Production Of Sulphuric Acid 433i6v

Production of Sulphuric Acid The Process Introduction In the processes, the sulphur dioxide is converted to sulphur trioxide by the use of metal oxide catalyst. Platinum was once widely used as catalyst but because of it’s excessive first cost and susceptibility to poisoning, it has been largely replaced by vanadium oxide. The vanadium pent oxide is dispersed on a porous carrier in a pellet form. The characteristics of the catalyst which can be used are mentioned as follows:  Porous carrier having large surface area, controlled pore size and resistance to process gases at high temperature; in pellet form if used in fixed bed and powdered form if used for fluidized bed. Ex- Alumina, silica gel, zealots.  Active catalytic agent: Vanadium pent oxide in this case. Preparations are generally kept secret for the competitive reasons but they usually consist of adding water soluble compounds  to gels or porous substrates and firing at temperature below the sintering point.  Promoter: Alkali and/or metallic compounds added in trace amounts to enhance the activity of the catalytic agent. Advantages of the V2O5 catalyst  Relatively immune to poisons.  Low initial investment and only 5% replacement per year. Disadvantages of V2O5 catalyst  Must use dilute SO2 input (7-10%).  As a catalyst it is less active and requires high oxygen or sulphur dioxide to give economic conversions  Requires larger converters and thus higher initial investment. Now the SO3 gas is ed to an absorption tower where it is absorbed in recalculating

concentrated acid. There are many variations in the process depending upon the types of raw materials available and other considerations; also a number of engineering variations are in use by many different design/construction firms offering services in this field. Methodology There are two major processes used in the production of H2SO4 the lead chamber process and the process. The lead-chamber process is the older of the two processes, and its product is aqueous sulfuric acid containing 62% to 78% H2SO4. The process yields pure sulfuric acid. In both processes, sulfur dioxide, SO2, is oxidized to sulfur trioxide, SO3, and the SO3 is dissolved in water. Sulfur dioxide is obtained by burning sulfur, S(s) + O2(g) xxv SO2(g) by roasting pyrite (iron sulfide) or other metal sulfides prior to smelting, 4 FeS(s) + 7 O2(g) xxv 2 Fe2O3(s) + 4 SO2(g) or by burning hydrogen sulfide, H2S(g) + O2(g) xxv SO2(g) + H2O(g) The sulfur dioxide is oxidized to sulfur trioxide catalytically. 2 SO2(g) + O2(g) Catalyst 2 SO3 xxxv (g) Without the catalyst, the oxidation of SO2 is quite slow. In the old lead-chamber process, the catalyst is nitrogen dioxide gas. In the process, the catalyst is vanadium(V) oxide, V2O5 , mixed with an alkali metal sulfate. The mixture is ed on small silica beads, and at the high temperature inside the reactor, the mixture is a liquid. The product SO3 is dissolved in 98% sulfuric acid. The dissolved SO3 reacts with the 2% water, forming H2SO4.SO3(g) + H2O(l) Pure sulfuric acid is a colorless, odorless, oily liquid. It freezes at 10.5EC. It fumes when heated,because some of the H2SO4 decomposes to H2O and SO3. The H2O is retained in the liquid, while SO3 gas

is released. Therefore, the concentration of H2SO4 decreases, reaching a concentration of 98.33%. This solution boils at 338EC and is the material sold as “concentrated sulfuric acid.” Concentrated sulfuric acid, which is 18M, has a strong affinity for water and is sometimes used as a drying agent. It can be used to chemically remove water from many compounds. It dehydrates sucrose (table sugar), C12H22O11, leaving a spongy black mass of carbon and diluted sulfuric acid. Concentrated sulfuric acid reacts similarly with skin, paper, and other animal and plant matter. When it is mixed with water, a highly exothermic reaction occurs, and the energy released can be enough to heat the mixture to boiling. Therefore, concentrated sulfuric acid must be diluted by adding the acid slowly to cold water while the mixture is stirred to dissipate the heat.Sulfuric acid has a wide range of uses and plays a part in the production of nearly all manufactured goods. About 65% of the H2SO4 produced annually is used in the production of agricultural fertilizers.

Using Le Chatelier's principle, the equilibrium yield of sulfur trioxide should increase when: - temperatures are low, since the reaction is exothermic; - pressure is high; - excess reactants are present. However the rate of the reaction is high when: - temperature is high, hence an obvious conflict exists with the equilibrium yield; - the pressure is high; - a catalyst is used. The conflict between increased yield and fast rate is resolved by the use of a catalyst. The use of a catalyst enables low temperatures to be used in the reaction vessel while maintaining a very high rate of reaction. The vanadium(v)oxide catalyst is made into a porous solid and layed out in several beds to increase the surface area exposed to the reactants. Keep in mind, a catalyst does not influence the equilibrium yield only the rate at which equilibrium is reached. The yield is further improved by using excess air in the reaction mixture and since the reaction occurs at atmospheric pressure the need for expensive, high pressure equipment is eliminated