“Green Chemistry” A greener future…

“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


¿WHY?

• 1991 – Green Chemistry is promoted by EPA – (Paul Anastas)


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


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


Green Chemistry Goals

• Reduction or elimination of

–Waste

–Toxic chemicals or processes

–Energy use


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


Environmental Environmental ChemistryChemistry

Clean upResearch

Monitoring Prevention

EnvironmentalRegulations

Green

Chemistry


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


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/


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!


¿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+


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.


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


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



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.


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.


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.



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…


Atom Economy

– Barry Trost, Stanford University

– Evaluate the efficiency of the chemical transformation

“Because an Atom is a Terrible Thing to Waste”


Atom Economy

How many of the atoms of the reactant are incorporated into the final product and how many are wasted?


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


% Yield vs. atomic economy

• % Yield = 43.7%

• %Atomic Economy = 83.6%


Chemical Reactions and Atomic Economy

• Addition > Substitutions > Eliminations

• Re-arrangements: 100 % efficient

– Ex: Diels-Alder


Twelve Principles of Green Chemistry: 8. Use safer solvents and reaction conditions

• Avoid:

– solvents,

– separation agents,

– other auxiliary chemicals.

• USE: innocuous chemicals.


Solvents

• Organic solvents = high VOC’s

• Alternatives– Synthesis without solvents

– Water

– Supercritical fluids (CO2)

– Ionic Liquids


Dry Cleaning – Greener…

• Initially gasoline and kerosene were used

• Now use PERC

• Future use Supercritical CO2 and CO2 surfactants


Twelve Principles of Green Chemistry: 9. Increase energy efficiency:

• Run chemical reactions at ambient temperature and pressure whenever possible.


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.


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.


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 $$$$!!


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…


PAT: Process Analytical Technologies

• Helps to:

–Understand the process

–Make corrections in the moment, without waiting for the final product

–Develop mitigation strategies.


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.


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


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%)


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

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


• 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


“Green Chemistry” A greener future…

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