DOCSLIB.ORG

Mediated Ammonia Synthesis from N2 and H2 at Ambient Temperature

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Mediated Ammonia Synthesis from N2 and H2 at Ambient Temperature Ta +-mediated ammonia synthesis from N and H at 2 2 2 INAUGURAL ARTICLE ambient temperature Caiyun Genga, Jilai Lia,b,1, Thomas Weiskea, and Helmut Schwarza,1 aInstitut für Chemie, Technische Universität Berlin, 10623 Berlin, Germany; and bInstitute of Theoretical Chemistry, Jilin University, Changchun 130023, People’s Republic of China This contribution is part of the special series of Inaugural Articles by members of the National Academy of Sciences elected in 2018. Contributed by Helmut Schwarz, September 20, 2018 (sent for review August 24, 2018; reviewed by R. Graham Cooks and Markus Reiher) + In a full catalytic cycle, bare Ta2 in the highly diluted gas phase is oriented external electric fields (53, 54) followed by insertion of, able to mediate the formation of ammonia in a Haber–Bosch-like for example, a nitrogen atom in the C–C bonds of alkanes has process starting from N2 and H2 at ambient temperature. This find- been reported as well (55, 56). Another promising approach is ing is the result of extensive quantum chemical calculations sup- based on the electrochemical cleavage of N2 to produce ammonia ported by experiments using Fourier transform ion cyclotron (11, 31, 32, 51, 57–60). There are indications that the cooperative + resonance MS. The planar Ta N , consisting of a four-membered 2 2 activation of N2 by several transition metal atoms holds promise ring of alternating Ta and N atoms, proved to be a key intermedi- as well (28, 34–39, 45, 61–64). Furthermore, the reactivity of ate. It is formed in a highly exothermic process either by the re- μ = + ditantalum complexes of the type ([NPN]Ta( -H))2N2 ([NPN] action of Ta2 with N2 from the educt side or with two molecules + PhP(CH2SiMe2NPh)2) with dinitrogen (65) has also been ex- of NH3 from the product side. In the thermal reaction of Ta2 with tensively investigated in the past (28, 34, 61–71). ≡ N2, the N N triple bond of dinitrogen is entirely broken. A detailed Mechanistically, the catalytic activity of the transition metals is analysis of the frontier orbitals involved in the rate-determining based on the interplay of vacant and filled d-orbitals during step shows that this unexpected reaction is accomplished by the multielectron rearrangements along the reaction coordinate. interplay of vacant and doubly occupied d-orbitals, which serve as Here, the vacant orbitals of the metal center receive electrons CHEMISTRY both electron acceptors and electron donors during the cleavage from N and simultaneously weaken (or cleave) the triple bond of the triple bond of N≡N by the ditantalum center. The ability of 2 + of dinitrogen by donating electron density from the filled d-orbitals Ta2 to serve as a multipurpose tool is further shown by splitting into the antibonding π*-orbitals of N2 (49, 50). According to the the single bond of H2 in a less exothermic reaction as well. The insight into the microscopic mechanisms obtained may provide conceptual framework outlined by Fryzuk and coworkers (67), it guidance for the rational design of polymetallic catalysts to bring was recognized that the ability of Ta compounds to store two – about ammonia formation by the activation of molecular nitrogen electrons in a Ta Ta bond is a prerequisite for subsequent re- and hydrogen at ambient conditions. ductive transformations and is of paramount importance to split the N≡N triple bond completely. gas-phase catalysis | ammonia synthesis | dinitrogen activation | While the impressive progress made in recent decades is un- hydrogen activation | quantum chemical calculation deniable, a deep and comprehensive understanding of the vari- ous mechanistic details related to either fixation or activation of he direct use of molecular nitrogen with its thermodynami- N2 to ammonia is far from being complete. This also applies to a Tcally stable and kinetically inert triple bond as one of the very consistent description of the elementary steps involved, with the few commodities that are freely available worldwide and in al- most unlimited quantities is essential for life on Earth (1–3). Significance Nature utilizes nitrogen-binding enzymes, the nitrogenases, to catalyze the conversion of nitrogen to ammonia at ambient A combined experimental/computational approach provides conditions (4, 5). In contrast, its industrial production still relies deep mechanistic insight into an unprecedented cluster- on the highly energy-demanding Haber–Bosch process to bring mediated N−H coupling mimicking the industrially extremely important ammonia synthesis from N and H (the “Haber– about the challenging chemical marriage of N2 and H2 to form 2 2 Bosch” process) at room temperature. Crucial steps were NH3 (3, 6–8), which consumes ca. 1–2% of the world’s energy – identified for both the forward reactions (i.e., the activation of production (8 11). In addition, presently about 1.5 tons of the + greenhouse gas carbon dioxide are produced per ton of ammonia N2) and the backward process (i.e., the Ta2 -mediated de- composition of NH3). The central intermediate for either path (9). To slow down global warming (12), it would, therefore, be + corresponds to Ta2N2 , a four-membered ring with alternating sensible, in addition to numerous other measures, to find a ’ process for producing ammonia on an industrial scale from the Ta and N atoms. The root cause of tantalum s ability to bring about nitrogen fixation and its coupling with H under mild molecular feedstock nitrogen and hydrogen in an economically 2 conditions has been identified by state-of-the-art quantum viable and environmentally benign way. chemical calculations. The greatest obstacle to the production of ammonia from N2 ≡ corresponds to the cleavage of the N N triple bond, which with a Author contributions: J.L. and H.S. designed research; C.G. and J.L. performed research; −1 bond energy of 945 kJ mol (13), constitutes one of the stron- C.G., J.L. and T.W. analyzed data; and J.L., T.W. and H.S. wrote the paper. gest chemical bonds. While some progress has been made on the Reviewers: R.G.C., Purdue University; and M.R., Swiss Federal Institute of Technology. daunting road to artificial nitrogen activation, the number of The authors declare no conflict of interest. well-defined complexes that bind N2 and ultimately, lead to a Published under the PNAS license. ≡ complete cleavage of the N N triple bond is rather limited so 1To whom correspondence may be addressed. Email: [email protected] or helmut.schwarz@ far. For instance, complexes with single (14–32) and multiple tu-berlin.de. – – (15, 33 39) transition metal centers, small metal clusters (40 This article contains supporting information online at www.pnas.org/lookup/suppl/doi:10. 48), and also, main group compounds (49–52) have been found 1073/pnas.1814610115/-/DCSupplemental. to be able to split dinitrogen. The activation of N–N bonds by www.pnas.org/cgi/doi/10.1073/pnas.1814610 115 PNAS Latest Articles | 1of8 Downloaded by guest on September 27, 2021 + A A with Δm =+28 appears, which has been identified as Ta2N2 ABAr 14N2 15 (Eq. 1). By using isotope-labeled N2, signal C from Fig. 1B is C = Ta2N2+ shifted by two mass units on the mass scale and shows up as peak 15 + + + D C 2 A = Ta2 in Fig. 1 (Ta2 N2 ) (Eq. ). If Ta2 is exposed to a 1:1 + + B = Ta O+ 14 15 14 15 2 mixture of N2 and N2, signals for both Ta2 N2 and Ta2 N2 are observed, but there are none containing both nitrogen iso- 14 15 + 3 4 C topes Ta2 N N (Eqs. and ). Mass-selected and properly B 14 + 15 B thermalized Ta2 N2 ,whenexposedto N2, does not react fol- lowing one of the degenerate exchange reactions 3 and 4: 340 362 420 340 362 420 + + A A Ta2 + N2 → Ta2N2 [1] CD15N2 + + 15 → 15 + [2] D = Ta15N2+ Ta2 N2 Ta2 N2 14 + 15 15 + 14 Ta2 N2 + N2↛Ta2 N2 + N2 [3] D CD + B B 14 + 15 14 15 14 15 Ta2 N2 + N2↛Ta2 N N + N N. [4] 340 362 420 340 362 420 + The rate constant k(Ta2 /N2) for reaction 1 is estimated to − − − + 14 × 12 3 1 1 Fig. 1. Mass spectra for the thermal reactions of Ta2 with Ar (A), N2 (B), 5.1 10 cm molecule s ; this corresponds to a collision 15 14 15 × −7 N2 (C), and a 1:1 mixture of N2 and N2 (D) at a pressure of ca. 2.0 10 efficiency of ϕ = 0.8%. Owing to the uncertainty in the de- mbar after a reaction time of 2 s. All x axes are scaled in m/z, and the y axes termination of the absolute N2 pressure, an error of ±30% is are normalized relative ion abundances. associated with these measurements. In addition to the labeling experiments, the elementary compositions of the charged parti- cles have been confirmed by exact mass measurements. Since exception of the elegant elucidation of the mechanism of the 14N/15N kinetic isotope effects (KIEs) are expected to be quite Haber–Bosch process by Ertl and coworkers (7, 8, 72, 73). small (95) and as it was not possible to reproducibly adjust the As has been shown time and again, gas-phase experiments pressure in the ICR cell to the required accuracy to obtain mean- provide an ideal arena for tackling many challenging mechanistic ingful data, we have renounced the determination of the 14N/15N issues at a strictly molecular level, such as investigating the de- + KIE for the formation of Ta N . tailed course of chemical reactions, including those that are in- 2 2 The simplified 2D potential energy surface (PES) of the most dustrially relevant (74–88).
Load more

Recommended publications
  • Chemical Reactions Involve Energy Changes
    Page 1 of 6 KEY CONCEPT Chemical reactions involve energy changes. BEFORE, you learned NOW, you will learn • Bonds are broken and made • About the energy in chemical during chemical reactions bonds between atoms • Mass is conserved in all • Why some chemical reactions chemical reactions release energy • Chemical reactions are • Why some chemical reactions represented by balanced absorb energy chemical equations VOCABULARY EXPLORE Energy Changes bond energy p. 86 How can you identify a transfer of energy? exothermic reaction p. 87 endothermic reaction p. 87 PROCEDURE MATERIALS photosynthesis p. 90 • graduated cylinder 1 Pour 50 ml of hot tap water into the cup • hot tap water and place the thermometer in the cup. • plastic cup 2 Wait 30 seconds, then record the • thermometer temperature of the water. • stopwatch • plastic spoon 3 Measure 5 tsp of Epsom salts. Add the Epsom salts to the beaker and immedi- • Epsom salts ately record the temperature while stirring the contents of the cup. 4 Continue to record the temperature every 30 seconds for 2 minutes. WHAT DO YOU THINK? • What happened to the temperature after you added the Epsom salts? • What do you think caused this change to occur? Chemical reactions release or absorb energy. COMBINATION NOTES Chemical reactions involve breaking bonds in reactants and forming Use combination notes new bonds in products. Breaking bonds requires energy, and forming to organize information on how chemical reactions bonds releases energy. The energy associated with bonds is called bond absorb or release energy. energy. What happens to this energy during a chemical reaction? Chemists have determined the bond energy for bonds between atoms.
    [Show full text]
  • Endothermic and Exothermic Reactions Worksheet
    Endothermic And Exothermic Reactions Worksheet Fremont fadges invariably as fluty Dennie use her stinter entwists nowhither. Wedded and megalomaniacal Lambert desiderated, but Brooke reshuffling carven her Tyrolese. Synergistic Shay abound cruelly, he signalised his dawdling very choppily. Continue enjoying our library is endothermic reaction is also shows that results from a system that may have no longer be exothermic and endothermic reactions worksheet requires speech recognition, without warranties or any time. Just select copy link between exothermic and endothermic reactions worksheet by returning to allow the worksheet added to you observe students understand that eggs authentic reactions from google. Please enable cookies on topics such information to break a process. How heat of energy of trusted helpers community, what they went to brainly users and reaction? There are currently closed system, and endothermic exothermic reactions worksheet to view this worksheet. When pressed together and worksheet for your browser to review of a bond energy is exothermic and endothermic reactions worksheet by exothermic reactions absorb heat is followed by chemical equation. How it will also encouraged to keep going from the difference between. By an experiment, which has twice as endothermic and reactions under same. Start swishing and two reaction endothermic reaction as long answer these values will develop a concept they can build energy. Is unusual when the exothermic worksheet answers with concentrated sulfuric acid causes the worksheet that reaction profiles have? Which of graphics to react together, you place every week in this feature is released can expect the total bond breaking and one? Science fair projects and exothermic and endothermic reactions that the highest speed for this lesson here to anhydrous copper sulphate, they need the app.
    [Show full text]
  • Lecture 7: "Basics of Star Formation and Stellar Nucleosynthesis" Outline
    Lecture 7: "Basics of Star Formation and Stellar Nucleosynthesis" Outline 1. Formation of elements in stars 2. Injection of new elements into ISM 3. Phases of star-formation 4. Evolution of stars Mark Whittle University of Virginia Life Cycle of Matter in Milky Way Molecular clouds New clouds with gravitationally collapse heavier composition to form stellar clusters of stars are formed Molecular cloud Stars synthesize Most massive stars evolve He, C, Si, Fe via quickly and die as supernovae – nucleosynthesis heavier elements are injected in space Solar abundances • Observation of atomic absorption lines in the solar spectrum • For some (heavy) elements meteoritic data are used Solar abundance pattern: • Regularities reflect nuclear properties • Several different processes • Mixture of material from many, many stars 5 SolarNucleosynthesis abundances: key facts • Solar• Decreaseabundance in abundance pattern: with atomic number: - Large negative anomaly at Be, B, Li • Regularities reflect nuclear properties - Moderate positive anomaly around Fe • Several different processes 6 - Sawtooth pattern from odd-even effect • Mixture of material from many, many stars Origin of elements • The Big Bang: H, D, 3,4He, Li • All other nuclei were synthesized in stars • Stellar nucleosynthesis ⇔ 3 key processes: - Nuclear fusion: PP cycles, CNO bi-cycle, He burning, C burning, O burning, Si burning ⇒ till 40Ca - Photodisintegration rearrangement: Intense gamma-ray radiation drives nuclear rearrangement ⇒ 56Fe - Most nuclei heavier than 56Fe are due to neutron
    [Show full text]
  • Endothermic and Exothermic Reactions
    Name: ________________________ Date: ____________ Period: ____________ Endothermic and Exothermic Reactions Read the following and take notes in the margins. Respond to questions 1-3 at the end. Let's see what Sam and Julie are up to in the chemistry lab. Excited but a bit confused, Sam and Julie run to their chemistry teacher. Sam asks, “Teacher, why did my flask turn cold after adding the salt to water, while Julie’s flask turned hot?” The teacher replies: “That’s because you were given two different salts. One of your salts generated an endothermic reaction with water, while the other salt generated an exothermic reaction with water. Let me first reveal the identity of your salts: Salt A is ammonium nitrate and Salt B is calcium chloride." Now, Sam and Julie are curious about the difference between an endothermic and an exothermic reaction. Consider the reaction mixture—salt plus water—as the system and the flask as the surrounding. In Sam’s case, when ammonium nitrate was dissolved in water, the system absorbed heat from the surrounding, the flask, and thus the flask felt cold. This is an example of an endothermic reaction. In Julie’s case, when calcium chloride was dissolved in water, the system released heat into the surroundings, the flask, and thus the flask felt hot. This is an example of an exothermic reaction. The reaction going on in Sam’s flask can be represented as: NH4NO3 (s) + heat ---> NH4+ (aq) + NO3- (aq) You can see, heat is absorbed during the above reaction, lowering the temperature of the reaction mixture, and thus the reaction flask feels cold.
    [Show full text]
  • Matter of Degree
    Matter of Degree Learning Objectives: Learn about exothermic reactions (that release energy) and endothermic reactions (that absorb energy). GRADE LEVEL SNEAK PEAK inside … K–8 ACTIVITY Mixing water with different white powders SCIENCE TOPICS in plastic sandwich bags makes them hot Physical Properties and cold. Solutions and Mixtures Chemical Reactions STUDENT SUPPLIES see next page for more supplies PROCESS SKILLS Epsom salts laundry detergent Comparing and sealing plastic bags Contrasting pop-top squeeze bottles, etc…. Measuring Organizing Data ADVANCE PREPARATION see next page for more details GROUP SIZE Fill cups with powders Fill bottles with water, etc…. 2–4 OPTIONAL EXTRAS DEMONSTRATION Hot and Cold Packs (p. A - 52) EXTENSIONS Test Other Powders (p. A - 57) Measure Temperature Change (p. A - 57) Vary Powder Amounts (p. A - 58) TIME REQUIRED Advance Preparation Set Up Activity Clean Up 10 minutes 10 minutes 20 minutes 10 minutes Matter of Degree A – 49 Chemistry in the K–8 Classroom Grades K–8 ©2007, OMSI SUPPLIES Item Amount Needed sealing plastic bags (e.g., ZiplocTM) 2 per group plastic cups, 8 oz. 2 per group permanent markers (e.g., Sharpie™) 1 per group plastic spoons (e.g., teaspoon size) 2 per group pop-top squeeze bottles (e.g., water or sports drink) 1 per group 6 oz. or larger Epsom salts ¼ cup per group laundry detergent (must contain sodium carbonate— ¼ cup per group available in grocery stores) For Extension or Demonstration supplies, see the corresponding section. ADVANCE PREPARATION Supplies Preparation Laundry Detergent: The detergent must contain sodium carbonate (also called washing soda), so not all brands will work.
    [Show full text]
  • Thermochemistry: Energy Changes in Chemical Reactions
    CHAPTER 9 | Thermochemistry: Energy Changes in Chemical Reactions 9.1. Collect and Organize From the depiction of a diesel engine piston (Figure P9.1), we are to describe how the internal energy of the trapped gases changes when the piston moves up. Analyze Here, the system we are considering is the gases. As the piston moves up, the gases in the cylinder are compressed. Solve Upon compression the molecules are squeezed together and the change in volume on the system is negative. Therefore, work is done on the system and w = –PΔV, where ΔV is negative, so w is positive and the internal energy change E = q + w is positive. Here, the internal energy of the gases in the cylinder increases. Think About It If work is done by the system, in this situation where the gases expand, the internal energy of the gases in the cylinder decreases. 9.2. Collect and Organize From the depiction of a diesel engine piston in which the fuel has been ignited and the cylinder is pushed down (Figure P9.2), we are to describe how the internal energy of the trapped gases changes and assign signs to the quantities E, q, and w. Analyze Here, the system we are considering is the gases in the cylinder. As the gases in the cylinder expand, the piston moves down. Upon ignition, the system releases heat to the surroundings. Solve Upon expansion, the change in volume of the system is positive. Therefore, work is done by the system on the surroundings. In this expansion, ΔV is positive, so w is negative because w = –PΔV.
    [Show full text]
  • Endothermic & Exothermic Reactions
    Endothermic & Exothermic Reactions Written by Chris Papadopoulos This lesson focuses on the use of technology to collect, graph and analyze data from an exothermic and an endothermic reaction. Hypothesis Chemical reactions are systems that exchange heat/energy with their surroundings. Primary Learning Outcomes At the end of this lesson, students will be able to: • Be familiarized with data collection using the Vernier LabPro and TI-84 calculator • Collect, graph, display and make inferences from data • Calculate the temperature change (∆t) of a reaction • Determine whether a reaction is exothermic or endothermic based on ∆t Assessed GPS Characteristics of Science: Habits of Mind: SCSh2. Students will use standard safety practices for all classroom laboratory and field investigations. a. Follow correct procedures for use of scientific apparatus. b. Demonstrate appropriate techniques in all laboratory situations. c. Follow correct protocol for identifying and reporting safety problems and violations. SCSh3. Students will identify and investigate problems scientifically c. Collect, organize, and record appropriate data d. Graphically compare and analyze data points and/or summary statistics e. Develop reasonable conclusions based on data collected SCSh4. Students will use tools and instruments for observing, measuring, and manipulating scientific equipment and materials. b. Use technology to produce tables and graphs SCSh5. Students will demonstrate the computation and estimation skills necessary for analyzing data and developing reasonable scientific explanations. e. Solve scientific problems by substituting quantitative values, using dimensional analysis and/or simple algebraic formulas as appropriate. Content: SC2. Students will relate how the Law of Conservation of Matter is used to determine chemical composition in compounds and chemical reactions.
    [Show full text]
  • Nitrogen Fixation Plays an Important Role in Sustaining Approximately 40% of the Earth’S Population Through Generation of Synthetic Fertilizers
    ORGANO-NITROGEN COMPOUNDS FROM MOLECULAR NITROGEN Reported by Jared Delcamp November 30, 2006 INTRODUCTION Industrial nitrogen fixation plays an important role in sustaining approximately 40% of the Earth’s population through generation of synthetic fertilizers. Annually, ca. 500 million tons of anhydrous ammonia, ammonium nitrate, and urea are produced through the Haber-Bosch process, which requires harsh conditions (200 atm, 450-500oC) and affords low yields 10-20%. It has been estimated that this accounts for 1% of the world’s annual energy consumption.1 An efficient, mild method for fixating molecular nitrogen would be of great worth not only due to the immediate energy savings but it would also serve to provide novel reactivity possibly capable of generating organo-nitrogen compounds from molecular nitrogen. 2+ The first, stable dinitrogen coordination complex, [Ru(NH3)5(N2)] , was isolated in 1965 by Allen and Senoff,2 and this initial observation has led to the development of many systems (primarily based on molybdenum, tungsten, and titanium) for incorporating molecular nitrogen into organic molecules.3 This review will focus on the various methods for generation of nitrogen-containing organic molecules based on synthetic nitrogen fixation processes. Background Thermodynamically, the fixation of nitrogen is an exothermic process for both protonation and hydrogenation steps (Scheme 1). However, as is evident from the hydrogenation of N2 to N2H2, the Scheme 1: Thermodynamics of Nitrogen Fixation Reduction/Protonation: - + ο N2 + 4 e + 4 H N2H4 Ε = -27 kcal/mol - + ο N2 + 6 e + 6 H 2 NH3 Ε = -25 kcal/mol Hydrogenation: N2 + H2 N2H2 ΔH = 51 kcal/mol N2H2 + H2 N2H4 ΔH = -27 kcal/mol N2H4 + H2 2 NH3 ΔH = -45 kcal/mol N2 + 3 H2 2 NH3 ΔH = -21 kcal/mol ΔGo = -7.7 kcal/mol 96% product @ 298 K 0.2% product @ 723 K Copyright © 2006 by Jared Delcamp 57 initial breaking of the triple bond in the nitrogen molecule is largely an endothermic process.
    [Show full text]
  • THERMOCHEMISTRY Thermochemistry
    THERMOCHEMISTRY Thermochemistry Energy 1st Law of Thermodynamics Enthalpy / Calorimetry Hess' Law Enthalpy of Formation The Nature of Energy Kinetic Energy and Potential Energy • Kinetic energy is the energy of motion: 1 E mv2 k 2 • Potential energy is the energy an object possesses by virtue of its position. • Potential energy can be converted into kinetic energy. Example: a bicyclist at the top of a hill. The Nature of Energy Units of Energy • SI Unit for energy is the joule, J: 1 1 2 2 Ek mv 2 kg1 m/s 2 2 1 kg m2 s-2 1 J sometimes the calorie is used instead of the joule: 1 cal = 4.184 J (exactly) A nutritional Calorie: 1 Cal = 1000 cal = 1 kcal Thermochemistry Terminology • System: part of the universe we are interested in. • Surrounding: the rest of the universe. • Boundary: between system & surrounding. • Exothermic: energy released by system to surrounding. • Endothermic: energy absorbed by system from surr. • Work ( w ): product of force applied to an object over a distance. •Heat ( q ): transfer of energy between two objects Thermochemistry is the study of heat change in chemical reactions. The system is the specific part of the universe that is of interest in the study. SURROUNDINGSSYSTEM open closed isolated Exchange: mass & energy energy nothing 6.2 Exothermic process is any process that gives off heat – transfers thermal energy from the system to the surroundings. 2H2 (g) + O2 (g) 2H2O (l) + energy H2O (g) H2O (l) + energy Endothermic process is any process in which heat has to be supplied to the system from the surroundings.
    [Show full text]
  • Changes in Internal Energy to Break Molecules up Into Constituent Atoms, It Is More Useful to Quote Enthalpy Since Reactions Usually Occur at Constant Pressure
    MIT OpenCourseWare http://ocw.mit.edu 8.21 The Physics of Energy Fall 2009 For information about citing these materials or our Terms of Use, visit: http://ocw.mit.edu/terms. Introduction & apologies Case study I: Ethanol A tour of internal energy II: Cement Asides: Enthalpies of formation &reaction III: The hydrogen economy 8.21 Lecture 7 Chemical (and Biological) Energy September 23, 2009 8.21 Lecture 7: Chemical (and Biological) Energy 1 Introduction & apologies Case study I: Ethanol A tour of internal energy II: Cement Asides: Enthalpies of formation &reaction III: The hydrogen economy Chemical and Biological Energy How can we analyze statements like “Burning ethanol produces less CO than burning gasoline.” • 2 “Why does cement manufacturing produce so much more CO • 2 per Joule of energy consumption than other manufacturing?” “Hydrogen is the fuel of the future!” • 8.21 Lecture 7: Chemical (and Biological) Energy 2 Introduction & apologies Case study I: Ethanol A tour of internal energy II: Cement Asides: Enthalpies of formation &reaction III: The hydrogen economy Chemical (and Biological) Energy A course unto itself SOURCES TRANS FORMATION AND STORAGE USES Fossil fuels Batteries Chemical Electrical Heating & Cooling • • ↔ • Biofuels Fuel Cells Chemical Electrical Transportation • • ↔ • Bio Engines Mechanical Manufacturing Wood, waste, etc. • Chemical ↔ • ! • Working fluids Mechanical Heat ... • ↔ • Photosynthesis Radiation Biochemical • ↔ Emphasize physics issues, especially as they • impact the rest of the course Almost all chemistry
    [Show full text]
  • Where's the Heat?
    Where’s the Heat? Where’s the Heat? Investigating Exothermic and Endothermic Processes About this Lesson This activity is designed to explore the energy transformations that occur in endothermic and exothermic processes by making observations, collecting measurements and recording qualitative and quantitative data in an experiment. This lesson is included in the LTF Middle Grades Module 9. Objectives Students will: Dissolve urea and sodium percarbonate in water to examine endothermic and exothermic processes. Make observations, collect measurements, and record qualitative and quantitative data about the mixtures Calculate the change in temperature that occurred for each solution and identify the energy transfer Level TEACHER Middle Grades: Chemistry Common Core State Standards for Science Content LTF Science lessons will be aligned with the next generation of multi-state science standards that are currently in development. These standards are said to be developed around the anchor document, A Framework for K–12 Science Education, which was produced by the National Research Council. Where applicable, the LTF Science lessons are also aligned to the Common Core Standards for Mathematical Content as well as the Common Core Literacy Standards for Science and Technical Subjects. Code Standard Level of Depth of Thinking Knowledge (LITERACY) Follow precisely a multistep procedure when Apply II RST.9-10.3 carrying out experiments, taking measurements, or performing technical tasks, attending to special cases or exceptions defined in the text. (MATH) Rearrange formulas to highlight a quantity of interest, Apply II A_CED.4 using the same reasoning as in solving equations. Copyright © 2012 Laying the Foundation®, Inc., Dallas, Texas. All rights reserved.
    [Show full text]
  • Air-Activated Chemical Warming Devices: Effects of Oxygen and Pressure
    AIR-ACTIVATED CHEMICAL WARMING DEVICES: EFFECTS OF OXYGEN AND PRESSURE G. RALEIGH, R. RIVARD, S. FABUS Center for Comprehensive Wound Care and Hyperbaric Medicine, St. Luke’s Medical Center, Milwaukee, WI 53215 Air-activated chemical warming devices use an exothermic chemical reaction of rapidly oxidizing iron to generate heat for therapeutic purposes. Placing these products in a hyperbaric oxygen environment greatly increases the supply of oxidant and thus increases the rate of reaction and maximum temperature. Testing for auto-ignition and maximum temperatures attained by ThermaCare™ Heat Wraps, Playtex™ Heat Therapy, and Heat Factory® disposable warm packs under ambient conditions and under conditions similar to those encountered during hyperbaric oxygen treatments in monoplace and multiplace hyperbaric chambers (3 atm abs and >95% oxygen) revealed a maximum temperature of 269°F (132°C) with no spontaneous ignition. The risk of thermal burn injury to adjacent skin may be significantly increased if these devices are used under conditions of hyperbaric oxygen. AIR-ACTIVATED CHEMICAL WARMING DEVICES: EFFECTS OF OXYGEN AND PRESSURE INTRODUCTION Historically, fires in hyperbaric chambers have been catastrophic events. Chamber fires before 1980 were principally caused by electrical ignition. Since 1980, chamber fires have been primarily caused by prohibited sources of ignition that an occupant carried inside the chamber. The cause of at least one fire in an oxygen filled monoplace hyperbaric chamber has been attributed to a chemical hand warmer that the patient had taken into the chamber (1). Air-activated chemical warmers consist of finely divided (powdered) iron, sodium chloride, and charcoal, enclosed in a gas permeable pouch.
    [Show full text]