Influence of different preparation conditions on catalytic activity of AG/γ-Al2O3 for hydrogenation of coal slime pyrolysis

This paper,introducing variable conditional factors with ag/al 2o3 as catalyst,selects five variables to investigate the influences of experimental conditions on ag/al2o3 catalytic activity and define the optimal pr°cess conditions. these variables include ag loading amount,calcinations temperature,calcinations time,reduction temperature,reduction time. x ray diffraction (xrd),hydrogen temperature-programmed reduction (tpr),x ray photoelectron spectrum (xps) and scanning electron microscopy (sem) were utilized to characterize the catalytic activity of ag/γ-al2o3,active center structure and state and those of carrier were emphatically studied,in the meantime the effects of active center and carrier on catalytic activity are studied. the results showed that: (1) in the range of 600 °c̃900 °c,the catalytic activity of ag/γ-al2o3 with different loading showed little difference when changing loading amount,in the range of 900 °c̃1100 °c,when the loading was 5%,the catalytic activity was very high; from the xrd and sem characterizations,when the loading was 5%,it showed strong intensity diffraction peak of ag crystal,crystal ag is the most important activity center to promote hydrogen yield. (2) the catalytic activity of ag/γ-al2o3 at 450 °c was considerably higher than that at 400 °c and 500 °c. by bet,xrd and sem characterization,it can be seen,the diffraction peaks intensity of ag crystal at 450 °c is higher and sharper than that at 400 °c and 500 °c and with the increase of calcinations temperature,the specific surface area of catalysts also increased. (3) in the range of 600 °c ̃ 1000 °c,the effects of calcinations time can be negligible,while,with temperature higher than 1000.c,4-hour-calcinations-time catalyst exhibits a more noticeable catalytic activity than 3-hour and 5-hour catalyst do; from the xrd spectrogram,we can see that three kinds of catalysts all showed diffraction peaks of ag and the diffraction peaks intensity of elemental ag of the catalysts prepared at the calcination time of 4hour was higher and sharper than that prepared at 3hou and 5hour. (4) when reduction temperature was 450 °c,the catalyst showed excellent activity,the catalytic activity of ag/γ-al2o3 was decreased after 1000 °c when the reduction temperature at 400 °c and 500 °c; (5) the reduction time had very little influence on the catalytic activity of catalyst. in the range of 600̃1100 °c,the catalytic activity of reducion time of 3 hour and 4 hour was the most significant,and when reduction time was 5 hour,the catalytic activity significantly reduced after 1000 °c.