SummaryIn this work, 3 currently used trimerization catalysts, TMR-2 (quaternary ammonium), K-15 (potassium octoate), and PU-1792 (potassium acetate) were used to produce rigid polyisocyanurate (PIR) foams with certain amounts of isocyanurate contents. The results from Fourier transform infrared (FTIR) quantitative analysis showed that PU-1792 had the highest catalytic efficiency in isocyanurate formation. Then, the effect of different amounts of PU-1792 catalyst on isocyanurate ring output was further investigated, and the result showed that the highest amount of isocyanurate ring formation could be attained by the 5 pphp of PU-1792 catalyst. It was also found that the increased amount of isocyanurate ring could result in reduced cell size, improved compressive strength, and lowered thermal conductivity of PIR foam. The results from thermogravimetric analysis (TGA) and cone calorimeter (CONE) test revealed that the thermal stability and fire performance of PIR foam could be improved with the increased amount of isocyanurate ring. Furthermore, the CONE test indicated that the smoke production of PIR foam decreased approximately 51.7% in comparison to the reference polyurethane (PU) foam, and the SEM image of char morphology showed that the char of PIR foam was more compact than PU foam.

Oxidation of dexamethasone in an aqueous suspension by air during prolonged storage produces the 17alpha-formyloxy-17beta-carboxylic acid 4. A pathway to 4 is proposed that involves Baeyer-Villiger-type oxidation of keto aldehyde 1 to mixed anhydride 5, followed by intramolecular formyl transfer. Synthetically, acid 3 was reacted with N,N'-carbonyldiimidazole followed by triethylammonium formate in order to generate the transient anhydride 5 en route to an authentic sample of 4.

A series of novel C–N dual-doped Cr2O3 photocatalysts were synthesized from MIL-101(Cr), using a two-step method, including initial carbonization in nitrogen atmosphere without adding any carbon source and subsequent calcination in air.

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