催化剂对褐煤焦孔隙结构和表面形态的影响

在固定床反应器中对添加了碱金属K、碱土金属Ca、过渡金属Ni和Fe的褐煤进行制焦，采用N2等温吸附法测量各煤焦孔隙结构的表征参数，从而研究催化剂对煤焦的孔隙结构和气化反应性的影响。同时利用扫描电子显微镜分析煤焦表面形态的变化。测试结果表明，原煤焦主要含中、微孔；相对于原煤焦，添加Ca、Ni和Fe后煤焦的孔隙结构向中大孔发展，微孔比表面积减小，中大孔比表面积增大；而K-char的微孔和中大孔比表面积均大幅度减小。原煤焦以及添加Ni和Fe后所制成的焦均具有不规则粗糙表面和直管壁结构2种表面形态。当催化剂添加量达10%时，Ca-char和K-char从具有与原煤焦相同的表面形态发展为仅有粗糙表面形态。K-char和Ca-char的气化反应性随催化剂添加量的增加而增强，但K-char的比表面积随催化剂添加量的增加而减小，Ca-char的比表面积随催化剂添加量的增加先减小后增大。

Effects of Catalysts on the Pore Structure and Morphology of a Lignite Char

The lignite samples loaded with K, Ca, Ni and Fe were devolatilized in a fixed-bed reactor to prepare the corresponding chars which were measured by nitrogen adsorption to obtain the parameters of pore structure, and the effects of catalysts on the pore structure change and steam gasification reactivity were analyzed. The morphology of the chars and the catalyst dispersion were analyzed by a scanning electron microscope (SEM). Most of the pores of chars resulting from lignite loaded with Ca, Fe and Ni are mesopores and macropores, but the raw char mainly consists of micropores and mesopores. The micropore area and external surface area of chars resulting from lignite loaded with Ca, Fe and Ni become smaller and larger than that of the raw char respectively, but the micropore area and external surface area of K-char are both significantly smaller than that of the raw char. The SEM images of chars show that porous structure with rough surface and structure with longitudinal tube walls coexist in raw char, Ni-char and Fe-char, but in the case of K-char and Ca-char, only porous structure with rough surface is observed when the catalyst loading is increased to 10%. The reactivities of K-char and Ca-char increase with catalyst loadings, but the surface area of K-char decreases evidently with catalyst loading and the surface area of Ca-char decreases first and then increases with catalyst loading.