Shanmugam Palani Elangovan

Nepheline from K2CO3/Nanosized Sodalite as a Prospective Candidate for Diesel Soot Combustion

Nepheline group materials obtained by a thermal treatment of K2CO3-supported nanosized sodalite are identified as cost-effective materials which show promising activity and durability toward diesel soot combustion.

Widening Synthesis Bottlenecks: Realization of Ultrafast and Continuous‐Flow Synthesis of High‐Silica Zeolite SSZ‐13 for NOx Removal

Characteristics of zeolite formation, such as being kinetically slow and thermodynamically metastable, are the main bottlenecks that obstruct a fast zeolite synthesis. We present an ultrafast route, the first of its kind, to synthesize high-silica zeolite SSZ-13 in 10 min, instead of the several days usually required. Fast heating in a tubular reactor helps avoid thermal lag, and the synergistic effect of addition of a SSZ-13 seed, choice of the proper aluminum source, and employment of high temperature prompted the crystallization. Thanks to the ultra-short period of synthesis, we established a continuous-flow preparation of SSZ-13. The fast-synthesized SSZ-13, after copper-ion exchange, exhibits outstanding performance in the ammonia selective catalytic reduction (NH3 -SCR) of nitrogen oxides (NOx ), showing it to be a superior catalyst for NOx removal. Our results indicate that the formation of high-silica zeolites can be extremely fast if bottlenecks are effectively widened.

Catalysis with Microporous Aluminophosphates and Silicoaluminophosphates Containing Transition Metals

The literature related to the catalytic activity of aluminophosphate (AlPO 4 ) and silicoaluminophosphate (SAPO) molecular sieves containing transition metal ions and/or transition metal clusters is reviewed. Microporous crystalline metal aluminophosphates (MeAPOs) and metal silicoaluminophosphates (MeAPSOs) represent an important group of inorganic materials because of their large potential as adsorbents and catalysts. This review focuses mainly on the catalytic activity of MeAPOs and MeAPSOs in comparison with the corresponding MeAPSOs covering the literature through 2008. The catalysis over these materials is summarized and discussed with respect to the catalytic performance, possible reaction mechanisms, and potential applications.

Pioneering In Situ Recrystallization during Bead Milling: A Top-down Approach to Prepare Zeolite A Nanocrystals

Top-down approach has been viewed as an efficient and straightforward method to prepare nanosized zeolites. Yet, the mechanical breaking of zeolite causes amorphization, which usually requires a post-milling recrystallization to obtain fully crystalline nanoparticles. Herein we present a facile methodology to prepare zeolite nanocrystals, where milling and recrystallization can be performed in situ. A milling apparatus specially designed to work under conditions of high alkalinity and temperature enables the in situ recrystallization during milling. Taking zeolite A as an example, we demonstrate its size reduction from ~3 μm to 66 nm in 30 min, which is quite faster than previous methods reported. Three functions, viz., miniaturization, amorphization and recrystallization were found to take effect concurrently during this one-pot process. The dynamic balance between these three functions was achieved by adjusting the milling period and temperature, which lead to the tuning of zeolite A particle size. Particle size and crystallinity of the zeolite A nanocrystals were confirmed by X-ray diffraction, scanning electron microscopy, transmission electron microscopy and water adsorption-desorption. This work presents a pioneering advancement in this field of nanosized zeolites, and will facilitate the mass production as well as boost the wide applications of nanosized zeolites.

“Super Hydrocarbon Reformer Trap” for the Complete Oxidation of Toluene Using Iron‐Exchanged β‐Zeolite with a Low Silicon/Aluminum Ratio

This study examines the effects of the Si/Al ratio and metal cation exchange of a zeolite on the ability to adsorb and reform unburned hydrocarbons (HCs) in emissions from gasoline vehicles. Iron ion‐exchanged β‐zeolites with a low Si/Al ratio not only trap but also oxidize HCs efficiently, which spurred on the development of a “super HC reformer trap”. Toluene temperature‐programmed desorption experiments in an O2‐containing stream revealed that >90 % of the adsorbed toluene was converted into CO2, and other oxygenates were not observed. This material could be reused and it retained its performance. The strong adsorption of toluene on the zeolites was derived from two synergistic effects: (1) electrostatic interactions between the π orbital of the aromatic ring and the p orbital of the metal cation and (2) interactions between the positively polarized methyl group of toluene and a basic oxygen atom in the zeolite framework. This new material will pave the way for low‐emission, Pt‐free vehicles.

Preparation of zeolitic mesoporous aluminosilicate by vapor phase transport method

A vapor phase transport method is applied to the synthesis of composite zeolitic mesoporous aluminosilicate. Analytical data suggest that aluminosilicate in mesopore wall is partially transformed to a zeolitic unit, and the composite shows the zeolitic nature.