Jan
7
A Catalyst to Remove Water From Biofuels
January 7, 2010 | 6 Comments
Daniel E. Resasco leads an Oklahoma University research team including Steven Crossley, Jimmy Faria, and Min Shen that has published a paper in Science where they have found a way that stabilizes water-oil emulsions and catalyzes reactions at the liquid/liquid interface. Or more succinctly, they can separate out the main liquid components in biofuel processes. While it’s not a process yet, the innovation to use a catalyst could have dramatic impacts in energy use, complexity and progress in biofuel product processing.
Here we often look at new innovations without the “Whole Picture” as a process engineer would in designing a plant to take in raw materials and put out sale-able products. Along the way of any process there is equipment, energy use, housing, personnel and an incredible array of considerations. It all takes a great deal of time, with intense rechecking, as an error could be an economic and time disaster. But innovations that would separate out water from a fuel process solution offer immense opportunities in cost controls and maybe simplification.
Just to put the OU team’s work up for significance, the team is saying the catalyst is recoverable and reusable. Perhaps ‘getting the water out’ is going to get simpler easier and cheaper.
The team notes that such a recoverable catalyst that simultaneously stabilizes emulsions would be “highly advantageous” in streamlining processes such as biomass refining, in which the immiscibility and thermal instability of crude products greatly complicates purification procedures. One of the goals can be described as a metaphor such as trying to get the alcohol out of a bottle of beer. The other is that many in process fuels are going to be jell like at lower temperatures. The metaphor would be trying to get the sugar out of Jello after it sets. These kinds of issues are what seem to delay getting so many great innovations to working processes. This view imparts some significance to the OU team’s work.
The team deposited palladium onto carbon nanotube–inorganic oxide hybrid nanoparticles. The oxides are hydrophilic, and attracted to the water; the carbon nanotubes are hydrophobic, and prefer the organic layer. Those are called ‘Janus’ catalysts and are described by Dr. David Cole-Hamilton of University of St. Andrews, Scotland in an accompanying Perspective piece in Science. The catalysts sit at the surface like a large surfactant molecule. But unlike surfactants (think detergent), the nanoparticles are solids that can be easily separated out. Otherwise the process would trade one problem for one of getting the surfactant out.
Carbon Nanotube Palladium Catalyst. Click image for more info.
The team explains, “Rather than carrying out multiple consecutive purification steps during refining to separate out the hydrophilic by-products incompatible with fuel applications, it would be desirable to perform sequential reactions under phase-transfer conditions in a single reactor medium . . .” The problem lies in getting out surfactants and solids out as well as separating the oil and water, so “the most efficient way of catalyzing reactions is to place the solid catalyst at the liquid/liquid interface and to maximize the extent of interface by creating an emulsion . . .” The OU team offers that “. . . the concept of solid particles that can simultaneously stabilize an emulsion and catalyze reactions in both phases becomes an attractive proposition.”
For the study, the team explores two preparations with nanotubes of different types that affected the deposition of palladium. The paper shows results obtained for several important reactions in biomass-refining chemistry: the elimination of oxygen and the condensation of small molecules. Oxygen elimination is needed to improve the low stability caused by the high reactivity of the oxygenated functional groups in molecules such as the phenolic compounds derived from lignin. Condensing out small molecules is particularly important to increase the molecular weight of those light fragments derived from the less refractory parts of the biomass such as cellulose and hemicellulose.
The study results may solve in a large way the issues in biofuel process design. While not a whole neat and complete package, the catalyst proposal does cover important ground. The questions still out there such as economic cost for the catalysts themselves, the actual process equipment requirements and the energy requirements and simply the economics of scale prospects are a ways out there. But this kind of innovation shows the serious nature of how research is progressing.
The team says, “The advantage of operating in a biphasic (the oil and water still combined) system, with the catalyst at the liquid/liquid interface, is the possibility of conducting the sequential reactions in a single reactor instead of two. Our results highlight the preliminary applications of solid catalysts localized at the interface between two liquid phases. We anticipate that tailoring such emulsion-stabilizing solids with additional catalytic functional groups will facilitate a broad range of reactions.
“With solid-stabilized emulsions, a continuous process could be designed in which the two homogeneous phases coexist with the emulsion in a layered configuration: oil/emulsion/water. One can achieve full conversion on both sides of the emulsion followed by constant removal of oil-soluble products from the top layer and water-soluble products from the bottom layer while the reaction keeps occurring in the emulsion.”
Now those are comments to make engineers involved from ethanol up to heavy alcohols, algae oils and synthetic fuels sit up and notice.
Lastly, a look at the web page that covers Resasco’s research suggests that Conoco Phillips has some role (The lab is called the ConocoPhillips Catalysis Laboratory) in supporting the research. Conoco Phillips has been gathering experience in biofuels and the fact that they’re there in a major way is a very good sign. Maybe an announcement of hundreds of billions for research feels good, but hard steady cash solving actual process matters is every bit as important and deserves a thank you.
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