Catalysis Science & Technology最新文献

Cation exchange resins represent an important family of solid acid organic catalysts that have been used to convert different biobased feedstocks. In this context, cation exchange resins have been previously investigated in the synthesis of alkyl levulinates, an important biobased platform chemical, but obtained mainly from sugar-downstream chemicals such as levulinic acid or furfuryl alcohol. So far, their utilization as catalysts for the one-pot conversion of sugars to alkyl levulinates has hardly been investigated, this reaction being dominated by inorganic catalysts. One of the main reasons stems from their irreversible deactivation during the catalytic reaction. Although one previous article demonstrated that gel-type cation exchange resins were more prone to catalyzing this one-pot reaction, much less is known about their deactivation, a scientific obstacle which we study in this report. By assessing the impact of different reaction parameters on more than 13 different cation exchange resins, we discovered conditions for which it was possible to drastically limit the deposition of humins on cation exchange resins. In methanol, and under optimized conditions, we found that Purolite C124 SH exhibited the best catalytic performance, leading to methyl levulinate in 86% yield from fructose, and it can be successfully recycled 10 times without an apparent decrease in its catalytic efficiency.

AlF₃ and MgF₂ are important catalysts for fluorination processes. In this study we characterise structures consisting of either AlF₃, or MgF₂ supported over AlF₃, using Fourier transform infrared spectroscopy of surface absorbed CO. We interpret the results using atomic-scale density functional calculations, along with high-resolution electron microscopy and spectroscopy. By coupling theory to vibrational spectroscopy we are able to establish different stable facets in the host species, identifying both surface physisorbed CO binding to pristine facets, and chemisorbed CO binding to fluorine anion vacancy sites. In the case of MgF₂ supported over AlF₃ surfaces we suggest that a 50 : 50 mixed Mg–AlF_x monolayer surface phase can form. Excess MgF₂ deposition subsequently results in the formation of MgF₂ nanoparticles on the surface. Mixed composition surface phases may play a critical role in Al/MgF_x fluorine catalysis.

The rate processes occurring at catalytic surfaces are complicated by various factors, and the corresponding kinetic models are diverse. One of the common ingredients of these models is the assumption that binding sites are vacant or occupied by one adsorbed particle. Double occupation is, however, also possible although energetically not favourable. With this background, the author presents general equations describing coadsorption isotherms and kinetics of molecular adsorption, desorption, and Langmuir–Hinshelwood reaction in the situations when double occupation of binding sites is allowed for one of the adsorbates. The results of the corresponding calculations indicate that the conventional kinetic pathways including vacant sites or sites occupied by one adsorbed particle dominate up to high coverage, roughly at θ ≤ 0.9. With increasing pressure, one can, however, reach the high-coverage limit, θ ≥ 0.9, where the kinetic pathways including double occupation of sites can be dominating. This finding identifies and clarifies one of the likely reasons or complicating factors of the pressure-gap problem in heterogeneous catalysis.

Through the responsible manipulation of linkage chemistry on a molecular scale, the band gaps and electronic structures of two-dimensional covalent organic frameworks (2D COFs) can be finely tuned. Intrinsically, the incorporation of expanded conjugated moieties together with an enhancement of the donor–acceptor (D–A) effect through strategic structural engineering typically determines more favorable photochemical activities for polymers. However, understanding the functional underpinnings of these enhancements remains a significant challenge. In this work, we designed and synthesized a new anthracene-based COF (AND–TAPT) enhanced in its π-conjugation and D–A structure to boost photocatalytic performance. For comparison, an analogous phenyl COF (PDA–TAPT) was also manufactured. As expected, the introduction of anthracene moiety into 2D COFs significantly extended the visible light absorption range beyond 100 nm compared to PDA–TAPT and resulted in more efficient transfer and separation of photogenerated electron–hole pairs. Consequently, as a potent white light-activated catalyst, AND–TAPT achieved superior amine oxidative coupling, selective sulfide oxidation conversion, and selectivity (up to 99%), exemplifying the potential use of such anthracene-derived COFs in this field. This study provides an effective strategy for designing photocatalytic systems.

Silica-supported Rh (Rh/SiO₂) was an effective and reusable heterogeneous catalyst for the hydrogenolysis of isosorbide, providing diols and triols in 58% total yield. The yield was higher than those obtained by hydrogenolysis of glucose and sorbitol, confirming the high potential of isosorbide as a biomass-derived intermediate for the synthesis of polyols.

Vinyl chloride is a crucial raw material for producing polyvinyl chloride. Improper emissions of vinyl chloride during production can cause significant harm to ecosystems and human health. In this work, we prepared Cu-modified Ru/HZSM-5 catalysts by the impregnation method, and investigated the effect of Cu addition on the catalytic combustion of vinyl chloride. The catalytic activity of the Ru/HZSM-5 catalyst was significantly promoted by Cu modification. The T₉₀ of the Ru–2Cu/HZSM-5 catalyst was reduced by 68 °C compared to that of the Ru/HZSM-5 catalyst. The promotion effect of Cu modification was also reflected in the catalytic combustion performance of 1,2-dichloroethane. However, the introduction of Cu had a negative effect on the by-product selectivity. Further modifying the Ru–2Cu/HZSM-5 catalyst with Nb effectively improved selectivity to by-products. The Ru–2Cu/HZSM-5 catalyst also exhibited better cycling stability and water resistance stability than the Ru/HZSM-5 catalyst. Catalyst characterization results showed that the addition of Cu promoted Ru dispersion. Furthermore, the modification with Cu significantly enhanced the redox ability and oxygen mobility of the catalysts, resulting in improved catalytic activity. Additionally, in situ DRIFTS experiments were employed to propose the reaction mechanism for vinyl chloride oxidation over the Ru–2Cu/HZSM-5 catalyst.

As an important application of microfluidic chips, liquid chemical microthrusters need to introduce a structured catalyst block in the design process. In this paper, a structured silver catalyst is used to promote the decomposition of hydrogen peroxide in microfluidic chips. In addition, the temperature of the microchannel on the microfluidic chip is controlled in real time by the planar electric heating plate, and the temperature of the catalytic decomposition reaction of the hydrogen peroxide reaction liquid is monitored in real time by an infrared thermal imaging camera. The reaction rate of catalytic decomposition of hydrogen peroxide was indirectly detected online by an ultraviolet-visible spectrophotometer. The experimental results show that when the temperature of the microfluidic chip exceeds 70 °C, the thermal decomposition rate of hydrogen peroxide in the microchannel on the preheating region gradually dominates and cannot be ignored. When the quadratic regression orthogonal experiment was used to study the influence of 1/T, ln t and ln c₀ on ln r, it was found that ln c₀ had a significant effect on ln r, and (1/T) × ln t and (ln t)² had a significant effect on ln r. And within the experimental study range, when T = 333.16 K, t = 0.02 ms and c₀ = 3 mol L⁻¹, the maximum value of ln r was obtained, and it was 454.5 ± 8.2 mol L⁻¹ s⁻¹. In the single factor study, it can be seen that the temperature of the hot plate and the initial concentration of hydrogen peroxide are positively correlated with the reaction rate of hydrogen peroxide-catalyzed decomposition. The reaction rate of catalytic decomposition of hydrogen peroxide decreases first and then increases with the increase of flow rate. The study of the thermal effect and catalytic performance of microfluidic chips provides a reference value for the design and application of microfluidic chips in microthrusters.

Cycloaddition of CO₂ and epoxides to synthesize cyclic carbonates via photothermal catalysis represents one of the effective strategies for achieving carbon neutrality. In this study, a facile one-step hydrothermal method was employed to synthesize a bimetallic photothermal catalyst FeCo@BPDC. This catalyst demonstrates remarkable efficiency in fixing CO₂ to synthesize cyclic carbonates under atmospheric pressure and solvent-free conditions. Through comprehensive characterization and experimentation, the indispensability of bimetallic active sites has been convincingly demonstrated. Additionally, the incorporation of organic ligands significantly enhances the concentration of oxygen vacancies within the catalyst, thereby endowing it with excellent photocatalytic performance. This study presents a novel perspective for the design of photothermal catalysts that convert CO₂ into value-added chemicals under mild conditions.

The electrocatalytic nitrite (NO₂⁻) reduction reaction (NO₂⁻RR) is an eco-friendly and sustainable method to remove NO₂⁻ pollution under ambient conditions while producing high value-added ammonia (NH₃). However, the conversion of NO₂⁻ to NH₃ is governed by a complex six-electron transfer mechanism, necessitating the development of catalysts that exhibit high efficiency and selectivity. Herein, we report Co nanoparticle-decorated radix cynanchi paniculati-derived carbon (Co@RCPC) as a highly active electrocatalyst for NO₂⁻ to NH₃ conversion. Co@RCPC attains an excellent faradaic efficiency of 92.77% and an NH₃ yield of 1235.62 μmol h⁻¹ cm⁻² in alkaline solution. In addition, it also demonstrates superior stability in recycling stability tests and consecutive long-term electrolysis tests.