One of the major environmental problems of our time is the presence of nitrous oxide (NO) as an exhaust gas from automobiles. The primary goal of this research is to determine the quantum mechanism that aids the conversion of NO through the use of naturally found zeolite called Cu-ZMS-5 and small quantities of ammonia (NH₃). During the conversion process, the effectiveness of zeolite is degraded. During the experiments performed at the Ford Motor Company without NH₃, it is found that the catalyst zeolite needs to be frequently replaced. Rate equation analysis based on energy principles will be used to determine the mechanism, which makes ZMS-5 effective. Decomposition of NO to nitrogen is a very active topic of current research especially at Shell Chemicals and California Institute of Technology.

One of the primary goals of this research is to numerically produce the general trends as observed by experimental studies carried by Iwamoto, specifically look at the gas concentration as a function of time and temperature. These results will also be compared with other preliminary calculations previously made at ASU.

Zeolites are alkaline-earth metals hydrated aluminosilicates (Virta, 1998). Zeolites are porous silicate and aluminum atoms. A zeolite synthesized as ZMS-5 is of special interest. This zeolite has unique ion-exchange and catalytic properties. This is a natural zeolite, and there are deposits in Arizona among other states. ZMS-5 consists of a unit cell of 288 atoms of silicon (Si), aluminum (Al), and copper (Cu) (Goodman 1998).

A substantial amount of research is being done using zeolites as catalysts for NO_x reduction. Researchers at Shell Chemicals have developed a method by using sonic vibrations to create thin zeolite sheets. Tests have demonstrated that zeolite sheets are more efficient than conventional zeolite catalyst (Chemical Week, 1998). Researchers at the California Institute of Technology have developed a method of incorporating organic molecules into the zeolite beta structure (2-phenyethyl-trimethoxysilane). This acts as a superior catalyst for conversion of NO into N₂.

One of the major environmental problems of our current time is the presence of nitrous oxide (NO) as an exhaust gas from automobiles. Decomposition of NO to nitrogen is a hot topic of research. The proposed research examines the impact of zeolite catalysts at an atomic level for the conversion process. Recently, it is found that the use of a minor quantity of ammonia (NH₃) greatly facilitates this conversion process (Hoelderich, 1998).

This study is primarily focused on trying to answer the question: what is the mechanism that aids the conversion of NO through the use of the catalyst Cu-ZMS-5 and ammonia (NH₃).

We will use a rate equation analysis to understand qualitatively the conversion process from NO to nitrogen. Experimental observations from the Ford Motor Company will be used to validate theoretical and computational models.

Nitrogen oxide causes photochemical smog and acid rain. Copper exchange zeolite decomposes nitrous oxide into elemental nitrogen. Reference 1 surveys the diffusion mechanism through the zeolite pores. Copper exchanged zeolite acts as a catalyst. The active site contains zeolite bound copper ions in the form of Z^--Cu(Ion) or

The most important point is the absorption mechanism of NO into ZCu. Schneider et al indicates that direct spectroscopic evidence of the bonding of ZCu to O₂ remains lacking.

ZCu and ZCuO form ZCuNO, ZCuO₂N, and ZCuNO₃. These molecules are stable at ambient temperature, but at higher temperature they release nitrogen. Figure 9 of the referenced article summarizes all the reaction schemes of ZCuONO.

Fundamental equations for the flow of gas are provided. This is a differential equation that needs to be solved using numerical methods. Certain physical constants are needed. It is assumed that we are operating at standard atmospheric pressure, and the velocity of the gas is not at the supercritical stage.

Considerable research is in progress to clearly understand the bonding behavior between gases and solid adsorbents. Basically, there are two types of adsorption called physisorbed where a molecule is adsorbed without undergoing significant change in electronic structure and chemisorbed where the molecules’s electronic structure is significantly changed. Energies for chemisorption are typically eight to ten times higher than required for physisorption.

Hayward and Trapnell prepared a reactivity table for a series of gases with metals. For a reaction between copper and nitrogen, they gave a number of 2. Among all the metals in the periodic table, copper seems to be the only metal which adsorbs nitrogen.

Zeolites are aluminas/silicas with strong Brønsted and Lewis acid sites acting as hard centers. Zeolites interact strongly with both hard acids and bases. Electronegativity and the hardness of the surface of a zeolite are important properties. Zeolites can be doped with acids to change the average electronegativity.

According to the density functional theory based on quantum mechanical methods and Taylor series expansion for n_a, the following equation can be used essentially to yield an exact result for adsoprtion.

Wilber and Boehman have presented a numerical modeling of the reduction of nitric oxide by using ethylene and Cu-ZSM-5. These copper zeolites act as catalysts in the decomposition of NO. Newton-Raphson techniques have been used. Experimental data has been used to adjust kinetic parameters for the reduction of NO. The paper examines different test velocities as well as the se of ethylene and benzene as reductants.

Newton-Raphson method consists of taking the slope of the curve …

Christopher Cummins at MIT has been able to find a way to break the extremely strong triple bond of a nitrogen molecule at room temperature and pressure. This could lead a way to better utilize di-nitrogen oxide (N₂O) in various manufacturing processes.

A team of chemists has been able to design a new class of material that can be used at catalysts. These catalysts are designed to handle particularly large molecules. The new material formed from zinc-oxide. This metal-organic framework material has many of the functional capabilities of zeolites which is a porous material used as catalysts in conversion of NO into N₂. Zinc oxide is used with the terephthalic acid, an organic compound, to form a molecular sieve. This new material has a double bond linking the organic acid to zinc oxide which is exceptionally stable. According to Michael O’Keefe, this is the first metal-organic material which is stable. This molecular sieve can handle quite large molecules and retains its integrity at temperatures up to 300 degrees centigrade.

Adams et al (1996) have examined the influence of velocity on the behavior of CuZSM-5. Activation energy related to NO reduction by C₃H₆ shows some agreement for the activation energy of C₃H₆ oxidation reaction.

The development of rate equation model includes prediction of concentration of different gases having different gas properties and reaction rates. Initially, the activation energy needs to be calculated and estimation of adsorption and de-adsorption rates have to be made with an estimate of capture radius for the Cu molecule in the Zeolite pore. Computer program will look at the molecular dynamics along with the calculations of enthalpy and entralpy. Molecular dynamics will consider ionic state and the existence of dipole. Specifically, it would simulate diffusivity of gas within the Zeolite pore. There is very little which has been done on the simulation of molecular dynamics, therefore a literature search would be performed. In this study, the reactivity of Zeolite molecules with the Zeolite pore will also be considered.

Adams, J. B., Rockett, Angus, Kieffer, John, Wei, Xu, Nomura, Miki, Kilian, Karland A., Richards, David F., and Ramprasad, R., "Atomic-level Computer Simulation," Journal of Nuclear Materials, Volume 216, pp 265-274, Elsevier: 1994.

Adams, K.M., Cavatajo, J.V., Hammerle, R.H., Applied Catalysis B, 10 (1996) 157-181.

B.R. Goodman, W.F. Schneider, K.C. Hass, and J.B. Adams, "Theoretical Analysis of Oxygen-bridged Cu pairs in Cu-exchanged Zeolites," Catalysis Letter 56(4), (1998) 183-188.

Chemical Week, Shell Develops Open-Pore Zeolite Sheets. Volume 160, #43, November 11, 1998, page 23.

Goodman, B. R., Hass, K. C., Schneider, W.F., and Adams, J.B., "Cluster Model Studies of Oxygen-Bridged Cu Pairs in Cu-ZSM-5 Catalysts," Submission to the Journal of Physical Chemistry B, pp 1-26, 1999.

Hass, K.C., and Schneider, W. F., "Density Functional Studies of Adsorbates in Cu-Exchanged Zeolites: Model Comparisons and SO_x Binding," submission to Journal of Chemical Society, Faraday Transaction, pp 1-30, 1999.

Hayward, D. O., B. M. W. Trapnell, Chemisorption, Butterworths (1964).

Heimrich, Society of Automotive Engineers, Paper no. 970755 (1997).

Hoelderich, W.F. and Heinz, D., 1998, Research and Development of Zeolite Catalysis in the 80s and in the 90s as well as Forthcoming Trends: Research on Chemical Intermediates, v. 24, no. 3, March, p. 337-345.

Iwamoto, M.; Hamada, H. Catal. Today 1991, 10, 57.

Iwamoto, Masakazum, "Copper Ion-exchanges Zeolites as Active Catalysts for Direct Decomposition of Nitrogen Monoxide," Chemistry of Microporous Crystals, Proceeding of the International Symposium on Chemistry of Microporous Crystals, Tokyo, Studies in Surface Science and Catalysis, B. Delmon and J. T. Yates, Volume 60, pp 327-334, Elsevier, New York, pp 327-334, 1991.

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Ramprasad, R., Hass, K.C., Schneider, W.F., and Adams, J.B., "Cu-Dinitrosyl Species in Zeolites: A Density Functional Molecular Cluster Study," Journal of Physical Chemistry B, Volume 101, Number 35, pp 6903-6913, 1997.

Ramprasad, R., Schneider, W. F., Hass, K. C., and Adams, J.B., "Theoretical Study of CO and NO Vibrational Frequencies in Cu-Water Clusters and Implications for Cu-Exchanged Zeolites," Journal of Physical Chemistry B, Volume 101, Number 11, pp 1940-1949, 1997.

Robert L Virta, Zeolites in Sedimentary Rocks, United States Mineral Resources, U.S. Geological Survey Professional Paper #820, 1998.

Schneider, W. F., Hass, K.C, Ramprasad, R., Adams, J.B.; Density Functional Theory Study of Transformations of Nitrogen Oxides Catalyzed by Cu-Exchanged Zeolites; Journal of Physical Chemistry B, Vol. 102, Num. 19, pp 3692 – 3705.

Schneider, W.F., Hass, K. C., Ramprasad, R., and Adams, J. B., "Cluster Models of Cu Binding and CO and NO Adsorption in Cu-Exchanged Zeolites," Journal of Physical Chemistry, Volume 100, Number 15, pp 6032-6046, 1996.

Schneider, W.F., Hass, K. C., Ramprasad, R., and Adams, J. B., "First-Principles Analysis of Elementary Steps in the Catalytic Decomposition of NO by Cu-Exchanged Zeolites," Journal of Physical Chemistry B, Volume 101, Number 22, pp 4353-4357, 1997.

Sengupta, D., Adams, J. B., Schneider, W. F., and Hass, K. C., "Theoretical Analysis of N₂O to N₂ Conversion During the Catalytic Decomposition of NO by Cu-zeolites," to be published, pp 1-15, 1999.

Sengupta, D., Schneider, W. F., Hass, K. C., and Adams, J.B., "CO Oxidation Catalyzed by Cu-exchanged Zeolites: A Density Functional Theory Study," Catalysis Letters, pp 1-16, 1999.

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Wilber, Ronald A., Boehman, André L., "Numerical Modeling of the Reduction of Nitric Oxide by Ethylene Over Cu-ZSM-5 Under Lean Conditions," Catalysis Today, Volume 50, pp 125-132, 1999.