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Forschungsarbeit

Investigation of hydrocarbon transport on surface modified zeolites

by Stephan J. Reitmeier (09.07.2009)

Solids with nanopores such as molecular sieves are at the key to hydrocarbon sorption, separation and heterogeneous catalysis in modern industrial processes implementation. Moreover, due to their unique properties such as high surface area, non-toxicity and regular pore structure, zeolites nowadays cover a broad field of applications ranging from petrochemical industry to agriculture and environmental protection. However, a fundamental understanding of hydrocarbon transport in zeolites is crucial to advance material development beyond optimization and heuristic findings.

Overview to the formation of zeolite structures and the broad field of their applications.[Bildunterschrift / Subline]: Fig. 1. Overview to the formation of zeolite structures and the broad field of their applications.

Within the research project entitled Investigation of hydrocarbon transport phenomena on surface modified H-ZSM5 zeolites”, the complex network of sorption and transport steps for aromatic hydrocarbon molecules (benzene, toluene, o- and p-xylene) in ZSM-5 has been studied on a molecular level using fast time-resolved infrared spectroscopy and the frequency response method. Sorption into a physisorbed surface state with high two-dimensional mobility was found to precede sorption to the terminal sites, pore entering and intracrystalline diffusion processes.

Scheme illustrating the infrared spectroscopic approach to determine transport properties of aromatic hydrocarbons in H-ZSM5 zeolites with p-xylene adsorbed inside the H-ZSM5 pores.[Bildunterschrift / Subline]: Figure 2: Scheme illustrating the infrared spectroscopic approach to determine transport properties of aromatic hydrocarbons in H-ZSM5 zeolites with p-xylene adsorbed inside the H-ZSM5 pores (left). A typical series of time-resolved infrared spectra is given (middle) together with the concentration profile determined at the terminal active sites (right).

In a next step, three-dimensional structuring of the ZSM-5 surface with a mesoporous silica overlayer using chemical liquid deposition with tetraethyl orthosilicate investigated, leading to an enhancement of the sorption rates of small molecules by funneling them towards the nanopores of the zeolite. Larger molecules such as p-xylene are slowed down significantly, as the molecules are captured with respect to their radius of gyration by the overlayer porosity.

Scheme of an H-ZSM5 crystal with (right) and without silica surface overlayer indicating the enhanced separation of aromatic reactant molecules given with respect to their maximum length dimension.[Bildunterschrift / Subline]: Figure 3: Scheme of an H-ZSM5 crystal with (right) and without silica surface overlayer indicating the enhanced separation of aromatic reactant molecules given with respect to their maximum length dimension.

The hierarchic materials obtained, combining different pore sizes can open promising new ways in materials research for the a-priori design of sorbent materials for highly selective separation of aromatic and aliphatic hydrocarbon molecules.


Stephan J. Reitmeier
* 1980

Education
  • 2000 – 2005
  • TU München, Studies in Chemistry (Dipl.-Chem.), Diploma thesis „Reactivity and thermochemistry of transient species in water clusters“ (Prof. M. K. Beyer)
  • 2005 – 2006
  • JWG-University Frankfurt and TU München, Research associate „Investigation of structure-dynamic-function relations in DNA-based nanomagnets using EPR-spectroscopy“(Prof. O. Schiemann)
  • 2007 – 2008
  • South German Catalysis Institute Ulm, “Catalysis – Fundamental Aspects and Common Principles”
  • 2008 – 2009
  • Associate Member of the International Graduate Program NanoCat at the TU Munich
  • since 2006
  • TU Munich, PhD in Chemistry, Chair of Technical Chemistry, “Investigation of hydrocarbon transport phenomena on surface modified H-ZSM5 zeolites” (Prof. J. A. Lercher)

Scholarships
  • 2000 – 2002
  • Scholarship, „Jubiläumsstipendium“, VCI e.V., Frankfurt
  • 2000 - 2005
  • Scholarship, „BayBFG-Stipendium“, München
  • 2000 - 2005
  • Scholarship, Studienstiftung des Deutschen Volkes, Bonn / Berlin
  • 2006 - 2009
  • PhD-Scholarship, Studienstiftung des Deutschen Volkes e.V., Bonn / Berlin
  • 2007
  • Konferenz- und Reisekosten-Stipendium der Gesellschaft Deutscher Chemiker GDCh e.V., Frankfurt, Deutschland
  • 2008
  • Karl-Ziegler-Scholarship, Karl-Ziegler-Stiftung e.V. Frankfurt

Publications
  • Stephan J. Reitmeier, O. Petru Balaj, Vladimir E. Bondybey and Martin K. Beyer “Reactions of hydrated electrons (H2O)n- with formic acid”, Int. J. Mass Spect. 2006, 249-250, 106-111
  • Chi-Kit Siu, Stephan J. Reitmeier, Iulia Balteanu, Vladimir E. Bondybey, and Martin K. Beyer “Substrate Poisoning in the Catalytic Conversion of CO and N2O to CO2 and N2 on Pt4- in the Gas Phase”, Eur. Phys. J. D, 2007, 43, 189-191
  • Stephan J. Reitmeier, Rino R. Mukti, Andreas Jentys and Johannes A. Lercher “Surface transport processes and sticking probability of aromatic molecules in HZSM-5”, J. Phys. Chem. C, 2008, 112, 2538-2544
  • Stephan J. Reitmeier et al. “Experi-mental and theoretical investigation of the sticking probability of benzene, toluene and o-/p-xylene on amorphous SiO2 and HZSM-5”, in Studies in Surface Science and Catalysis 2008, Vol. 174 A, p. 585 – 590
  • Stephan J. Reitmeier, Oliver C. Gobin, Andreas Jentys and Johannes A. Lercher “On the enhancement of sorption processes on HZSM-5 by post synthetic surface modification”, “Angew. Chem. Int. Ed., 2009, 48, 533 – 538
  • Stephan J Reitmeier et al. “A Novel Design of a Temperature Controlled FT-ICR Cell for Low-Temperature Black-Body Infrared Radiative Dissociation (BIRD) Studies of Hydrated Ions”, Int. J. Mass Spec., 2009, 279, 5-9
  • Oliver C. Gobin, Stephan J. Reitmeier, Andreas Jentys and Johannes A. Lercher “Diffusion pathways of benzene, toluene and p-xylene in MFI”, Microp. Mesop. Mat., 2009 (in press)
  • Stephan J. Reitmeier, Oliver C. Gobin, Andreas Jentys and Johannes A. Lercher “Influence of post-synthetic modification on transport processes of aromatic molecules in HZSM-5”, J. Phys. Chem. C (in press)
  • Stephan J. Reitmeier, Oliver C. Gobin, Andreas Jentys and Johannes A. Lercher “Hierarchically structured microporous materials separate aromatic molecules based on their radius of gyration”, Angew. Chem. Int. Ed., (submitted)