Ti-ferrierite and TiITQ-6: synthesis and catalytic activity for the epoxidation of olefins with H 2 O 2 A. Corma,* U. Diaz, M. E. Domine and V. Fornés Instituto de Tecnología Química, UPV-CSIC, Universidad Politécnica de Valencia, Avda. de los Naranjos, s/n, Valencia, 46022 Spain. E-mail: acorma@itq.upv.es Received (in Cambridge, UK) 3rd November 1999, Accepted 8th December 1999 A new zeolitic material TiITQ-6 has been obtained by the direct synthesis of a layered titanosilicate precursor, fol- lowed by delamination; titanium is tetrahedrally coordi- nated in framework positions and, while the zeolite derived from the precursor has little activity owing to geometrical constraints, the delaminated TiITQ-6 material is active and selective for the epoxidation of hex-1-ene with H 2 O 2 . A new generation of oxidation catalysts started when TS-1 1 was synthesized and showed excellent catalytic activity in aqueous media using H 2 O 2 as oxidant. Since then other Ti containing molecular sieves have been synthesized but only a few of them, of which TS-2 2 and Ti-beta 3 are outstanding, have shown to be active and selective for the epoxidation of linear olefins with H 2 O 2 . Recently 4 it has been proposed that the presence of Ti 4+ ions tends to impede or to decrease the nucleation rates in the organothermal Ti-ferrierite (TiFER) system but by seeding with Si-ferrierite it was possible to prepare a Ti containing ferrierite. Unfortunately no catalytic activity for the sample was detected. 4 It was also demonstrated that it was possible to synthesize a laminar aluminosilicate precursor of ferrierite (PREFER) 5 that upon calcination could produce the ferrierite structure. In our case, we have succeeded in synthesizing directly, without seeding, the titanium containing laminar analogue TiPREFER. This was prepared in the following manner: 10 g silica (Aerosil 200, Degussa), 0.759 g of titanium(IV) ethoxide (Alfa 98%), 28.186 g H 2 O (MiliQ), 26.008 g of 4-amino-2,2,6,6-tetra- methylpiperidine (Fluka 98%), 9.246 g NH 4 F (Aldrich 98%) and 3.462 g HF (Aldrich, 48.1 wt%) were mixed in an autoclave at 408 K for 10 days. The resulting product TiPREFER was filtered off, washed three times, and dried at 333 K. The X-ray diffraction (XRD) pattern of the product is shown in Fig. 1(a). The UV spectrum of the sample shows a single absorption band at ca. 210 nm corresponding to isolated framework Ti in tetrahedral coordination [Fig. 2(a)] and this band was main- tained after calcination at 923 K for 12 h [Fig. 2(b)] to produce the well crystallised Ti containing ferrierite TiFER [Fig. 1(d)]. The catalytic activity of this material for the epoxidation of hex- 1-ene with H 2 O 2 was tested in a batch reactor in the following way: 16.5 mmol olefin, 11.8 acetonitrile and 300 mg TiFER (1.3 wt% TiO 2 ) were introduced in a three necked glass flask which was heated to 323 K in a temperature controlled silicon bath. 4.5 mmol H 2 O 2 (30% vol) was then added dropwise and the catalytic results obtained are given in Table 1. Very little conversion of hex-1-ene was observed for TiFER owing to diffusion limitation in the pores of this structure, in a similar manner found to that for another unidirectional 10-member ring pore zeolite Ti-ZSM-48. 6 Recently, 7 a new approach has been undertaken for expand- ing the use of zeolites to catalyze reactions when the accessibility of the reactants to the active sites is hindered. This involves the preparation of lamellar precursors of zeolites whose structure is subsequently delaminated making potentially catalytically active sites accessible through the external surface. Up to now the only delaminated material reported has been ITQ-2 which shows outstanding adsorption and catalytic Fig. 1 X-Ray diffraction patterns of (a) TiPREFER, the laminar precursor of Ti-ferrierite, (b) TiPREITQ-6, the expanded material, (c) TiITQ-6, the delaminated zeolite and (d) TiFER, a Ti-ferrierite zeolite obtained after calcination of TiPREFER. Fig. 2 Diffuse UV–VIS reflectance spectra of TiITQ-6: (a) as synthesised (TiPREFER), (b) Ti-Ferrierite, (c) TiITQ-6 and (d) TiITQ-6 after two reaction–calcination cycles. Table 1 Catalytic activity of Ti zeolites for hex-1-ene epoxidation a Sample X hex-1-ene (% of maximum) Selectivity to epoxide (%) Selectivity to H 2 O 2 (%) TON TiFER 3.2 85.2 23 6 Ti-beta 18.0 97.2 77 20 TiITQ-6 19.7 95.5 73 23 TiITQ-6 b 17.7 93.2 56 21 a Reaction conditions: 16.5 mmol olefin; 11.8 g acetonitrile; 4.5 mmol H 2 O 2 ; 300 mg catalyst; 323 K, 5 h. b After two regeneration cycles. This journal is © The Royal Society of Chemistry 2000 Chem. Commun., 2000, 137–138 137