Synthesis of the large pore aluminophosphate STA-1 and its application as a catalyst for the Beckmann rearrangement of cyclohexanone oxime

The preparation of stable large pore aluminophosphate (AlPO) zeotypes offers materials for applications in adsorption and catalysis. Here we report the synthesis of the pure AlPO with the SAO topology type (AlPO STA-1) using N,N′-diethylbicyclo[2.2.2]oct-7-ene-2,3:5,6-dipyrrolidine (DEBOP) as the organic structure directing agent in the presence of fluoride. The AlPO STA-1 can be rendered microporous (pore volume 0.36 cm3 g−1) via calcination and the calcined form remains stable in the presence of moisture. The structure of the dehydrated form has been established by Rietveld refinement (tetragonal P4̄n2, a = 13.74317(10) Å, c = 21.8131(5) Å, V = 4119.94(16) Å3). Multinuclear 27Al and 31P MAS NMR, together with 2D COSY and CASTEP NMR calculations, enables resolution and assignment of the signals from all crystallographically distinct Al and P framework sites. Structural elucidation of the as-prepared aluminophosphate-fluoride is more challenging, because of the presence of partially protonated OSDA molecules in the 3D-connected channel system and in particular because the fluoride ions coordinate with positional disorder to some of the Al atoms to give 5-fold as well as tetrahedrally-coordinated framework Al species. These are postulated to occupy Al–F–Al bridging sites, where they are responsible for distortion of the framework [P4̄n2, a = 13.3148(9) Å, c = 22.0655(20) Å, V = 3911.9(7) Å3]. Calcination and removal of fluoride ions and OSDAs allows the framework to expand to its relaxed configuration. The SAO topology type aluminophosphate can also be synthesised with small amounts of Si and Ge in the framework, and these SAPO and GeAPO STA-1 materials are also stable to template removal. IR spectroscopy with CO as a probe at 123 K indicates all have weak-to-mild acidity, increasing in the order AlPO < GeAPO < SAPO. These STA-1 materials have been investigated for their activity in the Beckmann rearrangement of cyclohexanone oxime to ε-caprolactam at 598 K: while all are active, the AlPO form is favoured due to its high selectivity and slow deactivation, both of which are a consequence of its very weak acid strength, which is nevertheless sufficient to catalyse the reaction.


S3. Comparative studies with SAPO-37
For the synthesis of SAPO-37, 0.2571 g of water, 0.6918 g phosphoric acid (85 wt %) and 0.1802 g of fumed silica were mixed at RT for 30 mins.Then 0.6118 g of alumina (76.5 wt %) was added very slowly with vigorous stirring.The mixture was stirred for further 4 hours at RT and then 3.0506 g tetrapropylammonium hydroxide (40% solution) and 0.0547 g tetramethylammonium hydroxide were added.The final gel pH was approximately 7. The mixture was then stirred for further 2 hours and the gel was sealed in a Teflon-lined autoclave and heated at 463 K for 48 h.The overall gel composition was 2 H 3 PO 4 : SiO 2 : 2 Al(OH) 3 : 0.05 TMAOH: 2 TPAOH: 50 H 2 O.The resulting solid was isolated by centrifugation, washed with distilled water and dried at 333 K overnight.In order to remove the OSDA, the solid was calcined at 923 K for 12 h in air.ICP-AES indicated an inorganic composition of Al 1.02 Si 0.34 P 0.60 O 4 .

Figure S10 .
Figure S10.IR spectrum of dehydrated AlPO STA-1 in the hydroxyl region (red, bold) and difference spectra after low temperature adsorption of CO at different pressures.

Table S1 .
Calculated energies of 1 -4 DEBOP OSDAs included per unit cell of AlPO 4 STA-1 indicate that the filling of all four positions within the unit cell provide favourable binding.All Energies in kcal /mol of OSDA.

Table S2 .
Chemical analysis of all STA-1 samples.

Table S3 .
Crystallographic details of dehydrated samples.

Table S4 .
Al-O and P-O bond lengths and O-Al-O and O-P-O bond angles for refined structure of calcined and dehydrated AlPO STA-1 (SAO).

Table S6 .
Al-O and P-O bond lengths and O-Al-O and O-P-O bond angles for refined structure of as-made and dehydrated AlPO STA-1 (SAO).