Physico-Chemical nanomaterials science
Hierarchical Ti-, Sn- and Zr-containing zeolites as promising catalysts for ethyl lactate condensation into lactide
Mykhailo Kurmach1, Anatoliy Varvarin2 , Oleksandr Andreev3,           Volodymyr Brei2
1 L.V. Pisarzhevsky Institute of Physical Chemistry of the NAS of Ukraine,.  Prospect Nauki 31, Kyiv-03028, Ukraine
E-mail: mazinator3710@ukr.net
2 Institute for Sorption and Problems of Endoecology of NAS of Ukraine, Gen. Naumov str., 13, Kyiv-03164, Ukraine.
3   Institute of Geology, Taras Shevchenko National University of Kyiv, Vasylkivska str., 90, Kyiv-03022, Ukraine 

Ethyl lactate is an environmentally friendly solvent with effectiveness comparable to petroleum-based solvents which could be used in many different industry sectors. Also, ethyl lactate can be considered as raw materials for obtaining monomeric lactide, which is used for the production of biodegradable polymers, which transformation is described by total reaction 2C5H10O3 = C6H8O4 + 2C2H5OH. The key stage is transesterification reaction between two ethyl lactate molecules at the Lewis acid site (LAS) of catalyst. Hierarchical zeolites are promising catalysts for different acid-base process based on transformation of molecules with different size. 
Ti-, Sn- and Zr-containing hierarchical zeolites with MTW and MFI topology were synthesized using Gemini-type surfactants as structure-directing agents by the method similar as proposed by Ryoo [2]. Prepared materials possess high external surface (up to 255 m2∙g−1) and mesopore volume (up to 0.43 cm3 ∙g−1). Depending in the SDA structure it could be obtained MFI nanosheets and MTW nanoneedles. The general concentration of LAS for prepared zeolite samples varied in range from 15 up to 90 мmole∙g−1. In case of Ti-MTW and Ti-MFI LAS have predominantly weak strength, while Sn-MTW and Zr-MTW also contain significant amount of medium strength LAS. Ti-, Sn- and Zr-containing zeolites showed significant catalytic activity in vapour-phase process of ethyl lactate transformation into cis-lactide. Conversion of ethyl lactate reached up to 47%  and selectivity by target product is reached by 45%. The highest selectivity was achieved for Ti-MFI which containing the highest concentration of weak LAS.

1.	Choi M., Na K., Kim J., Sakamoto Y., Terasaki O., Ryoo R / Stable single-unit-cell nanosheets of zeolite MFI as active and long-lived catalysts //  Nature. – 2009. – 461. P. 246–249.