Catalysts in the Contact process

V2O5 is used as a heterogeneous catalyst in the Contact Process... 

Orange-yellow Vanadium(V) oxide, V2O5, is used as an oxidizing agent/catalyst in the contact process for the manufacture of sulfuric acid. 

The oxides VO and V2O3 are basic, whereas VO2 can have both acid and basic properties. Vanadium pentoxide (V2O5), an acid anhydride, is the most important of the vanadium compounds whose main use is as a catalyst in the contact process for the manufacture of sulfuric acid. The compounds of vanadium in its different oxidation states exhibit varied colors. Compounds of V are lavender V, green V, blue and V, orange. 

In the finely divided state platinum is an excellent catalyst, having long been used in the contact process for producing sulfuric acid. It is also used as a catalyst in cracking petroleum products. Much interest exists in using platinum as a catalyst in fuel cells and in antipollution devices for automobiles. 

Sulfuric acid, H2S04, is produced commercially in the contact process, in which sulfur is first burned in oxygen and the S02 produced is oxidized to S03 over a V205 catalyst ... 

In the contact process for making H2S04, s is burned with air t0 S02, and S02-air mixture is then passed over a V20-, catalyst, which converts it to... 

Uses of Gels Gels have found several applications. Silica gel is used in laboratory and in industry and is also used to support the platinum catalyst, when this is used in the contact process of H2S04 manufacture. It is resistant to catalytic poisoning. Solidified alcohol (gel) is used as fuel in picnic stoves and is made from alcohol and calcium acetate. 

The catalyst used in the contact process of sulphuric acid manufacture is ... 

In the 1800s, the most important method for producing H2S04 was by the lead chamber process. Today, sulfuric acid is produced by a method known as the contact process. In the contact process, sulfur is burned to give S02 or the required S02 is recovered from coal burning or ore roasting processes. The S02 is then oxidized in the presence of a catalyst to produce SO3 (see Section 15.7.2). Typical catalysts are spongy platinum or sodium vanadate. Next, the SO3 is dissolved in 98% sulfuric acid ... 

In the contact process sulfur trioxide is made by the catalytic oxidation of sulfur dioxide (the name of the process refers to the fact that reaction occurs on contact of the gases with the solid catalyst). The catalyst formerly used was finely-divided platinum it has now been largely replaced by vanadium pentoxide, V O. The gas containing sulfur trioxide is then bubbled through sulfuric acid, which absorbs the sulfur trioxide. Water is added at the proper rate, and 98% acid is drawn off. 

According to this, SO 3 should be dissociated 5 per cent, at 527° C. and a pressure of one atmosphere. This is in agreement with technical experience, as the temperature in the contact process (with platinum as catalyst) must not exceed 450°. According to the accurate iritourements of Bodenstein and Pohl, the degree of dissociation of SO3 at 500° is 8 7 per cent. 

The aging and combustion kinetics of coke deposited on an HZSM-5 zeolite-based catalyst in the MTG process have been studied. The kinetic study of coke combustion in air was carried out at 500-550°C in a differential scanning calorimeter, by following the evolution of the combustion products with on-line FTIR analysis. The results provide evidence for limitations on coke reactivity that can be attributed to the combined effects of several circumstances (e.g. bad oxygen-coke contact and heterogeneous distribution of coke within the zeolite crystal). The need is demonstrated for a thermal aging treatment which equilibrates reproducibly the coke prior to combustion. The aging of coke is also limited by a peculiar coke deposit in the microporous stmcture of the zeolite. 

Reaction yields in the contact process were increased in several ways—by selecting an optimum temperature, using an efficient catalyst, removing a product from a reaction that does not go to completion, and by controlling the rate of reaction of SO3 with water. Keeping operating pressures at the correct values also increases yield. 

Vanadium has numerous industrial uses such as the processing of steel, chemical production, polymer synthesis, ceramics and electronics production (Nriagu, 1997). As a catalyst, V is used in the contact process for the production of sulfuric acid and a variety of organic reagents. Vanadium compounds are also used as mordants in dyeing and printing of cotton and silk (Nriagu, 1997). Because of the multiplicity of sources, the concentrations of vanadium in municipal wastewaters vary widely, from <1.0 to over 3000/rg/l (Blackmore et al, 1996 Adriano, 2001). 

In the contact process SO2 is converted to SO3 by use of a metal or metal-oxide catalyst. Platinum was once widely used as a catalyst, but because of its excessive cost and susceptibility to poisoning, it has largely been replaced by vanadium pentoxide. The SO3 is passed to an absorption tower where it is absorbed in recirculat-... 

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