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Effect of Stannic Species Modification on the Acidity of Silicalite-1 and its Enhancement in Transforming Ethylenediamine to Heterocyclic Amines

Department of Catalytical Chemistry and Engineering, State Key Laboratory of Fine Chemicals, Dalian University of Technology, Dalian 116024, China
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Catalysts 2020, 10(2), 211; https://doi.org/10.3390/catal10020211
Received: 17 January 2020 / Revised: 1 February 2020 / Accepted: 7 February 2020 / Published: 10 February 2020
(This article belongs to the Section Catalytic Materials)
In this study, a series of SnO2 modified zeolite catalysts (Snx-S-1; x is the weight percentage of Sn) were prepared with SnCl2 and a defective Silicalite-1 (S-1) zeolite via facile deposition–precipitation method. It was found that the stannic species modified all-silica zeolite catalysts were active for the intermolecular condensation of ethylenediamine (EDA) to 1, 2-Diazabicyclo [2, 2, 2] octane (TEDA) and piperazine (PIP). The best catalyst Sn6-S-1 (6 wt.% Sn loading) showed 86% EDA conversion and 93% total selectivity to TEDA and PIP. By contrast, the defective S-1 zeolite parent showed only approximately 9% EDA conversion under the same conditions. With the help of catalyst characterization techniques including hydroxyl vibration and pyridine adsorption FT-IR spectroscopy (transmission mode), the enhancement of the catalytic activity of the SnO2 modified zeolite catalysts (Snx-S-1) was mainly attributed to the formation of mild Lewis acid sites in the siliceous zeolite. Both the hydroxyl nests of the defective S-1 zeolite and the dispersed SnO2 clusters should be the important factors for the formation of mild Lewis acid sites on the modified zeolite. Based on the catalytic performance of the modified zeolite in the conversion of EDA to PIP and TEDA, it is inferred that the mildly acidified defective S-1 zeolite by the SnO2 deposition modification might become a very active and durable catalyst for reactions involving strongly alkaline reactants and products.
Keywords: defective Silicalite-1; SnO2 modification; acidity; condensation of ethylenediamine defective Silicalite-1; SnO2 modification; acidity; condensation of ethylenediamine
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MDPI and ACS Style

Zhang, Y.; Lin, L.; Zheng, X.; Liu, C.; Zhu, Q.; Guo, H. Effect of Stannic Species Modification on the Acidity of Silicalite-1 and its Enhancement in Transforming Ethylenediamine to Heterocyclic Amines. Catalysts 2020, 10, 211.

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