OCR Text |
Show z o C/) a: w z> o o 100~--~--~~~~~~~~1 90+----~--~~--~~~~--~--~ 80+----4~1~4---~,----~----~--~ 70~---~~-~~~--~+----+----~--~ 60~----4~~~~-4~~---r----r----1 50~--~~~--~~--+----+----~--~ 40~----~r~--~---+----~--~----1 ~ 30~--~~~~----+----+----4-----1 20~--~~~-r--~ @ 15,000 GHSV 1 04----~--f 0~--~~--~----+----4----~--~ 300 400 500 600 700 800 900 TEMPERATURE, DEGREES F --- VINYL CHLORIDE -AkO- DICHLOROBENZENE -?IE- _ CCI4 -H-BENZENE Figure 4 - Halohydrocarbon Destruction Catalyst- Oxidation of Va no us Compounds Poison Resistance Certain compounds commonly used in industry contain chemicals having silicones, phosphorus, sulfur or other organo-metallic compounds. The organic portion of these compounds are oxidized, leaving behind a metallic oxide covering the catalyst site where the oxidation occurred. The end result is the loss of the active site due to a masking effect and poisoning of the catalyst occurs. The active site might be recovered through various washing techniques. Research and development programs continue to seek ways of preventing this poisoning of the catalyst and currently support several formulations which display a lower affInity for the metallic oxide and thus display a longer than normal operating life. Formulations are currently being marketed as poison resistant catalysts for silicone, phosphorus, and sulfur. Figure 5 shows the effects of silicon accumulation vs. the hydrocarbon converting effIciency of a new Si resistant catalyst formulation in comparison with a reference catalyst formulation. Further to these formulations, another successful solution for catalyst systems contaminated in this way has been the regeneration of the catalyst. This technique will be discussed later in this paper. 5 |