Ni/MgO-Al_2O_3催化剂上高温焦油组分的催化转化

Catalytic Conversion of Tar Components in Hot Coke Oven Gas over Ni/MgO-Al_2O_3 Catalysts

采用分步浸渍法制备了MgO-Al2O3负载的Ni基催化剂,并运用N2吸附、X射线衍射(XRD)、透射电子显微镜(TEM)等手段进行表征.该催化剂用于甲苯或萘为焦油模拟化合物的高温焦炉煤气(COG)的常压加氢裂解反应,并考察了H2浓度、H2S对催化剂活性的影响.结果表明:催化剂还原后,表面形成均匀分散、直径为8-14nm的金属Ni纳米颗粒;在较低的水碳摩尔比(nH2O/nC=0.28)时,甲苯就能完全转化并选择性地加氢裂解形成CH4,测试的时间内(480min),催化剂没有明显的失活和积炭现象,显示出好的反应活性、稳定性和耐硫能力.制得的Ni/MgO-Al2O3催化剂有望应用于较低水含量(10%-15%(φ,体积分数))的高温焦炉煤气中焦油的直接转化.

NiO/MgO-Al2O3 catalysts with different Ni contents were prepared by a two-step impregnation method and characterized by X-ray diffraction （XRD）, Brunauer-Emmett-Teller （BET） and transmission electron microscopy （TEM）. Results showed that metallic Ni nanoparticles with diameters of 8-14 nm were formed and homogenously dispersed on the surface of the catalysts after reduction at 800℃. The catalysts were used for the catalytic conversion of toluene as a model tar compound in hot coke oven gas （COG） and showed excellent catalytic activity, stability and sulfur tolerance. Toluene could be fully converted and selectively hydrogenated to CI-L even using a low molar ratio of water to carbon （nH2O/nc=0.28） at 800℃ and under ambient pressure. The existence of H2O in the feed gas greatly enhanced the conversion of toluene and contributed to CH4 formation. Under similar conditions, naphthalene was converted into light fuel gases. Effects of H2 concentration and H2S in the feed gas were discussed. The Ni/MgO-Al2O3 catalyst was promising for the hydrocracking of tar compounds in hot coke oven gas with a low H20 content of 10%- 15% （φ, volume fraction）.