Methanol was pumped into the etherification reactor using pneumatic pump, 98% sulfuric acid was slowly flowed into the reactor through metering drum, the temperature was controlled below 45 (open jacket for cooling as appropriate), then 3-methoxy-2-naphthalenecarboxylic acid was fed into the reactor, the feeding time was controlled at 0.5~1 hour, the temperature was raised to 76~83 for the reaction, and the reaction was started when the temperature reached 76 for 6 hours. The reaction conversion of methyl 3-methoxy-2-naphthalenecarboxylate was 94.5% in terms of 3-methoxy-2-naphthalenecarboxylic acid with excess methanol, and the remaining methanol was not carried out without reaction.
