Dual-function cracking catalysts

Characterization of Dual-Function Cracking Catalyst Mixtures... 

Surface vanadium appears to be most stable (to reduction) at low (<1%) V concentration when present as monomeric vanadyl units. Its stability decreases with increasing V levels. It is least stable (to reduction) at high (5%) V levels when present as a supported Vanadia phase. This difference in reactivity with V concentrations is believed responsible for the rapid decline in cracking activity observed in dual function cracking catalysts containing alumina when V start to exceed the 1.0-1.25 wt.% level (4). Further details of the mechanism of catalyst deactivation by V age the subject of continuing investigations 1n our laboratories by 31V solid state NMR, XPS, and Raman spectroscopy. 

Hydrocarbon Cracking Selectivities with Dual-Function Zeolite Catalysts... 

For optimal performance of dual function isomerization catalysts based on zeolite Y or mordenite, extensive removal of sodium is necessary. The finished catalyst must be highly crystalline, and the finely dispersed metallic hydrogenation function should be well distributed throughout the catalyst particles. The proposed mechanism explains the stabilizing influence on conversion and the suppression of cracking reactions by addition of the metallic hydrogenation function to the active acidic catalyst base. 

Residue Hydrocracking. The catalysts used for HCR should have dual functionality, cracking and hydrogenation (HYD) functions. The process scheme of a typical HCR fixed-bed system contains two reactors ... 

Historically, the isomerization catalysts have included amorphous siUca-aluminas, zeoHtes, and metal-loaded oxides. AH of the catalysts contain acidity, which isomerizes the xylenes and if strong enough can also crack the EB and xylenes to benzene and toluene. Dual functional catalysts additionally contain a metal that is capable of converting EB to xylenes. 

HC Unibon [Hydrocracking] A version of the hydrocracking process for simultaneously hydrogenating and cracking various liquid petroleum fractions to form branched-chain hydrocarbon mixtures of lower molecular weight. The catalyst is dual-functional, typically silica and alumina with a base metal, in a fixed bed. Developed by UOP. By 1988,46 licenses had been granted. Currently offered under the name Unicracking. 

DFCr systems appear to have the necessary metals tolerance to process residual oils and the abundant, cheaper, but heavily vanadium-contaminated, Venezuelan and Mexican crudes (1-4). Therefore, the dual function fluid cracking catalyst (DFCC) concept could lead to the generation of important catalysts for U.S. refineries should Middle East politics cause another sudden escalation in crude oil prices and availability. The concept is... 

Hydrocracking catalysts are dual functional, containing both hydrogenation and cracking sites. The best choice of catalyst for a specific situation requires a particular balance between these two functions. Table I shows some applications of hydrocracking and the characteristics of the families of catalysts that have evolved for accomplishing the indicated conversions. 

Acid-catalyzed cracking and platinum-catalyzed hydrogenolysis proceed simultaneously over dual-function catalysts. The distribution of the scission products is determined by the relative strengths of the acidic and metal-type catalytic components. 

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