the European Academy of Sciences and Arts, Academia Europaea, French Academy of Technologies, and French Academy of Sciences. He is the recipient of several national and international awards: the Chevalier dans l'Ordre National du Mérite, the Max Planck Research Award, the Grand Prix de la Société Française de Chimie, the Distinguished Achievements Award of IMPI, and the Augustine Award of the ORCS, to name a few. Basset joins the ranks of two other KAUST faculty, 2015 NAI fellows Charlotte Hauser, professor of bioscience, and Jean Fréchet, distinguished professor of chemical science and vice president for research. With the election of the 2016 class there are now 757 NAI Fellows, representing 229 research universities and governmental and non-profit research institutes. The 2016 Fellows will be inducted on April 6, 2017, as part of the Sixth Annual Conference of the National Academy of Inventors in Boston, MA. King Abdullah University of Science and Technology (KAUST) is an international, graduate-level research university located on the Red Sea coast of Saudi Arabia. The University is dedicated to advancing science and technology through interdisciplinary research, education and innovation. Goal-oriented and curiosity-driven research is conducted by students, faculty, scientists and engineers to address the world's pressing scientific and technological challenges related to water, food, energy and the environment. KAUST seeks to contribute to the transformation of Saudi Arabia to a knowledge-based economy, promoting economic development and achieving the widest public benefit. http://www. The National Academy of Inventors is a 501(c)(3) non-profit member organization comprising U.S. and international universities, and governmental and non-profit research institutes, with over 3,000 individual inventor members and Fellows spanning more than 240 institutions, and growing rapidly. It was founded in 2010 to recognize and encourage inventors with patents issued from the U.S. Patent and Trademark Office, enhance the visibility of academic technology and innovation, encourage the disclosure of intellectual property, educate and mentor innovative students, and translate the inventions of its members to benefit society. http://www.
Li Y.,University of Tokyo |
Takata T.,University of Tokyo |
Cha D.,King Abdullah University of Science and Technology |
Takanabe K.,Catalysis Center |
And 3 more authors.
Advanced Materials | Year: 2013
A vertically aligned Ta3N5 nanorod photoelectrode is fabricated by through-mask anodization and nitridation for water splitting. The Ta3N5 nanorods, working as photoanodes of a photoelectrochemical cell, yield a high photocurrent density of 3.8 mA cm -2 at 1.23 V versus a reversible hydrogen electrode under AM 1.5G simulated sunlight and an incident photon-to-current conversion efficiency of 41.3% at 440 nm, one of the highest activities reported for photoanodes so far. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Zhao J.,Catalysis Center |
Pahovnik D.,Catalysis Center |
Gnanou Y.,King Abdullah University of Science and Technology |
Hadjichristidis N.,Catalysis Center
Macromolecules | Year: 2014
The effectiveness of carboxylic acid as initiator for the anionic ring-opening polymerization of ethylene oxide was investigated with a strong phosphazene base (t-BuP4) used as promoter. Kinetic study showed an induction period, i.e., transformation of carboxylic acid to hydroxyl ester, followed by slow chain growth together with simultaneous and fast end-group transesterification, which led to poly(ethylene oxide) (PEO) consisting of monoester (monohydroxyl), diester, and dihydroxyl species. An appropriate t-BuP4/acid ratio was proven to be essential to achieve better control over the polymerization and low dispersity of PEO. This work provides important information and enriches the toolbox for macromolecular and biomolecular engineering with protic initiating sites. © 2014 American Chemical Society.
Goumri-Said S.,KAUST |
Benali Kanoun M.,Catalysis Center |
Manchon A.,KAUST |
Journal of Applied Physics | Year: 2013
The spin-polarization at the interface between Fe(100) and a benzene is investigated theoretically using density functional theory for two positions of the organic molecule: planar and perpendicular with respect to the substrate. The electronic and magnetic properties as well as the spin-polarization close to the Fermi level strongly depend on the benzene position on the iron surface. An inversion of the spin-polarization is induced by p-d hybridization and charge transfer from the iron to the carbon sites in both configurations. © 2013 American Institute of Physics.
Fihri A.,Catalysis Center |
Sougrat R.,King Abdullah University of Science and Technology |
Rakhi R.B.,King Abdullah University of Science and Technology |
Rahal R.,Catalysis Center |
And 5 more authors.
ChemSusChem | Year: 2012
Nickel oxide and mixed-metal oxide structures were fabricated by using microwave irradiation in pure water. The nickel oxide self-assembled into unique rose-shaped nanostructures. These nickel oxide roses were studied by performing electron tomography with virtual cross-sections through the particles to understand their morphology from their interior to their surface. These materials exhibited promising performance as nanocatalysts for CO oxidation and in energy storage devices. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Goumri-Said S.,KAUST |
Kanoun M.B.,Catalysis Center
Journal of Solid State Chemistry | Year: 2013
By means of first-principles calculations, the structural, elastic, electronic, magnetic and optical properties of pentalanthanum hexamolybdenum henicosaoxide (La 5Mo 6O 21) were studied in detail. No experimental or theoretical investigations of its physical properties have previously been reported in the literature. Our results reveal that La 5Mo 6O 21 is metallic with high ionic character due to the oxygen composition. The bonding characterization was achieved by analysis of valence charge density and the electronic localized functions. Flexibility and ease of deformation of the tetrahedral units appears to be important for the ion conduction mechanisms. The magnetic moment was evaluated to be 8.03 μ B, principally induced by Mo d-orbitals and La f-orbitals and the polarization of the oxygen by molybdenum. The optical spectra were analyzed by means of the electronic structure. The future advances will depend on achieving a fundamental understanding of the structural, defect and mechanistic features of ion conducting materials. © 2012 Elsevier Inc. All rights reserved.
News Article | November 16, 2016
Making greater use of sunlight's abundant energy as an alternative and sustainable power source is a key priority for researchers worldwide. The drive towards more efficient and more extensive use of solar energy is also a prominent goal of the University to promote in-Kingdom research and development. The KAUST Catalysis Center works on ways to develop catalysts that can harness solar energy to power the chemistry that creates alternative fuels—for example, by splitting water into hydrogen and oxygen gases. "Saudi Arabia is privileged to possess both existing and future energy resources," said Kazuhiro Takanabe, KAUST associate professor of chemical science and a member of the University's Catalysis Center, referring to the Kingdom's oil reserves and abundant solar energy. "At our center, we are working on building the bridge from current energy production methods to those of the future." Takanabe and his Ph.D. student Muhammad Qureshi focused their review on the use of powder photocatalysts to accelerate light-driven reactions in liquids. This process of heterogeneous photocatalysis is one of the most significant procedures used to harness light for fuel production and environmental remediation. "We hope to draw attention to the problem of different measuring and reporting systems and suggest procedures that will allow easier comparison among the results from different laboratories," said Takanabe. This is a vital issue, as the most effective and economically viable solar energy solutions can only be identified if the efficiency of different methods can be accurately compared. Takanabe also pointed out that some research papers contain inaccuracies and are inconsistent, partly because of the different systems of measurement and reporting. The KAUST team proposed a unified system to report the key variables linked to the efficiency of different photocatalytic materials, and they give an example based on their own work. Quantifying the key variables is focused on three measurements, which are the photon flux through each photo-reactor, the photocatalytic rate at which maximized incident photons are absorbed and the accurate measurement of reactant consumption and product generation. The researchers hope that their review and proposals will assist research teams around the world in their quest to develop an increasingly solar-powered future. Explore further: Graphene quantum dots can improve the efficiency of silicon solar cells More information: Muhammad Qureshi et al. Insights on Measuring and Reporting Heterogeneous Photocatalysis: Efficiency Definitions and Setup Examples, Chemistry of Materials (2016). DOI: 10.1021/acs.chemmater.6b02907