Effect Of P Atom Modified MCM-41 Loaded Molybdenum Oxide On Self-metathesis Of 1-butene To Propylene

Propylene,used to produce synthetic resins,synthetic rubber,synthetic fibers,and fine chemicals.These products involve all aspects of clothing,food,housing and transportation,benefiting people's lives.At present,from upstream propylene products to downstream propylene derivatives industry chain,there is a contradiction between supply end and demand end.The contradiction is becoming more and more serious,the supply side's production capacity is out of balance with the demand side's demand,and the market is in short supply.However,the traditional propylene production process has been unable to meet the rapid growth of propylene demand.The process of 1-butene self-metathesis to propylene can realize the conversion of low-value olefins to high-value olefins,which provides a new utilization way for the resource utilization of C4 olefins.And at the same time it can alleviate the present situation of ethylene shortage to produce propylene,which has important practical significance and wider application prospect.Based on this,the heteroatom modified MCM-41 supported molybdenum-based catalysts were studied,and the catalysts were applied to the reaction of 1-butene self-metathesis to propylene.(1)A series of heteroatom-doped MCM-41 was prepared by hydrothermal method as supports,and the catalyst loaded with molybdenum oxide was impregnated by wet method.The reaction performance of 1-butene self-metathesis to propylene catalysts were evaluated in a self-made fixed-bed reactor.The catalysts were characterized by XRD,N2 adsorption-desorption,UV-Vis,pyridine adsorption infrared spectroscopy(Py-IR),H2-TPR,NH3-TPD.XRD and N2 adsorption-desorption characterization were analyzed the changes in the diffraction peaks,specific surface area,and pore diameter of the modified catalyst,and then analyzing the influence of modification on catalyst structure.Pyridine adsorption infrared spectrum and NH3-TPD characterization by analyzing the type and amount of acid in the catalyst,and then analyzing the effect of acidity on the catalytic performance.UV-Vis and H2-TPR characterization by analyzing the structure,redox characteristics of the surface-active substances on the catalyst,and then analyzing the dispersion degree of molybdenum oxide on the carrier surface.(2)Different elements P,Al,Zn,Fe and Mg were selected to modify the catalyst,and the influence of molybdenum-based catalysts modified by different elements on the reaction of 1-butene self-metathesis to propylene was investigated.The results showed that the activity of catalysts modified by different elements was different in the reaction.The effect of catalyst preparation conditions on the reaction of 1-butene self-metathesis to propylene was investigated.In order to obtain the catalyst suitable for the reaction and with the best performance,a series of P catalysts were prepared by varying the preparation conditions P doping amount,molybdenum loading,crystallization temperature(100?,110?,120?,130?),crystallization time(24 h,36 h,48 h,60 h,72 h).and the catalysts was applied to the reaction of 1-butene self-metathesis to propylene.The results showed that the difference in preparation conditions affects the performance of the reaction,the crystallization temperature was too low or too high,and the crystallization time was too short or too long,which had a great impact on the catalyst,and then affected the activity of the catalyst.Butene conversion and propylene yield increased first and then decreased with the increase of P doping amount.The amount of P doping remained unchanged,changing the molybdenum loading,butene conversion and propylene yield increased first and then decreased with the increase of molybdenum load.Among them,2%Mo/5P-MCM-41 catalyst(100?,60 h)has the highest metathesis activity,butene conversion is 82.2 mol%,and propylene yield is 26.8 mol%.The influence of the reaction conditions on the 1-butene self-metathesis to propylene were also investigated.By changing the reaction temperature and the amount of catalyst,the effects of reaction conditions on the reaction of 1-butene self-metathesis to propylene were investigated.The results showed that the reaction conditions also affected the performance of the reaction.(3)The stability of the catalysts were analyzed.The newly prepared 2%Mo/MCM-41 and 2%Mo/5P-MCM-41 catalysts(110?,48 h,0.2 g)maintained stable 1-butene conversion and propylene yield within 20 h.The deactivated 2%Mo/MCM-41 and 2%Mo/5P-MCM-41 catalysts were regenerated,and the performance test of the regenerated catalysts showed that:P doped with MCM-41 was beneficial to improve the regenerated catalyst stability.The results showed that compared with 2%Mo/MCM-41 catalyst,P-doped MCM-41 as a carrier can make molybdenum oxide species more uniformly distributed on the catalyst surface,and make the catalyst have a certain degree of acidity,which improveed 1-butene activity and stability of self-metathesis reactions.When the amount of catalyst used for the 1-butene self-metathesis reaction was increased by 0.1 g,2%Mo/5P-MCM-41 catalyst(110?,48 h,0.3 g),1-butene conversion and propylene yield increased from 65.9 mol%,21.7 mol%to 90.5 mol%,25.7 mol%,and the 1-butene conversion and propylene yield remained stable for nearly 90 hours.Reactivation of the deactivated catalyst described above and the reaction performance test showed that:2%Mo/5P-MCM-41(regenerated)catalyst,compared with the newly prepared catalyst,both the initial conversion of 1-butene and the initial yield of propylene are reduced,and the propylene yield is reduced to 10 mol%after 10 hours of reaction.It can be seen that the selection of an appropriate amount of catalyst in the catalytic reaction is also crucial to exert the best performance of the catalyst.