What is Green Chemistry?

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Green Chemistry?

• 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

1. It is better to prevent waste than to treat or clean up waste after it is formed.

2. Synthetic methods should be designed to maximize the incorporation of all materials used in the process into the final product.

3. 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.

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.

12 Principles of Green Chemistry

Application of Green Chemistry in daily life1

• 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 life1

• 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 life2

Application of Green Chemistry in daily life2

• 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 life3

• 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 life3

• 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 chemistry1

• to develop reactions which can proceed in the solid state without the use of solvents

• e.g. formation of a cyclic adduct of trans-1,2-bis(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

2

• 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?

• 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 sterilizati

on 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

• 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

•1909 -1910 • The decaf coffee first arrived on the American scene around

• It involved steaming coffee beans with a brine (salt water) solution and then using benzene as a solvent to remove the caffeine.

Three main methods for decaffeination

1. Swiss Water Process2. Triglyceride process 3. CO2 Decaffination

Swiss Water Process

1. Soak the bean in pure water2. 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 Process4. The beans are immersed in the flavor-charged water

5. The water then passes through a carbon filter that traps the caffeine.

6. The flovour-charged water is now recycled.

7. Flavour-charged water flows back to the beans to remove more 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