INVESTIGATION OF THE EFFECT OF SELECTED TRANSITION METAL SALTS ON THE PYROLYSIS OF HUADIAN OIL SHALE, CHINA

In this paper, the effect of several transition metal salts such as Fe[Cl.sub.2]*[4H.sub.2]O, Co[Cl.sub.2]*[6H.sub.2]O, Ni[Cl.sub.2]*[6H.sub.2]O and Zn[Cl.sub.2] on oil shale pyrolysis was investigated, based on thermal decomposition characteristics and product yields and compositions. The salts were added individually to Chinese Huadian oil shale by physical mixing. Pyrolysis experiments of oil shale with and without transition metal salts were performed in a thermogravimetric analyzer and a fixed bed reactor. Thermogravimetric analysis (TGA) suggested that Co[Cl.sub.2]-[6H.sub.2]O and Ni[Cl.sub.2]-[6H.sub.2]O could promote oil shale pyrolysis, leading to a greater thermogravimetric mass loss than raw oil shale. By contrast, Fe[Cl.sub.2]*[4H.sub.2]O and Zn[Cl.sub.2] had only a slight effect on the decomposition behavior of oil shale. The results of fixed bed pyrolysis experiments showed that all metal salts enhanced the secondary cracking of shale oil, which decreased the oil yield and increased the pyrolytic gas yield. The metal salts could also catalyze the aromatization of aliphatic hydrocarbons to yield aromatic hydrocarbons. The catalytic activity of the studied salts decreased in the order Ni[Cl.sub.2]*[6H.sub.2]O > Co[Cl.sub.2]*[6H.sub.2]O > Zn[Cl.sub.2] > Fe[Cl.sub.2]*[4H.sub.2]O. Keywords: oil shale pyrolysis, transition metal salts, catalytic effect, shale oil cracking, aliphatic hydrocarbon aromatization.