Silica-alumina catalyst bead development

In 1944, Socony-Vacuum Oil Company started manufacture of synthetic silica-alumina catalyst in the form of beads (262). This catalyst was reported to contain about 10% alumina. The bead catalyst gives about the same product distribution as the pelleted synthetic catalyst and was developed primarily to achieve greater physical strength for use in the TCC process. The bead catalyst has also been used in Houdry fixed-bed units (51,171). Subsequently, a harder bead catalyst was developed for use in the air-lift units. The improved bead catalyst consists of approximately 15% alumina and 85% silica and contains 0.003% chromium to minimize afterburning by suppressing formation of carbon monoxide during regeneration (333). 

The synthetic silica-alumina bead catalyst developed at Socony-Vacuum had a distinct advantage because of its resistance to attrition. The bead also allowed for operating without the need of baffles in the reactor therefore, more reactor space was occupied by catalyst and the operation without baffles was much simpler. 

The desire to have catalysts that were uniform in composition and catalytic performance led to the development of synthetic catalysts. The first synthetic cracking catalyst, consisting of 87% silica (Si02) and 13% alumina (AI2O3), was used in pellet form and used in fixed-bed units in 1940. Catalysts of this composition were ground and sized for use in fluid catalytic cracking units. In 1944, catalysts in the form of beads about 2.5 to 5.0 mm in diameter were introduced and comprised about 90% silica and 10% alumina and were extremely durable. One version of these catalysts contained a minor amount of chromia (Cr203) to act as an oxidation promoter. 

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