The Effect of Zeolite Structure on the Activity and Selectivity in p -Xylene Alkylation with Isopropyl Alcohol
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The Effect of Zeolite Structure on the Activity and Selectivity in p-Xylene Alkylation with Isopropyl Alcohol Zuzana Musilova´-Pavlacˇkova´ Æ Martin Kubu˚ Æ Allen W. Burton Æ Stacey I. Zones Æ ˇ ejka Martina Bejblova´ Æ Jirˇ´ı C
Received: 21 March 2009 / Accepted: 15 May 2009 / Published online: 8 July 2009 Ó Springer Science+Business Media, LLC 2009
Abstract The effect of zeolite architecture and channel dimensionality on p-xylene conversion and selectivity to 1-isopropyl-2,5-dimethyl-benzene was investigated in p-xylene alkylation with isopropyl alcohol over novel zeolites SSZ-33 and SSZ-35. Catalytic behavior of these zeolites was compared with those of zeolites Beta, mordenite, ZSM-11 and ZSM-5. It was found that p-xylene conversion increases with increasing pore size and connectivity of the channel system of individual zeolites with the exception of SSZ-35, which possesses a system of onedimensional 10-ring channels that periodically open into wide, shallow cavities circumscribed by 18-rings. SSZ-35 exhibited the highest conversion among all zeolites at the reaction temperature of 150 °C and also the highest selectivity to 1-isopropyl-2,5-dimethyl-benzene. Molecular modeling confirmed the dimensions of the 18-ring cages are optimal for the formation of this alkylation product. Keywords SSZ-35 SSZ-33 p-Xylene Alkylation 2,5-Dimethyl cumene (1-isopropyl-2,5-dimethyl-benzene)
Z. Musilova´-Pavlacˇkova´ M. Kubu˚ M. Bejblova´ J. Cˇejka (&) J. Heyrovsky´ Institute of Physical Chemistry, v.v.i., Academy of Sciences of the Czech Republic, Dolejsˇkova 3, 182 23 Prague 8, Czech Republic e-mail: [email protected] A. W. Burton S. I. Zones Chevron Energy and Technology Company, Richmond, CA 94802, USA
1 Introduction Alkylation reactions are important processes that are industrially used in large scale technological units that include benzene alkylation with ethylene to provide ethylbenzene or benzene alkylation with propylene to prepare cumene or their further reactions including disproportionations or transalkylations [1–6]. In addition to their petrochemical impact, these reactions can be used to investigate the internal channel system of zeolites as size and dimensionality of zeolite channels substantially influence the rate and selectivity in transformations of aromatic hydrocarbons [7–10]. Both conversions and selectivities in these reactions depend on the architecture of the respective zeolite reaction volume [11, 12]. Zeolites are the most important industrial catalysts and serve as model systems due to their well-crystalline structure with channels of 8-, 10-, 12-, 14- and even 18rings of different shapes and sizes [13]. These channels form from one-dimensional (1D) up to three-dimensional (3D) arrays of channels with/without cavities in their intersections or even possessing cages in 1D channel system [14]. In principal, increasing catalytic activity of different structural types of zeolites could be related to the increasing pore size and dimensionality of the channels. This prediction
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