Initiation Effect of Local Heating in Hydro-Thermal Cracking of Resids
Fuels 》14 (6), pp.1331. 發表
Jie Chang, Noritatsu Tsubaki* and Kaoru Fujimoto
Department of Applied Chemistry, School of Engineering, The University of Tokyo,
Masao Yoshimoto Petroleum Energy Center of Japan, KSP R&D Build. D-12-1237, 3-2-1,
Sakado, Takatsu-ku, Kawasaki, Kanagawa, 213-0012, Japan
The upgrading of heavy oils is attracting growing interest as a means of producing premium quality transportation fuels and other middle distillate products. Hydro-thermal cracking is one of the promising processes to obtain maximum middle distillate (kerosene + gas oil) from residual oils. This process and its reaction mechanism have been described elsewhere.1,2 Hydro-thermal cracking of resid, which is the combination of thermal cracking and catalytic hydrogenation, is composed of the following elementary steps: (1) formation of free radicals proceeding via cleavage of C-C or C-X (heteroatom) bond;3,4 (2) production of middle distillate proceeding via β-scission of free radicals;5 (3) termination of free radical reactions and saturation of C=C bonds proceeding via catalytic hydrogenation.
High reaction temperature can simply accelerate the conversion of resid, but the selectivities of gaseous hydrocarbons and coke will be increased tremendously. We have demonstrated that adding some initiators, such as element sulfur and di- tert-butyl-peroxide, which might produce free radicals even at lower temperature, promoted the conversion of resids and increased the yield of distillate.2,6 This paper presents our results on another initiation method, local heating by inside filament. The in situ measurement of free radical concentration during hydro-thermal cracking of Kuwait AR was carried out by ESR and reported elsewhere.7 The in situ spin concentration (at g = 2.0035, which shows the signal of hydrocarbon free radical) was detected by using a quartz tube containing Kuwait AR at 2.0 MPa of hydrogen pressure and heating it at 5 K/min. The results showed that the spin concentration of free radicals increased with the increasing temperature probably due to the cleavage of C-C and C-S bond and leveled off at about 480 K, then it slightly decreased, and again increased very quickly at above 680 K. According to this trend, an inside filament was employed to realize higher-temperature zone at some limited space inside the reactor to initiate the formation of free radicals at lower reaction temperature. The experiment results proved that local heating effectively promoted the conversion of Canadian oil sand bitumen and Arabian VR.
1、Effect of Addition of K to Ni/SiO2 and Ni/Al2O3 Catalysts on Hydrothermal Cracking of Bitumen
2、Hydrothermal cracking of Residual Oil
3、The Promotional Effect of Initiators in Hydro-thermal Cracking of Resids
5、Enhancement effect of free radical initiator on hydro-thermal cracking of heavy oil and model compound