|
Propylene is fundamental raw materials of petrochemical industries. Recently, due to the rapid growth of demand for propylene derivatives,the market demand for propylene is growing fast. At present, the main ways of propylene production are the steam cracking and fluid catalytic cracking (FCC) of naphtha.However, since petroleum resource is shortage in the world, the production of propylene can not satisfy the market demand of propylene. Moreover, other routes for the production of propylene, such as,methanol to propylene (MTP), olefins disproportionation and the dehydrogenation of propane, show some disadvantages, such as, low production capacity, high energy consumption, high emission and high cost. Hence, it is necessary to explore a new way to increase the production of propylene.With the breakthrough in the technology of bio-ethanol, the large-scale production of ethanol has become possible. The conversion of ethanol to propylene, especially bio-ethanol by the fermentation of biomass as raw material, is considered to be carbon neutral utilization.This new technical route is a combination of organic chemical industry and biological chemical industry. It is one of key problems to develop the an efficient catalyst. At present, in order to promote the industrial application of ethanol conversion to propylene, we mainly focuses on the research and development of the high efficiency catalyst in this dissertation.In this work, the Zn-modified Hβ catalysts (Zn/Hβ) were prepared by the impregnation and then it was used for ethanol to propylene. The effects of Zn-loading, anion of the precursor of Zn and the reaction conditions (temperature, ethanol partial pressure and contact time) on the reactivity of the catalyst were investigated. In addition, the properties and structure of the catalyst were characterized by X-ray powder diffraction (XRD), N2isothermal adsorption-desorption, NH3temperature-programmed desorption, etc.. The relationship between the catalytic reactivity of the catalysts with their properties was discussed. The technology process of the conversion of ethanol to propylene over16%Zn/Hβ-C catalyst was primary designed and calculated.(1)The Zn-loading, the anion of the precursor of Zn and reaction conditions played great influences on the reactivity of the Zn/Hβ catalysts. Under the optimal reaction conditions,723K, ethanol partial pressure=23kPa, WHSV=2.8h"1, the highest propylene yield of43%was obtained on16%Zn/Hβ catalyst. (2) The addition of Zn into Hβ could not changed the framework of Hβ, but modified the acidity of the Zn/Hβ catalysts. The acidity of the catalysts was close relative to the Zn-loading and the anion of the precursor of Zn.(3) Acidity of the catalysts played important roles on the reactivity of the catalyst. In order to gain the high propylene yield, it is necessary that the catalyst should have the proper acidity.(4) The anion of the precursor of Zn had great influences on the properties of the catalyst, which in turn affected the reactivity of the catalyst. ZnCl2might be better precursor of Zn than ZnSO4, Zn(NO3)2and Zn(Ac)2.(5) The simple calculation and design of the technology process for ethanol to propylene was made, and the principal technology process was proposed.
|