2003 Progress Report: Synthesis, Characterization, and Catalytic Studies of Transition Metal Carbide Nanoparticles as Environmental NanocatalystsEPA Grant Number: R829624
Title: Synthesis, Characterization, and Catalytic Studies of Transition Metal Carbide Nanoparticles as Environmental Nanocatalysts
Investigators: Shah, S. Ismat , Chen, Jingguang G.
Institution: University of Delaware
EPA Project Officer: Hahn, Intaek
Project Period: March 1, 2002 through February 28, 2006 (Extended to February 28, 2007)
Project Period Covered by this Report: March 1, 2003 through February 28, 2004
Project Amount: $350,000
RFA: Exploratory Research: Nanotechnology (2001) RFA Text | Recipients Lists
Research Category: Nanotechnology , Safer Chemicals
The objective of this research project is to explore the possibility of using alternative catalytic materials, transition metal carbides, and oxycarbides (defined as oxygen-modified carbides) to replace platinum (Pt)-group metals for the reduction of NOx.
Result 1: Extended X-Ray Absorption Fine Structure (EXAFS) Studies of the Nanoparticles
|EXAFS analysis shows the nearest neighbor coordination in materials. For our work, these studies are important because in light of result 1, WC (Tungsten Carbide) surfaces have catalytic behavior for NO decomposition similar to that of Pt. If we observe the same electronic structure and local chemistry in the WC nanoparticles as we do in the bulk, we can correlate their catalytic properties. Previously, we reported that the synthesis process can be modified to obtain desired surfaces. EXAFS is used to compare the local chemistry of the nanoparticles with that of bulk surfaces. Figure 1a shows the comparison of the W K-edge (the absorption edge of Tungsten) oscillation for the nanoparticle film, with spectra from the bulk and theory. Figure 1b shows the edge oscillations of the nanoparticles and the bulk only. The similarity of the structure is readily observable, indicating that the local chemistry of the nanoparticles is similar to that of the bulk, and therefore we should expect the catalytic properties of the nanoparticles to be similar to that of the bulk.|
|Figure 1. EXAFS Results Comparing the Nanoparticles, Bulk and Theoretical Spectra|
Result 2: NOx Decomposition With WCx Nanoparticles
Preliminary experiments to study NOx decomposition with WCx nanoparticles were conducted in an inline reactor. The reactor setup is shown in Fig. 2. The temperature of the reactor can be varied from room temperature to 1,000°C. Currently, we are using only a nitrogen column in the gas chromatographer (GC). This soon will be expanded to include a NO column. A mixture of 1 percent NO with He is used as the test gas. Flow rates are adjusted using mass flow controllers.
Figure. 2: In line reactor for NOx decomposition studies.
A baseline for the experiment is obtained by passing the gas mixture through the reactor, without any catalyst. The baseline is shown in Fig. 3. With the addition of the catalyst, the direct decomposition of NOx occurs according to the reaction:
NOx ® N2 + O2
|Figure 3. NOx Decomposition With and
Without the Catalyst
We will: (1) use reactive gas condensation with laser ablation for the synthesis of WCx nanoparticles, (2) study the addition of oxygen towards the stability of the WCx nanoparticles, (3) conduct de-NOx catalysis experiments with the addition of hydrocarbons to the feed gas, and (4) expand the catalysis studies to include the oxidation of hydrocarbon.
Journal Articles on this Report : 2 Displayed | Download in RIS Format
|Other project views:||All 16 publications||3 publications in selected types||All 3 journal articles|
||Chen JG, Zhang MH, Rumaiz A, Shah SI. A comparative investigation of the self-hydrogenation and hydrogenation of cyclohexene. Catalysis (submitted, 2004).||
||Zhang MH, Hwu HH, Buelow MT, Chen JG, Ballinger TH, Andersen PJ, Mullins DR. Decomposition pathways of NO on carbide and oxycarbide-modified W(1 1 1) surfaces. Surface Science 2003;522(1-3):112-124.||