Acetylene
Acetylene is odorless in its
purest form, but industrial acetylene has a distinct smell that is similar to
garlic. It is also quite soluble in alcohol and virtually miscible with ethane.
The combustible gas acetylene is stored under pressure in gas cylinders.
Acetylene can combine with copper, silver, and mercury to generate acetylides,
which are substances that can serve as ignition sources.
Acetylene can be used with brasses
and some nickel alloys that include less than 65% copper in the alloy. Strong
oxidizers like bromine pentafluoride, oxygen, oxygen difluoride, and nitrogen
trifluoride, as well as brass metal, calcium hypochlorite, heavy metals like
copper, silver, and mercury, as well as their salts, as well as bromine,
chlorine, iodine, fluorine, sodium hydride, calcium hydride, ozone, perchloric
acid, and potassium, are incompatible with acetylene.
Identification
Name |
Acetylene |
CAS |
74-86-2 |
Synonyms |
·
4-(chloromethyl)tolunitrile ·
CARBON BLACK ·
Ethine ·
Ethyne ·
Narcylen ·
Acetylen ·
C2H2 ·
Vinylene ·
ethenylene ·
Welding Gas ·
ACETYLENE (DISSOLVED) ·
Acetylene (non-chemical
use) ·
Acetylene (chemical use) ·
acetylene ethyne ·
Drew Ameroid Amerox
Acetylene 40 LTR ·
Dissolved acetylene ·
Acetylene (liquefied) |
EINECS |
200-816-9 |
Molecular Formula |
C2H2 |
MDL Number |
MFCD00008567 |
Molecular Weight |
26.04 g/mol |
MOL File |
74-86-2.mol |
Melting point |
-88°C |
Boiling point |
-28°C |
Density |
0.91 |
vapor pressure |
3.04 X 104 mmHg (~40 atmospheres) at 16.8 °C |
refractive index |
1.00051 |
Fp |
-18°C |
pka |
25at 25 ℃ |
Odor |
Odorless, although garlic-like or ''gassy" odor
often detectable because of trace impurities |
Water Solubility |
0.106 g/100 mL |
Appearance
Acetylene is a compressed,
colorless gas that is very combustible. When it is pure, it smells faintly
ethereal; when it is tainted, it smells like garlic.
Chemical Properties
Acetylene is odorless in 100%
purity, but it smells strongly like garlic in industrial purity. It is
virtually miscible with ethane and extremely soluble in alcohol. The
combustible gas acetylene is stored under pressure in gas cylinders. Acetylene
can combine with copper, silver, and mercury to generate acetylides, which are
substances that can serve as ignition sources. Acetylides, substances that can
serve as ignition sources, are a component of brasses. Acetylene can be used
with brasses and some nickel alloys that include less than 65% copper in the
alloy.
Strong oxidizers like chlorine,
bromine pentafluoride, oxygen, oxygen dichloride, and nitrogen trifluoride, brass
metal, calcium hypochlorite, heavy metals like copper, silver, and mercury, and
their salts, bromine, chlorine, iodine, fluorine, sodium hydride, cesium
hydride, ozone, perchloric acid, or potassium are incompatible with acetylene.
General Description
an odorless gas with a hint of
garlic. flammable with ease and emitting a sooty flame. Air is heavier than
gas. Flame can very simply return to the leak's origin. The canisters may
violently burst and shoot into the air when exposed to heat or fire for an
extended period of time.
Reactivity Profile
1. Alkali metals and ACETYLENE (74-86-2) react to produce
hydrogen gas.
2. Bromine and ACETYLENE(74-86-2) might react violently.
3. When ACETYLENE(74-86-2) is added to an aqueous
solution of mercuric nitrate, it transforms into a sensitive acetylide.
4. An explosion was caused when a plow frame loaded with
hydrogen gas was drilled through with an ACETYLENE(74-86-2) torch.
5. Silver, copper, and lead react with acetylene
(74-86-2) to generate delicate, explosive salts.
6. The interaction between ACETYLENE(74-86-2), an endothermic
substance that functions as a reducing agent, and oxidants can be quite intense
(examples: calcium hypochlorite, nitric acid, nitrogen oxide, ozone,
trifluoromethyl hypofluorite, etc.).
7. Due to the significant temperature differences
present, contact of very cold liquid gas with water may cause intense or
violent boiling of the product and highly quick vaporization. The risk of a
liquid "superheat" explosion exists if the water is warm. If liquid
gas comes into contact with water in a confined container, pressures may
increase to dangerous levels.
8. When in contact with silver, the explosive silver
salts ACETYLENE(74-86-2) and ammonia can produce.
Air & Water Reactions
Extremely flammable a little water
soluble. creates poisonous ammonia gases when combined with water.
Health Hazard
There could be headaches, vertigo,
and even unconsciousness. If the oxygen content of the air is significantly
lowered by dilution with acetylene, death by "smothering" may result.
Acetylene exposure for extended
periods of time can result in a variety of symptoms, including nausea,
vomiting, dizziness, respiratory difficulties, ringing in the ears, shortness
of breath, wheezing, dizziness, and unconsciousness. Overexposure victims' skin
may appear blue in tone. Chronic exposure to the elements of this compressed
gas has not been linked to any known harmful health effects. Death or major
harm may result from insufficient oxygen. The kidneys, CNS, liver, respiratory
system, and eyes are among the target organs.
Potential Exposure
Acetylene is used in metallurgy
for brazing, welding, cutting, metallizing, hardening, flame scarfing, and
local heating. It can be burnt in oxygen or air. The glass sector also makes
use of the flame. Chemically, acetylene is used to produce trichloroethylene,
acrylate, butyrolactone, 1,4-butanediol, vinyl alkyl ethers, pyrrolidone,
synthetic rubber, vinyl chloride, acrylinitrile, and other compounds.
Fire Hazard
Behavior in Fire: May explode in
fire
First aid
Get the victim outside. Dial a
medical emergency line. If the victim is not breathing, perform artificial
respiration. Give oxygen if breathing is difficult. Take off and keep
contaminated clothing and shoes isolated. If you come into touch with liquefied
gas, use warm water to thaw any areas that have frozen. Keep the victim cozy
and silent. Make that the medical staff is informed about the substance(s) in
question and takes the necessary safety measures.
As well as the document listed below,
see the NIOSH criteria. Do not touch or wash the affected regions of frostbite;
instead, seek medical assistance right away. DO NOT try to remove frozen
garments from regions that have been exposed to the cold in order to avoid
further tissue damage. If frostbite has not yet happened, wash the infected
skin with soap and water right away.
Shipping
Acetylene that has been dissolved,
Hazard Class 2.1, Labeled as 2.1-Flammable gas, UN1001. Cylinders must be
transported in a truck with good ventilation, securely upright. Spare the
cylinder and the labels from harm. Federal legislation (49CFR) only permits the
owner of the compressed gas cylinder to transfer and refill it. Refilling
compressed gas cylinders without the owner's express written consent is against
transportation regulations.
Incompatibilities
Heating the substance may cause it
to polymerize. When heated and under pressure, the chemical decomposes, posing
a risk of fire and explosion. The material is a potent reducer and under the
influence of light interacts violently with oxidants, fluorine, and chlorine,
creating a fire and explosion hazard. combines with copper, silver, and mercury
in order to generate compounds that are sensitive to shock (acetylides).
Acetylene transport lines cannot
include more than 63% copper. may combine explosively with air. creates a
mixture that is shock-sensitive when copper, mercury, and their salts, as well
as silver and their salts, are combined. reacts with sodium hydride,
trifluoromethyl hypofluorite, brass, bromine, cesium hydride, chlorine, cobalt,
and cuprous acetylize; fluorine, iodine, and mercuric nitrate; nitric acid,
potassium, and rubidium hydride.
Waste Disposal
Send refilled compressed gas
cylinders back to the source. Consult environmental regulatory organizations
for advice on proper disposal procedures. Generators of this
contaminant-containing trash (100 kg/mo) are required to abide by EPA standards
controlling waste disposal, treatment, storage, and transportation.
Incineration.
Physical properties
The simplest alkyne hydrocarbon,
acetylene, occurs as a gas that is colorless, combustible, and unstable and has
a distinct, pleasant odor (acetylene prepared from calcium carbide has a garlic
smell resulting from traces of phosphine produced in this process). In the
petroleum business, compounds with a triple bond of carbon are collectively
referred to as "acetylenes."
History
Edmund Davy (1785–1857) discovered
acetylene in 1836 while attempting to create potassium metal from potassium
carbide (K2C2). By creating an electric arc between carbon electrodes and
hydrogen in 1859, Marcel Morren in France created acetylene. Morren described
the gas as hydrogen that had been carbonized. Morren's experiment was
replicated three years later by Pierre Eugène-Marcelin Berthelot (1827-1907),
who recognized carbonized hydrogen as acetylene.
Uses
The synthesis of other chemicals
uses about 80% of the acetylene produced as a closed-system manufacturing
intermediate. Vinyl chloride monomer, N-vinylcarbazole, 1,4-butanediol, vinyl
ethers, N-vinyl-2-pyrrolidone, vinyl fluoride, N-vinylcaprolactam, and vinyl
esters are among the additional compounds produced from acetylene. About 20% of
acetylene is also used in oxyacetylene torches, which are used for welding and
cutting metal.
As a fuel, illuminant, purifier of
copper, silver, and other metals, and in the production of acetic acid,
acetaldehyde, and acetylides, acetylene is used to weld and cut metals. When
calcium carbide and water react, it is created. It can also be made by cracking
fractions of petroleum naphtha.
pptg metals, particularly Cu;
production of acetaldehyde and acetic acid; illumination; oxyacetylene welding,
cutting, and soldering metals; fuel for motor boats.
Definition
an alkyne gas. Since ethyne burns
with oxygen to produce an extremely hot flame, it has historically been used in
oxy-acetylene welding torches. Additionally, it is critical to the synthesis of
various vinyl compounds as well as chloroethene (vinyl chloride), the precursor
to polyvinyl chloride (PVC), in the organic chemicals sector. Ethyne was
previously produced by the expensive process of synthesizing calcium dicarbide
and then hydrolyzing it. Alkanes are progressively cracked using modern
techniques.
Production Methods
The traditional method of
producing acetylene is from reacting lime, calcium oxide (CaO), with coke to
produce calcium carbide (CaC2). The calcium carbide is then combined with water
to produce acetylene:
2CaO(s) + 5C(s)→2CaC2(g) + CO2(g)
CaC2(s) + 2H2O(l)→ C2H2(g) + Ca(OH)2(aq)
In the 1920s, a number of methods
for generating acetylene from natural gas and other petroleum products were
discovered. To prevent all of the methane from combusting, thermal cracking of
methane entails heating methane to about 600°C in an oxygen-poor atmosphere.
When some of the methane mixture is burned, the temperature rises to about
1,500°C, which causes the remaining methane to crack as shown by the following
reaction:
2CH4(g) → C2H2(g) + 3H2(g).
In addition to methane, ethane,
propane, ethylene, and other hydrocarbons can be used as feed gases to produce
acetylene.
Acetylene is manufactured for use
in industry by pyrolyzing naphtha during a two-stage cracking process. End
products include acetylene and ethylene. The naphtha feed rate can be altered
to alter the ratio of the two products. Additionally, crude oil has been used
in a submerged-flame technique to create acetylene. In essence, the flame used
to gasify the crude oil is sustained by oxygen found beneath the oil's surface.
The borders of the flame are where the oil burns and cracks.
The broken gas contains 6.3%
acetylene and 6.7% ethylene, roughly speaking. Therefore, additional separation
and purification are necessary. J. W. Reppe devised a set of reactions that
eventually came to be known as "Reppe chemistry" several years ago
when protocols were created for the safe handling of acetylene on a wide scale.
The production of numerous high polymers and other synthetic items benefited
greatly from these reactions. Reppe and his colleagues were successful in
synthesizing compounds that had previously been off-limits to commerce.
An illustration is the production
of cyclooctatetraene by heating an acetylene solution under pressure in
tetrahydrofuran in the presence of a catalyst made of nickel cyanide. In a
different process, a nickel catalyst was used to create acrylic acid from CO
and H2O:
C2H2 + CO + H2O → CH2:CH·COOH.
These two reactions are
representative of a much larger number of reactions, both those that are
straight-chain only, and those involving ring closure.
Reactions
Acetylene reacts:
(1) with chlorine, to form
acetylene tetrachloride C2H2Cl4 or CHCl2·CHCl2 or acetylene dichloride C2H2Cl2
or CHCl:CHCl.
(2) with bromine, to form
acetylene tetrabromide C2H2Br4 or CHBr2·CHBr2 or acetylene dibromide C2H2Br2 or
CHBr:CHBr.
(3) with hydrogen chloride
(bromide, iodide), to form ethylene monochloride CH2:CHCl (monobromide,
monoiodide), and 1,1-dichloroethane, ethylidene chloride CH3·CHCl2 (dibromide,
diiodide).
(4) with H2O in the presence of a
catalyzer, e.g., mercuric sulfate HgO4S, to form acetaldehyde CH3·CHO.
(5) with hydrogen, in the presence
of a catalyzer, e.g., finely divided nickel heated, to form ethylene C2H4 or
ethane C2H6.
(6) with metals, such as copper or
nickel, when moist, also lead or zinc, when moist and unpurified. Tin is not
attacked. Sodium yields, upon heating, the compounds C2HNa and C2Na2.
(7) With ammoniocuprous (or
silver) salt solution, to form cuprous (or silver) acetylide C2Cu2, dark red
precipitate, explosive when dry, and yielding acetylene upon treatment with
acid.
(8) with mercuric chloride
solution, to form trichloromercuric acetaldehyde C(HgCl)3·CHO, precipitate,
which yields with HCl acetaldehyde plus mercuric chloride.
Hazard
Asphyxiation cannot happen until the
LEL of acetylene is achieved, and the danger of explosion occurs before any
other health hazard is evident. The fire should be put out before shutting the
valve to the container when battling fires involving acetylene containers. It
can fire inside the container since acetylene has such a broad range of
flammability. Copper, silver, mercury, fluorine, chlorine, and their
derivatives are all incompatible with acetylene.
The four-digit UN identification
number for acetylene is 1001. Health 1, flammability 4, and reactivity 3 are
the NFPA 704 designations. When the acetylene is dissolved in acetone, the
reactivity is decreased to 2.
Flammability and Explosibility
Acetylene is a highly flammable
gas that can combine explosively with air at concentrations ranging from 2 to
80%. Acetylene can exothermally polymerize, which can cause a deflagration.
Acetylene has an extremely high positive free energy of production, making it
thermodynamically unstable and susceptible to pressure and shock.
Small concentrations of other
substances, such as methane, help to increase its stability, and because
acetylene is dissolved in acetone, handling it in cylinders is generally
considered to be safe. Extinguishers that use carbon dioxide, dry chemicals, or
halon can put out acetylene fires; but, turning off the gas supply makes the
process much easier.
Industrial uses
Acetylene is a gas that is
colorless, combustible, and smells like garlic. It is highly explosive when
compressed, but if the high-pressure cylinders are lined with absorbent
material that has been soaked in acetone, it can be compressed and stored
safely. The red line on acetylene pressure gauges indicates that users should
not discharge acetylene at pressures higher than 15 psig (103 kPa).
The oxyacetylene flame can be used
for a wide variety of welding and cutting operations, such as hardfacing,
brazing, beveling, gouging, and scarfing, thanks to its extreme heat and
controllability. Metals can be bent, straightened, formed, hardened, softened,
and strengthened using acetylene's heating capabilities.
Purification Methods
Acetylene should be purified if it
is extremely impure by passing it repeatedly through spiral wash bottles
containing, in this order: saturated aqueous NaHSO4, H2O, 0.2M iodine in
aqueous KI, sodium thiosulfate solution, alkaline sodium hydrosulfite with
sodium anthraquinone-2-sulfonate as indicator, and 10% aqueous KOH solution
(two bottles).
The gas is then routed through two
drying tubes, the second of which contains Dehydrite [Mg(ClO4)2], and a Dry-Ice
trap. J Am Chem Soc 61 1868 1939, Conn et al. By passing through H2O, then conc
H2SO4, or by passing through two gas traps at -65o and -80o, conc H2SO4, a soda
lime tower, a tower of 1-mesh Al2O3, and then through H2SO4, acetone vapour can
be extracted from acetylene.
Sometimes it contains acetone and
air. These can be removed by a series of bulb-to-bulb distillations, e.g. a
train consisting of a conc H2SO4 trap and a cold EtOH trap (-73o), or passage
through H2O and H2SO4, then over KOH and CaCl2. It is also available
commercially as 10ppm in helium, and several concentrations in N2 for
instrument calibration.
Storage
Acetylene should only be used in
well-ventilated areas and should be stored in a cool, dry location in a well
sealed container. Cylinders should be kept at least 20 feet away from oxygen
and other oxidizers, or behind a barrier made of non-combustible material that
is at least 5 feet tall and has a 30 minute fire resistance rating. Storage in
excess of 2500 cu ft is forbidden in buildings with other occupancies.
To prevent falling or being
knocked over, cylinders should be stored upright with a valve protection cap in
place and firmly fastened. It is important to preserve the cylinders from
physical harm and to avoid dragging, rolling, sliding, or dropping them. For cylinder
movement during shipment, employees should use an appropriate hand truck. In
the storage or use areas, special attention should be paid to labeling "No
Smoking" or "Open Flames" signage. There shouldn't be any
ignition sources. In the storage and use areas, all electrical equipment should
be explosion-proof.
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