Study On Modified MoNi/Al₂O₃ Catalysts For The Hydrodenitrogenation Of Low-temperature Coal Tar

Coal tar is a kind of inevitable byproducts, which is produced in the carbonization process under high temperature. It is a pungent odor viscous liquid, with black or dark brown color. With the development of s coal chemical industry in China, the production of coal tar is increasing. Current research is focused on using the coal tar oil as supplementary energy. Because the composition and content in coal tar and crude diverge greatly, the purification process of catalysts is different.The incipient-wetness impregnation method was used in the research to synthetize a series of catalysts which used γ-Al2O3 and nano TiO2 as carrier and Mo and Ni as reactive metal. The effect of nano TiO2 modification and additives (P, citric acid) modification on HDN catalyst property was investigated. Addition of modification catalyst HDN property was investigated at different temperatures and different concentrations of raw material. The catalysts were analyzed and characterized by XRD, H2-TPR, NH3-TPD, Py-IR and TEM etc. techniques. The activity of HDN catalysts was tested at fixed bed micro-reactor with decalin solution contains quinoline and thiophene as raw material.The results are followed:(1) When the catalysts were modified by P, the amount of surface acid was improved. And the reducing components, stacking of MoS2 and the length of layer are increased. The comparison between catalyst modified by 2% P with non-modified catalyst indicated that the nitrogen removal rate for the catalyst modified by 2% P is 12% higher. (2) As the catalysts were modified by citric acid, the interaction between active constituent and supporter weakened. The dispersion of active constituent formed on the carrier surface increased the reducibility of active constituent. The highest nitrogen removal rate was obtained under the ratio of CA/Ni=0.5. (3) Since the supporters of the catalysts were modified by TiO2, total acids were reduced but the amount of B acid was increased. The highest nitrogen removal rate was achieved when the catalysts were modified by 5% TiO2. (4) After modification of catalyst by P and citric acid, the higher the temperature, the better the HDN results in a certain temperature range. For HDN property, the nitrogen removal rates of raw materials under the low concentration (<500ppm) were more than 99%.