Towards the sustainable synthesis of microporous and layered titanosilicates: mechanochemical pre-treatment reduces the water amount

resumo

There has been growing awareness of the importance of developing environmentally friendly chemical processes. In this context, the synthesis of materials by mechanical grinding or milling holds much promise. Microporous zeolitic materials are well-known for their importance as catalysts, ion exchangers, and in gas separation and storage. Here, the incorporation of a mechanosynthesis (ball milling) step in the preparation of an important class of zeolite-type materials, microporous titanosilicates, is shown to reduce by one to two orders of magnitude the amount of water used, as compared with the conventional hydrothermal synthesis. Accordingly, no water was added to the reagents in the synthesis of the small-pore synthetic analogue of minerals sitinakite (Na2Ti2O3SiO4 center dot 2H(2)O), now a commercial Cs+ ion exchanger, and ivanyukite-K (also known as GTS-1, HK3Ti4O4(SiO4)center dot 4H(2)O). The preparation of the important microporous titanosilicate ETS-10 ((Na,K)(2)TiSi5O13 center dot nH(2)O), microporous AM-2 (K2TiSi3O9 center dot H2O), and the analogue of the layered mineral natisite (Na2TiO(SiO4)) required only the addition of a very small amount of water. The increased reactivity of the ball-milled reaction mixture is ascribed to the reduction of the precipitated silica particle size (ETS-10 synthesis) and the increased number of silica nanoparticle silanol groups (ETS-10 and sitinakite synthesis). Moreover, in general, the ball milling step also decreased the synthesis time considerably, in most cases resulting in significant energy saving (3-34 times) over conventional hydrothermal synthesis. This work shows that mechanosynthesis enables the preparation of microporous (and layered) titanosilicates by a process that is more sustainable than the conventional hydrothermal synthesis and is also amenable for upscaling.

palavras-chave

ION-EXCHANGE PROPERTIES; SOLVENT-FREE SYNTHESIS; HYDROTHERMAL SYNTHESIS; CRYSTAL-STRUCTURES; AQUEOUS-SOLUTIONS; TITANIUM SILICATE; ETS-10; ZEOLITE; SELECTIVITY; STRONTIUM

categoria

Chemistry; Science & Technology - Other Topics

autores

Santos-Vieira, ICMS; Lin, Z; Rocha, J

Grupos

G1 - Materiais Porosos e Nanossistemas

Projectos

CICECO - Aveiro Institute of Materials (UIDB/50011/2020)

CICECO - Aveiro Institute of Materials (UIDP/50011/2020)

Associated Laboratory CICECO-Aveiro Institute of Materials (LA/P/0006/2020)

Rede Nacional de Ressonância Magnética Nuclear (PTNMR)

agradecimentos

This work received financial support from PT national funds (FCT/MCTES, Fundacao para a Ciencia e Tecnologia and Ministerio da Ciencia, Tecnologia e Ensino Superior (PIDDAC)) through the CICECO-Aveiro Institute of Materials (UIDB/50011/2020, UIDP/50011/2020 and LA/P/0006/2020). The NMR spectrometers are part of the National NMR Network (PTNMR) and are partially supported by Infrastructure Project No. 022161 (co-financed by FEDER through COMPETE 2020, POCI and PORL and FCT through PIDDAC. The position held by I. C. M. S. S. V. (Ref. 197_97_ARH-2018) was funded by national funds (OE), through FCT, I. P., in the scope of the framework contract foreseen in the numbers 4, 5 and 6 of article 23 of the Decree-Law 57/2016 of 29 August, changed by Law 57/2017 of 19 July.