Catalyst Screening Gets Faster

Automated chromatographic alignment enhances high-throughput testing

By Mark Krawczyk, Charles P. McGonegal, Matthew J. Schmidt, Mike McCall and J. W. Adriaan Sachtler, UOP, and Martin Plassen, Arne Karlsson and Elisabeth M. Myhrvold, SINTEF Materials and Chemistry

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The application of combinatorial or high-throughput methods to the discovery and commercialization of new heterogeneous catalysts requires a means of rapidly screening the performance of novel materials. To meet this requirement, UOP Honeywell and SINTEF have a long history of collaborating, developing and optimizing new and efficient tools capable of measuring key catalyst-performance variables. A critical enabler of combinatorial screening is high-speed analysis. However, in parallel testing units, complex analyses often demand a significant amount of time to manually reprocess files. In some cases, this could incur a reduction in testing rate. Furthermore, post-run reprocessing efforts frequently are complicated, tedious, time-consuming and prone to human error. In this article, we will illustrate an effective real-time automated solution to correcting retention time shifts across multiple gas chromatographs with multiple detectors that might lead to peak misidentifications. The solution directly integrates multivariate correlation-based chromatographic alignment software into the high-throughput test control software.

The search for a suitable prototype catalyst may require many experiments to screen different chemical elements, additives, substrates and treatments. In addition, evaluation of catalyst substances must take place at relevant temperatures and pressures using applicable chemical feedstocks. This often necessitates a very large number of tests. High-throughput testing and combinatorial approaches have emerged not only as a contributor to catalytic science but as an enabler to product commercialization. The sequential strategy requires a workflow process incorporating catalyst library design and construction, primary or secondary screening, and piloting. Figure 1 shows one of our high-throughput systems for catalyst screening.

High-throughput capabilities and infrastructure for catalyst discovery at UOP Honeywell utilize an integrated end-to-end methodology. It encompasses: a combinatorial synthesis of material libraries; catalyst preparation using ion exchange and impregnation; catalyst finishing such as oxidation, steaming and chlorination; catalyst pretreatments done either in-situ or ex-situ; and parallel testing of catalytic formulations to rapidly identify prototypes for commercialization. Specific program objectives have led to the development and application of innovative tools, novel experimental methodologies, predictive performance models, and optimization tools for heterogeneous catalyst discovery. The tools and methodologies routinely are used in catalyst discovery and technology development projects with broad economic and societal returns.

The current infrastructure supports a wide range of UOP Honeywell process-development, catalyst-development and commercial-support projects. By applying unique testing methodologies, the coverage of process technologies with assorted feedstocks and reactor phase regimes is extensive. Furthermore, the infrastructure is flexible to allow exploration of future process technologies.

The growth in the processing of high-molecular feedstocks with more-complex product distributions (Figure 2) presents challenges for high-speed analytical methods, making innovations necessary. For example, this paper discusses the development of automated chromatographic alignment tools to ensure proper peak identifications with minimal human intervention.

The defining feature of a high-throughput system is the quantity of analyses per unit time. In this case, the analysis is defined as a gas chromatograph (GC) injection. As those skilled in the art of high-throughput testing well understand, conducting a statistically meaningful experiment requires multiple injections. These are achieved by a combination of a process flow scheme that directs multiple reactors to an instrument and the use of several analytical instruments per test system. The length of the analytical method, product complexity, the requested test length, and the anticipated testing demand determine the numbers of reactors multiplexed onto a given analytical instrument and the total number of instruments per system.

The speed of analysis is a critical parameter and many tactics are used to reduce the analysis time. For example, the number of components individually identified and peak quality may be reduced to gain speed for screening. (More-detailed analyses can be done on selected samples in secondary or pilot testing.) Even when some loss of resolution is accepted for speed, the repeatability of the analysis must remain high. With several reactors being tested by one instrument, the injection-to-injection variability must remain smaller than the performance differences in the materials being tested. Likewise, analyses must be consistent across multiple instruments.

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