UltraCat process

It has been ten years since Amoco announced the UltraCat process O) for SOx control in FCC units. In those ten years, as well as in the years previous to the announcement, much work was done to develop catalysts that would control SOx emissions. The evidence is the 80 or more U.S. patents that have issued in that time to Amoco and others. One of the first patents issued was to Amoco in 1974 ( ) for the addition of magnesia and other group IIA oxides to cracking catalyst. This paper reviews the SOx catalyst developments and emphasizes the work done at Amoco to identify the active materials, explain the deactivation mechanism and, finally, to make a side-by-side comparison of various catalytic systems that are being pursued commercially today. 

The UltraCat Process. The UltraCat process for SOx control entails oxidative capture by a metal oxide, MO, of SO2 from the burning of sulfur in coke on the regenerator side of the ECU,... 

Selection of Oxides. At Amoco, previous studies in the literature on SO2 removal from flue gas have been used to guide the selection of oxides for the UltraCat process but they have been of limited direct usefulness. This was true because of the peculiar requirements of the UltraCat process of high adsorption temperature, low regeneration temperature, and non-interference with the cracking reactions. The previous literature studies generally assumed that SO2 would be adsorbed at temperatures close to a stack gas temperature of 600 E, and desorb at either the same temperature or higher. The conditions of these studies was set. 

The early work of Bienstock ( ) at 625°F showed manganese, copper and cobalt oxides to be active. But these materials have not been used for the UltraCat Process probably because of the adverse effect on the cracking reactions. 

In a theoretical study, Lowell et al. W selected oxides from thermodynamic considerations for a process in which SO2 was adsorbed at temperatures greater than 100 C and desorbed by decomposition of the sulfate or sulfite formed, at temperatures below 750 C. Under these constraints, all of 47 oxides considered had potential for adsorption but only 16 had low enough decomposition temperatures to make a process economical. Intuitively, sulfate decomposition temperature should correlate loosely with reducibility of sulfates, so it is interesting that many of the 16 oxides chosen by Lowell, which included cerium and aluminum, have been shown to be useful in the UltraCat process. 

Platinum. Other materials are effective promotors for the oxidative adsorption of SO2. Figure 6, for instance, demonstrates the effect of platinum which is the best promotor and the earliest one used for the UltraCat process (31). The figure, which compares SO2 removal curves for alumina alone and with 2 and 100 ppm Pt at 1200, 1300 and 1400 F, indicates that alumina promoted with platinum at both levels is more efficient for removing SO2 than pure alumina. The catalytic effect of platinum, not unexpectedly, becomes less pronounced as the temperature is increased as can be seen by inspecting the curves and also by comparing the percentage of SO2 removed after 100 minutes as shown on Table IV. 

The thermodynamic data shown in Figure 21 indicate, post factum, how magnesia and alumina fit the requirements for the UltraCat process. The figure shows values for standard AG for reduction of the sulfate with hydrogen at 980°F to make SO2 for... 

An appropriate material for the UltraCat process should have favorable thermodynamics for both SO2 release and capture. The most favored elements are designated in the boxed area on Figure 21 and include alumina and magnesia. Berylium is also included, but the decomposition temperature of berylium sulfate, 1000-1100°F, indicates that it is probably not suitable, even if it were not hazardous. 

Ultracat A version of the FCC process, developed by Standard Oil of Indiana in the 1970s. 

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