How nitric oxide affects the decomposition of supported nickel nitrate to arrive at highly dispersed catalysts

Abstract

An explanation is put forward for the beneficial effect of thermal decomposition of supported Ni 3 (NO 3 ) 2 (OH) 4 in NO/He flow (0.1-1 vol%) that enables preparation of well-dispersed (3-5 nm particles) 24 wt% Ni-catalysts via impregnation and drying using aqueous [Ni(OH 2 ) 6 ](NO 3 ) 2 precursor solution. Moreover, combining electron tomography, XRD and N 2 -physisorption with SBA-15 support yielded a clear picture of the impact of air, He and NO/He gas atmospheres on NiO shape and distribution. TGA/MS indicated that NO 2 , N 2 O, H 2 O products evolved more gradually in NO/He. In situ XRD and DSC revealed that NO lowers the nitrate decomposition rate and appears less endothermic than in air supposedly due to exothermic scavenging of oxygen by NO, which is supported by MS results. The Ni/SiO 2 catalyst prepared via the NO-method displayed a higher activity in the hydrogenation of soybean oil as the required hydrogenation time decreased by 30% compared to the traditionally air calcined catalyst.

A Time‐Resolved In Situ Quick‐XAS Investigation of Thermal Activation of Fischer–Tropsch Silica‐Supported Cobalt Catalysts

“…Indeed, Table S2 (see the Supporting Information) shows that decomposition of cobalt nitrate in diluted NO at 240 8C results in smaller cobalt oxide particles, which is consistent both with our in situ EXAFS data ( Figure S7, the Supporting Information) and with previous reports by de Jong et al [9][10][11] Moreover, in contrast with Co-A C H T U N G T R E N N U N G (NO 3 ) 2 , nitrate ions, present in substoichiometry with respect to cobalt in hydroxynitrates, participate in the oxidation of cobalt and no dioxygen is produced during decomposition (compare Equations 2, 5 and 6). The brutal release of dioxygen has been reported to be detrimental to nickel oxide dispersion.…”

“…This can be achieved by optimizing catalyst texture, [3] adding organic compounds, [4] [5] or promoters [6] during catalyst preparation, decomposing cobalt nitrate in a glow discharge [7] or by controlling the catalyst thermal activation. [8,9,10,11] In particular, de Jong et al prepared smaller Co 3 O 4 and Co 0 particles on SBA-15 silicas by activating the catalyst in a NO-containing atmosphere instead of air prior to the reduction. [9,10,11] In the present paper, in situ quick X-ray absorption spectroscopy (QXAS) has been used as a unique tool to accurately monitor the transformations of dispersed phases in supported catalysts under different atmospheres (air, helium and 5 % NO/He), both from the structural, quantitative, and kinetic standpoints.…”

“…[8,9,10,11] In particular, de Jong et al prepared smaller Co 3 O 4 and Co 0 particles on SBA-15 silicas by activating the catalyst in a NO-containing atmosphere instead of air prior to the reduction. [9,10,11] In the present paper, in situ quick X-ray absorption spectroscopy (QXAS) has been used as a unique tool to accurately monitor the transformations of dispersed phases in supported catalysts under different atmospheres (air, helium and 5 % NO/He), both from the structural, quantitative, and kinetic standpoints. The time-resolved QXAS spectra were continuously collected at the Co K edge in the transmission mode during the catalyst activation.…”

Influence of copper on nickel-based catalysts in the conversion of glycerol

“…3b). The first peak is due to the decomposition of the Ni nitrate precursor to Ni in its oxidized state [30][31][32][33] while the second peak is attributed to the reduction of nickel oxide species to metallic Ni [34]. For monometallic Cu sample, the reduction peak between 500 and 550 K (Fig.…”

Copper Nitrate Redispersion To Arrive at Highly Active Silica-Supported Copper Catalysts

“…24, 29 We have previously reported that agglomeration of cobalt and nickel nitrate can effectively be prevented by replacing traditional air calcination with thermal treatment in 1% (v/v) NO/He flow, resulting in high NiO and Co 3 O 4 dispersions. 30,31 For silicasupported copper nitrate, it was reported that the drying step is of vital importance to the particle size distribution. 5 Drying at elevated temperatures resulted in agglomeration during the hydrolysis of copper nitrate hydrate to copper hydroxynitrate.…”