Gas Phase Kinetics Data and Databases What Information is Needed and How to Use it.

1. Gas Phase Kinetics Data and Databases What Information is Needed and How to Use it. Jeffrey A. Manion National Institute of Standards and Technology Physical and Chemical Properties Division Gaithersburg MD 20899 Workshop on Constructing a Kinetics Database NIST, Gaithersburg, MD April 19, 2004

2. Structure of Talk PART 1: Overview of gas phase kinetic data PART 2: Application of gas phase databases: Combustion Chemistry: What are the data needs NIST Real Fuels Project: Vision of how to implement change

3. Who Uses Databases and How? • Who uses the data? • Experts within community • People from other disciplines • How is the data to be used? • Archival: Storage of results for rapid retrieval • a. Numerical results; sometimes evaluation • b. Adequate specification of the conditions • c. Bibliographic information • Use Oriented: Focus is application and extension of the data • a. All of the above, plus: • b. Information to establish intrinsic relationships • c. Information to enable additional processing

4. What is Meant by Kinetic Data? Chemical Reaction:A chemical reaction is a process that results in the interconversion of chemical species. A → B A + B → C + D Chemical Kinetics: The study of the rates of chemical reactions. -dA/dt = k1[A] -dA/dt = k2[A]a[B]b BUT: Do mechanical engineers, biochemists, and combustion chemists mean the same thing by “kinetic data” and expect the same things in a kinetics database?

5. What do People Actually Mean? From a March 2004 e-mail: Dear Dr. Manion: I am working to improve the production of methylene chloride. The reaction is: CH4 + 2 HCl + 02 → CH2Cl2 + 2 H20 I was unable to find the kinetic data for the above reaction in the NIST Gas Phase Kinetics Database. Can you help me in this regard? Not everyone distinguishes between global and elementary reactions.

6. Gas Phase Kinetic Data - Definitions Elementary Reaction (IUPAC): An algebraic representation of a chemical transforma-tion for which no reaction intermediates have been detected or need to be postulated to describe the chemical reaction on a molecular scale. An elementary reaction is assumed to occur in a single step and to pass through a single transition state. CH4 + OH → [CH3 - H - OH]‡→ CH3 + H2O transferrable Lumped Reaction: A collection of (a small number) of elementary reactions expressed as an “equivalent” apparent single-step reaction. transferrable under specified conditions Global Reaction: A collection of (a large number) of elementary reactions expressed as an apparent single-step reaction. CH4 + 2 O2→ CO2 + 2 H2O Not transferrable

7. Kinetic Data for Gas Phase – Issues and Non-Issues In many respects, reactions in the gas phase are easiest to describe. • Generally Non-Issues in Gas Phase Kinetics: • Solvent, cage effects • Catalytic processes (heterogeneous) • Ions and ionic processes (thermal systems – but not true for plasmas!) • Complications: • Pressure effects (non-Boltzmann energy distributions): • Description of “Fall-off” behavior for unimolecular processes • Chemical activation processes • Multi-channel reactions • Role of theory and calculated data? • Real-world process modeling applications may have additional complexity (gas-surface reactions, photolytic reactions, etc.)

8. Part 2:Application of Gas Phase Kinetics Databases

9. Process Chemistry: • Semiconductors • Base Chemicals • Waste Streams • Combustion Chemistry: • Energy Production (NIST Real Fuels Program) • Waste Incineration Major Problems Needing Gas Phase Kinetic Data Scales Range from Corporate Needs to National to World Encompassing • Atmospheric Chemistry: • Troposphere • Stratosphere

10. Common Threads: Ultimate goal is the application of chemical kinetics to realistically simulate a complex system for predictive purposes. Databases should be designed to support the application of the data

11. A Closer Look at Combustion

12. Liquid Fuels Year 2000 731 Billion Liters $272 Billion Diesel Jet Gasoline Energy Production for Transportation - National Impacts * • Monetary Importance: • Economic Competitiveness • Energy Self-Sufficiency • Green House Gas Trading Credits • Healthcare costs • Quality of Life (Pollution Effects): • Heart/Lung Disease • Environmental Degradation • Global Warming • Premature death *“Statistics for Industry Groups and Industries: 2000”, Publication M00(AS)-1, U.S. Census Bureau, Economics and Statistics Administration, U.S. Department of Commerce, 2002.

13. Better Combustion: What’s the Monetary Value to the Nation? Annual Net Value of Improved Fuel Efficiency and Reduced Pollution PM2.5 PM10 NOX SO2 Adv. Eng. Tech. * ** * “The Benefits and Costs of the Clean Air Act 1990 to 2010: EPA Report to Congress”, Table ES-1 (EPA central value converted to year 2000 dollars), EPA-410-R-99-001, U.S.EPA, 1999. ** Based on annual liquid transportation fuel cost of $272 B in the year 2000 (Energy Information Administration) and minimum estimate of 15% improved fuel efficiency increase for advanced combustion technologies such as HCCI.

14. Device Simulation & Design $ $ $ Vision: The Application of Kinetics Databases to Combustion Too Large for CFD Kinetic Data (Databases) Chemical Kinetic Model Thermodynamic Data (K = kf/kr) Refined Chemical Kinetic Model Experimental Observations Reduced Chemical Kinetic Model + Physical Properties Boundary Conditions Computational Fluid Dynamics (CFD) Code CFD Code

15. Model 1 1800 Reactions 260 Species Model 2 2200 Reactions 220 Species Current Situation with Combustion Modeling Situation: An applications engineer (non-expert kineticist) goes to the literature and is lucky to find two models of a reacting system. Great, except: • Reaction sets are different • Rate constants are different • Thermodynamic sets are different • Species are identified by different strings (understandable only to creator) • Data often not traceable – no reference or reference is not original source • No common validation experiments Dilemma: How do you choose? How do you begin to compare, to improve? How much TIME will it take?

16. NIST Real Fuels Project: A Vision for the Future?

17. Match Physical & Chemical Properties Real Fuels Complex Mixtures (100’s compounds but few classes) Surrogate Fuels Small # compounds representing chemical classes NIST Real Fuels Program - Concept NIST “Real Fuels” Program: A collaborative effort designed to enable the combustion of liquid transportation fuels (diesel, gasoline, aviation) to be realistically simulated for device design purposes. Build Community Experimental and Kinetic Model Development Efforts Realistic Device Simulation Workshop on Combustion Simulation Databases for Real Transportation Fuels, National Institute of Standards and Technology, Gaithersburg, MD, September 4-5, 2003.

18. Components of NIST Real Fuels Project • Experimental: • Surrogate fuels concept • Experiments to fill knowledge gaps • Infrastructural: • Design intelligent data structures for combustion information • Create web-accessible data warehouse for combustion modeling • Promote collaborative paradigm for development of chemical kinetic models of combustion systems • Won’t solve all problems, but can: • take key steps • lay the foundation for systematic progress

19. Partnering: NIST – PrIMe – CMCS Collaboration Collaboratory for Multi-scale Chemical Science (CMCS): DOE funded computerscience project whose goal is to to enhance chemical science research by developing an adaptive informatics infrastructure. Larry Rahn, Sandia - CMCS.org Process Informatics Model effort(PrIMe): A community effort to develop predictive reaction models for combustion. The goal is to convert model building into a science, automate the methodology, and provide the results to the User in a prompt and convenient format. (Outgrowth of GRI-Mech) Michael Frenklach - UCB

20. Chemical Kinetic Model Refined Chemical Kinetic Model Kinetic Data (Databases) Tools Tools Tools Thermodynamic Data (K = kf/kr) Experimental Observations Reduced Chemical Kinetic Model • PrIMe Process (Vision): • Community-based evaluation of Warehouse Data “Best” values • Selected set of “Best” validation experiments for combustion models • Set of Community Tools for “on-the fly” generation of “Best Current Kinetic Model” NIST – PrIMe – CMCS Collaboration Tools • NIST PrIMe Data Warehouse: • All kinetic data on elementary reactions relevant to combustion (NIST Gas Kinetics, GRI Mech) • Relevant thermodynamic data • Inclusion of global kinetic data for model validation? CMCS: Implementation of Computer Science Infrastructure.

21. Take Home Message Rapid access to gas phase kinetic information is nice – but terribly insufficient. • Value of gas phase kinetic information is in the aggregate content. • Value is greatly diminished in the absence of infrastructure to efficiently process and share large amounts of data. • Need is ability to (rapidly) validate and apply traceable information to problems and then analyze and refine the results. Databases should be designed to support the use of the data.

22. Automated Molecule Classification Mol File atom/connectivity information Designing Data Structures to Enable Automation Example: How does one identify a molecule in the database? Choice 1: A CAS number or some other “meaningless” string • Unique identifier, but establishes no relationships between data Better: Choice 2: Include a structural representation relatable to chemical information • e.g. mol file or similar Enables SARs for Molecules & Rxns “Expert Systems” Development for: • Data estimation • Data evaluation • Automated uncertainty estimates • Automated mech. generation See Posters by Don Burgess & Dave Matheu

23. Final Comments and a Question • Gas Phase Chemical Kinetic Data is incredibly important to solving a variety of National Problems • Intelligently designed databases and appropriate cyberinfrastructure and knowledge management tools are incredibly important. • Scientists need to develop new paradigms for working together. • Funding agencies need to recognize and support these efforts. • Is Gas Phase Database Model Applicable to Other Types of Kinetic Data?