Journal of Catalysis 238 (2006) 79–87 www.elsevier.com/locate/jcat Direct synthesis of a 9 × 10 member ring zeolite (Al-ITQ-13): A highly shape-selective catalyst for catalytic cracking R. Castañeda, A. Corma ∗ , V. Fornés, J. Martínez-Triguero, S. Valencia Instituto de Tecnología Química (UPV-CSIC), Universidad Politécnica de Valencia, Avenida de los Naranjos s/n. 46022 Valencia, Spain Received 6 October 2005; revised 25 November 2005; accepted 28 November 2005 Available online 9 January 2006 Abstract A synthesis route for preparing ITQ-13, a tridirectional medium-pore zeolite containing 9- and 10-member ring pores, has been found that allows the introduction of framework Al by direct synthesis. It has been shown that ITQ-13 can also be prepared in a fluoride-free media. The directly synthesized Al containing ITQ-13 sample presents acid sites as strong or even stronger than ZSM-5. The strong electric field gradient in ITQ-13 and the smaller pore dimensions are responsible for the strong acidity and shape selectivity that increases the production of propylene during the cracking of vacuum gasoil compared with ZSM-5.  2005 Elsevier Inc. All rights reserved. Keywords: ITQ-13; Zeolite; Catalytic properties; 10 × 9 member ring pore zeolite; Propylene production in catalytic cracking; Zeolite-cracking additive 1. Introduction There is a continuous effort in industry and academia to obtain new zeolite structures, as well as to modify the character- istics of the existing ones [1–3]. Various series of new structures with extra large, large, medium, and small pore sizes have been reported [4–18]. Medium pore size zeolites—those formed by 10-member ring (MR) channels, such as ferrierite [19], ZSM-22 [20], Theta-1 [21], SSZ-35 [22], and especially ZSM-5 [23]—have been successful shape-selective catalysts [24]. More specifi- cally, ZSM-5 has strongly enhanced the possibilities of FCC units through shape-selective cracking of n-olefins to increase the formation of propylene [25]. Cracking of model hydrocar- bons using a large number of zeolites with different pore di- mensions and topologies led to predictions that zeolites with a bidirectional or tridirectional pore system formed by 9 or 9 × 10 MR should be very adequate FCC additives for boosting propylene [26,27]. Recently, a new zeolite (ITQ-13) was syn- thesized [28] that presents a tridirectional set of channels in * Corresponding author. Fax: +34 96 3877809. E-mail address: acorma@itq.upv.es (A. Corma). which one of them has 9 MR (4.0 × 4.9 Å) openings and the other two channels are straight (4.7 × 5.1 Å) and sinusoidal 10 MR (4.8 × 5.7 Å) [29]. Zeolite ITQ-13 is described as a material prepared in flu- oride media with hexamethonium as an organic structure- directing agent (OSDA) that is able to incorporate boron in the framework by isomorphic substitution of silicon during synthesis [28]. By means of a postsynthesis treatment, it was possible to exchange aluminium with boron, giving Al-ITQ- 13, a material of sufficient acidity for catalytic activity [30]. Unfortunately, in the previously reported synthesis [28] it was found extremely difficult to directly synthesize the alu- minosilicate form of ITQ-13 with significant levels of alu- minium. In this paper we describe a new synthesis route for ITQ- 13 that allows us to readily incorporate framework Al dur- ing the synthesis, resulting in very thermally and hydrother- mally stable samples. We also show that this synthesis route makes it possible to synthesize ITQ-13 in a fluoride-free me- dia. Acid samples showed cracking activity close to that of ZSM-5, but with a much higher propylene-to-propane ratio in the gases when used as a catalyst additive for cracking vacuum gasoil. 0021-9517/$ – see front matter  2005 Elsevier Inc. All rights reserved. doi:10.1016/j.jcat.2005.11.038