Hydrodechlorination of Chlorobenzene Over Ni2P/SiO2 Catalysts: Influence of Ni2P Loading

Naphthalene Hydrogenation Saturation over Ni2P/Al2O3 Catalysts Synthesized by Thermal Decomposition of Hypophosphite

A series of Ni₂P/Al₂O₃ catalysts with different Ni₂P loadings were synthesized via thermal decomposition of hypophosphite and employed for naphthalene hydrogenation saturation. Results showed that Ni₂P loading greatly affected Ni₂P particle size and the number of active sites of the as-synthesized catalysts, which was derived from the variable interaction between POx and Al₂O₃. When the hydrogenation saturation reaction was performed at 300 °C, 4 MPa, a H₂/oil volume ratio of 600, and a liquid hourly space velocity (LHSV) of 3 h^-1, 98% naphthalene conversion and 98% selectivity to decalin were achieved over Ni₂P/Al₂O₃ catalysts with 10 wt % Ni₂P. The superior naphthalene hydrogenation saturation performance was ascribed to the large specific surface area (169 m²·g^-1), small Ni₂P particle size (3.8 nm), and the high number of exposed active sites (CO sorption 30 μmol·g^-1), which were beneficial to the adsorption and diffusion of the reactant molecules on the catalyst.

Novel thiotolerant catalysts for the on-board partial dehydrogenation of jet fuels

The possibility of producing on-board H₂ by dehydrogenation of petrol derivates is interesting for transport applications.

Hydrodechlorination of polychlorinated molecules using transition metal phosphide catalysts

Ni2P and CoP catalysts (5 wt.% of metal) supported on a commercial SiO2 were tested in the gas phase catalytic hydrodechlorination (HDCl) of mono (chlorobenzene-ClB) and polychlorobenzenes (PCBs) (1,2- dichlorobenzene (1,2-DClB), 1,3-dichlorobenzene (1,3-DClB), 1,4-dichlorobenzene (1,4-DClB), and 1,2,4-trichlorobenzene (1,2,4-TClB)) at atmospheric pressure. It was investigated how the number and position of chlorine atoms in the molecule influence the HDCl activity. The prepared catalysts were characterized by X-ray diffraction (XRD), CO chemisorption, N2 adsorption-desorption at -196°C, and X-ray photoelectron spectroscopy (XPS). Characterization results indicated better active phase dispersion and greater amount of P on the Ni2P catalyst surface. Catalytic results showed that the Ni2P was more active and stable in this type of reactions. The hydrodechlorination activity decreased by increasing the number of chlorine atoms in the molecule and chlorine substituents in close proximity. The observed trend in the HDCl activity was: ClB>1,4-DClB>1,3-DClB>1,2-DClB>1,2,4-TClB. The exception was the catalytic response after 24h on stream observed for the Ni2P in the HDCl reaction of 1,2,4-TClB, which was equal to that observed for the 1,4-DClB molecule, and also yielding benzene as the main reaction product.

Gas phase catalytic hydrodechlorination of chlorobenzene over cobalt phosphide catalysts with different P contents

The gas phase catalytic hydrodechlorination (HDC) of chlorobenzene (CB) at atmospheric pressure was investigated over silica-supported cobalt and cobalt phosphide catalysts containing different P loading and a fixed amount of cobalt (5 wt.%). The effect of the initial P/Co molar ratio on the stoichiometry of the cobalt phosphide phase, the acidity and the hydrogen activation capability were discussed and these properties correlated with the catalytic activity. Catalytic results indicated that the cobalt phosphide phase is much more active than the monometallic cobalt one. The activity raised with the P content present in the sample due to the formation of the CoP phase instead of the Co₂P one, which favored the formation of hydrogen spillover species, increased the amount of weak acid sites and the number of exposed superficial cobalt atoms probably related to a better dispersion of the active phase. All the catalysts gave rise benzene as the main reaction product.

Catalytic hydrodechlorination of chloroaromatic gas streams promoted by Pd and Ni: the role of hydrogen spillover

Catalytic hydrodechlorination (HDC) is an effective means of detoxifying chlorinated waste. Involvement of spillover hydrogen is examined in gas phase dechlorination of chlorobenzene (CB) and 1,3-dichlorobenzene (1,3-DCB) over Pd and Ni. The catalytic action of single component Pd and Ni, Pd/Al(2)O(3), Ni/Al(2)O(3) and physical mixtures with Al(2)O(3) has been considered. Catalyst activation is characterized in terms of temperature programmed reduction, the supported nano-scale metal phase by transmission electron microscopy and hydrogen/surface interactions by chemisorption/temperature programmed desorption. Pd/Al(2)O(3) generated significantly greater amounts of spillover hydrogen (by a factor of over 40) compared with Ni/Al(2)O(3). Hydrogen spillover on Pd/Al(2)O(3) far exceeded the chemisorbed component, whereas chemisorbed and spillover content was equivalent for Ni/Al(2)O(3). Inclusion of Al(2)O(3) with Ni and Ni/Al(2)O(3) increased spillover with an associated increase in specific HDC rate (up to a factor of 10) and enhanced selectivity to benzene from 1,3-DCB. HDC rate delivered by Pd and Pd/Al(2)O(3) was largely unaffected by the addition of Al(2)O(3). This can be attributed to the higher intrinsic HDC performance of Pd that results in appreciable HDC activity under conditions where Ni/Al(2)O(3) was inactive. Spillover was partially recovered (post TPD) for the Ni samples but the loss was irreversible in the case of Pd.

Alternative catalytic materials: carbides, nitrides, phosphides and amorphous boron alloys

Catalysts generated by the addition of carbon, nitrogen or phosphorus to transition metals have interesting properties and potential applications. The addition of carbon, nitrogen or phosphorus can lead to substantial modification of the catalytic efficacy of the parent metal and some carbides and nitrides are claimed to be comparable to noble metals in their behaviour. Amorphous boron transition metal alloys are also a class of interesting catalyst, although their structures and phase composition are more difficult to define. In this critical review, the preparation of these catalysts is described and brief details of their application given. To date, attention has largely centred upon the application of these materials as alternatives for existing catalysts. However, novel approaches towards their utilisation can be envisaged. For example, the extent to which it is possible to utilise the "activated" carbon and nitrogen species within the host lattices of carbides and nitrides, respectively, as a reactant remains largely unexplored (195 references).