Medium Basic Sites Research Articles

Synergistic Catalysis by MgO Induced Acid‐Base Bifunctional Sites for Cross Condensation of HCHO and Acetaldehyde

AbstractAcid‐base synergistic catalysis greatly enhances the performance of MgO‐based catalysts in the Aldol condensation. In this paper, the effect of acid‐base strength/concentration/proportion and the synergistic catalysis on the performance of cross condensation between HCHO and acetaldehyde were studied. The NH3/CO2‐TPD results indicated that the weak acidic sites combined with the medium basic sites were beneficial for the cross condensation of formaldehyde and acetaldehyde. The loading of MgO nanocrystals on SiO2 induced the generation of new acidic sites (Mg‐O‐Si). Combined with the inherent basic sites (Mg‐O‐Mg) and Mg‐O‐Si, the acid‐base bifunctions sites could catalyze the cross condensation of HCHO and acetaldehyde synergistically. The appropriate proportion of acidic/basic sites (10/1) was critical for the cross condensation in the presence of vast water in formalin. The effect of reaction parameters, including molar ratio of substrates, reaction temperature, linear velocity and weight hourly space velocity, were investigated for the cross condensation. The results showed that 10 wt% MgO/SiO2 catalysts exhibited the highest catalytic activity (57.9% conversion of acetaldehyde and 84.3% selectivity of acrolein) under the optimal reaction parameters among the investigated catalysts. The catalytic performance of MgO/SiO2 could be recovered after in situ regeneration in air to remove the carbon deposition.

Enhanced carbon dioxide adsorption performance of UiO-66-SO3H with a mixed ligand strategy

Enhanced carbon dioxide adsorption performance of UiO-66-SO3H with a mixed ligand strategy

Preparation of heavy bio-oil-based porous carbon by pyrolysis gas activation and its performance in the aldol condensation for aviation fuel as catalyst carrier

Preparation of heavy bio-oil-based porous carbon by pyrolysis gas activation and its performance in the aldol condensation for aviation fuel as catalyst carrier

Enhanced CO2 methanation over LaNiO3/CeO2 derivative catalyst with high activity and stability

Enhanced CO2 methanation over LaNiO3/CeO2 derivative catalyst with high activity and stability

Performance of NiO doped on alkaline sludge from waste photovoltaic industries for catalytic dry reforming of methane.

Alkali sludge (AS) is waste abundantly generated from solar photovoltaic (PV) solar cell industries. Since this potential basic material is still underutilized, a combination with NiO catalyst might greatly influence coke resentence, especially in high-temperature thermochemical reactions (Arora and Prasad, RSC Adv. 6:108,668-108688, 2016). This paper investigated alkaline sludge containing 3CaO-2SiO2 doped with well-known NiO to enhance the dry reforming of methane (DRM) reaction. The wet-impregnation method was used to prepare the xNiO/AS (x = 5-15%) catalysts. Subsequently, all catalysts were tested by using X-ray diffraction (XRD), nitrogen adsorption/desorption (BET), temperature-programmed reduction of hydrogen (H2-TPR), temperature-programmed desorption of carbon dioxide (TPD-CO2), field emission scanning electron microscopy (FESEM-EDX), and X-ray photoelectron spectroscopy (XPS). The spent catalysts were analyzed by thermogravimetric analysis (TGA/DTG), transmission electron microscopy (TEM), and temperature-programmed oxidation (TPO). The catalytic performance of xNiO/AS catalysts was investigated in a fixed bed reactor connected with gas chromatography thermal conductivity detector (GC-TCD) at a CH4:CO2 flow rate of 30 mL-1 during a 10-h reaction by following (Shamsuddin et al., Int. J. Energy Res. 45:15,463-15,480, 2021d). For optimization parameters, the effects of NiO concentration (5, 10, and 15%), reaction temperature (700, 750, 800, 850, and 900 °C), catalyst loading (0.1, 0.2, 0.3, 0.4, and 0.5 g), and gas hourly space velocity (GHSV) range from 3000, 6000, 9000, 12,000, and 15,000 h-1 were evaluated. The results showed that physical characteristics such as BET surface area and porosity do not significantly impact NiO percentages of dispersion, whereas chemical characteristics like reducibility are crucial for the catalysts' efficient catalytic activity. Due to the active sites on the catalyst surface being more accessible, increased NiO dispersion resulted in higher reactant conversion. The catalytic performance on various parameters that showed 15%NiO/AS exhibited high reactant conversion up to 98% and 40-60% product selectivity in 700 °C, 0.2 g catalyst loading, and 12,000 h-1 GHSV. According to spent catalyst analyses, the catalyst was stable even after the DRM reaction. Meanwhile, increased reducibility resulted in more and better active site formation on the catalyst. Synergetic effect of efficient NiO as active metal and medium basic sites from AS enhanced DRM catalytic activity and stability with low coke formation.

Oxygen vacancy engineering in MOF-derived AuCu/ZnO bimetallic catalysts for methanol synthesis via CO2 hydrogenation

Oxygen vacancy engineering in MOF-derived AuCu/ZnO bimetallic catalysts for methanol synthesis via CO2 hydrogenation

Sustainable methyl formate generation by dehydrogenation of green methanol over Cu_SiO2/MgO

Sustainable methyl formate generation by dehydrogenation of green methanol over Cu_SiO2/MgO

Ce enhanced RuNi alloy multi-metal synergic hydrotalcite oxide derived catalyst for high performance CO2 methanation

Ce enhanced RuNi alloy multi-metal synergic hydrotalcite oxide derived catalyst for high performance CO2 methanation

Synergistic effects between Mn and Co species in CO2 hydrogenation over xCo/MnO catalysts

Synergistic effects between Mn and Co species in CO2 hydrogenation over xCo/MnO catalysts

High-performance Al-doped Cu/ZnO catalysts for CO2 hydrogenation to methanol: MIL-53(Al) source-enabled oxygen vacancy engineering and related promoting mechanisms

High-performance Al-doped Cu/ZnO catalysts for CO2 hydrogenation to methanol: MIL-53(Al) source-enabled oxygen vacancy engineering and related promoting mechanisms

Mesoporous-Layered Double Oxide/MCM-41 Composite with Enhanced Catalytic Performance for Cyclopentanone Aldol Condensation

Layered double oxides are widely employed in catalyzing the aldol condensation for producing biofuels, but its selectivity and stability need to be further improved. Herein, a novel MCM-41-supported Mg–Al-layered double oxide (LDO/MCM-41) was prepared via the in situ integration of a sol–gel process and coprecipitation, followed by calcination. This composite was first employed to catalyze the self-condensation of cyclopentanone for producing high-density cycloalkane precursors. LDO/MCM-41 possessed large specific surface area, uniform pore size distribution, abundant medium basic sites and Bronsted acid sites. Compared with the bulk LDO, LDO/MCM-41 exhibited a higher selectivity for C10 and C15 oxygenates at 150 °C (93.4% vs. 84.6%). The selectivity for C15 was especially enhanced on LDO/MCM-41, which was three times greater than that on LDO. The stability test showed that naked LDO with stronger basic strength had a rapid initial activity, while it suffered an obvious deactivation due to its poor carbon balance. LDO/MCM-41 with lower basic strength had an enhanced stability even with a lower initial activity. Under the optimum conditions (50% LDO loading, 170 °C, 7 h), the cyclopentanone conversion on LDO/MCM-41 reached 77.8%, with a 60% yield of C10 and 15.2% yield of C15.

Synergistic promotions of K doping on CO2 capture and in situ conversion

AbstractThe integrated CO2 capture and conversion (iCCC) technology has been recognized as a promising strategy for upcycling the emitted CO2 into artificial carbon sequestration but still demands highly efficient dual functional materials (DFMs). We develop an efficient iCCC process of the integrated lithium‐looping (LiL) and reverse water gas shift reaction through deeply understanding K doping in the novel Kx‐Li4SiO4@Niy DFMs. The appropriate K doping enables the fast diffusion of CO2 and H2 into the bulk DFMs through forming LiKCO3 surface eutectic layer as well as strongly interacts with catalyst Ni to generate new medium basic sites for synergistic promotions of CO2 capture and in situ conversion. More importantly, after the pelletization, the LP‐K0.2‐Li4SiO4@Ni10 DFM (20–40 mesh) avoids the agglomeration and achieves an excellent and stable iCCC cycle performance, with CO2 capture capacity of 3.8 mmol/g, CO2 conversion efficiency of 90%, and CO selectivity close to 100% at 550°C in one fixed‐bed column.

Effect of Support on Oxidative Esterification of 2,5-Furandiformaldehyde to Dimethyl Furan-2,5-dicarboxylate

One-step oxidative esterification of 2,5-furandiformaldehyde (DFF) derived from biomass to prepare Dimethyl Furan-2,5-dicarboxylate (FDMC) not only simplifies the catalytic process and increases the purity of the product, but also avoids the polymerization of 5-hydroxymethylfurfural (HMF) at high-temperature conditions. Gold supported on a series of acidic oxide, alkaline oxide, and hydrotalcite was prepared using colloidal deposition to explore the effect of support on the catalytic activities. The Au/Mg3Al-HT exhibited the best catalytic activity, with 97.8% selectivity of FDMC at 99.9% conversion of DFF. This catalyst is also suitable for oxidative esterification of benzaldehyde and furfural. X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and CO2 temperature programmed desorption (CO2-TPD) were performed to characterize the catalysts. The results indicated that the medium and strong basic sites in the catalysts benefited for the absorption of intermediate agents and facilitated the oxidative esterification of aldehyde groups, while neutral or acidic supports tended to produce an acetal reaction. It is worth noting that basicity on the support surface reduced the electronic state of the Au nanoparticle (Auδ−) and, thus, enhanced the catalytic selectivity of oxidative esterification. This finding demonstrated that the support plays a crucial role in oxidative esterification.

Cooperative catalysis of carbon supported zinc salts hybrid for efficient conversion of fructose to ethyl lactate

Cooperative catalysis of carbon supported zinc salts hybrid for efficient conversion of fructose to ethyl lactate

Cyano group modified graphitic carbon nitride supported Ru nanoparticles for enhanced CO2 methanation

Cyano group modified graphitic carbon nitride supported Ru nanoparticles for enhanced CO2 methanation

Activity of Nickel Supported Over Nanorod-Shaped Strontium Hydroxyapatite Catalysts in Selective Methanation of CO & CO2

Nickel modified strontium hydroxyapatite (Ni/Sr-HAP) supported catalysts are studied in selective methanation of CO/CO2. In this work, a new type of nano rod-shaped strontium hydroxyapatite-based catalysts with two different sizes and aspect ratios were prepared by sol–gel method and in next step, Ni precursor was wet impregnated i.e., denoted as Ni/Sr-HAP and Ni/Sr-HAP(F127). The catalytic tests were performed in CO and CO2 methanation reactions and evaluated the light-off temperatures curves (225–450 °C) under ambient pressure in a fixed-bed flow reactor. The physicochemical properties of the prepared catalysts were characterized by XRD, N2 physisorption, TEM, SEM, TPR, CO2/H2-TPD and H2-chemisorption techniques. From XRD analysis, both Ni/Sr-HAP and Ni/Sr-HAP(F127) were identified as the hydroxyapatite type structure with high crystallinity and very low intensity peaks corresponds to strontium phosphates as the main phase and structure. The TEM and SEM micrographs of Ni/Sr-HAP catalysts displayed a nano- rod shaped morphology with different dimensions and exhibited average Ni particle size of ~ 9.2 nm. While Ni/Sr-HAP(F127) shown the rod size in the length in the range of 100–250 nm and width in the range of 20–40 nm with average Ni particle size 5.7 nm. The F127 mediated support Sr-HAP synthesis i.e., Ni/Sr-HAP(F127) mesoporous catalyst possessed higher metal surface with smaller Ni particles size and possessed higher CO2 adsorption capacity. The medium strength basic sites of Ni/Sr-HAP catalyst played an important role in methanation reactions. Based on the characterization and the catalysts activity results, small sized nanorods of Ni/Sr-HAP(F127) is the most active and selective catalyst due to the higher Ni dispersion, higher amounts of medium basic sites, and reducibility character than the bigger nanorods based Ni/Sr-HAP catalyst.

Cyclic operation of CO2 capture and conversion into methane on Ni-hydrotalcite based dual function materials (DFMs)

Cyclic operation of CO2 capture and conversion into methane on Ni-hydrotalcite based dual function materials (DFMs)

Promotion effect of different lanthanide doping on Co/Al2O3 catalyst for dry reforming of methane

Promotion effect of different lanthanide doping on Co/Al2O3 catalyst for dry reforming of methane

Facile and efficient synthesis of ordered mesoporous MIL-53(Al)-derived Ni catalysts with improved activity in CO2 methanation

Facile and efficient synthesis of ordered mesoporous MIL-53(Al)-derived Ni catalysts with improved activity in CO2 methanation

Selective Synthesis of Renewable Bio-Jet Fuel Precursors from Furfural and 2-Butanone via Heterogeneously Catalyzed Aldol Condensation

This study aims to synthesize α,β-unsaturated carbonyl compounds with branched structures via aldol condensation of furfural and 2-butanone using magnesium–aluminum (MgAl) mixed oxides as heterogeneous acid–base catalysts. Regarding the molecular structure of 2-butanone, there are two possible enolate ions generated by subtracting the α-hydrogen atoms at the methyl or methylene groups of 2-butanone. The branched-chain C9 products, derived from the methylene enolate ion, can be applied as bio-jet fuel precursors. The most suitable catalyst, contributing the highest furfural conversion (63%) and selectivity of the branched-chain C9 products (77%), is LDO3, the mixed oxides with 3:1 Mg:Al atomic ratio, with a high surface area and a large number of medium basic sites. The suitable reaction conditions to produce the branched-chain C9 ketones are 1:5 furfural:2-butanone molar ratio, 5 wt.% catalyst loading, 120 °C reaction temperature, and 8 h reaction time. Additionally, this study investigates the adsorption of 2-butanone onto a mixed oxide using in situ Fourier transform infrared spectroscopy; the results of which suggest that the methylene enolate of 2-butanone is the likely dominant surface intermediate at elevated temperatures. Accordingly, the calculation, based on density functional theory, indicates that the methylene enolate ion of 2-butanone is the kinetically favorable intermediate on an MgO(100) as a model oxide surface.