The contact process is the current method of producing sulfuric acid in the high concentrations needed for industrial processes. Sulfuric (or sulphuric acid, H 2 S[[oxygen O]]4 is a strong Mineral acid. Vanadium(V) oxide is the catalyst employed. Vanadium(V oxide ( vanadia) is the Chemical compound with the formula V2O5 Catalysis is the process in which the rate of a Chemical reaction is increased by means of a Chemical substance known as a catalyst
This process was patented in 1831 by the British vinegar merchant Peregrine Phillips, as a far more economical process for producing sulfur trioxide and concentrated sulfuric acid than the previous lead chamber process method used for producing sulfuric acid. Vinegar is an acidic liquid processed from the Fermentation of Ethanol in a process that yields its key ingredient Acetic acid (also called ethanoic acid Sulfur trioxide (also spelled sulphur trioxide) is the chemical compound with the formula SO3 The lead chamber process was an industrial process used to produce relatively strong concentrations of Sulfuric acid in large quantities
Process
The process can be divided into three stages:
- Preparation and purification of sulfur dioxide
- Catalytic oxidation (using vanadium oxide catalyst) of sulfur dioxide to sulfur trioxide
- Conversion of sulfur trioxide to sulfuric acid
Purification of air and SO2 is necessary to avoid catalyst poisoning (ie. Catalysis is the process in which the rate of a Chemical reaction is increased by means of a Chemical substance known as a catalyst Redox (shorthand for reduction-oxidation reaction describes all Chemical reactions in which atoms have their Oxidation number ( Oxidation state Sulfur trioxide (also spelled sulphur trioxide) is the chemical compound with the formula SO3 Catalysis is the process in which the rate of a Chemical reaction is increased by means of a Chemical substance known as a catalyst removing catalytic activities). The gas is then washed with water and dried by H2SO4. Water ( H2[[oxygen O]] H OH) is the most abundant Molecule on Earth 's surface composing of about 70% of the Earth's surface as
To conserve energy, the mixture is heated by exhaust gases from the catalytic converter by heat exchangers.
Sulfur dioxide and oxygen then react in the manner as follows:
- 2 SO2(g) + O2(g) ⇌ 2 SO3(g) : ΔH = −197 kJ mol−1
To increase the reaction rate, high temperatures (450 °C), high pressures (10 atm), and vanadium(V) oxide (V2O5) are used to ensure a 99. Oxygen (from the Greek roots ὀξύς (oxys (acid literally "sharp" from the taste of acids and -γενής (-genēs (producer literally begetteris the The Standard atmosphere is an international reference pressure defined as 101325 Pa and formerly used as unit of Pressure (symbol atm Vanadium(V oxide ( vanadia) is the Chemical compound with the formula V2O5 5% conversion. Platinum would be a more suitable catalyst, but it is very costly and easily poisoned. Platinum (ˈplætɪnəm is a Chemical element with the Atomic symbol Pt and an Atomic number of 78 The catalyst only serves to increase the rate of reaction - it has no effect on how much SO3 is produced.
Hot sulfur trioxide passes through the heat exchanger and is dissolved in concentrated H2SO4 in the absorption tower to form oleum:
- H2SO4(l) + SO3 → H2S2O7(l)
Note that directly dissolving SO3 in water is impractical due to the highly exothermic nature of the reaction. Oleum ( Latin oleum = "oil" or fuming sulfuric acid refers to a solution various compositions of Sulfur trioxide in Sulfuric An exothermic reaction is a Chemical reaction that releases Heat. Acidic vapour or mists are formed instead of a liquid.
Oleum is reacted with water to form concentrated H2SO4.
The average percentage yield of this reaction is around 30%.
- H2S2O7(l) + H2O(l) → 2 H2SO4(l)
DCDA
The next step to the Contact Process is DCDA or Double Contact Double Absorption. In this process the product gases (SO2) and (SO3) are passed through absorption towers twice to achieve further absorption and conversion of SO2 to SO3 and production of higher grade sulphuric acid.
SO2 rich gases enter the catalytic converter, usually a tower with multiple catalyst beds, and get converted to SO3, achieving the first stage of conversion. The exit gases from this stage contain both SO2 and SO3 which are passed through intermediate absorption towers where sulphuric acid is trickled down packed columns and SO3 reacts with water increasing the sulphuric acid concentration. Though SO2 too passes through the tower it is unreactive and comes out of the absorption tower.
This stream of gas containing SO2, after necessary cooling is passed through the catalytic converter bed column again achieving upto 99. 8% conversion of SO2 to SO3 and the gases are again passed through the final absorption column thus resulting not only achieving high conversion efficiency for SO2 but also enabling production of higher concentration of sulphuric acid H2SO4.
The industrial production of sulphuric aicd involves proper control of temperatures and flow rates of the gases as both the conversion efficiency and absorption are dependent on these. Elncid (talk) 12:16, 11 June 2008 (UTC)
References
- Jim Clark (2002). The Contact Process. Chemguide.
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