The active use of transition metal phosphides in catalysis commenced at the beginning of the 2000s primarily in hydrodesulfurization and hydrodenitrogenation reactions. Owing to an increased interest in biomass-based feedstocks the intensive use of phosphides in hydrodeoxygenation reactions started in the first part of the 2010s. In earlier reviews devoted to phosphides, which were published before the 2010s, no information pertaining to hydrodeoxygenation is available. This review addresses monometallic phosphides of such transition metals as nickel, cobalt, molybdenum, and tungsten and covers their structure, synthesis, and properties. Transition metal phosphides are promising catalysts for hydroprocesses. They possess both metal active sites and acid sites, and, therefore, demonstrate activity not only in hydrogenation but in a number of acid-catalyzed processes. The review concerns the hydrodeoxygenation reactions of higher fatty acids and their esters; vegetable oils; and bio-oil and its model compounds. The hydrotreatment of vegetable oils and their derivatives over phosphides makes it possible to obtain hydrocarbons, which can be used as diesel fuel components or as a pure fuel. Using the hydrodeoxygenation of bio-oil model compounds catalyzed by phosphides partially or fully deoxygenated products may be obtained; however, the hydrotreatment of bio-oil itself did not provided positive results so far and calls for further research.

The annual production of plastic waste is a serious ecological problem as it causes substantial pollution of the environment. Polyethylene terephthalate, a material usually found in disposable plastic bottles, is one of the most popular material used for packaging in the world. In this paper, it is proposed to recycle polyethylene terephthalate waste bottles into benzene-toluene-xylene fraction using a heterogeneous nickel phosphide catalyst formed in situ during the polyethylene terephthalate recycling process. The catalyst obtained was characterized using powder X-ray diffraction, high-resolution transmission electron microscopy, and X-ray photoelectron spectroscopy techniques. The catalyst was shown to contain a Ni₂P phase. Its activity was studied in a temperature range of 250–400 °C and a H₂ pressure range of 5–9 MPa. The highest selectivity for benzene-toluene-xylene fraction was 93% at quantitative conversion.

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.

The development of catalysts for the hydrodeoxygenation of bio-based feedstocks is an important step towards the production of fuels and chemicals from biomass. This paper describes in situ-generated bulk molybdenum and tungsten oxides in the hydrodeoxygenation of the lignin-derived compound guaiacol. The catalysts obtained were studied using powder X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, high-resolution transition electron microscopy, diffuse reflectance infrared Fourier transform spectroscopy, and Raman spectroscopy. The use of metal carbonyls as precursors was shown to promote the formation of amorphous molybdenum oxide and crystalline tungsten phosphide under hydrodeoxygenation conditions. The catalysts’ activity was investigated under various reaction conditions (temperature, H₂ pressure, solvent). MoO_x was more active in the partial and full hydrodeoxygenation of guaiacol at temperatures of 200–380 °C (5 MPa H₂, 6 h). However, cyclohexane, which is an undesirable product, was formed in significant amounts using MoO_x (5 MPa H₂, 6 h), while WO_x was more selective to aromatics. When using dodecane as a solvent (380 °C, 5 MPa H₂, 6 h), the benzene-toluene-xylenes fraction was obtained with a 96% yield over the WO_x catalyst.