Propane dehydrogenation(PDH)has emerged as a key on-purpose technology for the production of propylene,but it often depends on toxic chromium and expensive platinum catalysts,highlighting the need for environmentally ...Propane dehydrogenation(PDH)has emerged as a key on-purpose technology for the production of propylene,but it often depends on toxic chromium and expensive platinum catalysts,highlighting the need for environmentally friendly and cost-effective alternatives.In this study,we developed a facile impregnation method to fabricate unsaturated Co single-atoms with a tricoordinated Co_(1)O_(3)H_(x) structure by regulating silanol nests in purely siliceous Beta zeolites.Detailed PDH catalytic tests and characterizations revealed a positive correlation between the presence of silanol nests and enhanced catalytic activity.Additionally,the unsaturated Co single-atoms exhibited a carbon deposition rate more than an order of magnitude slower than that of Co nanoparticles.Notably,the optimized Co_(0.3%)/deAl-meso-Beta catalyst achieved a record-high propylene formation rate of 21.2 mmol_(C3H6) g_(cat)^(-1) h^(-1),with an exceptional propylene selectivity of 99.1%at 550℃.Moreover,the Co_(0.3%)/deAl-meso-Beta catalyst demonstrated excellent stability,with negligible deactivation after 5 consecutive regeneration cycles.This study emphasizes the pivotal role of silanol nests of zeolites in stabilizing and modulating the coordination environment of metallic active sites,providing valuable insights for the design of high-activity,high-stability,and low-cost PDH catalysts.展开更多
The pathway of dehydrogenation reaction of silanol SiH3OH is investigated by ab initio Mo calculations using RHF/-31G basis set. The geometries of reactant, transition states and products are optimized on the singlet ...The pathway of dehydrogenation reaction of silanol SiH3OH is investigated by ab initio Mo calculations using RHF/-31G basis set. The geometries of reactant, transition states and products are optimized on the singlet potential energy surface of the ground state. The activation energies, reaction heats, statistical A factor and activation entropies are calculated. The vibrational analysis of the reactant and the transition states is made. The reaction crgodography along the intrinsic reaction coordinate (IRC) are performed to examine the reaction mechanism.展开更多
Design and preparation of highly efficient zeolite catalysts for gas-phase Beckmann rearrangement of cyclohexanone oxime to caprolactam are attractive but still challenging.Herein,we show a one-pot synthesis of silica...Design and preparation of highly efficient zeolite catalysts for gas-phase Beckmann rearrangement of cyclohexanone oxime to caprolactam are attractive but still challenging.Herein,we show a one-pot synthesis of silicalite-1 zeolite nanosheets with rich H-bonded silanols.The key to this success is the use of urea in the synthetic system.Catalytic tests of cyclohexanone oxime gas-phase Beckmann rearrangement show that the silicalite-1 zeolite nanosheets with H-bonded silanols exhibit higher selectivity for caprolactam and longer reaction lifetime than those of the conventional silicalite-1 zeolite.Theoretical simulations reveal that the ammonium decomposed by urea is a critical additive for the formation of H-bond silanols.Obviously,one-pot synthesis of silicalite-1 zeolite nanosheets with rich H-bonded silanols plus excellent catalytic performance in the Beckmann rearrangement offer a new opportunity for development of highly efficient zeolites for catalytic applications in the future.展开更多
Propane dehydrogenation(PDH)offers a promising route for on-demand propylene production,yet developing costeffective and durable non-noble metal catalysts remains challenging.Herein,we report a silanol(Si-OH)stabilize...Propane dehydrogenation(PDH)offers a promising route for on-demand propylene production,yet developing costeffective and durable non-noble metal catalysts remains challenging.Herein,we report a silanol(Si-OH)stabilized Zn catalyst supported on hierarchical self-pillared pentasil(SPP)zeolite,synthesized via the metal-ligand protection strategy under one-pot hydrothermal condition.The abundant isolated silanol groups on the SPP framework effectively anchor Zn^(2+) ions,forming highly dispersed subnanometric ZnO clusters confined within zeolite channels without forming bulk particles.Structural characterization(powder X-Ray diffraction(PXRD),Fourier transform infrared(FTIR),high-angle annular dark-field scanning transmission electron microscopy(HAADF-STEM),X-ray photoelectron spectroscopy(XPS))confirms the atomic-level dispersion of Zn species and their strong interaction with silanol defects.At an optimal Zn loading of 2.65 wt.%,the catalyst achieves 33.7%propane conversion with 92.7%propylene selectivity and a space-time yield of 179.9 mg·g^(−1)·h^(−1) at 550℃ under a weight hourly space velocity(WHSV)of 0.6 h^(−1).Remarkably,the catalyst retains>90%selectivity and recovers 80%initial activity after two regeneration cycles,attributed to minimized coke deposition(<0.3 wt.%)and suppressed Zn loss.Mechanistic studies reveal that silanol-mediated Zn stabilization optimizes propane C-H activation,while the hierarchical porosity of SPP enhances mass transport and coke resistance.This work underscores the critical role of support surface chemistry and architecture in designing robust propane dehydrogenation(PDH)catalysts,offering a viable pathway to replace conventional noble or toxic metal-based systems.展开更多
A novel method for scandium recovery is proposed through high-surface area silanol-rich silica sorbents which were prepared with calcium silicate hydrate(C-S-H) as raw material.Two types of silanol-rich silica particl...A novel method for scandium recovery is proposed through high-surface area silanol-rich silica sorbents which were prepared with calcium silicate hydrate(C-S-H) as raw material.Two types of silanol-rich silica particles,i.e.,LAC-S(silica derived from acid leaching of amorphous C-S-H) and LLC-S(silica derived from acid leaching of low-crystallinity C-S-H) are obtained after calcium ions are removed from both amorphous and low-crystallinity forms of C-S-H through a facile acid leaching process(3 mol/L,25℃,24 h).(29)^Si NMR spectroscopy reveals that the proportion of silicon atoms carrying silanol groups increases from less than 43% to over 80% when silica particles are transferred from a dry state to an aqueous solution.Batch adsorption experiments were conducted to evaluate the sorption performance and selectivity of these silica sorbents toward Sc(Ⅲ).The scandium sorption capacities of LAC-S and LLC-S at an equilibrium pH of 4.2 are 174.45 and 129.57 mg/g,respectively.The separation factors(SFSc/Ln) of both silica particles exceed 1000 in the initial pH range of 3.5-5.The loaded scandium ions are recovered with 3 mol/L hydrochloric acid and the sorbents exhibit good reusability.This strategy provides an efficient and green method for recovering scandium from aqueous solutions.展开更多
文摘Propane dehydrogenation(PDH)has emerged as a key on-purpose technology for the production of propylene,but it often depends on toxic chromium and expensive platinum catalysts,highlighting the need for environmentally friendly and cost-effective alternatives.In this study,we developed a facile impregnation method to fabricate unsaturated Co single-atoms with a tricoordinated Co_(1)O_(3)H_(x) structure by regulating silanol nests in purely siliceous Beta zeolites.Detailed PDH catalytic tests and characterizations revealed a positive correlation between the presence of silanol nests and enhanced catalytic activity.Additionally,the unsaturated Co single-atoms exhibited a carbon deposition rate more than an order of magnitude slower than that of Co nanoparticles.Notably,the optimized Co_(0.3%)/deAl-meso-Beta catalyst achieved a record-high propylene formation rate of 21.2 mmol_(C3H6) g_(cat)^(-1) h^(-1),with an exceptional propylene selectivity of 99.1%at 550℃.Moreover,the Co_(0.3%)/deAl-meso-Beta catalyst demonstrated excellent stability,with negligible deactivation after 5 consecutive regeneration cycles.This study emphasizes the pivotal role of silanol nests of zeolites in stabilizing and modulating the coordination environment of metallic active sites,providing valuable insights for the design of high-activity,high-stability,and low-cost PDH catalysts.
文摘The pathway of dehydrogenation reaction of silanol SiH3OH is investigated by ab initio Mo calculations using RHF/-31G basis set. The geometries of reactant, transition states and products are optimized on the singlet potential energy surface of the ground state. The activation energies, reaction heats, statistical A factor and activation entropies are calculated. The vibrational analysis of the reactant and the transition states is made. The reaction crgodography along the intrinsic reaction coordinate (IRC) are performed to examine the reaction mechanism.
文摘Design and preparation of highly efficient zeolite catalysts for gas-phase Beckmann rearrangement of cyclohexanone oxime to caprolactam are attractive but still challenging.Herein,we show a one-pot synthesis of silicalite-1 zeolite nanosheets with rich H-bonded silanols.The key to this success is the use of urea in the synthetic system.Catalytic tests of cyclohexanone oxime gas-phase Beckmann rearrangement show that the silicalite-1 zeolite nanosheets with H-bonded silanols exhibit higher selectivity for caprolactam and longer reaction lifetime than those of the conventional silicalite-1 zeolite.Theoretical simulations reveal that the ammonium decomposed by urea is a critical additive for the formation of H-bond silanols.Obviously,one-pot synthesis of silicalite-1 zeolite nanosheets with rich H-bonded silanols plus excellent catalytic performance in the Beckmann rearrangement offer a new opportunity for development of highly efficient zeolites for catalytic applications in the future.
基金supported by the National Key Research and Development Program of China(No.2021YFA1500503)the National Natural Science Foundation of China for Single-Atom Catalysis(No.22388102)+3 种基金the National Natural Science Foundation of China(Nos.22302218,22102210,22302199,22378079,and 21961142006)Natural Science Foundation of Shandong Province(No.ZR2024QB299)the Program for High-level Innovative Talents in Guizhou Province(No.GCC[2023]049)Energy Revolution Science and Technology Special Project(Joint Fund)of the Yulin Innovation Institute of Clean Energy(No.E411040316).
文摘Propane dehydrogenation(PDH)offers a promising route for on-demand propylene production,yet developing costeffective and durable non-noble metal catalysts remains challenging.Herein,we report a silanol(Si-OH)stabilized Zn catalyst supported on hierarchical self-pillared pentasil(SPP)zeolite,synthesized via the metal-ligand protection strategy under one-pot hydrothermal condition.The abundant isolated silanol groups on the SPP framework effectively anchor Zn^(2+) ions,forming highly dispersed subnanometric ZnO clusters confined within zeolite channels without forming bulk particles.Structural characterization(powder X-Ray diffraction(PXRD),Fourier transform infrared(FTIR),high-angle annular dark-field scanning transmission electron microscopy(HAADF-STEM),X-ray photoelectron spectroscopy(XPS))confirms the atomic-level dispersion of Zn species and their strong interaction with silanol defects.At an optimal Zn loading of 2.65 wt.%,the catalyst achieves 33.7%propane conversion with 92.7%propylene selectivity and a space-time yield of 179.9 mg·g^(−1)·h^(−1) at 550℃ under a weight hourly space velocity(WHSV)of 0.6 h^(−1).Remarkably,the catalyst retains>90%selectivity and recovers 80%initial activity after two regeneration cycles,attributed to minimized coke deposition(<0.3 wt.%)and suppressed Zn loss.Mechanistic studies reveal that silanol-mediated Zn stabilization optimizes propane C-H activation,while the hierarchical porosity of SPP enhances mass transport and coke resistance.This work underscores the critical role of support surface chemistry and architecture in designing robust propane dehydrogenation(PDH)catalysts,offering a viable pathway to replace conventional noble or toxic metal-based systems.
基金Project supported by the National Natural Science Foundation of China (52064002)Guangxi Science and Technology Major Project(AA23073018)。
文摘A novel method for scandium recovery is proposed through high-surface area silanol-rich silica sorbents which were prepared with calcium silicate hydrate(C-S-H) as raw material.Two types of silanol-rich silica particles,i.e.,LAC-S(silica derived from acid leaching of amorphous C-S-H) and LLC-S(silica derived from acid leaching of low-crystallinity C-S-H) are obtained after calcium ions are removed from both amorphous and low-crystallinity forms of C-S-H through a facile acid leaching process(3 mol/L,25℃,24 h).(29)^Si NMR spectroscopy reveals that the proportion of silicon atoms carrying silanol groups increases from less than 43% to over 80% when silica particles are transferred from a dry state to an aqueous solution.Batch adsorption experiments were conducted to evaluate the sorption performance and selectivity of these silica sorbents toward Sc(Ⅲ).The scandium sorption capacities of LAC-S and LLC-S at an equilibrium pH of 4.2 are 174.45 and 129.57 mg/g,respectively.The separation factors(SFSc/Ln) of both silica particles exceed 1000 in the initial pH range of 3.5-5.The loaded scandium ions are recovered with 3 mol/L hydrochloric acid and the sorbents exhibit good reusability.This strategy provides an efficient and green method for recovering scandium from aqueous solutions.
