The side reactions play an evident role in the selectivity of propylene in methanol to propylene (MTP) process. It was found that the innovative pressured hydrothermal treatment could improve the distribution of phosphorus species and enhances the interaction between P and Al to enhance hydrothermal stability of ZSM-5 with more acid sites preserved, which showed higher conversion than the conventional phosphorus-impregnated samples, as well as higher yields of propylene and butenes. The interaction between phosphorus species and Al was favored at elevated temperature, however too high hydrothermal treatment temperature could lead to further dealumination. As well as low temperature, the introduction of steam or pressured steam could effectively shift the reaction from larger condensed polyphosphate species toward smaller monomer or oligomeric phosphorus species, which were small enough to penetrate channels of ZSM-5 for consecutive stabilization on framework Al. We look forward to the development status of the catalytic pyrolysis process and expected future development orientation.Ī novel method, the pressured hydrothermal treatment was proposed to activate phosphorus species to stabilize framework Al of ZSM-5 based upon the nature of the endothermic equilibrium reaction between H 2O and phosphorus species. In addition, the effects of different factors that contain the acid properties of zeolite, the ratio of Si/Al, and process conditions on the production of ethylene and propylene are discussed, and the effects of modified elements on the catalytic pyrolysis mechanism are summarized. Propylene and ethylene were produced by the catalytic pyrolysis of different kinds of paraffin over modified ZSM-5 zeolite and summarizes the mechanism and factors influencing the catalytic pyrolysis of paraffin, i.e., various modified elements and posttreatment methods have been employed, such as rare earth elements, alkaline earth and alkali elements, transition metals, P, steaming and alkali treatments, the influences on the properties of modified ZSM-5, and the selectivity of light olefins. This article emphasizes the current research progress that acid-catalyzed paraffin cracking leads to high yields of light olefins.
Recent studies have shown that a considerable amount of propylene and ethylene can be produced by hydrocarbon cracking on modified ZSM-5 zeolite.
Light olefins, especially ethylene, have been produced mainly by hydrocarbon steam cracking in recent decades.
0 kommentar(er)
