RESUMEN
The effect of the sulfur and metal-type content of MoP-S/γ-Al2O3-MgO, NiMoP-S/γ-Al2O3-MgO, and NiP-S/γ-Al2O3-MgO phosphide on hydroprocessing (HDO, HDCx-HDCn, HCK, HYD, and HYG) of fatty acids was studied. The catalysts were characterized by XRF, XRD, textural properties, XPS, Raman, Py-TPD, and EDS elemental mapping. The chemical analyses by X-ray fluorescence (XRF), EDS elemental mapping, and CHNS-O elemental analysis showed stoichiometric values Al/Mg = 38-40, Mo:Ni:P â¼ 1, and S ≤ 4.5 wt % (this value means that the molar ratio Mo:S â¼ 1.0:1.6, i.e., MoS2); also EDS elemental mapping confirmed the presence of Mo, Ni, Al, O, P, Mg, and S with good distribution on Al2O3-MgO. The impregnation of metals leads to a decrease in the surface area and pore volume as follows NiMoP-S/γ-Al2O3-MgO < MoP-S/γ-Al2O3-MgO < NiP-S/γ-Al2O3-MgO < Al2O3-MgO < Al2O3 (unimodal pore size distribution), propitiating a pseudo bimodal pore size distribution with Dp-BJH between â¼5-7 nm and 11.8-14.2 nm for the presence of MgO. XRD confirmed differences between metallic phosphates and phosphides, and XPS confirmed the presence at the surface of Moδ+(0 < δ+ < 2), Mo4+, Mo6+, Niδ+(0 < δ+ < 2), Ni2+, S2-, SO4 2-, Pδ+, and P5+ species. Raman revealed the presence of MoS2 only in MoP-S/γ-Al2O3-MgO and NiMoP-S/γ-Al2O3-MgO, while the NiMoP-S/γ-Al2O3-MgO catalyst had a more significant number of Brønsted and Lewis sites, although the increasing temperature decreased the Lewis sites. MoP-S/γ-Al2O3-MgO was more active at HDO showing the highest production rate for octadecane of 53 mol/(gcat·h), whereas NiP-S/γ-Al2O3-MgO was more active at HDCx-HDCn [45 mol/(gcat·h)] and HCK [6 mol/(gcat·h)]; meanwhile, NiMoP-S/γ-Al2O3-MgO had a mix of HDO [47 mol/(gcat·h)] and HDCx-HDCn [41 mol/(gcat·h)]. This showed production towards octadecane, heptadecane, and light hydrocarbons, meaning that the fatty acids were deoxygenated through bifunctional sites for hydrogenation (HYD) and hydrogenolysis (HYG) as follows: MoP-S/γ-Al2O3-MgO (K1 = 0.08 and K2 = 0.03 L/mol) < NiMoP-S/γ-Al2O3-MgO (K1 = 0.25 and K2 = 0.45 L/mol) < NiP-S/γ-Al2O3-MgO (K1 = 2.5 and K2 = 6.5 L/mol). For this reason, we considered that phosphide acts as a structural promoter with sulfur on its surface as a "mixed phosphidic-sulphidic species", allowing the largest generation of heptadecane and octadecane by the presence of BRIM sites for HYD and CUS sites for HYG.
RESUMEN
Resumen Gracias a su débil polaridad y gran área superficial, los soportes de carbón activado tienen el potencial de aumentar la dispersión de los sulfuros metálicos. La ausencia de una interacción fuerte metal-soporte puede conducir a la formación de una fase Ni-Mo-S muy activa y estable. En este estudio se prepararon catalizadores por el método de co-impregnación, con diferentes cantidades de níquel y molibdeno y soportados sobre carbón activado comercial, y se caracterizaron por técnicas BET, XRF y SEM. Se evaluó su actividad catalítica para el hidroprocesamiento de aceite de Jatropha utilizando un reactor por lotes, y se determinó la composición de los productos líquidos y gaseosos. Los resultados mostraron que los productos gaseosos están compuestos principalmente de grandes cantidades de propano y pequeñas cantidades de otros hidrocarburos livianos (C1 a C5). Los hidrocarburos líquidos fueron principalmente una mezcla de n-parafinas de C15-C18 y de algunos compuestos oxigenados. Los catalizadores presentaron una fracción de masa de 3 % Ni, 15 % Mo (Ni3Mo15/AC) y mayor selectividad hacia hidrocarburos C17-C18, con una distribución de productos similar al catalizador Ni-Mo-S soportado en alúmina comercial.
Abstract Due to their weak polarity and large surface area, activated carbon supports have the potential to enhance the dispersion of metal-sulfides. It is expected that the absence of a strong metal-support interaction can result in the formation of a very active and stable Ni-Mo-S phase. In this study, catalysts with different amounts of nickel and molybdenum supported on a commercial activated carbon were prepared by a co-impregnation method and characterized by BET, XRF, and SEM techniques. The catalytic activity for hydroprocessing of Jatropha oil was evaluated in a batch reactor, and the composition of the liquid and gaseous products were determined. Results showed that gaseous products are mainly composed of high amounts of propane and small amounts of other light hydrocarbons (C1 to C5). Liquid hydrocarbon products consisted of a mixture containing mainly n-paraffins of C15-C18 and some oxygenated compounds. The catalysts with a mass fraction of 3 % Ni, 15 % Mo (Ni3Mo15/AC) presented the highest selectivity toward C17-C18 hydrocarbons, with a product distribution similar to a commercial alumina-supported Ni-Mo-S catalyst.
Resumo Devido a sua baixa polaridade e amplia área superficial, os suportes de carvão ativado possuem o potencial de aumentar a dispersão de sulfetos metálicos. A ausência de uma forte interação suporte-metal pode levar a formação de uma fase Ni-Mo-S muito ativa e estável. Neste estudo, foram preparados catalizadores com diferentes teores de níquel e molibdênio suportados em carvão ativado comercial por um método de co-impregnação e caracterizados pelas técnicas BET, XRF e SEM. A atividade catalítica foi avaliada para o hidroprocessamento do óleo de Jatropha em um reator por lotes, e se determinou a composição dos produtos líquidos e gasosos. Os resultados mostraram que os produtos gasosos são compostos principalmente por altos teores de propano e pequenos teores de outros hidrocarbonos leves (C1-C5). Os hidrocarbonos líquidos consistiram de uma mistura contendo principalmente n-parafinas de C15-C18 e alguns compostos oxigenados. Os catalizadores apresentaram uma fração de massa de 3 % Ni, 15 % Mo (Ni3Mo15/AC) e uma maior seletividade em relação aos hidrocarbonos C17-C18, com uma distribuição de produtos similar ao catalizador comercial Ni-Mo-S suportado em alumina.