University of Texas at AustinMichigan Technological University 1 Environmental Assessment During Process Synthesis - Chapters 7 and 8 David T. Allen Department of Chemical Engineering University of Texas

University of Texas at AustinMichigan Technological University 2 Software exploration Green Chemistry Expert System TOPIC AREAS Green Synthetic Reactions - search a database for alternatives Designing Safer Chemicals - information on chemical classes Green Solvents/Reaction Conditions - alternative solvents / uses - solvent properties

University of Texas at AustinMichigan Technological University 3 Software demonstration Green Chemistry Expert System search Green Synthetic Reactions for adipic acid references

University of Texas at AustinMichigan Technological University 4 Adipic Acid Synthesis Traditional vs. New Traditional Route - from cyclohexanol/cyclohexanone Cu (.1-.5%) C 6 H 12 O+ 2 HNO H 2 O C 6 H 10 O 4 + (NO, NO 2, N 2 O, N 2 ) V (.02-.1%) 92-96% Yield of Adipic Acid Carbon - 100% Oxygen - 4/9 x 100 = 44.4% Hydrogen - 10/18 x 100 = 55.6% Nitrogen - 0% Product Mass = (6 C)(12) + (10 H)(1) + (4 O)(16) = 146 g Reactant Mass = (6 C)(12) + (18 H)(1) + (9 O)(16) + (2 N)(14) = 262 g Mass Efficiency = 146/262 x 100 = 55.7% global warming ozone depletion hazardous Davis and Kemp, 1991, Adipic Acid, in Kirk-Othmer Encyclopedia of Chemical Technology, V. 1,

University of Texas at AustinMichigan Technological University 5 New Route - from cyclohexene Na 2 WO 4 2H 2 O (1%) C 6 H H 2 O 2 C 6 H 10 O H 2 O [CH 3 (n-C 8 H 17 ) 3 N]HSO 4 (1%) 90% Yield of Adipic Acid Carbon - 100% Oxygen - 4/8 x 100 = 50% Hydrogen - 10/18 x 100 = 55.6% Product Mass = (6 C)(12) + (10 H)(1) + (4 O)(16) = 146 g Reactant Mass = (6 C)(12) + (18 H)(1) + (8 O)(16) = 218 g Mass Efficiency = 146/218 x 100 = 67% Adipic Acid Synthesis Traditional vs. New Sato, et al. 1998, A “green” route to adipic acid:…, Science, V. 281, 11 Sept

University of Texas at AustinMichigan Technological University 6 Maleic Anhydride Synthesis Benzene vs Butane - Mass Efficiency Benzene Route (Hedley et al. 1975, reference in ch. 8) V 2 O 5 2 C 6 H O 2 2 C 4 H 2 O 3 + H 2 O + 4 CO 2 (air) MoO 3 95% Yield of Maleic Anhydride from Benzene in Fixed Bed Reactor Butane Route (VO) 2 P 2 O 5 C 4 H O 2 C 4 H 2 O H 2 O (air) 60% Yield of Maleic Anhydride from Butane in Fixed Bed Reactor Felthouse et al., 1991, “Maleic Anhydride,..”, in Kirk-Othmer Encyclopedia of Chemical Technology, V. 15,

University of Texas at AustinMichigan Technological University 7 Maleic Anhydride Synthesis Benzene vs Butane - Summary Table 1 Rudd et al. 1981, “Petroleum Technology Assessment”, Wiley Interscience, New York 2 Chemical Marketing Reporter (Benzene and MA 6/12/00); Texas Liquid (Butane 6/22/00) 3 Threshold Limit Value, ACGIH - Amer. Conf. of Gov. Indust. Hyg., Inc., 4 Toxicity Weight, and 5 ChemFate Database - EFDB menu item

University of Texas at AustinMichigan Technological University 8 Maleic Anhydride Synthesis Benzene vs Butane - Tier 1 Assessment Benzene Route Butane Route Where i is the overall stoichiometric coefficient of reactant or product i

University of Texas at AustinMichigan Technological University 9 Benzene Route Butane Route Maleic Anhydride Synthesis Benzene vs Butane - Tier 1 Assessment

University of Texas at AustinMichigan Technological University 10 Identifying and estimating air emissions and other releases from process units 1. Identify waste release sources in process flowsheets 2. Methods for estimating emissions from chemical processes 3. Case study - Benzene to Maleic Anhydride process evaluation Chapter 8

University of Texas at AustinMichigan Technological University 11 Benzene to MA Process AP-42, Chapter 6, section 6.14, Air CHIEF CD, V 2 O 5 2 C 6 H O > 2 C 4 H 2 O 3 + H 2 O + 4 CO 2 MoO 3

University of Texas at AustinMichigan Technological University Waste streams from process units 2. Major equipment - vents on reactors, column separators, storage tanks, vacuum systems,.. 3. Fugitive sources - large number of small releases from pumps, valves, fittings, flanges, open pipes,.. 4. Loading/unloading operations 5. Vessel clean out, residuals in drums and tanks 6. Secondary sources - emissions from wastewater treatment, other waste treatment operations, on-site land applications of waste,.. 7. Spend catalyst residues, column residues and tars, sludges from tanks, columns, and wastewater treatment, … 8. Energy consumption - criteria air pollutants, traces of hazardous air pollutants, global warming gases, Typical waste emission sources from chemical processes - Ch 8

University of Texas at AustinMichigan Technological University Actual measurements of process waste stream contents and flow rates or indirectly estimated based on mass balance and stoichiometry. (most preferred but not always available at design stage) 2. Release data for surrogate chemical or process or emission factors based on measured data 3. Mathematical models of emissions (emission correlations, mass transfer theory, process design software, etc.) 4. Estimates based on best engineering judgement or rules of thumb Process release estimation methods

University of Texas at AustinMichigan Technological University 14 Waste stream summaries based on past experience 1. Hedley, W.H. et al. 1975, “Potential Pollutants from Petrochemical Processes”, Technomics, Westport, CT 2. AP-42 Document, Chapters 5 and 6 on petroleum and chemical industries, Air CHIEF CD, 3. Other sources i. Kirk-Othmer Encyclopedia of Chemical Technology, ii. Hydrocarbon Processing, “Petrochemical Processes ‘99”, March Emission estimation methods: based on surrogate processes

University of Texas at AustinMichigan Technological University 15 Emission Factors - major equipment Average Emission Factors for Chemical Process Units Calculated from the US EPA L&E Database Process UnitEF av ; (kg emitted/10 3 kg throughput) Reactor Vents1.50 Distillation Columns Vents0.70 Absorber Units2.20 Strippers0.20 Sumps/Decanters0.02 Dryers0.70 Cooling Towers0.10

University of Texas at AustinMichigan Technological University 16 Emission factors - fugitive sources; minor equipment

University of Texas at AustinMichigan Technological University 17 Emission factors - criteria pollutants from energy consumption AP-42, Chapter 1, section 1.3, Air CHIEF CD,

University of Texas at AustinMichigan Technological University 18 Emission factors - CO 2 from energy consumption AP-42, Chapter 1, section 1.3, Air CHIEF CD,

University of Texas at AustinMichigan Technological University 19 Software Tools Storage tanks TANKS program from EPA - Wastewater treatment WATER8 - on Air CHIEF CD - Treatment storage and disposal facility (TSDF) processes CHEMDAT8 - on Air CHIEF CD Emission correlations/models - storage tanks and waste treatment

University of Texas at AustinMichigan Technological University 20 Tier 2 environmental assessment indexes 1. Energy: [total energy (Btu/yr)] / [production rate (MM lb/yr)] 2. Materials: [raw materials (MM lb/yr)] / [production rate (MM lb/yr)] 3. Water: [process water (MM lb/yr)] / [production rate (MM lb/yr)] 4. Emissions: [total emissions and wastes (MM lb/yr)] / [production rate (MM lb/yr)] 5. Targeted emissions: [total targeted emissions and wastes (MM lb/yr)] / [production rate (MM lb/yr)]

University of Texas at AustinMichigan Technological University 21 Benzene to MA Process AP-42, Chapter 6, section 6.14, Air CHIEF CD, V 2 O 5 2 C 6 H O > 2 C 4 H 2 O 3 + H 2 O + 4 CO 2 MoO 3

University of Texas at AustinMichigan Technological University 22 Air emission and releases sources: Benzene to MA Process Source Identification 1. Product recovery absorber vent 2. Vacuum system vent 3. Storage and handling emissions 4. Secondary emissions from water out, spent catalyst, fractionation column residues 5. Fugitive sources (pumps, valves, fittings,..) 6. Energy consumption

University of Texas at AustinMichigan Technological University 23 Uncontrolled Air emission / releases Benzene to MA Process (lb/10 3 lb MA)

University of Texas at AustinMichigan Technological University 24 Benzene to MA Process Conclusions from emissions summary 1. Chemical profile: CO 2 > CO > benzene > tars-oxygenates > MA 2. Toxicity profile: Benzene > MA > CO > tars-oxygenates > CO 2 3. Unit operations profile: Absorber vent > energy consumption > vacuum system vent - Pollution prevention and control opportunities are centered on benzene, the absorber unit, and energy consumption -

University of Texas at AustinMichigan Technological University 25 Emission Mechanisms; Fixed Roof Tank L TOTAL = L STANDING + L WORKING Roof Column Vent  T  P Liquid Level - Weather, paint color/quality - Weather - liquid throughput, volume of tank Vapor pressure of liquid drives emissions Pollution prevention - Storage Tanks

University of Texas at AustinMichigan Technological University 26 Storage tank comparison - TANKS 4.0 program Gaseous waste stream flowsheet Toluene emissions only 100 kgmole/hr absorber oil rate 15,228.5 gallon tank for each comparison Pollution prevention strategies replace fixed-roof with floating-roof tank maintain light-colored paint in good condition heat tank to reduce temperature fluctuations

University of Texas at AustinMichigan Technological University 27 Fugitive Sources - pollution prevention techniques