Acetylene Derivatives
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Chapter 5: Acetylene Derivatives Vinyl Chloride Reaction of acetylene with hydrogen chloride HC CH + HCl CH 2 CHCl Ethyne Vinyl Cloride - advantage : No by-product hydrogen chloride was formed - carried out in vap. phase using charcoal impregnated with 10% mercuric chloride as catalyst - reagents pure and dry with slight Xs of hydrogen chloride - press. atmospheric or slightly higher - temp : 100 to 210 o C - exothermic reaction - rxn. conditions depends on age and cond. of catalyst - nearly all vinyl chloride polymerized to PVC and small amount converted to vinylidene chloride. The emergence of ethylene (ethene) as contender for vinyl chloride production arose from development of oxychlorination processes. The decomposition of EDC to vinyl chloride splits HCl which is most undesirable and wasteful by-prodt Hence, ‘balanced’ process was introduced whereby HCl fr. decomposition of EDC was reacted with acetylene to make more Vinyl Chloride
description
acetylene
Transcript of Acetylene Derivatives
Chapter 5: Acetylene Derivatives
Vinyl Chloride Reaction of acetylene with hydrogen chloride
HC CH + HCl CH2CHClEthyne Vinyl Cloride
- advantage : No by-product hydrogen chloride was formed- carried out in vap. phase using charcoal impregnated with 10%
mercuric chloride as catalyst- reagents pure and dry with slight Xs of hydrogen chloride- press. atmospheric or slightly higher- temp : 100 to 210oC - exothermic reaction- rxn. conditions depends on age and cond. of catalyst- nearly all vinyl chloride polymerized to PVC and small amount
converted to vinylidene chloride.
The emergence of ethylene (ethene) as contender for vinyl chloride production arose from development of oxychlorination processes.
The decomposition of EDC to vinyl chloride splits HCl which is most undesirable and wasteful by-prodt
Hence, ‘balanced’ process was introduced whereby HCl fr. decomposition of EDC was reacted with acetylene to make more Vinyl Chloride
Vinyl Acetate The reaction between acetylene and acetic acid.
CH3COOH + HC CH CH3COOCH CH2
Vinyl Acetate
- carried out in vap. Phase using catalyst comprising zinc or cadmium acetate on charcoal
- temp. about 210oC- pressure slightly above atmospheric- Xs acetic acid to red. Formation of ethylidene diacetate by-
product- Exit gases cooled to 0oC- Purified by distillation
- Polymerised rapidly either alone or with other vinyle compounds
- Applications : adhesives and emulsion paints- Presently, ethylene has been used to replace acetylene as the
raw material. (Covered in Chap. 8)
Chloroprene Monomer for polychloroprene rubbers Characteristics of these rubbers:
- good resistance to weathering (ie. ozone resistance)- sustain continuous flexing without undue build up of heat- adhesives- less heat resistance than other rubbers hence limitations
1st stage chloroprene production:2HC CH HC CCH CH2
monovinylacetylene
- liquid phase dimerization of acetylene - presence of aqueous solution of CuCl and NH4Cl- temp. 65 – 75oC- above atmospheric pressure- contact time 10 – 15 sec- 20% conversion- 60 – 65% yield
2nd stage:HC CCH CH2 + HCl CH2 CClCH CH2 Monovinylacetylene Chloroprene
- presence of aqueous CuCl - temp. 30 – 60oC- > 90% yield
Polychloroprene – produced by emulsion polymerisation process using radical-initiated with mercaptans
Process change: using butadiene as raw materials- butadiene chlorinated in gaseous phase to form 1,2-
dichlorobut-3-ene and 1,4-dichlorobut-2-ene- interconvertible in presence of copper catalysts
- 1,2-dichlorobut-3-ene dehydrochlorinated by contact with aqueous sodium hydroxide to produce chloroprene (2-chlorobuta-1,3-diene) for polymer production
- acetylene dimmer route phase out ! Trichloroethylene
- HClHC CH + 2Cl2 CHCl2 CCl2
CHCl2 CHCl tetrachloroethane trichloroethylene
- chlorination of acetylene in CHCL2CHCl2 solution - temp. 80oC- reduced pressure- catalyst : antimony or ferric chloride - acetylene and Cl2 introd. independently into liq.
tetrachloroethane- exo. reaction, hence cooling of prodts. necessary- gas phase operation poss. but not practice - chlorinated prodt, tetrachloroethane is dehydrochlorinated to
give trichloroethylene- HCl removal using slurry of lime and loss of chlorine as
calcium chloride
Setbacks ! Trichloroethylene results in environmental problems producing air pollution and also carcinogen
Perchloroethylene
CCl2 CCl3 CCl2
CHCl CHCl2 CCl2
trichloroethylene pentachloroethane perchloroethylene
Two stage process:- Trichloroethylene chlorinated in pentachloroethane solution - Temp. 80 – 90oC- Catalyst: metal chloride- Dehydrochlorinated (removal of HCl) to form
perchloroethylene using alkali or pyrolysis Applications: chemical intermediates
Acrylonitrile
HC CH + HCN CH2
CHCNacrylonitrile
- Addition of acetylene to hydrogen cyanide- Atmospheric pressure- Temp. 70 – 90oC- Solution of CuCl in hydrochloric acid
Process change: based on propylene ammoxidation (Covered in Chap. 9)
Applications: synthetic fibres in textile industry, plastics, adiponitrile for nylon
Acetaldehyde
HCCH + HOH H2C=CHOH CH3CHOvinyl alcohol acetaldehyde
- Acetylene hydration process using H2SO4
- Reduction-oxidation system of mercurous/mercuric sulphate catalyst buffered by ferric sulphate
- Initial prodt. – vinyl alcohol which rearranges itself to give acetaldehyde
- Atmospheric pressure- Temp. 95oC- 53% acetylene conversion and balance recycled Applications: acetic acid and acetic anhydride production
Acrylic acid and acrylates
C2H2 + CO + H2O CH2=CHCOOH
- High pressure reaction- Nickel and halogen (NiBr) catalyst- Temp. 225oC- Pressure 100 atm.- Medium: tetrahydrofuran solution Other routes: propylene oxidation (Covered in Chap. 9)
Isoprene Italian process based on reaction of acetylene and acetone
- Press. 20 atm- Temp. 10 – 40oC- Liquid ammonia as solvent- Alkaline catalyst
2nd step : hydrogenation process of methyl butynol to methyl butenol
3rd step : dehydration using alumina at 260 – 300oC
C2H2 + (CH3)2CO CH3C(CH3)(OH)C≡CHacetylene acetone methyl butynol
+ H2 - H2O
CH2=C(CH3)CH=CH2 CH3C(CH3)(OH)CH=CH2
isoprene methyl butenol
