Transcript What is Green Chemistry?

What is Green Chemistry?
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Green Chemistry
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• Sustainable chemistry
• Chemical research and engineering that encourages
the design of products
• Minimize the use and generation of hazardous
substances
• Focus on industrial applications
12 Principles of Green Chemistry
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3.
It is better to prevent waste than to treat or clean up
waste after it is formed.
Synthetic methods should be designed to maximize the
incorporation of all materials used in the process into the
final product.
Wherever practicable, synthetic methodologies should be
designed to use and generate substances that possess
little or no toxicity to human health and the environment.
12 Principles of Green Chemistry
4. Chemical products should be designed to preserve efficacy of
function while reducing toxicity
5. The use of auxiliary substances (e.g. solvents, separation
agents, etc.) should be made unnecessary wherever possible
and innocuous when used.
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. raw material or feedstock should be renewable rather than
depleting wherever technically and economically
practicable.
8. Reduce derivatives - Unnecessary derivatization (blocking
group, protection/ deprotection, temporary modification)
should be avoided whenever possible.
9. Catalytic reagents (as selective as possible) are superior to
stoichiometric reagents.
12 Principles of Green Chemistry
10. Chemical products should be designed so that at the end of
their function they do not persist in the environment and
break down into innocuous degradation products.
11. Analytical methodologies need to be further developed to
allow for real-time, in-process monitoring and control prior
to the formation of hazardous substances.
12. Substances and the form of a substance used in a chemical
process should be chosen to minimize potential for chemical
accidents, including releases, explosions, and fires.
Application of Green Chemistry in daily life
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• 100% carbon dioxide blowing agent for polystyrene foam
production (1996) produces CFC and other ozone-depleting
which causes a serious environmental hazard It was
discovered that supercritical carbon dioxide works equally as
well as a blowing agent
Application of Green Chemistry in daily
life
1
• without the need for hazardous substances
allow the polystyrene to be more easily
recycled
• the CO2 released in the process is reused
from other industries, so the net carbon
released from the process is zero.
Application of Green Chemistry in daily
life
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Application of Green Chemistry in daily
life
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• Glycerine to propylene glycol (2002)
• waste glycerin from biodiesel production is
converted to propylene glycol
• through the use of a copper-chromite catalyst
• to lower the required temperature of conversion
• raise the efficiency of the distillation reaction
• cheap
Application of Green Chemistry in daily
life
3
• enzyme interesterification process (2005)
• To develop a clean, enzymatic process for the
interesterification of oils and fats by
interchanging saturated and unsaturated
fatty acids
Application of Green Chemistry in daily
life
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• produce commercially viable products
without trans-fats
• beneficial to the human health
• reduce the use of toxic chemicals and water,
prevents vast amounts of byproducts,
• reduces the amount of fats and oils wasted
Application of Green Chemistry in chemistry
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• to develop reactions which can proceed in
the solid state without the use of solvents
• e.g. formation of a cyclic adduct of trans-1,2bis(4-pyridyl)ethylene is directed by
dihydroxybenzene in the solid state in the
presence of UV light
• in the presence of UV light
Application of Green Chemistry in
chemistry
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• Atul Kumar has developed an efficient and
green method for the synthesis of
tryptanthrin - employing β-cyclodextrin as a
catalyst in aqueous media at room
temperature
• tryptanthrin
•β-cyclodextrin
What is supercritical carbon dioxide
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• a fluid state of carbon dioxide where it is held at or above its
critical temperature and critical pressure.
• adopt properties midway between a gas and a liquid
expanding to fill its container like a gasbut with a density
like that of a liquid
Supercritical carbon dioxide is a good
solvent. Why?
•non toxic and non-flammable
•separation of the reaction components from the starting
material is much simpler than with traditional organic
solvents, merely by allowing it to evaporate into the air
recycling it by condensation into a cold recovery vessel.
•relatively low temperature of the process and the high
stability of CO2, which allows most compounds to be extracted
with little damage or denaturing.
Application of supercritical carbon dioxide
in daily life
• remove the caffeine in coffee when they are sprayed
with water at high pressure
• a more environmentally friendly solvent for dry
cleaning
• produce micro and nano scale particles, often for
pharmaceuticaluses,
• used in the foaming of polymers. Many corporations
utilize supercritical carbon dioxide to saturate the
polymer with solvent (carbon dioxide).
• an important emerging natural refrigerant,
being used in new, low carbon solutions for
domestic heat pumps
• enhance oil recovery in mature oil fields
• an effective alternative for terminal
sterilization of biological materials and
medical devices
• used as the extraction solvent for creation of
essential oil and other herbal distillates.
What is caffeine?
Structure of caffeine
1,3,7-trimethyl-1H-purine-2,6(3H,7H)-dione
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Molecular formula C8H10N4O2
Appearance Odorless, white needles or powder
Density 1.23 g/cm3, solid
Melting point 227–228 °C, 500-501 K (anhydrous)
234–235 °C, 507-508 K (monohydrate)
• Boiling point 178 °C, 451 K, 352 °F (subl.)
Caffeine
• Caffeine is a bitter, white crystalline xanthine
alkaloid and psychoactive stimulant.
• found in varying quantities in the seeds, leaves, and
fruit of some plants, where it acts as a natural
pesticide that paralyzes and kills certain insects
feeding on the plants.
Caffeine
• commonly consumed by humans in infusions extracted from
the bean of the coffee plant and the leaves of the tea bush,
as well as from various foods and drinks containing products
derived from the kola nut.
• Other sources include yerba maté, guarana berries, and the
yaupon holly.
• In humans, caffeine acts as a central nervous system (CNS)
stimulant, temporarily warding off drowsiness and restoring
alertness.
Health effects of caffeine
• precise amount of caffeine necessary to produce
effects varies from person to person depending on
body size and degree of tolerance to caffeine.
• An oral dose of 200 mg caffeine appears to decrease
reaction time by approximately 4 percent within 30
minutes, approximately 15 percent in 30 to 60
minutes and 18 percent in 60-90 minutes.
• does not eliminate the need for sleep but only
temporarily reduces the sensation of being tired.
Health effects of caffeine
• Studies have shown that increased caffeine
consumption is associated with less severe liver
injury among those at high risk for liver disease,
such as those with alcoholism, obesity, or
hemochromatosis. The mechanism by which this
occurs is not known.
Overuse of caffeine
• lead to a condition known as caffeinism.
• Caffeinism usually cause a wide range of unpleasant physical
and mental conditions including nervousness, irritability,
anxiety, headaches, respiratory alkalosis, and heart
palpitations.
• increases the production of stomach acid and so high usage
over time can lead to peptic ulcers, erosive esophagitis, and
gastroesophagea reflux disease.
• Increase the toxicity of certain other drugs, such as
paracetamol.
History of removing caffeine from coffee beans
• 1903
• a German coffee merchant, Ludwig Roselius, and his partner
Karl Wimmer created a system
• It involved steaming coffee beans with a brine (salt water)
solution and then using benzene as a solvent to remove
the caffeine.
•1909 -1910
• The decaf coffee first arrived on the American scene
around
Three main methods for decaffeination
1. Swiss Water Process
2. Triglyceride process
3. CO2 Decaffination
Swiss Water Process
1. Soak the bean in pure water
2. The water extracts both the coffee flavour solids and the caffeine
form the beans.
3. The bean are discarded. The caffeine is removed using a carbon
filter, leaving just water, super saturated with coffee solids.
Swiss Water Process
4. The beans are immersed
in the flavor-charged water
7. Flavour-charged water
flows back to the beans to
remove more caffeine
6. The flovour-charged
water is now recycled.
5. The water then
passes through a
carbon filter that
traps the caffeine.
Finally the decaffeinated beans are removed from the water. They
are then dried, Cleaned, polished, bagged and shipped.
A typical green bean, after decaffeination, is
composed of:
http://www.youtube.com/watch?v=xIjfiD7dl9c
03:08- 05:27
Triglyceride process
• soak green coffee beans in a very hot water/coffee
solution
• caffeine is extracted from the beans.
• The half cooked beans are moved to a vat with
coffee oil that came from used coffee ground.
• The beans are super heated again
• Triglycerides in the oil remove the caffeine, but not
the java flavor.
• The beans are heat dried now decaffeinated and
ready to make coffee.
CO2 process
• This process is technically known as supercritical
fluid extraction.
• the caffeine is stripped directly from the beans by a
highly compressed semi-liquid form of carbon
dioxide.
• Pre-steamed beans are soaked in a bath of
supercritical carbon dioxide at a pressure of 73 to
300 atmospheres.
• After a thorough soaking for around ten hours, the
pressure is reduced, allowing the CO2 to evaporate,
or the pressurized CO2 is run through either water
or charcoal filters to remove the caffeine.
• The carbon dioxide is then used on another batch of
beans. This liquid works better than water because
it is kept in supercritical state near the transition
from liquid to gas, combining favorable diffusivity
properties of the gas with increased density of a
liquid.
Advantage
• This liquid works better than water because it is kept in
supercritical state near the transition from liquid to gas,
combining favorable diffusivity properties of the gas with
increased density of a liquid. This process has the advantage
that it avoids the use of potentially harmful substances.
THE END