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“Green Chemistry”A greener future…
Prof. Ángela González
Department of Biology, Chemistry and Env. Sciences
Interamerican University of Puerto RicoSan Germán [email protected]
What to expect from this talk…
• Why?– History
• What?– Definitions
• How? – Principles
• Examples
Angela González, Ph.D. / UIA-SG
¿WHY?• 70’s – need to improve environmental
quality– Control Laws
– Contaminants produced and THEN treated before releasing them to the environment
– Excellent idea IF there is good control and handling of environmental laws
• It is continuous, slow and expensive
Angela González, Ph.D. / UIA-SG
Angela González, Ph.D. / UIA-SG
¿WHY?
• 1991 – Green Chemistry is promoted by EPA – (Paul Anastas)
Angela González, Ph.D. / UIA-SG
What is Green Chemistry?
… or sustainable/environmentally benign chemistry is the design of chemical products and processes that reduce or eliminate the use and generation of hazardous substances
www.epa.gov/greenchemistry
Angela González, Ph.D. / UIA-SG
What is Green Chemistry?
… principles to reduce or eliminate use or production of dangerous chemicals in the design, manufacture and application of
chemical products. Green Chemistry Theory & Practice, P T Anastas & J C
Warner, Oxford University Press 1998
Angela González, Ph.D. / UIA-SG
Green Chemistry Goals
• Reduction or elimination of
–Waste
–Toxic chemicals or processes
–Energy use
Angela González, Ph.D. / UIA-SG
Green chemistry is looking to:
Reduce
Waste
Materials
Danger
Risk
Energy
Environmental Impact
COST! ($$$$)Angela González, Ph.D. / UIA-SG
Green Chemistry vs. Environmental Chemistry
• Environmental Chemistry:
– Study of sources, reactions, transport, effects and destruction of chemical compounds in the ground, water and air.
Stanley Manahan, Env. Chemistry, 6th Ed. CRC Press. 2005
Angela González, Ph.D. / UIA-SG
Environmental Environmental ChemistryChemistry
Clean upResearch
Monitoring Prevention
EnvironmentalRegulations
Green
Chemistry
Angela González, Ph.D. / UIA-SG
Green Chemistry Benefits:
• Reduced waste, eliminating costly end-of-the-pipe treatments
• Safer products
• Reduced use of energy and resources
• Improved competitiveness of chemical manufacturers and their customers
www.epa.gov/greenchemistry/Angela González, Ph.D. / UIA-SG
What has happened?
• 1996 Presidential Green Chemistry Challenge Awards -promote non contaminant technologies.
• 1997 Green Chemistry and Engineering Conference
• 1999 Journal “Green Chemistry”
• Chemical and Engineering News
• 2000 GCI integrated into ACS
• 2000 Journal of Chemical Education
Angela González, Ph.D. / UIA-SG
and?• Until 2006 all the technologies nominated to
the PGCCA had eliminated the use or production of:– 1.2 billion pounds of chemicals and solvents per
year
• Enough to fill 5000 train tanks or a 62 miles long train
– 57 million pounds of CO2 has been reduced • equivalent to take out circulation 37000 cars.
– 16 billion gallons of water per year have been saved www.epa.gov/greenchemistry/
Angela González, Ph.D. / UIA-SG
Twelve Principles of Green Chemistry
•Paul Anastas and John Warner in Green Chemistry: Theory and Practice (Oxford University Press: New York, 1998).
Twelve Principles of Green Chemistry:1. Prevent waste
• Design chemical syntheses to prevent waste, leaving no waste to treat or clean up.
• Easier than clean up, transport or store them
• Transforming chemical reactions that incorporate the largest amount of the starting materials = Less waste!
Angela González, Ph.D. / UIA-SG
¿What kind of industry is worst?
•New Industries:
•Large gain margins $$$
•More complex chemistry
•More waste production R A Sheldon J Chem Tech Biotechnol 1997 68 381
Industry Products (tons)
Kg byproducts/ Kg products
Petroleum Refinery 106 – 108 <0.1
Chemical Production
104 – 106 1-5
Specialized Chemical Compounds
102 - 104 5 – 50
Pharmaceutical 10 - 103 25 – 100+
Angela González, Ph.D. / UIA-SG
Possible sources of waste reduction:
Inputs“eco-friendly” solvents, high purity reagents, solvent recycling.
ProductionOptimization of reaction time, temperature and pressure. New synthesis pathways.
DischargesReduce water usage, improve filtering procedures and reuse waste products.
Angela González, Ph.D. / UIA-SG
Twelve Principles of Green Chemistry: 2. Design safer chemicals and products:
• Design chemical products to be fully effective, yet have little or no toxicity.
• …chemicals that are less hazardous to human health and the environment are:
– Less toxic to organisms and ecosystems
– Not persistent or bioaccumulative in organisms or the environment
– Inherently safer with respect to handling and use
Angela González, Ph.D. / UIA-SG
Twelve Principles of Green Chemistry:
3. Design less hazardous chemical syntheses:
• Use and generate substances with little or no toxicity to humans and the environment.
• Avoid reactions that give dangerous by-products
Angela González, Ph.D. / UIA-SG
Twelve Principles of Green Chemistry:
4. Use renewable feedstocks:
• Use raw materials and feedstocks that are renewable rather than depleting.
• Agricultural products
• Wastes of other processes;
• Reduce dependency from fossil fuels (petroleum, natural gas, or coal) or are mined.
Angela González, Ph.D. / UIA-SG
Twelve Principles of Green Chemistry: 5. Use catalysts, not stoichiometric reagents:
• They are selective
• Catalysts are used in small amounts
• Can carry out a single reaction many times.
• Improve production and energy consumption
• They are preferable to stoichiometric reagents, which are used in excess and work only once.
Angela González, Ph.D. / UIA-SG
Twelve Principles of Green Chemistry: 6. Avoid chemical derivatives:
• Avoid:
• blocking or protecting groups or any temporary modifications if possible.
• Derivatives use additional reagents and generate waste.
Angela González, Ph.D. / UIA-SG
Twelve Principles of Green Chemistry:
7. Maximize atom economy:
• Final product contains the maximum proportion of the starting materials. There should be few, if any, wasted atoms.
• Relation between atoms in the products and atoms in the reagents
– Addition – good atom efficiency
– Elimination – not so good…
Angela González, Ph.D. / UIA-SG
Atom Economy
– Barry Trost, Stanford University
– Evaluate the efficiency of the chemical transformation
“Because an Atom is a Terrible Thing to Waste”
Angela González, Ph.D. / UIA-SG
Atom Economy
How many of the atoms of the reactant are incorporated into the final product and how many are wasted?
Angela González, Ph.D. / UIA-SG
How a reactions efficiency is measured?
Reaction Yield% yield = (actual quantity of products achieved) x 100
(theoretical quantity of products
achievable)
Atom Economy*
% atom economy = (MWt of desired products) x 100
(MWt of all products)
* B M Trost, Science 1991, 254, 1471Angela González, Ph.D. / UIA-SG
Atom EconomyH3C-CH2-CH2-CH2-OH + Na-Br + H2SO4 H3C-CH2-CH2-CH2-Br + NaHSO4 + H2O
1 2 3 4 5 6
% Atom Economy = (FW of atoms utilized/FW of all reactants) X 100 = (137/275) X 100 = 50%
Reagents Formula ReagentsFW
UtilizedAtoms
Weightof
UtilizedAtoms
UnutilizedAtoms
Weight ofUnutilized
Atoms
H3C-CH2-CH2-CH2-OH 74 4C, 9H 57 OH 17
Na-Br 103 Br 80 Na 23
H2SO4 98 ------ 0 2H, 4O, S 98
Total4C, 12H, 5O, Br, Na, S
275 4C, 9H, Br
137 3H, 5O, Na, S
138
Angela González, Ph.D. / UIA-SG
% Yield vs. atomic economy
• % Yield = 43.7%
• %Atomic Economy = 83.6%
Angela González, Ph.D. / UIA-SG
Chemical Reactions and Atomic Economy
• Addition > Substitutions > Eliminations
• Re-arrangements: 100 % efficient
– Ex: Diels-Alder
Angela González, Ph.D. / UIA-SG
Twelve Principles of Green Chemistry: 8. Use safer solvents and reaction conditions
• Avoid:
– solvents,
– separation agents,
– other auxiliary chemicals.
• USE: innocuous chemicals.
Angela González, Ph.D. / UIA-SG
Solvents
• Organic solvents = high VOC’s
• Alternatives– Synthesis without solvents
– Water
– Supercritical fluids (CO2)
– Ionic Liquids
Angela González, Ph.D. / UIA-SG
Dry Cleaning – Greener…
• Initially gasoline and kerosene were used
• Now use PERC
• Future use Supercritical CO2 and CO2 surfactants
Angela González, Ph.D. / UIA-SG
Twelve Principles of Green Chemistry: 9. Increase energy efficiency:
• Run chemical reactions at ambient temperature and pressure whenever possible.
Angela González, Ph.D. / UIA-SG
Twelve Principles of Green Chemistry: 10. Design chemicals and products to degrade after use:
• Design chemical products to break down to innocuous substances after use so that they do not accumulate in the environment.
Angela González, Ph.D. / UIA-SG
Twelve Principles of Green Chemistry: 11. Analyze in real time to prevent pollution:
• Include in-process real-time monitoring and control during syntheses to minimize or eliminate the formation of byproducts.
Angela González, Ph.D. / UIA-SG
PAT:Process Analytical Technologies
• Measure quality and execution properties DURING manufacturing
• Information is gather continuously to improve process
http://www.fda.gov/Cder/OPS/PAT.htmAngela González, Ph.D. / UIA-SG
Pre - PAT
• Analysis of raw materials, intermediates and final products
• In case of problems: WHOLE lot rejected = A LOT OF WASTE!... A LOT OF $$$$!!
Angela González, Ph.D. / UIA-SG
Like you do while cooking…
• While you cook you test the food, and apply the needed corrections to improve it:– If it is too salty: …
– If it is too bland: ….
– If you have extra guest…
– If it is too acidic: stop there…
Angela González, Ph.D. / UIA-SG
PAT: Process Analytical Technologies
• Helps to:
–Understand the process
–Make corrections in the moment, without waiting for the final product
–Develop mitigation strategies.
Angela González, Ph.D. / UIA-SG
Twelve Principles of Green Chemistry: 12. Minimize the potential for accidents:
• Design chemicals and their forms (solid, liquid, or gas) to minimize the potential for chemical accidents:
• explosions,
• fires, and
• releases to the environment.
Angela González, Ph.D. / UIA-SG
Example of Green Chemistry Synthesis - Ibuprofen
Ibuprofen SynthesisClassic Route
• Demand:
13,000 TPY
• Developed in 1960
• 6 steps reaction
Ac2O
AlCl3
COCH3
HCl, AcOH, Al Waste
ClCH2CO2Et
NaOEt
OEtO2C
HCl
H2O / H+
OHC
AcOH
NH2OH
OHNN
H2O / H+
HO2C
NH3
Angela González, Ph.D. / UIA-SG
Ibuprofen SynthesisClassic Route
•Atomic Economy: 32%
• If this synthesis were to be used today, the amount of by-products per year:
MORE WASTE THAN PRODUCT!!!Angela González, Ph.D. / UIA-SG
Boots & Hoechst Synthesis of Ibuprofen – Green Route
O
HF
AcOH
Ac2O
H2 / Ni
OH
CO, Pd
HO2C
Developed to improve production:* 3 steps* No solvents* Catalytic vs. stoichiometric reagents* Recycling, reuse and recovery of byproducts and reagents (acetic acid >99%; HF >99.9%)
Angela González, Ph.D. / UIA-SG
Boots & Hoechst Synthesis of Ibuprofen – Green Route
•Atomic Economy 77%•Faster•More % yield •Less waste produced
And a happier environmentAngela González, Ph.D. / UIA-SG
Angela González, Ph.D. / UIA-SG
Angela González, Ph.D. / UIA-SG
What is green chemistry looking for?
• Waste production minimization from the source
• Use of catalysts
• Use of non-toxic reagents
• Use of renewable sources
• Improvement of atomic economy
• Use of non-solvent or environmental benign solvents
Angela González, Ph.D. / UIA-SG
• Anastas, P. T.; Warner, J. C. Green Chemistry: Theory and Practice; Oxford University Press: New York, 1998
• B M Trost, Science 1991, 254, 1471
• PAT: – http://www.fda.gov/Cder/OPS/PAT.htm
• EPA: – http://www.epa.gov/greenchemistry/index.html
• ACS Green Chemistry Institute: – http://acs.org
• Michael Cann, University of Scranton: – http://academic.scranton.edu/faculty/CANNM1/
greenchemistry.html
Angela González, Ph.D. / UIA-SG