Residuum hydroconversion

From the foregoing dicussion it is apparent that residuum hydroconversion processes can be influenced adversely by pore diffusion limitations. Increasing the catalyst porosity can alleviate the problem although increased porosity is usually accompanied by a decrease in total catalytic surface area. Decreasing the catalyst particle size would ultimately eliminate the problem. However, a different type of reaction system would be required since the conventional fixed bed would experience excessive pressure drops if very fine particles were used. A fluidized system using small particles does not suffer from this limitation. However, staging of the fluidized reaction system is required to minimize the harmful effects that backmixing can have on reaction efficiency and selectivity. 

The major goal of hydroconversion is the cracking of residua with desulfurization, metal removal, denitrogenation, and asphaltene conversion. The residuum hydroconversion process offers production of kerosene and gas oil, and production of feedstocks for hydrocracking, fluid catalytic cracking, and petrochemical applications. 

Residuum hydroconversion is a special case of hydrocracking. Compared to distillate hydrocracking, a significantly different catalyst is used, frequently low metal loading with Mo, with a special pore size distribution less subject to pore plugging by coke. More... 

Table 9-5 CANMET Hydroconversion of Cold Lake Vacuum Residuum... 

In the process (Figure 9-22), fresh vacuum residuum, microcatalyst, and hydrogen are fed to the hydroconversion reactor. Effluent is sent to a flash separation zone to recover hydrogen, gases, and liquid products, including naphtha, distillate, and gas oil. The liquid bottoms from the flash step is then fed to a vacuum distillation tower to obtain a 565°C (1050°F ) product oil and a 565°C + (1050°F+) bottoms fraction that contains unconverted feed, microcatalyst, and essentially all of the feed metals. 

Typical conditions used for the hydroconversion of residuum include ... 

---