Direct conversion of syngas to light olefins (C2–C3) over a tandem catalyst CrZn–SAPO-34: Tailoring activity and stability by varying the Cr/Zn ratio and calcination temperature

•CrZn–SAPO-34 is able to convert syngas to C2–C3 hydrocarbons with high olefin/paraffin ratio and low methane yield.•Catalytic performance exhibited a trade-off between activity and stability in olefin yield.•Tuning Cr/Zn ratio is able to improve olefin production with compromise in the overall olefin selectivity.•The nonstoichiometric and inversed ZnCr2O4 spinel phase is the active phase for CO hydrogenation.•Decay in olefin production over time correlates with the amount of segregated ZnO on the catalyst.