In a process to synthesize the pain reliever acetylsalicylic acid (ASA, also known as aspirin), the effluent stream from the final reactor contains 11 wt% ASA and 2 wt% sodium acetate in water. The final dry product is to be obtained by drying, crystallizing, or some combination. The product purity, measured as wt% ASA in the final dry powder, is a key value. If the water is evaporated off, what product purity results? The sodium acetate can be considered to be infinitely soluble in water, so an alternative process is suggested. Part of the water is removed by evaporation, then the concentrated solution is cooled to crystallize some pure ASA. The filter cake, which contains 1 kg entrained solution for each 4 kg of ASA crystals, is then dried. At the crystallizer/filter temperature, the solubility of ASA in water is 35 wt%. If enough water is evaporated so that half of the ASA fed is recovered as dry product, what is the ASA product final purity? How much water is removed per 100 kg of reactor effluent? Obtain a general equation that relates product purity to fractional recovery. What purity do you predict at 90% ASA recovery? At 10% recovery? What changes would you suggest to this process that would increase yield, purity, or both?
In a process to synthesize the pain reliever acetylsalicylic acid (ASA, also known as aspirin), the effluent stream from the final reactor contains 11 wt% ASA and 2 wt% sodium acetate in water. The final dry product is to be obtained by drying, crystallizing, or some combination. The product purity, measured as wt% ASA in the final dry powder, is a key value.
If the water is evaporated off, what product purity results?
The sodium acetate can be considered to be infinitely soluble in water, so an alternative process is suggested. Part of the water is removed by evaporation, then the concentrated solution is cooled to crystallize some pure ASA. The filter cake, which contains 1 kg entrained solution for each 4 kg of ASA crystals, is then dried. At the crystallizer/filter temperature, the solubility of ASA in water is 35 wt%. If enough water is evaporated so that half of the ASA fed is recovered as dry product, what is the ASA product final purity? How much water is removed per 100 kg of reactor effluent?
Obtain a general equation that relates product purity to fractional recovery. What purity do you predict at 90% ASA recovery? At 10% recovery?
What changes would you suggest to this process that would increase yield, purity, or both?
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