Chengguang Yang

Designed copper–amine complex as an efficient template for one-pot synthesis of Cu-SSZ-13 zeolite with excellent activity for selective catalytic reduction of NOx by NH3

Low-cost copper-amine complex was rationally designed to be a novel template for one-pot synthesis of Cu-SSZ-13 zeolites. Proper confirmation and appropriate size make this complex fit well with CHA cages as an efficient template. The products exhibit superior catalytic performance on NH(3)-SCR reaction.

Highly Mesoporous Single-Crystalline Zeolite Beta Synthesized Using a Nonsurfactant Cationic Polymer as a Dual-Function Template

Mesoporous zeolites are useful solid catalysts for conversion of bulky molecules because they offer fast mass transfer along with size and shape selectivity. We report here the successful synthesis of mesoporous aluminosilicate zeolite Beta from a commercial cationic polymer that acts as a dual-function template to generate zeolitic micropores and mesopores simultaneously. This is the first demonstration of a single nonsurfactant polymer acting as such a template. Using high-resolution electron microscopy and tomography, we discovered that the resulting material (Beta-MS) has abundant and highly interconnected mesopores. More importantly, we demonstrated using a three-dimensional electron diffraction technique that each Beta-MS particle is a single crystal, whereas most previously reported mesoporous zeolites are comprised of nanosized zeolitic grains with random orientations. The use of nonsurfactant templates is essential to gaining single-crystalline mesoporous zeolites. The single-crystalline nature endows Beta-MS with better hydrothermal stability compared with surfactant-derived mesoporous zeolite Beta. Beta-MS also exhibited remarkably higher catalytic activity than did conventional zeolite Beta in acid-catalyzed reactions involving large molecules.

Seed-directed synthesis of zeolites with enhanced performance in the absence of organic templates

We demonstrate here a seed-directed synthesis (SDS) of Beta, Levyne, and Heulandite zeolites in the absence of organotemplates, where the seeds drive crystallization of the zeolites. Compared with conventional Beta synthesized in the presence of organic templates, Beta-SDS exhibits large textural parameters, stable Al species, and unprecedentedly high density of active sites, resulting in superior catalytic activity and selectivity for valuable products in catalysis.

Solvent-Free Synthesis of Silicoaluminophosphate Zeolites†

Solvent-Free Synthesis of Silicoaluminophosphate Zeolites Solvents, who needs them? Silicoaluminophosphate zeolites with various frameworks have been successfully synthesized by a solvent-free route. Catalytic tests for the conversion of methanol into olefins show that thus obtained SAPO-34 (see picture) exhibited catalytic performance comparable to that of zeolites made by the conventional hydrothermal route. Angewandte Chemie

Design and Synthesis of a Catalytically Active Cu-SSZ-13 Zeolite from a Copper-Amine Complex Template

The modern synthesis of zeolites typically uses organic structure-directing agents. Therefore, the developing of new templates is part of zeolite research. The design and synthesis of Cu-SSZ-13 using a novel template of a low-cost copper amine complex (Cu2+ coordinated with tetraethylenepentamine) were reported, where the copper amine complex is both a template for synthesizing the SSZ-13 structure and a source of copper species in the zeolite. The calculated size of the complex (0.728 nm x 0.922 nm) matches well with the CHA cages (0.73 nm x 1.2 nm), which are the building units of the SSZ-13 zeolite. Various techniques were used to investigate the chemical and physical properties of the synthesized zeolite. The results showed that the sample has the SSZ-13 zeolite structure, high crystallinity, adjustable Si/Al ratios, and controllable copper loading. Catalytic tests using the selective catalytic reduction of NOx with NH3 showed that the Cu-SSZ-13 was a superior catalyst, and it can be important for the abatement of environmentally harmful NOx.

Organotemplate-free and seed-directed synthesis of ZSM-34 zeolite with good performance in methanol-to-olefins

The methanol-to-olefins (MTO) reaction over zeolites is of great importance due to the shortage of crude oil, and we demonstrate here a fast, organotemplate-free, and seed-directed synthesis of ZSM-34 zeolite, designated as ZSM-34-S, having very high selectivity for propylene. When the temperature is at 140–180 °C, ZSM-34-S zeolite could be crystallized for 2–6 h in the presence of ZSM-34 crystals as seeds. For industry, a fast and organotemplate-free synthesis, a typically green route, means significant savings in energy and costs. Characterizations using XRD, SEM, 27Al and 29Si MAS NMR, and N2 sorption techniques show that the ZSM-34-S crystals grow from the seeds of ZSM-34 crystals in an amorphous aluminosilicate. Catalytic tests of the MTO reaction show that HZSM-34-S has a very high selectivity for propylene (55.2%), which is even higher than that (47.0%) of SAPO-34 under the same conditions. Moreover, the hydrothermal treatment of HZSM-34-S significantly improves the catalyst life for MTO due to decreasing acidic concentration and increasing anti-deactivation. The combination of a “green” synthesis and the good catalytic performance of ZSM-34-S would be potentially important for the highly effective conversion of methanol, which can be easily obtained from coal, natural gas, or biomass at a large scale.

One-pot synthesis of Fe-Beta zeolite by an organotemplate-free and seed-directed route

We have demonstrated that an organotemplate-free and seed-directed route has been successfully applied for synthesizing Fe-Beta zeolite with good crystallinity, high surface area, uniform crystals, and tetrahedral Al3+ and Fe3+ species. Catalytic tests for the direct decomposition of nitrous oxide indicate that the Fe-Beta exhibits excellent catalytic performance.

Organotemplate-free and one-pot fabrication of nano-rod assembled plate-like micro-sized mordenite crystals

Plate-like micro-sized MOR and Fe-MOR zeolite crystals assembled from highly uniform nano-rods are successfully fabricated by an organotemplate-free method during one-pot crystallization in the presence of a MOR seed solution. The seed solution rich in 4-membered rings plays a critical role for the formation of the unique nano-rod assembled structure.

High temperature synthesis of high silica zeolite y with good crystallinity in the presence of N-methylpyridinium iodide

A novel synthetic route is designed, employing both high temperature and a nontoxic organic structure-directing agent (SDA), for the synthesis of high silica zeolite Y. The N-methylpyridinium used as an organic SDA is stable during the synthesis, and the high silica zeolite Y shows high hydrothermal stability and good catalytic performance, as well as excellent adsorptive properties.