Highly Active and Stable Ni–SiO₂Prepared by a Complex-Decomposition Method for Pressurized Carbon Dioxide Reforming of Methane

Abstract

A series of Ni−SiO 2 catalysts was synthesized by the complex-decomposition method using different amino acids as complexing agents and fuels and nickel nitrate and tetraethoxysilane as precursors of Ni and SiO 2 , respectively. For comparison, ammonium hydroxide and acetic acid were also used as complexing agents and fuels. Characterization by XRD, TEM, and N 2 adsorption−desorption at low temperature indicated that the structural and textural properties of the Ni−SiO 2 catalysts were strongly dependent on the complexing agent used. The dispersion of metallic Ni was increased by optimizing the complexing agent used. As revealed from H 2 -TPR patterns, Ni−SiO 2 exhibited significantly different interactions between Ni and SiO 2 , the extent of which was influenced by the complexing agent used. The Ni−SiO 2 catalysts were comparatively evaluated for carbon dioxide reforming of methane (CDR) under the following conditions: CH 4 /CO 2 = 1.0, T = 750°C, GHSV = 53200 mL· g −1 ·h −1 , and P = 1.0 atm. The results indicate that the Ni−SiO 2 materials prepared with glycine, alanine, serine, threonine, valine, and proline exhibited much higher activity and stability for CDR under atmospheric conditions than those prepared with lysine, acetic acid, and ammonium hydroxide. Moreover, the Ni−SiO 2 material prepared with glycine was also tested at elevated pressures of 5.0 and 10.0 atm. The effect of pressure on the CDR performance was investigated. Importantly, a highly active and stable Ni−SiO 2 material for pressurized CDR was obtained by tailoring the structure of Ni−SiO 2 and adjusting the interactions between Ni and SiO 2 by selecting the complexing agent. Thus, the main factors determining catalyst activity and stability for CDR were clearly revealed.

A High-Performance Ni/SiO2 Prepared by the Complexed-Impregnation Method with Citric Acid for Carbon Dioxide Reforming of Methane

“…As shown in Figure 1, all samples exhibited similar diffraction peaks, and in particular, the diffraction peak at 2θ ≈ 23°was attributed to amorphous silica species. 35 Moreover, the diffraction peaks at 2θ = 37°, 43°, 63°, 75°, and 79°can be ascribed to the (111), ( 200), (220), (311), and (222) planes of cubic NiO, 26,27 suggesting that the crystal morphology of the sample did not change when prepared with or without citric acid. However, for the intensity of diffraction peaks, obvious differences showed for Ni/SiO 2 and Ni−C/SiO 2 .…”

“…For the supported Ni catalyst, a lower dispersion of Ni is the obstacle for CDR. Liu and co-workers 26,27 observed that Ni dispersion was significantly promoted by complexation of the Ni 2+ with various complexants. Moreover, many organic ligands, such as acetic acid, ethylenediamine, or L-arginine, were added as a complexant in the process of Ni impregnation.…”

“…For the supported Ni catalyst, a lower dispersion of Ni is the obstacle for CDR. Liu and co-workers , observed that Ni dispersion was significantly promoted by complexation of the Ni 2+ with various complexants. Moreover, many organic ligands, such as acetic acid, ethylenediamine, or l -arginine, were added as a complexant in the process of Ni impregnation. − Because it is cheap and less toxic, citric acid was also used as a complexant for synthesis of high-dispersion metal catalysts, which were mainly used as hydrodesulfurization (HDS) catalysts. , Recently, citric acid was a complexant to improve Ni dispersion for CO methanation and reforming of CH 4 , but the effect of the amount of citric acid and the origin of the high dispersion of Ni were not reported. ,, …”

Oxidative CO 2 reforming of methane over stable and active nickel-based catalysts modified with organic agents

“…8) showed Ni2p 3/2 peak was centered at 854.2 eV and accompanied by an uptake satellite peak at 860 eV for each sample, which was the typical characteristic peak for Ni 0 . Compared with the standard binding energy (BE) of Ni 0 at 852 ± 0.4 eV [63], all of the Ni 2p BEs of spent catalysts were shifted to higher values. This shift indicated that the interactions between Ni species and support species were significantly enhanced during the reforming process [64].…”

Synthesis Gas Production via Dry Reforming of Methane over Manganese Promoted Nickel/Cerium–Zirconium Oxide Catalyst

“…For the DRM reaction, nickel based catalysts were more practical in industry because of their cost effectiveness compared to noble metals. − However, nickel based catalysts suffered from deactivation due to deposited carbon and Ni sintering in the DRM process. − In addition, several side reactions occurred on Ni-based catalysts, such as CH 4 decomposition, CO disproportionation, a reverse water gas shift reaction (RWGS, CO 2 + H 2 → CO + H 2 O, Δ H 298K = 41.19 kJ mol –1 ), and so on, which led to the result that the H 2 /CO ratio of the final products was not equal to 1. − Among them, RWGS was usually considered the most responsible for the results that the H 2 /CO obtained was usually less than 1. − …”