As-synthesised and reconstructed NH4-Al-dawsonite and NH4-Ga-dawsonite, and the materials obtaine... more As-synthesised and reconstructed NH4-Al-dawsonite and NH4-Ga-dawsonite, and the materials obtained by thermal treatment in the range 373873K, were studied as heterogeneous catalysts for the epoxidation of cyclooctene with hydrogen peroxide at ...
The transesterification of ethylene carbonate with methanol to dimethyl carbonate, an alternative... more The transesterification of ethylene carbonate with methanol to dimethyl carbonate, an alternative phosgene-free route to DMC, was investigated over aluminas derived from calcination at different temperatures of Na- and NH4-dawsonites. The influence of the monovalent cation (NH4+, Na+) on the thermal decomposition of the starting dawsonites and derived crystallinity, morphology and porosity of the resulting aluminates was studied. The physico-chemical properties of the dawsonite precursors and the derived oxides were characterized by ICP, in situ XRD, TGA-MS, TEM, N2 adsorption, FTIR, and 27Al MAS-NMR. Phase transitions during thermal decomposition are dependent on the monovalent cation in the original dawsonite, i.e. the NH4-counterpart is transformed into finely dispersed and highly amorphous aluminas with well-developed porosity in the range 473–1073K, while Na-dawsonite exhibits an intermediate amorphous sodium-containing alumina phase at 523–773K, which crystallizes into sodium aluminate at 773–1073K. Tests were carried out in a parallel reactor system at 298–343K, methanol-to-ethylene carbonate ratios of 2–12, and 0.1–10wt.% catalyst amount. Tailoring the catalyst activation conditions is essential to optimize the transesterification performance, and consequently the production of DMC, a valuable environment-friendly chemical for many potential applications. Any of the oxides derived from NH4-dawsonite were in active in the reaction. The basicity of the Na-containing oxides, attained by calcination of Na-dawsonite at 973K, is required to obtain an active catalyst, which rendered a maximum DMC yield ca. 65%. Recycling experiments demonstrated that activated dawsonites can be successfully reused.
As-synthesised and reconstructed NH4-Al-dawsonite and NH4-Ga-dawsonite, and the materials obtaine... more As-synthesised and reconstructed NH4-Al-dawsonite and NH4-Ga-dawsonite, and the materials obtained by thermal treatment in the range 373873K, were studied as heterogeneous catalysts for the epoxidation of cyclooctene with hydrogen peroxide at ...
The transesterification of ethylene carbonate with methanol to dimethyl carbonate, an alternative... more The transesterification of ethylene carbonate with methanol to dimethyl carbonate, an alternative phosgene-free route to DMC, was investigated over aluminas derived from calcination at different temperatures of Na- and NH4-dawsonites. The influence of the monovalent cation (NH4+, Na+) on the thermal decomposition of the starting dawsonites and derived crystallinity, morphology and porosity of the resulting aluminates was studied. The physico-chemical properties of the dawsonite precursors and the derived oxides were characterized by ICP, in situ XRD, TGA-MS, TEM, N2 adsorption, FTIR, and 27Al MAS-NMR. Phase transitions during thermal decomposition are dependent on the monovalent cation in the original dawsonite, i.e. the NH4-counterpart is transformed into finely dispersed and highly amorphous aluminas with well-developed porosity in the range 473–1073K, while Na-dawsonite exhibits an intermediate amorphous sodium-containing alumina phase at 523–773K, which crystallizes into sodium aluminate at 773–1073K. Tests were carried out in a parallel reactor system at 298–343K, methanol-to-ethylene carbonate ratios of 2–12, and 0.1–10wt.% catalyst amount. Tailoring the catalyst activation conditions is essential to optimize the transesterification performance, and consequently the production of DMC, a valuable environment-friendly chemical for many potential applications. Any of the oxides derived from NH4-dawsonite were in active in the reaction. The basicity of the Na-containing oxides, attained by calcination of Na-dawsonite at 973K, is required to obtain an active catalyst, which rendered a maximum DMC yield ca. 65%. Recycling experiments demonstrated that activated dawsonites can be successfully reused.
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Papers by Georgiana Stoica