Fig. 3: Catalytic performances over naphthalene-based SAPO-34 zeolites in MTO reaction.

a ZEOS and b ZEOL zeolites were used to implement the strategy of selective transformation of coke to naphthalene. MTO reactions were first performed on calcinated SAPO-34 zeolites, the peak selectivity of ethylene and product distribution under completed conversion of methanol at 124 min for ZEOS sample (abbreviated as ZEOS-124 min) or at 18 min for ZEOL sample (abbreviated as ZEOL-18 min) are shown in the first bar chart. When the methanol conversion decreased to ~80%, the product distribution is shown in the second bar (samples named as ZEOS-Coked and ZEOL-Coked). The initial product distributions of MTO reaction at ~1.5 min are shown in the followed bar charts over ZEOS-Coked and ZEOL-Coked samples treated by nitrogen at 953 K for 40 min (samples aliased as Coked@N₂) or steam cracking at 953 K for different times (samples aliased as Coked@H₂O-xxmin series). MTO reaction condition: T = 723 K, weight hour space velocity (WHSV) = 6.6 g_MeOH g_cat. h⁻¹. Steam cracking condition: T = 953 K, WHSV = 2.6 g_Steam g_cat. h⁻¹. c MTO reaction performance over the CAT-Coked@H₂O-20 min sample in the fluidized bed rector. MTO reaction condition: T = 723 K, WHSV = 2 g_MeOH g_cat. h⁻¹. Steam cracking condition: T = 953 K, WHSV = 3 g_Steam g_cat. h⁻¹. d Gas composition during steam cracking of CAT-Coked sample at T = 953 K and WHSV = 3 g_Steam g_cat. h⁻¹.