Department of Chemical Engineering, IT GGV, Bilaspur ... · Department of Chemical Engineering, IT GGV, Bilaspur ... A. triglyceride B. fatty acids ... Methyl ester is hydrolyzed

Model Answer: B.Tech. IV Sem (Chemical Engg.)- Organic Chemical Technology, (AR-9094) 2013

Department of Chemical Engineering, IT GGV, Bilaspur B. Tech. IV Sem.

Organic Chemical Technology (Paper Code: AR-9094)

Section-A Q1. Choose the correct answer: (i) The basic constituent of vegetable oils is A. triglyceride B. fatty acids C. fatty alcohol D. mono esters Ans: A (ii) Solvent used for extraction of oil is A. hexane B. methyl ethyl ketone C. furfurol D. none of these Ans: A (iii) Which of the following is a detergent ? A. Benzene hexachloride B. Alkyl benzene sulphonate C. Polytetraflouroethylene D. Cellulose nitrate Ans: B (iv) Metallic soap (e.g. aluminium or calcium salts of fatty acids) can be used A. as a lubricant. B. as a rust preventive. C. in hard water for cleaning of cloth. D. as a foam depressant in distillation column. Ans: A (v) Wood charcoal is used for decolorization of sugar, because it __________ the coloured materials. A. adsorbs B. oxidises C. reduces D. converts Ans: A (vi) Fermentation of molasses to produce ethyl alcohol is done at __________ °C A. 20 - 30 B. < - 5 C. 100 - 150 D. 250 - 300 Ans: A (vii) Neoprene is the trade name of A. polyurethane B. phenol formaldehyde C. polychloroprene D. styrene-butadiene rubber Ans: C (viii) Polycaprolactum is commercially known as A. nylon-6 B. nylon-66 C. Dacron D. rayon Ans: A (ix) In sulphate pulp manufacture, the pressure and temperature in the digestor is A. 10 atm., 800 °C B. 10 atm., 170-180°C C. 1 atm., 170 - 180°C D. 1 atm., 800°C Ans: B


(x) Which oil is preferred for paint manufacture? A. Drying oil B. Non-drying oil C. Semi-drying oil D. Saturated oil Ans: A

Section-B

Unit-I

Q2. Describe the oil extraction process by mechanical extraction method with flow sheet and also describe the refining of oil.

Answer: Mechanical Extraction Method: first of all oil seeds are mechanically cleaned to remove stone and other

undesirable materials then dehulled to remove husks and dry outer covering of seeds. Cleaned seeds then sent to the crushing rolls to reduce its size upto 0.25 mm. Then flaked seeds sent to the digester where 100 parts of flaked seeds mixed with 5-10 parts of water by rotating blenders, steam is added for heating. Here acid is formed by hydrolysis of ester and seeds are swollen up. The swollen seeds are crushed under great pressure by this Cells of seeds get ruptured and oil is released. The oil depleted cake is either sent for solvent extraction or used as animal feed.

Refining of Oil: The extracted oil is treated with alkali like NaOH or Na2CO3 to remove fatty acids. It also

removes heavy metals, which can start oxidation of oil. Acids are separated in centrifuge separator. These separated acids are used as foots for soap manufacturing. The clear oil is treated with some bleaching agent like "Fullers Earth Carbon” in filter aid before rotary filter. Rotary drum filter is used for removal of seed particles which may be present. This finished oil is produced. From this process around 1-2% oil content remains in the meal.

Flow sheet for the Mechanical Extraction of oil and refining:


OR Write short notes on the following: (i) Chemical composition & physical properties of vegetable oils (ii) Nickel catalyst preparation for hydrogenation of oil Answer: (i) Chemical Composition and physical properties of vegetable oils: (a) Fats and Oils: oils and fats are the mixtures of glycerides of fatty acids which has the structure as

shown below, where R1, R2 and R3 are not necessarily the same.

At normal temperature and pressure oils are all liquid and fats are solid. (b) Effect of degree of saturation: number of double bonds in the fatty acid radical (R) controls the

melting point and chemical reactivity of oils and fats and shown in the table:

R Number of double bonds

Melting point, 0C

Reactivity to oxygen Name Composition

Stearic C17H35 0 69 Nil

Oleic C17H33 1 14 Fair

Linoleic C17H31 2 -5 Rapid

Linolenic C17H29 3 -11 Extremely rapid

The ability to react with oxygen enhances the use of unsaturated fatty acids as film forming

vehicles for paints. It is also cause the rancidity in edible fat products which can be avoided be us of:

Hydrogenation: removes ractive double bonds. Antioxidants: compounds which oxidize preferentially to fats without much increase in color or

odor.

(ii) Nickel catalyst preparation for hydrogenation of oil: (a) Nickel formate decomposition:

Reaction shown above is the decomposition of nickel formate which produces a finely divided

catalyst which is preferred for well-stirred hydrogenation reactors.

(b) Reduced Ni on inert catalyst support

1900C

R1 . CO . O. CH2

R2 . CO . O. CH

R3 . CO . O. CH2


Nickel salts are precipitated on inert porous carrier such as kieselguhr or diatomaceous earth and reduced at high temperature in a hydrogen atmosphere.

(c) Raney or spongy nickel method:

Alloy of aluminum and nickel is reacts with sodium hydroxide to give the spongy, high-surface area catalyst.

Unit-II

Q3. Describe the hydrogenolysis of methyl esters to obtain fatty alcohols and glycerin from natural fats

with flow sheet. Answer:

Methyl esters have increasingly replaced fatty acids as starting materials for many oleochemicals. The use of methyl esters instead of fatty acids as starting materials for many oleochemicals is rapidly gaining ground because of the following advantages 1. Lower energy consumption. 2. Less expensive equipment. 3. More concentrated glycerine byproduct 4. Easier to distill–fractionate. Methyl ester are prepared by reacting methanol with coconut triglyceride, catalyzed by small amount of sodium methylate as follows:

Methyl ester is hydrolyzed to give fatty alcohols and methanol

Process: in this process the catalyst is slurries with a small amount of the methyl ester and then fed into the reactor together with the rest of the preheated ester. Hydrogen is also fed into the reactor after preheating. The catalyst amount is atleast 2% and hydrogen (20 moles/mole of methyl ester) is bubbled through to agitate the reactant. From the column the reaction mixture is sent to the separator after cooling, where hydrogen gas is separated from the alcohol-methanol mixture. The hydrogen gas is recycled and the alcohol-methanol mixture sent to the methanol stripping unit where, methanol is tripped off at low pressure and recycled to the reactor. The crude fatty alcohol is filtered to separate the catalyst. A major portion of the catalyst is recycled.


OR

Describe the continuous hydrolysis and saponification process for soap manufacturing as follows (i) Advantages over other methods (ii) Reactions (iii) Raw Materials (iv) Quantitative requirements Answer: Continuous hydrolysis and saponification process:

(i) Advantages over other methods: this method is in greater use because it has the following advantanges over other processes:

Flexibility in control of product distribution.

Higher yields (> 80%).

Less off-color product.

Requires less space and manpower

(ii) Chemical Reactions: Fat splitting reaction:

(iii) Raw materials: refined tallow, recovered and refined grease, coconut and palm oils are the principal fatty constituents. Metal oxides such as ZnO are frequently added as fat splitting


catalysts. Alkali for saponification and builder-type additives, mainly rosin, complete the raw material requirements. Caustic soda and vegetable oil are the two raw materials for the production of toilet soaps as the use of animal tallow is not allowed in India.

(iv) Quantitative requirements: Basis: 1 ton of anhydrous soap Oil or fat 1.1 tons 50% NaOH 0.3 ton Sodium silicate 6 kg H2O 0.8 ton Steam 1.5 tones Plant capacity: 2-15 tons/day

Unit-III

Q4. Briefly describe the various equipments used in manufacturing ethyl alcohol by fermentation from molasses.

Answer: Various Equipments and their functions used in ethanol production from molasses:

(a) Molasses storage tank: it is used to store the molasses obtained from the sugar industry as byproduct. Molasses is a heavy viscous material ,which contains sucrose, fructose and glucose (invert sugar) at a concentration of 50-60(wt/vol).

(b) Sterlization tank: Yeast is sterilized under pressure and then cooled to remove the unwanted impurities.

(c) Yeast cultivation tank: here Yeast grows in the presence of oxygen by budding. (d) Yeast storage tank: Yeasts are unicellular, oval and 0.004 to 0.010mm in diameter. PH is adjusted to

4.8 to 5 and temperature up to 32˚C. (e) Fermentation tank: Chemical changes are brought by the action of enzymes invertase and zymase

secreted by yeast in molasses in anaerobic conditions. Heat is evolved which is removed by cooling coils. Residence time is 30-70 hours and temperature is maintained at 20-30˚C. 8-10% alcohol by volume (beer) is produced by fermentation process. HCl or sulfuric acid is added to obtain 4.5 PH.

(f) Diluter: here Here molasses is diluted to 10 to 15% sugar solution. (g) Scrubber: Carbon dioxide is released from the fermentation tank which scrubbed and utilized as by

product. By-product CO2 contains some ethanol due to Vapor liquid evaporation and can be recovered by water scrubbing. Water is sent back to continuous diluter stream.

(h) Beer still: here 50-60% concentration alcohol and aldehyde is produced by distillation. Slops containing proteins, sugar and vitamins are removed as bottom product which is concentrated by evaporation and used as cattle feed or discharge as waste.

(i) Aldehyde still: Undesirable volatile liquid; aldehyde is taken off from the top of the still. From the side stream alcohol is feed to the decanter. It is extractive distillation column, and operates at a pressure of around 0.6-0.7 MPa.

(j) Decanter : Fusel oil which is high molecular weight alcohol is recovered by decantation. Fusel oil is fractionated to produce amyl alcohol or are sold directly. The principle behind extraction of- fusel oil from ethanol is that higher alcohols are more volatile than ethanol in solution containing a high concentration of water.

(k) Rectifying column: In the column, azeotropic alcohol- water mixture of 95% ethanol is withdrawn as side product. This 95% ethanol is condensed in condenser and stored in storage tank. Side stream is


withdrawn and sent to decanter. At the bottom, water is discharged. Here, alcohol – water mixtures are rectified to increase the strength of alcohol.

(l) Storage tank: From storage tank, three streams are evolved:

Direct sale as portable.

For industrial use.

To anhydrous still to produce 100% ethanol. (m) Mix tank: For producing denatured alcohol, denaturant is mixed with the 95% ethanol produced

from rectifying column. Denaturant is normally methanol (10vol%) (n) Ternary Azeotropic distillation: The product from rectifying column is a ternary minimum boiling

azeotrope of ethanol, water and benzene. Here Benzene is used as an azeotropic agent. Here mainly two units are present; anhydrous still, decanter, stripper and few heat exchangers. Anhydrous motor fuel grade ethanol (100% ethanol) is produced as product.

OR

Explain the cane sugar refining process also describe the various equipments used in this process. Answer: Cane Sugar Refining:

Cane sugar obtained from the sugar cane is brown in color and having the impurities which refined to get the white sugar. Cane sugar refining can be divided into the following parts:

Affination: raw cane sugar is made up of sugar crystals that have thin film impurities on the surface. It is mixed with hot impure syrup which softens the film. This mixture is known as magma, a dark brown viscous mass. This magma is fed into the centrifuge where raw crystal sugar separates from the impure raw syrup. The sugar is sprayed with water for a few seconds during the spinning, which helps to remove the last traces of impure syrup. The clean raw sugar crystals are then dissolved in water to produce raw melted liquor.

Carbonation: milk of lime is mixed with the raw melted liquor. CO2 is bubbled through the mixture,

which reacts with the lime to form chalk which attracts the waxes gums, resins and other impurities.

The mixture (carbonated liquor) is then passes through the filter presses, where the liquor is

filtered. This removes the chalk and about half of the color, together with virtually all the fine debris and solid matter.

Decolorization: the filtered liquor from the carbonation is passed through the bed of granulated

activated carbon which removes more color. The carbon is regenerated in a hot kiln where

the color is burnt off from the carbon. The decolorized solution is known as fine liquor.

Evaporation and Crystallization: the fine liquor is concentrated by evaporator upto 74%, which is then sent to large vacuum pan where the sugar crystals are grown. The syrup is heated indirectly by steam to about 800C where it boils due to vacuum applied to the vessel. The use of a vacuum and the resulting reducing temperature helps to minimize the creation of color during the process.


Separation and drying: the mixture of sugar crystals and liquor (massecuite) is centrifuged to separate the white sugar crystals. The separated liquor, which still contains significant amounts of sugar, is sent to a second and then a third crystallization step to extract more stable sugar from the syrup. The separated white sugar crystals still have 1% moisture, which is removed by dryer.

Various equipments used in this process:

Bin: to store the raw crystal sugar.

Screw Conveyor: to mix the syrup with crystal and transportation.

Centrifuger: to separate the syrup containing impurities from crystal surgar.

Melter: to mix the crystal sugar with water to get dilute sugar.

Carbonation tank: here the reaction between lime and CO2 is occurred and CaCO3 is formed.

Filter press: to separate the calcium carbonate and other impurities as cake from sugar solution.

Adsorber: here GAC is used to adsorb the color causing compound.

Evaporator and crystallizer: here the solution is concentrated and sugar crystals are formed.

Unit-IV

Q5. Explain the basic chemistry of epoxy polymers, also describe the manufacturing process. Answer: Basic Chemistry:

(a) Epoxidation is the addition of an oxygen atom across a C=C to give,

The oxygen transfer agent can be peracids such as peracetic acid, hydrogen peroxide or

chlorhydrin followed by HCl removal. The latter gives epichlorhydrin.

(b) Epoxide polymer contain an epoxy group at the ends of the polymer. For example, the reaction of epichlorhydrin with bisphenol-A (prepared by condensation of acetone with phenol) is condensation with loss of HCl.

C C

O

CH2 = CH - CH3 + Cl2 CH2 = CH - CH2Cl Allyl Chloride

HOCl

CH2 - Cl CH OH CH2Cl -HCl

CH2 = CH - CH2Cl

O

Epichlorohydrin


(c) Epoxy monomer can be obtained from unsaturated natural products such as vegetable oils, and tall

oil from wood pulping. The molecular structure of polymers from epoxidized natural product monomers is extremely complex. Both linear and cross-linked polymers are possible.

Methods of production:

Epoxy polymers are manufactured largely by batch processing because of low tonnage, multiple formulation marketing. Increased demand of several epoxy resins has led to the development of continuous processing, using two or more mixing reactors in series. Epoxy polymer processes are relatively simple and use the solvent polymerization method. Unsaturates, epoxidizing agent, and solvent are contacted on a programmed addition schedule for given time-temperature conditions. Water or other condensibles and solvents are removed and the solid or oil resin fraction is given a final purification and drying.

OR

Describe the manufacturing of viscose rayon as follows: (a) Chemical Reactions (b) Process Description (c) flow sheet Answer: (i) Chemical Reactions: the raw material for the production of Viscose rayon is wood pulp. It involves the

reaction between cellulose and alkali, which gives the alkali cellulose. Alkali cellulose is solubilized with CS2 to give sodium cellulose xanthate. Acid regeneration of sodium cellulose xanthate produces the rayon of regenerated cellulose as follows:

(a) Alkali Conversion-

Cellulose Alkali Cellulose (b) CS2 Solubilization-

Sodium Cellulose Xanthate (c) Acid Regeneration-

Rayon or regenerated Cellulose

(ii) Process Description: The raw materials used in this process are cellulose wood pulp sheets or cotton linters. These are placed in a steeping press with contact in aqueous NaOH Solution for a period of 2 – 4 hours at normal room temperature. A hydraulic ram presses out the excess alkali and the sheets are shredded to crumbs and aged for 2 – 3 days. The aging process has its direct consequence on the viscosity of the solution.

Later CS2 is added in a rotating drum mixer over a period of 3 hours. The orange cellulose xanthate which forms is transferred to a solubilizer , wherein it is mixed into dilute caustic .

CH2 = CH - CH2Cl

O

HO OH C

CH3

CH3

+

-HCl

O O - CH2CHOH - CH2 C

CH3

CH3

n

CH2 = CH - CH2-

O


The mixing of cellulose xanthate and dilute caustic yields a orange colored viscous solution which contains 7 – 8 % cellulose and 6.5 – 7 % NaOH. It is digested at room temperature for 4-5 days. Thereafter, the solution is filtered and fed to spinning machines.

The spinning is carried out in extrusion spinnerettes , which are made up of platinum or gold alloys. The orifices of these spinnerets have a diameter of 0.1 – 0.2 mm. for continuous filament yarns and of diameter 0.05 – 0.1 mm for short fibre shapes. The solution extruded from the spinnerette is contacted with an acid bath which precipitates the filaments without causing them to break or stick together. The processing treatments of washing, desulphurizing, bleaching and conditioning takes place continuously and in order after the filaments are wound on a series of plastic rolls.

Unit-V

Q6. Write the chemical reactions and draw flow sheet involved in Sulfate Kraft Process of pulp manufacturing. Answer: It is the most popularly used process for manufacturing pulp. This is an alkaline process as Na2SO4 is added to the cooking liquor. So its common name is sulfate process. The presence of sodium sulfide makes bleaching of pulp easier and the paper produced has better strength. Chemical reactions involved

(i) Digestion (hydrolysis and solubilization of lignin)

R-R’ + NaOH → R”COONa + ROH

R-R’ + Na2S → Mercaptans


(ii) Chemical recovery from black liquor (a) Smelting 2NaR (lignin salt) + air → Na2CO3 + CO2

Na2SO4 + 2C → Na2S + 2CO2 (from R) (white liquor)

(b) Causticizing

Na2CO3 (aq) + Ca(OH)2 (s) → 2NaOH (aq) + CaCO3 (s) (green liquor) (white liquor)

CaCO3 → CaO + CO2 CaO + H2O → Ca(OH)2

Flow sheet for manufacturing of pulp from wood chips:

OR

Describe the general paint manufacturing process with flow sheet.

Answer:

General paint manufacturing process:

Paint manufacturing process involves the various mechanical operation and only physical changes.

Chemical conversions are involved in the manufacture of the constituents of paints as well as in the

drying of film. Flow sheet for the manufacturing of paint is shown below:


Various constituents like, oil, resins, pigments, etc. are weighed, assembled and mixed on the top

floor. The mixer may be large kneader with sigma blade. The batch masses are then conveyed to the

floor below, where further grinding and further mixing takes place. Grinding mills widely used are

Buhrstone mill.

After mixing and grinding, the paint is transferred to the next floor, where it is thinned in agitated

tanks, which may hold batches of several thousand liters. The liquid paint is transferred into a hopper

tank and then poured into cans or drum, labeled, packed and moved to storage and shipping section.

Sometimes pressure filtration is applied after thinning to remove non-dispersed pigments.

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Department of Chemical Engineering, IT GGV, Bilaspur ... · Department of Chemical Engineering, IT GGV, Bilaspur ... A. triglyceride B. fatty acids ... Methyl ester is hydrolyzed