This post relates to using activated charcoal to separate nitrogen and oxygen from air. Oxygen heavy air is useful for pyrolysis and combustion operations. Nitrogen is useful for pyrolysis (as an inert gas) or producing nitric acid, ammonia nitrate, etc.
In his collected papers, Sir James DeWar explores the absorbent capacity of activated charcoal at the temperature of liquid air (-120C?). When cooled to low temperatures, 50g of coconut charcoal absorbed 6 L of room air. When raised back up to room temp, the charcoal released the same volume, but first releasing very nitrogen rich air, and finishing very oxygen rich. Or maybe it was oxygen first…
This absorbance and selectivity is now understood (and was by DeWar also) to be a property of molecular sieves, which are very porous materials with hundreds of square meters of surface area per gram, and pore spaces the size of molecules.
6 liters of air from 50 g of charcoal is alot. According to DeWar, thats 1 L of 80% pure oxygen. The less pure fractions could be recycled, so doing more runs in a row would give maybe 2 or 3 L of enriched air per cycle. How much air is desorbed selectively between temperatures easily achievable (evaporative chilling and solar cookers or flue gasses)? What about using more selective silica/alumina molecular sieves?
Using enriched air in a wood gasifier would likely decrease the nitrogen concentration to the point that methanol catalysis becomes possible. Also, the reaction zone would be hotter, or the combustion zone of any furnace type thing.
edit: upon further research into methanol catalysis, I believe that actually catalyzing methanol from hydrogen and carbon monoxide is not attainable with simple technology (required pressures, tempertures and plumbing complexity are too great). Methanol from wood gas comes from higher hydrocarbons that are oxidized, and makes up only 1% of the gas. Optimizing combustion for increasing methanol from this chemical route would be more achievable, and is a subset of the technology of making pyrolysis oil.