Modification Of HZSM-5 And Its Catalytic Performance In Coupling Transformation Of Methanol With 1-Butene To Propylene

The demand for olefins,especially for propylene,is increasing every year.Thus,how to enhance the production of propylene has gradually become a hot research topic.The main processes to produce olefins are steam cracking of naphtha and fluid catalytic cracking（FCC）.Although the naphtha to olefins has been in large scale for production of propylene,it is not meeting the ever-increasing of industrialization demands.Therefore,it is becoming increasingly urgent to find new method to increase propylene production.Methanol to olefins（MTO）has been widely developed in recent years.Its catalytic process is exothermic and accompanied with a great deal of by-product of 1-butene.In addition,other techniques such as C₄hydrocarbons to produce propylene,which is endothermic process,has been regarded as an attractive choice because of its abundant supply of feedstock and high selectivity to aimed products.Therefore,in order to make full use of the energy and enhance the selectivity to target products,coupling the exothermic MTO reaction with endothermic 1-butene cracking reaction has been profitable and promising.In this dissertation,the catalytic performance of phosphorus modified,alkali-treated phosphorus modified,and iron and manganese bimetallic modified HZSM-5 in coupling methanol with 1-butene was studied in a fixed-bed reactor,respectively.1.HZSM-5 catalysts with different phosphorus contents were prepared by the isomorphous substitution method.It was characterized by the methods of XRD,ICP-OES,SEM,FT-IR,N₂adsorption-desorption,NH₃-TPD,XPS,and TG-DTA,respectively.The test indicated that the amount of acidity of modified HZSM-5 is decreased and the H[P,Al]-ZSM-5（0.4）exhibits the highest coke tolerance rate.The catalytic performance of H[P,Al]-ZSM-5（X=0,0.2,0.4,0.6,0.8）in coupling reaction of methanol with 1-butene was investigated in the fixed-bed reactor under the operating conditions of T=550℃,P=1 atm,molar ratio of methanol/1-butene=1.0and WHSV=3.53 h^-1.The H[P,Al]-ZSM-5 catalyst synthesized by isomorphous substitution Al with P species about 40%exhibits higher catalytic stability and selectivity for propylene is 35.6%.2.Hierarchically porous P substituted HZSM-5（H[P,Al]-ZSM-5-AT-0.05M）was successfully synthesized by isomorphous substitution method with introduced P atoms into HZSM-5 zeolite followed by alkali treatment.H[P,Al]-ZSM-5-AT-0.05M was characterized by XRD,ICP-OES,SEM,FT-IR,N₂adsorption-desorption,NH₃-TPD,XPS,Py-IR,and TG-DTA,respectively.The surface area,pore volume,particle size and P/Al（molar ratio）of H[P,Al]-ZSM-5-AT-0.05M are 328 m².g^-1,0.23cm³.g^-1,563 nm and 0.027,respectively.The catalytic performance of H[P,Al]-ZSM-5-AT-0.05M in coupling reaction of methanol with 1-butene was investigated in the fixed-bed reactor.Under the conditions of reaction temperature at500℃,pressure at 0.1 MPa,molar ratio of methanol/1-butene to 1.0 and WHSV of3.53 h^-1,the main product is propylene with the selectivity and yield of 33.7%and31.0%,respectively.Hydrogen transfer index calculated is to 0.24.Moreover,its diffusion limitation was investigated with the self-etherification of benzyl alcohol reaction.The value of Thiele modulus（f）and effectiveness factor（η）are 0.08 and16.9,respectively.3.Iron and manganese modified HZSM-5（Fe-Mn-ZSM-5）was prepared and characterized by means of XRD,SEM,BET,TG-DTA,NH₃-TPD and FT-IR.The test indicated that the Fe-Mn-ZSM-5 with the molar ratio of Fe/Mn to 1:1 exhibited the good catalytic performance and lowest coke formation rate.The catalytic performance of Fe-Mn-ZSM-5（1:1）in coupling reaction of methanol with 1-butene was investigated in the fixed-bed reactor.Under the conditions of reaction temperature at550℃,pressure at 0.1MPa,molar ratio of methanol/1-butene to 1.0 and WHSV of3.53 h^-1,the main product is propylene with the selectivity and yield of 44.6%and38.3%,respectively.