Boiling point of BF3 is determined by the interaction of BF3 and the promoter. Promoter is a chemical agent that causes BF3 to act as an oligomerization catalyst. Generally, a promoter has a boiling point below that of BF3’2H20. Some examples are ketones, alcohols, and fatty acids.
An oligomer is made by charging a quantity of BF3 to a reaction vessel and then stirring for a certain number of hours under a specified pressure. The oligomer is then water washed to extract BF3 as a hydrate.
As a result, an aqueous solution of BF3 hydrate is accumulated in a reboiler. This is then recovered by mixing the residual liquid with sulfur trioxide. Alternatively, it can be used for disposal or recycling.
The amount of BF3 in the reaction mixture can be increased by continuously bubbling BF3 through the reaction mixture. However, an aqueous soluble promoter has to be used. A useful range for the amount of a polar compound is 0.1 to 2.0 weight percent of -olefin.
The amount of water to use for the first wash is four to ten parts per hundred parts of oligomer. In subsequent water washes, the amount can be much higher. After the separation, a second wash is added. This will be analyzed for fluoride and n-butanol.
A useful pressure range is from five to fifty psig. The residual product has at least 50 weight percent BF3 in the form of BF3’2H20. Depending on the type of residual product, it can be recovered by conventional means.