Over the past few months I tried to collect as much information as I could find on the iron-potassium oxide catalysts routinely used in the work by Holmlid et al. After much research and note taking, it seems apparent to me that the probable main reason why experimenters have been having several difficulties with replicating the results is the preparation involved for activating the catalysts, or in other words to render them catalytically active.
This information is widely published in the mainstream scientific literature, but this is not immediately obvious by just reading Holmlid's papers. In fact, very little is directly available about them just by reading his papers. One has to follow the references and read the related papers cited there. These are the two main works he usually cites when referring to these catalysts:
- G. R. Meima and P. G. Menon, Appl. Catal. A 212 (2001) 239.
- M. Muhler, R. Schlögl and G. Ertl, J. Catal. 138 (1992) 413.
To cut a long explanation short, it seems that upon specific conditions, in particular those similar to the industrial processes they're normally involved with, these catalysts undergo various structural transformations. The main defining characteristic is the formation of an unstable potassium ferrite (KFeO2) compound on their surface, which is generally considered to be the main catalytically active phase (this compound in isolation is as active as the industrial catalyst).
My understanding is that this compound is formed during these conditions:
- During catalysts synthesis from precursor materials at about 800-850 °C in air
- During actual process conditions in the presence of hydrocarbons and oxygen at about 600-650°C (typical operating temperature)
- Simply by heating the catalyst in a non-reducing residual atmosphere under vacuum conditions above 600°C
The reaction is as follows:
Fe2O3(s) + K2CO3(s) => 2 KFeO2(s) + CO2(g)
Interestingly, the compound is characterized by a dark olive green color, which can be used to detect its formation. Under ambient air conditions the compound is reported to quickly decompose back into red hematite (Fe2O3) due to CO2 absorption, with water catalyzing the reaction. "As received" catalysts from long-term storage under uncontrolled conditions therefore are mostly composed (at least on the surface) of hematite and potassium carbonates, and are not immediately catalytically active. Any activation procedure would have to be preferably done in-situ.
A few weeks ago to test the hypothesis that just calcinating (heating in air) for a relatively short period of time pre-formed, commercially available industrial iron oxide catalysts similar to those used by Holmlid could restore at least part of the potassium ferrite surface layer (by the above reaction) with a possibly noticeable change of color, I asked Alan Smith (our LENR-Forum moderator), who had a certain amount of these catalysts at disposal, to calcinate some of them for 90 minutes at 900°C and take a couple photos before and after the treatment. The entire procedure overall required minimal effort on his part.
It did appear that the "after" catalysts changed slightly in color, at least in part confirming existing information in the literature and that at the right conditions potassium ferrites (KFeO2) might have been indeed formed. Note that the white patina visible in the "before" photos is likely potassium carbonate. Unfortunately I haven't been provided photos showing their state several hours later after storage in air. From various reports it seems that this occurs visually within hours. The so-treated catalysts have not been tested in an experimental apparatus under a hydrogen atmosphere either.
I'm wondering if other experimenters with access to basic materials and equipment would be interested in performing some tests to confirm some of the characteristics of these catalysts. I can provide all references and information needed, but in absence of public of interest on the subject putting too much effort early on this thread would probably not be very useful.
Potentially interesting activity diagram from http://dx.doi.org/10.1006/jcat.2002.3725