Researchers Gain New Insight into Activating Fischer-Tropsch Catalysts

	The image on the left shows an array of model Fischer-Tropsch catalyst particles, as seen using a special scan- ning tunneling microscope at NETL. The image on the right is an enlargement of the surface of one of these particles showing a regular array of closely packed oxygen atoms, which appear as small circular ‘bumps’ in the images.

The Fischer–Tropsch (F-T) process is a set of chemical reactions that historically has been used to produce a petroleum substitute from coal, natural gas, or biomass by nations looking for an alternative to importing it. The F-T process has received intermittent attention as a source of low-sulfur diesel fuel whenever the cost of petroleum gets sufficiently high, but can also be used to create hydrogen from the same raw materials, and are therefore of interest to researchers who are developing new technologies for powering a fuel cell more economically.

Catalysts are a key component of the F-T process. A common catalyst is iron oxide, Fe₂O₃ (commonly referred to as rust), which is transformed into Fe₃O₄, FeO, Fe, and Fe-carbides during the F-T process. The arrangement of the surface atoms on the iron compounds dictates how reactive these catalysts are, but although F-T catalysts have been in use for several decades, there is no experimental data on how the arrangement of atoms on the surface of these catalysts evolves during the F-T process.

Publication on CO₂ Reuse Photocatalysts One of Top 10 Most Accessed Papers in 2010

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	SEM image of (A) t-CdSe/Pt/TiO2 photocatalyst, scale bar 100 nm, and (B) EDS mapping of the same sample, scale bar 80 nm (Se: yellow; Cd: red; Pt: pink).

It is always nice to learn that your work is appreciated. The Journal of Physical Chemistry Letters, published by the American Chemical Society, recently announced that one of NETL’s publications, titled “Visible Light Photo Reduction of CO₂ Using CdSe/Pt/TiO₂ Heterostructured Catalysts” was one of its top 10 most accessed journal articles in 2010.  This distinction illustrates the scientific community’s interest in NETL’s development of new carbon dioxide (CO₂) management technologies.  Whereas much of NETL’s carbon management research is oriented towards capture and long-term storage of CO₂, as a means of abating global warming, NETL is also conducting research on alternative ways to convert some of the CO₂ that we produce into useful products. The trick, of course, is to find a way to do this at a reasonable cost.

The paper that has received all of this attention describes the synthesis and characterization of a new light-activated catalyst, and the potential of this catalyst to enable conversion of CO₂ into value-added fuels, such as methanol and methane, and other chemicals.  Ideally, the money made by selling these products will be used to offset some of the costs of capturing, storing, and monitoring the stored CO₂. Previously investigated catalysts for this application were activated by ultraviolet light, which makes up only 1–5% of the sunlight reaching Earth’s surface, but the new catalyst is activated by visible light, which makes up most of the sunlight that reaches us. Visible light activation will thus increase the efficiency of the catalytic process, an advance of paramount importance for CO₂ reuse applications. Furthermore, the activity of the catalyst can be systematically tuned to use different colors of visible light by controlling the size of the semiconductor nanocrystals that make up the catalyst.

NETL Files Patent Application for High Speed Particle Imaging System

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	Figure 1. HSPI system recognizing and simultaneously tracking more than 500 particles in a dense particle flow field of NETL's Cold Flow Circulating Fluidized Bed experimental unit.
	Figure 2.  NETL's HSPI system is being used in medical applications to accurately image blood flow, which closely resembles the high concentration particle flow of fossil energy processes. Image courtesy of the Medical Devices Laboratory--McGowan Institute

Imagine following a particle smaller than a grain of salt among millions of particles moving randomly in a high-speed liquid or gas stream. High concentration particle flows are not only microscopic, they are opaque, and their high speed has made them very difficult to study. So, although high concentration particle flow is critically important to many chemical, energy, biological, and food processes, until recently, researchers could not see how particles moved within them. NETL had developed computational fluid dynamics models of HCPFFs that can be used to design and optimize new fossil energy systems, but they could not tell how accurate their models were.

NETL has studied high concentration particle flow fields (HCPFFs) because they are important in fossil energy applications such as fluidized beds, pulverized coal combustion, advanced gasification, CO₂ capture and sequestration, and gas stream clean-up. Now, NETL has developed a new high speed particle imaging system (HSPI) that allows researchers to observe, measure, and study particle motion via thousands of high-speed video frames. The HSPI system measures the velocity of fluids and can accurately recognize and measure particle motion inside HCPFFs (Figure 1).

A patent application for the HSPIV software has been filed with the U.S. Patent Office, and discussions are underway with private sector companies who may be interested in licensing the technology. Additionally, the HSPI system has left the laboratory and is currently being used at a chemical/energy industry research lab in Chicago (PSRI), and at the McGowan Institute for Regenerative Medicine in Pittsburgh to study blood flow—a mixture of fluid and high particle concentrations (blood cells)—in a respiratory assist catheter (Figure 2).