EXC - UniCat

15 Items

Recent Submissions
Design of PtZn nanoalloy catalysts for propane dehydrogenation through interface tailoring via atomic layer deposition

Ingale, Piyush ; Knemeyer, Kristian ; Preikschas, Phil ; Ye, Mengyang ; Geske, Michael ; Naumann d'Alnoncourt, Raoul ; Thomas, Arne ; Rosowski, Frank (2020-11-18)

Supported Pt nanoparticles are widely used for the catalytic dehydrogenation of propane to propene. Monometallic Pt catalysts are subject to fast deactivation. A successful strategy for stabilization is alloying Pt with a second metal. In this study, we present a novel approach for the precise formation of bimetallic nanoparticles via tailoring of the interface between metal nanoparticles and t...

Toolbox for atomic layer deposition process development on high surface area powders

Knemeyer, Kristian ; Baumgarten, Robert ; Ingale, Piyush ; Naumann d’Alnoncourt, Raoul ; Driess, Matthias ; Rosowski, Frank (2021-02-18)

Atomic layer deposition (ALD) is an industrially applied technique for thin film deposition. The vast majority of processes target flat substrates rather than powders. For ALD on powders, new processes are needed, as different reaction conditions are required. Here, two setups are described in detail, which enhance the ALD process development for powders. The first setup described is capable of...

Design of an active and stable catalyst for dry reforming of methane via molecular layer deposition

Ingale, Piyush ; Guan, Chengyue ; Kraehnert, Ralph ; Raoul, Naumann d’Alnoncourt ; Thomas, Arne ; Rosowski, Frank (2020-04-30)

The dry reforming of methane (DRM) has been proposed as an efficient way to convert two greenhouse gases, namely CO2 and CH4 to syngas. However, most catalysts reported in the literature suffer from strong deactivation during the reforming reaction. The deactivation is caused by strong sintering of catalytically active nanoparticles and the formation of filamentous carbon. Herein a new synthesi...

Mechanistic studies of atomic layer deposition on oxidation catalysts – AlOx and POx deposition

Knemeyer, Kristian ; Hermida, Mar Piernavieja ; Ingale, Piyush ; Schmidt, Johannes ; Kröhnert, Jutta ; Naumann d’Alnoncourt, Raoul ; Driess, Matthias ; Rosowski, Frank (2020-07-15)

Atomic layer deposition is a rising technique for catalyst synthesis and modification. Typically, the focus of ALD in catalysis is on supported metal nanoparticles. Here, the authors give mechanistic insights into the ALD of oxides on redox active catalysts by a combination of in situ analytics, such as XPS, DRIFTS and gravimetric measurements. Phosphorus oxide and aluminum oxide were deposited...

Atomic Layer Deposition of ZnO on Mesoporous Silica: Insights into Growth Behavior of ZnO via In-Situ Thermogravimetric Analysis

Ingale, Piyush ; Knemeyer, Kristian ; Piernavieja Hermida, Mar ; Naumann d’Alnoncourt, Raoul ; Thomas, Arne ; Rosowski, Frank (2020-05-20)

ZnO is a remarkable material with many applications in electronics and catalysis. Atomic layer deposition (ALD) of ZnO on flat substrates is an industrially applied and well-known process. Various studies describe the growth of ZnO layers on flat substrates. However, the growth characteristics and reaction mechanisms of atomic layer deposition of ZnO on mesoporous powders have not been well stu...

Towards Experimental Handbooks in Catalysis

Trunschke, Annette  ; Bellini, Giulia  ; Boniface, Maxime  ; Carey, Spencer J.  ; Dong, Jinhu  ; Erdem, Ezgi  ; Foppa, Lucas  ; Frandsen, Wiebke  ; Geske, Michael  ; Ghiringhelli, Luca M.  ; Girgsdies, Frank  ; Hanna, Rania  ; Hashagen, Maike  ; Hävecker, Michael  ; Huff, Gregory  ; Knop‑Gericke, Axel  ; Koch, Gregor  ; Kraus, Peter  ; Kröhnert, Jutta  ; Kube, Pierre  ; Lohr, Stephen  ; Lunkenbein, Thomas  ; Masliuk, Liudmyla  ; Naumann d’Alnoncourt, Raoul ; Omojola, Toyin  ; Pratsch, Christoph  ; Richter, Sven  ; Rohner, Christian  ; Rosowski, Frank  ; Rüther, Frederik  ; Scheffler, Matthias  ; Schlögl, Robert  ; Tarasov, Andrey  ; Teschner, Detre  ; Timpe, Olaf  ; Trunschke, Philipp  ; Wang, Yuanqing  ; Wrabetz, Sabine  (2020-10-06)

The “Seven Pillars” of oxidation catalysis proposed by Robert K. Grasselli represent an early example of phenomenological descriptors in the field of heterogeneous catalysis. Major advances in the theoretical description of catalytic reactions have been achieved in recent years and new catalysts are predicted today by using computational methods. To tackle the immense complexity of high-perform...

Enhancing of catalytic properties of vanadia via surface doping with phosphorus using atomic layer deposition

Strempel, Verena E. ; Löffler, Daniel ; Kröhnert, Jutta ; Skorupska, Katarzyna ; Johnson, Benjamin ; Naumann d’Alnoncourt, Raoul ; Drieß, Matthias ; Rosowski, Frank (2015-12-11)

Atomic layer deposition is mainly used to deposit thin films on flat substrates. Here, the authors deposit a submonolayer of phosphorus on V2O5 in the form of catalyst powder. The goal is to prepare a model catalyst related to the vanadyl pyrophosphate catalyst (VO)2P2O7 industrially used for the oxidation of n-butane to maleic anhydride. The oxidation state of vanadium in vanadyl pyrophosphate...

Atomic layer deposition on porous powders with in situ gravimetric monitoring in a modular fixed bed reactor setup

Strempel, Verena E. ; Naumann d’Alnoncourt, Raoul ; Drieß, Matthias ; Rosowski, Frank (2017-07-19)

A modular setup for Atomic Layer Deposition (ALD) on high-surface powder substrates in fixed bed reactors with a gravimetric in situ monitoring was developed. The design and operation are described in detail. An integrated magnetically suspended balance records mass changes during ALD. The highly versatile setup consists of three modular main units: a dosing unit, a reactor unit, and a downstre...

Investigating the trimethylaluminium/water ALD process on mesoporous silica by in situ gravimetric monitoring

Strempel, Verena E. ; Knemeyer, Kristian ; Naumann d’Alnoncourt, Raoul ; Rosowski, Frank (2018-05-24)

A low amount of AlOx was successfully deposited on an unordered, mesoporous SiO2 powder using 1–3 ALD (Atomic Layer Deposition) cycles of trimethylaluminium and water. The process was realized in a self-built ALD setup featuring a microbalanceand a fixed particle bed. The reactor temperature was varied between 75, 120, and 200 °C. The self-limiting nature of the deposition was verified by in si...

Controlled ligand distortion and its consequences for structure, symmetry, conformation and spin-state preferences of iron(II) complexes

Kroll, Nicole ; Theilacker, Kolja ; Schoknecht, Marc ; Baabe, Dirk ; Wiedemann, Dennis ; Kaupp, Martin ; Grohmann, Andreas ; Hörner, Gerald (2015)

The ligand-field strength in metal complexes of polydentate ligands depends critically on how the ligand backbone places the donor atoms in three-dimensional space. Distortions from regular coordination geometries are often observed. In this work, we study the isolated effect of ligand-sphere distortion by means of two structurally related pentadentate ligands of identical donor set, in the sol...

Palladium-catalysed hydroxylation and alkoxylation

Enthaler, Stephan ; Company, Anna (2011)

The formation of oxygen–carbon bonds is one of the fundamental transformations in organic synthesis. In this regard the application of palladium-based catalysts has been extensively studied during recent years. Nowadays it is an established methodology and the success has been proven in manifold synthetic procedures. This tutorial review summarizes the advances on palladium-catalysed C–O bond f...

A straightforward zinc-catalysed reduction of sulfoxides to sulfides

Enthaler, Stephan (2011)

In the present study, the zinc-catalysed reduction of a variety of sulfoxides with silanes as reductant to the corresponding sulfide has been examined in detail. With the straightforward and commercially available zinc(II) triflate as pre-catalyst, excellent yields and chemoselectivities were feasible. After studying the reaction conditions and the scope and limitations several attempts were un...

Iron-based pre-catalyst supported on polyformamidine for C-C bond formation

Enthaler, Stephan ; Krackl, Sebastian ; Epping, Jan Dirk ; Eckhardt, Björn ; Weidner, Steffen M. ; Fischer, Anna (2012)

In the present study the incorporation of iron into an organic polymer, composed of formamidine subunits [R–N[double bond, length as m-dash]C(H)–NH–R], has been examined. The catalytic ability of the recyclable material was investigated in the iron-catalyzed formation of C–C bonds. After optimization of the reaction conditions, excellent yields and chemoselectivities were feasible.

Dual functionality of formamidine polymers, as ligands and as bases, in ruthenium-catalysed hydrogen evolution from formic acid

Enthaler, Stephan ; Junge, Henrik ; Fischer, Anna ; Kammer, Anja ; Krackl, Sebastian ; Epping, Jan Dirk (2013)

In the present study, the ruthenium-catalysed decomposition of formic acid to yield hydrogen has been examined. A ruthenium complex modified polyformamidine network was used as a solid catalyst. As a dual support the polyformamidine acts both as a ligand and as a base for the activation of formic acid.

Enhanced catalytic performance of MnxOy-Na2WO4/SiO2 for the oxidative coupling of methane using an ordered mesoporous silica support

Yildiz, M. ; Aksu, Y. ; Simon, U. ; Kailasam, K. ; Görke, O. ; Rosowski, F. ; Schomäcker, R. ; Thomas, A. ; Arndt, S. (2014)

The oxidative coupling of methane is a highly promising reaction for its direct conversion. Silica supported MnxOy–Na2WO4 is a suitable catalyst for this reaction. In this study, a variety of different SiO2 materials have been tested as supports. Surprisingly, the application of ordered mesoporous silicas, here exemplarily shown for SBA-15 as support materials, greatly enhances the catalytic pe...