Acetylene oxidation—continued

Compounds with triple bonds, i.e. acetylenic compounds, continue to receive attention. Patents have been filed for mixtures of propargyl alcohol with, for example, cellosolve + a phenol formaldehyde resin + tar bases heterocyclic nitrogen compounds + acetylenic + dialkylthiourea or a quaternary + antimony oxide . 

Limits of Detection for the Nitrous Oxide-Acetylene Flame (continued)... 

Polished steel substrates primed with plasma polymerized acetylene films were immersed into a stirred mixture of these materials at a temperature of 155 5°C to simulate the curing of rubber against a primed steel substrate. During the reaction, the mixture was continuously purged with nitrogen to reduce oxidation. At appropriate times between 1 and 100 min, substrates were removed from the mixture, rinsed with hexane ultrasonically for 5 min to remove materials that had not reacted, dried, and examined using RAIR. The RAIR spectra obtained after reaction times of 0, 15, 30, and 45 min are shown in Fig. 13. 

Some acrylates are still produced by a modified Reppe process that involves the reaction of acetylene, the appropriate alcohol (in the case of butyl acrylate, butyl alcohol is used), and carbon monoxide in the presence of an acid. The process is continuous and a small amount of acrylates is made this way. The most economical method of acrylate production is that of the direct oxidation of propylene to acrylic acid, followed by esterification. 

Catalysts used to convert ethylene to vinyl acetate are closely related to those used to produce acetaldehyde from ethylene. Acetaldehyde was first produced industrially by the hydration of acetylene, but novel catalytic systems developed cooperatively by Farbwerke Hoechst and Wacker-Chemie have been used successfully to oxidize ethylene to acetaldehyde, and this process is now well established (7). However, since the largest use for acetaldehyde is as an intermediate in the production of acetic acid, the recent announcement of new processes for producing acetic acid from methanol and carbon monoxide leads one to speculate as to whether ethylene will continue to be the preferred raw material for acetaldehyde (and acetic acid). 

Flame Atomic Absorption Spectroscopy FAAS is one of the oldest analytical techniques and continues to be used in the analysis of food products. The analysis is usually performed in an air-acetylene or a nitrous oxide-acetylene flame. The technique measures the absorbance of electromagnetic radiation by the free atoms produced at high temperamre (1000-4000 K) [6]. 

The composition and temperature profiles in low-pressure fuel-rich flames of ethylene oxide have been studied by Bradley et al. [65]. The major products were carbon monoxide, hydrogen, ethylene, methane, acetylene, butadiene and vinylacetylene, with traces of propene and propane. The unsaturated products were formed marginally later than the others, and ethane showed a maximum which coincided with the almost complete removal of fuel and oxygen. Acetylene and vinylacetylene continued to increase above the flame, although other products remained constant. 

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