JOURNAL OF CHEMICAL EDUCATION
220
MAKING WATER GAS BY CRACKING METHANOL WILLIAM K. VIERTEL State University of New York, Agricultural & Technical Institute, Canton, New York
COI CYLINDER
,
METHANOL 'OILER
SILICA TUBE IN ELECTRIC FURNACE
SAFETY WASH BOTTLE BOTTLE
%WAY STOPCOCK
GAS HOLDER
Applvatve for Mahi.ing Watar Gas hy Cracking Methanol
ITIS perhaps not generally known 'that methanol vapor decomposes very readily at about 1000°C., without the use of & catalyst, into carbon monoxide and hydrogen. The process is simple enough~tohe done by students with only ordinary supervision, and requires no special equipment. The operation has been part of our laboratory work in industrial chemistry for several years, and serves a double purpose-to illust,rate the industrially important "cracking" operation, and to make water gas for practice analyses with a gas analyzer. We use a carbon combustion furnace, complete with its fused-silica tube. We put in this tube, at, the hottest part, about three inches of some refractory material, in granular form, held in place by two pieces of nichrome screen wedged in. The methanol boiler is a conical flask,with both inlet and outlet tubes, heated by an electric hot plate. The outlet tube of the boiler is connected to. the inlet end of the silica tube. At the outlet of the silica tube, there is a safety bottle, followed by a water-scmbbing bottle to remove any undecomposed methanol. Then comes a two-way stopcock, one arm of which is connected to a miniature gas holder of about one gallon capacity. The other arm is vented outdoors through a long tube going out of a window. Formation of explosive mixtures is avoided by flush-
ing out the air with carbon dioxide or nitrogen from a cylinder, when starting up, and flushing out the water gas with the same inert gas in shutting down. This is the reason for the inlet tube on the methanol boiler. After the silica tube is up to temperature, the air is flushed out, and the methanol started boiling. The first product gas, being contaminated with inert gas, is allowed to escape outdoors. When it is believed that the inert gas has all been swept out, a holderful is collected. The gas is then vented again, and the inert gas turned on again as the heat is turned off under the boiler. Soon after the methanol stops boiling, the flushing is stopped and the apparatus can be dismantled. There is perhaps a remote risk of carbon monoxide poisoning. Our students are warned of the symptoms and treatment; but after using the process for three years, no trouble has been encountered. The product runs very close to the calculated composition-two-thirds hydrogen, one-third carbon monoxide, with a few tenths of a per cent of methane. The only item of equipment that would not ordinarily be found in a reasonably well-equipped laboratory is the miniature gas holder. The author does not know whether these are obtainable; ours was built in our sheet-metal shop to the author's design.
