Cobalt aluminophosphate

The liquid-phase autoxidation of cyclohexane is carried out in the presence of dissolved cobalt salts. A lot of heterogeneous catalysts were developed for this process but most catalysts lacked stability. The incorporation of cobalt ions in the framework of aluminophosphate and aluminosilicate structures opens perspectives for heterogenization of this process. CoAPO (cobalt aluminophosphate) molecular sieves were found to be active heterogeneous catalysts of this oxidation.133 Site isolation was critical to get active catalysts.134... 

A.J. Ramirez-Cuesta, P.C.H. Mitchell, S.F. Parker P.A. Barrett (2000). Chem. Commun., 1257-1258. Probing the internal stracture of a cobalt aluminophosphate catalyst. An inelastic neutron scattering study of sorbed dihydrogen molecules behaving as one- and two-dimensional rotors. 

Ramirez-Cuesta A J, Mitchell P C H and Parker S F (2001), An inelastic neutron scattering study of the interaction of dihydrogen with the cobalt site of a cobalt aluminophosphate catalyst. Two-dimensional quantum rotation of adsorbed dihydrogen , 7 Mol Catal A Chem, 167, 217. 

A combined FTIR and EPR study, using NO and NO2 as molecular probes of the nature and reactivity of cobalt ions in microporous cobalt-aluminophosphates with chabasite-related structure (CoAPO-18 and CoAPO-34) has been performed both at 298 K and 77 K. CoAPOs materials were prepared by following a facile route during which the cobalt ions were directly inserted in the synthesis gels. 

The studies presented here deal with the coordination of cobalt atoms in cobalt aluminophosphates (CoAPOs). The compounds investigated include those of CHA topology (CoMnAPO-34) [51] and of SOD topology [42].In the case of the CoMnAPO, a perfect fit to the filtered EXAFS function of the first coordination shell is obtained with four oxygen atoms at a distance Rco-o of 1-93 A. This result is consistent with the presumed incorporation of the Co atoms into the alu-minophosphate framework [51]. 

Recently fluoride ions were introduced in the starting mixtures of ionothermal syntheses in order to prepare (cobalt)aluminophosphate molecular sieves [200, 201]. In these systems, the solvent is an ionic liquid or eutectic mixture and, in many cases, can be considered as a precursor of the structure directing agent. It seems that F also plays important roles for the crystallization in these media containing few water molecules. 

Usually, the synthesis of zeolite materials requires an excess amount of reactant reagents. After the resultant products are filtered from the reaction mixture, the filtrate (mother-liquor) containing abundant nutrients is discarded as a waste solution. With the concept of green chemistry, Yu and coworkers attempted a mother-liquor-reused route to synthesize cobalt aluminophosphate zeolites CoAPO-CJ51 (GIS) and CoAPO-CJ52 (LAU) by introducing Co + cations into the filtrated mother liquors of two layered aluminophosphates Mu-4 and AlPO-IM, respectively [47]. The mother-liquor-reused route provides a low-cost way for the synthesis of zeolite materials. 

Ionic liquid l-methyl-3-ethylimidazolium bromide ([EMim][Br]) is the most commonly used ionic Uquid in the ionothermal synthesis of zeoUte materials, leading to the formation of cobalt aluminophosphate zeolites SIZ-7 (SIV), SIZ-8 (AEI), and SIZ-9 (SOD) [56]. 

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