Benzene Alkylation with Propane over Mo Modified HZSM-5
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Benzene Alkylation with Propane over Mo Modified HZSM-5 Xueqing Huang Æ Xinde Sun Æ Shukui Zhu Æ Zhongmin Liu
Received: 24 April 2007 / Accepted: 7 August 2007 / Published online: 7 September 2007 Ó Springer Science+Business Media, LLC 2007
Abstract Benzene alkylation with propane has been studied over HZSM-5 loading 3.1–15.4 wt% Mo in continuous-flow microreactor under 350 °C and atmospheric pressure with the highest activity obtained at 6.7 wt% Mo loading. C7–9 aromatics were obtained as main products while the total amount of benzene rings kept unchanged. iPropylbenzene and n-propylbenzene are formed primarily, while toluene, ethylbenzene, and ethyl-toluene are formed secondly from the propylbenzenes. Catalytic performance of 6.7 wt% Mo/HZSM-5(38) partially poisoned by NH3 shows that the strong acid sites play a crucial role in the alkylation. Low SiO2/Al2O3 ratio of HZSM-5 in the Mo modified catalysts gives high propane conversion. Two hydrothermal treatment methods were applied to the 6.7 wt% Mo/HZSM-5(38) catalyst, caused decrease of propane conversion but result in different product distribution. A possible reaction mechanism concerning bifunctional active centers resulted from combination of loaded Mo species and strong acid centers on HZSM-5 is proposed. Keywords Acidity
Benzene Propane ZSM-5 Alkylation
X. Huang X. Sun S. Zhu Z. Liu (&) Dalian Institute of Chemical Physics, The Chinese Academy of Sciences, Dalian 116023, Liaoning, China e-mail: [email protected] X. Huang Graduate University of the Chinese Academy of Sciences, Beijing 100049, China X. Huang Daqing Oilfield Company Limited, Daqing 163000, Heilongjiang, China
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1 Introduction Light alkanes such as methane, ethane, propane, and butane are among the most abundant and inexpensive hydrocarbons available today. There has been no efficient commercial process for light alkanes functionalization up to now. One possible way to upgrade light alkanes is to involve them in reactions with other molecules, for example, carbonylation [1] and alkylation of aromatic hydrocarbons. The catalytic synthesis of alkyl aromatics from alkanes and benzene was first reported by Schmerling and Vesely [2] for the Friedel-Crafts catalyst systems and then studied by Olah et al. [3] in superacidic media. The above catalysts showed high catalytic activity and selectivity to products resulted from direct alkane addition to aromatics. However, these catalysts suffered from numerous, mainly environmental and corrosion drawbacks. These drawbacks can be overcome by using solid catalysts. Over the past decade, metal-containing zeolites were reported to be potential catalysts for production of alkylbenzenes from benzene and propane. The attention was mainly focused on HZSM-5 zeolite usually modified by metal species such as Ga or Pt [4–14]. Over Pt/HZSM-5, the major products observed include C1–C4 gases, toluene (T), ethylbenzene (EB), isopropylbenzene (iPB), n-propylbenzene (nPB), and other products (in smaller amounts involving alkyl- and polyalkylbenzenes, nap
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