Experimental study of the zeolite LTA crystallisation parameters

Author

Arana Juve, Jan-Max

Abstract

In the context of an economy based on fossil fuels, hydrogen emerges as a promising alternative since it is a clean and energy-intensive fuel to carry out a necessary energy transition. Nowadays, the steam reforming of methane is the main hydrogen production pathway. This technique results in the production of hydrogen through the well-known water gas shift reaction. Aiming to purify the resulting hydrogen from these chemical reactions, zeolites emerge as good candidates due to their different pore sizes. Among them, the zeolite LTA seems to be one of the most promising materials for H2 purification purposes. The main goal of this thesis is to investigate the effect of several synthesis parameters on the particle size and purity of the LTA zeolite, with the aim to determine the minimum particle size keeping the LTA zeolite structure. The synthesis parameters evaluated are divided into three groups: process parameters (synthesis temperature, mixing temperature, and stirring influence), composition parameters for single trajectories (SiO2 content, Al2O3 content, Na2O content, water content, salt addition, and their combinations), and composition parameters for the combination of trajectories (SiO2 content, Al2O3 content, Na2O content, water content, and their combinations). SEM and XRD are the techniques used to characterize the samples.
The study reveals that a combination of trajectories, the SiO2/Al2O3 ratio, and the water content are the most effective parameters to decrease the particle size of the zeolite LTA, which can be reduced up to 150-200nm. This manuscript also provides ternary diagrams, where the results from the compositions are plotted, to summarize the particle size and phase of the experiments. The optimum region of the combination of trajectories diagram is found within the following axis ratios: 0,94-0,95 H2O, 0,04-0,05Na2O, and 0-0,01 SiO2.
The work is completed by the optimization of the concentration of the polyamide used to prepare the polymer supports, aiming to avoid the ring drying effect produced by the long filtration times of high concentrated polymer solutions (22%). Finally, the optimum number of zeolites to produce a homogeneous film onto the polymeric support is also studied, using SEM to evaluate the deposition.
This work includes a final chapter summarizing the possibilities of future work that can be done for a practical application.

Director

Llovell Ferret, Fèlix
Khaleel, Maryam  

Degree

IQS SE - Master’s Degree in Materials Science and Engineering

Date

2020-07-09