The invention provides a method for preparing low-water-content
solid methyl disulfonic acid through taking
methylene chloride as a
raw material. The method comprises the following steps of the processes of sulfonating,
barium treating, acidifying,
dewatering and the like, and mainly comprises the steps that an aqueous methyl disulfonic acid
system which is obtained after acidifying is mainly subjected to reduced pressure
distillation, when the
water content of the
system is 8-10% and the temperature is between 50-100 DEG C, an
organic solvent and a dehydrating agent are dripped, after reacting for 2-4 hours, the mixture is cooled to the
room temperature, filtrated and washed, and thus, the
solid methyl disulfonic acid with the
water content being lower than 0.50% is obtained, wherein the
organic solvent is selected from one of haloalkanes, ethers and alkanes or is the mixture of the haloalkanes, the ethers and the alkanes arbitrarily, and the use amount of the
organic solvent is 1-5 times of the quantity of methyl disulfonic acid; and the dehydrating agent is
thionyl chloride, and the
molar ratio of
thionyl chloride to the
water content of methyl disulfonic acid is (1.0-2.5):1. The
drying method is simple and ingenious, the
drying and dehydrating time is shortened, the production cost is lowered, and the method has great practicable value and industrial economic benefit.