Understanding the dissolution of zeolites.

Area of Science:

• Geochemistry
• Materials Science
• Chemical Engineering

Background:

• Zeolites are microporous aluminosilicates with diverse natural and industrial applications.
• Understanding zeolite dissolution in acidic environments is crucial for various processes.
• Limited scientific knowledge exists regarding the dissolution mechanisms of zeolites in hydrochloric acid.

Purpose of the Study:

• To investigate the influence of the silicon-to-aluminum (Si-to-Al) ratio on zeolite framework dissolution in aqueous hydrochloric acid solutions.
• To elucidate the mechanism controlling selective aluminum removal and its effect on silicon dissolution.
• To establish the general role of the Si-to-Al ratio in zeolite dissolution kinetics and outcomes.

Main Methods:

• Experimental dissolution of Type 4A, analcime, and Type Y zeolites in hydrochloric acid.
• Analysis of dissolution rates and products, including silicate precipitation.
• Construction of zeolite framework models and comparison with experimental data (SEM, dissolution rates).

Main Results:

• The Si-to-Al ratio universally controls zeolite dissolution, with selective aluminum removal preceding silicon dissolution.
• Type 4A zeolite (Si-to-Al=1.0) showed stoichiometric dissolution, complete silicon dissolution, and subsequent silicate precipitation.
• Analcime (Si-to-Al=2.0) dissolved non-stoichiometrically with partial silicon dissolution and precipitation.
• Type Y zeolite (Si-to-Al=3.0) exhibited minimal silicon dissolution and amorphous silicate particle formation due to insufficient aluminum.

Conclusions:

• Zeolite dissolution is governed by the Si-to-Al framework ratio, impacting aluminum and silicon removal rates.
• The dissolution mechanism is consistent across different zeolite framework types, emphasizing the Si-to-Al ratio's universal role.
• Findings have significant implications for optimizing petroleum reservoir stimulation treatments.