Introduction to Green Chemistry: Principles, Applications, and Carbon Credits

1. Unit IV Part A Green Chemistry By. Prof. SharadaIshwarkarGWCET, Nagpur

2. GREEN CHEMISTRY • DEFINITION (P T Anastas & J C Warner) 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. • PRINCIPLES OR SIGNIFICANCE OR GOLES OR APPLICATION • 1. Prevention of waste/By-products • It is better to prevent the formation of waste than to clean up waste after it has been created.  • 2. High atom Economy • Designed such Synthetic methods which increase the use of all materials or reactants used in process to produce the final product.  • 3. Less Hazardous Chemical Synthesis • Designed such synthetic methods, which use and generate such substances that possess little or no toxicity which are harmful to people or the environment. 

3. 4. Designing of Safer Chemicals • Designed such Chemical products which affect their desired function and minimising their toxicity.  • 5. Use of Safer or most appropriate Solvents and Auxiliaries • Uses Safer or most appropriate Solvents and Auxiliaries (e.g., solvents or separation agents) in process whenever possible and innocuous whenever used. • 6. Design for Energy Efficiency • Designed such synthetic methods, which should be conducted at ambient temperature and pressure, due to which energy requirements for process which are recognised for their environmental and economic impacts should be minimised. • 7 Use of Renewable Feedstocks • Uses renewable raw material or feedstock rather than depleting whenever possible technically and economically practicable.

4. 8 Reduce Derivatives • Unnecessary derivatives (use of blocking groups, protection/de-protection, and temporary modification of physical/chemical processes) should be minimised or avoided if possible, because such steps require additional reagents and can generate waste products. • 9 Use of Catalyst • Catalytic reagents (as selective as possible) are superior to Stoichiometric reagents. • 10 Design for Degradation • Designed such chemical products, which are easily broken down into innocuous degradation products at the end of their function, so that they do not persist in the environment. • 11 Real-time Analysis for Pollution Prevention • Developed such analytical methods which allow for real-time, in-process monitoring and control prior to the formation of hazardous substances. • 12 Inherently Safer Chemistry for Accident Prevention • Select such substances in a chemical process which minimise the potential for chemical accidents, including releases, explosions, and fires.

5. CO2 AS SOLVENT OR SUPERCRITICAL CO2 • If the substance is placed at a temperature above the critical temperature Tc ( 310C for CO2) and critical pressure Pc (72.8 atm. for CO2), a supercritical fluid is obtained. In supercritical liquid, the CO2 molecules are pressed together due to high pressure so that they almost exist in both gas like and liquid like qualities. Due to this duel characteristic that provides the condition for extracting compounds with high degree of recovery in short period of time. Supercritical CO2 can dissolve wide range of polar and non polar compound • Tc - temperature above which a distinct a distinct liquid phase of the substance cannot exists, regardless the pressure applied. • Pc - the pressure at which a substance can no longer exists in gaseous state.

6. ADVANTAGES OF SUPERCRITICAL CO2 • a. Renewable, nontoxic, non-inflammable and inexpensive. • b. It can dissolve almost all types of solvents except hydrocarbons of higher MW. • c. Solubility of solutes more, which help to recover the solutes. • d. Due to its structure it replaces ultra-high purity water. APPLICATIONS OF SUPERCRITICAL CO2 • a. Solvent for organic reactions • b. Dry-cleaning • c. Mobile phase in HPLC • d. Decaffeinating • e. Dyeing of fabric • f. Important emerging refrigerant

7. CARBON CREDITS • Definition- a tradable certificate or permit representing right to emit one ton of CO2 or another green house gas equivalent to one ton of CO2. • This concept came to exist due to make aware about CO2 pollution. If through plantation one can remove 1 ton of CO2, such organization or industry has right to release 1 ton of CO2 or can sell the certificate and earn the money. • Carbon credit is apart of national and international attempts to control the green house gases. Carbon credit is also called as emission permit. • The Principle of carbon credits is to allow market mechanism to drives industrial and commercial processes in the direction of low emission of green house gases. • India and China are likely to be biggest seller to Europe.

8. Conclusion Green chemistryNot a solution to all environmental problems But the most fundamental approach to preventing pollution.

9. Thank you