MPD_2014
SOME WELL-PUBLICIZED
INCIDENTS FROM THE PAST
FEW DECADES…
The Cuyahoga River in Ohio became so polluted
with chemicals it caught fire.
A plant accident in Bhopal, India, released methyl
isocyanate. Nearly 4000 people died.
SOME WELL-PUBLICIZED
INCIDENTS FROM THE PAST
FEW DECADES…
An accidental
release of
chemicals,
including dioxin, in
Seveso, Italy, in
1976 resulted in
death of farm
animals and longterm health
problems for many
local residents.
ENVIRONMENTAL DISASTERS
DDT
CFCs
Apparent benefits were offset by unexpected side
effects.
GOOD
• created in 1928 as a non-toxic, non- flammable
refrigerant
• also used as solvents and in air conditioners
• low reactivity and volatility
BAD
• UV light in the upper atmosphere easily breaks the
C-Cl bonds
• free radicals formed speeded up the depletion of the
ozone layer
MANY COUNTRIES HAVE
ALREADY ENACTED LAWS AND
SIGNED INTERNATIONAL
TREATIES TO REDUCE POLLUTION
LEVELS, INCLUDING:
• Montreal Protocol to Protect the
Ozone Layer
• Global Treaty on Persistent
Organic Pollutants
• Rio Declaration on Environment
and Development
Risk Due to a Hazardous Substance
Risk=f(Hazard, Exposure)
environmental laws attempt to control exposure
Controlling Exposure =
“end of the pipe solution”
THE POLLUTION PREVENTION
Risk=f(HAZARD, Exposure)
Eliminate the hazard, no need to
worry about the exposure!
GREEN CHEMISTRY
PREVENTING POLLUTION
SUSTAINING THE EARTH
“ Chemistry has an important role to
play in achieving a sustainable
civilization on earth.”
— Dr. Terry Collins, Professor of Chemistry
Carnegie Mellon University
GREEN CHEMISTRY
DEFINITION
Green Chemistry is the utilisation of a set of
principles that reduces or eliminates the use or
generation of hazardous substances in the
design, manufacture and application of chemical
products.
Green chemistry about....
•
•
•
•
•
Waste Minimisation at Source
Use of Catalysts in place of Reagents
Using Non-Toxic Reagents
Use of Renewable Resources
Improved Atom Efficiency
Green Chemistry Is About...
Waste
Materials
Hazard
Risk
Energy
Cost
Why do we need Green Chemistry ?
• Chemistry is undeniably a very prominent
part of our daily lives.
• Chemical developments also bring new
environmental problems and harmful
unexpected side effects, which result in the
need for ‘greener’ chemical products.
• A famous example is the pesticide DDT.
Examples of Green Chemistry
 New syntheses of Ibuprofen.
 Integrated circuit production.
 Removing Arsenic and Chromate from pressure
treated wood.
 Many new pesticides.
 New oxidants for bleaching paper and disinfecting
water.
 Getting the lead out of automobile paints.
 Recyclable carpeting.
 Replacing VOCs and chlorinated solvents.
 Biodegradable polymers from renewable resources.
EXAMPLES OF
GREEN CHEMISTRY
•
Safer dry cleaning


Initially gasoline and kerosene were used
Chlorinated solvents are now used, such as perc
 Supercritical/liquid carbon dioxide (CO2)
CHEMICALS FOR
DRY CLEANING
•
•
Perchloroethylene (“perc”) is the
solvent most widely used in dry
cleaning clothing.
Perc is suspected of causing
cancer and its disposal can
contaminate ground water.
A SAFER METHOD OF
DRY CLEANING
•
•
Liquid CO2 can be used as a safer
solvent if a wetting agent is used
with it to dissolve grease.
This method is now being used
commercially by some dry cleaners.
Critical Temperature, Tc
LEAD POLLUTION
HAS BEEN DECREASED BY…
•
•
Replacing lead in paint with safe
alternatives, and
Replacing tetraethyl lead with less
toxic additives (e.g., “lead-free”
gasoline).
Risk Due to a Hazardous Substance
Risk=f(Hazard, Exposure)
Risk=f(HAZARD, Exposure)
GREEN CHEMISTRY
DEFINITION
Green Chemistry is the utilisation of a set of
principles that reduces or eliminates the use or
generation of hazardous substances in the
design, manufacture and application of chemical
products.
12 Principles of Green Chemistry
1. Prevention
It is better to prevent waste than to treat or
clean up waste after it is formed
2. Atom economy
Design syntheses so that the final product
contains the maximum proportion of the
starting materials. There should be few, if
any, wasted atoms.
12 Principles of Green Chemistry
3.Less hazardous chemical synthesis
Methods should be designed that use and
generate substances with little or no toxicity
to humans and the environment.
Eg.
4.Designing safer chemicals
Chemical products should be designed to be
fully effective, yet have little or no toxicity.
Eg.
12 Principles of Green Chemistry
5. Safer solvents and auxiliaries
The use of auxiliary substances (solvents,
separation agents, etc.) should be made
unnecessary whenever possible and, when
used, it should be harmless.
Eg.
6. Energy requirements should be recognized
for their environmental and economic
impacts and should be minimized. Synthetic
methods should be conducted at ambient
temperature and pressure.
12 Principles of Green Chemistry
7. A raw material or feedstock should be
renewable rather than depleting whenever
technically and economically practical.
8. Unnecessary derivatization (blocking group,
protection/deprotection, temporary
modification of physical/chemical processes)
should be avoided whenever possible.
Eg.
12 Principles of Green Chemistry
9. Minimise waste by using catalysts in small
amounts that can carry out a single reaction
many times.
10. Chemical products would be designed so
that at the end of their function they do not
persist in the environment and instead
break down into innocuous degradation
products.
Eg.
12 Principles of Green Chemistry
11. Real-time analysis for pollution prevention
Analytical methodologies need to be further
developed to allow for real-time in-process
monitoring and control prior to the
formation of hazardous substances.
Eg.
12. Substances and the form of a substance
used in a chemical process should be
chosen so as to minimize the potential for
chemical accidents, including releases,
explosions, and fires.
Eg.
Synthetic methods should be designed
to maximize the incorporation of all
materials used in the process into the
final product.
(Brufen)
Atom Economy Example…
• Calculate the percentage atom economy in the formation of
1-iodiopropane from 1-propanol according to the following
reaction.
CH3CH2CH3OH + NaI + H2SO4  CH2CH2CH2I + NaHSO4 + H2O
Formula of
Reactants
Molar
Mass of
Reactants
Atoms used
in Product
Sum of
Molar Mass
of Used
Atoms
Unused
Atoms
Sum of
Molar Mass
of Unused
Atoms
CH3CH2CH2OH
60.1
3C, 7H
43.1
HO
17.0
NaI
149.9
I
126.9
Na
23.0
H2SO4
98.0
-
0
2H, S, 4O
98.0
3C, 7H, I
170.0
HO, Na, 2H,
S, 4O
138.0
Total Atoms in
308.0
Reactants, 3C,
10H, 5O, Na, S, I
Atom Economy Example
Continued….
Percentage Atom Economy = (molar mass used atoms / molar
mass of all reactants) x 100
= (170.0/308.0) x 100
= 55.2%
Formula of
Reactants
Molar Mass Atoms used in
of Reactants Product
Sum of Molar
Mass of Used
Atoms
Unused
Atoms
Sum of Molar
Mass of
Unused
Atoms
CH3CH2CH2OH 60.1
3C, 7H
43.1
HO
17.0
NaI
149.9
I
126.9
Na
23.0
H2SO4
98.0
-
0
2H, S, 4O
98.0
3C, 7H, I
170.0
HO, Na, 2H, S,
4O
138.0
Total Atoms in 308.0
Reactants, 3C,
10H, 5O, Na,
S, I
% Atom Economy = (137/275) X 100 = 50%
“It is better to prevent waste than to
treat or clean
up waste after it is formed”
Chemical
Process
“The use of auxiliary substances (e.g. solvents,
separation agents, etc.) should be made
unnecessary
wherever possible, and innocuous when used”
“Energy requirements should be recognized for
their environmental impacts and should be
minimized.
Synthetic methods should be conducted at
ambient
pressure and temperature”
Heating
Cooling
Stirring
Distillation
Compression
Pumping
Separation
Energy Requirement
(electricity)
GLOBAL
WARMING
Burn fossil
fuel
CO2 to
atmosphere
Resource Depletion
• Renewable resources can be made
increasingly viable technologically
and economically through green
chemistry.
Carbondioxide
Biomass
Nanoscience
Solar
Waste utilization
Poly lactic acid (PLA) for plastics production
Polyhydroxyalkanoates (PHA’s)
The major uses of GREEN CHEMISTRY
•
•
•
•
•
Energy
Global Change
Resource Depletion
Food Supply
Toxics in the Environment
Energy
The
vast majority of the energy
generated in the world today is
from non-renewable sources that
damage the environment.
 Carbon


dioxide
Depletion of Ozone layer
Toxics
Energy
 Green

Chemistry will be essential in
developing the alternatives for energy
generation (photovoltaics, hydrogen, fuel
cells, biobased fuels, etc.) as well as
Global Change
 Concerns for climate change,
oceanic temperature, stratospheric
chemistry and global distillation can
be addressed through the
development and implementation of
green chemistry technologies.
Resource Depletion
Due
to the over utilization of nonrenewable resources, natural
resources are being depleted at an
unsustainable rate.
Fossil fuels are a central issue.
Resource Depletion
 Renewable
resources can be made
increasingly viable technologically and
economically through green chemistry.
Nanoscience & technology
 Solar

Pollution Prevention Hierarchy
Prevention & Reduction
Recycling & Reuse
Treatment
Disposal
Green chemistry
Not a solution to all environmental
problems But the most
fundamental approach to preventing
pollution.
• www.acs.org/education/greenchem
Green Chemistry in Action
• Most commonly used solvents are flammable
and volatile organic compounds which are
toxic.
• Some have significant environmental impact
and are associated with the deterioration of
the ozone.
• There has been a lot of research in finding
alternative solvents.
• One alternative is carbon dioxide.
Supercritical Carbon Dioxide cont…
• Carbon dioxide forms a supercritical fluid at a
pressure of 73atm and a temperature of 31°C.
• This relatively low temperature makes superficial
carbon dioxide easy to work with.
• Another useful feature is that its solvent properties
can be altered by making slight adjustments to
temperature and pressure.
• scCO2 is an environmentally friendly option also
because it can be obtained as a by-product from
other industries. It is also easy to recapture and
rescue.