Amino acids are utilized as medical raw materials and food additives. It is wellknown that most of the amino acids show polymorphism. Differences in the crystal structures affect the physical and chemical properties. Therefore, an effective method for polymorph control is required in the crystallization process. Polymorph control of L-arginine hydrochloride (L-ArgHCl) on antisolvent crystallization was achieved by ultrasonic irradiation. L-ArgHCl exhibits polymorphism and crystallizes into three distinct crystal forms. Without irradiation, the metastable form was selectively crystallized. In contrast, the unstable form was selectively crystallized by irradiation. Irradiation after the addition of an antisolvent led to a shorter induction time.

Most of the amino acids that are utilized as medical raw materials and food additives show polymorphism. To improve the physical and chemical properties of the crystals, an effective method for polymorph control is required in the crystallization process. In this study, polymorph control of L‐phenylalanine in cooling crystallization by ultrasonication was investigated. L‐Phenylalanine crystallizes in anhydrate and monohydrate forms. Without ultrasonication, a mixture of monohydrate and anhydrate forms was obtained. In contrast, the yield of monohydrate was increased by ultrasonication. In addition, ultrasonication shortened the induction time. It was considered that ultrasonic energy could supply the energy required for primary nucleation.

Most of the amino acids that are utilized as medical raw materials and food additives show polymorphism. To improve the functionality of amino acid crystals, an effective method of polymorph control is required in the crystallization process.Here, primary nucleation of L-arginine hydrochloride by ultrasonication was investigated. L-Arginine hydrochloride exhibits polymorphism, and it crystallizes into three distinct crystal forms. A cooling crystallization experiment was performed, and nucleation of each polymorph upon ultrasonication was observed. In addition, the nucleation was analyzed using the nucleation probability theory. The results indicate that ultrasonic irradiation would significantly induce the nucleation of a particular polymorph.

MFI-type zeolites and MWW-type zeolites containing Zn and/or Ga species were directly synthesized through the hydrothermal treatment of an amorphous gel containing Zn and/or Ga species with a high metal content in the absence of Al species. The metal-containing zeolites were applied to the aromatization of n-hexane to evaluate the catalytic performances. Ga-containing zeolites exhibited much higher catalytic activities than Zn-containing zeolites. The Ga-containing zeolites predominantly produced benzene through the dehydrocyclization of n-hexane among benzene, toluene, and xylenes (BTX), although cracked compounds were mainly produced. Higher crystallinity of the MFI zeolite containing both Zn and Ga species led to higher catalytic performances for both the dehydrocyclization and cracking. Furthermore, higher Ga content in the MFI zeolite containing both Zn and Ga species, which corresponds to lower Zn/Ga molar ratio, improved the catalytic activity for the aromatization of the cracked compounds to produce toluene and xylenes, whereas the selectivity for benzene was independent of the Ga content.