Attrition-resistant Ni[sbnd]Mg/SiO2[sbnd]Al2O3 catalysts with different silica sources for fluidized bed syngas methanation

Abstract

Attrition-resistant NiMg/SiO2Al2O3 catalysts for fluidized bed syngas methanation were prepared by combining co-precipitation and spray granulation using different silica sources including acidic silica sol (SS), sodium silicate (NS) and tetraethyl orthosilicate (TEOS). Air-jet attrition tests showed that the attrition strength of the resulting catalysts followed an order of C-10TEOS > C-33SS > C-10NS > C-10SS, where C-10TEOS, as an example, refers to the catalyst with 10 wt.% silica using TEOS as its silica source. Characterizations show that the porosity and skeletal structure have strong correlation with catalyst attrition strength. Simultaneous hydrolysis of TEOS and co-precipitation caused C-10TEOS to have dense and continuous skeletal structure to have the high strength of its NiMg/SiO2Al2O3 precursor particles and thus the improved attrition resistance of sprayed catalyst. Silica sol filled in the voids among precursor particles resulted in a compact framework in C-33SS but its NiMg/Al2O3 precursor had weak attrition resistance. Atmospheric syngas methanation over these catalysts at an SV of 600 NL g−1 h−1 in a fixed bed reactor clarified an activity order of C-10TEOS > C-10NS ≈ C-33SS. The TEOS also enabled highly dispersed metallic Ni and many surface active sites to facilitate the methanation activity and stability of this catalyst.