Research Of Ni-based Catalysts And Its Supports For Ammonia Decomposition

The paper studied the effects of supports and promoters of Ni-based catalysts for ammonia decomposition to find the methods and principles to decrease the reaction temperature of ammonia decomposition. Then the effect of S element,which is poison for Ni-based catalysts,was studied.According to the absorptivity of water,the capability to resist the acide erosion and the intensity,the Kaolin was tested to identify whether it can used as the support for ammonia decomposition or not. Then the major factors during preparing process were fixed. They were calcined temperature and quality ratio of Kaolin and MgO. The quality ratio of Kaolin and MgO mainly influenced the capability of supports to resist the acide erosion and calcined temperature mainly influenced the absorptivity of water and the intensity of supports. The activity data of Ni-based catalysts respectively loaded by Kaolin and MgO supports indicated that both of supports possessed the comparative capability for ammonia decomposition. When temperature was not below 800℃,ammonia decompose thoroughly. Kaolin support was a good one to prepare Ni-based catalysts for ammonia decomposition.The promoters selected the oxide of Fe,Cr,Mo element and the catalysts were tested by XRD and TPR to study the changes. The activity data of ammonia decomposition indicated that all the promoters could improve the activity of Ni-based catalysts and the effect of Mo element was the best. When using Mo element as promoter for Ni-based catalyst,ammonia could decompose thoroughly above 670℃. The results of TPR indicated that all the promoters made the reductive temperature of Ni-based catalysts low and improved their activity. But the reductive temperature of Ni-based catalyst was not better rather than the lower. Between 500℃and 750℃might be reasonable. At the temperature,ammonia could decompose more easily and quickly.When the Ni-based catalysts were poisoned by S element,their activity for ammonia decomposition were remarkably decreased. The results of XRD indicated that the birth of sulfide might be the reason.