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.

2

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

3

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

4

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.

6

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.

7

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.

8

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.

9

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.

10

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.

11

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.

12

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

13

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.

14

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.

20

21

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

23

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

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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

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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,

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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:

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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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