Abstract
The present work studied the stability and reusability of Ni/Al-Fe catalyst in the aqueous phase hydrogenolysis of glycerol without external hydrogen addition. The catalyst based on 28 molar % of Ni with 3/1 molar ratio of Al/Fe was prepared through co-precipitation. This catalyst presented the best performance in our last study which compares several Ni/Al-Fe catalysts with different molar ratios of Al/Fe. To see the influence of the pressurized water on the physicochemical characteristics of Ni/Al-Fe catalyst, a test of up to 9 h has been carried out. Fresh and used catalysts were characterized by various techniques: X-ray Diffraction (XRD), N2-physisorption, field emission scanning electron microscopy (FESEM) and STEM. Glycerol conversion and carbon yield to gases and liquids did not vary significantly when compared at 3 h and 9 h. Furthermore, the morphology of the catalyst remains stable after continuous recycling under severe hydrothermal conditions. The nickel rich phase of the catalyst, which was determined by XRD and scanning transmission electron microscopy (STEM) techniques, showed a stable size after 9 h under reaction.
Highlights
Nowadays, the production of biodiesel has been given considerable attention due to the growing concerns regarding environmental contamination and the depletion of existing fossil fuel reserves.Biodiesel is mainly produced by transesterification, where several triglycerides react with an alcohol such as methanol or ethanol in the presence of a catalyst
In our previous study [18], we showed that mixed-oxide catalysts (Ni/Alx Fey ) showed a better catalyst performance than the Ni/Al and Ni/Fe catalysts, with the Ni/Al3 Fe1 catalyst being the best for hydrogenolysis of glycerol
[18] for this type of catalyst used during 3 h of reaction. This means that the Ni/Al 3Fe1 catalyst is stable during 9 h of aqueous phase hydrogenolysis of glycerol, as was observed during the catalyst test and corroborated with the X-ray Diffraction (XRD) technique
Summary
The production of biodiesel has been given considerable attention due to the growing concerns regarding environmental contamination and the depletion of existing fossil fuel reserves. Catalysts 2020, 10, 1482 conversion and selectivity towards H2 production in comparison to the Ni/Al and Ni/Mg catalysts in the following order: Ni/Al2 Mg1 > Ni/Al1 Mg1 > Ni/Al1 Mg2 > Ni/Al > Ni/Mg. the results revealed that the mixed oxide supports had a good stability and activity in converting biomass into hydrogen through aqueous phase reforming of glycerol [21]. Fan et al [22] found that Mg-Al oxide supported Ni catalyst (Ni/Mg2 Al(O)), indicated higher activity at low reaction temperature and had a much better thermal stability (for 8 h of reaction duration at 700 ◦ C) than the Ni/MgO and Ni/Al2 O3 catalysts, respectively, for synthetic natural gas from syngas. Collected liquid products had a pH of around 4 as reported by
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