Al Hydrotalcite Research Articles

Streaming-Induced Hydrovoltaic Power Generation by Fluorinated Mg–Al Hydrotalcite Nanoclay

Streaming-Induced Hydrovoltaic Power Generation by Fluorinated Mg–Al Hydrotalcite Nanoclay

Effect of the hydrotalcite formation on the fracture behavior and corrosion resistance of HA‐bonded alumina‐spinel castables

AbstractHydratable alumina‐bonded castable is a promising non‐cement bonded refractory for ladle lining. An in situ formation of layered double hydroxides (Mg–Al hydrotalcite, M–A–H) using reactive MgO powders is proposed as a means of enhancing the castables during curing, drying, and after the high‐temperature treatment. The formation of hydrotalcite, spinel transformation, pore structure, mechanical properties, fracture behavior, and slag corrosion resistance have been systematically investigated. The results indicate that the hydrotalcite formation is governed by the hydration reactivity of MgO, which promotes the formation of Mg(OH)2 as an intermediate hydrate, and the ultimate growth of hydrotalcite. The residual MgO and newly formed hydrotalcite are eventually transformed into micron size and submicron size spinel, respectively. This structural evolution contributes to an optimized pore structure and microstructure, enhancing the castables. The ultimate pore structure and enhanced interfaces between aggregate and matrix facilitate the improvement of toughness and slag corrosion/penetration resistance.

High-Throughput, In Situ Preparation of Mg–Al Hydrotalcites and Tandem Self-Condensation of Cyclopentanone Integrated via the Ball-Milling Process

High-Throughput, In Situ Preparation of Mg–Al Hydrotalcites and Tandem Self-Condensation of Cyclopentanone Integrated via the Ball-Milling Process

Zn–Al Hydrotalcites and Magnetic Zn–Al Hydrotalcites for Efficient Phosphate Remediation and Recovery

Zn–Al Hydrotalcites and Magnetic Zn–Al Hydrotalcites for Efficient Phosphate Remediation and Recovery

Solvent-free oxidative coupling of benzylamine to imine using reusable MnO4−1 incorporated Mg–Al hydrotalcite catalyst

Solvent-free oxidative coupling of benzylamine to imine using reusable MnO4−1 incorporated Mg–Al hydrotalcite catalyst

Super rapid preparation of biodiesel over highly dispersed K2CO3 supported by LDH

AbstractA new heterogeneous K2CO3 supported by a layered double hydroxide (LDH), Mg–Al hydrotalcite, was prepared and used as a catalyst for the biodiesel preparation by a tri‐component coupling transesterification of methanol, vegetable oil, and methyl acetate. K2CO3/Mg‐Al exhibits high catalytic activities, and biodiesel yield can reach 99.48% within 20 min under 60°C, with 6 wt.% of K2CO3/Mg‐Al, 1:1:12 molar ratio of rapeseed oil, methyl acetate, and methanol. Fourier‐transform infrared spectroscopy, X‐ray diffraction (XRD), scanning electron microscopy, nitrogen physical adsorption, thermogravimetry analysis, and CO2‐chemical adsorption were used to assess the physical properties of the prepared K2CO3/Mg‐Al. Using the tri‐component coupling transesterification, 12.2% cost reduce can be get by reducing the cost from 8458 to 7424 ¥/t compared with di‐component transesterification containing oil and methanol as resource.

Controlling hydration of hydratable alumina via co‐grinding with Mg–Al hydrotalcite

AbstractThe on‐site industrial application of hydratable alumina (HA)‐bonded castables is inhibited by the high hydration rate of HA. In this study, the hydration behavior of HA co‐ground with sheetlike Mg–Al hydrotalcite (MAT) is investigated. The properties of castables bonded with MAT‐bearing HA are systematically assessed. The hydration rate of HA co‐ground MAT decreases as this allows MAT sheets to be effectively inserted into the microcracks of HA particles during grinding, thus decreasing the direct contact area between HA and water. The strength of MAT‐bearing castables (0.5 and 1 wt%) fired at 800°C improved slightly owning to the generation of magnesia–alumina spinel. The mechanical strength of castables fired at 1100 and 1550°C decreased as the MAT content increased owing to an increase in porosity. Based on an analysis of the hydration behavior of HA and the properties of HA‐bonded castables, the optimal MAT/HA weight ratio is approximately 1/10.

Hybrid Nanocomposite Comprising Mg–Al Hydrotalcite Nanocrystals on ZSM-5 Zeolite for Production of Renewable Fuel Additives from Furfural

An acido-basic nanocomposite is prepared through the in situ formation and growth of Mg–Al hydrotalcite nanocrystals on a ZSM-5 surface. The metal-functionalized hydrotalcite-ZSM-5 composite has been employed as a catalyst for the single-pot conversion of furfural to ethyl levulinate. The specific morphology of the composite with edge-to-face attachment of hydrotalcite nanocrystals on the ZSM-5 surface confirms the accessibility to the active sites located inside the zeolite pores. The prepared samples are thoroughly characterized using techniques like HR-SEM, HR-TEM, XRD, FTIR, N2 adsorption–desorption, TPD, TPR, UV–Vis spectroscopy, XPS, etc. for a better understanding of the catalyst properties. As high as 76% yield of ethyl levulinate was obtained through the cascaded transfer hydrogenation–alcoholysis reaction using ethanol as a H2 donor. In metal-functionalized hydrotalcite-ZSM-5 composite, metallic sites, basic sites, and acid sites are in close proximity, which act synergistically to exhibit superior catalytic performance.

Plasma-Catalytic CO2 Reforming of Toluene over Hydrotalcite-Derived NiFe/(Mg, Al)O x Catalysts.

The removal of tar and CO2 in syngas from biomass gasification is crucial for the upgrading and utilization of syngas. CO2 reforming of tar (CRT) is a potential solution which simultaneously converts the undesirable tar and CO2 to syngas. In this study, a hybrid dielectric barrier discharge (DBD) plasma-catalytic system was developed for the CO2 reforming of toluene, a model tar compound, at a low temperature (∼200 °C) and ambient pressure. Periclase-phase (Mg, Al)O x nanosheet-supported NiFe alloy catalysts with various Ni/Fe ratios were synthesized from ultrathin Ni-Fe-Mg-Al hydrotalcite precursors and employed in the plasma-catalytic CRT reaction. The result demonstrated that the plasma-catalytic system is promising in promoting the low-temperature CRT reaction by generating synergy between DBD plasma and the catalyst. Among the various catalysts, Ni4Fe1-R exhibited superior activity and stability because of its highest specific surface area, which not only provided sufficient active sites for the adsorption of reactants and intermediates but also enhanced the electric field in the plasma. Furthermore, the stronger lattice distortion of Ni4Fe1-R provided more isolated O2- for CO2 adsorption, and having the most intensive interaction between Ni and Fe in Ni4Fe1-R restrained the catalyst deactivation induced by the segregation of Fe from the alloy to form FeO x . Finally, in situ Fourier transform infrared spectroscopy combined with comprehensive catalyst characterization was used to elucidate the reaction mechanism of the plasma-catalytic CRT reaction and gain new insights into the plasma-catalyst interfacial effect.

Chemical transesterification of soybean oil as a feedstock for stable biodiesel and biolubricant production by using Zn Al hydrotalcites as a catalyst and perform tribological assessment

Chemical transesterification of soybean oil as a feedstock for stable biodiesel and biolubricant production by using Zn Al hydrotalcites as a catalyst and perform tribological assessment

Production of biodiesel: kinetics and reusability studies of the Mg–Al hydrotalcite catalyst using Jatropha oil

The optimal conditions for biodiesel transesterification are 800 rpm stirring, 12 : 1 methanol to oil ratio, 3% catalyst loading, and 60 °C temperature.

Study of the formation and anti-corrosion properties of Zn[sbnd]Al hydrotalcite conversion films grown “in situ” on different zinc alloys coated steel

The Zn-Al-CO32− hydrotalcite (HT) conversion film was developed on hot-dip galvanized steel (HDG), ZnAl coated steel (ZA), and Zn-Al-Mg coated steel (ZAM) substrates by “in situ” growth process for Al3+/Zn2+ ratio of 5/3 at pH 12. The characteristics of all the ZnAl HT film-coated samples before and after exposure to 0.1 M NaCl for 24 h were investigated by means of Fourier-transform infrared (FT-IR), X-Ray Diffraction (XRD), electron microscopy/energy dispersive X-ray spectroscopy SEM/EDS, and X-ray photoelectron spectroscopy (XPS). The corrosion properties of all the samples were studied by open circuit potential measurements (OCP), polarization curves, and electrochemical impedance spectroscopy (EIS). The electrochemical tests indicated that the HT film-coated can significantly restrain the corrosion of the HDG, ZA, and ZAM substrates but this efficiency was depending on the alloying compounds of the sacrificial layer. The inhibitive effect of HT film-coated on all the corrosion substrates was discussed in detail.

Reconstruction and hydration of hydrotalcite response to thermal activation temperature: Enhancement of properties for magnesia castables

Optimization binding system for refractory castables is significant to enhance the service performance. Hydrotalcite has been considered a promoter for high-temperature performance of basic castables, however, its binding property remains to be improved before practical application. In this work, the thermal activated Mg–Al hydrotalcites were incorporated in magnesia castables, and the mutual influence of pre-calcination temperature on the hydration, microstructure, and strength of castables was investigated. The obtained results indicated that the reconstruction of calcined hydrotalcite took place in the hydration process and effectively motivated the hydrolysis. Hydrate was thus promoted and a relatively dense microstructure of magnesia castables was confirmed by X-ray computed tomography analysis. Hydrotalcite pre-calcinated at 300 °C contributed to the highest early strength for castable, and the high-temperature properties also performed better than that of other pre-calcinated hydrotalcite-adding. The enhancement mechanisms of calcined hydrotalcite were attributed to the two following reasons: (ⅰ) the modified microstructure of magnesia castables from the early stage by hydration process, (ⅱ) the further enhanced sinterability inspired by the appropriate thermal activation effect.

Synthesis of Biohybrid Material Based on Magnetic Zn–Al Hydrotalcite and Cellulase: Structural and Enzymatic Activity Characterizations

Synthesis of Biohybrid Material Based on Magnetic Zn–Al Hydrotalcite and Cellulase: Structural and Enzymatic Activity Characterizations

Novel In2S3/Zn–Al LDHs composite as an efficient visible-light-driven photocatalyst for tetracycline degradation

Hexagonal Zn–Al hydrotalcite (Zn–Al LDHs) has become a research hotspot in the field of photocatalysis due to efficient photocatalytic performance, low cost and non-toxicity. In this research, In2S3/Zn–Al LDHs composites were firstly synthesized by one-pot method with InCl3 and TAA as raw materials. The crystalline structure, surface morphology, chemical composition, together with optical properties of the samples were investigated by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectra (FT-IR), UV–Vis diffuse reflectance spectrometry (DRS), and Photoluminescence spectra (PL). The photocatalytic performance of the composite photocatalyst was investigated by degradation of tetracycline (TC) under visible-light irradiation. The photochemical properties and cyclic stability of the photocatalyst were further explored. Experimental results display that the photocatalytic efficiency of In2S3/Zn–Al LDHs (1:2) was remarkably superior to that of pure In2S3 and Zn–Al LDHs. In2S3/Zn–Al LDHs (1:2) composite showed high photocatalytic activity for TC degradation (92.2% within 30 min). The modification of Zn–Al LDHs by In2S3 prompted the separation of photogenerated electron-hole pairs and thus improved the photocatalytic performance. It can be inferred that the efficient photocatalytic performance of In2S3/Zn–Al LDHs composites could remove many hazardous pollutants in wastewater.

Enhanced Methanol Production over Non-promoted Cu–MgO–Al2O3 Materials with Ex-solved 2 nm Cu Particles: Insights from an Operando Spectroscopic Study

Enhanced methanol production is obtained over a non-promoted Cu–MgO–Al2O3 mixed oxide catalyst derived from a Cu–Mg–Al hydrotalcite precursor (HT) containing narrowly distributed small Cu NPs (2 nm). Conversions close to the equilibrium (∼20%) with a methanol selectivity of 67% are achieved at 230 °C, 20 bar, and a space velocity of 571 mL·gcat–1·h–1. Based on operando spectroscopic studies, the striking activity of this Cu-based catalyst is ascribed to the stabilization of Cu+ ions favored under reaction conditions due to lattice reorganization associated with the “HT-memory effect” promoted by water. Temperature-resolved infrared–mass spectrometry experiments have enabled the discernment of monodentate formate species, stabilized on Cu+ as the intermediate in methanol synthesis, in line with the results of density functional theory calculations. These monodentate formate species are much more reactive than bridge formate species, the latter ones behaving as intermediates in methane and CO formation. Moreover, poisoning of the Cu0 surface by strongly adsorbed species behaving as spectators is observed under reaction conditions. This work presents a detailed spectroscopic study highlighting the influence of the reaction pressure on the stabilization of active surface sites, and the possibility of enhancing methanol production on usually less active non-promoted nano-sized copper catalysts, provided that the proper support is selected, allowing the stabilization of doped Cu+. Thus, a methanol formation rate of 2.6 × 10–3 molMeOH·gcat–1·h–1 at 230 °C, 20 bar, and WHSV = 28 500 mL·gcat–1·h–1 is obtained on the Cu–MgO–Al2O3 HT-derived catalyst with 71% methanol selectivity, compared to 2.2 × 10–4 molMeOH·gcat–1·h–1 with 54% methanol selectivity obtained on a reference Cu/(Al2O3/MgO) catalyst not derived from a HT structure.

Hydrotalcite-derived aluminum-doped cobalt oxides for catalytic benzene combustion: Effect of calcination atmosphere

Al-doped Co3O4 and CoO are prepared from Co‒Al hydrotalcite by calcination in air and N2 atmospheres, and characterized by TG-DTA, XRD, SEM, N2 adsorption, Raman, XPS, and H2-TPR. Co‒Al hydrotalcite is oxidized to Co(Co,Al)2O4 in air accompanying with the collapse of layered structure, while in N2 it decomposes to Co(Al)O that remains the plate morphology of hydrotalcite. In both cases, Al3+ is doped into the lattice of cobalt oxides, leading to marked changes in the crystal size, surface state, and reducibility. Especially, Al-doped CoO shows smaller crystal size (4.1 nm), larger surface area (172 m2 g‒1), and higher degree of structural disorder than Al-doped Co3O4. Meanwhile, the Al-doped cobalt oxides show different reducibilities to those of Co3O4 and CoO, indicating a strong interaction between cobalt and aluminum. The N2-calcined sample exhibits higher activity for benzene combustion than the air-calcined sample as well as a relatively good stability during heating/cooling cycles and a good long-time durability. Under the reaction atmosphere, Co(Al)O is transferred to Co(Co,Al)2O4. The resulting Co(Co,Al)2O4 remains the original plate morphology and textural property and presents abundant surface adsorbed oxygen species, which accounts for its high activity.

The in situ growth of Mg–Al hydrotalcite on spherical alumina and its application as a support of a Pt-based catalyst for isobutane dehydrogenation

The in situ growth of Mg–Al hydrotalcite on spherical alumina and its application in catalytic dehydrogenation with a Pt-based catalyst.

Photocatalytic Degradation of Composites with Magnesium Aluminum Hydrotalcite Derived Metal Oxides and g-C3N4

The remove of the organic pollutants in water plays an important role on the environmental protection, thus photocatalysis, as an effective method, has been attained much attention to deal with this problem. In this paper, a composite of g-C3N4 and Mg–Al hydrotalcite derived metal oxides was prepared by simple co-precipitation methods followed by calcination. The effective adsorption-photocatalysis synergic effect and highly efficient removal of organic pollutants from water under simulated sunlight irradiation was found in the presence of fabricated metal oxide nanocomposites. The photocatalytic degradation rate of methylene blue reached 97.3% within 1 h under visible light, and the degradation rate constant was 0.0432 min−1, which is 3.6 times that of g-C3N4. Though characterization analysis, more active sites are exposed to absorb more organic pollutants on the mater surface in the presence of the open hierarchical structures of composite materials, and the "face to face" contact structure between 2D materials is formed to promote the separation of electrons and holes. The photocatalytic degradation was stable in the recycling process of the catalyst. In addition, the photocatalytic degradation mechanism of the catalyst was explained by free radical scavenging experiment. The material provides an effective method for removing organic pollutants in water, and has broad application prospects.

Preparation and characteristics of modified red mud-municipal solid waste incineration bottom ash binder

In this paper, red mud (RM) and municipal solid waste incineration bottom ash (MSWIBA) were thermal modified to improve the pozzolanic activity. A binder was prepared with modified RM and MSWIBA by activation of calcium hydroxide (CH). The hydration and mechanical behavior of the prepared binder was systematically studied. The results indicated that the calcium-rich RM (CRM) had a higher pozzolanic activity after modification than the iron-rich RM. The hydrates formed in the modified RM-MSWIBA-CH system at ambient temperature were essentially Ca–Al hydrotalcite and C-A-S-H gel. The hydration reaction in the pastes mainly concentrated in the early stages, whereas the high amount of CH was not conducive to this process. Moreover, the RM-MSWIBA-CH system could be easily carbonized in the atmosphere. The maximum compressive strength of paste was 5.18 MPa with a fluidity of 85.5 mm when the proportion of CRM to MSWIBA was 3:2 (with 20% CH), and the sample with proportion of CRM to MSWIBA was 2:3 (with 10% CH) had the highest fluidity (97.5 mm) with a compressive strength of 2.42 MPa. The developed binder with low CRM content holds great potential for applications as a controlled low-strength material (CLSM). The overall findings from this study provide new insights in low carbon and green recycling of RM and MSWIBA with wide application potential in construction industry.