Phosphorus Catalysts

Phosphorus catalysts are widely used in organic chemistry laboratories to convert acetic acid and formaldehyde into acrylic acid or used to catalyze hydrodesulfurization (HDS) and hydrodenitrogenation (HDN). It also plays an important role in photocatalyst or electrocatalyst by combining phosphorus with carbon materials or other metals and metal derivatives such as TiO₂.

• Catalyst Used in Organic Chemistry Lab: Vanadium phosphorus oxide catalyst (VPO) can convert acetic acid and formaldehyde into acrylic acid for the conversion of oxidized butane to maleic anhydride or for certain condensation reactions. Various metal (Zr, Zn, Ni, Nb, Mo, Mn, Fe, Cu, Cr, Ce and Co) were used to dope VPO catalysts. Because of the changes in deped VPO catalysts, such as redox properties, catalytic performance and particle size, these catalysts showed significantly different performance compared with typical VPO catalysts.

Phosphorus reacts with most elements of the periodic table to form a diverse class of compounds known as phosphides. The catalysts are mainly based on transition metal phosphides catalyst which can be used to catalyze hydrodesulfurization (HDS) and hydrodenitrogenation (HDN). The below reaction sequence (Figure. 2) describes how the Ni-P catalyst affects the major observations on the reaction, i.e. the occurrence of an S_N2 step and the involvement of a piperidinium ion intermediate.

Figure 1. Crystal structure of transition metal phosphides

Figure 2. Mechanism of hydrodenitrogenation (HDN) of heterocyclic nitrogen catalyzed by Ni-P catalyst

• Catalyst based on Black Phosphorus: As a new two-dimensional material, black phosphorus (BP) has extraordinary catalytical properties because of its unique electronic, optical, and structural properties. Due to its advanced electrocatalytic properties, BP supported by thin film (BP-Ti) can catalyze the oxygen evolution reaction (OER). The OER activity of this catalyst can be developed by designing the BP grown on a carbon nanotube network (BP-CNT). In addition, a combination of two-dimensional (2D) black phosphorus (BP) and graphitic carbon nitride (CN) was designed and used as a metal-free photocatalyst. This new photocatalyst meets the requirement of green chemistry because it is a metal-free photocatalyst. During the irradiation of BP/CN in water with >420 and >780 nm light, H₂ gas was produced, respectively. The Figure.3 depicts how the photocatalyst works. Due to the interfacial interaction between BP and CN, enhanced photocatalytic performance is achieved and efficient charge transfer occurs. Moreover, the BP@TiO₂ hybrid photocatalysts provide enhanced photo-catalytic performance under light irradiation in the environmental and biomedical fields.

Figure 3

• Phosphorus-Doped Graphite Layers: The P-doped graphite layers were prepared by pyrolysis of toluene and triphenylphosphine. P-doped graphite—a typical metal-free catalyst—shows high electrocatalytic activity, long-term stability, and excellent tolerance to cross-over effects of methanol in the oxygen reduction reaction, which plays an important role in electrochemical conversion in fuel cells, in an alkaline medium.

References

1. Neher, H. T.; Kelton, S. C. (1952) 'Preparation of Acrylic Esters'. U.S.Patent 2582911.
2. Nagaki, D.; Weiner, H.; Chapman, J. T.; Scates, M. O.; Locke, A. S.; Peterson, C. J. (2012) "Catalysts for Producing Acrylic Acids and Acrylates." U.S. Patent 2012/0289743.
3. Zhu, Yun‐Pei, et al. (2015) 'Direct Synthesis of Phosphorus‐Doped Mesoporous Carbon Materials for Efficient Electrocatalytic Oxygen Reduction.', ChemCatChem, 7.18, 2903-2909.