Alkali wood extraction
Jump to navigation
Jump to search
Alkali wood extraction is a method of producing oxalic acid, formic acid and methanol from sawdust or wood chips by dry-distilling them in the presence of a strong alkali (usually sodium or potassium hydroxide), then treating the "melt" of wood with acid to produce a soluble alkaline oxalate.[1]
- Combine a concentrated solution of potassium hydroxide or sodium hydroxide with sawdust in a metal (iron) pan
- Mix thoroughly over heat
- Evaporate to dryness by heating to 110°C
- Raise temperature to the range 180-240°C for 20-40 minutes
- Leach with water
- Boil until density approaches 1.355 g/cm
- Allow to cool
- Filter
- Discard filtrate (toxic)
- Redissolve residue in hot water
- Add calcium hydroxide
- Ca(OH)2 + Na2C2O4 → CaC2O4(s) + 2 NaOH(aq)
- Filter
- Evaporate filtrate (hydroxides) and recycle
- Add water to the residue to create a slurry
- Add sulfuric acid to the slurry
- Heat gently and stir for 2h
- CaC2O4 + H2SO4 → H2C2O4(aq) + CaSO4(s)
- Filter.
- Residue is calcium sulfate
- Evaporate to density of 1.116
- Filter
- Residue is calcium sulfate
- Dry filtrate
- Powder is oxalic acid
References
- ↑ Othmer, Donald F.; Gamer, Carl H.; Jacobs, Joseph J. (1942) "Oxalic Acid from Sawdust - Optimum Conditions for Manufacture"
Ind. Eng. Chem. 34(3); pp262–267.
link courtesy ACS.