The solubility of 2-mercapto-1,3,4-thiadiazol (MTD) in 13 pure solvents including methanol, ethanol, n-propanol, i-propanol, n-butanol, i-butanol, s-butanol, n-pentanol, i-pentanol, acetonitrile, ethyl formate, methyl acetate, and ethyl acetate was determined by a static gravimetric method at temperatures ranging from 278.15 to 318.15 K under atmospheric pressure. The results demonstrated that the experimental solubility of MTD increases with the increase of temperature. The mole fraction solubility of MTD in the solvent of methyl acetate was the highest and in acetonitrile was the lowest. The experimental solubility data were correlated with the Yaws model, the modified Apelblat model, the λh model, and the NRTL model. Relative average deviation (RAD) and root mean square deviation (rmsd) were used to evaluate the fitting degree of each model. The fitting results show that the NRTL model fitted the solubility data best among all selected models (with RAD = 0.0008, rmsd = 0.00005).

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Reaction crystallization to produce glycidyl trimethyl ammonium chloride (GTA) via epichlorohydrin with gas-state trimethylamine was investigated. The crystallization process of the GTA gas-liquid reaction was optimized by a seed method. The optimized technology can prepare GTA products with crystal form and purity greater than 97%. The crystallization process of GTA consists of four steps (i.e., addition of seed, dispersion of seed, growth of crystals on the seed surfaces, agglomeration and growth of crystal). Seed method and flow rate are the key factors affecting purity. The purity and particle size of GTA crystals were satisfactory as long as the operation was kept within the defined envelope. The experiments were conducted on a 1 L reactor and successfully scaled-up to 3000 L in industry.

The solubility of 2-mercapto-1,3,4-thiadiazol (MTD) in four kinds of aqueous mixed solvents including water + (methanol, ethanol, n-propanol, and acetone) was measured by the static gravimetric method in a temperature range of 278.15–323.15 K. The solubility of MTD in all selected aqueous mixed solvents was positively correlated with temperature. The solubility of MTD in the water + acetone solvent is higher than that in the other three solvents. There is a cosolvency phenomenon in the solvent systems of water + n-propanol and water + acetone. The polarity of good solvents plays an important role in the solubility of MTD in mixed solvents. Three thermodynamic models including the modified Jouyban–Acree model, NRTL model, and Wilson model were chosen to correlate the experimental data of MTD. The NRTL model fits the solubility data of MTD best among all of the selected thermodynamic models (with RAD = 0.0104, RMSD = 0.000432). The results demonstrate that all of the models can fit the experimental data well.