From the beginning of the basic concept of fractional crystallization from the melt , some thermodynamic problems such as crystal structure, solid solution, nucleus forming and growing-up, have been discussed by means of bond parameters in combination with the thermodynamic data.

Coupled with the living examples of refining metal by fractional crystallization,the kinetic formula of fractional crystallization in the refining of metals were deduced according to the concepts of diffusion and effective coefficient of separation and criteria for the effective of fractional crystallization.

While preserving the advantages of the original Witten process for manufacturing DMT,an improved Witten process has been developed featuring the use of new reactors and advanced separation technology including mixed oxidation,mixed esterification,vacuum crystallization,special rectification and fractional crystallization.

Mesoporous materials with the primary structure units of zeolite in the pore wall have been synthesized by a two-step crystallization process at 140 ℃ and characterized by XRD, N 2 physical adsorption/desorption, TEM, IR and NH 3-TPD methods.

The composite molecular sieves Beta/MCM-41 with different ratios of SiO2/Al2O3 were hydrothermally synthesized by two-step crystallization with tetraethylammonium hydroxide and cetyltrimethylammoniumbromide as templates.

Composite micro/mesoporous MCM-48/ZSM-5 materials were successfully prepared by using a two-step synthesis route.