Petroleum cracking catalysts, rare

Figure 2. Rare earth usage in petroleum cracking catalysts as a function of total...

Chemical prqperties are also used in the largest field of application for the rare earth elements as catalysts. Most important are the cracking catalysts for the petroleum industry. The rare earth elements are combined into molecular sieves (Y-Zeolite) and serve in fluid bed or fixed bed reactors to increase the yield of gasoline. In addition thereto, there are the combustion catalysts for automobiles and for air pollution control. 

Since 1962 rare earths have been used to stabilize zeolite cracking catalysts for the petroleum industry (1, 2. Until recently this application to catalysis has been the only commercially significant one. Currently, however, a number of new applications of potential commercial significance are appearing. One of the most important of these is the use of cerium in catalysts for automobile exhaust emission control. We will emphasize this application in our review without neglecting other applications. 

Y zeolites exchanged with rare earth cations are widely used as the active component for cracking catalysts in petroleum industry. Such cations improve the catalytic activity and the gasoline yield, lowering the gas production and the coke formation. They also promote the thermal and hydrothermal stability of the catalyst. 

Petroleum hydrocarbon cracking catalysts usually contain more than 12 elements, including transition metals, rare earth elements (REEs), and alkali and alkaline earth elements at concentrations varying from 0.005 to 35 wt%. The composition of the catalyst can be determined accurately after fusion into borate beads the total analysis takes up to 1 h. The procedure and approach is described in ASTM D7085. Lubrication oil blenders use EDXRF to check their blends and ensure that control samples from lube shops are what the products claim to be (ASTM D6481 outlines the procedure). 

The spectrum of petroleum products from straight distillation of crude oil rarely matches the market demand and there is a surplus of the "heavier" compounds. As a result it is usual to employ catalysts to assist cracking reactions to produce... 

Lanthanum, or virtually all rare earth cations, are important constituents of catalysts employed in cracking of vacuum distillates from petroleum [77]. Thus, it seemed interesting to explore the possibility of introducing La cations into... 

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