Energy & Fuels 1995,9, 435-438
435
Explanation of Product Distribution of Hydrocracking Reaction of Aromatic Hydrocarbons with Nickel-Loaded Zeolites Based on CAMD Study on Interaction between Zeolites and Substrates Hisaji Matsui Research & Development Center, Osaka Gas Co. Ltd., 19-9, 6-Chome, Torishima, Konohana-ku, Osaka 554, Japan
Kenji Akagi, Satoru Murata, and Masakatsu Nomura" Department of Applied Chemistry, Faculty of Engineering, Osaka University, 2-1 Yamada-oka, Suita, Osaka 565, Japan Received October 3, 1994@
Simulation of diffusion phenomena of aromatic hydrocarbons in the channel of three different zeolites (ZSM-5, mordenite, and Y-type zeolites) was carried out by using a commercial CAMD (computer-aided molecular design) software. The diffusion phenomena of model aromatic hydrocarbons, such as benzene, naphthalene, phenanthrene, and pyrene, were found to depend greatly on molecular sizes of both the channel of these zeolites and model compounds. The relationship between such diffusion phenomena in the zeolites and product distribution of these aromatic hydrocarbons in hydrocracking reaction is briefly discussed.
Computer-aided molecular design (CAMD)technique has been extensively used in the area of protein engineering or drug design. Recent development of hardware and software of the computer makes this technique applicable for the larger systems such as ~ o a l , l -or~ catalytic s u p p ~ r t s . ~By ~ Jusing ~ this technique, Miyamot0 et al. studied fine structures and dynamics of H-ZSM-5 and Na-ZSM-5,1° and destruction of zeolites during a catalytic process.ll In a previous study, we reported the results of hydrocracking reaction of aromatic hydrocarbons including phenanthrene and pyrene using three different nickel-loaded zeolites such as ZSM-5, mordenite, and Y-type zeolites, this indicating that the product distribution reflects, to a great extent, the influence of pore size of the zeolite employed.12 In this paper, we report a CAMD study on the diffusion phenomena of aromatic hydrocarbons in the channel of the zeolites and discuss @Abstractpublished in Advance ACS Abstracts, April 15, 1995. (1)Nakamura, K.; Murata, S.; Nomura, M. Energy Fuels 1993,7 , 347 (2)Murata, S.;Nomura, M.; Nakamura, K.; Kumagai, H.; Sanada, Y.Energy Fuels 1993,7 , 469. (3)Dong, T.; Murata, S.; Miura, M.; Nomura, M.; Nakamura, K. Energy Fuels 1993,7 , 1123. (4)Takanohashi, T.; Iino, M.; Nakamura, K. Energy Fuels 1994,8, 295 -"I.
(5) Carlson, G. A. Energy Fuels 1992,6 , 771. (6)Faulon, J.-L.; Carlson, G. A,; Hatcher, P. G. Energy Fuels 1993,
7 , 1062. (7)Faulon, J.-L.; Hatcher, P. G.; Carlson, G. A,; Wenzel, K. A. Fuel Process. Technol. 1993,34, 277. ( 8 ) Faulon, J.-L.; Hatcher, P. G. Energy Fuels 1994,8,402. (9)Faulon, J.-L.; Mathews, J. P.; Carlson, G. A,; Hatcher, P. G. Energy Fuels 1994,8,408. (10)Miyamoto, A.; Kubo, M. J . Jpn. Pet. Inst. 1993,36, 282. (11)Oumi, Y.; Yamano, H.; Himei, H.; Katagiri, M.; Kumo, M.; Vetrivel, R.;Miyamoto, A. Shokubai 1994,73, 65. (12)Matsui, H.; Akagi, K.; Murata, S.; Nomura, M., unpublished results.
the relationship between diffusion ability of these substrates in the channel of zeolites and product distribution in their hydrocracking reaction. All the molecular dynamics calculations were carried out on a Titan 750V gi-aphicworkstation (Kubota Pacific Computer Inc.) using a commercial CAMD software, Polygraf (Ver. 3.1, Simulation Technology Inc.). In the simulation of diffusibn phenomena of the model molecules in the channel'of the zeolites, impulse dynamics methods were used. The following parameters were employed here: initial velocity of the model molecules 0.02 k f s , time for simulation 3000 steps (3.0 ps), and temperature of simulation 300 K. Under these conditions, some initial forces were given t o the model molecules (such as polyaromatic hydrocarbons) while zeolites' channels were located at fured position: the forces make the model move toward zeolites' channel at uniform velocity, where the distance of model's movement is 60 A within 3.0 ps, if repulsive forces between channel of zeolite and the model do not work. Figure 1 shows the channel structures of ZSM-5, mordenite, and Y-type zeolites, which were constructed on the basis of their single crystalline X-ray diffraction data provided by Simulation Technology Inc. The pore of ZSM-5 type zeolite has an oxygen 10-membered ring structure, while each pore of mordenite and Y-type zeolite has an oxygeml2-membered ring structure. Pore size was reported to be 5.4 A for ZSM-5, 7.0 x 6.7 A for mordenite, and 7.1 A for Y-type zeolite, pore size of ZSM-5 being the smallest and pore of mordenite being not circular. Generally, the siliconelaluminum atomic ratio was reported to be
