http://www.anl.gov/PCS/acsfuel/preprint%20archive/Files/35_1_BOSTON_04-90_0023.pdf
In several earlier dispatches, some time ago now, we reported the US Government's sponsorship of a Coal liquefaction pilot plant project at Wilsonville, Alabama; wherein a "two-stage" Coal conversion process was developed and studied.
Herein, we document what we perceive to be related studies of Coal liquefaction processes by the University of Alabama.
And, we submit that the technology explained herein could be a unique and forward-thinking concept, perhaps indicating a path to follow which would help to make Coal conversion processes more efficient.
Attempt at explanation follows our somewhat technically dense, and extended, excerpts from:
"Coal Liquefaction Using Intermetallic Hydrides as Both Catalysts and Hydrogen Distribution Agents
James E. Smith, Jr. and Scott D. Johnson; The University of Alabama in Huntsville, AL
Several intermetallic alloys are capable of forming reversible hydrides by storing atomic hydrogen within their metal matrices at densities that may exceed that of liquid hydrogen. In this paper we examine FeTi. LaNi5, CaNi5, Mg2Cu, and Mg2Ni as materials to both transport and distribute hydrogen to slurried coal while catalyzing the liquefaction process. Liquefaction experiments were performed in 5 ml microreactors using Alabama Black Creek coal slurried in 1-methylnaphthalene at temperatures of 316, 371, and 427 C ... .
Catalyst activity followed the general trend of CaNi5 -LaNi5 > FeTi > Mg2Cu > Mg2Ni with total conversions of greater than 60% obtained from the first three catalysts. As the reaction temperature increased, the higher conversions favored the production of additional preasphaltenes and oils. The CaNi5 catalyst proved to be the most selective towards oils. Noncatalyzed conversion results were approximately half that of the most active catalytic intermetallic hydrides at the temperatures investigated. The catalysts were recovered ... and with the exception of LaNi5 showed no visual evidence of coking. Previous results have shown that FeTi catalyst was deactivated by 4% after liquefaction at 260 OC and 4.14 MPa. A possible explanation for the increased activity at reduced severity may be that hydrogen is supplied to the surface by the intermetallic hydride making the surface self-cleaning.
Nickel molybdenum and cobalt molybdenum supported on alumina have been studied by many researchers as catalysts for direct coal liquefaction. These bimetallic supported catalysts show increased activity, stability, and selectivity when compared with pure nickel and cobalt similarly supported on alumina, but deactivate rapidly under liquefaction conditions. These surfaces may be and often are blocked by metal contaminants or organic layers which will not permit hydrogen chemisorption, thereby reducing the
liquefaction rate compared to that of a fresh catalyst charge. What is needed is a self cleaning approach which continuously renews the surface while delivering atomic hydrogen to the catalytic sites.
Several intermetallic alloys are capable of forming reversible hydrides by storing atomic hydrogen within their metal matrices. This paper concentrates on FeTi, Mi5, CaNi5, and Mg-Cu. When properly conditioned and
exposed to hydrogen at room temperature, ties, alloys form reversible metal hydrides ... .
Depending upon the temperature and pressure, these intermetallic matrices are capable of reversibly storing hydrogen at densities exceeding that of liquid hydrogen. Since the absorption process is exothermic, a matrix which has been fully hydrided at room temperature will desorb atomic hydrogen at the metal
surface when subjected to reactor temperatures. A drop in pressure will also result in the release of hydrogen from the intermetallic hydride. Thus, these compounds will deliver atomic hydrogen to the catalytic surface when taken from ambient to reaction temperature.
Intermetallic compounds differ chemically from their pure components. For FeTi, the elements react with carbon, oxygen, and nitrogen forming extremely stable compounds. When alloyed, this intermetallic compound has the hydride properties previously described and is virtually immune to oxidation, nitration, and carbide formation under normal liquefaction reactor conditions.
Furthermore, FexTi alloys have been shown to have substantial catalytic activity towards hydrogenation reactions.
These compounds also serve as bimetallic catalysts, and their use in the bulk form eliminates the pore diffusion, pore blockage, and particle sintering problems encountered with supported metal catalysts. Supported metal catalysts deactivate by coking resulting in site blockage and metals deposition which causes pore mouth clogging.
(As we have several times documented, catalyst clogging via Carbon deposition have been frequently encountered problems in indirect Coal liquefaction processes. As we also reported, significant progress, as demonstrated herein, had been made in preventing and resolving those problems.)
... the catalyst seems to be more effective as the temperature increases, which causes the alloy to release additional hydrogen from its matrix while improving the reaction rate.
... we conclude that the following series described the trends in activity for the catalytic hydrides studied to date: CaNi5 - LaNi5 > FeTi > Mg2Cu > Mg2Ni.
This research was supported by the Alabama Research Institute under grants ARI 85-611 and ARI 86-607 and Alabama Department of Economic and Community Affairs under grant number ARI 89-601."
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As we, after some discussion among ourselves, take this, researchers in Alabama figured out how to combine the functions of both traditional, Fischer-Tropsch type, indirect Coal conversion catalysts, which we believe to be mostly derived from the Iron-Nickel Group of elements, and Hydrogen-donors, which are most often associated with direct Coal liquefaction technologies, such as the West Virginia Process. In this Alabama technology, the catalysts sound as if they go through some sort of Hydrogen "loading" process, and, if so, would likely have to be somehow rejuvenated on a cyclic basis.
However, again, such Hydrogen donation by the catalyst, according to this report, seems to inhibit Carbon deposition, as in the statement that the catalysts are "self cleaning", and subsequent catalyst deactivation is thus prevented. And, one is led to speculate that such technology might be put to good use in Carbon Dioxide-Methane reforming, to synthesize higher hydrocarbons, where such Carbon deposition on, and deactivation of, the catalyst surfaces has also been noted as a problem.
If so, then this Alabama technology might represent not just an advancement in the science of Coal conversion, but a guide to more efficient Carbon Dioxide recycling, as well.