A process according to claim 4 further comprising repeating the steps at least one more time with the recrystallized and the extracted caffeine for further purifying the caffeine. Dry the washed product: Final drying for a small amount of crystallized product can be done by squeezing the crystals between sheets of filter paper and allowing them to dry on a watch glass; alternatively, you can place them in a round-bottomed flask, and leave them on a vacuum line for about an hour. A process for purifying caffeine having impurities which comprises the steps of: a preparing an aqueous solution of caffeine having impurities, wherein the solution has a pH of at least 6. In this Instructable I'll be using Maximum Strength NoDoz. During the heating process, it was ensured that the hotplate was set to low heat because the boiling point of dichloromethane is only 40ºC and the hood of the fume chamber was closed because dichloromethane is very volatile. This caffeine was added to a mixture of 500 g of fresh water and 1 g of sodium dithionite at 70° C.
Having that been said, lets start with the parts list. The pH of the aqueous alkaline solution of the caffeine is conveniently at least 6. Nitrogen was bubbled through and after mixing, the solution was filtered to remove the active charcoal, celite and impurities. Add the solvent drop by drop. Once crystallization has begun, take care not to disturb the container to allow formation of large crystals.
The liquid was stirred with a glass rod and dehydrated. Remove the charcoal with adsorbed impurities by filtration, as described in the next step. The washings were also transferred into the separatory funnel. A more skilled hand would do a bit better, but it's not really that bad and it certainly is an easy way to do it. The aqueous phase was then extracted with 2 liters of dichloromethane at 40° C. The solvent will evaporate leaving a layer of caffeine crystals. The most suitable solvents are halogenated hydrocarbons, preferably chlorinated hydrocarbons, for example, dichloromethane.
In the third week, the crude caffeine was purified by recrystallization and the caffeine crystals were collected. It was then cooled in an ice bath for a further 3 minutes to promote crystallization. This was placed on a hotplate and heated gently. If the caffeine is extracted before the recrystallisation, it is preferably extracted from an aqueous alkaline solution of caffeine in the absence of a reducing agent, after which the solvent phase containing the caffeine is separated from the aqueous phase, the solvent evaporated off and the caffeine dissolved in fresh aqueous alkaline solution containing a reducing agent and subsequently recrystallised. Add boiling solvent from the third Erlenmeyer flask to any crystals formed on the filter paper and to rinse the first Erlenmeyer flask that contained the solution being filtered, adding the rinse to the filter paper. Leave the vacuum on to dry the crystals at the end.
Use a few drops of ice-cold solvent to rinse the crystallization flask and pour that onto the funnel while reapplying vacuum, and break the vacuum as soon as all liquid is removed from the crystals. The crystals were filtered off, washed with 300 ml of fresh washing water and dried to give 41 g of pure caffeine. Simply pour off decant the hot solvent, leaving the insoluble solids behind. But if you insist on using both, I'd recrystallize first. Purification by recrystallisation from water has also been tried but the morphology of the crystals long needles forming inextricable masses caused the retention of impure mother-liquor and the chemical nature of the caffeine caused associations with the impurities, preventing the formation of a pure solid phase.
A process for the purification of caffeine which comprises carrying out the following steps in any order; a recrystallization of caffeine from an aqueous alkaline solution of caffeine containing a reducing agent and b extraction of the caffeine from an aqueous alkaline solution of caffeine with a substantially water-immiscible solvent which is liquid under the conditions of the process. Parts: A clean pane of glass. The recrystallized caffeine particles consistently exhibited acicular crystal habit. A process according to claim 6 wherein each aqueous solution is prepared with an alkali metal hydroxide. Nitrogen was bubbled through and after mixing, the temperature was reduced to 20° C. It is preferably inorganic and may be, for example, an alkali metal hydroxide such as sodium hydroxide or potassium hydroxide. The following Examples further illustrate the present invention.
It is best to add in just a little more solvent beyond saturation at the boiling point. Rinse the crystallization flask with ice-cold solvent, add this to the washed crystals, reapply vacuum, and break vacuum when the liquid is removed from the crystals. The effect of operating variables such as crystallizing temperature, solvent type, and the carbon dioxide injection rate on the solid-state properties of caffeine was investigated. The caffeine was extracted from the aqueous tea solution with three separate 10mL portions of dichloromethane. The glass funnel was removed and the separatory funnel was stoppered using a cork. Any help would be appreciated. The process of the present invention is preferably carried out at atmospheric pressure.
Followed all the steps with the appropriate ingredients and let the mix dry in 2 Pyrex dishes over night- from 6pm to 7am. Hook the flask to an aspirator, turn on the aspirator, and ascertain that the filter paper is pulled down onto the funnel by the vacuum. A second portion of dichloromethane was added to the brown layer in the separatory funnel and the process was repeated two more times. A process according to claim 6 wherein the inert gas is nitrogen. This caffeine was added to a mixture of 850 g of fresh water and 0.