Section 8: How To Make Sulfur

SECTION 8 : HOW TO MAKE SULFUR Sulfur is found on earth in free and compound form. Solid sulfur has two allotropic forms, namely rhombic sulfur and monoclinic sulfur. The sulfur that we usually see is rhombic sulfur, with a yellow color, this sulfur is stable below a temperature of 95.5 °C. If the temperature is above 95.5 °C, rhombic sulfur will change to monoclinic sulfur which will melt at a temperature of 113 °C. Usually sulfur is found in the form of sulfide and sulfate minerals, hydrogen sulfide, and organic sulfur compounds.Sulfur can be obtained by extraction through the Frasch process. The underground sulfur is melted by flowing superheated water (a mixture of water and water vapor with a pressure of around 16 atm and a temperature of around 160 °C) through the outer pipe of an arrangement of three concentric pipes. The liquid sulfur is then forced out by pumping hot air (with a pressure of around 20 – 25 atm). After that the sulfur is allowed to freeze. The sulfur obtained in this way has a purity of up to 99.6%, this is because sulfur does not dissolve in water.The main uses of sulfur are to make sulfuric acid, vulcanize rubber, and eradicate plant diseases. Sulfur is also used to make CS2 and other sulfur compounds. 1. Sulfuric Acid Sulfuric acid is a thick, colorless and hygroscopic liquid. Concentrated sulfuric acid is an oxidizing acid. Compounds containing H and O will burn when concentrated sulfuric acid is poured on them. This is because sulfuric acid can attract hydrogen and oxygen from its compounds.Sulfuric acid can be obtained using two methods. a. Contact Process The raw material for sulfuric acid is SO2 gas which is obtained bypyrite roasting or sulfur burning. Reaction: 4FeS2 + 11O2 2Fe2O3 + 8SO2 or S + O2 SO2 The resulting sulfur dioxide gas is mixed with air, flowed through a contact catalyst (V2O5 ) at a temperature of ± 500 °C with a pressure of 1 atm. In this reaction, V2O5 not only acts as a catalyst but also acts as an oxidizer. The resulting O3 gas is channeled into a dilute sulfuric acid solution resulting in pyrosulphic acid. Reaction: SO3 + H2SO4 H2S2O7 By adding water to this mixture, concentrated sulfuric acid (98%) is obtained. Reaction: H2S2O7 + H2O 2H2SO4 b. Lead Booth Process The raw material in this process is SO2 , the same as the contact process.The catalyst used in this process is NO and NO2 gas . SO2 , NO, NO2 and water vapor are channeled into a chamber whose interior is coated with Pb (lead). SO2 gas from roasting is channeled into the glover tower along with nitric acid. In this case nitric acid is decomposed into NO and NO2 . The gas mixture is flowed into the lead chamber together with air and water vapor until a reaction occurs. Reaction: 2SO2 + O2 + NO + NO2 + H2O 2HNOSO4 (nitrosyl acid) Nitrosyl acid (HNOSO4 ) reacts with H2O to form sulfuric acid (H2SO4). Reaction: 2HNOSO4 + H2O 2H2SO4 + NO + NO2 NO and NO2 gas is channeled to the Gay Lussac tower and then converted into HNO3 . Meanwhile, the nitric acid will flow back to the glover tower and so on. The sulfuric acid formed will be channeled to the storage tank.Sulfuric acid is widely used in the fertilizer and detergent industry.Apart from that, it can also be used in the metal industry, dyestuffs, explosives, medicine, petroleum refining, and for battery chargers.