Contact Process Development

1875 Clemens and Winkler Dingl. Polyt. J.218, 128 (1875) 223, 409 (1877). Described experiments to produce oleum using 8.5% platinum on asbestos with pure oxygen (73.3% conversion) or air (47.4% conversion). Used stoichiometric ratio of SO2/O2. Pure sulfur dioxide from decomposing sulfuric acid. Sulfur trioxide absorbed in water to form oleum. Their results were not thermodynamically possible—Ostwald later claimed it delayed developments [Z. Electrochem. 8, 154(1902)]. 

1875 Squire (and Messel) British Patent 3278 (1875) resulted from high oleum price. Used a platinum catalyst supported on pumice with a stoichiometric mixture of SO2/O2 made from decomposing H2SO4 in a platinum still (70% recovery of SO3). Plant at Silvertown produced three tons of SO3 per week. Patent mentioned that this avoided catalyst deactivation with dust and, probably arsenic although poisons were not recognized. 

1875-1880 Jacob Operated a contact process oleum plant in Germany at first from decomposed chamber acid but later from sulfur burning (43% free SO3). Jacob sold his plant to Meister, Lucius, and Bruning at Hoechst, who still made oleum in 1925. 

1879 Thann Chemical Works, Alsace Acquired an improved oleum process design from Squire. Burned Sicilian sulfur and washed gas at 4 atm pressure. Mixed SOrwith stoichiometric volume of air and formed SO3 using platinized asbestos. Output 1.5 tons of SO3 per day and dissolved in concentrated H2SO4. 

1880s BASF Began to use the same process as Thann, producing such large volumes that the oleum price fell. Production increased from 18,500 tons during 1880 to 116,000 tons by 1900. 

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Monarch A process for saving energy in sulfuric acid plants using the contact process. Developed by Monsanto. 

Sulfuric acid is produced industrially by a method known as the contact process, developed in the early twentieth century. In this method, elemental sulfur is first heated in air to form SO2 gas, which is then heated in contact with a V2O5 catalyst to form SO3 gas. 

Equipment Absorption, stripping, and distiUation operations are usually carried out in vertical, cylindrical columns or towers in which devices such as plates or packing elements are placed. The gas and liquid normally flow countercurrently, and the devices serve to provide the contacting and development of interfacial surface through which mass transfer takes place. Background material on this mass transfer process is given in Sec.. 5. 

Photographic processing Developing gives no trouble with the Cr-Ni steels, but for contact with acid fixing solutions 316S16 steel should be specified. 

CAT-OX [Catalytic oxidation] An adaptation of the Contact process for making sulfuric acid, using the dilute sulfur dioxide in flue-gases. A conventional vanadium pentoxide catalyst is used. Developed by Monsanto Enviro-Chemical Systems, and operated in Pennsylvania and Illinois in the early 1970s. 

Knietsch An early version of the Contact process for making sulfuric acid. Developed by R. Knietsch at BASF, Ludwigshaven. 

The production of sulphuric acid by the contact process, introduced in about 1875, was the first process of industrial significance to utilize heterogeneous catalysts. In this process, SO2 was oxidized on a platinum catalyst to S03, which was subsequently absorbed in aqueous sulphuric acid. Later, the platinum catalyst was superseded by a catalyst containing vanadium oxide and alkali-metal sulphates on a silica carrier, which was cheaper and less prone to poisoning. Further development of the vanadium catalysts over the last decades has led to highly optimized modem sulphuric acid catalysts, which are all based on the vanadium-alkali sulphate system. 

In this process developed by Lurgi [17], the phenolic effluent is contacted with the solvent in a multistage mixer-settler countercurrent extractor (Fig. 10.8). The extract, containing phenol, is separated into phenol and solvent by distillation and solvent is recycled to the extractor. The aqueous raffinate phase is stripped from solvent with gas, and the solvent is recovered from the stripping gas by washing with crude phenol and passed to the extract distillation column. 

Some of its compounds, particularly the oxides, are used in chemical industries as catalysts to speed up organic chemical reactions. The yellow-brown vanadium pentoxide (V O ) is used as a catalyst to facilitate the production of sulfuric acid by the contact process. Vanadium pent-oxide is also used as a photographic developer, to dye textiles, and in the production of artificial rubber. When combined with glass, it acts as a filter against ultraviolet rays from sunlight. 

The contact process was invented by Phillips in England in 1831 but was not used commercially until many years later. Today 99% of all sulfuric acid is manufactured by this method. It was developed mainly because of the demand for stronger acid. All new contact plants use interpass absorption, also known as double absorption or double catalysis. This process will be described in detail in Fig. 2.3. 

The lead-chamber process supplied the worlds need for sulfuric acid for a century and a half. In the late 19th century, the contact process replaced the lead-chamber process and is still used today to produce the world s supply of sulfuric acid. The contact process was first developed by Peregrine Phillips (1800- ), a British acid dealer, in 1831. The contact process used sulfur dioxide, S02, which was produced as a by-product when sulfur-bearing ores were smelted. The contact process was named because the conversion of sulfur dioxide to sulfur trioxide, S03, takes place on contact with a vanadium or platinum catalyst during the series of reactions ... 

The Bio-FGD process converts sulfur dioxide to sulfur via wet reduction (10). The sulfur dioxide gas and an aqueous solution of sodium hydroxide are contacted in an absorber. The sodium hydroxide reacts with the sulfur dioxide to form sodium sulfite. A sulfate-reducing bacteria converts the sodium sulfite to hydrogen sulfide in an anaerobic biological reactor. In a second bioreactor, the hydrogen sulfide is converted to elemental sulfur by Thiobacilh. The sulfur from the aerobic second reactor is separated from the solution and processed as a sulfur cake or liquid. The process, developed by Paques BV and Hoogovens Technical Services Energy and Environment BV, can achieve 98% sulfur recovery. This process is similar to the Thiopaq Bioscrubber process for hydrogen sulfide removal offered by Paques. 

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