In recent days, the applications of silica-based nanoparticles have gained much attention. The preparation of mesoporous silicas is usually achieved via the modified Stöber method, the reaction attained by the hy...In recent days, the applications of silica-based nanoparticles have gained much attention. The preparation of mesoporous silicas is usually achieved via the modified Stöber method, the reaction attained by the hydrolysis and condensation of silica precursors present within a medium containing template, solvent, deionized water (DI-W) and base. Therefore, the current study aimed to prepare and characterize mesoporous silicas by using tetramethoxysilane (TMOS) as silica precursor and ethylene glycol (Et-G) as solvent. The study was based on the template dodecyltrimethylammonium bromide (C<sub>12</sub>TMABr) and sodium hydroxide used as an alkaline agent. Mesoporous silicas were prepared in various batches based on TMOS molar concentration, ionized water, NaOH, and other solvents. The characterization of mesoporous silicas was achieved based on their specific surface area, pore size distribution and morphology using different instruments: Brunauer, Emmett & Teller (BET), scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FT-IR), and thermalgravimetric analysis (TGA). The study revealed that shape, average particle sizes “35 to 550 nm”, average pore radius “1.62 - 4.5 nm” and surface area “350 - 1204 m<sup>2</sup>·g<sup>-1</sup>” of obtained mesoporous silica particles were altered based on precursor concentration and other factors. Therefore, it is important to get the most suitable concentration of all chemicals in the preparation of mesoporous silicas to control the particle characteristics to use them upon their further applications. This is the baseline study that provides details regarding prepared silica particles with controlled characteristics, and more studies related to its applications are still in process.展开更多
Carbon-coated Ni,Co and Ni-Co alloy catalysts were prepared by the carbonization of the metal doped resorcinol-formaldehyde resins synthesized by the one-pot extended Stöber method.It was found that the introduct...Carbon-coated Ni,Co and Ni-Co alloy catalysts were prepared by the carbonization of the metal doped resorcinol-formaldehyde resins synthesized by the one-pot extended Stöber method.It was found that the introduction of Co remarkably reduced the carbon microsphere size.The metallic Ni,Co,and Ni-Co alloy particles(mainly 10-12 nm)were uniformly distributed in carbon microspheres.A charge transfer from Ni to Co appeared in the Ni-Co alloy.Compared with those of metallic Ni and Co,the d-band center of the Ni-Co alloy shifted away from and toward the Fermi level,respectively.In the in-situ aqueous phase hydrodeoxygenation of methyl palmitate with methanol as the hydrogen donor at 330℃,the decarbonylation/decarboxylation pathway dominated on all catalysts.The Ni-Co@C catalysts gave higher activity than the Ni@C and Co@C catalysts,and the yields of n-pentadecane and n-C6-n-C16 reached 71.6%and 92.6%,respectively.The excellent performance of Ni-Co@C is attributed to the electronic interactions between Ni and Co and the small carbon microspheres.Due to the confinement effect of carbon,the metal particles showed high resistance to sintering under harsh hydrothermal conditions.Catalyst deactivation is due to the carbonaceous deposition,and the regeneration with CO_(2) recovered the catalyst reactivity.展开更多
Porous carbon-encapsulated Ni and Ni-Sn intermetallic compound catalysts were prepared by the one-pot extended Stöber method followed by carbonization and tested for in-situ hydrothermal deoxygenation of methyl p...Porous carbon-encapsulated Ni and Ni-Sn intermetallic compound catalysts were prepared by the one-pot extended Stöber method followed by carbonization and tested for in-situ hydrothermal deoxygenation of methyl palmitate with methanol as the hydrogen donor.During the catalyst preparation,Sn doping reduces the size of carbon spheres,and the formation of Ni-Sn intermetallic compounds restrain the graphitization,contributing to larger pore volume and pore diameter.Consequently,a more facile mass transfer occurs in carbon-encapsulated Ni-Sn intermetallic compound catalysts than in carbonencapsulated Ni catalysts.During the in-situ hydrothermal deoxygenation,the synergism between Ni and Sn favors palmitic acid hydrogenation to a highly reactive hexadecanal that easily either decarbonylate to n-pentadecane or is hydrogenated to hexadecanol.At high reaction temperature,hexadecanol undergoes dehydrogenation-decarbonylation,generating n-pentadecane.Also,the C-C bond hydrolysis and methanation are suppressed on Ni-Sn intermetallic compounds,favorable for increasing the carbon yield and reducing the H_(2) consumption.The npentadecane and n-hexadecane yields reached 88.1%and 92.8%on carbon-encapsulated Ni_(3) Sn_(2) intermetallic compound at 330℃.After washing and H_(2) reduction,the carbon-encapsulated Ni_(3) Sn_(2) intermetallic compound remains stable during three recycling cycles.This is ascribed to the carbon confinement that effectively suppresses the sintering and loss of metal particles under harsh hydrothermal conditions.展开更多
文摘In recent days, the applications of silica-based nanoparticles have gained much attention. The preparation of mesoporous silicas is usually achieved via the modified Stöber method, the reaction attained by the hydrolysis and condensation of silica precursors present within a medium containing template, solvent, deionized water (DI-W) and base. Therefore, the current study aimed to prepare and characterize mesoporous silicas by using tetramethoxysilane (TMOS) as silica precursor and ethylene glycol (Et-G) as solvent. The study was based on the template dodecyltrimethylammonium bromide (C<sub>12</sub>TMABr) and sodium hydroxide used as an alkaline agent. Mesoporous silicas were prepared in various batches based on TMOS molar concentration, ionized water, NaOH, and other solvents. The characterization of mesoporous silicas was achieved based on their specific surface area, pore size distribution and morphology using different instruments: Brunauer, Emmett & Teller (BET), scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FT-IR), and thermalgravimetric analysis (TGA). The study revealed that shape, average particle sizes “35 to 550 nm”, average pore radius “1.62 - 4.5 nm” and surface area “350 - 1204 m<sup>2</sup>·g<sup>-1</sup>” of obtained mesoporous silica particles were altered based on precursor concentration and other factors. Therefore, it is important to get the most suitable concentration of all chemicals in the preparation of mesoporous silicas to control the particle characteristics to use them upon their further applications. This is the baseline study that provides details regarding prepared silica particles with controlled characteristics, and more studies related to its applications are still in process.
基金support from the National Natural Science Foundation of China(Grant Nos.21576193,21176177).
文摘Carbon-coated Ni,Co and Ni-Co alloy catalysts were prepared by the carbonization of the metal doped resorcinol-formaldehyde resins synthesized by the one-pot extended Stöber method.It was found that the introduction of Co remarkably reduced the carbon microsphere size.The metallic Ni,Co,and Ni-Co alloy particles(mainly 10-12 nm)were uniformly distributed in carbon microspheres.A charge transfer from Ni to Co appeared in the Ni-Co alloy.Compared with those of metallic Ni and Co,the d-band center of the Ni-Co alloy shifted away from and toward the Fermi level,respectively.In the in-situ aqueous phase hydrodeoxygenation of methyl palmitate with methanol as the hydrogen donor at 330℃,the decarbonylation/decarboxylation pathway dominated on all catalysts.The Ni-Co@C catalysts gave higher activity than the Ni@C and Co@C catalysts,and the yields of n-pentadecane and n-C6-n-C16 reached 71.6%and 92.6%,respectively.The excellent performance of Ni-Co@C is attributed to the electronic interactions between Ni and Co and the small carbon microspheres.Due to the confinement effect of carbon,the metal particles showed high resistance to sintering under harsh hydrothermal conditions.Catalyst deactivation is due to the carbonaceous deposition,and the regeneration with CO_(2) recovered the catalyst reactivity.
文摘Porous carbon-encapsulated Ni and Ni-Sn intermetallic compound catalysts were prepared by the one-pot extended Stöber method followed by carbonization and tested for in-situ hydrothermal deoxygenation of methyl palmitate with methanol as the hydrogen donor.During the catalyst preparation,Sn doping reduces the size of carbon spheres,and the formation of Ni-Sn intermetallic compounds restrain the graphitization,contributing to larger pore volume and pore diameter.Consequently,a more facile mass transfer occurs in carbon-encapsulated Ni-Sn intermetallic compound catalysts than in carbonencapsulated Ni catalysts.During the in-situ hydrothermal deoxygenation,the synergism between Ni and Sn favors palmitic acid hydrogenation to a highly reactive hexadecanal that easily either decarbonylate to n-pentadecane or is hydrogenated to hexadecanol.At high reaction temperature,hexadecanol undergoes dehydrogenation-decarbonylation,generating n-pentadecane.Also,the C-C bond hydrolysis and methanation are suppressed on Ni-Sn intermetallic compounds,favorable for increasing the carbon yield and reducing the H_(2) consumption.The npentadecane and n-hexadecane yields reached 88.1%and 92.8%on carbon-encapsulated Ni_(3) Sn_(2) intermetallic compound at 330℃.After washing and H_(2) reduction,the carbon-encapsulated Ni_(3) Sn_(2) intermetallic compound remains stable during three recycling cycles.This is ascribed to the carbon confinement that effectively suppresses the sintering and loss of metal particles under harsh hydrothermal conditions.
