CATALYSIS-A
DEMONSTRATION
LEROY D. JOHNSON Storer College, Harper's Ferry, West Virginia
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N THE October 1934 issue of the JOURNAL OR CHEMICAL EDUCATION^ a successful method of demonstration of the use of catalysts industrially was reported by Haut. With a modification of Haut's apparatus as described and as illustrated herewith, and with a few changes in procedure, it has been possible to show the catalytic oxidation of methyl alcohol to formaldehyde using copper oxide as catalyst. The essential reaction for this oxidation may be written:
About 50 cc. of methyl alcohol was placed in aroundbottomed flask fitted with an outlet tube. A 50-cc. distilling flask containing a thermometer inserted in a one-hole stopper can also be used. This flask was connected to the Pyrex tube where the oxidation took place by means of a piece of rubber tubing attached to a piece of glass tubing inserted into one hole of a two-hole rubber stopper which fitted the Pyrex tube. The flask containing the methyl alcohol was placed in an ordinary copper water bath, and during the course of the experiment a thermometer was inserted in the bath to assure that the temperature did not rise above
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Ham, J. CHEM.EDWC., 11, 575 (1934).
60°, for any temperature above this gave too rapid evaporation and consequent condensation of the methyl alcohol, increasing the danger of explosion. The oxygen for this experiment was generated by the usual laboratory method of heating a mixture of potassium chlorate and manganese dioxide, and was purified by bubbling the gas through a bottle of concentrated sulfuric acid. The acid wash bottle was very helpful in serving as a means of controlling the speed a t which the oxygen was delivered. The purification tube was connected to the Pyrex tube by means of a piece of rubber tubing, which in turn was attached to a piece of glass tubing inserted in the other hole of the two-hole stopper fitting the Pyrex tube. The Pyrex tube, about 1.5 to 2 inches in diameter, and about 12 inches long, was filled with Baker's copper gauze and was heated by means of a burner of the Meker type to give copper oxide. Into one end of this tube was inserted a two-hole stopper carrying the tubes leading from the vaporized methyl alcohol and the oxygen. To the other end of the tube there was attached a piece of glass tubing about one-half inch in diameter and two feet long. The outlet end of this half-inch tubing led into an Erlenmeyer flask, the bottom of which was covered by a few milliliters of distilled water. The apparatus assembled appeared as in the accompanying diagram. After the apparatus was assembled, and it was made
sure that all stoppers were fitted tightly, the copper In conclusion i t may be stated that this demonstragauze was heated to redness, and the methyl alcohol tion: was vaporized by a Bunsen burner under the water (1) illustrates the industrial application of a simple bath, care being taken that the temperature of the bath organic reaction; did not exceed 60°,and that no condensation took place (2) shows the r61e of catalysts and their importance; as the vapors entered the tube. (3) presents a sensible testing program for the general It is advisable to cover the Pyrex tube with wire gauze to prevent glass from striking students or operator should an explosion occur. The oxygen was next generated slowly, and the speed of evolution was noticed by watching the bubbling of acid in the wash bottle. As the methyl alcohol and oxygen passed over the heated copper (copper oxide) the reactiou took place and the odor of formaldehyde was detected in the Erlenmeyer flask. The reaction was permitted to continue until the oxygen charge was used up; a portion of the solution in the Erlenmeyer flask was then transferred to a clean test-tube and treated with an ammoniacal solution of student, i. e. (a) odor test, (b) visual test of silver mirror; (4) when employed with Haut method for oxidizing silver nitrate. Heating of the mixture and subsequent cooling resulted in the formation of a silver mirror on ammonia, affords a means of comparing reactions using the sides of the test-tube--a c o n h a t o r y test for the same catalyst; (5) requires simple apparatus and a brief time period. aldehyde.
