Vinyl acetate vapor measurement

Selective Measurement of Vinyl Acetate Vapor Using a Coated Surface Acoustic Wave Oscillator... 

A coated surface-acoustic-wave (SAW) sensor capable of real-time, selective measurement of vinyl acetate vapor in the presence of several olefin and non-olefin cocontaminants is described. The coating film en loyed consists of the solid platinum-ethylene Ji-complex, trans-PtCl (ethylene)(pyridine). occluded in a polyisobutylene matrix. Exposure to vinyl acetate results in displacement of ethylene from the cott lex and formation of the vinyl acetate-substituted complex. Subsequent regeneration of the original reagent is possible by treatment with ethylene gas, in situ. A lower detection limit of 5 ppm of vinyl acetate is achieved for operation at 46 C. The industrial-hygiene applications of the sensor are discussed. 

The vapor pressures have been measured up to ihe boiling point on all four compounds, and up to the critical point for methyl and ethyl acetate.The method of Miller was used to estimate the vapor pressure above the boiling point for butyl und vinyl acetate. 

Nakajima, A. Yamakawa, H. Sakurada, I., "Vapor Pressures of Polymer Solutions. I. Apparatus for Measurement and Some Results on Poly(vinyl acetate) Solutions," J. Polym. Sci., 35, 489 (1959). 

WAN Wang, N.H., Hattori, K., Takashima, S., and Masuoka, H., Measurement and prediction of vapor-hquid equihbrium solutes at infinite dilution in carbon dioxide + poly(vinyl acetate) system at high pressmes, 17, 1138, 1991. 

Reference [2] also indicates that the most economic route to vinyl acetate, when acetic acid is available, is to convert the raw materials to product in the vapor phase over a palladium catalyst. We therefore asked our research chemists to develop a catalyst suitable for the operation. They found a suitable catalyst by impregnating a silica base with 2% palladium along with some other proprietary chemicals. The chemists performed numerous experiments with the catalyst and found that it is quite selective towards vinyl acetate and quite active as measured in its space time yield (STY, grams of vinyl acetate/hr per liter of catalyst). The only significant side reaction we could notice is the combustion of ethylene to carbon dioxide and water... 

Kato, M. Vapor-liquid equilibrium measurements for binary systems of acetic add with ethyl acetate and vinyl acetate by the dew-bubble point temperature method J. Chem. Eng. Data 1988,33, 499-501... 

The selectivity of the sensor was tested by simultaneous exposure to VA and each of several other gases and vapors encountered with VA in industrial processes. The chemicals examined included ethyl acetate, methanol, methyl acrylate, methylmethacrylate, mesityl oxide and vinyl chloride. Table I summarizes the results for exposures at 40 C to 50 ppm of VA and each of the other chemicals. As shown, there was no measurable effect on the response to VA. With the exception of methyl acrylate, none of these confounds reacted with the conplex when exposed Individually. The response to 60 ppm of methyl acrylate alone was 10 Hz/mln which is about one-third that of VA at the same concentration. That methyl acrylate does not affect the response to VA during simultaneous exposure is remarkable since it indicates that the VA is exclusively favored in the con etition for reaction with the solid. This observation, coupled with the fact that the strongly-coordinating methanol does not increase the response to VA, is consistent with previous data (22) indicating an associative pathway for the reaction. 

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