Hydrodeoxygenation of phenol using nickel phosphide catalysts. Study of the effect of the support

Upgrading of Pyrolysis Bio-Oil by Catalytic Hydrodeoxygenation, a Review Focused on Catalysts, Model Molecules, Deactivation, and Reaction Routes

Biomass can be converted into energy/fuel by different techniques, such as pyrolysis, gasification, and others. In the case of pyrolysis, biomass can be converted into a crude bio-oil around 50-75% yield. However, the direct use of this crude bio-oil is impractical due to its high content of oxygenated compounds, which provide inferior properties compared to those of fossil-derived bio-oil, such as petroleum. Consequently, bio-oil needs to be upgraded by physical processes (filtration, emulsification, among others) and/or chemical processes (esterification, cracking, hydrodeoxygenation, among others). In contrast, hydrodeoxygenation (HDO) can effectively increase the calorific value and improve the acidity and viscosity of bio-oils through reaction pathways such as cracking, decarbonylation, decarboxylation, hydrocracking, hydrodeoxygenation, and hydrogenation, where catalysts play a crucial role. This article first focuses on the general aspects of biomass, subsequent bio-oil production, its properties, and the various methods of upgrading pyrolytic bio-oil to improve its calorific value, pH, viscosity, degree of deoxygenation (DOD), and other attributes. Secondly, particular emphasis is placed on the process of converting model molecules and bio-oil via HDO using catalysts based on nickel and nickel combined with other active elements. Through these phases, readers can gain a deeper understanding of the HDO process and the reaction mechanisms involved. Finally, the different equipment used to obtain an improved HDO product from bio-oil is discussed, providing valuable insights for the practical application of this reaction in pyrolysis bio-oil production.

Air-Stable Ni Catalysts Prepared by Liquid-Phase Reduction Using Hydrosilanes for Reactions with Hydrogen

The liquid-phase reduction method for the preparation of metal nanoparticles (NPs) by the reduction of metal salts or metal complexes in a solvent with a reducing agent is widely used to prepare Ni NPs that exhibit high catalytic activity in various organic transformations. Intensive research has been conducted on control of the morphology and size of Ni NPs by the addition of polymers and long-chain compounds as protective agents; however, these agents typically cause a decrease in catalytic activity. Here, we report on the preparation of Ni NPs using hydrosilane (Ni-Si) as a reducing agent and a size-controlling agent. The substituents on silicon can control not only the size but also the crystal phase of the Ni NPs. The prepared Ni NPs exhibited high catalytic performance for the hydrogenation of unsaturated compounds, aromatics, and heteroaromatics to give the corresponding hydrogenated products in high yields. The unique feature of Ni catalysts prepared by the hydrosilane-assisted method is that the catalysts can be handled under air as opposed to conventional Ni catalysts such as Raney Ni. Characterization studies indicated that the surface hydroxide was reduced under the catalytic reaction conditions with H2 at around 100 °C and with the assistance of organosilicon compounds deposited on the catalyst surface. The hydrosilane-assisted method presented here could be applied to the preparation of supported Ni catalysts (Ni-Si/support). The interaction between the Ni NPs and a metal oxide support enabled the direct amination of alcohols with ammonia to afford the primary amine selectively.

Bulk Molybdenum and Tungsten Phosphides for Selective Phenol Production from Guaiacol

Bulk MoP and WP were investigated and compared in guaiacol hydrodeoxygenation to phenol. The catalysts obtained were studied by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and temperature-programmed desorption of NH₃ (NH₃-TPD) analyses. MoP was shown to be more active than WP. However, WP was more selective in phenol production. Guaiacol conversion using MoP was 90-98%. The highest selectivity for phenol was 66% (340 °C). By increasing the temperature to 380 °C, phenol selectivity decreased to 31%, while selectivity for cyclohexane increased to 29%. Thus, MoP was active not only in hydrodeoxygenation but also in hydrogenation. Guaiacol conversion over WP was 53-90%. The highest selectivity for phenol was 84% (380 °C). Hydrogenation products were also detected but with low selectivity. Thus, WP was active in the partial hydrodeoxygenation of guaiacol and was more suitable for the selective production of phenol than MoP. It was shown that after a 30 h recycling test, the activity of MoP did not decrease (1st and 5th cycle conversion value was 91%), while the activity of WP reduced (1st and 5th cycle conversion values were 81 and 64%, respectively). However, the activity of both catalysts at average conversion values decreased. Selectivity for phenol remained unaltered over both catalysts. It was supposed that catalyst activity decreased due to partial destruction of the crystalline phosphide phase and the surface phosphide oxidation to phosphate.

Hydrocracking of crude palm oil to a biofuel using zirconium nitride and zirconium phosphide-modified bentonite

In this study, bentonite modified by zirconium nitride (ZrN) and zirconium phosphide (ZrP) catalysts was studied in the hydrocracking of crude palm oil to biofuels. The study demonstrated that bentonite was propitiously modified by ZrN and ZrP, as assessed by XRD, FTIR spectroscopy, and SEM-EDX analysis. The acidity of the bentonite catalyst was remarkably enhanced by ZrN and ZrP, and it showed an increased intensity in the Lewis acid and Brønsted acid sites, as presented by pyridine FTIR. In the hydrocracking application, the highest conversion was achieved by bentonite-ZrN at 8 mEq g⁻¹ catalyst loading of 87.93%, whereas bentonite-ZrP at 10 mEq g⁻¹ showed 86.04% conversion, which suggested that there was a strong positive correlation between the catalyst acidity and the conversion under a particular condition. The biofuel distribution fraction showed that both the catalysts produced a high bio-kerosene fraction, followed by bio-gasoline and oil fuel fractions. The reusability study revealed that both the catalysts had sufficient conversion stability of CPO through the hydrocracking reaction up to four consecutive runs with a low decrease in the catalyst activity. Overall, bentonite-ZrN dominantly favored the hydrocracking of CPO than bentonite-ZrP.

In this study, bentonite modified by zirconium nitride (ZrN) and zirconium phosphide (ZrP) catalysts was studied in the hydrocracking of crude palm oil to biofuels.

Unexpected sintering of small supported Ni2P under real feed conditions

2 nm well dispersed supported nickel phosphides have been made using hypophosphorous acid in the presence of organic components.