Alcohol

ALCALCOHOHOLOL

•What is Alcohol ?

•How is it made ?

•How is it used ?

WHAT IS WHAT IS ALCOHOL ?ALCOHOL ?

• Alcohol is any organic compound in which a hydroxyl group (-OH) is bound to a carbon atom of an alkyl or substituted alkyl group.

CCnnHH2n+12n+1OH. OH. • In common terms, the word alcohol

refers to ethanol, the type of alcohol found in alcoholic beverages.

The carbon atom is bound to hydrogen atoms and may bind to other carbon atom(s) to form a carbon chain. Methanol, an

alcohol with a single carbon atom, is pictured

Ethanol is a colorless, volatile liquid with a mild odor which can be obtained by the fermentation of sugars. (Industrially, it is more commonly obtained by ethylene hydration—the reaction of ethylene with water in the presence of phosphoric acid.

Other alcohols are usually described with a clarifying adjective, as in isopropyl alcohol (propan-2-ol) or wood alcohol (methyl alcohol, or methanol). The suffix -ol appears in the IUPAC chemical name of all alcohols.

Two other alcohols whose uses are relatively widespread (though not so much as those of methanol and ethanol) are propanol and butanol. Like ethanol, they can be produced by fermentation processes. (However, the fermenting agent is a bacterium, Clostridium acetobutylicum, that feeds on cellulose, not sugars like the Saccharomyces yeast that produces ethanol.)

BASIC CLASSIFICATION

• Primary alcohol (1°)- Have general formulas RCH2OH

• Secondary alcohol (2°)- Have general formulas RR'CHOH

• Tertiary alcohol (3°)- Have general formulas RR'RCOH

• Hydrogen bond strength order: 1°>2°>3° Boiling point order: 1°>2°>3° Acidity order: 1°>2°>3°

PHYSICALPHYSICAL AND AND

CHEMICAL CHEMICAL PROPERTIESPROPERTIES

• Alcohols have an odor that is often described as “biting” and as “hanging” in the nasal passages.• The hydroxyl group generally makes the

alcohol molecule polar. Those groups can form hydrogen bonds to one another and to other compounds. Two opposing solubility trends in alcohols are: the tendency of the polar OH to promote solubility in water, and of the carbon chain to resist it..

• Methanol, ethanol, and propanol are miscible in water because the hydroxyl group wins out over the short carbon chain. Butanol, is moderately soluble because of a balance between the two trends. Alcohols of five or more carbons (Pentanol&higher) are effectively insoluble in water because of the hydrocarbon chain's dominance. All simple alcohols are miscible in organic solvents.

• Because of hydrogen bonding, alcohols tend to have higher boiling points than comparable hydrocarbons and ethers. The boiling point of the alcohol ethanol is 78.29 °C, compared to 69 °C for the hydrocarbon Hexane (a common constituent of gasoline), and 34.6 °C for Diethyl ether.

• Alcohols, like water, can show either acidic or basic properties at the O-H group. With a pKa of around 16-19 they are generally slightly weaker acids than water, but they are still able to react with strong bases such as sodium hydride or reactive metals such as sodium. The salts that result are called alkoxides, with the general formula RO- M+.

•Meanwhile the oxygen atom has lone pairs of nonbonded electrons that render it weakly basic in the presence of strong acids such as sulfuric acid.

For example, with methanol:

• Alcohols can also undergo oxidation to give aldehydes, ketones or carboxylic acids, or they can be dehydrated to alkenes.• They can react to form ester

compounds, and they can undergo nucleophilic substitution reactions. • The lone pairs of electrons on the

oxygen of the hydroxyl group also makes alcohols nucleophiles.

HOW IS IT MADE ?

Industrial Alcohol (Ethyl

Alcohol) Production

•Production of ethyl alcohol from microbial fermentation using variety of cheap sugary substrates is still commercially important.

• It is imperative that the microorganisms used must have a high tolerance for alcohol, must grow vigorously and produce a large quantity of alcohol.

• Yeasts, particularly Saccharomyces cerevisiae, represent the best known microorganisms used in the production of ethyl alcohol.

• Some of the inexpensive substrates used in alcohol industry are molasses from cane sugar or waste sulphite liquor from paper industries.

• Starch yielding grams (corn), potatoes, grapes may also be used as substrate if their prices permit.

• Some countries used sugarbeet for the purpose.

• Reaction. The chemical reaction that results in the microbial fermentation of carbohydrate into alcohol can be represented as follows.

Commercial Production using Molasses as Raw Material

• Molasses contain about 50% fermentable carbohydrates (sugars).

• Big deep tanks of steel or stainless steel are used as containers in the industrial production method

• Molasses is diluted to a suitable sugar concentration (15-16%); a small quantity of nitrogen source (e.g., ammonium phosphate, urea.

Contd.

• Ammonium suphate) and sulphuric acid (H2SO4) is added in it.

• pH of this medium is maintained at about 5.0 and an actively growing Saccharomyces cerevisiae culture is added in it.

Contd….

• The fermentation starts and is allowed to proceeding for about 24-40 hours at about 25-300C temperature. The yield of ethyl alcohol ranges about 50% of the fermentable sugar concentration present in the medium.

• The large amount of CO2 which is produced during the fermentation process as a result of decarboxylation is recovered and compressed to its solid state. The yeast recovered is usually used as an animal feed.

Steps in the Manufacture of Ethyl Alcohol using Molasses as Fermentation Substrate

• Commercial Production using Starch as Raw MaterialWhen starches such as corn are used as the raw material they have first to be hydrolysed to release simple fermentable sugars. The hydrolysis can be accomplished with enzymes from barley malt or moulds (e.g., Aspergillus oryzae) or by heat-treatment of acidified material. After the simple fermentable sugars are obtained, the fermentation process proceeds similarly to that of molasses.

Commercial Production of Alcohol from Molasses

Steps in the Manufacture of Ethyl Alcohol Starch as Raw Material

REVISTEDREVISTED ELABORATELYELABORATELY

FERMENTATION

• All that is necessary to begin fermentation is to mix the activated yeast and the cooled, pH-adjusted

• mash in the fermentation tank. Aside from the considerations of pH as discussed earlier, the most

• important thing during the fermentation is temperature control. When the fermentation begins, carbon

• dioxide gas will be given off. At the height of fermentation, the mash will literally "boil" from the

• carbon dioxide produced. The reaction also produces some heat. The optimum temperature for the

• fermentation process is between 70-85 deg F., and it is desirable not to let the temperature go much

• above 90-95 deg F.

• SUGAR/STARCH CONTENT vs ALCOHOL• On the average, the amount of alcohol that can be produced

from a given feedstock will be about half• (on a weight/weight basis) of the convertible starch or sugar

content. Ethanol weighs about 6.6 pounds• per gallon. A ton of grapes, for example, with a 15% sugar

content is capable (assuming 100%• extraction) of producing about 150 pounds or 22.7 gallons of

alcohol. Corn, with 66% convertible• starch should produce 660 pounds or 100 gallons.

• SACCHARINE MATERIALS• The process of fermenting saccharine materials is relatively

simple and straightforward. The steps• involved are usually: (1) extracting or crushing, (2) pH

adjustment through acid or backslopping, and• (3) fermentation. Dilution is usually not necessary because

the extracted juices often contain less than• the 20% maximum of fermentable material. Exceptions to the

above are the various types of molasses• that do not require extraction, but usually require dilution.

• FRUITS• The following are some fruits and their average sugar content: grapes,

15.0%; bananas, 13.8%; apples,• 12.2%; pineapples, 11.7%; pears, 10.0%; peaches, 7.6%; oranges, 5.4%;

prickly pear, 4.2%;• watermelon, 2.5%; and tomatoes, 2.0%.• Allowing 75% extraction with apples, for example, the total fermentable

material would be about 9%• of the original weight. On this basis, a ton of apples would yield about 13

gallons of alcohol. Assuming• an 80% extraction with grapes, a ton should yield about 17 gallons. With

watermelons and a 90%• extraction, a ton would yield only about 3 or 3-1/2 gallons.

DISTILLATION DISTILLATION AND AND

ALCOHOL ALCOHOL PRODUCTION PRODUCTION APPLICAITONAPPLICAITON

Distillation and Alcohol Production Application

• Distillation process• Types of distillation• Distillation equipments and properties of

them• Alcohol production• Distillation of alcohol • Types of alcohol distillation

Distillation

• Distillation is a kind of seperation technique of two or more volatile liquid compunds by using the difference in boiling points and relative volatility.

• The process takes place in a column, and two heat exchangers.

• In the column two phases, liquid and gas, are distributed to enrich the vapor in more volatile compounds and enrich the liquid phase on less volatile compounds.

• Mass transfer is the key to a successful distillation.

REFLUX

Advantages & Disadvantages

Advantages• It has simple flowsheet, low

capital investment, and low risk. If components to be separated have a high relative volatility difference and are thermally stable, distillation is hard to beat.

Disadvantages• Distillation has a low energy

efficiency and requires thermal stability of compounds at their boiling points. It may not be attractive when azeotropes are involved or when it is necessary to separate high boiling components, present in small concentrations, from large volumes of a carrier, such as water.

Types of Distillation

• Continous Distillation• Batch Distillation• Semi-Batch Distillation

Continous Distillation

• The mixture which is to be seperated is fed to column at one or more points.

• Liquid mixture runs down the column while vapor goes up.

• Vapor is produced by partial vaporisation of the mixture which is heated in reboiler.

• Then vapor is partially condensed to earn back the less volatile compounds to the column to seperate as bottom product. (reflux)

Batch Distillation

• The oldest operation used for seperation of liquid mixtures.

• Feed is fed from bottom,where includes reboiler, to be processed.

• Numbers of accumulator tanks are connected to collect the main and the intermediate distillate fractions.

Semi-batch Distillation

• Semi-batch distillation is very similar to batch distillation.

• Feed is introduced to column in a continous or semi-continous mode.

• It is suitable for extractive and reactive distillations.

Comparsion of Distillation Types

• For batch distillation, it is enough to use only one column to seperate multicomponent liquid mixture.

• One sequence of operation is enough to seperate all the components in a mixture.

• For continous distillation, to seperate multicomponent liquid mixtures, more than one columns are necessary to be used.

• One column is dedicated to seperate a specific mixture and specific operation.

Equipment Designs

• Plate Columns (Tray Columns)• Packed Beds

Plate Columns (Tray Columns)

• It is the most widely used kind of distillation column.

• Trays are shaped to maximize the liquid-vapor contact and increase the mass transfer area.

• Tray types include sieve, valve and bubble cap.

Advantages & Disadvantages

Advantages• Least expensive colum for

diameters greater than 0.6m• The liquid-vapor contact in the

cross-flow of plate columns is more effective than countercurrent-flow in packed columns.

• Cooling coils can be easily added to the plate column

• Can handle high liquid flow rates.

Disadvantages• Higher pressure drops than

packed columns• Foaming can occur because the

liquid is agitated by the vapor flowing up through it.

Packed Beds

• Packings can be provided either as dumped or stacked.

• Dumped packing consistutes of bulk inert materials.

• Stacked packing is includes meshwork which has the same diameter with the column.

• Important criterias for packings are efficent contact (liquid-vapor), resistence to flow, flow capacity, resistance of packing against corrosion.

Advantages & Disadvantages

• When the diameter is less than 0.6m it is less expensive than the plate column.

• Packing is able to handle corrosive materials.

• Lower pressure drop than in plate columns.

• Good for thermally sensitive liquids.

• Can break during installation or due to thermal expansion.

• Not cost efficient for high liquid flow rates.

• Contact efficiencies are decreased when the liquid flow rate is too low.

Making of Alcohol

• Alcohols, generally can be created by reduction of aldehydes or twice reduction of ketones.

• Ethanol (C2H5OH) can produced by fermantation of molases.

• Fermantation is done in a tank and it is cleaned and sterilized before the fermantation begins.

Molases have strong concentration of sugar which doesn't provide the adequate conditions for fermantation. Consequently it must be dilluted to concentration of %17 sugar.

Optimum enviromental pH range is between 4.0 and 5.0; and optimum temperature is 76°F(25°C).

Fermantated molases is called beer and it contains %6.5 to %11 alcohol by volume.

Distillation of Alcohol

• Under 1 athmosphere pressure boiling points of water and alcohol are 100°C and 78.3°C.

• Water and ethyl alcohol mixture forms an azeotrope in athmospheric pressure at a mole fraction of %89.4 of ethyl alcohol which means that by simple distillation of ethyl alcohol, it cannot be purified more than %95.6 w.

• As distillation equipments, bubble cap trays and tray columns are mostly used in alcohol distillation.(Figure on left)

Pot Distillation Process (Batch Distillation)

• Entire batch of beer is heated in a large container and alcohol/water vapors are chanelled into a distillation column.

• After all the boiling and reflux operations, when almost all alcohol is boiled, process is stopped and stillage is removed.

The basic advantage of pot distillation is its simplicity. It has simple equipment system. Fermantation and boiling for distillation can take place at the same pot, which makes it more practical

The disadvantage of the pot distillation is low distillation efficiency. It requires about three times more energy comparing to continous distillation.

Continous-Feed Distillation Process

• Typically it is also known as continous distillation.

• Alcohol/liquid mixture is fed to column and it flows.

• Flow rate is decreased by trays.

• Mixture boils up in the reboiler and goes up of the column to condenser as it contacts with the condensed liquid.

• The vapor with high alcohol percent leaves the condenser to be collected in accumulator.

The advantage of the continous feed distillation process is it's high energy efficiency comparing to the pot distillation process. Eventually amount of energy required for per liter of alcohol is less than in pot distillation. On the other hand it can operate for long hours (almost 8000 hours per annum)

The disadvantage of continous feed distillation is it needs a little more complicated equipment system comparing to the batch distillation.

Vacuum Distillation

• Low temperature allows us to achieve higher alcohol concentrations.

• At a pressure below 0.1 athmosphere azeotrope disappears and enables to distillate to almost 100 percent alcohol.

Because of the high operation and installation costs, low energy efficiency, vacuum distillation appears to be uneconomical in the commercial applications.

Azeotropic Distillation

• This type of distillation is used for processes that produce almost 100 percent alcohol with help of an organic solvent and two additional distillations.

• A solvent (pentane, gasoline etc.) is added to distillation product comming out of the usual distillation column.

• Mixture is fed to another distillation column which seperates it into a top product and a bottom product.

• Distillate of this column is fed to a third column which distills out the solvent leaving the mixture of alcohol-water.

• Solvent is recycled and never gets out. • System is hard to design and it is more complicated

comparing to ordinary distillation system.

HOW IS IT HOW IS IT USED ?USED ?

APPLICATIONS

• Alcohols can be used as a beverage (ethanol only), as fuel and for many scientific, medical, and industrial utilities. • Ethanol in the form of alcoholic

beverages has been consumed by humans since pre-historic times. • A 50% v/v solution of ethylene glycol in

water is commonly used as an antifreeze.

• Some alcohols, mainly ethanol and methanol, can be used as an alcohol fuel.

• Fuel performance can be increased in forced induction internal combustion engines by injecting alcohol into the air intake after the turbocharger or supercharger has pressurized the air.

• This cools the pressurized air, providing a denser air charge, which allows for more fuel, and therefore more power.

• Alcohols have applications in industry and science as reagents or solvents.

• Because of its low toxicity and ability to dissolve non-polar substances, ethanol can be used as a solvent in medical drugs, perfumes, and vegetable essences such as vanilla.

• In organic synthesis, alcohols serve as versatile intermediates.

• Ethanol can be used as an antiseptic to disinfect the skin before injections are given, often along with iodine.

• Ethanol-based soaps are becoming common in restaurants and are convenient because they do not require drying due to the volatility of the compound.

• Alcohol is also used as a preservative for specimens.

• Alcohol gels have become common as hand sanitizers.

ALCOHOL FUELS

• Although fossil fuels have become the dominant energy resource for the modern world, alcohol has been used as a fuel throughout history.

• The first four aliphatic alcohols (methanol, ethanol, propanol, and butanol) are of interest as fuels because they can be synthesized biologically, and they have characteristics which allow them to be used in current engines.

Contd..

• One advantage shared by all four alcohols is octane rating. Biobutanol has the advantage that its energy density is closer to gasoline than the other alcohols (while still retaining over 25% higher octane rating) - however, these advantages are outweighed by disadvantages (compared to ethanol and methanol) concerning production, for instance. Generally speaking, the chemical formula for alcohol fuel is CnH2n+1OH. The larger n is, the higher the energy density.

• Alcohol fuels are usually of biological rather than petroleum sources. When obtained from biological sources, they are known as bio alcohols (e.g. bio ethanol). There is no chemical difference between biologically produced alcohols and those obtained from other sources. However, ethanol that is derived from petroleum should not be considered safe for consumption as this alcohol contains about 5% methanol and may cause blindness or death. This mixture may also not be purified by simple distillation, as it forms an azeotropic (same boiling point)mixture.

METHANOL AND ETHANOL

• Methanol and ethanol can both be derived from fossil fuels or from biomass. Ethanol is produced through fermentation of sugars and methanol from synthesis gas.

• As a fuel methanol and ethanol both have advantages and disadvantages over fuels such as petrol and diesel.

• In spark ignition engines both alcohols can run at a much higher EGR rates and with higher compression ratios.

• Both alcohols have a high octane rating, with ethanol at 109 RON, 90 MON, (which equates to 99.5 AKI) and methanol at 109 RON, 89 MON (which equates to 99 AKI) .

• Ordinary European petrol is typically 95 RON, 85 MON, equal to 90 AKI. Note that AKI refers to 'Anti-Knock Index' which averages the RON and MON ratings (RON+MON)/2, and is used on U.S. gas station pumps. As a compression ignition engine fuel, both alcohols create very little particulates, but their low cetane number means that an ignition improver like glycol must be mixed into the fuel with approx. 5%.

• With SI engines alcohols have the potential to reduce NOx, CO, HC and particulates. A test with E85 fueled Chevrolet Luminas showed that NMHC went down by 20-22%, NOx by 25-32% and CO by 12-24% compared to reformulated gasoline[. Toxic emissions of benzene and 1,3 Butadiene also decreased while aldehyde emissions increased (acetaldehyde in particular).

• Tailpipe emissions of CO2 also decrease due to the lower carbon-to-hydrogen ratio of these alcohols, and the improved engine efficiency

• Methanol and ethanol contain soluble and insoluble contaminants .

• Halide ions, which are soluble contaminants, such as chloride ions, have a large effect on the corrosivity of alcohol fuels. Halide ions increase corrosion in two ways: they chemically attack passivating oxide films on several metals causing pitting corrosion, and they increase the conductivity of the fuel.

• Increased electrical conductivity promotes electrical, galvanic and ordinary corrosion in the fuel system. Soluble contaminants such as aluminum hydroxide, itself a product of corrosion by halide ions, clogs the fuel system over time. To prevent corrosion the fuel system must be made of suitable materials, electrical wires must be properly insulated and the fuel level sensor must be of pulse and hold type (or similar). In addition, high quality alcohol should have a low concentration of contaminants and have a suitable corrosion inhibitor added.

• One liter of ethanol contain 21.1 MJ, a liter of methanol 15.8 MJ and a liter of gasoline approximately 32.6 MJ. In other words, for the same energy content as one liter or one gallon of gasoline, one needs 1.6 liters/gallons of ethanol and 2.1 liters/gallons of methanol. Although actual fuel consumption doesn't increase as much as energy content numbers indicate.

• Ethanol is already being used extensively as a fuel additive, and the use of ethanol fuel alone or as part of a mix with gasoline is increasing. Compared to methanol its primary advantage is that the fuel is non-toxic, although the fuel will produce some toxic exhaust emissions.

• Methanol combustion is: 2CH3OH + 3O2 → 2CO2 + 4H2O + heat

• Ethanol combustion is: C2H5OH + 3O2 → 2CO2 + 3H2O + heat

Propanol and Butanol

• Propanol and butanol are considerably less toxic and less volatile than methanol. In particular, butanol has a high flashpoint of 35 °C, which is a benefit for fire safety, but may be a difficulty for starting engines in cold weather. The concept of flash point is however not directly applicable to engines as the compression of the air in the cylinder means that the temperature is several hundred degrees Celsius before ignition takes place.

• The fermentation processes to produce propanol and butanol from cellulose are fairly tricky to execute, and the Weizmann organism (Clostridium acetobutylicum) currently used to perform these conversions produces an extremely unpleasant smell, and this must be taken into consideration when designing and locating a fermentation plant.

• This organism also dies when the butanol content of whatever it is fermenting rises to 7%.

• For comparison, yeast dies when the ethanol content of its feedstock hits 14%.

• Specialized strains can tolerate even greater ethanol concentrations - so-called turbo yeast can withstand up to 16% ethanol

• Butanol combustion is: C4H9OH + 6O2 → 4CO2 + 5H2O + heat

• The 3-carbon alcohol, propanol (C3H7OH), is not used as a direct fuel source for petrol engines that often (unlike ethanol, methanol and butanol), with most being directed into use as a solvent.

• However, it is used as a source of hydrogen in some types of fuel cell; it can generate a higher voltage than methanol, which is the fuel of choice for most alcohol-based fuel cells.

• However, since propanol is harder to produce than methanol (biologically OR from oil), methanol fuel cells are still used a lot more often than those that utilise propanol.

FATTY ALCOHOL• Fatty alcohols are aliphatic alcohols derived

from natural fats and oils, originating in plants, but also synthesized in animals and algae. Their significance in nutrition and health has historically been overlooked, and is only now being realized, as they are closely related to fatty acids, including the well-documented omega 3 fatty acids.

• The other counterparts are fatty aldehydes. Fatty alcohols usually have even number of carbon atoms.

• Production from fatty acids yields normal-chain alcohols—the alcohol group (-OH) attaches to the terminal carbon.

• Other processing can yield iso-alcohols—where the alcohol attaches to a carbon in the interior of the carbon chain.

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