Banca de DEFESA: ANTÔNIO MARCELO SILVA LOPES

Uma banca de DEFESA de DOUTORADO foi cadastrada pelo programa.
STUDENT : ANTÔNIO MARCELO SILVA LOPES
DATE: 02/10/2025
TIME: 14:00
LOCAL: videoconferência
TITLE:

Catalytic conversion of blonde glycerin into acrolein and allyl alcohol using Nb₂O₅/SiO₂ and Fe₂O₃/Nb₂O₅-SiO₂ based solids.

KEY WORDS:

Blonde glycerin; Nb₂O₅/SiO₂ catalysts; Acrolein; Allyl alcohol; Fe₂O₃; Stability

PAGES: 135
BIG AREA: Ciências Exatas e da Terra
AREA: Química
SUBÁREA: Físico-Química
SPECIALTY: Cinética Química e Catálise
SUMMARY:

Blonde glycerin, obtained by simple pretreatment of crude glycerol, represents an alternative to conventional purification, adding value to the biodiesel production chain. Nb₂O₅/SiO₂ catalysts were synthesized via the Pechini method for the catalytic conversion of blonde glycerin into acrolein. A preliminary study evaluated the effect of niobium content and calcination temperature on the dehydration of refined glycerol at 250 °C (10% w/w solution). Among the samples, 15NbSi500 (15% Nb, calcined at 500 °C) stood out for its high surface area (255.9 m²·g⁻¹), large pore volume and distribution (13 nm and 0.83 cm³·g⁻¹), high acid site concentration (4.30 μmol·m⁻²), and higher L/B ratio, factors essential for reducing coke formation. After 600 min, this catalyst achieved 77% glycerol conversion and 84% acrolein selectivity, maintaining 62% conversion and 75% selectivity with blonde glycerin after three reuse and regeneration cycles. Subsequently, hematite (Fe₂O₃) was incorporated by incipient wetness impregnation; the sample containing 12% Fe₂O₃ (12Fe solid) reached 92% conversion and 26% selectivity to allyl alcohol with refined glycerol. This performance was attributed to a balance between moderate total acidity (60.5 µmol·g⁻¹), predominance of Lewis sites, high active phase dispersion, and favorable textural properties, including surface area of 243 m²·g⁻¹, pore volume of 0.61 cm³·g⁻¹, and average pore diameter of 12.8 nm, compatible with glycerol diffusion. A hydrogen transfer mechanism was proposed to explain selectivity toward allyl alcohol and reduced by-product formation. With blonde glycerin, 12Fe sample maintained 49% conversion and 26% selectivity after three cycles, confirming its stability, regenerability, and potential for industrial application under near-real conditions.

COMMITTEE MEMBERS:
Externo à Instituição - MAURICIO BRANDAO DOS SANTOS - UFBA
Interno - 350509 - ANTONIO SOUZA DE ARAUJO
Externo à Instituição - RÔMULO BATISTA VIEIRA - UNILAB
Externo à Instituição - THIAGO DE MELO LIMA - UFF
Presidente - 2087667 - TIAGO PINHEIRO BRAGA