Uses • P Manufacture of paper • Di Manufacture of drugs • Di Manufacture of dyes has a ... • P Manufacture of pigments • H Household • DDetergent (manufacture ) in... • Beats As the electrolyte in car batteries • Per Petroleum refining • Minute Metallurgical processes
The production of Sulfuric Acid is a STRONG indicator of a countries industrial activity • 75% of the Sulfuric Acid that is produced is used to make fertilisers such as • Superphosphate • Ammonium sulphate and • Ammonium phosphate.
Superphosphate • Rock phosphate contains insoluble Calcium Phosphate. What is the formula for Calcium Phosphate??? • Ca3(PO4)2 • To be made available to plants it needs to be converted to a soluble form: • Ca3(PO4)2,(s) + 2H2SO4 (l) + 4H2O Ca(H2PO4)2 (s) + 2CaSO4 • 2H2O (s)
“Here rocky rockyrocky” • Australia has substantial rock phosphate resources, especially in Queensland • Australian companies usually import rock phosphate from North Africa. WHY? • Cheaper
Diprotic and powerful acid • H2SO4 (l) + H2O (l) HSO4-(aq) + H3O+ (aq) The Ka for this reaction is very high • HSO4-(aq) + H2O (l) SO42-(aq) + H3O+ (aq) The Ka for this reaction is small • These reactions are EXTREMELY exothermic. Because of this it is important to add acid to the water and not the other way around. • The reaction is so exothermic that water becomes steam and causes the solution to splutter, causing serious injury.
As a dehydrating agent • Sulphuric acid acts as a catalyst in the following reactions: C1 2H22O11 (s) (with H2SO4) 12C (s) + 11H2O (l) • Is this a condensation reaction, hydrolysis reaction or neither?
Dehydration • CuSO4 • 5H2O (s) CuSO4 (s) + 5H2O(l) • Sulphuric acid can even be used as a dehydrating agent for gases by bubbling them through the sulphuric acid. • However, these gases cannot be bases (i.e. NH4) or reductants. Why?
Dehydration • What health implication might there be for sulphuric acid being such a strong dehydrating agent?
Caution! • If sulfuric acid is spilt on the skin, wash with running water (wink wink, hint hint) • If there is a large amount of sulfuric acid, first wipe it off quickly
As an oxidant • A very strong oxidant, especially when hot. • H2SO4 can be reduced to SO2 S or H2S : • Zn (s) + 2H2SO4 (l) ZnSO4 (aq) + H2O (l) + SO2 (g) • 3Zn (s) + 4H2SO4 (l) 3ZnSO4 (aq) + 4H2O (l) + S (s) • 4Zn (s) + 5H2SO4 (l) 4ZnSO4 (aq) + 4H2O (l) + H2S (g) • However, when zinc reacts with dilute H2SO4: • Zn (s) + H2SO4 (l) ZnSO4 (aq) + H2 (g) • For each of the reactions above, identify the oxidation numbers of Sulfur.
The “Contact Process” • The production of H2SO4 usually follows the following process: S SO2 SO3 H2SO4 • This is know as “The Contact Process”
S and SO2 can be obtained from: • Combustion of sulphur recovered from natural gas and crude oil • SO2 formed during the smelting of sulphuric ores of Cu, Zn or Pb • It can be mined directly. This is not necessary in Australia
Step 1 • If solid sulfur is the starting point it is made molten and then sprayed under pressure into a furnace. • It will then combust in air to produce SO2 • The high surface area of molten S results in a very fast combustion reaction. • S(l) + O2(g) SO2 (g) Δ H = -297 kj mol-1 • Temperature may reach 1000°C so SO2 needs to be cooled
Step 2 • SO2 is converted to SO3 with the use of the V2O5 catalyst. • 2SO2 (g) + O2(g)(with V2O5 ) 2SO3 (g)Δ H = -197 kj mol-1 • Where does this reaction occur? Well, thanks for asking, it occurs in a .....
Converter! • SO2 is mixed with air and passed through trays containing loosely packed porous pellets of the catalyst V2O5 • Because the reaction is so exothermic it must continually be cooled • The temperature in the converter is maintained at 400 - 500°C and a pressure of 1 atmosphere • Nearly complete conversion from sulphur dioxide to sulphur trioxide is achieved. SO?
And now over to you- • Use Le Chatelier’s principle to determine what temperatures and pressure is desired for this reaction. • Also, would excess reactants be employed? • Excess products? Why/Why not? • What about dilution?
Le Chatelier • Temperature: Because the reaction is exothermic Le Chatalier predicts the reaction will become more product favoured when the temperature is decreased • Because the generation of products decreases pressure, an increase in pressure will push the reaction forward • By supplying excess reactants the system will try to re-establish equilibrium by getting rid of those reactants. This will also push the reaction forward.
Rate of reaction • What factors will increase the rate of reaction? • High Temperature • High Pressure • The use of a catalyst
Le Chatelier VS Speed: Path to Victory • In most instances both a product favoured reaction and a speedy reaction desire the same factors. • Excess oxygen is used as the excess reactant • Even though increased pressure increases the rate of reaction and pushes it forwards, manufacturers do not bother as high yields are achieved without this costly addition. • Le Chatelier dictates that a low temperature will push the reaction forward. However, the rate of reaction will slow with reduced temperature. What to do?!
Catalyst • Luckily, the catalyst saves the day by making lower temperatures viable. • The effect of the catalyst is maximised by spreading it over trays which increases the surface area. • The catalyst can become ‘poisoned’ and rendered ineffective by dust. Therefore the air and sulphur dioxide pass through electrostatic precipitators before they enter the converter.
Step 3 • Absorption of SO3 • SO3 (g) + H2O (l) H2SO4 (aq) Δ H = -130 kj mol-1 • Direct reaction with water is very exothermic which results in the formation of steam. Sulfuric acid as a gas is very difficult to collect so an absorption tower is used instead: • H2SO4 (aq) + SO3 (g) H2S2O7 (l) This product is called oleum • Very little reactant is left. Oleum is then mixed with water: • H2S2O7 (l) + H2O (l) 2H2SO4 (l) • Sometimes the reactions occur simultaneously: • H2SO4 (aq) + SO3 (g) + H2O (l) 2H2SO4 (l)
Waste Management • Plants built after 1970 use ‘double desorption’ processes. The unreacted SO2 is passed back through the catalytic converter. This increases efficiency from 98% to 99.6% • SO2, SO3 and H2SO4 emissions are continuously monitored. • H2SO4 mist is minimised by controlling the operating temperature of the absorber, gas flow rates and concentrations. • H2SO4 has a high boiling temperature of 290°C and a low vapour pressure. There is no appreciable air pollution problem with its storage, handling and shipping. • Cooling water is usually recycled
Waste and catalysts • Improvements to conversion have occurred by adding small amounts of cesium to the V2O5 catalyst. • This has increased efficiency and allows the reaction to occur at even lower temperatures. • Unfortunately the presence of cesium increases the cost of the catalyst by three times. • Spent Vanadium is slightly toxic so it needs to be recovered from ‘poisoned’ catalyst before the catalyst is disposed of in landfill.
Green Energy? • “The ‘Contact Process’ actually reduces pollution!” • Prove or disprove this statement. • 2 minutes 2 reasons
GREEN • By using the sulphur by products of other reactions it prevents these pollutants escaping into the atmosphere. • This helps to prevent acid rain. Yay! • More energy is produced in the process than is used by it. Another yay! • This energy is recycled by the plant and can even be sold to other plants for use in chemical manufacture. • Sometimes the energy is used to produce ‘green’ electricity.
Health and Safety • Transport procedures need to be in place for loading and unloading • H2SO4 is highly corrosive. It is a strong dehydrating agent. It can burn eyes and skin severely. It can cause blindness and 3rd degree burns. • Sulfuric acid mist can cause problems such as pulmonary oedema (fluid in the lungs). • Sulphur dioxide and sulphur trioxide are respiratory irritants, damage plants and contribute to acid rain. • Oleum is a highly corrosive, oily liquid, that produces SO3 fumes. These fumes can build up and accidental release procedures need to be in place. • Work areas must be well ventilated and employees must wear protective clothing. • Acid spills are contained using materials such as earth, clay or sand, then slowly diluted with water before being neutralised with a base (usually CaCO3 or Na2CO3)
Test yourself... • What does “P DiDi has a PhD in Beats Per Minute” stand for? • What is the name, location of and formula for the catalyst that is used? • Vanadium Pentoxide, Converter, V2O5 • What is the chemical formula for Oleum? H2S2O7 • Which reaction occurs in the ‘converter’? SO2 to SO3 • What two reactions need to occur for the adsorption of sulfur trioxide? • SO3 + H2SO4 H2S2O7 • H2S2O7 + H2O 2H2SO4 • How is sulfur converted to sulfur dioxide? • Molten sulfur is sprayed into the air • Write the formula for the production of superphosphate
And now, here’s something we hope you’ll really like • http://www.youtube.com/watch?v=zTLiJE-j1-I
Homework • From Chapter 22 Answer: • Q 2, 3, 5, 6, 7, 8, 9, 10, 11, 13, 15 • You will have a SACT test on sulfuric acid and its production next Monday, so get studying!