Hydrothermally Synthesized HZSM-5/SAPO-34 Composite Zeolite Catalyst for Ethanol Conversion to Propylene
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Hydrothermally Synthesized HZSM-5/SAPO-34 Composite Zeolite Catalyst for Ethanol Conversion to Propylene Chao Duan • Xin Zhang • Rui Zhou Yuan Hua • Jie Chen • Li Zhang
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Received: 30 August 2011 / Accepted: 17 October 2011 / Published online: 27 October 2011 Ó Springer Science+Business Media, LLC 2011
Abstract HZSM-5/SAPO-34 zeolite composites were prepared by hydrothermal synthesis (ZS-HS) and mechanical mixture (ZS-MM), respectively. ZS-HS showed higher propylene yield and better catalytic stability in ethanol conversion than ZS-MM as well as HZSM-5 and SAPO-34. In case of ZS-HS, SAPO-34 at least partially overlapped on HZSM-5, which resulted in the interfacial interaction of HZSM-5 and SAPO-34. Such interaction significantly modified the texture and the acidity of ZS-HS, which in turn affected its catalytic reactivity. ZS-HS showed the higher apparent formation rate of propylene, due to its moderate concentration and strength distribution of acid sites. Propylene, ethylene and butylenes might produce through the parallel reaction pathways and the common intermediate on ZS-HS. Keywords Ethanol Propylene HZSM-5/SAPO-34 composite Hydrothermal synthesis Acidity
1 Introduction Propylene is one of fundamental chemicals in the petrochemical industry. Nowadays, propylene is mainly produced from the steam cracking and fluid catalytic cracking of naphtha. In addition, methanol conversion to olefins
C. Duan X. Zhang (&) R. Zhou Y. Hua J. Chen L. Zhang School of Chemical Engineering, Northwest University, Xi’an 710069, China e-mail: [email protected]
(MTO) process has been developed for producing propylene by nonpetroleum resources. However, in recent years, the production of propylene can not meet the market demand of propylene with the fast growth rate. In view of high oil price and environmental protection, the conversion of ethanol to propylene (ETP), especially ethanol produced by the fermentation of biomass, has risen interesting. ETP is considered to be a carbon–neutral process by the use of renewable biomass. The doped HZSM-5 catalysts, such as, Sr-HZSM-5 [1], Zr-HZSM-5 [2], La-HZSM-5 [3], Ga-HZSM-5 [4] and P-HZSM-5 [5], etc., have been developed for the reaction so far. The highest propylene yield of ca. 32% was obtained at 550 °C [1–5]. Despite these remarkable achievements, the catalytic reactivity and stability of the catalyst should be further improved for industrial application. Zeolite composite with the binary structure is one of promising catalyst materials, because it can not only keep the nature of individual zeolite but also give rise to new distinctive properties. Some zeolite composites have been developed as catalysts for catalytic cracking [6–8], alkylation [9] and MTO [10], etc. The preparation and properties of the zeolite composite significantly affect its catalytic performance [6–10]. In this study, HZSM-5/SAPO-34 composites were prepared by hydrothermal synthesis and mechanical mixture, respectively. ETP on these composites was investigated under different react
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