Method of preparing para-aminophenol

Claim 1

A METHOD FOR PREPARING PARA-AMINOPHENOL COMPRISING THE STEPS OF HEATING A COMPOSITION COMPRISING PARANITROCHLOROBENZENE, SODIUM HYDROXIDE AND WATER FOR THREE HOURS AT 150*-160*C. AND 60-75 P.S.I.G. PRESSURE AND THEN FOR SIX HOURS AT 160*C. AND 60-75 P.S.I.G. PRESSURE; FILTERING THE RESULTING HOT SOLUTION; COOLING THE FILTRATE BELOW THE BOIL AND ADDING THERETO SODIUM HYDROSULFIDE; HEATING THE HYDROSULFIDE CONTAINIANG FILTRATE IN A CLOSED CONTAINER FOR ONE HOUR AT 130*-135*C. AND 30-40 P.S.I.G. PRESSURE AND THEREAFTER HEATING FOR 2-4 1/2 HOURS AT 140*-165*C. AND 40-65 P.S.I.G. PRESSURE; COOLING THE RESULTING SOLUTION TO 110*C; ADDING TO THE SOLUTION WHILE IT IS IN A CLOSED SYSTEM AND AS COOLING CONTINUES ENOUGH SULFUR DIOXIDE TO ADJUST THE PH TO 2-4; ADDING ACTIVATED CHARCOAL TO THE SOLUTION; HEATING THE CHARCOAL CONTAINING SOLUTION IN A CLOSED SYSTEM FOR ONE HOUR AT 70*-90*C.; EXTRACTING THE CHARCOAL AND OTHER INSOLUBLES FROM THE SOLUTION; DILUTING THE RESULTING SOLUTION WITH WATER TO 5-10% BY WEIGHT CONCENTRATIN OF SULFUROUS ACID SALT OF PARA-AMINOPHENOL; ADJUSTING THE TEMPERATURE OF THE SOLUTION TO 50*-95*C. AND ADDING THERETO FIRST NAOH AND THEN SODA ASH UNTIL THE PH BECOMES 6.0-6.9; COOLING THE RESULTING SLURRY TO 30*C. AND ALLOWING IT TO STAND WHILE PARA-AMINOPHENOL PRECIPITATES THEREFROM; ISOLATING THE PARA-AMINOPHENOL; WASHING THE PARA-AMINOPHENOL WITH AQUEOUS SODIUM BISULFITE; AND DRYING THE PARA-AMINOPHENOL UNDER VACUUM.

Claim 2

A METHOD FOR PREPARING PARA-AMINOPHENOL COMPRISING THE STEPS OF HEATING A COMPOSITION COMPRISING PARANITROCHLOROBENZENE, SODIUM HYDROXIDE AND WATER FOR THREE HOURS AT 150*-160*C. AND 60-75 P.S.I.G. PRESSURE AND THEN FOR SIX HOURS AT 160*C. AND 60-75 P.S.I.G. PRESSURE; FILTERING THE RESULTING HOT SOLUTION; COOLING THE FILTRATE BELOW THE BOIL AND ADDING THERETO SODIUM HYDROSULFIDE; HEATING THE HYDROSULFIDE CONTAINIANG FILTRATE IN A CLOSED CONTAINER FOR ONE HOUR AT 130*-135*C. AND 30-40 P.S.I.G. PRESSURE AND THEREAFTER HEATING FOR 2-4 1/2 HOURS AT 140*-165*C. AND 40-65 P.S.I.G. PRESSURE; COOLING THE RESULTING SOLUTION TO 110*C; ADDING TO THE SOLUTION WHILE IT IS IN A CLOSED SYSTEM AND AS COOLING CONTINUES ENOUGH SULFUR DIOXIDE TO ADJUST THE PH TO 2-4; ADDING ACTIVATED CHARCOAL TO THE SOLUTION; HEATING THE CHARCOAL CONTAINING SOLUTION IN A CLOSED SYSTEM FOR ONE HOUR AT 70*-90*C.; EXTRACTING THE CHARCOAL AND OTHER INSOLUBLES FROM THE SOLUTION; DILUTING THE RESULTING SOLUTION WITH WATER TO 5-10% BY WEIGHT CONCENTRATIN OF SULFUROUS ACID SALT OF PARA-AMINOPHENOL; ADJUSTING THE TEMPERATURE OF THE SOLUTION TO 50*-95*C. AND ADDING THERETO FIRST NAOH AND THEN SODA ASH UNTIL THE PH BECOMES 6.0-6.9; COOLING THE RESULTING SLURRY TO 30*C. AND ALLOWING IT TO STAND WHILE PARA-AMINOPHENOL PRECIPITATES THEREFROM; ISOLATING THE PARA-AMINOPHENOL; WASHING THE PARA-AMINOPHENOL WITH AQUEOUS SODIUM BISULFITE; AND DRYING THE PARA-AMINOPHENOL UNDER VACUUM.