Efecto de soportes híbridos en la eficiencia de catalizadores basados en Ni para aplicaciones catalíticas.
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Date
2025
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Publisher
Universidad de Concepción
Abstract
La anilina es un compuesto químico de gran importancia para la industria, especialmente como intermediario en la síntesis de productos farmacéuticos. Su producción se realiza principalmente mediante la hidrogenación catalítica de nitrobenceno, empleando catalizadores basados en metales nobles. No obstante, en los últimos años ha crecido el interés en usar metales no nobles como el níquel por su buen rendimiento y menor costo. Un aspecto clave en la eficiencia del catalizador es la naturaleza del soporte, ya que influye directamente en la dispersión y estabilidad. En este contexto, los soportes híbridos —que combinan las propiedades de materiales inorgánicos y orgánicos— han despertado interés debido a los efectos sinérgicos que pueden aportar. Por ello, el presente trabajo propone estudiar el efecto de este tipo de soportes en la hidrogenación selectiva de nitrobenceno.
En este trabajo se sintetizaron catalizadores de níquel sobre soportes orgánico (Biochar), inorgánico (SiO2) e híbridos mediante impregnación húmeda seguido de tratamientos térmicos de pirólisis y reducción. Las propiedades fisicoquímicas, morfológicas y superficiales de los catalizadores se caracterizaron mediante técnicas como TGA, TPR-H2, TGA-MS, adsorción de N2, SEM, XRD y FT-IR. La actividad catalítica se evaluó en la reacción de hidrogenación de nitrobenceno llevada a cabo en un reactor batch a 100°C, 20 bar de H2, 700 rpm de agitación y durante 5 horas.
Los resultados indicaron que los soportes híbridos presentaron una mayor funcionalización superficial y los catalizadores preparados sobre ellos mostraron una reducción del Ni a menor temperatura. En cuanto a los resultados cinéticos, se tiene que el catalizador Ni/SiO2-H muestra el mejor rendimiento en la reacción, llegando a un 100% de conversión en 3 horas, superando el rendimiento de los catalizadores con soporte tradicional. Además, los datos cinéticos revelaron un comportamiento de orden cero respecto al nitrobenceno, sugiriendo una saturación de la superficie del catalizador. Asumiendo este comportamiento cinético, se calcularon los parámetros cinéticos, donde el catalizador Ni/SiO2-H tiene la mayor TOF (0,119 s-1). La estabilidad se evaluó mediante pruebas de reciclo, identificándose una pérdida de actividad atribuida principalmente a la oxidación del níquel.
Este trabajo demostró que la incorporación de soportes híbridos orgánico-inorgánicos en catalizadores de níquel mejora sus propiedades estructurales y catalíticas en la hidrogenación de nitrobenceno. Los catalizadores híbridos alcanzaron mayores velocidades de reacción y mejores estabilidades, confirmando el potencial de los soportes híbridos como plataformas versátiles para catalizadores activos y sostenibles en la síntesis de intermediarios farmacéuticos.
Aniline is a chemical compound of great industrial importance, particularly as an intermediate in the synthesis of pharmaceuticals. Its production is mainly carried out through the catalytic hydrogenation of nitrobenzene using noble metal-based catalysts. However, in recent years, there has been growing interest in using non-noble metals such as nickel, due to their good catalytic performance and lower cost. A key aspect of catalyst efficiency is the nature of the support, as it directly affects dispersion and stability. In this context, hybrid supports—combining the properties of inorganic and organic materials—have attracted attention due to the synergistic effects they can provide. Therefore, this work aims to study the effect of such supports on the selective hydrogenation of nitrobenzene. Nickel catalysts supported on organic (biochar), inorganic (SiO2), and hybrid materials were synthesized by wet impregnation followed by pyrolysis and reduction thermal treatments. Their physicochemical, morphological, and surface properties were characterized by TGA, H2-TPR, TGA-MS, N2 adsorption, SEM, XRD, and FT-IR. Catalytic activity was evaluated in the hydrogenation of nitrobenzene using a batch reactor at 100 °C, 20 bar H2, 700 rpm stirring, for 5 hours. The results indicated that hybrid supports exhibited higher surface functionalization, and catalysts prepared on them showed nickel reduction at lower temperatures. Kinetic studies revealed that the Ni/SiO2-H catalyst achieved the best performance, reaching 100% conversion in 3 hours, outperforming catalysts with traditional supports. Moreover, kinetic data showed a zero-order behavior with respect to nitrobenzene, suggesting surface saturation of the catalyst. Assuming this behavior, kinetic parameters were calculated, with Ni/SiO2-H displaying the highest TOF (0.119 s-1). Catalyst stability was assessed by recycling tests, showing activity loss mainly due to nickel oxidation. This work demonstrated that incorporating hybrid organic-inorganic supports into nickel catalysts improves their structural and catalytic properties in the hydrogenation of nitrobenzene. Hybrid-supported catalysts achieved higher reaction rates and better stability, confirming their potential as versatile platforms for active and sustainable catalysts in the synthesis of pharmaceutical intermediates.
Aniline is a chemical compound of great industrial importance, particularly as an intermediate in the synthesis of pharmaceuticals. Its production is mainly carried out through the catalytic hydrogenation of nitrobenzene using noble metal-based catalysts. However, in recent years, there has been growing interest in using non-noble metals such as nickel, due to their good catalytic performance and lower cost. A key aspect of catalyst efficiency is the nature of the support, as it directly affects dispersion and stability. In this context, hybrid supports—combining the properties of inorganic and organic materials—have attracted attention due to the synergistic effects they can provide. Therefore, this work aims to study the effect of such supports on the selective hydrogenation of nitrobenzene. Nickel catalysts supported on organic (biochar), inorganic (SiO2), and hybrid materials were synthesized by wet impregnation followed by pyrolysis and reduction thermal treatments. Their physicochemical, morphological, and surface properties were characterized by TGA, H2-TPR, TGA-MS, N2 adsorption, SEM, XRD, and FT-IR. Catalytic activity was evaluated in the hydrogenation of nitrobenzene using a batch reactor at 100 °C, 20 bar H2, 700 rpm stirring, for 5 hours. The results indicated that hybrid supports exhibited higher surface functionalization, and catalysts prepared on them showed nickel reduction at lower temperatures. Kinetic studies revealed that the Ni/SiO2-H catalyst achieved the best performance, reaching 100% conversion in 3 hours, outperforming catalysts with traditional supports. Moreover, kinetic data showed a zero-order behavior with respect to nitrobenzene, suggesting surface saturation of the catalyst. Assuming this behavior, kinetic parameters were calculated, with Ni/SiO2-H displaying the highest TOF (0.119 s-1). Catalyst stability was assessed by recycling tests, showing activity loss mainly due to nickel oxidation. This work demonstrated that incorporating hybrid organic-inorganic supports into nickel catalysts improves their structural and catalytic properties in the hydrogenation of nitrobenzene. Hybrid-supported catalysts achieved higher reaction rates and better stability, confirming their potential as versatile platforms for active and sustainable catalysts in the synthesis of pharmaceutical intermediates.
Description
Tesis presentada para optar al título de Ingeniero/a Civil Químico/a.
Keywords
Catalizadores, Anilinas, Nitrobencenos, Hidrogenación