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Viewing upcoming talks containing the keyword: 3
Catalyst design, route development and feed characterization for lignocellulosic biomass valorization: different ways to renewable aromatics
Speaker: Peiter Bruijnincx (Utrecht)
Catalyst design, route development and feed characterization for lignocellulosic biomass valorization : different ways to renewable aromatics
An overview of some recent efforts from our lab will be presented, focusing on the catalytic valorization of the primary components of lignocellulosic biomass and the further conversion of renewable platform molecules to either new or drop -in chemicals . As showcase examples, the production or renewable aromatics from three different feeds will be discussed, including the catalytic depolymerization of lignin, the aromatization of biobased carbohydrate -derived furanics via a modified Diels -Alder aromatization route and the valorization of volatile fatty acids from waste water fermentation by sequential ketonization/arom atization. Examples of homogeneously and heterogeneously catalyzed routes will be included. As the complex structural nature of the biomass feed, lignin in particular, requires the development of new catalytic conversion strategies to go hand in hand with advan ced structural characterization, recent new insights into the structure of (technical) lignins and humins will also be presented .
 R. Rinaldi et al. Angew. Chem. Int. Ed. 2016, 55, 8164; R. Jastrzebski et al. ChemSusChem 2016, 9, 2074;  S. Thiyagarajan et al. ChemSusChem 2015, 8, 3052; Angew. Chem. Int. Ed. 2016, 55 , 1368.; H.C. Genuino et al. ChemSusChem 2017 , 10, 277 ; [3 ] Constant et al. Green Chem. 2016, 18, 2651; Van Zandvoort et al. Green Chem. 2015, 17, 4383 ; Lancefield et al . submitted for publication . Download PDF
On: February 28, 2018 From: 15h30 To: 16h30View talk
Homogeneous hydrogenation. An indispensable tool in the conversion of renewables and platform chemicals.
Speaker: Johannes de Vries (LIKAT, Rostock)
Homogeneous hydrogenation . An indispensable tool in the conversion of renewables and platform chemicals. Johannes G. de Vries Leibniz Institut für Katalyse, Albert -Einstein -Strasse 29a, 18059 Rostock, Germany johannes.devries@cataly sis.de Homogeneous hydrogenation has become a mature science. 1 Initially, the focus was very much on the development of asymmetric hydrogenation catalysts. 2 These days many chiral ligands are available, some of which quite affordable. The focus has now shifted towards selective hydrogenation of one functional group in the presence of another one. As part of our investigation of the conversion of bioethanol in to crotyl alcohol, a new platform chemical, we developed an interest in the selective reduction of -unsaturated aldehydes to the allylic alcohols. The problem here is that most efficient ruthenium catalysts are activated by base, which can lead to serio us side - reactions of the substrate aldehyde. We have solved this problem with the use of Ru -MACHO -BH as base - free transfer hydrogenation catalyst; this catalyst functions both with i-PrOH as well as with EtOH as reductant. 3 Another low -cost solution surpri singly does not come from a low -cost metal like iron, but rather from a catalyst made from ruthenium and a cheap NNS pincer ligand. 4 This catalyst is highly active and selective for the hydrogenation of -unsaturated aldehydes and ketones. In addition, w e have found that this is the first catalyst that is capable of selectively reducing -unsaturated esters to the allylic aldehydes. 5 In the second part of the lecture we will discuss our investigations on the development of cheap metal catalysts for th e isomerization of allylic alcohols to aldehydes or ketones. We got interested in this reacted as we wanted to convert crotyl alcohol into butyraldehdye. Whereas many ruthenium -catalysts exist that will catalyse this reaction very little is known about the use of cheap metals like iron, cobalt or manganese. We have now found that an iron catalyst can catalyse this transformation at room temperature. 6
1 Handbook of Homogeneous Hydrogenation, J. G. de Vries and C. J. Els evier, eds., Wiley -VCH , 2007 , Vol 1-3. 2 D. J. Ager, A. H. M. de Vries J. G. de Vries, Chem. Soc. Rev ., 2012 , 41, 3340 –3380. 3 R. Farrar -Tobar, Z. Wei, H. Jiao, S. Hinze, J . G. de Vries , Chem. Eur. J. 2018 , DOI : 10.1002/chem.201705423 . 4 P. Puylaert, R. van Heck, Y. Fan, A. Spannenberg, W. Baumann, M. Beller, J. Medlock, W. Bonrath, L. Lefort, S. Hinze, J. G. de Vries, Chem. Eur. J. 2017 , 23 , 8473 – 8481. 5 B. Stadler, P. Puylaert, J. Diekamp, R. van Heck, Y . Fan, A . Spannenberg, S . Hinze , J. G. de Vries , Adv. Synth. Catal. 2018 , http://dx.doi.org/10.1002/adsc.201701607 . 6 T. Xia, Z. Wei, B. Spiegelberg, H. Jiao, S. Hinze, J. G. de Vries, Chem. Eur. J. 2018 , DOI: 10.1002/chem.201705454 Download PDF
On: March 1, 2018 From: 14h00 To: 15h00View talk
Speaker: Edina Rosta (King\\\\\\\'s College London)
The formation and cleavage of phosphate bonds is essential in most biological processes including nucleic acid processing. Many enzymes that catalyze phosphate hydrolysis require bound divalent metal ions. Most commonly, Mg 2+ ions are required for catalysis, while similar Ca 2+ ion abolishes the catalytic activity. To elucidate the poorly understood mechanism of these ubiquitous metal ion catalyzed reactions, we carry out hybrid quantum -classical QM/MM free energy simulations. In our calculations, we focus on specific systems, including Ribonuclease H (RNase H)  and dUTPase . To gain a more general picture of the key requirements for Mg 2+ coordination, we also performed a PDB -wide analysis enumerating possible NTP hydrolys is enzyme crystal structures. Our results highlight key structural requirements for the Mg 2+ ion to serve as a “Mg -pinch” motif in phosphate catalysis over a wide range of enzymes. Reference s  E. Rosta, W. Yang and G. Hummer, J. Am. Chem. Soc. , Vol . 136, 3137, 2014  (a) Lopata, A.; Jambrina, P. G.; Sharma, P. K.; Brooks, B. R.; Toth, J.; Vertessy, B. G.; Rosta, E., ACS Catalysis 2015, 5 (6), 3225 -3237; (b) Nagy, G. N.; Suardíaz, R.; Lopata, A.; Ozohanics, O.; Vékey, K.; Brooks, B. R.; Leveles, I. ; Tóth, J.; Vértessy, B. G.; Rosta, E., J. Am. Chem. Soc. 2016, 138 (45), 15035 -15045. Download PDF
On: March 7, 2018 From: 15h30 To: 16h30View talk
Speaker: Sylviane Sabo-Etienne (Toulouse)
Dihydrogen and Polyfunctional L igands: Coordination Chemistry and Catalysis
More than 30 years ago, the proof by neutron diffraction that dihydrogen could be coordinated to a metal center without H -H bond breaking was published by Gregory Kubas and collaborators . The sigma dihydrogen complexes were born. Nearly at the same time, the concept of agostic interactions was established by Maurice Brookhart and Malcolm Green. Since then, many new complexes displaying agostic interactions or sigma coordination modes have been prepared, and applications in energy and catalysis have emerge d. If we want to control activity and selectivity issues, it is necessary to gain knowledge on the properties of this unique class of complexes which involves one (or in some cases two) three -centers, two -electron bonds. In this context, t his lecture will provide a few answers to the following points . How far can we define the hydrogen interaction with the metal center? Nowadays, we have access to a large variety of characterization techniques. Some of them might require sophisticated levels and be cost or/ and time expensive. Can we bypass them? How can we combine catalytic in situ monitoring , stoichiometric experiments , and various techniques to decipher the mechanism of a complex catalytic system? Download PDF
On: March 9, 2018 From: 12h00 To: 13h00View talk
Physics and Astronomy Colloquia
Speaker: Prof Paul Meredith (University of Swansea)
The light harvesting performance and tunability of organohalide perovskite semiconductors demonstrated in photovoltaic applications, leads to the obvious question as to whether they can be deployed as the junction in photodetectors. Indeed, these materials should in principle be able to rival other solution processed semiconductors such as the organics and inorganic quantum dots [1-3]. In my talk, I will describe recent progress to create a family of organohalide perovskite photodetectors based upon a simple thin film diode architecture. Applications include high detectivity broad-band photodiodes for the UV-Visible , single crystal NIR detectors , and narrow-band red, green, blue (RGB) systems  which deliver truly colour discriminative performance without the need for input optical filtering. The latter represent a completely new photodiode platform which could ultimately deliver the type of illuminant-independent imaging needed for machine and artificial vision.
 Solution-processed semiconductors for next-generation photodetectors”, F.P. García de Arquer, A. Armin, P. Meredith & E.H. Sargent, Nature Reviews Materials, 2, 16100 (2017).
 Thick junction broadband organic photodiodes, A. Armin, M. Hambsch, I.K. Kim, P.L. Burn, P. Meredith & E.B. Namdas, Laser and Photonics Reviews, 8(6), 924-932 (2014).
 Narrowband light detection via internal quantum efficiency manipulation of organic photodiodes, A. Armin, R. D. Jansen-van Vuuren, N. Kopidakis P. L. Burn & P. Meredith, Nature Communications, 6, 6343 (2015).
 Low noise, IR-blind organohalide perovskite photodiodes for visible light detection and imaging, Q. Lin, A. Armin, D.M. Lyons, P.L. Burn & P. Meredith, Advanced Materials, 27(12), 2060-2064 (2015);
 Near infrared photodetectors based on sub-gap absorption in organohalide perovskite single crystals, Q. Lin, A. Armin, P.L. Burn & P. Meredith, Laser and Photonics Reviews, 10(6), 1047-1053 (2016);
 Filterless, narrowband RGB photodetectors, Q. Lin, A. Armin, P.L. Burn & P. Meredith, Nature Photonics, 9, 687-694 (2015).
On: March 9, 2018 From: 10h00 To: 11h00View talk
Speaker: Michael D Ward (Warwick)
Self -assembled coordination cages (hollow metal/ligand capsules) have the ability to encapsulate small molecule guests in the central cavity. In this talk is presented a coordination cage with a very well developed host guest chemistry, for which the factors responsible for guest binding have been dissected in detail to the extent that guest binding can be quantitatively predicted. The combination of b inding of hydrophobic guests in the cage cavity in water, and accumulation of anions around the positively -charged cage surface by ion -pairing, has led to his catalytic rate enhancements for reactions of cavity -bound guests with surface -bound anions. As g uest binding and ion -pairing are based on orthogonal interactions, this affords a system capable in principle of quite general bimolecular catalysis of reactions of electrophiles with anions. Download PDF
On: March 14, 2018 From: 15h30 To: 16h30View talk