Phase-selective crystallization of nickel phosphate VSB-5 with (2-hydroxyethyl) trimethylammonium hydroxide as template

Abstract

Several nickel phosphate molecular sieves were synthesized by conventional heating (CH) and microwave assisted hydrothermal (MAH). Nickel phosphate VSB-5 (Versailles Santa Barbara-5) was synthesized with conventional oven for 72 h or with microwave for 1 h and followed by conventional oven for 48 h in the presence of (2-hydroxyethyl) trimethylammonium hydroxide as template. The phase transformation is observed by variation of CH time for the synthesis of nickel phosphate molecular sieves. At CH time of 24 h, the VSB-5 crystal together α-Ni2P2O7, Ni2P 4O12 and unknown phases were produced but the pure VSB-5 crystal was obtained in the CH time of 48 h or more. At high content of nickel, a mixture of α-Ni2P2O7, Ni 2P4O12 phases and small amount of VSB-5 crystal, was achieved but pure VSB-5 crystal was obtained in the lower level of nickel and other phases are vanished. An efficient ultrasonic-assisted aging was found for the synthesis of nickel phosphate molecular sieve, in which by ultrasonic mixing of 0.5 h followed microwave of 1 h, the CH time is significantly reduced from 48 to 24 h. The morphology of nickel phosphate crystals is highly influenced in the presence of ethylene glycol as co-solvent. © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.