Methanol → Methyl Lactate

Participants

Reaction Steps

2500 g of highly pure S-(−)-methyl lactate from reservoir (1), having purity 99.81% by on GC analysis as methyl lactate, obtained by reactive distillation of lactic acid and methanol followed by fractional distillation to isolate pure methyl lactate, was charged to the glass lined stirred reactor (4), having capacity of 10 L and was further charged with 2500 g of distilled water (De-ionized, glass distilled) from reservoir (2), along with 500 g of Purac Inc, USA make pure lactic (90% by wt on HPLC analysis) from reservoir (3). Temperature of reboiler was maintained continuously at 100° C. by hot oil circulator (5). The methanol vapors formed during hydrolysis reaction were allowed to rise through column (6) and condensed in cooler (7) and fractionated with proper reflux so as to get top temperature at 65° C. The methanol formed was continuously collected in reservoir (10) through cooler (8). Any trace amount of methanol or unconverted methyl lactate was recovered and recycled. After collecting desired amount of methanol in reservoir (10) through cooler (8), 1000 g of distilled water from reservoir (2) was charged to reactor (4) so as to get complete conversion of methyl lactate in to L-(+)-lactic acid. The water was removed by distillation and was collected in reservoir (9) through cooler (8) so as to get lactic acid free from methanol and methyl lactate in trace amount. After removing desired amount of water, the lactic acid in the reactor (4) was treated with 0.5% by wt of total material with pre-treated activated charcoal from reservoir (11). Where pretreatment of activated charcoal was done by washing activated charcoal with 10% solution of pure L-(+)-lactic acid in water. The pure L-(+)-lactic acid and the pre-treated activated charcoal in reactor (4) was stirred for 30 minutes, cooled to room temperature and the contents of reactor (4) were filtered on Buchner filter (12), to get highly pure L-(+)-lactic acid as the filtrate which was stored in reservoir (13). This L-(+)-lactic acid filtrate from (13) was clear and transparent and was further concentrated at 80° C. and under vacuum of 100 mm Hg till 90% by w/w of L-(+)-lactic acid solution in water was obtained. This L-(+)-lactic acid was analyzed by HPLC and showed lactic acid of 99.81% purity by wt. on water free basis and having optical purity of 99.9% as analyzed by RANDOX Enzyme Kit method. The L-(+)-lactic acid obtained was also free from any odor and color.

Provenance & Evidence