As etapas de remoção dos templates de sílica, após a carbonização dos precursores orgânicos, no processo de obtenção dos carbonos mesoporosos ordenados mostrou-se uma etapa essencial para que a síntese desses carvões fosse realizada com sucesso. Ficou claro que o termo utilizado frequentemente na literatura, “lavagem”, não é aplicado maneira adequada. O termo “extração” é o mais adequado, pois colocamos o compósito carbono/sílica em solução de HF 5% ou NaOH 1 mol/L, e mais eficiente do que um processo de lavagem.
Em relação a solução utilizada para a extração do template, HF 5% ou NaOH 1 mol/L, ambas são eficientes e resultam em materiais bem ordenados e não influenciam nas características do material de carbono obtido. O uso do HF 5% pode ser considerado mais eficiente por necessitar de apenas uma etapa de extração, enquanto que o NaOH 1 mol/L necessita de duas etapas para remover o template de maneira eficiente.
Além da extração do template de sílica, a etapa de carbonização também é uma etapa importante para a obtenção dos carbonos mesoporosos ordenados. Como pôde ser observado, os materiais que tiveram contato com oxigênio durante a etapa de carbonização apresentaram tamanhos de mesoporosos de diferentes tamanhos, enquanto que os materiais que foram carbonizados em atmosfera de N2 apresentaram mesoporosidade uniforme.
Após a impregnação do MoO3 nos materiais mesoporosos, tanto de sílica como de carbono, observou-se uma diminuição significativa nos valores de área específica e no volume de poros, indicando que o MoO3 ficou localizado no interior dos poroso dos materiais. Pelas microscopias eletrônicas de transmissão, pode-se observar que alguns materiais apresentaram maior formação de aglomerados de MoO3, resultando no maior bloqueio dos poros e uma maior redução no valor da área desses materiais.
Quanto ao desempenho dos catalisadores nas reações de hidrodeoxigenação do fenol, o óxido de molibdênio suportado nas réplicas de carbono mesoporoso (CMK-3 e CMK-8) apresentaram resultados superiores em relação aos seus templates de sílica SBA- 15 e KIT-6. Esse fato ocorre, principalmente, pela formação de uma fase MoOxCy, ou seja, ocorre uma carburação parcial do catalisador MoO3.
O aumento da temperatura de pré-tratamento do óxido suportado também contribui em um melhor desempenho dos catalisadores pela formação de vacâncias de oxigênio, observado pela técnica de OSC.
92 As reações feitas realizadas com Mo2C suportado nos diferentes materiais sintetizados apresentou um desemprenho bem superior ao desemprenho apresentado pelo óxido suportado. Porém, o suporte e a carburação in situ ou ex situ não apresentou influência na reação de hidrodeoxigenação do fenol.
Todos os catalisadores apresentaram uma excelente seletividade ao benzeno, favorecendo a deoxigenação direta (DDO). Onde os maiores valores de conversão e seletividade foram encontrados nas reações utilizando Mo2C suportado nas réplicas de carvão mesoporosos.
93
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