Al-ZSM-5 Nanocrystal Catalysts Grown from Silicalite-1 Seeds for Methane Conversion

Abstract

This study evaluated Al-ZSM-5 nanocrystals grown from silicalite-1 seed crystals as catalysts for the methane dehydroaromatization (MDA) reaction. Silicalite-1 seed crystals sized between 30 and 40 nm were used to grow Al-ZSM-5 under various synthesis conditions. The size of Al-ZSM-5 was significantly affected by the Si/Al ratio (SAR), synthesis time, and silica nutrients/seed crystal ratio (NSR). Larger crystals were obtained with an increased SAR in the synthesis sols. Gradual growth of Al-ZSM-5 occurred with synthesis time, although the growth in crystal size ceased at 5 h of synthesis at 120 °C, indicating the rapid growth of Al-ZSM-5 aided by the silicalite-1 seeds. Precise tuning of Al-ZSM-5 size was possible by changing the nutrient/silicalite-1 seed ratio; a higher NSR led to larger crystals. Two representative Al-ZSM-5 crystals with SARs of 35 and 140 were prepared for catalyst testing, and the crystal sizes were tailored to <100 nm by controlling NSR. The MDA reaction was conducted in the presence of the prepared Al-ZSM-5. The catalyst size exhibited distinct differences in catalyst stability, while the SAR of catalysts did not produce noticeable changes in the catalyst stability of the Al-ZSM-5 crystals and commercial zeolites in this reaction system.

Formation of Ni Species Anchored on a Silicalite-1 Zeolite Framework as a Catalyst with High Coke Deposition Resistance on Dry Reforming of Methane

“…However, in Ni-silicalite-1 HT and Ni-silicalite-1 DGC, the particle shape was oval-shaped compared to that of silicalite-1. Typically, coffin-shaped particles with a clean crystal surface state are observed for ultrahigh silica MFI-type zeolites such as silicalite-1, but it is known that the surface becomes oval-shaped when different elements are introduced . Therefore, a comparison of the four samples in the TEM image shows that metal species seemed to be introduced into the framework for one-pot synthesized samples.…”

Dual Functionality of MFI Zeolite Nanosheets as a PET Depolymerization Catalyst and a Flame Retardant in Repolymerized Polyurethane

“…During recipe preparation, the acid value of each batch was determined using the following equation, using bromothymol blue as the indicator normala cid value 0.25em ( mg / g ) = 56.1 ( V 0 − V 1 ) T m where V 1 represents the volume (mL) of the KOH solution used for the test sample, V 0 represents the volume (mL) of the KOH solution used for the blank sample, m represents the mass (g) of the sample, and T represents the normality (mol/L) of the KOH solution. The OH values were evaluated following the standard NF T 52-113 method, as previously described . Polyether polyol (PPG, CS-743) and MDI were used as additional polyols and isocyanates to facilitate repolymerization.…”

Size controllable synthesis of ZSM-5 zeolite and its catalytic performance in the reaction of methanol conversion to aromatics

“…On the other hand, although the nano-sized zeolite crystals display excellent performance in anti-coking, a decrease of the hydrothermal stability may also become significant owing to the increase of defect sites [20]. Therefore, to optimize the catalytic performance of zeolites, it is of importance to finely control the crystal size and to understand the effect of crystal size on the catalytic behaviours [21][22][23]. Nano-sized zeolite crystals have attracted considerable attention in the field of catalysis, and several methods including confined space synthesis, [24,25] low-temperature synthesis, [26,27] and seed-induction synthesis, [18,23,[28][29][30][31] have been devised to synthesize small-sized zeolite crystals.…”

“…Therefore, to optimize the catalytic performance of zeolites, it is of importance to finely control the crystal size and to understand the effect of crystal size on the catalytic behaviours [21][22][23]. Nano-sized zeolite crystals have attracted considerable attention in the field of catalysis, and several methods including confined space synthesis, [24,25] low-temperature synthesis, [26,27] and seed-induction synthesis, [18,23,[28][29][30][31] have been devised to synthesize small-sized zeolite crystals. Nowadays, the seed-induction synthesis method is paid more attention to because of its convenient and effective control of the crystal size of zeolites.…”