Nondestructive immobilization of cobalt and copper Schiff base complexes in silica aero- and xerogels was achieved via the sol−gel method using a precursor N,N‘-ethylenebis(salicylidenaminato) (salen) ligand modified with pendant silyl ethoxy groups. Aerogels were obtained by semicontinuous extraction of the wet gels with supercritical CO₂ and xerogels by conventional drying. Cobalt and copper(salen) containing silica gels were characterized by FTIR, UV−vis, and XPS spectroscopy, laser ablation-ICP-MS, and EPR studies. Aero- and xerogel incorporated salen compounds exhibited similar spectroscopic properties to cobalt/copper(salen) precursors and known metal(salen) compounds. BET measurements confirmed the importance of supercritical CO₂ drying in maintaining the mesoporous structure of the aerogel. Laser ablation-ICP-MS and EPR studies of the aerogels showed that a uniform distribution of the isolated metal(salen) complex was achieved via molecular mixing using the sol−gel method. Stability of these materials was demonstrated by thermogravimetric analyses in air and leaching studies conducted under typical liquid-phase oxidation conditions. XPS analyses showed surface relative atomic concentrations in the modified gels to be similar before and following leaching studies.

The catalytic synthesis of 1,3-diaminopropane from 1,3-propanediol and ammonia was studied in a continuous fixed-bed reactor in the pressure range 50 to 150 bar. The unsupported Co-based catalysts applied were characterized by N₂physisorption, XRD, XPS, TPR, and ammonia adsorption using pulse thermal analysis and DRIFT spectroscopy. The latter investigations revealed that the best catalyst, 95 wt% Co–5 wt% Fe, contained only very weak acidic sites, unable to chemisorb ammonia. The absence of strong acidic and basic sites was crucial to suppress the various acid/base-catalyzed side reactions (retro-aldol reaction, hydrogenolysis, alkylation, disproportionation, dimerization, oligomerization). Other important requirements for improved diaminopropane formation were the use of excess ammonia (molar ratio NH₃/diol>20) and the presence of the metastable β-Co phase. A small amount of Fe additive could efficiently hinder the transformation of this phase into the thermodynamically stable α-Co phase and thus prevent catalyst deactivation up to 10 days on stream. Application of supercritical ammonia almost doubled the selectivity to amino alcohol and diamine. The selectivity enhancement in the near-critical region is attributed to elimination of the interphase mass transport limitations and to the resulting higher surface ammonia concentration.