Selective Oxidation of CH Bonds Raw Materials Change

Selective Oxidation of C-H Bonds Raw Materials Change in Chemical Industry and Efficient Energy Storage Model studies of C-H Activation Introduction Objectives and strategy Highlights • Deeper understanding of the structural dynamics of the active sites and the entire catalyst material • Theoretical and experimental investigation of the interactions of catalyst and reaction dynamics • Identification of key factors controlling the performance of catalysts • Design of catalysts with adjustable “smart” surface properties • Immediate transfer of promising catalysts and process concepts to application • Oxidative coupling of CH 4 on Li-doped and non-doped Mg. O • The calculated energy barriers for CH 4 activation by hydrogen abstraction at oxygen radical sites of Li-doped Mg. O are unrealistically low. • Lundsford mechanism needs to be revised • Temperature programmed reaction experiments: the same active sites are responsible for activation of methane on both Li-doped Mg. O and pure Mg. O catalysts. Highlights • The multi-scale approach of UNICAT to the oxidative coupling of methane made substantial achievements for the fundamental understanding of simplest OCM catalyst and the development of promising catalyst and process for industrial application. • Revision of the long-time established “Lunsford”-mechanism • Detailed understanding of the contribution of gas phase reactions • Proposal of new activation mechanism at non-reducible oxide surfaces • Revealing of fluctuations in composition and shape of catalyst surface by in-situ structural studies at model systems • Substantial improvement of mixed hetero-metallic Na. Mn. Si oxide catalyst by advanced preparation methods • Identification of different oxygen species involved in selective and in selective reaction pathways • Development of optimized reactor concepts on the basis of comprehensive kinetic models • Conception and validation of new OCM process on mini-plant level • Measurements for differently prepared pure Mg. O catalysts suggest that the catalytic activity originates from morphological defects. • The activity proved to be very different in the initial phase of the OCM reaction and in the steady state. • Substantial morphological changes and restructuring of the terminations as transmission electron microscopy revealed. Modes of dynamics in catalysis with novel aspects of chemical and structural dynamics Kwapien, Paier, Sauer, Geske, Zavyalova, Horn, Schwach, Trunschke, Schlögl, Angew. Chem. Int. Ed. , 2014, 53, 8774 Kinetic Investigations of Gas Phase Reactions Highlights • Charge transfer from Mo donor ions stimulates the formation of superoxo-species on the surface of a wide-gap Ca. O film. • Formation of pre-dissciated O 2 - species • Final dissociation via electron tunneling from STM tip A profile reactor with on-line MS analysis allows spatial resolution of reactant and product concentrations in catalyst beds as well as free gas phase • Coupling of methane to C 2 -products without catalysts • Lag period for establishment of radical pool • Strong pressure dependence of selectivity Objectives and strategys • Characterize different oxygen species on the catalyst surface by joint experimental – computational work • Use computational methods to explore the role of different oxygen species in the complex reaction mechanism Objectives Extention of profile reactor studies to other hydrocarbon oxidation reactions and combination with in-situ studies of catalyst surface • Microkinetic model for homogeneous gas phase reactions • Two dimensional reactor modeling with CFD tool for model validation R. Horn, O. Korup, M. Geske, U. Zavyalova, I. Oprea, R. Schlögl , Review of Scientific Instruments 2010, 81, 64102 Cui, Shao, Baldowski, Sauer, Nilius Freund, Angew. Chem. Int. Ed. , 2013, 52, 11385 Synthesis of Mn/Na 2 WO 4/SBA-15 Reactor concepts Objectives precatalyst silica support catalyst Highlights • Investigation of structural dynamics • Correlation of performance and dynamics • Identification of tuning parameters for dynamic properties Impregnation Calcination Na 2 WO 4 · 2 H 2 O Mn(ac)2 · 4 H 2 O 750°C • Comparison of phase pure and complex phase catalysts • Detailed mechanistic studies and kinetic modeling of OCM • Simulation studies for OCM in Fixed Bed, Fluidized Bed and Membrane Reactor • Derivation of optimized feed strategies • Validation of catalysts performance with up to 200 g catalyst • C 2 -Yield of 25, 5 % at 80 % selectivity • Concepts for integrated OCM/DRM reactor X Mn-Na 2 WO 4/SBA-15 Scheme of fluidized bed reactor and OCM performance data Mn-Na 2 WO 4/SBA-15 S. Jaso et al. , J. Nat. Gas Chem. , 2012, 21 534 -543 nanostructured (SBA-15) Mn-Na 2 WO 4/ commercial silica Up-scaling of catalyst synthesis Highlights Objectives • Design of reactors and operation strategies by simulation studies with comprehensive kinetic models • Highly homogeneous dispersion of active components over SBA-15 • Increased activity due to higher dispersion of Mn/Na 2 WO 4 • Increased selectivity due to reduced number of non-selective sites at uncovered support material • Improved stability Testing on lab scale C 2 -Yield= 12 % Validation in Miniplant C 2 -Yield= 25, 5 % M. Yildiz, Y. Aksu, U. Simon, K. Kailasam, O. Goerke, F. Rosowski, R. Schomäcker, A. Thomas, S. Arndt Chem. Commun. 2014, 50, 14440 Process Design and Validation in Mini-Plants • Design and optimization of membrane fluidized bed reactor Scheme of membrane reactor and performance data H. R. Godini, et al. Energy & Fuels 2013, 1312 • Utilization of instationary operation conditions Harnessing the Methodological Toolbox Highlights Objectives Physical methods for structure analytical studies New Reactor concepts • Successful scale-up of OCM to a mini-plant • Yield of 25, 5 % at 80 % selectivity in mini-plant • 50 % energy saving in down-stream processing by hybrid separation process • Concepts for process integration of OCM and DRM • Investigation of different equipment alternatives • Chemical Microscope EMIL • Dynamic behavior of reactors under recycle conditions • Vibrational spectrodscopy for identifying adsorbates • Chemical Looping for partial oxidation reactions • Integration of reactors with instationary operation mode • EPR spectroscopy for high spin metal centers • Solid-state NMR with dynamic nuclear polarization (DNP) • X-Ray adsorption spectroccopy for direct tracking of structural changes Conventional design of OCM process Steam Generator Refrigerant Compressor Reactor CO 2 Absorption Cryogenic Distillation CO 2 CH 4, CO, H 2 Reactor 66 h • New mechanism proposed: Methane binds heterolytically on Mg 2+O 2 - sites at steps and corners, and methyl radicals are released into the gas phase when O 2 is present on the surface. • The role of the catalyst surface is to bind CH 4 and O 2 which exchange redox equivalent directly among themselves, but not with the catalyst. Activation of O 2 at model catalysts commercial 0 h Compressor Air Blower Steam Generator Adsorptive Separation CO 2 Absorption CH 4, CO, H 2 CO 2 • Challenges for fluid dynamics and process control C 2 Scheme of alternative OCM process without compressor D 2/E 2 • Feed strategies for separation of competitive reactions Flow diagram of new OCM process H. R. Godini, et. al. Technical Transactions 2012, 5, 63– 74 Dynamical terminating graphene layer at bulk copper metal (green lines in right image) followed by the home-developed in-situ ambient pressure SEM. Scheme of Chemical Looping operation of fixed bed reactors