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Presentation on theme: "GREEN CHEMISTRY PRESENTED BY CHAITANYA DHOKE (Ch09M002)"— Presentation transcript:


2 Environmental issues and problem Human society is constantly facing environmental issues and problems such as: 1. Ozone depletion, 2. Air pollution, 3. Global climate change, 4. Water and soil pollution, 5. Acid rain, 6. Depletion of natural resources, 7. and the Accumulation of hazardous waste. General perception: Chemical industry is responsible for all these.

3 Pollution control PrimarySecondary 1. Clean process ( Green Chemistry) 1. Exhaust clean up in mobile sources (3 way catalyst, SCR, HC trap, soot removal) 2. Clean fuels (HDS,HDN,HDM, use of renewable fuels) 2. Emitted gas clean up from stationary sources (SCR to reduce NO x ) 3. Catalytic combustion3. Clean up of liquid/solids/vapours from home and industries (ETP) 4. Alternatives to hazardous materials like CFC

4 Green chemistry (GC)

5 DEFINITION: Green Chemistry is the utilisation of a set of principles that reduces or eliminates the use or generation of hazardous substances, enhance the selectivity of the desired product. GREEN CHEMISTRY Material Hazards Risks Energy Cost Waste Reducing

6 Green chemistry principles: 1. Prevention of waste; E factor (kg of by products/ kg of products) should he small. 2. More atom efficient i.e. Maxim utilization of reactant atoms to desirable product. 3. Less hazardous synthesis. 4. Safer products. 5. Safer solvent. 6. Energy efficiency. 7. Renewable feedstock's. 8. Reduce derivatization. 9. Use of catalytic reactions. 10. Degradable products. 11. Better process monitoring. 12. Safer practices. Ref: Anastas and warner 1998

7 E factor in different industries

8 Advantage of green chemistry Conventional route for ethylene oxide production Atom utilization = 44/ 173 = 25 %. E factor = 129 / 44 = 2.93. Modern catalytic process for ethylene oxide production: Atom utilization = 100 %. 2

9 “ It is better to prevent waste than to treat or clean up waste after it is formed” Chemical Process

10 p-isobutyl acetopheneone 2-acetyl 6-methoxynaphthalene Acetyl compounds are used as intermediates in fine chemicals and pharmaceuticals Acylation of aromatic compounds is often carried out using mineral acids like AlCl 3 and acyl chlorides as reactants. Examples

11 Homogenous and heterogeneous mode for acylation Homogeneous AlCl3 >1 equivalent Solvent (recycle) Hydrolysis of products 85-95% yield 4.5 kg aqueous effluent per kg 12 unit operations Heterogeneous H-beta, catalytic & regenerable No solvent No water necessary >95% yield /higher purity 0.035 kg aqueous effluent per kg 3 unit operations Ref:Ratton S., Chem. Today (Chim. Oggi), March/April, 1998, 33

12 FRIEDEL-CRAFTS ACYLATION  Convectional acyl chloride route  Zeolite route using Anhydride  Preparing acyl chlorides from acids and acylation using mineral acids is environmentally unsound  Solid catalysts can be used to produce acyl compounds in a “green” manner using acid anhydrides that can be readily prepared.

13 al: studied acylation of toluene with acetic anhydride to give 4-methyacetophenone (MAP). Parameter studied:  Temp – 150 – 250 O C.  Catalyst – β zeolite.  Toluene: AA – 1-40.  TOS – 4 hrs. Reaction scheme

14 Effect of Reaction time, Temperture & toluene /AA ratio on MAP yield Ref: Botella. of catalysis 195 (2000), 161-168.

15 Beer et. al studied acylation of aromatics with carboxylic acids  Reactant- Anisole & octanoic acid.  Catalyst – zeolite ( BEA, FAU, USY)  monolith design. Reaction scheme

16 Diffusion effect: Ref: Beers et. al., Microporous and Mesoporous Materials 48 (2001) 279-284.

17 Effect of water removal and stability of catalysts: Ref: Beers et. al., Microporous and Mesoporous Materials 48 (2001) 279-284.

18 Wagholikar. et. al. studied acylation of anisole with C 6,C 8,C 10 acids Parameter studied  Catalyst- BEA,MOR,FAU.  Temperature-120-150 0 C.  Anisole: acid ratio =2-8  TOS= 6 hr.

19 Effects of various parameters Ref: Wagholikar, Applied Catalysis A: General 317 (2007) 250-257.

20 Problem statement Study the acylation of aromatic compounds with alaknoic acids or acid anhydrides to give ketone These ketones can be hydrogenated in another step using metal catalysts to produce alkyl aryl hydrocarbons. The project also aims to carry out acylation and hydrogenation in one step using bifunctional catalyst (i.e. metal site and acid site). Proposed catalysts: Metal site : Pt, Pd. Acid site : Zeolite, Sulfated Zirconia, Rare earth exchange, Clays

21 Reaction scheme for acylation of anisole with C 12 acid

22 Mechanism

23 Experimental conditions Reactants – a) Aromatic compounds { Anisole, Toluene, Benzene}. b) Long chain carboxylic acid { Dodecnoic acid (C 12 ), Oleic acid ( C 18:1 ), Steric acid (C 18 )}. Catalyst – H-β Zeolite (Si/Al= 25) cancined @ 450 o C. Reaction was carried out in reflux flask @ reflux condition and in parr reactor @ high temp under constant stirring condn.

24 Experimental conditions and results using H-β zeolite. Sr. NoReactantsConditions Conversion (%) Temp  C Amount of acid (mmol) Molar ratio (acid : aromatic) Catalyst weight (mg) Time (h) 1. C 12 acid / Anisole 150251:45006.03 2. C 12 acid / Toluene 150251:45006.02 3. C 12 acid / Benzene 120251:4500121.1 4. C 18 acid /Anisole 150181:650012.0- 5.C 18:1 acid /Anisole 150181:650012.0- Table 1. Conditions and results of acylation experiments

25 Preparation procedure adopted for SO 4 2− /ZrO 2 Dissolve 10 gm of ZrOCl 2.8H 2 O in distilled water. Add aqueous ammonia drop wise to maintain pH of 8 to get ppt. Wash ppt with distilled water and dry at 393K for 24h. Grind solid to fine powder and add 1M H 2 SO 4 for 30 min. Evaporate Excess water in water bath and dry in oven at 393K for 12h. Calcine sample at 923K for 4h in air. Ref:Reddy. et. al.Journal of molecular cat. A: chem. 237 (2005) 93-100

26 Thank you


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