green chemistry a synthetic chemist's perspective
TRANSCRIPT
Hermenegildo GarciaDepartment of Chemistry
D2Q-996 387 7807
(ext 73441 y 78572)[email protected]/herme
Green Chemistry
How to pass the course?• Attendance to class is mandatory
•You can miss one class max.• To perform exercises and homework
•Assignment•Correct exercises•Present in due time•Public presentation (30 min)
•Written exam• Volonteers
4
7
10
Assignment List
• History• Examples of novel green chemistry processes • Presidential Green Chemistry Challenge award
winners• Propose practical demonstrations• Renewable feedstocks• EPA grants• Search for reviews and literature reports• Search for web pages and electronic addresses• Assistance to prepare new class material
Actions aiming at Green Chemistry
Academia• Courses and training• Research in new processes
Goverment•Laws and regulations•Control•Funding and promotion
Industry• Development of new processes• Development of new products • New renewables feedstocks• Safe operation
General public• Information• Good practices• Support extra costs
The ACS/EPA Cooperative Agreement
• What is the EPA?• What is ACS?• EPA/ACS collaboration
Propose nominations to the Presidential Green Chemistry Challenge Awards Program
Highlights the concerns with current products and processes
Presents a green chemistry solutionReal-World Cases in Green Chemistry
ACS Activities
Earth Day ProgramGreen chemistry in the curriculum
(books)Green chemistry summer schoolNational Chemistry WeekInteractive Teaching Units
Europe and Japan• Royal Society of Chemistry• Venice (7th Summer school in green
chemistry)• Barcelona (Green Chemistry PhD course)• European Commission (Cost Actions)• York and other European Universities• Japan is developing very strong initiatives
Can the Chemistry be Dirty?
Atmospheric pollution• Green house effect and energy consumption• Ozone layer depletion• Photochemical smog• Smoke (NOx and SOx)
Aqueous pollution• Fertilizers, pesticides, insecticides• Industrial waste waters• Solvents• Detergents and urban waste waters
Solid pollution• Industrial soils• Nuclear and radiactive wastes• Chemical residues
Examples of Chemical Products of the 20th Century
Thalidomide.DDT.CFCs.Endocrine disruptors.Bioaccumulating substances.Persistent/non-biodegradable
materials.
Why the chemistry is dirty?• Provides energy• Provides materials (plastics, paper, etc)• Provides commodities (sprays, detergents,
paints, dyes)• Provides fertilizers, insecticides, pesticides• Provides drugs and pharmaceuticals
• Social demand• Social complain
Growth of Legal Regulation
AMFAARPAA
AJAAS BCAA
ES AA-AECAFFRAA
FEAPRAIRA
NWPAACODRA/NMS PAA
FCRPAMMPAA
120
110
100
90
80
70
60
50
40
30
20
10
0
1870 1880 1890 1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000
EPACTFFCACERFACRAA
PPAPPVAIEREAANTPAGLCPAABACZARAWRDAEDPOPARECACAAAGCRAGLFWRAHMTUS ANEEA
S DWAAS ARA
BLRAERDDAAEAWANOPPAPTS AUMTRCAES AAQGANCPA
TS CAFLPMARCRANFMACZMAA
NEPAEQIACAAEPAEEAOS HAFAWRAANPAA
FRRRPAS OWADPA
WS RAEARCFHS A
AQA
NAWCA
WQA
NWPA
MPRS AAARPA
HMTA
FCMHS A
NHPAWLDA
FWCAAFWA
AEA
AEPA FIFRA PAA
FAWRAMBCANPSWA
IANBRA
AARHAYA
TAFWCA
BPA
NLRAWPA
AQAFOIA
WRPAAFCA
FHS ANFMUA
BLBAFWPCAMPRS A
CZMANCA
FEPCAPWS AMMPA
ES ATAPA
RCRAAWLDI
APAS WDA
CERCLACZMIA
COWLDAFWLCA
MPRS AACAAACWA
S MCRAS WRCAS DWAA
Num
ber
of
Law
s
What is Green Chemistry?
Benign Disposal
Recycle/Re-use
Reduce -
Replace - Hazardous materials, processesInefficient processesNon-sustainable components
Chemical usageEnergy usage
•Environmentally friendly processes•Sustainability
Green Chemistry Technologies and Solutions
• What is Green Chemistry? •Chemistry to provide commodities being environmentally friendly and sustainable
• How do we know what is Green?
• A dip into the Clean/Green technology Pool with some examples.
“When you can measure what you are speaking about, and express it in numbers, you know something about it; but when you cannot measure it, when you cannot express it in numbers, your knowledge is of a meagre and unsatisfactory kind; it may be the beginning of knowledge, but you have scarcely, in your thoughts, advanced to the stage of science” William Thompson, Lord Kelvin, (1891)
How do we know what is Green?Metrics in Green Chemistry
“If you don’t keep score then you are only practising”
Metrics in Green Chemistry
How do we know what progress we are making?
⇒ E - FactorAmount of waste/kg product:
Product tonnage E Factor
Bulk Chemicals 104-106 <1 - 5
Fine chemical Industry 102-104 5 - >50
Pharmaceutical Industry 10-103 25 - >100
R.A. Sheldon, Chem & Ind, 1997,12
Metrics in Green ChemistryPreparation of 2-methoxypropane-1,3-diol from glycerol
HO OHOH
TrO OTrOH
TrO OTrOMe
HO OHOMe
TrO OTrOH
TrO OTrOMe
2Et3N
2AcOH
[92]
[106]
+ 2TrCl + + 2Et3N.HCl
+ MeI + Et3N + Et3N.HI
+ + 2TrOAc
[278.5] [101] [137.5]
[142] [229]
[60] [302]
Assuming 100% yields, no reaction or work-up solvents and no reagent excesses 1 kg glycerol produces 1.15 kg 2-methyl ether and 12.04 kg of waste!
Atom EconomyAtom economy =
MW of desired productΣ MWs of all substances produced
•Diels-Alder Reaction
+
O O
100% Atom economy
•Wittig Reaction
•O
+ CH2Ph3P+ _ C H•2
+ Ph3 P=O
35% Atom economy
Catalysis
Chemical recycling Membrane
reactors
Safer reactions and reagents-
New ChemistryRenewable Feedstocks
Alternative Solvents
Innovative Engineering
12 Principles of Green Chemistry • Prevent waste: Design chemical syntheses to prevent
waste, leaving no waste to treat or clean up. • Design safer chemicals and products: Design chemical
products to be fully effective, yet have little or no toxicity.
• Design less hazardous chemical syntheses: Design syntheses to use and generate substances with little or no toxicity to humans and the environment.
• Use renewable feedstocks: Use raw materials and feedstocks that are renewable rather than depleting. Renewable feedstocks are often made from agricultural products or are the wastes of other processes; depleting feedstocks are made from fossil fuels (petroleum, natural gas, or coal) or are mined.
• Use catalysts, not stoichiometric reagents: Minimize waste by using catalytic reactions. Catalysts are used in small amounts and can carry out a single reaction many times. They are preferable to stoichiometric reagents, which are used in excess and work only once.
• Avoid chemical derivatives: Avoid using blocking or protecting groups or any temporary modifications if possible. Derivatives use additional reagents and generate waste.
• Maximize atom economy: Design syntheses so that the final product contains the maximum proportion of the starting materials. There should be few, if any, wasted atoms.
• Use safer solvents and reaction conditions: Avoid using solvents, separation agents, or other auxiliary chemicals. If these chemicals are necessary, use innocuous chemicals.
12 Principles of Green Chemistry
• Increase energy efficiency: Run chemical reactions at ambient temperature and pressure whenever possible.
• Design chemicals and products to degrade after use: Design chemical products to break down to innocuous substances after use so that they do not accumulate in the environment.
• Analyze in real time to prevent pollution: Include in-process real-time monitoring and control during syntheses to minimize or eliminate the formation of byproducts.
• Minimize the potential for accidents: Design chemicals and their forms (solid, liquid, or gas) to minimize the potential for chemical accidents including explosions, fires, and releases to the environment.
12 Principles of Green Chemistry
Pharmaceutical ApplicationsTraditional synthesis of ibuprofen
(CH3CO)2O AlCl3
O
ClCH2CO2C2H5
NaOC2H5
O CHCO2C2H5
H+
H2O
CHO
H2NOH
CH NOH
CN CO2H
Ibuprofen
Pharmaceutical Applications
Alternative synthesis of ibuprofen
(CH3CO2)O HF
O
H2catalyst
CO2H
Ibuprofen
OH
CO, Pd
BHC Company
Redesign of the Sertraline Process
TiCl4/ MeNH2
ClCl
NMe
ClCl
NMe
ClCl
NMeCl
Cl
O
ClCl
NMe
MeNH2EtOH
ClCl
NMe
ClCl
NMe
EtOAcHCl
EtOAcHCl
ClCl
NMe
ClCl
NMe
toluene/hexanesTHF
Pd/C, H2
+ TiO2+ MeNH4Cl
(D)-mandelic acidEtOH
"imine"isolated
racemis mixture cis and trans isomers
Sertraline Mandelateisolated
Sertralineisolatedfinal product
"imine" not isolated
racemic mixture not isolated
PdC/CaCO3H2/EtOH
MeOH rex
(D)-mandelic acidEtOH
Sertralineisolated final product
Sertraline Mandelateisolated
+ H2O
Alternative Synthetic PathwaysSodium iminodisuccinate
Biodegradable, environmentally friendly chelating agent
Synthesized in a waste-free processEliminates use of hydrogen cyanide
Bayer Corporation and Bayer AG2001 Alternative Synthetic Pathways Award Winner
O
O
O
NaOH NH3 ONa
ONaNaO
NaON
H
O O
O O
New Chemistry: Synthesis of 4-ADPA
Traditional Chemistry
Organo-halogens used.
Hazardous Solvent used.
High Waste levels.
Green ChemistrySafer.No Organo-halogens. Waste Minimised -74% less organic, 99% less water.Reusable catalyst employed.Reduced Cost.
Starting Material: Aniline
Product: 4-ADPA
Monsanto’s new route: rubber antidegradant130,000 M tonnes/annum
NH
NH2
NH2
Catalysis
Zeolites as Alternatives to Classical Routes
• Alumino-silicates
• 3D crystalline structure
• Uniform pore size
• Green applications in
> Catalysis
> Water treatment
> Remediation
> Odour control
Zeolites: Chemical Composition
Mx/n x+ [AlxSiyO2 (x + y )]
x- z H2O
Organic or inorganicExchangeableAcid Zeolites H+
Control:• during synthesis• after synthesis
PRIMARY STRUCTURE
VariableThermally reversible
y/x between 1 and ∞number of countercationshydrophylicity
Zeolites:Microporous Solids
SUPRAMOLECULAR CHEMISTRY
Molecular SievesMicroscopic ReactorReaction CavityMolecular Pockets
small medium large
Erionita ZSM-5
VPI-5
MCM-41
8 Ox10 Ox
12 Ox
18 Ox
Mesoporous
Pore size
20
10
30
ß, Y, ž
extra large
Pore
Diam
eter (
Å)
• More than 30 natural zeolites• More than 300 synthetic zeolites
SOME COMMON TOPOLOGIES
Faujasite(zeolites X and Y):tridirectional,large pore (13 Å)
BEA(zeolite Beta):tridirectional,large pore (12 Å)
Pentasil(silicalite and ZSM-5):bidirectional,medium pore (5.4X5.6 Å2)
MCM-41:unidirectional,mesoporous (20 Å)
Zeolite Particles by SEM
ADVANTAGES OF ZEOLITES AS HOSTS
• WELL DEFINED SOLIDS• SYNTHETIC MATERIALS
– REPRODUCIBILITY BETWEEN BATCHES– CONTROL OF CHEMICAL COMPOSITION – LARGE AMOUNTS g ⇒ Ton
• THERMAL AND CHEMICAL STABILITY• LARGE VARIETY
– SIZE AND GEOMETRY OF MICROPORES• OTHERS:
– ACTIVE SITES– TRANSPARENT TO UV RADIATIONS
ACID ZEOLITES:H+ AS CHARGE BALANCING CATION
• CASE OF ZEOLITE Y (POST-SYNTHETIC EXCHANGE)
NaY NH4 Y HY
NH4+
Na+
>500o
NH3
• CASE OF ZSM-5 (AS-SYNTHESIZED SAMPLES)
PROPERTIES:•CONTROL OF THE POPULATION OF ACID SITES: ONE SITE EACH FRAMEWORK Al•ACID STRENGTH DISTRIBUTION•SUPERACIDIC BEHAVIOR AT HIGH TEMPERATURES•ALSO LEWIS SITES
SiO
Al
HOO
O
OOO
+ -o>500
NPr4 ZSM-5 HZSM-5
NPr 3 + CH2 =CH CH3
Zeolites and Petrochemistry
• Fluid Catalytic Cracking– Conversion of Gas Oil into Gasoline
• Reforming– Increase of octane number (Quality of gasoline)
• Alkene Alkylation– Gasoline with high octane number
Catalysis: Zeolites
Shape selectivity allows only p-xylene to pass through
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+
Disproportionation of Toluene Using HZSM5
Solvent Replacement in Green Chemistry
• Volatile organic solvents are the normal media for carrying out organic syntheses and extractions - usage £4,000,000,000 p.a.
• Also used in products- paints, varnishes, cleaning agents, adhesives
• VOC’s causing considerable environmental concern! (Global warming/Ozone Depletion)
Benzene
• Excellent solvent but it is a Genotoxic human carcinogen• Limit in drinking water of 5ppb(US EPA)• In 1990 Perrier water found to have 12- 20ppb (cigarette smoke has 2000 times more benzene than this) - 160 million bottles withdrawn• EU limit in petrol 5% before 2000, now <1%
Solvent Replacement in Green Chemistry
Solvent Replacement in Green Chemistry
Perchoroethylene CCl2CCl2:• a suspected human carcinogen• main use in dry cleaning(85% of all solvents)• also found in printing inks, typewriter correction fluid and shoe polish
Halogenated Solvents
Dichloromethane CH2Cl2: • a suspected human carcinogen• widely used in synthesis and extractions• extraction of caffeine from coffee (<10ppm residue)
Carbon Dioxide
scCO2 is inexpensive, non-flammable and non-toxic.
Current applications include:• Decaffeination of coffee -replacing dichloromethane
• Dry Cleaning-replacing perchloroethylene.
Solvent Replacement in Green Chemistry
220.6374.0Water
48.832.3Ethane
73.831Carbon dioxide
Critical pressure(Bar)
Critical temperature(oC)
Compound
CO2 for Dry Cleaning
Dry Cleaningcurrent process uses perc
(perchloroethylene), a suspected carcinogen and groundwater contaminant
new process uses liquid carbon dioxide, a nonflammable, nontoxic, and renewable substance
Other solvents
• Perfluorinated solvent– Fluorous media
• Ionic Liquids• Water• Solventless reactions
– High conversions are needed
Perfluorinated solvents
P SiR1
R2
R3
SiR1
R2 R3
SiR1
R2
R3
R1, R2, R3: CH3 or -CH2CH2CnF2n+1
fluorinated triarylphosphines
N
N
N
NCnF(2n+1)
CnF(2n+1)F(2n+1)C
F(2n+1)C
fluorinated cyclam
Ionic LiquidsN N
NRR
R
+ +
An- An-
An-: PF6-, BF4
-, Cl-, etc.
N,N'-dialkylimidazoliums N-alkylpyridinium
AlCl4- AlCl3 Al2Cl7
-Cl-AlCl3
Real-World Cases: Microbes as Catalysts
Synthesis of adipic acid and catechol from renewable feedstocks using genetically modified E. coli
ApplicationsCatalysis/biocatalysisRenewable feedstocksWaste water remediation
Catalysis
Activity + selectivity, higher throughput with less waste, less energy
Propeneamide is the first bulk chemical manufactured using an industrial biotransformation:
The active enzyme is nitrile hydralase in whole cells of Rhodococcus rhodochrous, immobilised on
poly(propeneamide) gel
NNH2
O
5 degrees CpH 7.599.99% Yield
Catalysis
Membrane Technology
Extractive Membrane Bioreactor
BI
OFILM
MEMBRANE
PollutantsDissolved OxygenNutrients
Attachment
BiomediumDetachment
Wastewater
Membrane Technology
Extractive Membrane Bioreactor
New Stripper-BioScrubber plant on site at Atofina Widnes
(Project initiated in March 2000)
Removals of benzene or toluene from 500-1000 mg L-1 to less than 1ppm from point source waste stream
Membrane Separations in Green Chemical Technology
Biotransformations
Nonporous membrane
Organic Phase
C
P
R R
P
R = ReactantP = Product
Aqueous Phase
Whole cells or enzymes as biocatalysts
Membrane Bioreactor for Biotransformations
Nanoporous membranes• Is it possible to filtrate molecules?
SiMe
MeO Si
Me
MeO Si
Me
MeO Si
Me
Me
H SiMe
MeO Si
Me
MeO Si
Me
MeO Si
Me
MeH
CH2CH2 H
SiMe
MeO Si
Me
MeO Si
Me
MeO Si
MeO Si
Me
MeO Si O
Me
MeSiMe
MeH Si
Me
MeO Si
Me
MeO Si
Me
MeO Si
H
MeO Si
Me
MeO Si O
Me
MeSiMe
MeH
m
BA
catalyst
n n' n n'
+
a) No-crosslinked PDMS polymer
A H B H
n
(linear PDMS)
b) Crosslinked PDMS polymer
catalyst
+
CH2CH2 H
(crosslinked PDMS)
BA
CH2CH2
HB
CH2CH2
H
A
Nanoporous membranes to filtrate molecules
Hydrophilicphase
H2O2
H2O2
H2O2
PDMS membrane
H2O
H2O
Hydrophobicphase
Nanoporous membranes to filtrate molecules
O
R(R and S)
*Organic phase
Aqueous phase
Aqueous phase
H2O
H2OHO OH
R*
O
R*
HO OH
R*
Nanoporous membranes to filtrate molecules
ZSM-5 continuous film
Nanopores of Anodisk
N N
O
tBu
But
But
tBuCo
OAc
Renewable Resources
• Biodiesel– Synthesis of biodiesel from vegetable oil– Properties of biodiesel– Potential of biofuels
Polylactic Acid
Manufactured from renewable resources Corn or wheat; agricultural waste in future
A new thermoplastic polymer family based on polylactic acid developed by Cargill Dow 144,000 tpa plant built in Nebraska USA Potential market approaching 500,000 metric
tons per year. Uses 20-50% fewer fossil fuels than conventional
plastics PLA products can be recycled or composted
Cargill Dow
Designing Safer ChemicalsCationic electrodeposition coatings
containing yttriumProvides corrosion resistance to
automobilesReplaces lead in electrocoat primersLess toxic than lead and twice as effective
on a weight basis
PPG Industries2001 Designing Safer Chemicals Award Winner
Alternative ReagentsChlorine-free wood pulp bleaching TAML catalysts activate hydrogen peroxide Eliminates formation of chlorinated organics
Collins, Carnegie Mellon University
HO
H
N
N
N
N
O
O
FeIII
O
O
X
X
Cat+
_
Cat+ = Li+, [Me4N]+, [Et4N]+, [PPh4]+
X = Cl, H, OCH3
Agrochemicals
Pesticides• Insecticides (wide spectrum, juvenile and sexual
hormones traps)• Fungicides• Herbicides (natural defense)• Rodenticides
Cl
CO
Cl
ClCl
HH+ ClCl
Cl
Cl Cl
+
ClCl
Cl Cl
-HCl
Pesticide generation
1. First Generation Pesticides: toxic metals.
2. Second Generation Pesticides: synthetic organic pesticides e.g. chlorinated hydrocarbons such as persistent DDT.
3. Nonpersistent pesticides (e.g. malathion, aldicarb).
4. Pheromones and insect hormones
DIELDRINALDRIN
4.- PESTICIDAS CLORADOS
Cl C C
H ClCl
Cl
Cl
ClCl
ClCl
Cl
Cl
Cl ClCl
Cl
ClCl
Cl
Cl ClCl
Cl
ClCl
O
Cl ClCl
Cl
ClCl
CLORDANO
DDT LINDANO
•Activity against carbonic anhydrase enzyme
Pest resistance and Biomagnification• Total impact of a pesticide depends on 1) toxicity, 2)
dosage, 3) location • Pests develop resistance, may have far reaching
effects, and desirable insects also impacted.• Resurgences – pest population recovers and explodes• Secondary Pest Outbreaks – non-pests become pests
as loose natural enemies, gain resistance to pesticides• Biomagnification: multiplying effect of
bioaccumulation through the food chain. Chemicals accumulate in lipids
Alternative Pest Control Methods i. Control by natural enemies: lady bugs
v. Cultural control: non-chemical alteration of environmental factors e.g. hygiene, crop rotation
vi. Natural Chemical Control (isolate, ID, synthesize then use insects own hormones or pheromones to disrupt its life cycle. Non-toxic and specific. Sex pheromones can be used to lead insects into traps, or confuse them.
vii. Genetic Control: breed resistance crops using chemical (e.g. Hessian fly on wheat) or physical barriers (e.g. hooked hairs), sterile males (e.g. tsetse fly), biotechnology – genetic engineering for transgenic crops (e.g. resistance to pest, or resistance to broad-spectrum herbicide).
Insect Metamorphosis
Larva Pupa AdultEgg
Changes are controlled by juvenile hormones
What are pheromones• Pheromones are chemicals emitted by an
animal that signals another animal of the same species.
• Example: female gypsy moths emit a pheromone to attract a male
Pheromones and Pest Control
• Pheromones can be utilized to catch or deter insects
• Example: Pheromone “traps”, which contain the pheromone emitted by the female gypsy moth can be set to catch male moths
CH2OH (E)10, (Z)12-Hexadecadienol
Sexual pheromone of silk butterfly female (Bombyx mori)
CH2 CH2 OH
(+)(z)2-Isopropenyl-1-methylcyclobutan-ethanol
Sexual pheromone of cotton worm
Examples of some Pheromones
Green Chemistry Technologies and Solutions
Conclusions:Much still to do but Green Chemistry provides a focus for:
• A pro-active approach to the increase in legislation (e.g. emissions, Green House Gases taxes,restricted chemicals list)
• A competitive advantage: beneficial in reducing costs/risks and provide greater manufacturing flexibility
• An improvement in public image