Catalytic Co-Cracking Of High Olefins With Methanol To Produce Light Olefins

In the process of coal indirect liquefaction and catalytic cracking,light distillate with high olefin content can be produced.These distillates are usually converted into fuel gasoline by further deep hydrogenation,which has high cost and low efficiency.In this paper,the catalytic co-cracking of distillate and methanol over ZSM-5 catalyst could convert high carbon olefins content in distillate into light olefins,which reduced the olefin content of oil and obtained high value-added low-carbon olefin products.The catalytic co-cracking of distillate and methanol over ZSM-5 catalyst not only made use of high carbon olefins in light distillate to generate light olefins,but also thermally coupled endothermic olefins cracking and exothermic methanol conversion to achieve efficient use of raw materials and energy.In this paper,the reaction network and reaction kinetics of C₂-C₈ olefins and methanol co-cracking process was studied.The catalytic cracking and co-cracking properties of high carbon olefins with different structure such as normal olefins,iso-olefins and cycloolefins were compared to expand the range of raw material for light olefins production.The feasibility of light distillate and methanol co-cracking to produce low-carbon olefins was demonstrated,and the distribution of co-cracking products was predicted based on the kinetic model.The research of this thesis mainly includes:1)The catalytic cracking reaction of linear a-olefin was investigated on a fix-bed reactor,and the main reaction pathways for the interconversion of C₂-C₈ olefins were molecule cracking and oligomerization-cracking.The influence of reaction conditions and structure was studied,which indicated that the olefin isomers had little impact on the catalytic cracking results.The aromatization was main reaction pathway for catalytic cracking of cycloolefins over ZSM-5 zeolite catalyst,and catalytic cracking rate was much lower than normal linear a-olefin with same carbon number.Light distillate was rich in C₆-C₈ olefins,which could be converted into high-quality low-carbon olefins under mild conditions,while alkanes were inertial.2)The reaction of co-cracking of linear a-olefins with methanol was studied on fixed bed reactor,and the main reactions network was obtained.The results showed that methylation was dominant for co-cracking of C₂-C₆ olefins and methanol at low space time,the oligomerization-cracking rate grew with the increase of space time,while molecule cracking was main reaction for C₇-C₈ olefins.In addition,the co-cracking of high-carbon olefins were compared and the results showed the isomers had little impact on co-cracking of olefins and methanol.Light distillate was rich in high-carbon linear α-olefins,which were converted into light olefin completely（C₃-C₅ olefins accounting for 71wt%in product）,while the alkanes were inertial.3)According to the experimental data obtained,a comprehensive catalytic co-cracking reaction network and kinetic model were established,and the kinetic parameters of each reaction was estimated by fitting the experimental data,which can predict the product distribution of co-cracking of high carbon olefins and methanol.