Methanol to olefins(MTO)reaction as an important non-oil route to produce light olefins has been industrialized,and received over 80% ethylene plus propylene selectivity.However,to achieve high single ethylene or prop...Methanol to olefins(MTO)reaction as an important non-oil route to produce light olefins has been industrialized,and received over 80% ethylene plus propylene selectivity.However,to achieve high single ethylene or propylene selectivity towards the fluctuated market demand is still full of challenge.Small-pore SAPO-14 molecular sieve is a rare MTO catalyst exhibiting extra-high propylene selectivity.It provides us a valuable clue for further understanding of the relationship between molecular sieve structure and MTO catalytic performance.In this work,a seconds-level sampling fixed-bed reactor was used to capture real-time product distributions,which help to achieve more selectivity data in response to very short catalytic life of SAPO-14.Changes in product distribution,especially during the low activity stage,reflect valuable information on the reaction pathway.Combined with in situ diffuse reflectance infrared Fourier-transform spectroscopy,in situ ultraviolet Raman measurements and ^(12)C/^(13)C isotopic switch experiments,a reaction pathway evolution from dual cycle to olefins-based cycle dominant was revealed.In addition,the deactivation behaviors of SAPO-14 were also investigated,which revealed that polymethylbenzenes have been the deactivated species in such a situation.This work provides helpful hints on the development of characteristic methanol to propylene(MTP)catalysts.展开更多
文摘Methanol to olefins(MTO)reaction as an important non-oil route to produce light olefins has been industrialized,and received over 80% ethylene plus propylene selectivity.However,to achieve high single ethylene or propylene selectivity towards the fluctuated market demand is still full of challenge.Small-pore SAPO-14 molecular sieve is a rare MTO catalyst exhibiting extra-high propylene selectivity.It provides us a valuable clue for further understanding of the relationship between molecular sieve structure and MTO catalytic performance.In this work,a seconds-level sampling fixed-bed reactor was used to capture real-time product distributions,which help to achieve more selectivity data in response to very short catalytic life of SAPO-14.Changes in product distribution,especially during the low activity stage,reflect valuable information on the reaction pathway.Combined with in situ diffuse reflectance infrared Fourier-transform spectroscopy,in situ ultraviolet Raman measurements and ^(12)C/^(13)C isotopic switch experiments,a reaction pathway evolution from dual cycle to olefins-based cycle dominant was revealed.In addition,the deactivation behaviors of SAPO-14 were also investigated,which revealed that polymethylbenzenes have been the deactivated species in such a situation.This work provides helpful hints on the development of characteristic methanol to propylene(MTP)catalysts.
