Controllable and SDA-free synthesis of sub-micrometer sized zeolite ZSM-5. Part 2: Influence of sodium ions and ageing of the reaction mixture on the chemical composition, crystallinity and particulate properties of the products

Precise control of the size of zeolite B-ZSM-5 based on seed surface crystallization

“…Based on seed surface crystallization mechanism, N. Ren et al proposed a method for facile, rapid, controllable and low-cost synthesis of ZSM-5 zeolite with submicron-size. [40][41][42][43] Furthermore, crystal growth kinetics, crystalline yield, and physicochemical properties of zeolite nanoparticles as a function of the seed concentration and synthesis temperature were addressed by V. Valtchev et al 44 However, most reports focused on the study of the seed role under a single system. Few studies have revealed the effect of the synthesis system on the particle size of ZSM-5 in the presence of seed crystals.…”

Crystallization of Sub-Micrometer Sized ZSM-5 Zeolites in SDA-Free Systems

“…In the other words, when A < 0.004, fully crystalline product cannot be obtained for t c ≤ 2 h regardless to the content of sodium ions in the reaction mixture [54,55]. Fig.…”

“…According to the principals of aggregation of zeolite particles, the tendency to aggregation decreases with the increase of the (negative) crystal surface charge (repulsion effect), and increases with the increase of the concentration of the "compensating" Na + ions [55]. It is evident that at the simultaneous increase of OH -ions and Na + ions with increasing alkalinity, A, the repulsive force prevails the "compensating" effect of Na + ions.…”

“…Taking into consideration the background of ZSM-5 synthesis conditions, and accompanying this with the basic knowledge of seed induced synthesis, we have developed a seed surface crystallization (SSC) approach, in which the sub-micrometer sized ZSM-5 zeolites can be obtained in a controllable manner [50,54,55]. More importantly, the growth of crystalline end products is achieved in a heterogeneous, SDA-free crystallization system, which is good basis for their further industrial-scale production and use in various applications.…”

Synthesis of colloidal silicalite-1 at high temperatures

“…In addition to their fundamental importance, colloidal silicalite-1 crystals have been used extensively as seeds for the fabrication of supported zeolite layers and three-dimensional structures [7]. More recently, silicalite-1 seeds were employed in the revitalized seed-induced synthesis method, for preparation of nanosized ZSM-5 [8][9][10][11][12]. Despite the tremendous importance of systems yielding monodisperse suspensions of silicalite-1, there are technological drawbacks, such as employment of abundant amounts of expensive and toxic TPA template solutions, expensive silica sources (tetraethyl orthosilicate, TEOS), long synthesis times and low product yields, which prohibit their commercialization.…”