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

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, Ni₂P₄O₁₂ 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, Ni₂P₄O₁₂ 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)