氨蒸发法制备用于甲烷干重整反应的高活性Ni催化剂

Preparation of highly-active Ni catalysts by ammonia evaporation method for dry reforming of methane

采用氨蒸发法制备了以KIT-6介孔二氧化硅负载的Ni催化剂,并将其应用于甲烷干重整反应。通过调整氨水浓度并与浸渍法对比,考察了制备方法、工艺参数对催化剂稳定性和抗积碳性能的影响。经ICP-OES、XRD、N_(2)等温吸脱附、TEM、H_(2)-TPR、Raman、TGA/DSC等表征分析发现,使用氨蒸发法能够形成层状硅酸镍,促进Ni高度分散在介孔孔道内并有效防止积碳;采用浓度为28%和20%的氨水制备的催化剂样品具有优异的催化活性和抗积碳能力,在700℃时的甲烷干重整反应中对CH_(4)和CO_(2)的转化率分别约为85%和91%,几乎没有积碳;当氨水浓度降低至10%时,形成过量的层状硅酸镍以致孔结构破坏,反应后出现严重积碳;采用传统浸渍法导致Ni颗粒大量团聚堆积在载体外表面,同样出现严重积碳。

Ammonia evaporation method was employed to prepare Ni catalysts loaded on KIT-6 mesoporous silica for the dry reforming of methane.The influence of preparation method and process parameters on the stability and coke resistance of the catalysts were investigated,by comparing the catalysts prepared with different ammonia concentration as well as that with impregnation method.Characterization and analysis including ICP-OES,XRD,N_(2) isothermal adsorption-desorption,TEM,H_(2)-TPR,Raman and TGA/DSC were carried out.It was found that Ni phyllosilicate was formed by using ammonia evaporation method,which promoted the high dispersion of Ni in the mesopores and effectively prevented carbon deposition.Catalysts prepared with 28% and 20% ammonia presented excellent catalytic activity and coke resistance.The conversion of CH_(4) and CO_(2) in the methane dry reforming reaction at 700 ℃ was ca.85% and ca.91%,respectively,with almost no carbon deposition.When the ammonia concentration was reduced to 10%,the formation of excessive Ni phyllosilicate destroyed the mesoporous structure,leading to severe carbon deposition.The same situation happened to the catalyst prepared by impregnation method owing to the agglomeration of Ni particles on the external surface of the support.