2002 Progress Report: Development of Nanocrystalline Zeolite Materials as Environmental Catalysts: From Environmentally Benign Synthesis to Emission AbatementEPA Grant Number: R829600
Title: Development of Nanocrystalline Zeolite Materials as Environmental Catalysts: From Environmentally Benign Synthesis to Emission Abatement
Investigators: Larsen, Sarah C. , Grassian, Vicki H.
Institution: University of Iowa
EPA Project Officer: Lasat, Mitch
Project Period: January 1, 2002 through December 31, 2004
Project Period Covered by this Report: January 1, 2002 through December 31, 2003
Project Amount: $350,000
RFA: Exploratory Research: Nanotechnology (2001) RFA Text | Recipients Lists
Research Category: Nanotechnology , Safer Chemicals
The objectives of this research project involve the development of nanometer-sized zeolites and zeolite nanostructures as environmental catalysts. Zeolites, which are widely used in applications in separations and catalysis, are aluminosilicate molecular sieves with pores of molecular dimensions. The crystal size of zeolites formed during conventional synthesis range in size from 1,000 to 10,000 nm. However, for some applications, it would be advantageous to employ much smaller nanometer-sized zeolite crystals in the range of 10-100 nm. Specific advantages to be gained by using zeolite nanostructures include facile adsorption and desorption, the ability to form dense films to facilitate separations applications, and optical transparency. The specific objectives of this research project are to conduct synthesis and characterize nanocrystalline zeolites, and to use the nanocrystalline zeolites as environmental catalysts.
The major accomplishments of this work during Year 1of the project are listed below:
· Synthesis of nanocrystalline NaY using hydrothermal synthetic methods.
· Characterization of nanocrystalline NaY particles using powder x-ray diffraction, scanning electron microscopy (SEM), solid state nuclear magnetic resonance, Fourier transform infrared spectroscopy, UV/Vis spectroscopy, and gas adsorption isotherms.
· Formation of transparent thin films from nanocrystalline NaY.
· Characterization of nanocrystalline thin films using SEM, atomic force microscopy (AFM), and UV/Vis spectroscopy.
· Synthesis of ZSM-5 zeolites using confined space synthetic methods.
· Design, fabrication, and testing of a gas flow reactor for temperature programmed desorption and flow reactor studies.
· A study of cyclohexane and cyclohexene photooxidation reactions in zeolite Y as an environmentally benign method for producing selective partial oxidation products.
Nanocrystalline NaY was synthesized, and transparent films were prepared from the nanocrystalline material. The nanocrystalline NaY was characterized by a variety of methods, including powder x-ray diffraction, SEM, solid state nuclear magnetic resonance, Fourier-transform infrared spectroscopy, UV/Vis spectroscopy, and gas adsorption isotherms. The average particle size of the nanocrystalline NaY from SEM was determined to be 46 ± 8 nm. Films of NaY were prepared by sonication of an aqueous mixture of nanocrystalline NaY for several hours. The resulting hydrosol was placed onto a pyrex slide and dried in ambient air. Films of commercial NaY (Aldrich) were prepared using the same method. The film prepared from the nanocrystalline NaY hydrosol is much more uniform than the film prepared from the Aldrich NaY hydrosol. The increased transparency of the films can be visually observed and can be obtained more quantitatively by measuring percent transmittance using UV/Vis spectroscopy. The nanocrystalline NaY film had a percent transmittance of 70-80 percent in the 300-700 nm range compared to a percent transmittance of 30-40 percent for the Aldrich NaY film in the same range. In addition, the photooxidation of cyclohexane and cyclohexene on Y zeolites was investigated. The roles of the wavelength, reactant, and reductant were examined. The next phase of the project will involve applications of these nanocrystalline zeolites as environmental catalysts.
Future activities will focus on the synthesis of zeolites with systematically varied particle sizes so that the size-dependent properties of the zeolites can be examined by various spectroscopic and physicochemical techniques. Methods to monitor the zeolite nucleation and crystal growth processes in situ will be developed. Once the nanocrystalline zeolites have been synthesized and thoroughly characterized, reactivity studies will be undertaken to evaluate the activity of the nanocrystalline zeolites as environmental catalysts. In the first application, the partial oxidation of hydrocarbons will be examined. A major motivation for the development of new oxidation routes is the desire to achieve high selectivities at high conversions. These factors combined with the emphasis on cleaner and safer processes provides the context for the proposed studies. In the second example, the selective catalytic reduction of NOx and N2O by hydrocarbons (SCR-HC) over transition-metal exchanged zeolites will be investigated using the nanocrystalline zeolites. The emission of NOx and N2O from stationary and automotive sources, such as power plants and lean-burn engines, is a major environmental pollution issue. NOx leads to the production of ground-level ozone and acid rain, and N2O is a greenhouse gas. The activity of the nanocrystalline zeolites for NOx decomposition and SCR-HC will be evaluated.
Journal Articles on this Report : 1 Displayed | Download in RIS Format
|Other project views:||All 47 publications||16 publications in selected types||All 11 journal articles|
||Li G, Xu M, Larsen SC, Grassian VH. Photooxidation of cyclohexane and cyclohexene in bay. Journal of Molecular Catalysis A: Chemical 2003;194(1-2):169-180.||