Applied Catalysis A: General 505 (2015) 1–7 Contents lists available at ScienceDirect Applied Catalysis A: General journal homepage: www.elsevier.com/locate/apcata CHA/AEI intergrowth materials as catalysts for the Methanol-to-Olefins process Rachel L. Smith a , Stian Svelle b , Pablo del Campo b , Terje Fuglerud c , Bjørnar Arstad d , Anna Lind d , Sachin Chavan b , Martin P. Attfield a , Duncan Akporiaye d , Michael W. Anderson a,∗ a Centre for Nanoporous Materials, School of Chemistry, The University of Manchester, Manchester, M13 9PL, UK b InGAP, Department of Chemistry, University of Oslo, PO Box 1126, 0315 Oslo, Norway c INEOS, Herøya Industrial Park, N-3936 Porsgrunn, Norway d SINTEF, Materials and Chemistry, PO Box 124, Blindern, 0314 Oslo, Norway a r t i c l e i n f o Article history: Received 16 February 2015 Received in revised form 19 June 2015 Accepted 21 June 2015 Available online 30 June 2015 Keywords: MTO SAPO-34 SAPO-18 Intergrowth Silicon content a b s t r a c t A series of SAPO-34/SAPO-18 intergrowth materials were prepared with a range of silicon content from 0.5 to 7.0%, where low levels of silicon resulted in SAPO-18 and higher levels resulted in CHA/AEI inter- growths. These materials were tested for their performance in the Methanol-to-Olefins reaction. The acidity of the catalysts was related to their silicon content, where a higher level of silicon gave a greater acid site density. The catalytic activity increased with increasing acid site density. There was consequently a higher level of heavy hydrocarbons in the catalysts at the end of the reaction in the materials with higher silicon content. The selectivity as a function of overall time on stream was similar for all catalysts, but at a given level of conversion, the C 2 /C 3 ratio was lower for the materials with higher AEI content. Catalysts with a higher ratio of AEI cages had a higher selectivity to C 3 and C 4 products than the other catalysts, due to the larger size of the internal AEI cage. The C 2 /C 3 ratio showed a strong correlation to the cage shape, making catalysts with high AEI content suitable where higher propylene ratios are desired. © 2015 Published by Elsevier B.V. 1. Introduction The Methanol-to-Olefins (MTO) process is a route to selectively forming light olefins (C 2 –C 4 products) from methanol. This process is desirable due to the expanding worldwide demand for poly- olefins and the fact that methanol can be produced from non-oil feedstocks (coal, natural gas or biomass) [1,2]. Small-pore molec- ular sieve SAPO-34 is established as an effective catalyst for the MTO process due to the high selectivity to ethylene and propylene and high conversion rates [2]. SAPO-34 is currently the preferred commercial catalyst for the UOP/Hydro MTO process [3]. Silicoaluminophosphate SAPO-34 is a member of the family of zeolites with the CHA framework topology, consisting of tilted double 6-rings (D6R, shown in grey on Fig. 1a) connected by 4- membered rings resulting in large internal CHA cages (shown in orange) with 8-ring pore openings of 3.8 Å [4]. The small pore open- ing allows only linear olefins and small molecules to diffuse through [1,5]. This makes SAPO-34 shape selective for light olefins, but the ∗ Corresponding author. E-mail address: m.anderson@manchester.ac.uk (M.W. Anderson). large internal cages afford enough space for aromatic intermediates to reside inside the cages. Although a number of mechanisms [1] have been proposed for this reaction, the most generally accepted is the ‘hydrocarbon pool’ mechanism first proposed by Dahl and Kolboe [6]. In this mechanism, the hydrocarbons (typically aromat- ics, such as polymethylbenzenes and napthalenes) trapped in the SAPO-34 cages are key intermediates in the MTO reaction, whose build-up are the reason for the induction period which may be observed at the beginning of the reaction [7]. Although these inter- mediates are essential to the MTO reaction, the large internal cage dimensions of SAPO-34 also make it susceptible to coking by larger aromatic compounds, such as phenanthrene and pyrene [8]. Coking is established as the main cause of catalyst deactivation in SAPO- 34 and for many SAPO-34 catalysts the limited catalytic lifetime is a disadvantage (this has been recently reviewed in detail by Chen et al [9]). However, the catalysts can be easily regenerated through high temperature treatment [1]. There is now extensive literature concerning SAPO-34 catalysts, and also the zeolite analogues, with the intention of understanding and tuning their properties to give superior catalysts. The catalytic performance can be influenced by both the reaction conditions and also the properties of the catalyst [10]. For example, Bleken et al. http://dx.doi.org/10.1016/j.apcata.2015.06.027 0926-860X/© 2015 Published by Elsevier B.V.