Changing the balance of the MTO reaction dual-cycle mechanism: Reactions over ZSM-5 with varying contact times

The methanol to olefins （MTO） reaction was performed over ZSM‐5 zeolite at 300℃ under various methanol weight hourly space velocity （WHSV） values. During these trials, the catalytic perfor‐mance was assessed, in addition to the formation and function of organic compounds retained in the zeolite. Analysis of reaction effluents and confined organics demonstrated a dual‐cycle reaction mechanism when employing ZSM‐5. The extent of the hydrogen transfer reaction, a secondary reac‐tion in the MTO process, varied as the catalyst‐methanol contact time was changed. In addition, 12C/13C‐methanol switch experiments indicated a relationship between the dual‐cycle mechanism and the extent of the hydrogen transfer reaction. Reactions employing a low methanol WHSV in conjunction with a long contact time favored the hydrogen transfer reaction to give alkene products and promoted the generation and accumulation of retained organic species, such as aromatics and methylcyclopentadienes, which enhance the aromatic cycle. When using higher WHSV values, the reduced contact times lessened the extent of the hydrogen transfer reaction and limited the genera‐tion of methylcyclopentadienes and aromatic species. This suppressed the aromatic cycle, such that the alkene cycle became the dominant route during the MTO reaction.

Conversion of methanol to propylene over SAPO-14:Reaction mechanism and deactivation

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.

Online Healthcare Community Interaction Dynamics

With the increasing dilemma of the rapid global demand for healthcare services(often in the presence of limited resources),how to creatively allocate and use healthcare resources across a widespread population has become a salient issue.Online healthcare communities(OHCs)are regarded as a potential ICT-based partial solution.In contrast to traditional healthcare,online doctor-patient interaction is unlimited in terms of time and space limitations while an OHC is exposed to the whole community.These characteristics are key to achieving synergistic doctor-patient interaction and community development in the longer term.In order to explore the nature of doctor-patient interaction dynamics in an OHC,we systematically investigate doctor-patient interaction dynamics from the dual perspectives of doctor and patient.Our doctor-patient interaction dual-cycle model has been built based on six doctor-patient interaction processes(i.e.,searching,choosing,knowledge sharing,providing,receiving and balancing).According to our dual-cycle model,four key managerial issues in OHC(information asymmetry,incentive mechanisms,service delivery processes and interaction mechanisms)have been identified as examples.Discussion and directions for future research,with challenges as well as opportunities,have been elaborated.A broad view with fruitful research potential is ensured and new theories and methods ultimately provide implications for effectively and efficiently allocating scarce healthcare resources to a broader population.

Insight into the Dual Cycle Mechanism of Methanol-to-OIefins Reaction over SAPO-34 Molecular Sieve by Isotopic Tracer Studies

Methanol-to-olefins(MTO)reaction is one of the important non-petroleum routes to produce light olefinsover acidic molecular sieves.In this study,the complete reaction course of MTO on SAPO-34 molecular sieve with retained organics evolution from induction period to deactivation period was investigated systematically at different weight hourly space velocities(WHSV)of methanol.By the aid of 12C/3C-methanol isotopic switch experiment,the dual cycle mechanism involving aromatics-based cycle and alkenes-based cycle was evaluated during the whole reac-tion process.The detailed reaction route varied with the evolution of the retained organics in the catalyst at different reaction stages.The aromatics-based cycle and alkenes-based cycle alternately dominate the reaction process.In the efficient reaction period,aromatics-based cvcle is the main reaction mechanism,while in the induction and deactiva-tion periods.the contribution of alkenes-based cvcle mechanism will become more important.