Niacet Plant

Aerial View of the Niacet Plant.
Notice on the left is Electrometallurgical’s property. The piles of ore are for smelting.

One of the principle products which was manufactured from acetylene was vinyl acetate. This was manufactured by an appropriately named company Niacet (an acronym for Niagara Acetylene). Niacet was a division of the giant Union Carbide and Carbon Chemicals Corporation. The technology was explained to me during the course of a science congress project. It involved the reaction of acetylene gas counter current to a flow of acetic acid mixed with sulfuric acid catalyzed by mercuric acetate. The by-product was acetaldehyde which you could small a block away on Buffalo Ave.

Vinyl acetate was polymerized, by emulsion polymerization to polyvinyl acetate and then reacted with butyraldehyde to polyvinyl butyral which was the layer in laminated safety glass to prevent glass from shattering. There were many other projects at this plant such as Tergitol surfactants, meta-aminoacetophenone (pharmaceutical), sodium acetate anhydrous, Sodium phenoxyacetate is a precursor for semi-synthetic penicillin’s.

The impetus was to develop acetylene chemistry. Niacet's early production of acetic acid was from acetylene which they received, via pipeline, from Electrometallurgical Division UCC "over the fence."

The formation of acetic acid was accomplished by catalytic liquid phase oxidation of acetaldehyde with oxygen, using air as the source of oxygen (20-21% O2).

Undoubtedly, nitrogen took place in the presence of catalytic amounts of manganese acetate which is soluble in acetic acid and takes place at atmospheric pressure.

There is a much more complex mechanism than just the general equation as demonstrated many years later during UCC's work on anhydrous peracetic acid chemistry.

The more dynamic phase of this story is found in a subsequent publication on peracetic acid from Union Carbide Chemicals where in the opening paragraphs (reference J. Am. Chem. Soc 79, 5982-5986 (1957)) showed the mechanism through an unstable peroxide which is decomposed by manganese ions into acetic acid in the absence of water.

Appartus for batch, liquid-phase oxidation
of acetaldehyde to acetic acid.

The equipment consists of an aluminum-lined steel reaction vessel capable of holding 4,000 to 5,000 kilograms (about 8,000 - 10,000 pounds) of acetaldehyde and fitted with an air sparger aluminum coils for heating and cooling, inlet and outlet openings. 99-99.8% acetaldehyde previously cooled to 0-5°C is introduced followed by 18-22 kg of manganese acetate added in a solution of acetic acid. Air is then admitted through the sparger and steam introduced into the coils to raise the mixture to reaction temperature. When the reaction starts, absorption of air begins and the heat of reaction must be removed by cooling water. The temperature is controlled after an hour - 27°C is ideal. After 2 hours, 28-30°C is ideal and 60°C after four hours as acetic acid forms. Reaction is complete in 12-14 hours. The pressure is not allowed to go above 65.3 psi. Nitrogen is vented through a series of condensers attached to the top of the kettle. The acetaldehyde, at reflux, is carried over as vapor is condensed and returned to the kettle. Nitrogen is finally scrubbed to remove acetaldehyde before being returned back to the kettle. The final acetic acid is 96%, yield 88-95% of theoretical and is then set to distillation to 99.5%. The plant operated at 80-100 tons per month.

Production of Acetaldehyde

Acetaldehyde was manufactured by the reaction of acetylene in theory with water but practically by the action of warm dilute sulfuric acid catalyzed by small amounts of mercuric sulfate (added as mercuric oxide). By passing acetylene through acid resistant towers containing warm dilute sulfuric acid with mercury catalyst, acetylene was converted continuously to acetaldehyde. Condensing the hot vapors with cold heat exchangers, acetaldehyde vapor could be easily recovered (boiling point 22°C). For additional information, the reader is referred to the following: The Chemistry of Acetylene, J. Nieuwland & R. Vogt, American Chemical Society Monograph Series, 1945 pp. 115-119 (and references therein).