球磨条件对浆态床CO甲烷化Ni-Al2O3催化剂性能的影响

Influence of milling conditions on performance of Ni-Al_2O_3 catalyst for CO methanation in slurry-bed reactor

利用行星式球磨机并采用机械化学法制备了系列Ni-Al_2O_3催化剂,考察了球配比[大小质量比(1∶0、0∶1、1∶1)]、球磨时间(30、50、60、70、90 min)和球料比(1∶1、2∶1、3∶1)对Ni-Al_2O_3催化剂晶相结构、孔道结构、粒径分布和浆态床CO甲烷化性能的影响。XRD分析结果显示,具有NiCO_3·6H_2O物相的活性组分Ni前体焙烧后均转变成无定型NiO,高度分散在Al_2O_3载体中。BET和PSD分析表明,大球球磨制备的CT-10比表面积较大,近300 m^2/g;平均粒径较小,仅为240 nm。评价实验显示,全采用大球球磨制备的CT-10试样,CO转化率、CH_4选择性和CH_4收率均最高,分别为72.01%、49.08%和35.57%。经对球磨时间(60 min)和球、料质量比(2∶1)优化后,所得CT1-60-21试样的CH_4选择性和收率分别提高至87%和75%。

A series of Ni-Al2O3 catalysts are prepared by the mechanochemical method and planetary ball mill.The effects of the ratio of size to mass of ball,milling time and the ratio of ball to material on the crystal structure,pore structure and particle size distribution of Ni-Al2O3 catalyst,and its catalytic performance for CO methanation in slurry bed are investigated.The analysis results by XRD show that after calcinations,the active component Ni precursor with Ni CO3·6 H2 O phase is entirely transformed into amorphous Ni O that is highly dispersed on the surface of Al2O3 carrier.BET and PSD analysis demonstrates that the CT-10 catalyst prepared by big-ball ball mill has large specific surface,up to300 m^2·g^（-1）,and its average particle size is only as small as 240 nm.The evaluation test shows that the CO conversion,CH4 selectivity and CH4 yield for CT-10 samples prepared by big-ball ball mill are 72. 01%,49. 08% and 35. 57%respectively,higher than other samples. Through optimization,the CT1-60-21 catalyst sample prepared under conditions that the milling time is 60 min and the ratio of ball to material is 2 ∶1 can make the selectivity and yield of CH4 increase to 87% and 75%,respectively.