Abstract
Performances of bimetallic catalysts (Ni-Co) supported on different acidic carriers (HZSM-5, HBeta, HY, ZrO2) and corresponding monometallic Ni catalysts in aqueous phase hydrodeoxygenation of phenol were compared in batch and continuous flow modes. The results revealed that the support acidity plays an important role in deoxygenation as it mainly controls the oxygen-removing steps in the reaction network. At the same time, sufficient hydrothermal stability of a solid catalyst is essential. Batch experiments revealed 10Ni10Co/HZSM-5 to be the best-performing catalyst in terms of conversion and cyclohexane yield. Complementary continuous runs provided more insights into the relationship between catalyst structure, efficiency and stability. After 24 h on-stream, the catalyst still reveals 100% conversion and a slight loss (from 100% to 90%) in liquid hydrocarbon selectivity. The observed alloy of Co with Ni increased dispersion and stability of Ni-active sites, and combination with HZSM-5 resulted in a well-balanced ratio of metal and acid sites which promoted all necessary steps in preferred pathways. This was proved by studies of fresh and spent catalysts using various characterization techniques (N2 physisorption, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM) and infrared spectroscopy of adsorbed pyridine (pyr-IR)).
Highlights
The major part of the presently consumed global energy is dependent on fossil fuels including oil, coal and natural gas
We have developed supported bimetallic Ni-Co catalysts
Ni-Co catalysts supported on HZSM-5, which stem from our previous studies on their performance in HDO of phenol in batch mode [48,50]
Summary
The major part of the presently consumed global energy is dependent on fossil fuels including oil, coal and natural gas. To reduce the dependence on fossil fuel, considering environmental concerns, renewable and sustainable energy is needed [2,3]. Renewability and CO2 neutrality, biomass appears to be an alternative and sustainable resource for transportation fuels. The use of first-generation biofuels such as bioethanol and biodiesel (FAME—Fatty Acid Methyl Ester) has been established around the world for blending of conventional gasoline or diesel fuel. The governments of many countries set ambitious goals to promote the use of renewable sources, e.g., the U.S Department of Energy has set a target to produce 20% of transportation fuel from biomass [4]
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