Monodispersed Ultrafine Zeolite Crystal Particles by Microwave Hydrothermal Synthesis

Conference · Tue Jan 01 00:00:00 EST 2008

OSTI ID:989701

Hu, Michael Z. ^[1]; Harris, Michael Tyrone ^[1]; Khatri, Lubna ^[1]

---

1. ORNL

Microwave hydrothermal synthesis of zeolites is reviewed. Monodispersed ultrafine crystal particles of zeolite (Silicalite-1) have been synthesized in batch reactor vessels by microwave irradiation heating of aqueous basic silicate precursor solutions with tetra propyl ammonium hydroxide as the templating molecule. The effects of major process parameters (such as synthesis temperature, microwave heating rate, volume ratio (i.e., the volume of the initial synthesis solution over the total volume of the reactor vessel), and synthesis time on the zeolite particle characteristics are studied using a computer-controlled microwave reactor system that allows real-time monitoring and control of reaction medium temperature. The changes in the morphology, size and crystal structure of the particles are investigated using scanning electron microscope, dynamic light scattering, X-ray diffraction, and BET surface analysis. We have found that the synthesis temperature, volume ratio, and heating rate play a significant role in controlling the particle size, uniformity, and morphology. Microwave processing has generated new morphologies of zeolite particles (i.e., uniform block-shaped particles that contain mixed gel-nanocrystallites and agglomerated crystal particles) that could not be made by a conventional hydrothermal process. At higher synthesis temperature and lower volume ratio, irregular block-shaped particles were produced, whereas increasing the volume ratio promoted the formation of monodispersed single-crystal particles with uniform shape. Our results clearly demonstrate that faster microwave heating is advantageous to enhance the zeolite crystallization kinetics and produces larger-size crystal particles in shorter time. In addition, zeolite crystallization mechanisms, depending on the microwave heating rate, were also discussed.

• Research Organization: Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). High Temperature Materials Lab. (HTML)
• Sponsoring Organization: USDOE Office of Science (SC)
• DOE Contract Number: DE-AC05-00OR22725
• OSTI ID: 989701
• Resource Relation: Conference: M&ST2008, Pittsburg, PA, PA, USA, 20081005, 20081005
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
AMMONIUM HYDROXIDES
CRYSTAL STRUCTURE
CRYSTALLIZATION
ELECTRON MICROSCOPES
HEATING
HEATING RATE
HYDROTHERMAL SYNTHESIS
IRRADIATION
KINETICS
LIGHT SCATTERING
MICROWAVE HEATING
MONITORING
MORPHOLOGY
PARTICLE SIZE
PRECURSOR
REACTOR VESSELS
SILICATES
SYNTHESIS
X-RAY DIFFRACTION
ZEOLITES