Challenges in Reaction Engineering Practice of Heterogeneous Catalytic Systems

Milorad P. Dudukovic*; Patrick L. Mills┼    * Chemical Reaction Engineering Laboratory (CREL), Department of Energy, Environmental & Chemical Engineering (EECE), Washington University in St. Louis (WUStL), St. Louis, Missouri, USA
┼ Department of Chemical and Natural Gas Engineering, Texas A&M University-Kingsville (TAMUK), Kingsville, Texas, USA

Abstract

The Topsøe Catalysis Forum was created as a framework for an open exchange of views on catalysis in fields of interest to Haldor Topsøe. The forum scope included a discussion of new catalytic reactions and new principles of catalysis in an attempt to jointly look beyond the horizon (Topsoe catalysis forum, 2013). The 2013 meeting was dedicated to Modeling and Simulation of Heterogeneous Catalytic Processes and provided an opportunity to review and discuss the current state of the art in the engineering practice of heterogeneous catalytic systems (Topsoe catalysis forum, 2013). The primary objective of this chapter is to capture key elements of our conference presentation (Dudukovic, 2013) that were focused on multiscale reaction engineering concepts and to what extent these have been applied in the commercial implementation of multiphase heterogeneous catalytic reacting systems. Of particular interest is to identify common approaches and tools used in practice, and to examine their effectiveness in the scale-up and development of more efficient, environmentally friendly catalytic processes. Current practice is limited by the availability of experimental tools to increase the reliability of scale-up, and by the lack of more robust models for analysis and optimization of reactor systems for existing processes or the design of new reactor systems for implementation of new catalytic chemistries. From an economic perspective, the pursuit of short-term financial objectives favors the use of existing reactors with minimal modifications with performance analysis based upon simplified approaches. A longer-term perspective on the development and implementation of more advanced experimental techniques and modeling approaches for reactor analysis that are applicable to commercial reactor conditions would accelerate the development of new process technologies and result in reduced risk with associated lower costs.

Keywords

Catalyst

CFD

Design

Experimental

Heterogeneous

Modeling

Multiphase

Multiscale

Process

Reactors

Scale-up

Simulation

Tomography

1 Introduction

Multiscale process engineering (MPE) attempts to describe various physiochemical phenomena in process systems over a large range of time and length scales using various modeling approaches to provide robust predictions of process system behavior. MPE is gaining increased momentum as the preferred approach for developing robust process models that can be utilized for efficient development of sustainable solutions for emerging technologies. This approach has been advocated by experts in the reaction engineering field (de Lasa et al., 1992; Dudukovic et al., 2002; Krishna and Sie, 1994; Lerou and Ng, 1996; Schouten, 2008; Tunca et al., 2006) and has been the subject of recent conferences dedicated to multiscale multiphase process engineering (MMPE) (MMPE, 2011, 2014) as well as monographs on multiscale process modeling (Li et al., 2013). However, implementing this approach for existing and new process technologies, whose profitability is always impacted by variables such as feedstock price and composition, competition from other companies, and other business platform dynamics, could potentially benefit by synergistic collaborations between universities and industry than commonly practiced today (Huesemann, 2003; Schouten, 2008). These observations are reinforced by more than 40 years of experience of interactions between academia and industry at Chemical Reaction Engineering Laboratory (CREL) at the Washington University in St. Louis (Dudukovic, 2009; Mills and Dudukovic, 2005a, 2005b).

Since 1974, the objectives of the CREL have been to advance the state of the art of multiphase reaction engineering via education and research involving students and to transfer these advances to industrial practice. Recognizing that reaction engineering, as an academic discipline, can only develop new advances if it is related to industrial practice, cooperation and financial support was sought and received from numerous companies located in five continents as well as from various national government funding agencies (e.g., NSF, DOE, USDA, and DARPA). The financial support for research in CREL originated from various industrial sectors, including petrochemical processing, bulk and specialty chemicals, pharmaceuticals, semiconductor grade silicon production, biotechnology, and specialty materials. Many research programs involved heterogeneous-catalyzed kinetics, catalysis, and the analysis of catalytic reactors (Chemical Reaction Engineering Laboratory, 2014).

It is noteworthy that the precompetitive research generated by CREL in-house initiatives using consortium funding from various companies over the past four decades produced many graduates that collectively represented a strong reaction engineering workforce that accomplished notable technical advances in a host of diverse technologies (Chemical Reaction Engineering Laboratory, 2014). Instead of embracing this model of pooling resources, sharing the knowledge acquired in a broad consortium like CREL, utilizing that knowledge for in-house projects, and creating new initiatives for reaction engineering research, industrial trends for the last 10-15 years or so have largely placed decreased emphasis on precompetitive research and the development of core competency groups in reaction engineering and the process sciences. Various reasons for reducing emphasis can be identified, but it can often be traced back to an assessment of costs for supporting these groups within a company's organization. For example, when the DuPont Company sold the fibers and textiles unit in 2003 (Brubaker, 2003), various core competency groups located in the corporate science and engineering research laboratory were eventually downsized, reorganized, or disbanded owing to reduced needs from the remaining business platforms to provide improved technology or plant operational support. Other business examples can be identified in the open literature for similar or other related reasons. In addition, it has been observed by one of us (P. L. M.) over the years as an industrial practitioner that changes in business direction has sometimes lead to the loss of researchers with strong skills in heterogeneous catalysis and reaction engineering, or decreased support for a core group with reaction engineering expertise. Nevertheless, the need still exists in companies to have a skilled technology workforce that has the knowledge and experience to either drive the development of next-generation processes, or to provide expert guidance and critique of work performed by external engineering technology businesses who may be contracted to perform it as part of a larger project on process development (Ericsson et al., 2007).

Another key aspect that has impacted support and development of new reaction engineering principles for next-generation heterogeneous processes is connected to increased emphasis on the ownership of intellectual property by both companies and universities. The literature on this topic is extensive, but a recent article highlights some key issues from a university perspective (Hallet, 2014). Generally, development of an acceptable legal agreement can consume notable time and resources. However, examples can be cited on successful agreements between universities and industrial partners (Glicksman, 2003). The above-cited developments and others that are not set forth here for brevity have generally had a negative effect on the reliability of scale-up of new processes. Thus, it is appropriate to first examine the difference in current prevailing approaches and what is needed in order to improve the technologies for heterogeneous catalytic processes.

In the distant past, profit maximization was the primary guiding principle in process development and operation. However, the key future challenge for our profession includes meeting the global energy, environmental, and material needs of the world using more efficient processes that can eliminate or dramatically reduce wastes while maintaining profitable (Dudukovic, 2010; Schouten, 2008). This is necessitated by the realization that global damage to the environment is the product of three factors: overall process inefficiency, consumption per capita (which is proportional to Gross Domestic Product (GDP)), and total population (Dudukovic, 2009, 2010). As political and economic pressures prevent any foreseeable actions in curtailing the last two factors, the only strategy for the future that can make our processes sustainable is to work relentlessly to increase all types of process efficiency. Use of multiphase catalytic systems is prevalent in most processes that chemically convert various raw materials to final products for the market (Fig. 1.1;...