| Acetylene, Acetone, Acetic Acid Dave Dietzer Acetylene for oxyacetylene welding and cutting can be obtained by reacting calcium carbide with water. CaC2 + 2H2O ==> C2H2 + Ca(OH)2 The acetylene, C2H2, evaporates and the calcium hydroxide, slaked lime, remains. From: http://en.wikipedia.org/wiki/Calcium_carbide "Calcium carbide is produced industrially in an electric arc furnace loaded with a mixture of lime and coke at approximately 2000 °C. This method has not changed since its invention in 1888: CaO + 3C ==> CaC2 + CO The high temperature required for this reaction is not practically achievable by traditional combustion, so the reaction is performed in an electric arc furnace with graphite electrodes" Acetylene cannot be compressed over 15 psi or it will explode. Acetylene tanks contain a porous material and acetone. The acetylene dissolves in the acetone. From: http://en.wikipedia.org/wiki/Acetone One liter of acetone can dissolve around 250 liters of acetylene From: http://www.taylor-wharton.com/Pages/HP&A/Acetylene.htm The inner porous mass in every Taylor-Wharton Millennium acetylene cylinder is an environmentally-friendly formula of calcium-silicate, delivering a porosity of 88-92% - the highest allowed by U.S. and Canadian regulations Calcium silicate could be made on the Moon probably by simply roasting CaO with SiO2 at the right temps are proportions. Now we need acetone. From: http://chestofbooks.com/science/chemistry/Distillation-Principles-And-Processes/Chapter-XXIII-Production-Of-Acetone-By-Means-Other-Than-Fer.html "Calcium acetate when heated at a temperature of about 380° C. decomposes, giving acetone and a residue of calcium carbonate, but at the same time the accompanying calcium salts present as impurities also react and acetaldehyde and various higher ketones are formed together with the condensation products. In addition other impurities (such as dumasin) and tar-like bodies are formed" The acetone is then purified by condensing the tar and floating the off other impurities in water. Since the calcium acetate we make on the Moon should be rather pure compared to the stuff made from limestone on Earth, we might not have much trouble with other ketones forming. But how do we get calcium acetate? First we need syngas, a mixture of CO and H2. We will obtain this by volatiles scavenginging. Then we react this mixture: CO + 2H2 ==> ZnO/Cr2O3 catalyst ==> CH3OH methanol CO + CH3OH ==> at 200 C. and 50 atm. pressure ==> CH3COOH acetic acid From: http://www.newworldencyclopedia.org/entry/Acetic_acid "Acetic acid is corrosive to many metals including iron, magnesium, and zinc, forming hydrogen gas and metal salts called acetates" Pure calcium metal is reacted with acetic acid. Ca(s) + 2 CH3COOH(aq) ==> (CH3COO)2Ca(aq) + H2(g) The calcium acetate (CH3COO)2Ca is then distilled as described above. (CH3COO)2Ca ==> CH3COCH3 (acetone) + CaCO3 Acetic acid has other uses. It's commonly known as vinegar and when diluted with water it makes and cleaning fluid. Windex is basically just vinegar water. Acetic acid can also be used to make plastics. From: http://www.newworldencyclopedia.org/entry/Acetic_acid. "The major use of acetic acid is for the production of vinyl acetate monomer (VAM). This application consumes approximately 40 to 45 percent of the world's production of acetic acid. The reaction is of ethylene and acetic acid with oxygen over a palladium catalyst. 2 H3C-COOH + 2 C2H4 + O2 ==> 2 H3C-CO-O-CH=CH2 + 2 H2O Vinyl acetate can be polymerised to polyvinyl acetate or to other polymers, which are applied in paints and adhesives." Ethylene can be made on the Moon according to the reaction: 2CO + 4H2 ==> Fe cat. ==> C2H4 (ethylene) + 2H2O We will need equipment to do all this, basically tubes and containers, valves and compressors, electric furnaces, etc. Poylmerizing vinyl acetate will require a reflux condensor. And we will need catalysts. We won't be making huge tonnages of polyethylene from ethylene or polyvinyl acetate given the supply of carbon and hydrogen, but we will be capable of making necessary amounts of these substances in pounds probably, not tons, although volatiles mining could eventually allow some small tonnages of plastics making. We will need a substantial qty. of acetylene and acetone, and the H2O and CO2 formed when C2H2 burns in a welding or cutting torch will be recovered from the air and the H2O will be electrolyzed to hydrogen and oxygen and the CO2 converted to carbon monoxide and oxygen to make syn-gas. Acetone is made today by the cumene process that combines benzene and propylene to make acetone and phenol. See: http://en.wikipedia.org/wiki/Cumene_process Propylene is made: 6CO + 3H2 ==> C3H6 + 3CO2 I don’t know how benzene would be made from synthesis gas or from methane , but a good organic chemist could figure it out. Phenol is used to make other synthetic materials and propylene can be polymerized to polypropylene. Whether the modern Cumene process or the old dry distillation of metal acetates will be more expedient on the Moon with limited resources available I cannot predict. SEE: Basic Chemistry for Moon Miners and Lunar Calcium |
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