The question I am now posing involves how scientific papers should be presented where the author faces a dilemma. On one hand, the author wants to show something that might lead to more widespread use, but on the other hand, the information might have more general use. The first point is obviously desirable if in fact the use proposed makes sense, but even if it does not it might still make sense while reporting to funding agencies. The second point involves the dissemination of knowledge, and the problem is if it is presented in one way, it may not be seen by others for whom it may be more useful. The huge output of scientific papers means that nobody can read any more than a tiny fraction, and everybody has to have some form of very coarse screening otherwise they never get anything done.
 
These thoughts were started, for me, by a recent paper (Angew. Chem. Int. Ed. 53, 9755 –9760) which claimed to give an interesting approach to biofuel production, but I feel the more interesting aspect of it was the implied underpinning chemistry. The basic process involved three reactions that started with molecules such as furfural and hydroxymethyl furfurals, which are acid degradation products of carbohydrates. Furfural is readily obtained from pentoses because it steam distills out of a reaction in which carbohydrates are acid hydrolysed at higher temperatures, but hydroxymethyl furfural does not do this, and instead it degrades further. It can be isolated, but at a cost, and at only moderate yield. So, before we go much further, this paper will have questionable direct applicability because it involves relatively expensive starting materials that represent only a part of the initial resource.
 
But it is what happens next that is of interest. The authors carry out an aldol condensation of the furfurals with acetone, thus getting C8, C9, C10, C16, etc materials. Furfural gives the furan ring and the unsaturated ketone. These are now reacted at elevated temperatures and pressures with NbOPO₄ in the presence of hydrogen and a Pd catalyst. The interesting part now is that the NbOPO₄ has the ability to pull out the oxygens, including the furfural ring oxygen and the ketonic oxygen (although this may be a dehydration reaction as the carbon-carbon double bond becomes hydrogenated), with the result that we end up with linear hydrocarbons.
 
The niobium phosphate gets a 94% yield of hydrocarbons, whereas aluminium phosphate gets a zero yield of hydrocarbons, while the palladium there catalyses the hydrogenation of the double bonds. Actually, the phosphate is not that important as Nb₂O₅ gives the same yield of hydrocarbons. According to the authors, what happens is that the bulk Nb – O  – Nb groups break, permitting a Nb – O – C  bond to form, and a nearby hydrogen atom can transfer to the carbon atom.
 
The question then is, what use is this to biofuels? Superficially, not that much because the problem of getting furans probably makes this uneconomic. Not only that, but while the C16 hydrocarbons would make excellent diesel, linear C8 hydrocarbons are not at all attractive as fuels, as lying in the petrol range and having an octane number approaching zero makes them undesirable. What I would find more interesting, though, is how this catalytic system would function with lignin, or lignin derived smaller molecules. While lignin polymerization has essentially no pattern, nevertheless many of the linkages occur through C – O – C bonds. If they could be hydrogenated, and the methoxyl groups removed, it might be a breakthrough in biofuel development. The question then is, why did these authors not try their reaction on lignocellulose to see what would happen? Perhaps they did, and perhaps there are more papers coming, but I do not feel that is constructive. We need to see the fewest papers presented consistent with getting all information over, so as to reduce the deluge.