project on deepak
TRANSCRIPT
SHIVAJIRAO S. JONDHALE COLLEGE
OF ENGINEERING
MANUFACTURING
OF
ACETALDEHYDE
PROJECT GUIDE:
PRADNYA KAMBLE
GROUP MEMBERS:
SUDARSHAN S.
DEEPAK YADAV
PRAMOD SHARMA
1
ACKNOWLEDGEMENT
I am deeply indebted to my guide Prof.Pradnya Kamble, whose support,
stimulating suggestions and encouragement helped me throughtout the course of
my work and writing of this report. Without her expert advices and motivations, I
would not have achieved my current level of completeness.
My cordial thanks to all other professors for their teaching and helping throughout
all these semesters.
Also I whole heartedly thank to all my friends for their help and activities.
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CERTIFICATE
MANUFACTURING OF ACETALDEHYDE
PROJECT SUBMITTED
TO THE
UNIVERSITY OF MUMBAI
FOR THE DEGREE OF
B.E. IN CHEMICAL ENGINEERING
PROJECT TEAM:
SUDARSHAN S.
DEEPAK YADAV
PRAMOD SHARMA
SHIVAJIRAO S. JONDHALE C.O.E.DOMBIVLI
DEC-2010
__________________ _________________
PROJECT GUIDE: PRINCIPAL
PRADNYA KAMBLE
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INDEX
PAGE NO.
CHAPTER 1
1.1 Intoduction
1.2 Material Safety Data Sheet
5
7
CHAPTER 2
2. Properties And Uses
18
CHAPTER 3
3. Process Selection And Justification
28
CHAPTER 4
4. Process Description
36
5. Bibliography
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CHAPTER 1:
INTRODUCTION:
5
CHAPTER 1
INTRODUCTION
Acetaldehyde, CH3CHO is an important intermediate in industrial organic synthesis.
Acetic acid, acetic anhydride, n-butanol, and 2-ethylhexanol are the major products derived from
acetaldehyde. Smaller amounts of acetaldehyde are also consumed in the manufacture of
pentaerythritol, trimethylolpropane, pyridines, peracetic acid, crotonaldehyde, chloral, 1,3-
butylene glycol, and lactic acid. Acetaldehyde (ethanal) was first prepared by Scheele in 1774,
by the action of manganese dioxide and sulfuric acid on ethanol. Liebig established the structure
of acetaldehyde in 1835 when he prepared a pure sample by oxidizing ethyl alcohol with
chromic acid. Liebig named the compound “aldehyde” from the Latin words translated as al
(cohol) dehyd (rogenated). Kutscherow observed the formation of acetaldehyde by the addition
of water to acetylene in 1881.
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Acetaldehyde is an important intermediate in the production of acetic acid, acetic
anhydride, ethyl acetate, peracetic acid, pentaerythritol, chloral, glyoxal, alkylamines, and
pyridines. Acetaldehyde was first used extensively during World War I as an intermediate for
making acetone from acetic acid. Commercial processes for the production of acetaldehyde
include: the oxidation or dehydrogenation of ethanol, the addition of water to acetylene, partial
oxidation of hydrocarbons, and the direct oxidation of ethylene. It is estimated that in 1976, 29
companies with more than 82% of the world’s 2.3 megaton per year plant capacity use the
Wacker – Hoechst processes for the direct oxidation of ethylene. Acetaldehyde is a normal
intermediate product in the respiration of higher plants. It occurs in traces in all ripe fruits that
have a tart taste before ripening; the aldehyde content of the volatiles has been suggested as a
chemical index of ripening during cold storage of apples. Acetaldehyde is an intermediate
product of alcoholic fermentation but it is reduced almost immediately to ethanol. It may form in
wine and other alcoholic beverages after exposure to air, and imparts an unpleasant taste; the
aldehyde ordinarily reacts to form diethyl acetal and ethyl acetate. Acetaldehyde is an
intermediate product in the decomposition of sugars in the body and, hence, occurs in traces in
blood. Acetaldehyde is a product of most hydrocarbon oxidations.
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Material Safety Data Sheet
Acetaldehyde MSDS
Chemical Name: Acetaldehyde Chemical Formula: CH3CHO
1.1 Composition and Information on Ingredients
Composition:
Name CAS # % by Weight
Acetaldehyde 75-07-0 100
Toxicological Data on Ingredients:
Acetaldehyde: ORAL (LD50): Acute: 661 mg/kg [Rat.]. 900 mg/kg [Mouse]. DERMAL
(LD50): Acute: 3540 mg/kg [Rabbit]. VAPOR (LC50): Acute: 13300 ppm 4 hours [Rat]. 23000
mg/m 4 hours [Mouse].
1.2 Hazards Identification
1.2.1 Potential Acute Health Effects:
Hazardous in case of eye contact (irritant), of ingestion, of inhalation (lung irritant). Slightly
hazardous in case of skin contact (irritant, permeator).
1.2.2 Potential Chronic Health Effects:
Hazardous in case of skin contact (irritant). Slightly hazardous in case of skin contact
(sensitizer). CARCINOGENIC EFFECTS: Classified 2B (Possible for human.) by IARC.
MUTAGENIC EFFECTS: Mutagenic for mammalian somatic cells. Mutagenic for bacteria
and/or yeast. TERATOGENIC EFFECTS: Classified POSSIBLE for human.
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DEVELOPMENTAL TOXICITY: Not available. The substance may be toxic to liver. Repeated
or prolonged exposure to the substance can produce target organs damage.
1.3 First Aid Measures
1.3.1 Eye Contact:
Check for and remove any contact lenses. Immediately flush eyes with running water for at least
15 minutes, keeping eyelids open. Cold water may be used. Get medical attention.
1.3.2 Skin Contact:
In case of contact, immediately flush skin with plenty of water. Cover the irritated skin with an
emollient. Remove contaminated clothing and shoes. Cold water may be used.Wash clothing
before reuse. Thoroughly clean shoes before reuse. Get medical attention.
1.3.3 Serious Skin Contact: Not available.
1.3.4 Inhalation:
If inhaled, remove to fresh air. If not breathing, give artificial respiration. If breathing is difficult,
give oxygen. Get medical attention.
1.3.5 Serious Inhalation:
Evacuate the victim to a safe area as soon as possible. Loosen tight clothing such as a collar, tie,
belt or waistband. If breathing is difficult, administer oxygen. If the victim is not breathing,
perform mouth-to-mouth resuscitation. Seek medical attention.
1.3.6 Ingestion:
Do NOT induce vomiting unless directed to do so by medical personnel. Never give anything by
mouth to an unconscious person. If large quantities of this material are swallowed, call a
physician immediately. Loosen tight clothing such as a collar, tie, belt or waistband.
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1.4 Fire and Explosion Data:
1.4.1 Flammability of the Product: Flammable.
1.4.2 Auto-Ignition Temperature: 175°C (347°F) (ACGIH, 1996; Lewis, 1996; NFPA, 1994);
185 deg. C (ILO, 1998)
1.4.3 Flash Points:
CLOSED CUP: -38°C (-36.4°F) (Buvardi (1996); Clayton and Clayton, 1993; Lewis, 1996); -
38.89 deg. C (American Conference of Governmental Industrial Hygienists) OPEN CUP: -40°C
(-40°F) (Lewis, 1997; ACGIH, 1996 (Cleveland).
1.4.4 Flammable Limits:
LOWER: 4% UPPER: 55% (Clayton; Patty's Industrial Hygiene and Toxicology); 57%
(American Conference of Governmental Industrial Hygienists); 60% (National Fire Protection
Association)
1.4.5 Products of Combustion:
These products are carbon oxides (CO, CO2).
1.4.6 Fire Hazards in Presence of Various Substances:
Extremely flammable in presence of open flames and sparks, of heat. Non-flammable in
presence of shocks.
1.4.7 Explosion Hazards in Presence of Various Substances:
Risks of explosion of the product in presence of static discharge: Not available. Explosive in
presence of heat, of acids, of alkalis. Non-explosive in presence of shocks.
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1.4.8 Fire Fighting Media and Instructions:
Flammable liquid, soluble or dispersed in water. SMALL FIRE: Use DRY chemical powder.
LARGE FIRE: Use alcohol foam, water spray or fog. Cool containing vessels with water jet in
order to prevent pressure build-up, autoignition or explosion.
1.4.9 Special Remarks on Fire Hazards: When heated to decomposition it emits acrid smoke
and fumes.
1.4.10 Special Remarks on Explosion Hazards:
Hazardous or explosive polymerization may occur with acids, alkaline materials, heat, strong
bases, trace metals. Forms explosive peroxides on exposure to air, heat or sunlight.
1.5 Accidental Release Measures
1.5.1 Small Spill:
Dilute with water and mop up, or absorb with an inert dry material and place in an appropriate
waste disposal container.
1.5.2 Large Spill:
Flammable liquid. Keep away from heat. Keep away from sources of ignition. Stop leak if
without risk. Absorb with DRY earth, sand or other non-combustible material. Do not touch
spilled material. Prevent entry into sewers, basements or confined areas; dike if needed. Be
careful that the product is not present at a concentration level above TLV. Check TLV on the
MSDS and with local authorities.
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1.6 Handling and Storage
1.6.1 Precautions:
Keep locked up.. Keep away from heat. Keep away from sources of ignition. Ground all
equipment containing material. Do not ingest. Do not breathe gas/fumes/ vapor/spray. Avoid
contact with eyes. Wear suitable protective clothing. In case of insufficient ventilation, wear
suitable respiratory equipment. If ingested, seek medical advice immediately and show the
container or the label. Keep away from incompatibles such as oxidizing agents, combustible
materials, organic materials, metals, acids, alkalis.
1.6.2 Storage:
Store in a segregated and approved area. Keep container in a cool, well-ventilated area. Keep
container tightly closed and sealed until ready for use. Avoid all possible sources of ignition
(spark or flame).
1.7 Exposure Controls/Personal Protection
1.7.1 Engineering Controls:
Provide exhaust ventilation or other engineering controls to keep the airborne concentrations of
vapors below their respective threshold limit value. Ensure that eyewash stations and safety
showers are proximal to the work-station location.
1.7.2 Personal Protection: Splash goggles. Lab coat. Vapor respirator. Be sure to use an
approved/certified respirator or equivalent. Gloves (impervious).
1.7.3 Personal Protection in Case of a Large Spill:
Splash goggles. Full suit. Vapor respirator. Boots. Gloves. A self contained breathing apparatus
should be used to avoid inhalation of the product. Suggested protective clothing might not be
sufficient; consult a specialist BEFORE handling this product.
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1.7.4 Exposure Limits:
TWA: 25 (ppm) from ACGIH (TLV) [United States] TWA: 200 STEL: 150 (ppm) from OSHA
(PEL) [United States] TWA: 360
STEL: 270 (mg/m3) from OSHA (PEL) [United States] Consult local authorities for acceptable
exposure limits.
1.8 Physical and Chemical Properties
Physical state and appearance: Liquid. (Fuming liquid.)
Odor: Fruity. Pungent. (Strong.)
Taste: Leafy green
Molecular Weight: 44.05 g/mole
Color: Colorless.
pH (1% soln/water): Not available.
Boiling Point: 21°C (69.8°F)
Melting Point: -123.5°C (-190.3°F)
Critical Temperature: 188°C (370.4°F)
Specific Gravity: 0.78 (Water = 1)
Vapor Pressure: 101.3 kPa (@ 20°C)
Vapor Density: 1.52 (Air = 1)
Volatility: Not available.
Odor Threshold: 0.21 ppm
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Water/Oil Dist. Coeff.: Not available.
Ionicity (in Water): Not available.
Dispersion Properties: See solubility in water, diethyl ether, acetone.
Solubility: Easily soluble in cold water, hot water. Soluble in diethyl ether, acetone. Miscible
with benzene, gasoline, solvent naphtha, toluene, xylene, turpentine. Solubility in water: 1000 g/l
@ 25 deg. C.
1.9 Stability and Reactivity Data
1.9.1 Stability: The product is stable.
1.9.2 Conditions of Instability: Heat, igition sources (flames, sparks), incompatible materials
1.9.3 Incompatibility with various substances:
Highly reactive with metals, acids, alkalis. Reactive with oxidizing agents, combustible
materials, organic materials.
1.9.4 Corrosivity: Non-corrosive in presence of glass.
1.9.5 Special Remarks on Reactivity:
Reacts with oxidizing materials, halogens, amines, strong alkalies (bases), and acids, cobalt
acetate, phenols, ketones, ammonia, hydrogen cyanide, hydrogen sulfide, hydrogen peroxide,
mercury (II) salts (chlorate or perchlorate), acid anhydrides, alcohols, iodine, isocyanates,
phosphorus, phosphorus isocyanate, tris(2-chlorobutyl)amine. It can slowly polymerize to
paraldehyde. Polymerization may occur in presence of acid traces causing exothermic reaction,
increased vessel pressure, fire, and explosion. Impure material polymerizes readily in presence of
traces of metals (iron) or acids. Acetaldehyde is polymerized violently by concentrated sulfuric
acid. Acetaldehyde can dissolve rubber.
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1.10 Toxicological Information
1.10.1 Routes of Entry: Absorbed through skin. Eye contact. Inhalation. Ingestion.
1.10.2 Toxicity to Animals:
WARNING: THE LC50 VALUES HEREUNDER ARE ESTIMATED ON THE BASIS OF A
4-HOUR EXPOSURE. Acute oral toxicity (LD50): 661 mg/kg [Rat.]. Acute dermal toxicity
(LD50): 3540 mg/kg [Rabbit]. Acute toxicity of the vapor (LC50): 23000 mg/m3 4 hours
[Mouse].
1.10.3 Chronic Effects on Humans:
CARCINOGENIC EFFECTS: Classified 2B (Possible for human.) by IARC. MUTAGENIC
EFFECTS: Mutagenic for mammalian somatic cells. Mutagenic for bacteria and/or yeast.
TERATOGENIC EFFECTS: Classified POSSIBLE for human. May cause damage to the
following organs: liver.
1.10.4 Other Toxic Effects on Humans:
Hazardous in case of ingestion, of inhalation (lung irritant). Slightly hazardous in case of skin
contact (irritant, permeator).
1.10.5 Special Remarks on Toxicity to Animals: Not available.
1.10.6 Special Remarks on Chronic Effects on Humans:
May cause adverse reproductive effects and birth defects(teratogenic) based on animal test data
May affect genetic material (mutagenic). May cause cancer based on animal test data
1.10.7 Special Remarks on other Toxic Effects on Humans:
Acute Potential Health Effects: Skin: Causes mild skin irritation. It can be absorbed through
intact skin. Eyes: Causes severe eye irritation. Eye splashes produce painful but superficial
corneal injuries which heal rapidly. Inhalation: It causes upper respiratory tract and mucous
15
membrane irritation. It decreases the amount of pulmonary macrophages. It may cause
bronchitis. It may cause pulmonary edema, often the cause of delayed death. It may affec
respiration (dyspnea) and respiratory arrest and death may occur. It may affect behavior/central
nervous and cause central nervous system depression. Iirritation usually prevents voluntary
exposure to airborne concentrations high enough to cause CNS depression, although this effect
has occurred in experimental animals. It may also affect the peripheral nervous system and
cardiovascular system (hypotension or hypertension, tachycardia, bradycardia), kidneys
(albuminuria) Chronic Potential Health Effects: Skin: Prolonged direct skin contact causes
erythema and burns. Repeated exposure may cause dermatitis secondary to primary irritation or
sensitization. Ingestion: Symptoms of chronic Acetaldehyde exposure may resemble those of
chronic alcoholism. Acetaldehyde is the a metabolite of ethanol in humans and has been
implicated as the active agent damaging the liver in ethanol-induced liver disease.
1.11 Ecological Information
1.11.1 Products of Biodegradation:
Possibly hazardous short term degradation products are not likely. However, long term
degradation products may arise.
1.11.2 Toxicity of the Products of Biodegradation: The products of degradation are less toxic
than the product itself.
1.12 Disposal Considerations
1.12.1 Waste Disposal:
Waste must be disposed of in accordance with federal, state and local environmental control
regulations
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1.13 Transport Information
1.13.1 DOT Classification: CLASS 3: Flammable liquid.
1.13.2 Identification: : Acetaldehyde UNNA: 1089 PG: I
1.13.3 Special Provisions for Transport: Marine Pollutant
1.14 Protective Equipment:
Gloves (impervious). Lab coat. Vapor respirator. Be sure to use an approved/certified respirator
or equivalent. Wear appropriate respirator when ventilation is inadequate. Splash goggles.
17
CHAPTER2:
PROPERTIES AND USES:
18
CHAPTER 2
PROPERTIES AND USES
2.1 PHYSICAL PROPERTIES:
Acetaldehyde is a colorless, mobile liquid having a pungent suffocating odor that is somewhat
fruity and pleasant in dilute concentrations. Some physical properties of acetaldehyde The
freezing points of aqueous solutions of acetaldehyde are as follows:
4.8 wt %, -2.50C; 13.5 wt %, - 7.80 C, and 31.0 wt %, - 23.00 C.
Acetaldehyde is miscible in all proportions with water and most common organic solvents:
acetone, benzene, ethyl alcohol, ethyl ether, gasoline, paraldehyde, toluene, xylenes, turpentine,
and acetic acid.
2.2 CHEMICAL PROPERTIES:
Acetaldehyde is a highly reactive compound exhibiting the general reactions of aldehydes; under
suitable conditions, the oxygen or any hydrogen can be replaced. Acetaldehyde undergoes
numerous condensation, addition, and polymerization reactions.
2.2.1 Decomposition: Acetaldehyde decomposes at temperatures above 400°C, forming
principally methane and carbon monoxide. The activation energy of the pyrolysis reaction is 97.7
kJ/mol (408.8 kcal/mol). There have been many investigations of the photolytic and radical –
induced decomposition of acetaldehyde and deuterated acetaldehydes.
2.2.2 The Hydrate and Enol Form: In aqueous solutions, acetaldehyde exists in equilibrium
with the hydrate, CH3CH(OH)2. The degree of hydration can be computed from an equation
derived by Bell and Clunie. The mean heat of hydration is – 21.34 kJ/mol (89.29kcal/mol);
hydration has been attributed to hyper conjugation. The enol form, vinyl alcohol (CH2 = CHOH)
19
exists in equilibrium with acetaldehyde to the extent of approximately one molecule per 30,000.
Acetaldehyde enol has been acetylated with ketene to form vinyl acetate.
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2.2.3 Oxidation:
Acetaldehyde is readily oxidized with oxygen or air to acetic acid, acetic anhydride, and
peracetic acid (see Acetic acid and derivatives). The principal product isolated depends on
reaction conditions. Acetic acid is produced commercially by the liquid – phase oxidation of
acetaldehyde at 65°C with cobalt or manganese acetate dissolved in acetic acid as a catalyst.
Liquid – phase oxidation of acetaldehyde in the presence of mixed acetates of copper and cobalt
yields acetic anhydride. Peroxyacetic acid or a perester is believed to be the precursor of acetic
acid and acetic anhydride. There are two commercial processes for the production of peracetic
acid. Low temperature oxidation of acetaldehyde in the presence of metal salts, ultraviolet
irradiation, or ozone yields acetaldehyde monoperacetate, which can be decomposed to peracetic
acid and acetaldehyde. Peracetic acid can also be formed directly by liquid – phase oxidation at 5
- 50°C with a cobalt salt catalyst. The nitric acid oxidation of acetaldehyde yields glyoxal.
Oxidations of p – xylene to terephthalic acid and of ethanol to acetic acid are activated by
acetaldehyde.
2.2.4 Reduction:
Acetaldehyde is readily reduced to ethanol. Suitable catalysts for vapor-phase hydrogenation are
supported nickel and copper oxide. Oldenberg and Rose have studied the kinetics of the
hydrogenation of acetaldehyde over a commercial nickel catalyst.
2.2.5 Polymerization:
Paraldehyde,2,4,6- trimethyl – 1,3,5 – trioxan, a cyclic trimer of acetaldehyde is formed when a
mineral acid, such as sulfuric, phosphoric, or hydrochloric acid, is added to acetaldehyde.
Paraldehyde can also be formed continuously by feeding acetaldehyde as a liquid at 15 - 20°C
over an acid ion – exchange resin. Depolymerization of paraldehyde occurs in the presence of
acid catalysts. After neutralization with sodium acetate, acetaldehyde and paraldehyde are
recovered by distillation. Paraldehyde is a colorless liquid, boiling at 125.35 °Cat 101 kPa (1
atm). Metaldehyde, a cyclic tetramer of acetaldehyde, is formed at temperatures below 0°C in the
22
presence of dry hydrogen chloride or pyridine – hydrogen bromide. The metaldehyde crystallizes
from solution and is separated from the paraldehyde by filtration. Metaldehyde melts in a sealed
tube at 246.2°C and sublimes at 115 °C with partial depolymerization. Travers and Letort first
discovered Polyacetaldhyde, rubbery polymer with an acetal structure, in 1936. More recently, it
has been shown that white, nontacky, and highly elastic polymer can be formed by cationic
polymerization with BF3 in liquid ethylene. At temperatures below - 75°C with anionic
initiators, such as metal alkyls in a hydrocarbon solvent, a crystalline, isotactic polymer is
obtained. This polymer also has an acetal structure [poly (oxymethylene) structure]. Molecular
weights in the range of 800,000 – 3,000,000 have been reported. Polyacetaldehyde is unstable
and depolymerizes in a few days to acetaldehyde. The methods used for stabilizing
polyformaldehyde have not been successful with polyacetaldehyde and the polymer has no
practical significance (see Acetal resins).
2.2.6 Reactions with aldehydes and ketones:
The base catalyzed condensation of acetaldehyde leads to the dimmer, acetaldol, which can be
hydrogenated to form 1,3 butandiol or dehydrated to form crotonaldehyde. Crotonaldehyde can
also be made directly by the vapor-phase condensation of acetaldehyde over a catalyst.
Crotonaldehyde was formerly an important intermediate in the production of butyraldehyde,
butanol, and 2-ethylhexanol. However it has been replaced completely with butyraldehyde from
theoxo process. A small amount of crotonaldehyde is still required for the production of crotonic
acid.
Acetaldehyde forms aldols with other carbonyl compounds containing active hydrogen atoms.
Kinetic studies of the aldol condensation of acetaldehyde and deuterated acetaldehydes have
shown that only the hydrogen atoms bound to the carbon adjacent to the –CHO group takes part
in the condensation reactions and hydrogen exchange. A hexyl alcohol, 2-ethyl-1 butanol, is
produced, industrially by the condensation of acetaldehyde and butaraldehyde in dilute caustic
solution followed by hydrogenation of the acrolein intermediate. (see alcohols, higher aliphatic)
condensation of acetaldehyde in the presence of dimethylamine hydrochloride yields polyenals
which can be hydrogenated to a mixture of alcohols containing from 4 to 22 carbon atoms. The
base catalyzed reaction of acetaldehyde with excess formaldehyde is the commercial route to
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pentaerythritol. The aldol condensation of three moles of form aldehyde with one mole of
acetaldehyde is followed by a crossed cannizzaro reaction between pentaerythrose, the
intermediate product, and formaldehyde to give pentaerythritol. The process proceeds to
completion without isolation of the intermediate. Pantaerythrose has been made by condensing
acetaldehyde and formaldehyde at 450 C using magnesium oxide as a catalyst. The vapor-phase
reaction of acetaldehyde and formaldehyde at 450C over a catalyst composed of lanthanum
oxide on silica gel gives acrolein. Ethyl acetate is produced commercially by the Tischenko
condensation of acetaldehyde with an aluminum ethoxide catalyst. The Tischenko reaction of
acetaldehyde with isobutyraldehyde yields a mixture of ethyl acetate, isobutyl acetate, and
isobutyl isobutyrate.
2.2.7 Reactions with Ammonia and Amines:
Acetaldehyde readily adds ammonia to form acetaldehyde ammonia. Diethyl amine is obtained
when acetaldehyde is added to a saturated aqueous or alcoholic solution of ammonia and the
mixture is heated to 50-750C in the presence of a nickel catalyst and hydrogen at 1.2 MPa
(12atm). Pyridine and pyridine derivates are made from paraldehyde and aqueous ammonia in
the presence of a catalyst at elevated temperatures; acetaldehyde may also be used by the yields
of pyridine are generally lower than when paraldehyde is the staring material. Levy and Othmer
have studied the vapor- phase reaction of formaldehyde, acetaldehyde, and ammonia at 3600 C
over oxide catalysts; a 49% yield of pyridine and picolines was obtained using an activated
silica-alumina catalyst. Brown polymers result when acetaldehyde reacts with ammonia or
amines at a PH of 6-7 and temperature of 3-250C. With acetaldehyde, a primary amines can be
condensed to Schiff bases: CH3CH=NR, the schiff base rivets to the starting materials in the
presence of acids.
2.2.8 Reactions with Alcohols and Phenols:
Alcohols add readily to acetaldehyde in the presence of a trace of mineral acid to form acetals;
eg, ethanol and acetaldehyde form diethyl acetal. Similarly, cyclic acetals are formed by the
reactions with glycols and other polyhydroxy compounds; eg, the reaction of ethylene glycol and
acetaldehyde gives 2 – methyl – 1,3 – dioxolane. Mercaptals, CH3CH(SR)2, are formed in a like
24
manner by the addition of mercaptans. The formation of acetals by a noncatalytic vapor – phase
reactions of acetaldehyde and various alcohols at 3500C has been reported. Butadiene can be
made by the reaction of acetaldehyde and ethyl alcohol at temperature s above 3000C over a
tantala – silica catalyst. Aldol and crotonaldehyde are believed to be intermediates. Butyl acetate
has been prepared by the catalytic reaction of acetaldehyde with butanol at 3000C. Reaction of
one mole of acetaldehyde with excess phenol in the presence of a mineral acid catalyst gives 1,1
– bis (p-hydroxyphenyl) ethane. With acid catalysts acetaldehyde and three moles or less of
phenol yield soluble resins. Hardenable resins are difficult to produce by the alkaline
condensation of acetaldehyde and phenol as acetaldehyde tends to undergo aldol condensation
and self-resinification.
2.2.9 Reactions with Halogens and Halogen compounds:
Halogens readily replace the hydrogen atoms of the methyl group: eg, chlorine reacts with
acetaldehyde or paraldehyde at room temperature to give chloroacetaldehyde; increasing the
temperature to 700-800C gives dichloroacetaldehyde; and at a temperature of 80-900C chloral is
formed. The catalytic chlorination with an antimony powder or aluminum chloride ferric
chloride has been described. Bromal is formed by an analogous series of reactions. It has been
postulated that acetyl bromide is an intermediate in the bromination of acetaldehyde in aqueous
ethanol. The gas – phase reaction of acetaldehyde and chlorine, has prepared acetyl chloride. The
oxygen atom in acetaldehyde can be replaced by reaction of the aldehyde with phosphorus
pentachloride to produce 1,1 – dichloroethane. Hypochlorite and hypoiodite react with
acetaldehyde yielding chloroform and iodoform, respectively. Phosgene is produced by the
reaction of carbon tetrachloride with acetaldehyde in the presence of anhydrous aluminum
chloride. Chloroform reacts with acetaldehyde in the presence of potassium hydroxide and
sodium amide to form 1,1,1 – trichloro – 2- propanol.
2.2.10 Miscellaneous Reactions:
Sodium bisulfite adds to acetaldehyde to form a white
crystalline addition compound, insoluble in ethyl alcohol and ether. The bisulfite addition
compound frequently is used to isolate acetaldehyde from solution and for purification; the
25
aldehyde is regenerated with dilute acid. Hydrocyanic acid adds to acetaldehyde in the presence
of an alkali catalyst to form the cyanohydrin; the cyanohydrin may also be prepared by reaction
of sodium cyanide with the bisulfite addition compound. Acrylonitrile can be made by reaction
of acetaldehyde with hydrocyanic acid and heating the cyanohydrin to 600 – 7000C. Alanine can
be prepared by reaction of ammonium salt and alkali metalo cyanide with acetaldehyde; this is
the Strecker amino acid synthesis, a general method for the preparation of α-amino acids.
Grignard reagents add readily to acetaldehyde, the final product being a secondary alcohol.
Thioacetaldehyde is formed by reaction of acetaldehyde with hydrogen sulfide; thioacetaldehyde
polymerizes readily to the trimer.
Acetic anhydride adds to acetaldehyde forming ethylidne diacetate in the presence of dilute acid;
boron fluoride is also a catalyst for the reaction. Ethylidene diacetate is decomposed to the
anhydride and aldehyde at temperatures of 220-2680C and initial pressures of 1.5 – 6.1 kPa
(110- 160 mm Hg), or by heating to 1500C with a zinc chloride catalyst. Acetone has been
prepared in 90% yield by heating an aqueous solution of acetaldehyde to 4100C in the presence
of a catalyst. Acetaldehyde can be condensed with active methylene groups. The reaction of
isobutylene with aqueous solutions of acetaldehyde in the presence of 1-2% sulfuric acid yields
alkyl-m-dioxanes, the principal product being 2,4,4,6-tetramethyl – m dioxane in yields up to
90%.
2.3 Uses:
The manufacturers use about 95% of the acetaldehyde produced internally as an intermediate for
the production of other organic chemicals. Figure 1 illustrates the significant variety of organic
products ( and their end uses) derived from acetaldehyde. Acetic acid and acetic anhydride are
the derivatives of acetaldehyde followed by n-butanol and 2-ethylhexanol. Twenty percent of the
acetaldehyde is consumed in variety of other products, the most important being pentaerythritol,
trimethylolpropane, pyridines, peraceticacid, crotonaldehyde, chloral, lactic acid.
26
CHAPTER 3:
PROCESS JUSTIFICATION:
27
CHAPTER 3
PROCESS SELECTION AND JUSTIFICATION
MANUFACTURING PROCESSES AND SELECTION
The economics of the various processes for the manufacture of acetaldehyde are strongly
dependent on the price of the feedstock used. Since 1960, the liquid-phase oxidation of ethylene
has been the process of choice. However, there is still commercial production by the partial
oxidation of ethyl alcohol, dehydrogenation of ethyl alcohol and the hydration of acetylene.
Acetaldehyde is also formed as a co product with ethyl alcohol and acetic acid.
3.1 Oxidation of Ethylene:
Wacker – Chemie and Farbwerke Hoechst, developed the direct liquid phase oxidation of
ethylene in 1957 – 1959. The catalyst is an aqueous solution of PdCl2 and CuCl2. In 1894, F.C.
Phillips observed the reaction of ethylene with an aqueous palladium chloride solution to form
acetaldehyde.
C2H4+PdCl2 + H2O CH3CHO +Pd +2HCl
The metallic palladium is reoxidized to PdCl2 with CuCl2 and the cuprous chloride formed is
reoxidized with oxygen or air.
28
Pd + 2CuCl2 PdCl2 +2CuCl
2CuCl + 1/2 O2 + 2HCl 2CuCl2 + H2O
The net result is a process in which ethylene is oxidized continuously through a series of
oxidation – reduction reactions.
C2H4 + ½ O2 CH3CHO ΔH = -244 kJ(102.1 kcal)
Studies of the reaction mechanism of the catalytic oxidation have suggested that a cis –
hydroxyethylene – palladium π complex is formed initially, followed by an intramolecular
exchange of hydrogen and palladium to give a gem – hydroxyethyl palladium species which
leads to acetaldehyde and metallic palladium. There are two variations for the production of
acetaldehyde by the oxidation of ethylene; the two – stage process developed by Wacker –
Chemie and the one – stage process developed by Farbwerke Hoechst. In the two – stage process
ethylene and oxygen (air) react in the liquid phase in two stages. In the first stage ethylene is
almost completely converted to acetaldehyde in one pass in a tubular plug-flow reactor made of
titanium. The reaction is conducted at 125-1300C and 1.13 Mpa (150 psig) palladium and cupric
chloride catalysts. Acetaldehyde produced in the first reactor is removed from the reaction loop
by adiabatic flashing in a tower. The flash step also removes the heat of reaction. The catalyst
solution is recycled from the flash – tower base to the second stage (or oxidation) reactor where
the cuprous salt is oxidized to the cupric state with air. The high pressure off – gas from the
oxidation reactor, mostly nitrogen, is separated from the liquid – catalyst solution and scrubbed
to remove acetaldehyde before venting. A small portion of the catalyst stream is heated in the
catalyst regenerator to destroy undesirable copper oxalate. The flasher overhead is fed to a
distillation system where water is removed for recycle to the reactor system and organic
29
impurities, including chlorinated aldehydes, are separated from the purified acetaldehyde
product.
In the one-stage process ethylene, oxygen, and recycle gas are directed to a vertical reactor for
contact with the catalyst solution under slight pressure. The water evaporated during the reaction
absorbs the heat evolved, and make – up water is fed as necessary to maintain the catalytic
solution concentration. The gases are water – scrubbed and the resulting acetaldehyde solution is
fed to a distillation column. The tail gas from the scrubber is recycled to the reactor. Inerts are
eliminated from the recycle gas in a bled – stream which flows to an auxiliary reactor for
additional ethylene conversion. This oxidation process for olefins has been exploited
commercially principally for the production of acetaldehyde, but the reaction can also be applied
to the production of acetone from propylene and methyl ethyl ketone from butanes. Careful
control of the potential of the catalyst with the oxygen stream induced commercially by a
variation of this reaction.
3.2 From Ethyl Alcohol:
3.2.1 Acetaldehyde is produced commercially by the catalytic oxidation of ethyl alcohol. Passing
alcohol vapors and preheated air over a silver catalyst at 4800C carries out the oxidation.
CH3CH2OH + ½ O2 CH3CHO + H2O, ΔH = 242 kj/mol (57.84 kcal / mol)
With a multitubular reactor, conversions of 74-82% per pass can be obtained while generating
steam to be used elsewhere in the process.
3.2.2 Acetaldehyde also, produced commercially by the dehydrogenation of ethyl
alcohol.Reaction:
C2H5OH CH3CHO + H2
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Catalyst: Cu -Co-Cr2o3
Temperature: 280 – 3500 C.
Process description:
The raw material i.e., ethanol is vaporized and the vapors, so generated, are heated in a heat
exchanger to the reaction temperature by hot product stream. The product stream is cooled to –
100 C and in doing it, all unreacted ethanol and acetaldehyde are condensed. The out going
gaseous stream, containing hydrogen mainly, is scrubbed with dilute alcohol (alcohol + water) to
remove uncondensed products and the undissolved gas. The remaining pure hydrogen (98%) is
burnt in stack. Figure 2, shows the flow sheet of the process in which ethanol is vaporized in
vaporizer and heated to the reactor temperature in heat exchanger. The heated vapors are passed
through the converter. The product stream is first cooled in heat exchanger and then in
condensers using water and liquid ammonia. This condenses most of the unreacted ethanol and
the acetaldehyde formed in reactor. The escaping gas, which is almost pure hydrogen, is
scrubbed by ethanol to remove all the traces of the product. The liquid stream consisting of
mainly ethanol and acetaldehyde, is distilled in distillation column to get acetaldehyde.
3.3 From Acetylene:
Acetaldehyde has been produced commercially by the hydration of acetylene since 1916.
However, the development of the process for the direct oxidation of ethylene in the 1960s has
almost completely replaced the acetylene – based processes and in 1976 there was only small
volume production in a few European countries. In the older processes, acetylene of high purity
is passed under a pressure of 103.4 kPa (15 psi) into a vertical reactor containing a mercury
catalyst dissolved in 18-25% sulfuric acid at 70-900C.
HC = CH + H2O CH3CHO
Fresh catalyst is fed to the reactor periodically; the catalyst may be added in the mercurous form
but it has been shown that the catalytic species is a mercuric ion complex (100). The excess
31
acetylene sweeps out the dissolved acetaldehyde which is condensed by water and refrigerated
brine and scrubbed with water; the crude acetaldehyde is purified by distillation and the
unreacted acetylene is recycled. The catalytic mercuric ion is reduced to catalytically inactive
mercurous sulfate and metallic mercury; this sludge, consisting of reduced catalyst and tars, is
drained from the reactor at intervals and resulfated. Adding ferric or other salts to the reaction
solution can reduce the rate of catalyst depletion. The ferric ion reoxidizes mercurous to the
mercuric ion while it is reduced to the ferrous state; consequently, the quantity of sludge, which
must be recovered, is reduced (81,101). In one variation, acetylene is completely hydrated with
water in a single operation at 68-730C using the mercuric iron salt catalyst. The acetaldehyde is
partially removed by vacuum distillation and the mother liquor recycled to the reactor. The
aldehyde vapors are cooled to about 350C, compressed to 253 kPa (2.5 atm), and condensed. It is
claimed that this combination of vacuum and pressure operations substantially reduces heating
and refrigeration costs. Acetaldehyde may also be made from methyl vinyl ether and ethylidene
diacetate, both of which can be made from acetylene. Methyl vinyl ether is made by the addition
of methanol to acetylene at 1.62 Mpa (16 atm) in a vertical reactor containing a 20% methanolic
solution of potassium hydroxide. Hydrolysis of the ether with dilute sulfuric acid yields
acetaldehyde and methanol which are separated by distillation; the methanol is recycled to the
reactor. Acetylene and acetic acid form ethylidene diacetate in the presence of mercuric oxide
and sulfuric acid at 60-800C and atmospheric pressure. After separation, the ethylidene diacetate
is decomposed to acetaldehyde and acetic anhydride by heating to 1500C in the presence of a
zinc chloride catalyst (81). Acetaldehyde has been made from methyl vinyl ether and ethylidene
diacetate in the past, but neither process is used today.
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3.4 From Saturated Hydrocarbons:
Acetaldehyde is formed as a co product in the vapor – phase oxidation of saturated
hydrocarbons, such as butane or mixtures containing butane, with air or, in higher yield, oxygen.
Oxidation of butane yields acetaldehyde, formaldehyde, methanol, acetone, and mixed solvents
as major products; other aldehydes, alcohols, ketones, glycols, acetals, epoxides, and organic
acids are formed in smaller concentrations. This is of historic interest. Unlike the acetylene route,
it has almost no chance to be used as a major process.
From synthesis Gas: A rhodium-catalyzed process capable of converting synthesis gas directly
into acetaldehyde in a single step was reported in 1974 (84-85).
CO + H2 CH3CHO + other products
The process comprises passing synthesis gas over 5% rhodium on SiO2 at 300 0C and 2.0 Mpa
(20 atm). The principal co products are acetaldehyde, 24% acetic acid, 20%; and ethanol, 16%.
In the years 1980 and beyond, if there will be a substantial degree of coal gasification, the
interest in the use of synthesis gas as a raw material for acetaldehyde production will
increase.
3.5 Specifications, Analytical, and Test Methods:
Commercial acetaldehyde has the following typical specifications: assay, 99% min; color, water-
white; acidity, 0.5% max (acetic acid); specific gravity, 0.790 at 200C; bp, 20.8 at 101.3 kPa (1
atm). Acetaldehyde is shipped in steel drums and tank cars bearing the ICC red label. IN the
liquid state, it is noncorrosive to most metals; however,
33
it oxidizes readily, particularly in the vapor state, to acetic acid. Precautions to be observed in the
handling of acetaldehyde have been published by the manufacturing chemists association.
Analytical methods based on many of the reactions common to aldehydes have been developed
for the determination of acetaldehyde. In the absence of other aldehydes, it can be detected by
the formation of a mirror from an alkaline silver nitrate solution (Tollens’ reagent) and by the
reduction of Fehling’s solution. It can be determined quantitatively by fuchsin-sulfiur dioxide
solution (Schiff’s reagent) or by the reaction with sodium bisulfite, the excess bisulfite being
estimated iodometrically. Acetaldehyde present in mixtures with other carbonyl compounds,
organic acids, etc. can be determined by paper chromatography of 2,4 – dinitrophenylhydrazones
polarographic analysis either of the untreated mixture or of the semicarbazones, the color
reaction with thymol blue on silica gel (detector tube method) mercurimetric oxidation,
argentometric titration, microscopic and spectrophotometric methods, and gas – liquid
chromatographic analysis. With the advent of gas – liquid chromatographic techniques, this
method has superseded most chemical tests for routine analysis. Acetaldehyde can be isolated
and identified by the crystalline compounds of characteristic melting points formed with
hydrazine’s, semicasrbazides, etc.; these derivatives of aldehydes can be separated by paper and
column chromatography. Acetaldehyde has been separated quantitatively from other carbonyl
compounds on an ion exchange resin in the bisulfite form; the aldehyde is eluted from the
column with a solution of sodium chloride. In larger quantities, it may be isolated by passing the
vapor into ether and saturating the ether with dry ammonia; the product, acetaldehyde –
ammonia, crystallizes from the ether solution. The reactions of acetaldehyde with bisulfite,
hydrazine’s, oximes, semicarbazones, and 5,5–dimethyl – 1,3 cyclohexanedione (dimedone)
have been used to isolate acetaldehyde from solutions.
3.6 PROCESS SELECTION:
Here, ethyl alcohol dehydrogenation is selected for the production of acetaldehyde. Because, in
this process, hydrogen is taken out as a by-product which can be used else where or which can be
used to generate heat. In dehydrogenation process more conversion-taking place compared to
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other processes. The dehydrogenation catalyst has a life of several years but requires periodic
reactivation. In dehydrogenation process,
number of products are less, so separation of acetaldehyde from other product is not a difficult
problem.
CHAPTER 4:
PROCESS DESCRIPTION:
35
CHAPTER 4
PROCESS DECRIPTION
Acetaldehyde Production by Ethanol Dehydrogenation
Background
Acetaldehyde is a colorless liquid with a pungent, fruity odor. It is primarily used as a chemical
intermediate, principally for the production of acetic acid, pyridine and pyridine bases, peracetic
acid, pentaeythritol, butylene glycol, and chloral. Acetaldehyde is a volatile and flammable
liquid that is miscible in water, alcohol, ether, benzene, gasoline, and other common organic
solvents. The goal of this project is to design a grass-roots facility that is capable of producing
95,000 tons of acetaldehyde per year by ethanol dehydrogenation.
Process Description
A preliminary base case BFD for the overall process is shown in Figure 1. Unit 100 A PFD of
Unit 100 is shown in Figure 2. Ethanol, an 85-wt.% solution in water, Stream 1, is combined
with 85-wt.% ethanol recycle stream, Stream 23, from Unit 200. The resultant stream, Stream 2,
is then pumped to 100 psia and heated to 626°F in E-101 and E-102 before being fed to R-101,
an isothermal, catalytic, packed-bed reactor, where the ethanol is dehydrogenated to form
acetaldehyde. The reactor effluent is then cooled in E-103 and E-104. The resultant two-phase
stream, Stream 8, is then separated in V- 101. The vapor, Stream 9, is sent to T-101 where it is
contacted with water, which absorbs the acetaldehyde and ethanol from the vapor stream. The
resulting vapor effluent, Stream 11, is then sent for further processing and recovery of valuable 2
hydrogen. Alternatively, this stream could be used as fuel. Stream 12, the liquid, is combined
36
with Stream 14, the liquid effluent from V-101, and sent to Unit 200. Unit 200 A PFD for Unit
200 is shown in Figure 3. Stream 15 enters T-201 where the crude acetaldehyde, Stream 16, exits
as the distillate. This crude acetaldehyde is then sent to T-203 where the acetaldehyde is purified
to 99.9-wt.%, Stream 17. The bottoms, Stream 18, is sent to waste treatment. The bottoms from
T-201, Stream 19, is sent to T-202 to begin the purification process of ethanol. In T-202, ethyl
acetate and some water is removed from Stream 19 and exits as the distillate, Stream 20, which
is then sent to waste treatment. The bottoms, Stream 21, is sent to T-204 where ethanol is
separated from butanol, ethyl acetate, and most of the water. These impurities exit in Stream 22
and are sent to waste treatment. The distillate consists of an 85-wt.% solution of ethanol, which
is then recycled back to Unit 100 to be used in the feed. Waste streams, Streams 18, 20, and 22,
all contain small quantities of valuable chemicals. Methods for their separation and purification
should be investigated.
Necessary Information and Simulation Hints
The following reactions occur during the dehydrogenation of ethanol:
CH3CH2OH CH3CHO + H2O (1)
2CH3CH2OH CH3COOC2H5 + 2H2 (2)
2CH3CH2OH CH3(CH2)3OH + H2O (3)
CH3CH2OH + H2O CH3COOH + 2H2 (4)
The conversion of ethanol is assumed to be 60.8%. The yields for each reaction are as
follows:
(1) acetaldehyde 91.7%
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(2) ethyl acetate 3.8%
(3) butanol 2.4%
(4) acetic acid 2.1%
References are not available for these values. Since reaction kinetics were not available, the
above conversions were assumed in the design of the process. NRTL thermodynamics was used
for K-values, as suggested by the Chemcad expert system.\
Equipment Summary
E-101 Reactor Preheater
E-102 Reactor Preheater
E-103 Heat Exchanger
E-104 Heat Exchanger
E-105 Heat Exchanger
E-201 Condenser
E-202 Reboiler
E-203 Condenser
E-204 Reboiler
E-205 Condenser
E-206 Reboiler
E-207 Condenser
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E-208 Reboiler
H-101 Fired Heater
P-101A/B Feed Pump
P-102A/B Dowtherm A Pump
P-201A/B Reflux Pump
P-202A/B Reflux Pump
P-203A/B Reflux Pump
P-204A/B Reflux Pump
T-101 Absorber
T-201 Distillation Column
T-202 Distillation Column
T-203 Distillation Column
T-204 Distillation Column
V-101 Flash Vessel
V-201 Reflux Vessel
V-202 Reflux Vessel
V-203 Reflux Vessel
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