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The Contact Process
Transcript of The Contact Process
SO3(g) + H2O(g) --> H2SO4 The Contact Process The Process History Best Conditions Importance Catalyst Works Cited The first observation of a "contact" process was made by Edmund Davy in 1817 (Friedman 3).
In 1831, Peregrine Phillips, a British vinegar manufacturer, patented the process of mixing oxygen and sulfur dioxide over heated platinum to produce sulfur trioxide (Friedman 3)
Vanadium was first used in the early 1900s.
In 1901, Kneitsch discovered temperatures should be lower and "made the contact process so successful that it could not only produce fuming acid cheaply, but it could compete with the established chamber process" (Friedman 5).
"A breakthrough about 1927 by Chemico with the development of the pressurized sulfur furnace [...] opened the way to the plants of today" (Friedman 2).
The contact process slowly grew to replace the chamber (or lead-chamber) process ("Contact Process"). Many catalysts have been used in its history, including copper, chromium, and platinum.
The currently used catalyst is vanadium, in the form V2O5.
Catalysts do not change equilibrium, but in the case of this reaction, the rate is extremely slow without one!
Vanadium is useful because it readily changes its oxidation number. During the reaction, V2O5 is required to change to V2O4, then back again.
Platinum catalysts were used originally, but "suffered from high costs and were easily poisoned by contaminants such as As2O3" ("Contact"). Sulfuric acid is consistently the most-produced chemical every year (by far) ("Production").
"Sulfuric acid has so many uses in industrial processes that it might be easier to look for objects that do not require some form of sulfuric acid or its derivatives as a part of the production process" (Ejim).
"Examples for the use of sulfuric acid in industry can be seen in the area of waste treatment, for the production of fertilizing agents and in the manufacture of various items ranging from explosives to dyes" (Ejim). "Chemistry-sulfuric Acid-contact Process." Chemistry-sulfuric Acid-contact Process. Dynamic Science, n.d. Web.
"Contact." Knowledge for the Sulphuric Acid Industry. DKL Engineering, Inc., n.d. Web. 10 Jan. 2013.
"Contact Process (chemistry)." Encyclopædia Britannica. N.p., n.d. Web.
Friedman, Leonard J., and Samantha J. Friedman. The History of the Contact Sulfuric Acid Process. Rep. Acid Engineering and Consulting, Inc., n.d. Web.
"Production: Growth in Most Regions." Chemical & Engineering News. American Chemical Society, 11 July 2005. Web.
"The Contact Process for the Manufacture of Sulphuric Acid." The Contact Process for the Manufacture of Sulphuric Acid. N.p., n.d. Web.
Ejim, Esther, and Kaci Lane Hindman. "What Are the Uses of Sulfuric Acid in Industry?" WiseGeek. Conjecture, n.d. Web. "Essentially all of the sulfuric acid produced today is made by the contact process" (Friedman 2). Step 1: Liquid sulfur reacts with dry air in the presence of fire to produce sulfur dioxide (SO2).
Step 2: The sulfur dioxide is oxidized to sulfur trioxide by oxygen using vanadium oxide as a catalyst.
Step 3: Concentrated sulfuric acid is added to sulfur trioxide and forms oleum (H2S2O7).
Step 4: Oleum is then mixed with water to obtain sulfuric acid. ("Chemistry"). It is best to input sulfur dioxide and oxygen in a 1:1 ratio (an excess of oxygen). The excess causes the reaction to shift to the right, making more sulfur trioxide ("The"). The forward reaction is exothermic (-196kJ/mol), so lowering the temperature shifts the equation to the right. However, the temperature cannot be too low, or it will react too slowly. The best temperature is 400 - 450°C ("The"). 2 SO2(g) + O2(g) --> 2 SO3(g) There are 3 molecules on the left side, and 2 molecules on the right, so increasing the pressure also shifts the reaction the the right. But plants usually do not spend money to create high pressures, because the other condition changes are sufficient to make 99.5% conversion at 2 atm ("The").