Posted on 12/04/2015 12:48:06 PM PST by Red Badger
Butane is a bastard gas.
The conversion selectivity is important, of course, for final product purity, but if it takes two gallons of ethanol to produce one gallon of butanol, then it is not economically worth the effort of using up that much food stock to make a fuel that we are currently awash in thanks to fracking.
most chemical conversion processing uses titer recycling so any reaction products that are not the final product in this case butanol are recycled to the head of the process that would be why selectivity is important no side reaction producing things that cannot be recycled. ethanol goes in one end and 99% of that is converted to butanol at the other end eventually assuming 2 recycles a process loss of 3% would not be unreasonable. if the catalyst is stable enough to drive the reaction to completion in one step then no recycling is needed since 99% of the original ethanol is now butanol. since ethanol has less btu per gallon one gallon of ethanol cannot make one gallon of butanol thermodynamics dictates that some energy must be lost to gibbs again taking them at their word of a 99% conversion on a btu to btu basis you would need 1.4 gal of ethanol to make one gal of butanol thats suppling the reaction energy probably process heat from an external source, resistance heaters, natural gas, coal whatever you can get the reaction heat from for the catalyst. put another way at 99% conversion and exterbal reaction energy one gal of ethanol should make .68 gal of butanol but that .68 gal of butanol has the HHV energy equivalent of .99 gal of ethanol its chemically denser in enegry per gram of mass and ml of volume as well. an even better alcohol for fuel would be propanol its denser still and already allowed in gasoline in quantities of 20% as a registered oxygenated additive. it does not have to be labeled much like MTBE it is just allowed as a componet of RFG. Propanol is made from propane or propene but some bacteria can synthesize it the goal is to take those genes and put them in a wood eating bug. all the higher alcohols propanol,hexanol,heptanol have octane ratings over 100, and energy densities near or above octane. any one of them can be used as is one a 1 for 1 basis to petrol in unmodified engines. All the higher alcohols are already approved as oxy additives and some like propanol are mixed in RFG presently at industrial levels the consumer is not notified due to their 100% miscability to petrol the DoE doesn’t require them to disclose the over 200 actual chemicals in retail petrol.
The whole point of butanol is that ultimately it can be made from nonfood stocks. as a second generation biofuel it can and should be made from cellulose, hemicellulose, and sugars hydrolysis from waste streams that contain cellulose or hemi, taken as a group cellulose and hemicellulose make up 2/3 or more of plant matter...
ALL plant matter not just the food part. think corn stalks, straw, sugar cane stalks,trees,bark,leaves,roots,hydrilla(weed that grows more than a food per day chocking American waterways),duckweed(fastest growing multicell plant on earth loves sewage water),scrap paper,scrap wood,municipal solid waste, sewage sludge,hemp,fast growing grasses on none irrigated land,mesquite trees that are a plague in the southwest growing like weeds on salty soil that even without human help if cut down will regrow 100% in 12 yrs or less, paddle cactus being one of the most efficient plant biomass makers on land, agave being the most efficient on land high yield on none irrigated scrub lands are producing 50+ tons a year of biomass per acre.can thrive on 250mm rain and even less.
The point is there is massive amounts of biomass to be had once you can use all of it not just the kernals of a corn plant. butanol is designed from the very get go to be a cellulitic biofuel the original process of ABE fermentation can eat any biomass cheap natural gas keeps that process from being used for organic solvent production not lack of technology its 1930s tech. biomass at 50$ a ton dry weight is equal to $25 oil on an energy basis btw. waste biomass can be had for tipping fees in some regions of the world that means negative costs per ton as someone is paying you to take the waste.
One of my graduate research projects was none food none irrigated biomass in the southwest USA on arid, marginal lands at 50 bucks a ton dry delivered mass new mexico could export energy even after fueling every car in its borders the problem is not availability of resources it’s turning all that biomass into something that the existing infrastructure can use at a cost that is competitive to oil. At $4 a gallon things get interesting at 2 nothing beats oil. The damn Saudis will run out of capital eventually and when they do oil will shoot back up to where the market needs to be for shale oil and deep water to be profitable 80ish a barrel
That’s all well and good, but this article is specifically about converting ethanol to butanol. Saying that you can re-run the ethanol through the process until you convert it all does not indicate the efficiency rate of this improved process.
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