Project Research Results
Grantee Research Project Results
Final Report: Environmentally Benign Photo-Assisted Catalysis Selective Oxidation Reactions in ZeolitesEPA Grant Number: R825304
Title: Environmentally Benign Photo-Assisted Catalysis Selective Oxidation Reactions in Zeolites
Investigators: Larsen, Sarah C. , Grassian, Vicki H.
Institution: University of Iowa
EPA Project Officer: Karn, Barbara
Project Period: October 1, 1996 through September 30, 1999
Project Amount: $260,228
RFA: Technology for a Sustainable Environment (1996)
Research Category: Nanotechnology , Pollution Prevention/Sustainable Development
The focus of this project was to develop photooxidation in zeolites as an environmentally benign alternative to conventional liquid phase oxidation of industrially important chemicals. Developing green methodology for the catalytic syntheses of industrially important chemicals is necessary if the production of hazardous waste is to be reduced. Our approach to this problem is unique in that it combines several key aspects to eliminating waste. First, the reactions that are considered are all done in the gas phase, thereby eliminating the use of organic solvents. Second, sunlight can be used to initiate the reaction for selective oxidation; therefore, the method has the potential to be energy efficient. Third, zeolites, long exploited in industry, are used as reaction vessels to both control the initial selective oxidation reaction and for further selective steps in synthesis of industrially important chemicals.
The overall objectives of this project were:
- To extend these unique, recently discovered photooxidation reactions in zeolites to other systems.
- To determine the chemical and geometric properties of the zeolite that control the product selectivity.
- To develop a strategy for the environmentally benign catalytic synthesis of
industrially important molecules. The types of reactions proposed here are:
butene ?> butyraldehyde
p-xylene ?> terephthalic acid
hexane ?> adipic acid
- To begin catalytic studies on the systems described here using a photocatalytic reactor.
One of the most important applications of homogeneous catalysis is the oxidation of hydrocarbons to produce industrially important chemicals, such as terephthalic acid and adipic acid, which are used in the production of polymers. Oxidation by O2 with homogeneous catalysts exhibits very low selectivity because side reactions are difficult to control and intermediates are often more easily oxidized than the parent under thermal conditions. The problem with autooxidation is that it is slow and nonselective. One challenge is to find new, more efficient catalysts for the conversion of hydrocarbons into oxygenates. A second challenge is to develop processes that have a minimal environmental impact.
Several years ago, Frei and coworkers demonstrated that hydrocarbons in zeolite Y can be selectively oxidized by visible light. The use of visible, rather than ultraviolet irradiation, allows access to this low energy pathway, eliminates many secondary photo-processes, and leads to the remarkable selectivity. The geometric constraints of the zeolite framework also are important to the selectivity. The implications of this methodology for environmentally benign synthesis of chemicals are twofold. The increased selectivity of the oxidation reaction will decrease the production of unwanted side products. In addition, a zeolite catalyst and gas phase reactants and products will eliminate use of expensive and environmentally toxic solvents.
During the grant period, our research was focused on identifying the factors that control selectivity in these hydrocarbon photooxidation reactions in zeolites. Specifically, it was our interest to extend these recently discovered, highly selective photooxidation reactions in zeolite Y to other systems, to determine the chemical and structural properties of the zeolite that control product selectivity, and to develop a strategy for the environmentally benign catalytic synthesis of industrially important molecules. The major accomplishments of this work include:
- Examined the role of zeolite structure and properties in zeolite hydrocarbon photooxidation reactions
- Investigated the effect of the parent zeolite, temperature, and excitation wavelength on the photooxidation products
- Identified several new reactions in cation-exchanged zeolites
- Evaluated electric field requirements for these reactions and determined how these change with different zeolites
- Assigned electric field values to cation and acid sites using the vibrational frequency of CO
- Computed the vibrational frequencies of CO in model CO-zeolite complexes
- Studied the photooxidation of toluene, p-xylene, and 1-alkenes in a variety of cation-exchanged zeolites including NaX, BaX, NaY, CaY, BaY, BaHY, BaBeta, NaZSM-5 and BaZSM-5
- Applied in situ FTIR and ex situ NMR, GC and GC/MS for detailed product analysis.
Many of these accomplishments are discussed in detail in the publications listed below.
Journal Articles on this Report : 5 Displayed | Download in RIS Format
|Other project views:||All 13 publications||6 publications in selected types||All 5 journal articles|
|| Li P, Xiang Y, Grassian VH, Larsen SC. CO adsorption as a probe of acid sites and the electric field in alkaline earth exchanged zeolite beta using FT-IR and ab initio quantum calculations. Journal of Physical Chemistry B 1999;103(24):5058-5062
|| Myli KB, Larsen SC, Grassian VH. Selective photooxidation reactions in zeolites X, Y and ZSM-5. Catalysis Letters 1997;48(3--4):199-202
||Panov AG, Larsen RG, Totah NI, Larsen SC, Grassian VH. Photooxidation of toluene and p-xylene in cation-exchanged zeolites X, Y, ZSM-5, and beta: The role of zeolite physicochemical properties in product yield and selectivity. Journal of Physical Chemistry B 2000;104(24):5706-5714.||
||Panov AG, Myli KB, Xiang Y, Grassian VH, Larsen SC. Photooxidation of toluene in cation-exchanged zeolites. Green Chemical Syntheses and Processes, ACS Symposium Series767. Anastas, P.T; Heine, L.G.; and Williamson, T.C. ed.; American Chemical Society 2000: 206-216.||
|| Xiang Y, Larsen SC, Grassian VH. Photooxidation of 1-alkenes in zeolites: A study of the factors that influence product selectivity and formation. Journal of the American Chemical Society 1999;121(21):5063-5072
pollution prevention, green chemistry, clean technologies, innovative technology, waste reduction, waste minimization, environmentally conscious manufacturing, environmental chemistry., RFA, Scientific Discipline, Sustainable Industry/Business, cleaner production/pollution prevention, Environmental Chemistry, Sustainable Environment, Technology for Sustainable Environment, Environmental Engineering, in-process changes, cleaner production, oxidation reactions, zeolites, environmentally conscious manufacturing, oxidation, photoreactor, alternative materials, catalysts, photochemical alternatives, photo-assisted catalysis, hazardous waste, industrial process, process modification, innovative technology, industrial innovations, pollution prevention, alternative chemical synthesis
Progress and Final Reports: