1,3-Butadiene → Isoprene butadiene

Participants

Reaction Steps

Part of the polymeric solution (195 g) described in Example V was introduced into a 0.5 L Fischer-Porter reactor. The total amount of polymer added to the reactor was 31.4 g which represents 0.540 moles of butadiene unsaturation. The hydrogenation catalyst was prepared by adding 35.1 mL of a 1.7M triethylaluminum solution (59.6 mmol) to a solution of 19.9 mmol of cobalt octoate in 153.0 mL (119.2 g) of cyclohexane. The final catalyst solution was 0.1M in cobalt and had an aluminum-cobalt ratio of 3:1. A portion of this catalyst (5.0 mL, 0.50 mmol Co) was syringed into the reactor which had been purged/vented three times with nitrogen, then hydrogen, and pressured to 55 psig with hydrogen. The reaction exothermed to 34° C. and was maintained at 30°-35° C. The progress of the hydrogenation was monitored by infrared (FTIR) analysis of hourly samples. After 4 hours an additional 4 mL (0.40 mmol) of catalyst was added. The reaction was terminated after 6.25 h, when the IR showed minimal trans unsaturation (968 cm-1) and complete disappearance of vinyl (910, 990 cm-1). The catalyst was then removed by washing the polymer in the same type of reactor described in Example I with 300 mL of a 0.5M citric acid aqueous isopropanol (2:1 water-IPA) solution. The mixture was vigorously mixed at 70° C. for 20 minutes and allowed to settle. The pink aqueous layer was removed and the entire wash step was repeated using an aqueous isopropanol (2:1 water-IPA) solution. After addition of 0.2 g of Irganox 1076, the polymer was isolated by removing the volatiles under reduced pressure. Gel permeation chromatography of a sample revealed little change in the polydispersity index of the polymer had occurred as a result of hydrogenation.

Provenance & Evidence