Control of WastesProf. Attilio CitterioDipartimento CMIC “Giulio Natta”http://iscamap.chem.polimi.it/citterio/dottorato//

“The pessimist sees the difficulty in every opportunity. The optimist, the opportunity in every difficulty”

PhDIN INDUSTRIAL CHEMISTRY AND

CHEMICAL ENGINEERING (CII)

Attilio Citterio

Disposal of Effluent

Becoming increasingly costly Need to identify effluent cast for each product

- including aqueous waste

Development work should aim to minimise effluent BEFORE process reaches plant

Need to look at ALL aspects The most efficient processes generate the least

effluent- Catalytic Processes

Attilio Citterio

Disposal Routes

Biological Degradation- Aqueous waste- Aqueous organics- Not suitable for water-immiscibles

Incineration- Suitable for most organic liquid waste- Chlorine and Sulphur compounds may be expensive(They require scrubbing)

Landfill- Acceptable for innocuous solid waste- Widely-used for other wastes- More restrictions likely in the future

Attilio Citterio

Bio-treatment of Organic Molecules

Water solubility is not enough.• Factors which make a molecule more difficult to treat

biologically:- increasing molecular wt (particularly > 500)- water immiscibility- type of bonds: ester > amide > ether/ketone > S-O > P-O- stereochemistry- for aromatics: number and type of substituents

Cl, NO2, SO3H slow degradationOH, C=O, NH2 neutral or increase degrad.

- branching of alkyl chains, particularly quaternary centres, are a problem

- steric hindranceProducts must be non-toxic to organism, e.g. Quaternary ammonium salts, some heterocyclics, some organometallics are biocides

Attilio Citterio

C. Ibbetson, T.C.E., 1996, June, 23

0 100 1000 10000

99% 99.9%Cryogenic

Condensation50% 80% 95%

90% 95% 98%

50% 95% 98%

90% 95-98%

95% 99%

Adsorption

CarbonAdsorption

CatalyticIncineration

ThermalIncineration

Inlet VOC conc. (ppmV)

VOC Reduction Efficiencies - Different Technologies

Attilio Citterio

Solvent TALuft

mg/m3

UK (IPC)guideline

mg/m3

Equilibriumtemperature

TA Luft

TocomplyUK (IPC)

Acetone 150 80 86 -97Methanol 150 80 74 -94Dichloromethane 150 20 99 -118Toluene 100 80 64 -64MIBK 150 20 50 -50THF 100 80 86 -86

VOC Reduction

Attilio Citterio

Disposal Routes

Recycling- Precious metals- Nickel and other metals- Solvents

Neutralisation - Aqueous acids and bases

Disposal routes vary depending on the location of the site

Attilio Citterio

1991 1992 1993 1994 1995 1996

Fuel and power industryCombustion > 50 MW(t)

GasificationCarbonisation

Combustion (rem.)Petroleum

Waste Disposal IndustryIncineration

Chemical recoveryWaste-derived fuel

Mineral IndustryCement

AsbestodFibre

GlassCeramic

The Chemical Engineer, 28 March 1991

Integrated Pollution Control - Timetable

Attilio Citterio

Effluent Control in Process R&D

• Effluent control through process improvement- Synthetic route- Choice of reagent- Stoichiometry- Solvent- Work-up- Total process design

• Pollution Prevention Pays (3P)- 3M saved $420 million through a 3P scheme- 1000,000 tonnes of air pollutants eliminated

Attilio Citterio

3M’s 3P Program

• Product reformulation- Development of non-polluting or less-polluting products- Using different raw materials or feedstocks

• Process modification- Changing processes to control by-product formation- Incorporation of non-polluting or less-polluting raw materials or

feedstocks

• Equipment redesign- To perform better under specific operating conditions- To make use of available resources (such as by-products from

another process)

• Resource recovery- Recycling by-products (for sale or use in other processes)

Attilio Citterio

3M’s 3P Program

None of these concepts is new What is new is the Company commitment Paybacks were attained in less than three years Paybacks were due to

- Decreased raw material costs- Decreased waste management costs- Decreased energy costs- Improved product quality- Enhanced productivity- Decreased downtime- Decreased worker health risk- Decreased environmental hazards- Decreased long-term liability for clean-up, of waste- Improved public image for Company

Attilio Citterio

Corporate Measures

Prof Huisingh has developed a plan of corporate steps necessary for waste reduction- Develop a corporate environmental policy- Develop and use waste-reduction audit procedures- Involve employees in incentive awards programmes- Set corporate goals and timetables for waste reduction- Allocate responsibility, time and finance for waste reduction- Monitor progress on waste reduction programmes- Regularly inform all employees of progress- Update goals and timetables

Attilio Citterio

HN N

SHN NHMe

N

NCN

S

S

H3C

H3C

NCN

S

S

NH2CNBase

CH3NO2Base

NNO2

S

S

Me2SO4 Me2SO4

NNO2

S

S

H3C

H3C

O

SHN NHMe

N

CH2NMe2

NO2CN

CS2

Cimetidine Ranetidine

Synthesis of H2 Antagonist

Attilio Citterio

NCN

S

S

H3C

H3C

MeNH2

+

S N

SHN SMe

N

N

CN

NH2

NH2

S N

SNH2

N NH2

NH2

S N

SHN NHMe

N

N

CN

NH2

NH2

- MeSH

Tiotidine

Synthesis of Tiotidine

Attilio Citterio

NCN

O

O

H3C

H3C

MeNH2

+

S N

SHN OMe

N

N

CN

NH2

NH2

S N

SNH2

N NH2

NH2

S N

SHN NHMe

N

N

CN

NH2

NH2

- MeOH

Alternative Synthesis of Tiotidine

Attilio Citterio

Tiotidine - Problems with N-Cyanodithioimidocarbonate Route

• MeSH has a very low our thresold (1 ppb)

• TLV is 0.5 ppm

• 1 kg Tiotidine generates 0.5 kg of MeSH

• Emissions encountered during scale-up work (20 L)

• Therefore need to examine alternatives

Attilio Citterio

Tiotidine - Use of N-Cyanoimidocarbonates

• Replacement of the first alkoxy group is fast• Replacement of the second alkoxy group is

usually slow• Product is not very stable - rearranges

NCN

O

O

R

R

RO N

OCN

R

Attilio Citterio

N-Chloro intermediates explosiveGeneration of alkyl hypochlorite

NCN

O

O

R

RKCN + Cl2

ROH

NHO

O

R

RClCN + NaOR

CyanamideHCl

NO

O

R

R CN

Process requires simultaneousaddition of reagentsProcess difficult to scalePremixing of reagents investigated

Synthesis of N-Cyanoimidocarbonates

Attilio Citterio

Temperature Half-life

0 > 100 hours12 43 hours25 8.3 hours37 2.2 hours

Therefore, premixing not a problem

Simple process gives 55% yield on plant

Cyanamide - Half live in 36% HCl

Attilio Citterio

Is This Process Useful for Other Anti-Ulcer Drugs?

Cimetidine?Ranetidine?

ICI has in-house source of ClCN

Carbon disulphide is cheap

Require other sources of CX2Y2 or Cl2=NCN

Attilio Citterio

AcidWater

WaterSolventReactants

Filter

Filter

Final product(cake)

Wasteliquors

Reslurry

Product(cake)

Quench

Wasteliquors

Reaction

Case Study - Polaroid Dye Synthesis

Attilio Citterio

Case Study - Polaroid Dye Synthesis

• Two high-volume aqueous steam produced

• First steam heavily contaminated- Organic solvents, reaction by-products, heavy metal salts- Requires licensed external disposal

• Second stream less contaminated- But still requires external disposal

• Solution: Use second stream as quench for next batches- No equipment change- Costs only R&D and product testing- Waste volume reduced (60,000 gal in 1987/ 80,000 gal in 1988)

• Annual saving on transport and disposal of waste -$ 160.000 in 1988

Attilio Citterio

Rhone-Poulenc

Mitsubishi

H2O, heati)

Cl2

ii) H2O

OH O

OH

OH

OH

Cheap raw materialsSample processEffluent - 50 Kg/kg Product

H2 / Pt

O2CuCl LiCl

OH O

OH

OH

O

More expensive rawmaterialsComplex processEffluent - 2 Kg/kg Product

C. Mercier (R-P), Pure App. Chem., 1994, 1516

Vitamin E Intermediate

Attilio Citterio

- 35°C+ Li/NH3

HC CHO

R COH

HCCH

CH2

+ Li salt

- Lithium dissolved in ammonia at -35°C- Acetylene added to give dilithium acetylide- More acetylene added to give monolithium acetylide- Ketone added in solvent - reaction to give lithium enolate- Ammonia removed- Product released with diluted sulphuric acid- Layers separated- Solution of etinal stripped to remove polymeric material- Solution used in next step

H. Wiederkahr, Chem. Eng. Science, 1988, 1783

Etinol - Vitamin Intermediate

Attilio Citterio

Problems and Solutions Tried

Problems• Consumption of lithium - 50% of cost of intermediate

- 6.5 million dollars worth of lithium goes to the effluent plant in one year

• Acetylene and ethylene emission• Ammonia losses

Solution tried• Recycling lithium - unsuccessful• Replacement of lithium by cheaper alkali metals - much lower

yield • Catalytic process - low yield

Attilio Citterio

Laboratory Improvement

• Prepare lithium acetylide as before in ammonia

• Evaporate ammonia and replace with solvent

• Carry out reaction in solvent as before

• Gives 95% yield

• Can reduce lithium excess from 20% to 5%

Attilio Citterio

Etinol - Scale-Up Problems

• Unable to reproduce yield• Ammonia evaporation takes longer; temperature plateaux in reactor

before all ammonia removed• Found that complex formed between lithium acetylide and ammonia• 1:1 ratio of acetylide and ammonia absolutely critical

- below 1:1 - disproportionation to dilithium acetylide; reaction with ketone gives resins

- above 1:1 - polymerisation- at 1:1 - high yields achieved

• Need good process control• Result

- Process scaled up well- Other modifications to reduce effluent examined

Attilio Citterio

Etinol - Effluent Control

• Modified work-up to enable reprocessing of lithium by manufacture- Hydrolyse product with water, not acid- Separate phases- Neutralise organic phase with acid, then strip as before- Concentrate aqueous phase - recycle LiOH solution

• In separate studies, recycling of acetylene (by dissolving in ammonia) and ammonia implemented

• Total cost of implementing all 3 modifications - $ 4.6 million

Attilio Citterio

YIELD before after differencebased on ketone 82.0% 95.0% 13.0%based on lithium 68.0% 90.0% 22.0%RAW MATERIALSKetone 100 85.4 14.6Lithium 100 14.2 85.8Acetylene 100 48.2 51.6Ammonia 100 24.1 75.9Sulphuric acid 100 0.0 100.0Solvent 100 96.5 3.5Total 100 45.2 54.8

Etinol - Yield & RM Consumption

Attilio Citterio

WASTEPRODUCT before after differencePolymers 100 17.6 82.4Lithium salt 100 1.7 98.3Acetylene 100 (28.0) 100.0Ammonia 100 24.1 75.9Solvents 100 (96.5) 100.0Miscellaneous 100 8.3 91.7Total 100 5.3 94.7

Etinol - Waste Products

Attilio Citterio

N

+

NH2

OMe

NaNO2

MeOH - H2O, CO2

N N N

OMe

5 - 65 barCO2 + H2O H2CO3

(pKa = 3.3 ~ pKa )H2CO3 HNO2

Current azo dye production generates as by-products large amounts of salts.

Heterocyclic amines, normally difficult to diazotise, work well in CO2

Bayer - Salt-free Diazotisation

Attilio Citterio

Water

Phos

gene

Phosphorustrichloride

Triphenylphosphineto purification

Phosphorus

To watertreatment

Triphenylphosphineoxide impurities

Solv

ent

Ph3P=O + COCl2 Ph3PCl2

3 Ph3PCl2 + 2 P 3 Ph3P + 2 PCl3

Recovery of Triphenylphosphine