| The conversion of methanol to light olefins (MTO) over commercial narrow pore Silicoaluminophophate SAPO-34, and pentasil type ZSM-5 and Silicalite S-115, was studied in a fixed bed tubular reation system. Nitrogen was used as carrier gas. Experiments were caried out at various temperatures, space velocities (WHSV) and methanol-to-nitrogen (wt) ratio to study their effects on catalyst activity, selectivity, product distribution and coke deposition. ZSM-5 and S-115 were modified by impregnation with various metal elements to investigate their effects on catalyst active life time and selectivity to lower olefins. At 400{dollar}spcirc{dollar}C and 4 hr{dollar}sp{lcub}-1{rcub}{dollar} WHSV SAPO-34 exhibited higher initial selectivity to lower olefins than both ZSM-5 and S-115 but also deactivated more rapidly ({dollar}La>Ag>Cu>Ca>Sr>Ga>Cd>In,{dollar} while for ZSM-5, the selectivity decreased in the order {dollar}rm In>Ag>Cu>Cd.{dollar} Optimum Ba-loading on S-115 for high olefin yield was found to be 5.2% by impregnation and 0.03% by ion-exchange. |
