Purification of Caffeine

100 g of crude industrial caffeine containing 84.8 g caffeine were dissolved in1 liter of an aqueous solution containing 6 ml of a 30% solution of sodium hydroxide and having a pH of 9 and a temperature of 70.degree. C. To this solution were added 10 g of active charcoal, 5 g of sodium dithionite and 4 g of celite. Nitrogen was bubbled through and after mixing, the solution was filtered to remove the active charcoal celite and impurities.

The filtrate was then cooled to 20.degree. C. to recrystallise some of the caffeine. The crystals were filtered off and washed with 200 ml of washing water. The mother-liquor, which was an aqueous alkaline solution containing the remainder of the caffeine, together with the washing water, were extracted with 2 liters of dichloromethane at 40.degree. C. in a countercurrent manner. The dichloromethane phase containing most of the caffeine was separated from the impure exhausted aqueous alkaline phase and the dichloromethane was evaporated off to yield a further quantity of caffeine, which together with the previously recrystallised caffeine weighed 55 g. This caffeine was added to a mixture of 500 g of fresh water and 1 g of sodium dithionite at 70.degree. C. and the pH was adjusted to 9 by further addition of 1.2 ml of 30% sodium hydroxide. Nitrogen was bubbled through and after mixing, the temperature was reduced to 20.degree. C. to recrystallise some more of the caffeine. The crystals were filtered off, washed with 200 ml of fresh washing water and dried to give 30 g of pure caffeine. The mother-liquor, which was an aqueous alkaline solution containing the remainder of the caffeine, together with the washing water, were recirculated and extracted at 40.degree. C. with the dichloromethane which had been evaporated off after the first extraction. The dichloromethane phase containing most of the caffeine was separated from the impure aqueous alkaline phase and the dichloromethane was evaporated off and the caffeine recrystallised again as before. This recirculation of the mother-liquor and dichloromethane, and the recrystallisation of the caffeine followed by drying were repeated until the yield of pure caffeine was 95%.

100 g of crude industrial caffeine containing 84.8 g caffeine were dissolved in 500 g of an aqueous solution containing 6 ml of a 30% solution of sodium hydroxide and having a pH of 9 and a temperature of 70.degree. C. To this solution were added 10 g of active charcoal, 1 g of powdered zinc and 4 g of celite. Nitrogen was bubbled through and after mixing, the solution was filtered to remove the active charcoal, celite and impurities.

The filtrate was then cooled to 20.degree. C. to recrystallise some of the caffeine. The crystals were filtered off and washed with 300 ml of washing water. The mother-liquor, which was an aqueous alkaline solution containing the remainder of the caffeine, together with the washing water, were extracted with 1 liter of dichloromethane at 40.degree. C. in a countercurrent manner. The dichloromethane phase containing most of the caffeine was separated from the impure exhausted aqueous alkaline phase and the dichloromethane was evaporated off to yield a further quantity of caffeine which together with the previously recrystallised caffeine weighed 44 g. This caffeine was added to a mixture of 850 g of fresh water and 0.4 g of powdered zinc at 70.degree. C. and the pH was adjusted to 9 by the further addition of 0.8 g of 30% sodium hydroxide. Nitrogen was bubbled through and after mixing, the temperature was reduced to 20.degree. C. to recrystallise some more of the caffeine. The crystals were filtered off, washed with 300 ml of fresh washing water and dried to give 41 g of pure caffeine. The mother-liquor, which was an aqueous alkaline solution containing the remainder of the caffeine, together with the washing water, were recirculated and extracted at 40.degree. C. with the dichloromethane which had been evaporated off after the first extraction. The dichloromethane phase containing most of the caffeine was separated from the impure aqueous alkaline phase and the dichloromethane was evaporated off and the caffeine recrystallised again as before. This recirculation of the mother-liquor and dichloromethane, and the recrystallisation of the caffeine followed by drying were repeated until the yield of pure caffeine was 95%.

100 grams of crude industrial caffeine containing 84.8 g caffeine were dissolved in 1 liter of an aqueous solution containing 6 ml of a 30% solution of sodium hydroxide and mixed at 40.degree. C. before filtering to remove the pellicules. The aqueous phase was then extracted with 2 liters of dichloromethane at 40.degree. C. in a countercurrent manner up to exhaustion of the caffeine. The dichloromethane phase containing most of the caffeine was separated from the impure aqueous alkaline phase and the dichloromethane was evaporated off leaving 74 g of caffeine. This caffeine was then redissolved in 1100 g of fresh water at 70.degree. C. and 0.4 g of a 30% solution of sodium hydroxide was added to bring the pH to 9.5. 10 g of activated charcoal, 0.4 g of zinc powder and 4 g of celite were then added and nitrogen was bubbled through. After mixing the solution was filtered to remove the zinc, activated charcoal, celite and impurities. The filtrate was then cooled to 20.degree. C. to recrystallise some of the caffeine. the crystals were filtered off, cleaned with 300 ml of fresh washing water and dried to give 46 g of pure caffeine. The mother-liquor which was an aqueous alkaline solution containing the remainder of the caffeine was recirculated and extracted at 40.degree. C. with the dichloromethane which had been evaporated off after the first extraction. The dichloromethane phase containing most of the caffeine which was present in the mother-liquor was separated from the impure aqueous alkaline phase and the dichloromethane was evaporated off and the caffeine recrystallised again as before. This recirculation of the mother-liquor and dichloromethane, and the recrystallisation of the caffeine followed by drying were repeated until the yield of pure caffeine was 95%. The mother-liquor and the washing water can be used to dissolve a fresh charge of crude caffeine and the process repeated.