**1. Introduction**

Zeolites are crystalline microporous aluminosilicates formed by a network of [SiO4] <sup>4</sup><sup>−</sup> and [AlO4] 5− tetrahedrals [1]. These materials have unique properties, such as their uniform microporous structure, hydrophilic surfaces, adjustable framework composition and strong chemical interactions with guest molecules. These properties have made them suitable candidates for widespread applications, including gas separation, adsorption, ion-exchange and catalysis [2–8]. The search for new materials is important especially for the petrochemical and pharmaceutical industries. In particular, potassium containing MER zeolite (K-MER), a zeolite which has framework topology similar to the mineral merlinoite; has drawn researchers' attention due to its three-dimensional pore channel system with medium pore sizes and high hydrophilicity. Thus, it is a promising material for adsorption [9], separation [10], and catalytic applications [11,12].

The physicochemical properties of zeolites are greatly dependent on their framework structures. Furthermore, the morphological properties such as crystal shape and size of a zeolite also have great impact on their physicochemical properties and applications [13,14]. For example, the shape of

zeolite crystals has been shown to exert a significant effect in adsorption and separation applications since it modulates molecular diffusion, accessibility, interfacial energy, molecular separation and inclusion properties [15,16]. Recently, several techniques to control the morphological properties of zeolites were reported [17]. For example, the use of different organic templates has shown to produce AlPO-5 zeolite-like materials with aggregated sphere, plate, rod, prism and barrel shapes [18–20]. The employment of different heating methods such as microwave and ultrasonic radiations exhibit significant effects on the overall crystal size and shape of the zeolite products [21,22]. In addition, the influence of the hydrothermal synthesis parameters, such as silica and alumina contents, alkalinity, amount of water, type of organic template, type of mineralizer, crystallization time and temperature, on the morphological and other properties of zeolites are also reported [23–25]. Nevertheless, knowledge about the impact of these synthesis parameters on the morphological behavior, crystallization kinetics and formation process of K-MER zeolite is still not well understood.

Therefore, we have studied the influence of synthesis parameters on the formation of K-MER zeolite (e.g. crystallization kinetics, structure and purity, morphology and crystal size). In addition, the influence of crystal morphologies on the catalytic behavior of K-MER zeolite in the cyanoethylation of methanol, under novel non-microwave instant heating, is also presented in this paper.
