Hannsjörg Freund

Hannsjörg Freund
Friedrich-Alexander-University of Erlangen-Nürnberg | FAU · Department of Chemical and Bioengineering

Prof. Dr.-Ing.

About

131
Publications
13,985
Reads
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2,495
Citations
Citations since 2016
51 Research Items
1829 Citations
2016201720182019202020212022050100150200250300
2016201720182019202020212022050100150200250300
2016201720182019202020212022050100150200250300
2016201720182019202020212022050100150200250300
Introduction
Hannsjörg Freund currently works at the Department of Chemical and Bioengineering, Friedrich-Alexander-University of Erlangen-Nürnberg. His research aims at the development of energy and resource efficient chemical processes with a special focus on the model-based design of optimal catalytic reactors. Research Areas include: 1) Model-based design of optimal reactors and processes -> Identification of the optimal reaction concept and conditions and the best possible transfer into innovative apparatuses 2) Cellular structures as novel catalyst supports -> Detailed understanding of local transport processes and, based on this, the design and manufacturing of innovative catalyst supports 3) Reaction kinetic modeling -> Identification of reaction kinetics and parameters based on experiments
Additional affiliations
January 2012 - present
Friedrich-Alexander-University of Erlangen-Nürnberg
Position
  • Professor
September 2005 - December 2011
Max Planck Institute for Dynamics of Complex Technical Systems
Position
  • Senior Researcher
September 2005 - December 2011
Otto-von-Guericke-Universität Magdeburg
Position
  • Senior Researcher

Publications

Publications (131)
Article
Periodic open cellular structures (POCS) show great potential for process intensification in catalytic reactors due to their favorable properties regarding heat transfer, pressure drop and liquid distribution. In multiphase applications, POCS can be employed as multifunctional catalyst carrier with integrated liquid distribution function for enhanc...
Article
The detailed understanding of local mass transport characteristics in porous catalyst supports is essential for the evaluation of their performance in reaction engineering applications. This applies particularly for the development and assessment of novel concepts such as additively manufactured periodic open cellular structures (POCS). A major dra...
Article
The kinetics of the acid catalyzed reactions of acetaldehyde ammonia trimer (AAT) and paraldehyde (para) to 2-methyl-5-ethyl pyridine (MEP) in the presence of an acid catalyst were investigated systematically. A...
Article
The dynamic and load flexible operation of fixed bed reactors has recently gained considerable interest for processes where large fluctuations of the feed flow rate are expected. Load flexibility poses new challenges regarding the reactor design and operation in comparison to the conventional steady state operating mode. These challenges can be man...
Article
Full-text available
Conductive structured catalysts offer significant potential for the intensification of gas-solid catalytic processes owing to their enhanced heat transfer properties. A major drawback is the limited catalyst inventory. Recently, packed foams were proposed to overcome the catalyst inventory limitation. The effectiveness of this concept was proven at...
Article
Kinetic investigations with a commercial H-ZSM-5 catalyst were performed to enable the modeling of the interconversion reactions of olefins in a temperature range from 420 to 490 °C. Different olefin feedstocks ranging from C2 up to C7 were investigated using a Berty-type reactor. Additional mixed olefin feedstocks experiments were performed to ach...
Article
Die (elektro)chemische Stoffwandlung wird sich ändern, wenn Unternehmen die Wertschöpfungskette auf eine regenerative Energie‐ und Rohstoffbasis umstellen. Reaktoren müssen dynamische Änderungen tolerieren, und die ablaufenden Prozesse müssen auf unterschiedlichen Skalen messbar sein.
Article
Full-text available
Reaction kinetic modeling, model-based optimization and experimental validation are performed for the direct synthesis of dimethyl ether from CO2 rich synthesis gas. Among these disciplines, experimental methods and models are aligned in a stringent way of action, i.e., the same setup and models are applied throughout the whole contribution. First,...
Article
A new correlation to account for the radial heat transfer in fixed-beds modeled via a 2D pseudo-homogeneous approach is presented in this contribution. Compared to state-of-the-art heat transfer correlations, no points of discontinuity are included in the definition of the new heat transfer correlation. This enables a direct application of gradient...
Article
Catalyst bed dilution by mixing active and inert particles is common practice for highly exothermic gas phase reactions for balancing the heat generation and heat removal out of the reactor tubes. The predicted reactor performance is commonly calculated assuming a perfectly mixed bed. However, loading a particle mixture into a reactor tube is an in...
Article
The design of dynamically operated fixed bed reactors is a challenging task, especially for highly exothermic reactions. Fluctuations of process conditions such as inlet flow rate and composition can cause losses in product quality, wrong-way behavior or even a thermal runaway which damages reactor and catalyst. We present a methodology for the mod...
Article
Catalytic fixed-bed reactors are well established and frequently used in the chemical industry. Full-scale catalytic fixed-bed reactors are commonly described via pseudo-homogeneous continuum models. The heat transfer is accounted for by correlations that have been predominately fitted under the assumption of constant fluid properties. As a result...
Article
Full-text available
The most recent work in the field of model-based design of catalytic reactors with a special focus on the multi-level reactor design (MLRD) methodology is reviewed. The key idea of this method is to track a fluid element on its way through the — not yet specified — reactor and to optimize the reaction conditions along its way by providing the neces...
Article
Structured catalyst supports and structured reactors offer interesting features to address heat and mass transport challenges in catalytic processes. The present work addresses the unique role of so-called interpenetrating periodic open cellular structures (interPOCS) as a geometrically flexible system enabling in operando adjustment of fluid flow...
Article
Model-based strategies for chemical reactor design proved to be a reliable tool for the systematic design of resource and energy efficient chemical reactors. The adequacy and accuracy of the underlying model equations (e.g. reaction kinetics and kinetics for heat and mass transport) are crucial for the success of such design approaches. However, th...
Article
A comprehensive model comparison is presented for the description of the steady state and dynamic behavior of a wall-cooled fixed bed methanation reactor. Firstly, the maximal conversion predicted by different steady state models is compared and evaluated. Secondly, the dynamic reactor behavior is investigated based on positive and negative step ch...
Article
With the raw material and energy transition to biomass based feedstocks and renewable energy sources, flexible chemical reactor designs which are capable of converting more than one feedstock will become increasingly important in the chemical industry. In the present work, we refer to chemical reactors which can convert multiple different feedstock...
Article
In multitubular fixed bed reactors for heterogeneously catalyzed, highly exothermic gas phase reactions the catalyst bed is usually diluted with inert particles for improving the heat management. To help balancing the heat generation and heat removal out of the reactor by catalyst bed dilution, the active and inert particles have to be mixed as wel...
Article
Model-based design of chemical reactors via dynamic optimization can be performed using a recently developed approach called Multi-Level Reactor Design (MLRD). As a start, the MLRD method, its extensions and applications over the last ten years are reviewed compactly. In the main part of this contribution, a further extension to the model framework...
Article
Based on non-isothermal experiments in an integral pilot scale reactor, the heterogeneously catalyzed gas phase oxidation of propylene to acrolein was investigated at industrial relevant process conditions. From an extensive experimental data set both reaction scheme and reaction rates were derived. Beside the main components propylene, oxygen, acr...
Article
In the present work we propose an efficient and general algorithm for optimization under uncertainty based on the work of Srinivasan et al. (2003). We use specialized cubature rules to speed up the uncertainty propagation step which results in a significant reduction of the overall computational effort. The approach is illustrated by studying the o...
Article
To improve the transport characteristics of a catalytic fixed-bed via optimal design of catalyst pellet specifications such as the pellet diameter it is necessary to account for all physicochemical phenomena influenced by the pellet. For the approximative description of the transport phenomena on the catalyst pellet scale a new shortcut method is d...
Article
de In dieser Arbeit wird ein modellbasierter Ansatz für die Entwicklung maßgeschneiderter, energieeffizienter chemischer Reaktoren vorgestellt. Hierzu wird eine praktikable Größe zur Beschreibung der Energieeffizienz eingeführt und als Zielfunktional der Optimierung genutzt. Zur Veranschaulichung des Ansatzes und der energetischen Bewertungsgröße w...
Article
Cellular structures are considered as alternative catalyst carrier with high potential for process intensification of catalytic reactors due to their remarkable combination of beneficial properties: high specific surface area, low pressure drop and adjustable heat transfer properties. In this contribution, the potential for heat transfer intensific...
Article
Model-based optimization under consideration of uncertainty is an important and active research topic. In order to handle uncertain model and process parameters for the design and optimization of chemical processes, various different approaches have been proposed in the literature. Among these approaches, the application of unscented transformation...
Article
In this contribution, a new analytical approximation to the extended Brinkman equation, based on the previous work of Vortmeyer and Schuster is presented. The new approximation can be utilized for modelling pseudo-homogeneous two-dimensional fixed bed reactors. In the present contribution we focus on the applicability of the new approximation to th...
Article
Multiphase reaction systems are often complex due to the interaction of reaction and transport processes. To design optimal reactors for such systems, a rigorous optimization is necessary. In this regard, this work proposes extensions of a reactor design methodology based on rigorous optimization. Each phase is represented by one fluid element, sub...
Article
We propose a new approach for the synthesis of optimal chemical reactor networks based on the concept of elementary process functions [1] and dynamic optimization. This approach is capable of incorporating process intensification options at an early design stage. Only one single differential equation is required to describe the mass balance of the...
Article
Full-text available
Rasterized representations of geometrical structures are commonplace in science and engineering. They are used in analysis and design of complex geometrical structures; however, the introduced errors for volume and surface estimation are often not considered in detail. To provide insight and information on these effects, in this study model geometr...
Article
In this work, a new approach for taking catalyst deactivation into account in the early stage of reactor design is derived and exemplified by the ethylene oxide synthesis as an industrial relevant case study. In this process, the catalyst lifetime is much larger than the residence time of reactants. The operating conditions over the whole catalyst...
Article
Our contribution demonstrates that the combination of additive manufacturing and electrophoretic deposition offers great potential for the future manufacturing of tailor-made catalytic structures for continuous flow applications. A new protocol for the controlled and homogeneous coating of both electrodes of interpenetrating porous open cell struct...
Article
Full-text available
In this work, a novel synthesis route to produce 2-methyl-5-ethyl-pyridine (MEP) from the cyclic acetaldehyde ammonia trimer (AAT) is explored. The reaction was studied in a semi-batch reactor in the presence of different promoters to adjust the pH of the reaction solution. Among various ammonium salts tested as promoters, ammonium acetate was iden...
Article
Full-text available
The pH dependency of the reaction of acetaldehyde and ammonia to form the acetaldehyde-ammonia trimer has been studied in detail. The acetaldehyde-ammonia trimer is a molecule of interest in organic synthesis, since it can be used as a substrate in many reactions involving acetaldehyde or ammonia. This trimer is well known in the literature but no...
Article
An extension of a proposed design methodology to identify optimal integrated reactor concepts accounting for fast catalyst deactivation is presented. Both solid phase and gas phase are tracked along the reaction coordinate and/or time-on-stream. Optimal fluxes can be provided dynamically and adjusted according to the state at a certain location and...
Article
Radial and axial liquid distribution was measured in a packed column of 500 mm length and 100 mm inner diameter under various gas- and liquid superficial velocities to achieve trickle flow regime. Liquid maldistribution was determined using a liquid collector at the outlet consisting of 21 collection zones of equal area. In this work, as packings i...
Article
Based on previous lab-scale heat transfer experiments performed in a test tube filled with metallic foams, extensive simulations of conjugated heat transfer were performed to systematically investigate the role of different coupling scenarios between the foam structure and the tube wall, using a 3D scanned foam geometry to enable the comparison of...
Article
Owing to their outstanding geometry and material related properties, open-cell foams as structured packing in reactors, columns or heat exchangers offer clear advantages over their traditional counterparts. For the reliable and efficient design of such systems, an accurate knowledge or prediction of the pressure drop is of fundamental importance, a...
Article
Full-text available
Sustainable and efficient processes require optimal design and operating conditions. The determination of optimal process routes, however, is a challenging task. Either the models and underlying chemical reaction rate equations are not able to describe the process in a wide ranges of reaction conditions and thus limit the optimization space, or the...
Article
In this paper, the effective heat conductivity of periodic open cellular structures (POCS) is investigated by means of a systematic numerical study. 3D geometries of different configurations were considered, representing the unit cell volume of the modular POCS. Special emphasis is put on the strut morphology, i.e. the strut cross sectional shape a...
Article
Previously developed kinetic and dynamic models of the hydroformylation of 1-dodecene in a thermomorphic multicomponent solvent system (TMS), consisting of DMF, n-decane, and hydroformylation products, were experimentally validated applying various operation modes, such as batch, semibatch, and perturbed batch operation. On the basis of experimenta...
Article
To maximize the utilization of limited energy and material resources, a new design methodology for chemical processes is proposed based on a multiscale optimization approach. The different levels of the process hierarchy are presented and design aspects are discussed. The methodology is further exemplified by considering a methane steam reforming p...
Article
In this work, a methodology for the design of optimal multiphase reactors is proposed and illustrated on the hydroformylation of 1-octene using a biphasic ionic liquid system with TPPTS modified Rh catalyst. The applied three level design methodology is apparatus independent and thus able to validate existing and generate innovative reactors.On the...
Article
We assess the heat transfer properties of open-cell foams, i.e. cellular materials made of interconnected struts, in view of their use as catalyst carriers. Metallic foams made of FeCrAlY and aluminum with 89-95% porosities and 10-40PPI (pores per linear in.) pore densities were investigated. Geometrical measurements of all samples were performed u...
Article
In this paper, a new method for the identification of the best reaction concept from an overall process point of view is proposed. Using this method the optimal reaction route is determined independent of existing apparatuses and the recycle affecting the reactor is fully considered. The reaction concept and the design parameters of the process are...
Article
In complex chemical processes optimizing the reactor with respect to a stand-alone reactor performance criterium such as product selectivity does not necessarily yield the best process-wide reaction concept. Especially in case of multiphase reaction systems, which often involve complex reaction networks, nonideal phase behavior and multiple recycle...
Article
In reactive multiphase systems, the reactive phase can be manipulated not only by temperature and pressure, but also via coexisting "service" phases. For the exploitation of the full potential of such systems, a model-based reactor design that includes an accurate calculation of the equilibrium composition using advanced thermodynamic models is man...
Article
Grundlage für eine optimale Reaktorauslegung ist die Kenntnis der optimalen Reaktionsführung. Modellbasierte Methoden sind dabei von besonderem Wert, da bei komplexen Systemen eine intuitive Erarbeitung der optimalen Reaktionsführung nicht mehr möglich ist. Am Beispiel der Hydroformulierung langkettiger Alkene wird hier eine auf modellbasierter Opt...
Article
Periodic open cellular structures (POCS) with ideal cubic cell geometry (icPOCS) were manufactured via the selective electron beam melting technique (SEBM). Depending on the cell dimensions (cell length, strut diameter) and cell orientation in respect to the main axis of the cylindrical structures, the icPOCS investigated in this work exhibit diffe...
Article
Der Entwurf maßgeschneiderter neuartiger Katalysatorträger erlaubt eine verbesserte Reaktorleistung durch gezielt einstellbare Strömungs- und Stofftransportcharakteristika. Die numerische Geometrieerzeugung, Strömungssimulation und das Particle-Tracking zur Stofftransportuntersuchung liefern das hierfür erforderliche Verständnis für Struktur-Transp...
Conference Paper
Optimal Reactor Design for the Hydroformylation of Long Chain Olefins in Thermomorphic Solvent Systems Benjamin Hentschel1, Andreas Peschel2, Hannsjörg Freund3, Kai Sundmacher1,2 1Process Systems Engineering, University of Magdeburg, Magdeburg/DE 2Max Planck Institute for Dynamics of Complex Technical Systems, Magdeburg/DE 3Chemical Reactio...
Conference Paper
In the context of process intensification, structured catalyst supports offer the advantage of a better control on the geometrical properties and consequently on the effective transport properties of the catalytic bed. In this regard, open-celled foams are of particular relevance. They represent a class of consolidated porous media which is charact...
Conference Paper
Structuring concepts for catalytic reactors have drawn much attention in recent years as a promising option to achieve process intensification in the chemical industries. However, for the case of solid foam monoliths the quantitative understanding of the structural influence of the local foam structure on the flow field and the heat and mass transp...
Conference Paper
Structuring concepts for catalytic reactors have drawn much attention in recent years as a promising option to achieve process intensification in the chemical industries. However, for the case of solid foam monoliths the quantitative understanding of the structural influence of the local foam structure on the flow field and the heat and mass transp...
Article
In this work we investigate the heat transfer within single phase tubular reactors packed with open-cell metal foams. Special focus is on the role of the coupling between the foam packing and the reactor tube wall. Steady-state heat transfer experiments were carried out in a tube of 28 mm inner diameter packed with different open-cell foams using N...
Article
A fundamental approach to separate azeotropic mixtures by tuning the phase behavior using pressurized CO2 as a tunable solvent was studied. Following this new process concept, two process variants were put forward to separate aqueous pressure-insensitive and pressure-sensitive azeotropic mixtures. The two process variants were studied in process si...
Article
Energieeffizienz ist ein wesentlicher Baustein nachhaltigen Wirtschaftens und unabdingbare Voraussetzung zur Erreichung aktueller klimapolitischer Ziele. Die von der Helmholtz-Gemeinschaft Deutscher Forschungszentren geförderte Energie-Allianz „Energieeffiziente chemische Mehrphasenprozesse” bündelt Kompetenzen und Forschungsaktivitäten im Bereich...
Article
An indirect hydration process route for the production of cyclohexanol was proposed by Steyer et al., which uses formic acid as a reactive entrainer (Steyer, F.; Freund, H.; Sundmacher, K.Ind. Eng. Chem. Res. 2008, 47, 9581−9587; Steyer, F.; Sundmacher, K.Ind. Eng. Chem. Res. 2007, 46, 1099–1104). This route overcomes several limitations of the con...
Conference Paper
In this work, a new method for the identification of the best reaction concept from an overall process point of view is proposed. Using this method the optimal reaction route is determined independently of existing apparatuses and the recycle affecting the reactor is fully considered. The reaction concept and the design parameters of the process ar...
Article
In the catalytic hydrogenation of benzene to cyclohexane, the separation of unreacted benzene from the product stream is inevitable and essential for an economically viable process. In order to evaluate the separation efficiency of ionic liquids (ILs) as a solvent in this extraction processes, the ternary (liquid + liquid) equilibrium of 1-alkyl-3-...