Preparation of ETS-10 Microporous Phase Pellets with Color Change Properties.

Pierantonio De Luca,Carlo Siciliano,Anastasia Macario,Carmelo Mastroianni,Janos B Nagy

doi:10.3390/gels5030042

Abstract

The main scope of the present work is to synthesize pH-responsive Engelhard titanium silicate (ETS)-10 phase crystalline pellets through the smart modification of a synthetic process which was previously applied to the preparation of other phases. The original preparative method, which envisages the use of the same initial synthesis as a binder for the preparation of pellets, was modified by adding an appropriate pH indicator to a number of systems subject to this investigation. It should be noted that the modified process was never before used to give access to pH-responsive ETS-10 phase pellets, and it is disclosed here for the first time. The study started from the definition of the best experimental conditions, which were optimized by analyzing the effects of temperature and system composition. The addition of the pH indicator did not alter the physicochemical characteristics and reactivity of the system. The pH-responsive ETS-10 phase crystalline pellets were characterized by an adequate mechanical strength and by a high capability to change color. The latter aspect can be particularly useful when this material is used in catalytic processes whose performance is strictly dependent on the pH value. The amount of gel used, as well as the working temperature, were the main critical parameters to be controlled during the preparation of pH-responsive ETS-10 phase crystalline pellets. The pellets were fully characterized by X-ray diffraction in order to investigate and identify the possible phases, and by using a hardness tester to measure the compressive strength. Finally, toning tests were performed.

Highlights

The environmental problem, more and more incumbent, is being tackled in various fields of research, such as that of eco-sustainable materials with low environmental impact [1,2,3,4,5,6,7,8], and through new materials that can be used for the removal and photodegradation of environmental pollutants [9,10]
The Engelhard titanium silicate (ETS)-10 phase is a microporous material that was synthesized for the first time by Kuznicki [15]
ETS-10crystalline /xerogel = 9 treated at 190 ◦ C by hydrothermal synthesis

Summary

Introduction

The environmental problem, more and more incumbent, is being tackled in various fields of research, such as that of eco-sustainable materials with low environmental impact [1,2,3,4,5,6,7,8], and through new materials that can be used for the removal and photodegradation of environmental pollutants [9,10]. Data from the literature report that hetero atoms were inserted into the structure of these materials to modify their properties [25,26] This material can be used in many sectors thanks to its particular peculiarities. The color change of the ETS-10 phase crystalline pellets might be a characteristic of particular importance when this material is applied for catalytic processes whose performance is thought to be highly dependent on the pH value in which the same process takes place. The new method uses the crystalline phase and its own initial gel, which after a minimal pre-treatment is employed as a binder for the preparation of pellets. The effects of adding this unusual component to the ETS-10 phase precursor system, known to be sensitive to any modification, are carefully investigated

Results and Discussion

X-ray diffraction spectra of pellets a function of

Mechanical compressive strength theETS-10

Conclusions

Materials and Methods