日本ゼオライト学会　刊行物 Publication of Japan Zeolite Association

The crystallinity and crystal form of zeolites, prepared through the wet method, are often strongly affected by synthetic conditions. The selection of appropriate raw materials and its compositions makes possible to form highly crystallized zeolites even at much lower temperatures than those usually used in zeolite synthesis (>100°C) without using any special reaction vessels such as autoclave. The zeolite formation proceeds comparatively slowly upon such mild heating, meaning that it is very convenient for the monitoring the zeolite crystallization processes and crystal form change. This paper mainly described the results of our synthesis of Na–Ca zeolites at 80°C and their reaction mechanisms. In addition, this low-temperature synthetic technique (around 100°C) was also applied to the production of ultramarine with a sodalite-like structure, known as an artificial mineral of lapis lazuli, although ultramarine usually requires high temperatures such as 800 – 950°C in dry process. The present idea is based on the fact that sodalites can also be synthesized through the low-temperature hydrothermal synthesis.