Sodium hydroxide, caustic soda production using Mercury Cell, Diaphragm cell, Membrane Cell methods

Sodium hydroxide (NaOH) an inorganic compound with following synonyms

• Caustic soda
• Lye
• Sodium hydrate

NaOH widely used inorganic industrial chemical. NaOH is having certain properties like

Sodium hydroxide's chemical formula is NaOH

NaOH molecular weight of 39.997 g/mol

Sodium hydroxide is contain ph of ~12-14

Sodium hydroxide characteristics can be mentioned as

• Raw material for various industrial products
• Co-product in chlorine synthesis
• Strong base
• Highly corrosive
• Auxiliary chemical
• Odorless material

Caustic soda is available in two forms - Caustic soda lye and Caustic soda solid. Solid form of caustic soda can be in the form of

Caustic soda flakes

or

Caustic soda granules

Pure form of sodium hydroxide also available as

• Sodium hydroxide pellets
• Sodium hydroxide flakes
• Sodium hydroxide granule
• Sodium hydroxide solution

Caustic soda has wide variety of industrial sectors like

In pulp and paper processing industry caustic soda used at the stages like bleaching process, in de-inking of waste paper, and in water treatment.

Next major industry like textile industry caustic soda is used to process cotton and synthetic fibers

Caustic soda is utilized more in the soap and detergent industry.

Other caustic soda uses include

• In oil and gas industry – to remove pungent smells
• In household cleaning products
• In beverage bottles
• In home soap making

Worldwide there is high demand for caustic soda and increase in caustic soda prices, applications in daily lives this article gives the different modern caustic soda manufacturing processes.

Sodium Hydroxide solutions are produced by three different technologies

• Mercury cells
• Membrane cells
• Diaphragm cells

Each of above processes utilizes sodium chloride (NaCl) salt as the primary raw material. Electrolytic splitting of salt results in products like chlorine and sodium ion (Na+). In turn Na+ will react with water in the mercury cell to form Sodium hydroxide and Hydrogen as by product.

Mercury Cell

Fig. [1] Mercury cell

In the Mercury Cell Process saturated brine voyages down a steel trough roughly 15 meters in length and one meter wide between a streaming film of mercury (the cathode) and titanium plates (the anodes). Direct current is connected between the anode and cathode. Chlorine freed at the anodes gathers above the brine and is begun as a hot, wet and corrosive gas.

Sodium ions are released at the surface of the streaming mercury cathode, forming an amalgam of low concentration with the mercury, which streams out of the cell without reacting with the water or chlorine.

The mercury cell thus has two products

(i) Hot, wet chlorine

(ii) Sodium amalgam

The soda cell or decomposer is a cylindrical steel trough loaded with graphite balls or graphite electrodes. The sodium amalgam is passed, along with pure water, into the decomposer, where it reacts to transform Sodium hydroxide as a controlled 50 per cent aqueous solution and hydrogen gas, liberating fee mercury, which is reused again to the electrolytic cell. The graphite provides a surface that expedites this reaction.

The following two types of reactions called brine cell and the soda cell respectively.

Brine Cell

                       2Cl = Cl₂ + e

                       Na + e = Na

                       Na + Hg = Na/Hg

Soda Cell

                          2 Na/Hg + 2 H₂O = 2NaOH + H₂ + 2Hg

Diaphragm Cell

Fig. [2] Diaphragm cell

This method produces 71 per cent of Sodium hydroxide. Diaphragm Cell process utilizes asbestos or alternate substitutes to asbestos, to separate the co-products Sodium Hydroxide (Caustic Soda) and Chlorine. The production of 50 per cent NaOH occurs primarily outside of the electrolytic cell.

The diaphragm cell produces a very weak 'cell liquor,' that contains 12-14 per cent, by weight, NaOH and the constant volume of NaCl salt. The cell liquor is subsequently evaporated in a three or four 'effect' evaporation method to a final nominal concentration of 50 per cent NaOH by weight. The surplus salt is precipitated and filtered through the evaporation method for subsequent reuse/recycle. This method produces the lowest quality electrochemical NaOH solutions.

The quality considerations with respect to the diaphragm cell produced Caustic solutions include comparatively high salt, chlorates, carbonates, and sulfates. Salt, as NaCl, concentrations are typically 1.0 per cent, with maximums ranging from 1.1 to 1.3 weight per cent, counting on producer.

The diaphragm cell created Caustic Soda (NaOH) is usually referred as Diaphragm Cell Grade. It is conjointly known as Commercial Grade, Technical Grade, and occasionally Technical Diaphragm or other similar combinations.

An additional 'grade' of Caustic Soda (NaOH) produced by the diaphragm cell method is the sublimate grade. The production of sublimate Grade involves the further evaporation of the 50 per cent Diaphragm Grade NaOH solution to cut back the salt concentration. The higher concentration solution is then re-diluted to the 50% concentration that is commercially available as sublimate grade Caustic Soda.

Common uses include process and sewer water neutralization, textiles production, soaps and detergents and aluminum production. These uses and applications typically can confer with the Caustic Soda as any of the varied grades.

Membrane Cell

Fig. [3] Membrane cell

This method produces approximately 13 per cent of Sodium Hydroxide. The membrane cell method utilizes a selective membrane that separates the Chlorine and Sodium ions. The membrane permits the Sodium ion to migrate across the membrane whereas keeping the Chlorine gas and salt (brine) solution in a compartment on the opposite facet of the membrane.

The Sodium ion is reacted with refined water as within the mercury cell to provide the Caustic Soda (NaOH). Evaporation is employed, as within the diaphragm method, to lift the concentration up to the nominal 50 weight per cent solution. The salt concentrations are not targeted as considerably during this evaporation method attributable to the selective diffusion nature of the membranes as well as the reduced quantity of evaporation needed during this method opposed to the diaphragm evaporation.

The Caustic Soda produced by the membrane cell process is most typically brought up as Membrane Grade. It conjointly contains a growing acceptance as a Rayon Grade product in all areas outside of rayon fiber production.

Reference

[1] http://www.essentialchemicalindustry.org/chemicals/sodium-hydroxide.html

[2] http://www.oocities.org/tiger_dil3000/

Image Reference

Fig. [1] Mercury cell © From http://www.essentialchemicalindustry.org/chemicals/chlorine.html#membrane_cell

Fig. [2] Diaphragm cell © From http://www.essentialchemicalindustry.org/chemicals/chlorine.html#membrane_cell

Fig. [3] Membrane cell © From http://www.essentialchemicalindustry.org/chemicals/chlorine.html#membrane_cell

Chemsitry Of Enzymes, Polymers origin, structures, production, industrial applications

Enzymes

Original name of enzymes is ferments. Enzymes are biomolecules, biocatalysts, complex proteins that drives thousands of metabolic processes in living things. Without enzymes there is no respiration process, digestion processes in animals and no photosynthesis process in plants. Overall enzymes can able to catalyze 4000 biochemical reactions. Enzymes are biocatalysts. Enzymes without being consumed in the process can speed up chemical processes or slow down the chemical processes. After the reaction is complete, the enzyme is released from the chemical process which can start another reaction.

They are present in all living cells, where they perform a vital function by controlling the metabolic processes. Moreover, enzymes take part in the breakdown of food materials into simpler compounds. Enzymes like pepsin, trypsin and peptidases break down proteins into amino acids, lipases split fats into glycerol and fatty acids, and amylases break down starch into simple sugars.

Enzymes production

Enzymes are generally extracted from various sources like plants, animals, bacteria, fungi, and animal organs. The enzymes of animal and plant origin are produced through the disruption of tissues, organs, leaves and fruits. Then enzymes will be extracted with water or organic solvent. In same way microbial enzymes are attained through the process of fermentation.

Examples for enzymes

Chimosin

Pepsin

Trypsin

Pancreatin

Ficin

Papain

Bromelain

Pactinases

Glucoamylase

Amylase

Protease

Alpha-amylase

Thousands of different enzymes are needed to keep the human body functioning normally, each usually acting on only one kind of substrate, and catalyzing only one kind of reaction. Enzymes are classified according to the type of reaction they catalyze and the type of substrates on which they act.

Most metabolic processes involve a series of many different chemical changes. In digestion, for example, separate chemical reactions take place in the mouth, stomach, and intestine. Certain enzymes break down the protein, carbohydrate, and fat molecules of food into smaller molecules. Other enzymes assist in passing these smaller molecules into the bloodstream.

History & Discovery of enzymes

In 1833 Payen and Persoz isolated enzyme complex from malt

In 1874 Christian Hansen extracted dried calves' stomachs with saline solution

In 1876 William Kuhne coined the term ‘enzyme’

In 1897 Eduard Buchner studied about zymase action

In 1926 James B. Sumner explained function of urease

In 1930 Northrop and Stanley worked on pepsin enzyme

Structure of enzymes

Enzymes are in general globular proteins and range from just 62 amino acid residues in size and all these amino acids linked together. The amino acids within each kind of enzyme have a characteristic arrangement. The bonds between the different amino acids in the chains are weak and may be broken by such conditions as high temperatures or high levels of acids. When the bonds are broken, the enzymes become nonfunctional and disease sometimes occurs.

Enzyme Commission number/system

For the classification of enzymes one particular method is following by the people i.e., Enzyme Commission System.

The Enzyme Commission number (EC number) is a numerical classification scheme for enzymes, based on the chemical reactions they catalyze.

EC 1 - Oxidoreductases, catalyzes both oxidation reactions and reduction reactions

EC 2 - Transferases, catalyzes transferring of groups

EC 3 - Hydrolases, catalyzes hydrolytic cleavage of different bonds

EC 4 - Lyases, catalyzes cleavage of bonds

EC 5 - Isomerases - catalyzes geometric or structural changes within molecule

EC 6 - Ligases - catalyzing the joining of two molecules

Applications of enzymes

Enzymes for textile industry, enzymes used for textile industry for the purpose of desizing, bio-polishing, denim finishing, bleach clean-up, bio-scouring and de-wooling

Enzymes for leather industry - enzymes used for leather industry for the purpose of bating, un-haring, degreasing and soaking in the beam-house processes

Enzymes for food industry - enzymes used for food industry for the purpose of food baking and brewing of alcohols

Enzymes for detergent industry - enzymes used for detergent industry for the purpose of removing protein stains, fatty stains

Enzymes for biofuel industry

Enzymes for rubber industry

Enzymes for photographic industry

Polymers

Polymers are high molar mass containing macromolecules and are composed of a large number of repeating units or different types of units. Homopolymers are the polymers contain single type of repeat units. Where as copolymers are the polymers contains mixture of repeat units

There are two types of polymers.

• Natural polymers
• Synthetic polymers

• Proteins - it is polymer of amino acids
• Nucleic acids - it is polymer of nucleotides
• Starches - it is polymer of glucose
• Latex is the naturally occurring polymers

• Ethylene
• Propylene
• Polyethylene
• Polyethylene terephthalate [PETE]
• Polyvinyl chloride [PVC]
• Polypropylene [PP]
• Polystyrene [PS]
• Poly tetrafluoro ethylene
• Polyurethane
• Polyamide
• Polyacrylamides are synthetic polymers

Polymers are the major constitute the basis for diamond, quartz, and feldspar and concrete, glass, paper, plastics, and rubbers.

Polymers are formed by chemical reactions in which a large number of molecules called monomers are joined sequentially, forming a chain. In others, two or three different monomers may be joined to form a long chain.

Polymers are classified by the characteristics of the reactions by which they are formed.

Addition polymers

If all atoms in the monomers are incorporated into the polymer, the polymer is called an addition polymer. Most addition polymers are made from monomers containing a double bond between carbon atoms. Such monomers are called olefins.

Condensation polymer

If some of the atoms of the monomers are released into small molecules, such as water, the polymer is called a condensation polymer. Condensation polymers are made from monomers that have two different groups of atoms which can join together to form.

Chemical properties of polymers

The attractive forces between polymer chains play a major role in polymer's properties. Polymers side groups determine what types of intermolecular forces will exist. If greater the strength of the intermolecular forces, the greater will be the tensile strength and melting point of the polymer.

Different types of bonds exists between polymers are

• Hydrogen bonds
• Dipole-dipole bonds
• Vander waal’s forces

Chemistry behind plastics, rubber, resins, its history, evolution, production, industrial applications

Plastics 

Plastics are made up of polymers, but some polymers like biopolymers are not plastics. Plastic materials are being used in day to day life like computers, pen, mobile phones, compact discs, pendrive, and toothbrushes etc.

Plastic is defined as any synthetic or semi-synthetic organic material that can be shaped or molded into any form. Chemical composition of plastics includes chains of carbon, oxygen, sulfur or nitrogen.

History of plastics

In 1284 naturally made plastic compounds from horn and tortoiseshell were identified

1820 plastic timeline

In 1823, Scottish chemist Charles Macintosh discovered rubber.

In 1845, Henry Bewley produced natural rubber from plant gutta percha

In 1850, first submarine telegraph cable in gutta percha laid between Dover and Calais

In 1862, Londoner Alexander Parkes unveiled first man-made Parkesine plastic compound

In 1869, John W. Hyatt invented Celluloid [colorless flammable material]

In 1872, Hyatt brothers patented first plastics injection moulding machine

In 1880 cellulose nitrate replacing horn as the preferred material for combs

In 1885, George Eastman Kodak patents machine for producing continuous photographic film based on cellulose nitrate.

1900 plastic timeline

In 1908, Jacques E. Brandenberger invented Cellophane [transparent cellulose material]

In 1909, Casein plastics, derived from milk, developed by Erinoid.

In 1909, H. Baekeland created first fully synthetic plastic product called Bakelite

In 1916, Rolls Royce begins to use phenol formaldehyde in its car interiors.

In 1920, Polyvinyl chloride or PVC was created.

In 1925, Plastic term was coined.

In 1930, in this year scotch tape was invented by 3M company

In 1933, Fawcett and Gibson discovered polyethylene material

In 1938, first toothbrush with nylons tufts manufactured.

In 1939, in this year nylon created.

In 1942, Dr Harry Coover discovered Super Glue (methyl cyanoacrylate).

In 1948, Acrylonitrile-butadiene-styrene (ABS) produced.

In 1949, Tupperware material made from low density polyethylene.

In 1949, DuPont invented Lycra product which is based on polyurethane.

In 1953, Lexan plastic material was invented by Daniel Fox.

In 1959 Barbie Doll unveiled at American International Toy Fair.

In 1965 DuPont released products with the trade name of Kevlar.

In 1973, Polyethylene terephthalate beverage bottles introduced.

In 1988, triangular recycling symbols relating to plastics were introduced.

2000 to 2022 plastic timeline

In 2003 Recovinyl [it is a European PVC recycling system] was established

2005 in this year NASA explores the advantages of a polyethylene based material RFX1 [RFX1 used for spaceship construction]

In 2011, vinylplus - sustainability programme established

In 2012 PVC fabric used in the construction of London Olympic venues

2020 PVC products production will reaches to 800,000 tones per year

2022 in this year the FIFA world cup qatar showcase stadium is planning to use super reflective, triangulated PVC fabric to create a zero carbon.

Manufacturing process of plastics

Preparation of raw materials

Preparation of monomer

Polymerization process

Conversion of polymer resins to plastic products

In the process of converting polymer resins to plastic product following steps are involved

• Extrusion
• Injection molding
• Blow molding
• Rotational molding

Applications of plastics

Plastics are widely used in following industrial sectors for various purposes

Textile industry – polyester used for making of some cloths

Packaging industry - Polyethylene terephthalate chemical used in carbonated drinks bottles, peanut butter jars, plastic film, microwavable packaging

Plastic also used in

• Supermarket bags
• Window frames, outdoor furniture
• Toothbrush bristles
• Traffic lights
• Cushioning foams
• Thermal insulation foams
• Surface coatings

Rubber

Rubber is considered as elastic substance, which is obtained from the exudations of certain tropical plants (natural rubber) or derived from petroleum and natural gas. Rubber also termed as elastomer, a type of polymer. In 1770 Joseph Priestley coined the term rubber.

Rubber is divided into two groups based on its origin

Natural rubber – used in racing car tires, bus tires, truck tires

Synthetic rubber – examples butadiene rubber, styrene butadiene rubber, neoprene

Physical & Chemical properties of rubber

Did your ever wonder how rubber will stretch?

Before you want to know the reason one should know the physical and chemicals properties of rubber

Physical properties

In relaxed state, rubber is in the form of long, coiled-up chains. By stretching of rubber the all chains will come very close as result, kinetic energy exerted in the form of heat. In chain elongation process entropy and temperatures required during this process are increases. When chain in relaxed state both entropy and temperatures decreases.

Relaxation of a stretched rubber band is thus driven by a decrease in entropy and temperature, and the force experienced is a result of the cooling of the material being converted to potential energy. The material undergoes adiabatic cooling during contraction.

Vulcanization of rubber creates disulfide bonds between chains. The result is that the chains tighten more quickly for a given strain, thereby increasing the elastic force constant and making rubber harder and less extensible.

Chemical properties

Like plastic, rubber is also a type of polymer, made of subunits called monomers. In rubber, the monomer is isoprene. As the latex dries, the isoprene molecules mass together and one isoprene molecule attacks a carbon-carbon double bond of a neighboring molecule. One of the double bonds breaks and the electrons repositioned to form a bond between the two isoprene molecules.

The process continues until long strands of many isoprene molecules linked like a chain. This long chain of strands is called as polyisoprene polymer. As the drying continues, the polyisoprene strands stick together by forming electrostatic bonds. The attraction between these strands holds the rubber fibers together and allows them to stretch and to recover.

Synthetic rubber production

Emulsion polymerization is the widely used method to produce synthetic rubber.

Emulsion polymerization

Emulsion polymerization is a type of radical polymerization process that usually starts with an emulsion incorporating water, monomer, and surfactant. The most common type of emulsion polymerization is an oil-in-water emulsion, in which droplets of monomer (the oil) are emulsified (with surfactants) in a continuous phase of water.

In emulsion polymerization, the monomers are emulsified in water with a suitable soap and a water-soluble free-radical catalyst is added to induce polymerization. After polymerization has reached the desired level, the reaction is stopped by adding a radical inhibitor. About 10 per cent of synthetic elastomer produced through emulsion technique. The rest is coagulated with acidified brine, washed, dried, and pressed into 35-kg bales.

Resins

Resin is a natural or synthetic hydrocarbon secreted many plants, particularly coniferous trees. Its applications ranging from art to polymer production and many consumers interact with products that contain it on a daily basis.

The resin produced by most plants is a viscous liquid, composed mainly of volatile fluid terpenes, with lesser components of dissolved non-volatile solids which make resin thick and sticky. The most common terpenes in resin are the bicyclic terpenes alpha-pinene,beta-pinene, delta-3 carene and sabinene, the monocyclic terpenes limonene and terpinolene, and smaller amounts of the tricyclic sesquiterpenes, longifolene, caryophyllene and delta-cadinene. Some resins also contain a high proportion of resin acids.

Types of resins

Oleoresins are naturally occurring mixtures of oil and a resin. Oleoresins contain benzoic acid or cinnamic acid.

Formaldehyde resin is a synthetic resin product made with formaldehyde. This product is used in a wide variety of settings and industries, and is one of the oldest synthetic resins around.Plastic resins are made by heating hydrocarbons. Plastic resins are used to make many different kinds of products.

Epoxy resins are created by transforming liquid polyethers into infusible solids through a special curing process. Epoxy resins fiber optics, optoelectronics, and dentistry.

Silicone resins are a type of silicone material which is formed by branched, cage-like oligosiloxanes with the general formula of R_nSiX_mO_y.

Applications of resins

Resins is used in following sectors

• Varnishes
• Adhesives
• Therapeutic purposes
• Musical instruments
• In making sculptures
• Motors
• Generators
• Transformers
• Switchgear
• Bushings
• Insulators
• Integrated circuits
• Transistors
• Hybrid circuits
• Printed circuit boards