Nickel has been developed with various promoters and carriers for decomposing tar and tar models [7-27].

Zhang [13] investigated tar catalytic destruction in a tar conversion system consisting of a guard bed and catalytic reactor. Three Ni based catalysts (ICI46-1, Z409 and RZ409) were proven to be effective in eliminating heavy tars (99% destruction efficiency). The experimental results demonstrated that space velocity (1500 -6000) had little effect on gas compositions, while increasing temperature boosted hydrogen yield and reduced light hydrocarbons (CH4 and C2H4) formation, which suggested that tar decomposition was controlled by chemical kinetics.

Furusawa et al. [14] reported that 10 wt% Ni/MgO (873 K) catalyst showed the best performance. Nickel supported on silica was active for tar catalyst cracking methane at relatively low temperature (823 K) was described by Zhang [9].

Srinakruang et al.[15,16] has developed Ni/Dolomite as highly efficient sulphur and coking resistance catalyst, and reported that calcining at 500 oC exhibited the most effective catalyst among Ni/SiO2 and Ni/АЬОэ; the poisoning effect was enhanced by increasing the reaction temperature and steam/C ratio; higher activity, durability and coking resistance.

Sato et al. [17], has developed Ni-WO3/MgO-CaO catalyst for naphthalene and toluene reforming. The results exhibited a better resistance to sulfur and coking catalyst; tar reforming to better than 90% and 100 h steady tar reforming operation (in H2S) at 800­850 oC.

Dou et al. [18] compared five catalysts on tar removal from fuel gases in a fixed-bed reactor. The Y-zeolite and NiMo catalysts were found to be the most effective about 100% tar removal can be achieved at 550 oC. It was also observed that process variables like temperature and space velocity had very significant effect on tar removal.

Baker [19] also mentioned the phenomena in their experiments. In order to overcome the shortcoming of the commercial Ni-based catalyst, many Ni-based catalysts were developed.

Miyazawa et al. [20] has prepared Ni (Ni/AhO3, Ni/ZrO2, Ni/TiO2, Ni/CeO2 and Ni/MgO) catalyst to reformed tar in the partial oxidation (POT) and steam introduction. Results have been achieved: the order of the performance at 823 K was as follows: Ni/AhO3 > Ni/ZrO2 > Ni/TiO2 > Ni/CeO2 > Ni/MgO > no catalyst; Ni/CeO2 showed smaller amount of coke than other catalysts; in the POT, much higher tar conversion and lower coke yield were obtained than that in SRT using fixed bed reactor.