(231e) Novel Catalytic Approach Towards C4 Olefins and Gasoline Octane in Fluid Catalytic Cracking

Many refiners in North America have an economic incentive to produce more LPG olefins (preferably butylene’s) within the fluid catalytic cracking (FCC) product streams to serve as feed reactants in downstream alkylation processes in order to increase the octane value of the overall refinery gasoline pool. In this paper, we will discuss the reaction networks involved in acid-catalyzed light olefins formation, the variables that determine gasoline octane, and the ways by which Grace can exploit such pathways using novel catalytic solutions that increase butylene yield and octane value within the FCC unit. Such governing principles are validated by significant value uplifts within commercial operations that leverage these novel technologies.

Within traditional FCC technologies, the zeolite Y modification, commonly via lowering the zeolite unit cell size, is employed to decrease hydrogen transfer thus leading to higher light olefins yields. However, lower zeolite unit cell size is achieved by reducing zeolite rare earth stabilization, which decreases the acid site density of the zeolite, leading to lower activity per unit of zeolite. Addition of ZSM-5 to the catalyst increases the yield of LPG olefins via scavenging of gasoline olefins formed on Y zeolite, however, traditional ZSM-5 additives favor the formation of propylene over butylene, which is not as desirable for alkylation.

In recent years, Grace has commercialized several catalyst technologies, including ACHIEVE^®400, ACHIEVE^®400 Gold, and ACHIEVE^®400 Prime. These solutions are producing high value alkylation feedstock, shifting product yields toward higher butylene to propylene ratios and rendering high-octane FCC gasoline. ACHIEVE^®400 incorporates isomerization activity within the catalyst particle by using two different types of zeolites – a traditional Y zeolite and a specially tuned pentasil zeolite. Incorporation of isomerization activity into the particle itself results in a more desirable yield pattern than the use of a traditional ZSM-5 additive.