Group 7 Green Chemistry and Decaffeination by supercritical carbon dioxide

1. Group 7Green Chemistry and Decaffeination by supercritical carbon dioxide Mimi Chan(1) Christine Chan(3) Jo Ngan(27) Fiona Wong(32) Candy Wong(34)

2. What is Green Chemistry? • Philosophy of chemical research and engineering • Minimize the use and generation of hazardoussubstances

3. Principles of Green Chemistry • Design safer chemicals and products • Design less hazardous chemicals synthesis • Use catalysts, not stoichiometric reagents • Maximize atom economy

4. Principles of Green Chemistry • Use safer solvents and reaction conditions • Increase energy efficiency • Design chemicals and products to degrade after use • Minimize the potential for accidents

5. Application of Green Chemistry in Daily life • Pesticides • Dichlorodiphenyl trichloroethane (DDT) is one of the most well-known insecticides during World War II. • Caused a significant environmental damage. • Banned in the United States in 1973.

6. Application of Green Chemistry in Daily life • Replaced by organophosphates, which degrade rapidly in the environment, but are much more toxic to mammals. • Use compounds that destroy only the target organisms. For example, an insecticide that mimics a hormone used only by molting insects; activating the natural defense mechanism against pests or diseases.

7. Application of Green Chemistry in Daily life • Polymers • Synthetic polymers or plastics are everywhere. • More than 60 million pounds of polymers are produced in the US each year. • To decrease petroleum consumption, biomass, a renewable resource is investigated to produce polymers:

8. Application of Green Chemistry in Daily life • NatureWorks polylactic acid (PLA), a naturally occurring lactic acid which is produced from the fermentation of corn and is biodegradable. • PLA can also be easily recycled by conversion back into LA.

9. Application of Green Chemistry in Daily life • Computer Chips • Requires excessive chemicals,water, and energy. • Use supercritical carbon dioxidein one of the steps in chip preparation • Reduces the quantities of materials needed to produce chips.

10. Application of Green Chemistry in Daily life • Dry Cleaning • Perchloroethylene is used most often to dry clean clothes • Poses hazards to the environment and is a suspected human carcinogen. • Condensed phase carbon dioxide,a combination of CO2 and a surfactant is used

11. What is supercritical carbon dioxide? • Carbon dioxide having its gas and liquid state at the same time. Phase diagram of CO2

12. Supercritical carbon dioxide is a good solvent. Why?    • Has similar densities to that of liquids, • Viscosities and diffusivities are closer to that of gases. • Can diffuse faster in a solid matrix than a liquid • Possess a solvent strength to extract the solute from the solid matrix.

13. Supercritical carbon dioxide is a good solvent. Why?    • As solvation strength of a supercritical fluid is directly related to the fluid density. • Thus, the solubility of a solid can be manipulated by making slight changes in temperatures and pressures.

14. Once the critical temperature and pressure have been reached the two distinct phases of liquid and gas are no longer visible. • The phase boundary can no longer be seen. • One homogenous phase called the “supercritical fluid" phase occurs which shows properties of both liquids and gases.

15. Here we can see the separation, phases of carbon dioxide. The phase. • Boundary is easily observed.

16. With an increase in temperature, the liquid expands, so its density decreases. • At the same time, more liquid vaporizes, so the density of the vapor increases. • The phase boundary begins to diminish.

17. Increasing the temperature further causes the gas and liquid densities to become more similar. • The phase boundary is less easily observed.

18. Characteristics of supercritical CO2 • Adopt properties midway between a gas and a liquid. • Can diffuse through solids like a gas, and dissolve materials like a liquid • Readily change in density upon minor changes in temperature or pressure when close to the critical point. • Suitable as a substitute for organic solvents

19. Caffeine • a bitter, white crystalline xanthine alkaloid • a psychoactive stimulant drug. • a central nervous system (CNS) stimulant • have the effect of temporarily warding off drowsiness and restoring alertness.

20. History of Decaffeination • Initial attempts: • Apply solvents to already roasted coffee beans. While it was easier to remove the caffeine from a roasted bean, the flavor and aroma were also adversely affected. • In subsequent efforts, green coffee beans were broken or ground so that the solvents could better extract the caffeine. However, pre-ground coffee proved too difficult to adequately roast. • Modification: • Steam coffee beans so that they would expand, then extract much of the caffeine by applying benzene. • As the health effects of benzene became better known, other solvents replaced benzene in the decaffeination process.

21. Methods of decaffeinating coffee • Supercritical gases (Supercritical CO2 method) • Chemical solvents (Solvent method) • Water method (Swiss Water Process)

22. A) Supercritical gases (Supercritical CO2 method)

23. Coffee beans, water and carbon dioxide are mixed to create the sparkling water. • The carbon dioxide attracts all the mobile caffeine molecules. • Caffeine is then extracted from CO2 using activated carbon filters.

24. B) Chemical solvent decaffeination • Green beans are treated with steam, under pressure. • Swells the beans, increasing their surface area and making the caffeine easier to remove. • Extraction of the caffeine by a solvent, again under pressure, at a temperature close to the boiling point of the solvent.

25. B) Chemical solvent decaffeination • Ideally, the solvent should remove caffeine selectively. • After decaffeination, only minute traces of the solvent are left in the coffee.

26. B) Chemical solvent decaffeination • The safety of solvents used in decaffeination • Tested in animal and human studies;reviewed by government scientific authorities. • Solvents in current use which pass these stringent criteria includedichloromethane and ethyl ethanoate.

27. B) Chemical solvent decaffeination Dichloromethane • Relatively low boiling point (40° C) • Maybe harmful and possibly carcinogenic Ethyl ethanoate • Is used as flavouring agents in foods. • Occurs naturally in many fruits at levels higher than the traces found in decaffeinated coffee.

28. C) Water method

29. Principles of decaffeination using supercritical carbon dioxide • Decaffeination can be classify as one of the Supercritical Fluid Extraction(SFE). • Separate one compoundfrom while using supercritical CO2 as the extracting solvent. • Extraction is usually from a solid matrix, but can also be from liquids.

30. Is the use of supercritical carbon dioxide in decaffeination is a green chemistry? • Eliminate harmful residual solvents in the products, like methylene chloride produced while using Chemical solvent decaffeination (previously mentioned) • An ideal substitute for many hazardous and toxic solvents • Extracts Caffeine by direct contact method without using chemicals.

31. Is the use of supercritical carbon dioxide in decaffeination is a green chemistry? • The byproducts are natural and a 100% recyclable. • CO2 is not producedin thesupercritical carbondioxide process. Existing CO2 is used. There is NO addition to the greenhouse effect.

32. Applications of supercritical carbon dioxide in daily life • Solvent for organic compounds present in aqueous salt solutions • Polymerization in supercritical carbon dioxide • Assisted, silicone-modified wood for enhanced fire resistance • Synthesis metal-polymer composites manufactured via metal vapor

33. Applications of supercritical carbon dioxide in daily life • Natural product extraction(decaffeination) • Dry cleaning • Extract thermally labile food components

34. Q&A Section This is the end of our sharing.