I
W. E. CROMWELL The Welsbach Corp., Philadelphia, Pa.
How to Predict
Flammability in Ozonization Reactions Water required to prevent spark-induced flame and explosion is small compared to amount needed for evaporative cooling. Temperature control is necessary in some anhydrous reactions, i f flame is to be avoided I N MAxUFACTURiNG COhiPOUNDS using ozone, sparks, or other high temperature energy sources-e.g., hot spotshave caused flames or explosions. I t was theorized that the presence of water might prevent or minimize these hazards, but the literature indicates that for optimum yields, water should be avoided (7). Yet regardless of the theories concerning the presence of water, a simple test is suggested to establish yields (2) where unsaturated fatty acids were ozonized without adverse effect, even though enough water was used to provide evaporative cooling. I n the work described here, simple tests are devised for determining safe temperature limits for all plant-scale ozonization reactions. Neither commercially used mixtures of ozone, up to 9% by weight, in oxygen, nor the presence of ozonized products alters flammability limits. Water will markedly reduce the hazard of flame and explosion in the ozonization of fatty acids.
Experimental
This study concerns the capability of a gaseous mixture to propagate flame. I t is known that the means of ignition can affect flammability limits. An effort was made to ensure that variations in the energy level of the spalk initiator did not affect the results obtained. A circuit breaker was used in the primary leads of the high voltage transformer. Manually closing this switch produced a spark across the gap. The duration of the spark was a function of the current load limit of the circuit breaker. T h e compound to be tested was plhced in a test tube reactor and 2% ozone in oxygen was bubbled through the mixture. The temperature of the reactants was controlled by a bath surrounding the test tube. T h e temperature within the
As little as 1%
water in the reactants will markedly reduce the hazard of flame and explosion in the ozonization of fatty acids. Simple tests are described for determining the safe limits of temperature for all plant scale ozonization reactions. Commercially used ozone concentrations up to 9% by weight in oxygen do not affect flame and explosions caused by sparks. The presence of ozonide products does not alter the flammability limits.
the top of the test tube was merely placed lightly on top, instead of inside the tube. With this setup, the force of the flame front merely lifted the stopper without shattering the glass. I n each experiment, typical conditions expected in an ozonization reaction were provided. Several attempts were made to produce a flame by sparking. Duplicate runs were made. The results are given in the table in terms of what is safe.
Flammability Limits in the Ozonization of Some Olefins, Paraffins, and Fatty Acids Safe Maximuni TPnij,. Reactant
reaction vessel was measured by a copperconstantan thermocouple connected to a recording potentiometer. The figure of 120" C. represents the temperature limit of experimentation only in the case of 1dodecene. The desired concentration of water was premixed with the reactants and allowed to come to a specified temperature in the bath before the ozone-oxygen application was started. I n this way, undue loss of water by evaporation was prevented. A suitable organic solvent was used for some of the unsaturated materials to ensure complete miscibility with the amounts of water required. No solvent was used with I-octene, 1-dodecene, and n-hexane. Acetic acid was used with a-methylstyrene, a-pinene, and maleic acid. Pelargonic acid was used with oleic and linoleic acids. Normal precautions were taken in the use of shields and barriers. It was found that destructive shattering could be reduced to a minimum if the stopper at
1-Octene 1-Dodecene n-Hexane a-Methylstyrene a-Pinene Maleic acid Oleic acid Linoleic acid Acetic acid Caproic acid Pelarogonic acid
O C .____ rlnhydrous V i t h water
