Hydrocracking conditions, thermal

McDaniel and Maher (159-161) were the first to report that upon thermal treatment of NH4-Y, under a particular set of conditions, thermal stability of the zeolite is considerably increased. The product retains crystallinity at temperatures in excess of 1000°C, while the decomposition of the sodium form of the zeolite takes place at ca. 800°C. This process is known as ultrastabilization. Ultrastable zeolite Y is very well suited as a catalyst for hydrocracking reactions—much more so than the as-prepared zeolite, which is too acidic and has insufficient thermal stability. 

Cracking is effected by one of three general methods thermal cracking, catalytic cracking, or hydrocracking. Each process has its own characteristics concerning operating conditions and product compositions. 

Recent design improvements with respect to yields, thermal efficiency, feed stock flexibility, and environmental protection are discussed. Also, it is shown that heavy feeds (such as hydrocracker residues) are good feed stocks for olefin production if they are cracked at the proper conditions. Furthermore, the economic application of design improvements to both the radiant and the convection sections in existing furnaces is shown. 

In contrast to the SRC-II Process, where coal dissolution and coal and solvent hydrocracking are achieved non-selectively in a single unit under largely non-optimal thermal conditions, the TSL... 

Thermal and catalytic hydrocracking reactions have been reported to occur in cascade (Yang et al, 2011), that is, the vacuum residue is hydrocracked to form vacuum gas oil the vacuum gas oil hydrocracks to produce middle distillates, and so forth. Depending on the reaction conditions, occurrence of some path reactions can be more difficult, or they could not even be present. 

The thermal hydrocracking (noncatalytic) was found to occur to a great extent even at moderate operating conditions, which implies that it must be considered in the evaluation of the performance of catalytic processes. 

Chapter 6 deals with thermal hydroprocessing. The effect of different reaction conditions on the extent of noncatalytic hydrodesulfurization, hydrodemetallization, and hydrocracking is examined in detail. 

---