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7/28/2019 Components for Polyamides Products of Propene
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Components for polyamides
Nylon was first produced on an industrial scaleby Du Pont after 1939.
Polyamides are the products of condensationbetween :
diamines and dicarboxylic acids, or betweenaminocarboxylic acids
Polyamides may also be obtained by
polymerizing lactamsThe characteristic of polyamides structure:CONH units alternating with CH2 chains
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Designation of polyamides
The use of one figure represents synthesisfrom a single bifunctional compound, e.g.Nylon 6
Two figures: synthesis from twocomponents, e.g. diamine and dicarboxylicacid
The values of the digits in the figuressignify the number of carbon atoms ineach component, e.g. Nylon 6,6
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Uses of polyamide
In synthetic fibres, e.g. clothes,carpets
In thermoplastics
Aromatic polyamides oraramides are manufactured
from terephthalic acid orisophthalic acid
Aramides are used in flame-resistant fibres, electricalinsulation material and in tire
cords. Kevlar is used in bullet-proof
vests, in the lining ofexpensive cars and shutters ofmore expensive cameras
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Dicarboxylic acids
Adipic acid, suberic acidand sebacic acid are themost widely useddicarboxylic acids in
industry Most adipic acid is
obtained from theoxidative cleavage ofcyclohexane in the liquid
phase and Mn or Co salts(acetate or naphthenate)as catalysts
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The oxidation productsare further oxidized toadipic acid, eitherwith:
nitric acid andammoniummetavanadate/coppernitrate or
Air and copper andmanganese acetate
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Uses of adipic acid
Manufacture of Nylon 6,6
Starting material for
hexamethylenediamine
Component for polyesters
Converted to esters for use in plasticizers
and lubricants Hydrogenated to 1,6-n-hexadiol for use in
polyesters, polyurethanes and HMDA
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1,12-dodecanedioic acid
The starting material,
cyclododeca-1,5,9-
triene, is synthesized
by the trimerization ofbutadiene with a
Ziegler catalyst (TiCl4
and Et2AlCl).
Ni0 and chromiumcomplexes may also
be used as catalysts
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Production of C12 dicarboxylic acid
from cyclododecatriene
1. Hydrogenation tocycloalkane usingNi catalysts
2. Mild oxidation to C12cyclicalcohols andketones
3. Oxidative cleavage
of the ring, resultingin the formation ofthe dicarboxylic acid
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Uses of C12 dicarboxylic acid
In polyamide
In polyesters
Esterified for use as lubricants
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Hexamethylenediamine
Cyclohexanone is
oxidized to caprolactone
Caprolactone is
hydrogenated to 1,6-
hexanediol
1,6-hexanediol is
aminated with ammonia
using a Raney nickel
catalyst to give 1,6-aminohexanol
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Adiponitrile
May be obtained by:
1. Dehydrative
amination of adipic
acid with ammonia(C6 + 2N)
The reaction is
catalysed by
phosphoric acid
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2. The Monsanto
EHD (electro-
hydrodimerization)
method involves thehydrogenative
dimerization of
acrylonitrile to
adiponitrile.The net reaction is:
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The steps involved in
this reductive or
cathodic dimerization
are:
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Hydrogenation of adiponitrile
Adiponitrile can be
hydrogenated using Co-
Cu or Fe catalysts to
produce
hexamethylenediamine.
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-aminoundecanoic acid
Precursor for Nylon 11
Castor oil, the source of ricinoleicacid, is used as the startingmaterial. This is one of the fewexamples of a starting material inindustrial organic chemistry that isnot derived from fossil fuels. Whatis the advantage of this?
Following transesterification ofglycerol triricinolate withmethanol, the methyl ester ispyrotically cleaved at 3000C toyield a C7 aldehyde and the methylester of undecanoic acid. Thepresence of theOH groupslightly weakens the C-C bondthat is indicated by the dotted line,and this bond is broken atelevated temperatures.
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The methyl ester is
saponified, then
converted to 11-
bromoundecanoic acid by
peroxide-catalysed HBraddition
The product is then
reacted with ammonia,
producing -aminoundecanoic acid
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Lactams
-caprolactam, which is the cyclic amide of
-aminocaproic acid, is the most important
lactam in industry
It is used in the manufacture of nylon-6
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The manufacture of-caprolactam
involves 4 steps
1. Production ofcyclohexanone.
Most cyclohexanone
is produced fromcyclohexane. Analternative routebegins with phenol,which may beconverted tocyclohexanone inone or two steps:
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2. Oxime formation
using cyclohexanone
in the presence of a
hydroxylamine salt:
The Toray process
produces oxime by
photonitrosation of
cyclohexane:
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3. Conversion of
cyclohexanone oxime
into -caprolactam by
rearrangement in
sulphuric acid or oleum.The first step forms
lactam sulphate, which
upon neutralization with
ammonia gives the freelactam:
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4. Hydroxylaminesulphate which is usedfor producing the oxime ismanufactured by the
Raschig process, inwhich ammonium nitrite isreduced with sulphurdioxide to produce thedisulphonate, which is
then hydrolysed tohydroxylamine sulphate:
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Propene conversion products
Propylene oxide
Not as reactive asethylene oxide
Attempts at producing itby direct oxidation ofpropylene have not beensuccessful
Propylene oxide ismanufactured by thechlorohydrin process
which was once the mainroute to the synthesis ofethylene oxide:
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Propylene oxide maybe obtained byindirect oxidation orpropene by radicaloxidation usinghydroperoxides orperoxycarboxylicacids. About 40% of
propylene oxide isnow produced by thismethod.
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Peracetic acid may be
produced from acetic
acid and hydrogen
peroxide withsulphuric acid as the
catalyst:
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Secondary products of propylene
oxide
Propylene oxide is used to make 1,2-propyleneglycol, dipropylene glycol and propoxylatedproducts
Propylene glycol is used as an antifreeze and asa brake fluid and in the manufacture of alkydand polyester resins
Polypropylene glycol, obtained by the reaction
between propylene oxide and propylene glycol,are used in manufacturing non-ionic surfactants,detergents and emulsiers
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Acetone
1. Acetone may be obtained by
direct oxidation of propene by
the Wacker-Hoechst process
using PdCl2 as the catalyst.
Compare this with a similarprocess which converts
ethylene to acetaldehyde
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2. Acetone may be obtained
from isopropanol via
oxidative
dehydrogenation over Ag
or Cu catalysts ordehydrogenation over
ZnO catalysts:
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A method by Shell
and Du Pont employs
liquid-phase oxidation
of isopropanol for theproduction of
hydrogen peroxide:
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Methyl isobutyl ketone from
acetone
Methyl isobutyl ketone is the largest
volume aldol condensation product from
acetone
It is used as a solvent for cellulose
acetate, alkyd and acrylic resins; as an
extractant and as the starting material to
produce hexylene glycol
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1st step: formation ondiacetone alcohol ina base-catalysedaldol reaction
2nd step: elimination of
water, catalysed bysulphuric acid orphosphoric acid. Mesityloxide is produced
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3rd step: mesityl oxide
is hydrogenated to
methyl isobutyl
ketone using Ni or Cucatalysts
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Methacrylic acid
Methacrylic acid is used as a homo- or
copolymer and as a thickener or for
finishing
The methyl ester is its the most widely
used derivative
Acetone cyanohydrin is the sole feedstock
for methacrylic acid
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1. Acetone cyanohydrin isproduced by a base-catalysed addition ofhydrocyanic acid to acetone:
2. The cyanohydrin is reactedwith sulphuric acid toproduce methacrylic acidamide sulphate, which isthen converted to methylmethacrylate and
ammonium hydrogensulphate by reaction withmethanol. The product ismethyl methacrylate
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A process designed
by Mitsubishi
hydrolyses the
cyanohydrin to anamide, which is then
reacted with methyl
formate to give the
methyl ester andformamide:
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Uses of methyl methacrylate
For making Plexiglas,a clear plastic havingconsiderablehardness, resistance
to fracturing andchemical stability
As a co-monomer inthe manufacture ofdispersions for paintsand textiles
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Acrolein
Formerly manufactured bycondensing acetaldehyde withformaldehyde in gaseousphase over sodium silicate:
Currently all acrolein isproduced by catalytic oxidationof propene over Cu2O/SiC andI2 as the promoter. Note thatthe double bond actives themethyl group, which is
oxidised. Refer to slide 54 forother examples of methylgroups activated by eithervinylic or aromatic groups
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Uses of acrolein
Hydrogenation to allyl alcohol
Reacted with ammonia in thegaseous phase to formpyridine and -picolinemixtures
As intermediate for themanufacture of acrylic acid andacrylonitrile
For conversion into methionine(an amino acid)
For manufacture of1,3-propanediol, an intermediatefor pharmaceuticalcompounds, also used in apolyester for synthetic fibres
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Acrylic acid and its esters
Ethylene oxide andhydrocyanic acid wereformerly used in theethylene cyanohydrinprocess to formhydroxypropionitrile (inthe presence of a base)
Hydroxypropionitrile isthen reacted with an
alcohol or with water andsulphuric acid to producethe ester or the free acid:
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The Reppe process is
based on the
carbonylation of
acetylene in thepresence of water or
alcohols over a nickel
tetracarbonyl catalyst,
producing the freeacid or the ester:
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Today most acrylicacid is obtained fromdirect oxidation ofpropene with air or
oxygen using amulticomponentcatalyst of mainlymetal molybdates
with telluriumcompounds ascatalysts:
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Uses of acrylic acid and its esters
Monomers for homo- and co-polymers
used for paints and adhesives, in paper
and textiles and leather processing
These polymers are superabsorbants,
having the ability to take up large amounts
of liquids
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Allyl compounds and its secondary
products
These compoundshave the H2C=CH-CH2- functional group
Hot chlorination ofpropene, in which afree radicalsubstitution takesplace at the allyl
position, is used tomanufacture allylchloride:
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Uses of allyl chloride
1. Hydrolysis to allyl
alcohol
H2C=CH-CH2-OH
2. Epoxidation to
3. Ammonolysis to
H2C=CH-CH2-NH2
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Epichlorohydrin production
1. Reaction with
hypochlorous acid
in the aqueous
phase
2. Elimination of HCl
using calcium
hydroxide
Epichlorohydrin is used to produce glycidyl ethers e.g.
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Epichlorohydrin is used to produce glycidyl ethers e.g.
bisphenol A glycidyl ether, precursors for epoxy resins. In
the first step, the epoxide ring breaks to form a chlorohydrin
ether, but it is reformed upon elimination of HCl by NaOH
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Allyl alcohols and esters
1. Allyl alcohol fromallyl chloride:
2. By isomerization ofpropylene oxide
using lithiumphosphate as thecatalyst
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Uses of allyl alcohols
Mainly in the manufacture of glycerol.Glycerol is used as a moistening agent,antifreeze, and as a slip additive.
Glycidol, an intermediate in glycerolsynthesis, is used to synthesizepharmaceutical and cosmetic compounds,and emulsifiers.
Esters of allyl alcohols, such as maleicand phthalic acid, are used in polymers
Gl l d ti f ll l
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Glycerol production from allyl
precursors
The processes of IG
Farben (1943) and
Shell (1948) use allyl
chloride or itsconversion product
epichlorohydrin. The
latter is hydrolysed to
glycerol using 10%caustic soda:
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Allyl alcohol is
hydroxylated using
hydrogen peroxide,
producing glycidol asan intermediate, using
tungsten oxide or
salts of tungstic acid
as the catalyst:
Glycerol is used to produce alkyd resin The
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Glycerol is used to produce alkyd resin. The
reaction between phthalic anyhydride and glycerol
produces a linear, fusible resin
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Acrylonitrile
Acrylic acid nitrile or
acrylonitrile was first
manufactured in 1930 in
Germany, then USA. It
was copolymerized withbutadiene to form a
synthetic rubber, buna
N
The first synthesis (IGFarben) used ethylene
oxide:
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The method of Bayer utilizedthe addition of HCN toacetylene:
Acrylonitrile is now producedmainly by the ammoxidation of
propene. The Sohio process(part of BP) is the mostimportant ammoxidationprocess today. It uses aheterogeneously-catalysedsingle step gas-phase
oxidation of propene in thepresence of ammonia, air andsteam using Bi2O3.MoO3catalysts in a fluidized bed
In ammoxidation activated methyl groups
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In ammoxidation, activated methyl groups
are converted into nitrile groups. Examples
of such groups:
Mechanism of ammoxidation: 2 H atoms are first
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Mechanism of ammoxidation: 2 H atoms are first
abstracted from chemisorbed propene and ammonia, after
which C3H4 and NH react to give acrylonitrile
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Uses of acrylonitrile
As a monomer in the synthesis of syntheticfibres, rubbers and plastics, e.g. ABS(acrylonitrile-butadiene-styrene), SAN (styrene-acrylonitrile)
Electrodimerization of acrylonitrile producesadiponitrile
Modification of starch and cellulose
Manufcture dyes and pharmaceutical
compounds Manufacture of acrylamide, which is used as amonomer to produce polymers used in paints,flocculating agents and resings.