Industrial Chemistry BCH5T12

Syllabus topics (RTMNU)

• Manufacturing processes of Sulphuric Acid, Hydrochloric acid, Nitric acid, Phosphoric acid
• Fertilizer Industries: Phosphorus Fertilizers – phosphorus, phosphoric acid, ammonium phosphate, superphosphate
• Nitrogen Fertilizers: Urea, ammonium nitrate and ammonium sulphate
• Cement: manufacturing, composition and setting, chemical analysis of Portland cement

Sulphuric acid — Contact process

1. Burning sulphur (or roasting pyrites): S + O₂ → SO₂.
2. Purification of SO₂ + air (dust chamber, scrubbing, drying with conc. H₂SO₄, arsenic removal with Fe(OH)₃) — impurities poison the catalyst.
3. Catalytic oxidation in the converter: 2SO₂ + O₂ ⇌ 2SO₃, ΔH = −196 kJ (exothermic); catalyst V₂O₅, about 400–450 °C, slight excess air, about 1–2 atm. (Le Chatelier: low temperature favours yield but slows rate — so an optimum temperature is used.)
4. Absorption: SO₃ is absorbed in 98% H₂SO₄ to form oleum (H₂S₂O₇), which is diluted with water: H₂S₂O₇ + H₂O → 2H₂SO₄. (SO₃ is not absorbed directly in water because it forms an acid mist.)

Uses: fertilisers (superphosphate, ammonium sulphate), detergents, dyes, batteries, petroleum refining, "king of chemicals".

Hydrochloric acid

(1) Synthetic process: H₂ and Cl₂ (by-products of chlor-alkali electrolysis of brine) are burnt in a silica/graphite burner: H₂ + Cl₂ → 2HCl; the gas is cooled and absorbed in water (falling-film absorbers). (2) Salt-cake process: NaCl + H₂SO₄ → NaHSO₄ + HCl (and at higher temperature Na₂SO₄). (3) By-product of chlorination of organic compounds. Uses: pickling steel, ore processing, PVC, food (glucose), dyes.

Nitric acid — Ostwald process

1. Catalytic oxidation of ammonia: 4NH₃ + 5O₂ → 4NO + 6H₂O, over Pt–Rh gauze at about 800–900 °C (very fast contact).
2. 2NO + O₂ → 2NO₂ (on cooling).
3. Absorption in water: 3NO₂ + H₂O → 2HNO₃ + NO; NO is recycled. Gives about 60–68% acid; concentrated further by distillation with conc. H₂SO₄.

Uses: fertilisers (ammonium nitrate), explosives (TNT, nitroglycerin), dyes, nylon intermediates.

Phosphoric acid

• Wet process (for fertilisers): rock phosphate + H₂SO₄: Ca₃(PO₄)₂ + 3H₂SO₄ + 6H₂O → 2H₃PO₄ + 3CaSO₄·2H₂O (gypsum filtered off).
• Thermal (furnace) process (pure acid): white phosphorus is burnt to P₄O₁₀, which is hydrated: P₄O₁₀ + 6H₂O → 4H₃PO₄.

Phosphorus fertilisers

• Phosphorus: made in an electric furnace from rock phosphate, sand and coke at about 1500 °C: 2Ca₃(PO₄)₂ + 6SiO₂ + 10C → 6CaSiO₃ + P₄ + 10CO; used to make pure phosphoric acid.
• Phosphoric acid — as above; raw material for all phosphate fertilisers.
• Ammonium phosphates: NH₃ + H₃PO₄ → NH₄H₂PO₄ (MAP); 2NH₃ + H₃PO₄ → (NH₄)₂HPO₄ (DAP, 18-46-0) — supplies both N and P.
• Single superphosphate: Ca₃(PO₄)₂ + 2H₂SO₄ + 4H₂O → Ca(H₂PO₄)₂ + 2CaSO₄·2H₂O (about 16% P₂O₅). Triple superphosphate: Ca₃(PO₄)₂ + 4H₃PO₄ → 3Ca(H₂PO₄)₂ (about 44–48% P₂O₅, no gypsum).

Nitrogen fertilisers

• Urea (46% N): NH₃ and CO₂ under about 140–200 atm and 180–200 °C: 2NH₃ + CO₂ → NH₂COONH₄ (ammonium carbamate) → NH₂CONH₂ + H₂O. Concentrated and prilled (granulated). Highest N content of solid fertilisers.
• Ammonium nitrate (about 34–35% N): NH₃ + HNO₃ → NH₄NO₃; hygroscopic and explosive, so often mixed with CaCO₃ as CAN (calcium ammonium nitrate).
• Ammonium sulphate (about 21% N): 2NH₃ + H₂SO₄ → (NH₄)₂SO₄; also by the gypsum process: CaSO₄ + 2NH₃ + CO₂ + H₂O → (NH₄)₂SO₄ + CaCO₃. Makes soil acidic on long use.

Cement — manufacture, composition and setting

Portland cement is a fine grey powder of calcium silicates and aluminates that sets hard with water.

Raw materials: calcareous (limestone, CaCO₃) and argillaceous (clay — SiO₂, Al₂O₃, Fe₂O₃), plus gypsum.

Manufacture (dry/wet process): crushing and mixing raw materials (as powder or slurry) → burning in a rotary kiln: drying zone (≈ 400 °C), calcination zone (≈ 1000 °C, CaCO₃ → CaO + CO₂), clinkering zone (≈ 1400–1500 °C, CaO combines with silica, alumina, iron oxide) → clinker → cooled and ground with 2–3% gypsum.

Typical oxide composition: CaO 60–67%, SiO₂ 17–25%, Al₂O₃ 3–8%, Fe₂O₃ 0.5–6%, MgO 0.1–4%, SO₃ 1–3%.

Setting and hardening: with water the compounds hydrate: C₃A hydrates fastest (initial set; gypsum forms calcium sulphoaluminate and delays it), C₃S and C₂S form calcium silicate hydrate (C–S–H) gel and Ca(OH)₂; the gel binds particles and hardens over weeks.

Chemical analysis of Portland cement (outline): loss on ignition (heat at 1000 °C); insoluble residue; silica (evaporate with HCl, ignite, weigh SiO₂); R₂O₃ (Fe₂O₃ + Al₂O₃) precipitated with NH₄OH and weighed; Fe₂O₃ by titration (K₂Cr₂O₇); CaO by oxalate precipitation and KMnO₄ titration or EDTA; MgO by EDTA or as Mg₂P₂O₇; SO₃ as BaSO₄.

Likely exam questions

1. (Long, 8 marks) Describe the manufacture of sulphuric acid by the contact process with the conditions for maximum yield.
2. (Long, 8 marks) Explain the manufacture of Portland cement. Give its composition and explain the setting of cement.
3. (Short, 4 marks) How is urea manufactured? Give its importance as a fertiliser.
4. (Short, 4 marks) Write the Ostwald process for nitric acid.
5. (Short, 4 marks) Distinguish between single and triple superphosphate.

Syllabus topics (RTMNU)

• Fuel Chemistry: Renewable and non-renewable. Classification of fuels and their calorific value
• Coal: Introduction of coal, uses and composition, carbonization of coal
• Coal gas, producer gas and water gas – composition and their uses
• Industrial methods for the fractionation of coal tar, uses of coal tar based chemicals
• Petroleum and Petrochemical Industry: Composition of crude petroleum, Refining and different types of petroleum products and their applications
• Fractional distillation, Cracking and Reforming
• Petroleum and non-petroleum fuels (LPG, CNG, LNG, biogas, fuels derived from biomass), fuel from waste, synthetic fuels (gaseous and liquids), clean fuels
• Petrochemicals: Vinyl acetate, Propylene oxide, Isoprene, Butadiene, Toluene and Xylene

Fuels — renewable and non-renewable; classification and calorific value

A fuel is a substance that burns in air/oxygen to give useful heat. Non-renewable fuels (coal, petroleum, natural gas) formed over millions of years and will be exhausted; renewable fuels (wood, biogas, biomass fuels, ethanol, biodiesel, hydrogen from renewable power) can be replaced quickly.

Calorific value: the heat released by complete combustion of unit mass (kJ kg^–1) or unit volume (kJ m^–3) of fuel. Gross (higher) calorific value includes the latent heat of the water vapour formed when it is condensed; net (lower) calorific value = GCV − latent heat of steam formed. A good fuel has high calorific value, moderate ignition temperature, low moisture and ash, controllable burning, low pollution and low cost.

(a) Coal — composition, uses and carbonisation

Coal is a fossil fuel formed from plant matter by heat and pressure (coalification): wood → peat → lignite → bituminous coal → anthracite (carbon content rises from about 50% to over 90%). It contains C, H, O, N, S and ash. Uses: thermal power, steel (as coke), cement kilns, source of coal tar chemicals.

Carbonisation: heating coal in the absence of air. Low-temperature carbonisation (500–700 °C) gives soft coke (domestic fuel) and more tar; high-temperature carbonisation (900–1200 °C, coke ovens) gives hard metallurgical coke, coal gas, ammoniacal liquor and coal tar.

Fractionation of coal tar: tar is distilled in a still and the fractions collected:

Uses of coal-tar chemicals: benzene and toluene (solvents, drugs, explosives), phenol (Bakelite, aspirin), naphthalene (mothballs, phthalic anhydride, dyes), anthracene (alizarin dyes), creosote (wood preservative).

(b) Petroleum — composition and refining

Crude petroleum is a dark viscous mixture of hydrocarbons — alkanes (paraffins), cycloalkanes (naphthenes) and aromatics — with small amounts of S, N and O compounds. Approx. C 80–85%, H 10–14%.

Refining: removal of water, salts and sulphur (desalting, Cottrell precipitation, copper oxide treatment) and fractional distillation in a tall fractionating column (crude heated to about 400 °C):

Cracking and reforming

• Cracking: breaking large hydrocarbon molecules into smaller ones (more petrol and alkenes). Thermal cracking: 450–750 °C, high pressure. Catalytic cracking: 450–550 °C, zeolite/silica–alumina catalyst, low pressure — gives better quality (branched, higher octane) petrol. Example: C₁₀H₂₂ → C₈H₁₈ + C₂H₄.
• Reforming: rearranging molecules to improve octane number — isomerisation, cyclisation and aromatisation over Pt catalyst (platforming): n-heptane → toluene + 4H₂.

Petroleum and non-petroleum fuels; fuel from waste; synthetic and clean fuels

• LPG: mainly propane and butane, liquefied under pressure; domestic cooking (an odorant, ethyl mercaptan, is added for leak detection).
• CNG: natural gas (mainly methane) compressed to about 200–250 bar; vehicle fuel, cleaner than petrol/diesel.
• LNG: natural gas cooled to about −162 °C to liquid for shipping.
• Biogas: anaerobic digestion of cattle dung/organic waste: CH₄ 55–65%, CO₂ 30–40%; slurry is good manure.
• Biomass fuels: bioethanol (fermentation of molasses/grains), biodiesel (transesterification of vegetable oils with methanol), wood pellets.
• Fuel from waste: refuse-derived fuel, landfill gas, pyrolysis oil from plastics and tyres.
• Synthetic fuels: gaseous (syngas CO + H₂, synthetic natural gas) and liquid (Fischer–Tropsch hydrocarbons from syngas over Fe/Co catalyst, methanol, coal liquefaction by Bergius process).
• Clean fuels: hydrogen (burns to water), CNG, LPG, ethanol blends, low-sulphur fuels — less pollution.

Petrochemicals

• Vinyl acetate: ethylene + acetic acid + O₂ over Pd catalyst → CH₂=CHOCOCH₃; monomer for polyvinyl acetate (adhesives, paints) and PVA.
• Propylene oxide: from propylene by the chlorohydrin process (Cl₂ + H₂O, then Ca(OH)₂) or by hydroperoxide/H₂O₂ oxidation; used for polyurethanes and propylene glycol.
• Isoprene: from C₅ cracking fractions (extractive distillation) or by dehydrogenation of isopentane/isopentene; monomer for synthetic (polyisoprene) rubber.
• Butadiene: separated from the C₄ fraction of steam cracking or by catalytic dehydrogenation of n-butane/butenes; used in SBR, nitrile and polybutadiene rubbers.
• Toluene and xylenes: from catalytic reforming of naphtha (BTX aromatics, separated by solvent extraction and distillation); solvents, TNT, benzoic acid; p-xylene → terephthalic acid → PET (polyester).

Likely exam questions

1. (Long, 8 marks) Describe the refining of crude petroleum by fractional distillation. Explain cracking and reforming.
2. (Long, 8 marks) What is carbonisation of coal? Describe the fractionation of coal tar and give the uses of coal-tar chemicals.
3. (Short, 4 marks) Distinguish between producer gas and water gas.
4. (Short, 4 marks) Define calorific value. Distinguish between gross and net calorific value.
5. (Short, 4 marks) Write a note on LPG, CNG and biogas.

Syllabus topics (RTMNU)

• Biological, physical and chemical treatments
• Treatment of water for refineries, thermal power station and domestic uses, reuse of cooling water
• Physical and chemical processes used for the recovery of important compounds from wastes: Activated carbon, adsorption, ion exchange process, evaporation, extraction, distillation, centrifugation, filtration, coagulation
• Membrane processes – osmosis, electrodialysis, evaporation, freezing processes
• Biological processes for the treatment of waste waters, trickle filters, activated sludge process, microbial degradations

Waste water — need for treatment and types of treatment

Waste water (sewage and industrial effluent) contains suspended solids, dissolved organic matter (measured as BOD and COD), oils, toxic metals, acids/alkalis, heat and pathogens. Untreated discharge depletes dissolved oxygen in rivers, kills fish and spreads disease. Treatment is done in stages:

1. Preliminary/physical (primary): screening, grit removal, oil–grease traps, sedimentation (removes settleable solids).
2. Chemical: neutralisation, coagulation–flocculation, precipitation of metals, oxidation (chlorine, ozone), disinfection.
3. Biological (secondary): micro-organisms oxidise dissolved organic matter (trickling filter, activated sludge, oxidation ponds, anaerobic digestion).
4. Tertiary/advanced: removal of N, P, colour and dissolved salts by adsorption, ion exchange, membranes; makes water fit for reuse.

Treatment of water for refineries, thermal power stations and domestic use; reuse of cooling water

• Refinery effluent: contains oil, phenols, sulphides, ammonia. Treatment: API oil–water separator → dissolved air flotation → sour-water stripping (H₂S, NH₃) → biological treatment (activated sludge) → activated carbon polishing.
• Thermal power station: boiler feed water must be very pure (to avoid scale, corrosion, priming and foaming) — clarification, softening, demineralisation by ion exchange or reverse osmosis, de-aeration, and internal conditioning (phosphate, hydrazine). Effluents include ash-pond water (settling), cooling-tower blowdown and acidic/alkaline regeneration wastes (neutralisation).
• Domestic water: screening → aeration → coagulation with alum → sedimentation → sand filtration → disinfection (chlorination, UV, ozone) → storage and supply.
• Reuse of cooling water: recirculating cooling systems with cooling towers reuse water many times; problems of scale, corrosion, microbial slime are controlled by side-stream filtration, softening, pH control, corrosion inhibitors and biocides; blowdown is limited (cycles of concentration).

Physical and chemical processes for recovery of important compounds from wastes

1. Activated carbon adsorption: porous carbon with huge surface area (500–1500 m² g^–1) adsorbs organics, colour, odour, phenols and some metals; carbon is regenerated by heating/steam and adsorbed solvents can be recovered.
2. Ion exchange: resins remove and concentrate metal ions (Cr, Cu, Ni, Au, Ag) from plating rinse water; regeneration gives a concentrated solution from which metal is recovered.
3. Evaporation: concentrates dissolved solids (e.g. recovery of salts, black liquor in paper mills, zero-liquid-discharge plants).
4. Solvent extraction: recovery of phenol, acetic acid or metals from effluent using an immiscible solvent.
5. Distillation: recovery of solvents (alcohols, acetone) from waste streams.
6. Centrifugation: separation of solids, oil and sludge by centrifugal force; dewatering of sludge.
7. Filtration: sand, pressure and vacuum filters remove suspended solids.
8. Coagulation: alum, FeCl₃ or polyelectrolytes neutralise the charge on colloids so they form flocs that settle (Al³⁺ + 3OH^– → Al(OH)₃ floc).
9. Membrane processes: reverse osmosis — pressure greater than osmotic pressure forces water through a semi-permeable membrane, leaving salts behind (desalination, effluent recycling); microfiltration, ultrafiltration, nanofiltration for smaller particles.
10. Electrodialysis: ions move under an electric field through alternate cation- and anion-exchange membranes, giving desalted and concentrated streams (brackish water desalting, salt recovery).
11. Freezing processes: on freezing, ice crystals of nearly pure water form and impurities stay in the brine; ice is separated and melted — used for desalination and concentrating effluents.

Biological processes for treatment of waste water

• Trickling filter: settled sewage is sprayed by a rotating arm over a bed of stones/plastic media coated with a biological film (bacteria, fungi, protozoa); aerobic microbes oxidise organic matter as the liquid trickles down; air enters from below. Simple, low energy; BOD removal about 80–90%.
• Activated sludge process: sewage is mixed with recycled "activated sludge" (a mass of active microbes) in an aeration tank with air blown in for several hours; organic matter is oxidised to CO₂ and H₂O and new cells; the mixture goes to a secondary clarifier, sludge settles, part is returned and the excess is digested. High BOD removal (90–95%).
• Microbial degradation: aerobic organisms (Pseudomonas, Bacillus etc.) mineralise organics; anaerobic digestion converts sludge to biogas (CH₄ + CO₂) in three stages — hydrolysis, acid formation, methane formation; special microbes degrade phenols, oils, dyes and pesticides (bioremediation). Oxidation ponds/lagoons use algae–bacteria symbiosis.

Likely exam questions

1. (Long, 8 marks) Describe the physical, chemical and biological methods of waste water treatment.
2. (Long, 8 marks) Explain the activated sludge process and the trickling filter for treatment of waste water with diagrams.
3. (Short, 4 marks) Write a note on reverse osmosis.
4. (Short, 4 marks) Explain electrodialysis.
5. (Short, 4 marks) How is water treated for use in a thermal power station?

Syllabus topics (RTMNU)

• Glass: manufacturing, annealing, types and uses
• Ceramics: definition, traditional and new ceramics, structure of ceramics
• Lubricants: Classification and properties of lubricants (viscosity index, cloud point, pour point)
• Lubricating oils (conducting and non-conducting), solid and semisolid lubricants, synthetic lubricants

Glass — manufacture, annealing, types and uses

Glass is an amorphous, transparent, super-cooled liquid — a fused mixture of silicates of alkali and alkaline earth metals. Ordinary (soda-lime) glass ≈ Na₂O·CaO·6SiO₂.

Raw materials: sand (SiO₂), soda ash (Na₂CO₃) or K₂CO₃, limestone (CaCO₃), cullet (broken glass, lowers melting point), decolourisers (MnO₂) and colouring agents.

Manufacture:

1. Melting: the batch is melted in a tank furnace at about 1400–1500 °C: Na₂CO₃ + SiO₂ → Na₂SiO₃ + CO₂; CaCO₃ + SiO₂ → CaSiO₃ + CO₂. Gas bubbles are removed (fining).
2. Shaping: blowing (bottles), pressing, drawing, rolling, float process (molten glass floated on molten tin for flat sheet glass).
3. Annealing: slow, controlled cooling in a long oven (lehr). Fast cooling leaves internal strains, making glass brittle; annealing removes these stresses.
4. Finishing: cutting, grinding, polishing.

Ceramics — definition, traditional and new ceramics, structure

Ceramics are inorganic, non-metallic solids made by shaping and then firing at high temperature. They are hard, brittle, heat-resistant, chemically inert and usually electrical insulators.

• Traditional ceramics: made from natural clay (kaolinite Al₂O₃·2SiO₂·2H₂O), feldspar and quartz — pottery, bricks, tiles, porcelain, sanitaryware, refractories, cement and glass in a broad sense.
• New (advanced) ceramics: made from pure synthetic compounds — alumina (Al₂O₃), zirconia (ZrO₂), silicon carbide (SiC), silicon nitride (Si₃N₄), titanates (BaTiO₃), ferrites; used in spark plugs, cutting tools, engine parts, electronic substrates, capacitors, bio-implants, superconductors and space shuttle tiles.

Structure: ceramics have ionic and/or covalent bonding. They may be crystalline (e.g. MgO with rock-salt structure, Al₂O₃ with close-packed O^2– and Al³⁺ in octahedral holes) or contain a glassy phase. Silicate ceramics are built from SiO₄ tetrahedra linked in chains, sheets (clays) or 3-D networks (quartz). Strong directional bonds and lack of free electrons explain hardness, brittleness, high melting point and insulating behaviour; porosity affects strength.

Lubricants — classification and properties

A lubricant is a substance placed between moving surfaces to reduce friction, wear and heat. It also cools, seals, prevents corrosion and carries away dirt.

Classification: (1) liquid lubricants (lubricating oils); (2) semi-solid lubricants (greases); (3) solid lubricants; (4) synthetic lubricants (and emulsions).

Properties

• Viscosity and viscosity index (VI): viscosity is resistance to flow; it falls as temperature rises. VI shows how little viscosity changes with temperature — a high VI (e.g. paraffinic oils, multigrade oils with VI improvers) is desirable.
• Cloud point: temperature at which an oil, on cooling, becomes cloudy because wax begins to crystallise.
• Pour point: lowest temperature at which the oil still flows. Low cloud and pour points are needed for cold climates.
• Others: flash and fire point (safety), oiliness, carbon residue, aniline point, acid value, emulsification, volatility.

Lubricating oils (conducting and non-conducting)

Mineral oils (from petroleum), vegetable/animal oils (castor, coconut, lard — good oiliness but oxidise) and blended oils with additives (antioxidants, VI improvers, pour-point depressants, anti-wear EP additives). Most lubricating oils are non-conducting (insulating) — e.g. transformer oil, which must have high dielectric strength and be free from moisture; electrically conducting lubricants (e.g. greases or oils loaded with graphite or metal powders) are used on sliding electrical contacts.

Solid and semi-solid lubricants

• Solid: graphite and molybdenum disulphide (MoS₂) — layered structures with weak forces between layers that slide easily; used under very high loads/temperatures or where oil would contaminate (food machinery, space). Also talc, PTFE.
• Semi-solid (greases): lubricating oil thickened with a metal soap (calcium, sodium, lithium); used where oil would leak or where frequent lubrication is not possible (bearings, gears). Lithium grease is multipurpose; calcium grease is water-resistant but low-temperature; sodium grease withstands heat but not water.

Synthetic lubricants

Man-made fluids for extreme conditions — polyalphaolefins, silicones (polydimethylsiloxane), ester oils, polyglycols, fluorocarbons. They have high VI, low pour point, high thermal and oxidation stability — used in jet engines, refrigeration compressors and high-performance car engines, but cost more.

Likely exam questions

1. (Long, 8 marks) Describe the manufacture of glass. What is annealing? Give the types of glass and their uses.
2. (Long, 8 marks) What are lubricants? Classify them and explain viscosity index, cloud point and pour point.
3. (Short, 4 marks) Distinguish between traditional and new ceramics.
4. (Short, 4 marks) Why are graphite and MoS₂ used as solid lubricants?
5. (Short, 4 marks) What are greases? Give their uses.