Search

Construction of coupled composite heterojunctions is an effective strategy for achieving high photocatalytic performance of SrTiO3(STO) perovskite. Herein, we synthesized Ag2O-STO heterostructure piezocatalysts using a simple one-step wet chemical method and evaluated its performance for full-spectrum photocatalytic degradation of toluene. Our findings reveal that the Ag2O-STO heterostructure demonstrates excellent catalytic activity, with a toluene conversion rate of 70%, which is 2.7 times that of STO. Furthermore, it showed good stability in five photocatalytic cycling experiments. The excellent catalytic performance of Ag2O-STO was attributed to the formation of p–n heterostructures, which induced the generation of a strong electrostatic field effect, providing a driving force for the transport of carriers and lowering the recombination or complexation rate, which could be confirmed by the photocurrent response. A possible mechanism of Ag2O-STO heterostructure is proposed. It is expected that this study can provide new understanding for the rational design of highly efficient photocatalysts for potential practical applications. [ABSTRACT FROM AUTHOR]

Studying the relationship between electronic structure and activity helps to understand the catalytic mechanism since the catalytic combustion is a redox reaction dominated by electron transfer. Herein, we regulated the electron energy and O p-band center of La-based perovskite catalysts by a facile method of changing the B-site ion (B = Co, Mn, Fe). The crystal structure, morphology, reducibility, element valence distribution, and catalytic properties of prepared catalysts were characterized. Combining with DFT calculation, it was found that the low electron energy in (110) facets of LaCoO3/SiO2 catalyst contributes to the formation of reactive oxygen species and high-valence Co3+ ions. The highest oxygen adsorption activation capacity of LaCoO3/SiO2 originates from a moderate location of the O p-band center with respect to the Fermi level. As expected, the LaCoO3/SiO2 sample shows higher n-butylamine oxidation activity than that of LaMnO3/SiO2 and LaFeO3/SiO2. This work provides different insights into understanding the activity of La-based perovskite catalysts for oxidation reactions. [ABSTRACT FROM AUTHOR]

The hierarchical porous ZSM-5 zeolites modified by the metal Mg and Ca (MH-ZSM-5) were constructed for catalytic coupling of CH3Cl to light-olefins (CMTO). The properties of the prepared catalysts were characterized by X-ray diffraction, N2 adsorption–desorption, scanning electron microscopy, Fourier-transform infrared spectroscopy and NH3 temperature-programmed desorption measurements. Results showed that the organosilane treatment could obviously change the morphology of ZSM-5 zeolites from cubic to sphere and introduce more mesoporous, and the metal modification could significantly reduce the amount of Brønsted acid. The mesoporous structure was in favor of mass transfer to avoid carbon deposits to prolong the lifetime of catalysts. In addition, the fewer strong acid sites could suppress the occurrence of side reactions to improve the selectivity of light olefins. Therefore, MH-ZSM-5 with the more mesoporous and appropriate acidity exhibited the best catalytic performance, among which the selectivity of light-olefins reached 90.9% and the lifetime (the duration of CH3Cl conversion > 98%) was up to 72 h. [ABSTRACT FROM AUTHOR]

The catalytic oxidation of volatile organic compounds (VOCs) is considered a feasible method for VOCs treatment by virtue of its low technical cost, high economic efficiency, and low additionally produced pollutants, which is of important social value. Single-atom catalysts (SACs) with 100% atom utilization and uniform active sites usually have high activity and high product selectivity, and promise a broad range of applications. Precise regulation of the microstructures of SACs by means of defect engineering, interface engineering, and electronic effects can further improve the catalytic performance of VOCs oxidation. In this review, we introduce the mechanisms of VOCs oxidation, and systematically summarize the recent research progress of SACs in catalytic VOCs total oxidation into CO2 and H2O, and then discuss the effects of various structural regulation strategies on the catalytic performance. Finally, we summarize the current problems yet to be solved and challenges currently faced in this field, and propose future design and research ideas for SACs in catalytic oxidation of VOCs. [ABSTRACT FROM AUTHOR]

An amorphous ZrO2 mesoporous material was prepared by propylene oxide (PO)-assisted sol-gel process and was first evaluated in CH4 oxychlorination. Various characterizations were conducted including XRD, N2 adsorption–desorption, NH3-TPD, CO2-TPD, SEM, and TEM. Results showed the amorphous ZrO2 with mesoporosity and large SSA exhibited abundant surface acid and base sites. As a non-redox catalyst, the amorphous ZrO2 unexpectedly delivered much higher activity and better stability in CH4 oxychlorination than conventional ZrO2. The CH4 conversion was 18.6% and the selectivity of CH3Cl and CO reached 47.6% and 30.2% at 490 °C, respectively. The amorphous ZrO2 could stably operate at 470 °C for 50 h without significant deactivation. Kinetic studies revealed that the CH4 activation on the surface of the amorphous ZrO2 was the rate-determining step. Highlights: An amorphous and mesoporous a-ZrO2 was prepared by propylene oxide-assisted sol-gel process. The a-ZrO2 catalyst unexpectedly delivered much higher activity and better stability in CH4 oxychlorination than conventional ZrO2. Reaction kinetics studies revealed that the CH4 activation on the catalyst surface was the rate-determining step. [ABSTRACT FROM AUTHOR]

Iron-doped mesoporous silica, Fe-MCM-41, with different concentrations of Lewis acidity have been prepared by the hydrothermal method. Physicochemical properties of all Fe-MCM-41 samples were obtained via HRTEM, PXRD and N2 sorption characterization. The surface acidities were tested by NH3-TPD. The catalytic activity of all Fe-MCM-41 materials were evaluated in the acidolysis reaction of benzyl chloride with various fatty acids. The corresponding benzaldehyde and acyl chloride product were synthesized in good conversion and high atom efficiency over the catalyst with the highest Fe content. [ABSTRACT FROM AUTHOR]

We report the catalytic property of sulfonated reduced graphene oxide (SOH-rGO) in the context of the additive esterification between carboxylic acids and olefins. The acid concentration in SOH-rGO can be modified during preparation, the SOH-rGO-5 at the optimal concentration of 2.66 mmol/g exhibits the highest catalytic activity in the additive reaction between acetic acid and isobutylene. The SOH-rGO can exhibit better catalytic activity than two benchmark porous catalysts such as sulfonated activated carbons (SOH-AC) and sulfonated SBA-15 (SOH-SBA). Specifically, the superior performance of SOH-SrGO observed for substrates with large steric hindrance (camphene and acrylic acid) suggests that its 2D sheet-like nanostructure can circumvent the mass transfer issue presented in conventional porous heterogeneous catalysts. [ABSTRACT FROM AUTHOR]

The dual-modified SBA-15 materials (A-S-Si) with Al ions inserting in the framework and −SOH groups grafting on the pore wall were prepared via a co-condensation method and characterized by a series of techniques. The characterization results implied that the A-S-Si samples have typically mesoporous structure and different acid properties. The catalytic performance of A-S-Si catalysts in the additive reaction of acetic acid with isobutene was studied. The results showed that the conversion of acetic acid strongly depended on the Brönsted acidity, while the selectivity of tert-butyl acetate (TBAC) was linear correlated with the ratio of Brönsted and Lewis acid amounts. The conversion of acetic acid could reach 72 % with the selectivity of TBAC as high as 97 % over A-S-Si with balanced Brönsted and Lewis acid under the optimal conditions. An additional advantage was that the dual-modified catalyst can be recycled and regenerate with good stability. [ABSTRACT FROM AUTHOR]

A novel strategy of carbonization and subsequent carboxylation in the confined mesopores of SBA-15 was implemented to synthesize meso-structured carbon/silica(C/Si) composites with enhanced acidity. The XRD and N sorption measurements suggested the preservation of ordered mesoporous structure; FTIR characterization indicated that the C/Sis were successfully modified with -COOH and the acidity of COOH-C/Si material was significantly enhanced. COOH- 30C/Si(A) with high COOH density of 2.61 mmol/g and retained mesoporous structure exhibited superior activity for dichlorohydrin production. Through the optimization of reaction variables, as high as 65.7 %, the yield of DCH, can be achieved over COOH- 30C/Si(A) after 12 h reaction under 130 °C. Meanwhile, it was 100 % that the conversion of the glycerol can be reached. A significant issue, good durability, especially for practical application, was verified through five consecutive cycles with the optimal reaction variables. [ABSTRACT FROM AUTHOR]

A set of propysulfonic acid modified mesostructured silica materials (SBA-15-SOH) were prepared by a convenient one-pot co-condensation method. Samples were characterized by XRD, FT-IR, Py-FTIR, N adsorption-desorption, elemental analysis and acid-base titration. The catalysts exhibited excellent activities and selectivities for addition esterification of acrylic acid and cyclohexene. The highest catalytic activity (82.8 %) and selectivity (92.6 %) were obtained over SBA-15-SOH (15 %). The efficient catalytic performance of SBA-15-SOH (15 %) was attributed to the high surface area, proper mesopore texture and presence of sulfonic acid groups in its structure. SBA-15-SOH catalyst was easily separated and recycled with high stability. [ABSTRACT FROM AUTHOR]