Study On The Technology Of Conversion From Mathanol And Light Hydrocarbons To Low-carbon Olefins

Low-carbon olefins are mainly obtained from petroleum refining process currently.The shortage of oil resource,the richness of coal resources,the over-production of methanol,and the growing demand for light olefins are driving the development of methanol to olefins?MTO?technology.Most of the MTO technology adopted the fluidized bed process which catalyzed by SAPO molecular sieve,the only one fixed-bed reactor technology was Lurgi MTP process which catalyzed by ZSM-5 molecular sieve.This thesis is committed to fill the gap in fixed-bed process and develops a kind of catalyst of industry value.In oil refining and coal chemical production process has generated a large amount of low value-added low carbon alkane such as petroleum light hydrocarbon,if low carbon alkane was mixed with methanol as feedstock in the MTO processsing,a new way to fully use these low value-added alkane may be developed,and the higher selectivity and yield of low carbon olefins?ethylene,propylene and butylene?may be expected.In this thesis,the basic molecular sieve was ZSM-5 with n?SiO₂?/n?AlO₃?of 300,The catalyst was prepared by incipient-wetness impregnation method.Firstly,ZSM-5 was modified by 2.5%phosphate solution and the processed by 550?thermal-water for 4 hours.Differential kind of self-desighned fixed bed reactor was used to evaluate of the catalytic performance of methanol to olefin catalystsand optimize the technological conditions,including methanol-water ratio,methanol space speed and reaction temperature.The propylene yield reached approximately 51%,15.5%ethylene yield,22%butane yield respectively,and the total olefin C₂⁼+C₃⁼+C₄⁼yields was⁸8.5%under the optimized process conditions.In order to study the influence of n-butane on the selectivity and yield of low carbon olefins in the MTO process,n-butane was mixed with methanol as feedstocks.The results showed that the optimal technology conditions were as follows:480?temperature,3:2methanol-water ratio,1h^-1 methanol space speed,and 0.2h^-1 butane space speed.The experimental results showed that the n-butane mixed feeding can obviously increase the selectivity of butene,butane yield was 26%.To further increase the selectivity or yield of low-carbon olefins,Cerium and Calcium reformed catalysts were prepared,and the modified catalysts were characterized by using BET,XRD and NH₃-TPD.The catalytic performance of modified catalysts were evaluated under the condition of 480?temperature,3:2 methanol-water ratio,1h^-1 methanol space speed and0.2h^-11 butane space speed.It was observed that 99.85%conversion of methanol was achieved,and yielded reached approximately 49%propylene,15%ethylene,24%butane respectively,and total olefin yields was 88%when the ZSM-5 catalyst was modified by 2.5%Cerium.When catalyzed by 3.5%Calcium-ZSM-5 catalyst,the selectivity of olefins was⁵5%propylene,28%butane,yield only 7%ethylene respectively,and conversion rate of methanol was only⁹8.00%,indicating that the MTO selectivity and activity of Ca modified ZSM-5catalyst was less active than 2.5%Cerium modified ZSM-5 catalyst.Finally,the working life of 2.5%Cerium modified ZSM-5 catalyst was investigated for a long period of time.It was found that the catalytic life time was 26 days,indicating that the catalyst has reached the level of industrialization.Duing the running period,the gas-phase yield can be as high as 93.44%while liquid phase gasoline yield was 6.56%.,The analog calculated motor octane number of gasoline was 77.70,while the analog calculated antiknock index was about 84.10.