Comparing synthesis routes to nano-crystalline zeolite ZSM-5

Abstract

Aiming at the identification of a suitable synthesis route to zeolite ZSM-5 with acidic properties and crystal diameters of about 100 nm or less, we have evaluated four different preparation methods. Three of these have been adopted from the literature, and one was developed by ourselves. The products, all of which synthesised from mixtures with a fixed Si/Al ratio of 60, were inspected by means of X-ray diffraction, scanning electron microscopy, laser-Doppler anemometry and temperature-programmed desorption of ammonia. Two methods turned out to be successful and well reproducible. The first one comprises hydrothermal crystallisation from clear solutions under autogenous pressure and has been described previously by van Grieken et al. The other approach is based on the use of colloidal silicalite-1 seed crystals in an open-vessel crystallisation at atmospheric pressure. The crystal size distribution and the Si/Al ratio of the products can be well controlled. The products from both synthesis types could be transferred into the H-form by conventional means without causing collapse of the crystal structure.

Synthesis and characterization of nano-ZSM-5 zeolite and its application for electrocatalytic oxidation of formaldehyde over modified carbon paste electrode with ion exchanged synthesized zeolite in alkaline media

“…The zeolite nano particles are more efficient catalysts and adsorbent materials because of their higher surface areas compared to the conventional micron size zeolites. By reducing the particle size, the diffusion path lengths will decrease and active sites will be accessible readily [7][8][9][10][11][12][13]. Among all zeolite types, ZSM-5 is important both from industrial and academic point of view due to its unique shape selectivity property, acidity, thermal stability and application in petro-chemical industry, oil refinery and environmental catalysis [14][15][16][17].…”

MFI Zeolite with Small and Uniform Intracrystal Mesopores

“…Recently, several efforts have been made to reduce the diffusion path length in zeolites by confining crystal growth to a nanometer length scale [2][3][4][5][6][7][8] or by providing intracrystal mesopores during synthesis.[9-13] The latter strategy is intrinsically appealing, in part, because it precludes the need for colloidal crystal formation and avoids the drawbacks associated with nanoparticle processing. Moreover, the presence of mesopores in zeolite crystals offers the possibility of improving product selectivity in the catalytic cracking of polymeric molecules.…”

Optimization of Parameters for Synthesis of MFI Nanoparticles by Taguchi Robust Design

“…Reding and co-workers surveyed the synthetic method for nanocrystalline ZSM-5 and reported a new procedure based on two crystallization steps, both under atmospheric pressure that yielded crystals with sizes ranging from 100 to 300 nm [12].…”

“…The particle size and size distribution of MFI-type zeolite are influenced by different variables: aluminum source [11,13], silica source [14][15][16], aluminum content [13], template/ silica molar ratio [11,13,17], nature of cations present in the synthesis medium [11,13], alkalinity [11,13,18], temperature of crystallization [19][20][21], presence of seeds [12], water content [11,13], aging time [17,22], time of crystallization [23,24], etc.…”