VOCs combustion catalysts based on composites of exfoliated organo-Laponite and multimetallic (Mn, Al, Zr, Ce) hydrotalcites prepared by inverse microemulsion

Fine Crystalline Mg-Al Hydrotalcites as Catalysts for Baeyer-Villiger Oxidation of Cyclohexanone with H2O2

The catalytic activity of Mg-Al hydrotalcite (HT) materials in base-catalyzed reactions is known to be promoted by the low crystallinity of the HT solid. In the present work, two routes enabling the preparation of finely crystalline Mg-Al HT materials were explored: (1) the inverse microemulsion technique, and (2) co-precipitation in the presence of starch. Carbonate, chloride and bromide forms of HT were prepared, examined with X-ray diffraction, scanning electron microscopy/energy dispersive X-ray spectroscopy and infrared spectroscopy, and used as catalysts in the Baeyer–Villiger oxidation of cyclohexanone to ε-caprolactone with a H2O2/acetonitrile system. The bromide forms proved significantly less active than the chlorides and carbonates, as they promoted nonselective consumption of H2O2. The fine crystalline materials were more active than the more crystalline HT references obtained by conventional co-precipitation. Catalysts prepared by inverse microemulsion were less crystalline and more active than the starch-templated ones, but suffered stronger deactivation by the acidic reaction environment. Alkalization of the reaction medium with NaHCO3 stabilized the HT materials and increased the ε-caprolactone yield, which became comparable for both types of fine crystalline catalysts—thus pointing to the synthesis involving a simple and cheap starch templating approach as being a particularly attractive one.

Bio-DEE Synthesis and Dehydrogenation Coupling of Bio-Ethanol to Bio-Butanol over Multicomponent Mixed Metal Oxide Catalysts

Within the Waste2Fuel project, innovative, high-performance, and cost-effective fuel production methods from municipal solid wastes (MSWs) are sought for application as energy carriers or direct drop-in fuels/chemicals in the near-future low-carbon power generation systems and internal combustion engines. Among the studied energy vectors, C1-C2 alcohols and ethers are mainly addressed. This study presents a potential bio-derived ethanol oxidative coupling in the gas phase in multicomponent systems derived from hydrotalcite-containing precursors. The reaction of alcohol coupling to ethers has great importance due to their uses in different fields. The samples have been synthesized by the co-precipitation method via layered double hydroxide (LDH) material synthesis, with a controlled pH, where the M(II)/M(III) ≈ 0.35. The chemical composition and topology of the sample surface play essential roles in catalyst activity and product distribution. The multiple redox couples Ni2+/Ni3+, Cr2+/Cr3+, Mn2+/Mn3+, and the oxygen-vacant sites were considered as the main active sites. The introduction of Cr (Cr3+/Cr4+) and Mn (Mn3+/Mn4+) into the crystal lattice could enhance the number of oxygen vacancies and affect the acid/base properties of derived mixed oxides, which are considered as crucial parameters for process selectivity towards bio-DEE and bio-butanol, preventing long CH chain formation and coke deposition at the same time.

CO2 Hydrogenation to Methane over Ni-Catalysts: The Effect of Support and Vanadia Promoting

Within the Waste2Fuel project, innovative, high-performance, and cost-effective fuel production methods are developed to target the “closed carbon cycle”. The catalysts supported on different metal oxides were characterized by XRD, XPS, Raman, UV-Vis, temperature-programmed techniques; then, they were tested in CO2 hydrogenation at 1 bar. Moreover, the V2O5 promotion was studied for Ni/Al2O3 catalyst. The precisely designed hydrotalcite-derived catalyst and vanadia-promoted Ni-catalysts deliver exceptional conversions for the studied processes, presenting high durability and selectivity, outperforming the best-known catalysts. The equilibrium conversion was reached at temperatures around 623 K, with the primary product of reaction CH4 (>97% CH4 yield). Although the Ni loading in hydrotalcite-derived NiWP is lower by more than 40%, compared to reference NiR catalyst and available commercial samples, the activity increases for this sample, reaching almost equilibrium values (GHSV = 1.2 × 104 h–1, 1 atm, and 293 K).

Co/Fe and Co/Al layered double oxides ozone catalyst for the deep degradation of aniline: Preparation, characterization and kinetic model

In this work, Co/Fe and Co/Al layered double oxides (Co/Fe-LDO and Co/Al- LDO)ozone catalysts were obtained from Co/Fe and Co/Al layered double hydroxides intermediates (Co/Fe-LDH and Co/Al-LDH). Firstly, the optimal preparation parameters of the two intermediates were determined, then the morphology and mineralogy microstructure of the derived Co/Fe-LDO and Co/Al- LDO ozone catalysts were systematically studied. Finally, the reaction kinetics of the two ozone catalysts for the deep degradation of aniline wastewater in catalysts/ozone systems were established. The results showed that the optimal preparation conditions were set as pH 12, temperature 60 °C, cobalt‑iron ratio 3:1 for Co/Fe-LDH intermediate, and pH 12, temperature 70 °C, cobalt‑aluminum ratio 3:1 for Co/Al-LDH intermediate. During calcination treatment, the dehydration and recrystallization effect impelled LDH intermediate to form LDO catalyst. The derived ozone catalysts Co/Fe-LDO and Co/Al-LDO possess layered structure, and Co species was mainly based on Co₃O₄ as the main mineral phase of the two ozone catalysts. The addition of catalyst can realize the deep ozonation catalysis of aniline wastewater. The kinetic models established on the aniline oxidized by ozone or catalyst/ozone systems were both fitted the first-order reactions, and the reaction activation energy for COD_Cr and TOC degradation were significantly reduced in catalyst/ozone system.

Enhanced catalytic performance for volatile organic compound oxidation over in-situ growth of MnOx on Co3O4 nanowire

Hierarchical Co₃O₄@MnOx material has been synthesized by in-suit growth of MnOx on the Co₃O₄ and applied in catalytic oxidation of volatile organic compounds (VOCs). Results revealed that T₉₀ of acetone on the Co₃O₄@MnOx was 195 °C, which was 36 °C and 32 °C lower than that on the Co₃O₄ and MnOx/Co₃O₄, respectively. The universality experiments demonstrated that T₉₀ of ethyl acetate and toluene on the Co₃O₄@MnOx were 200 °C and 222 °C, respectively. The above results indicated that Co₃O₄@MnOx catalyst presented a robust catalytic performance. Characterization results showed that high catalytic activity of the Co₃O₄@MnOx catalyst could be attributed to the improvement of low temperature reducibility, the enhancement of Co³⁺ and adsorbed oxygen species resulted from the sufficient reaction between MnO₄^- and Co²⁺ during secondary hydrothermal process. Furthermore, stability and water-resistance experiments showed the Co₃O₄@MnOx catalyst with high cycle and long-term stability, satisfied endurability to 5.5-10 vol. % water vapor at 210 °C.

Excellent porous environmental nanocatalyst: tactically integrating size-confined highly active MnOx in nanospaces of mesopores enables the promotive catalytic degradation efficiency of organic contaminants

A nanoporous molecular sieve catalyst containing size-confined MnO_x species, which affords excellent environmental catalytic efficiency, was synthesized using a micelle-assisted in situ embedding strategy.

Composites of Laponite and Cu⁻Mn Hopcalite-Related Mixed Oxides Prepared from Inverse Microemulsions as Catalysts for Total Oxidation of Toluene

Composites of Laponite and Cu–Mn hopcalite-related mixed oxides, prepared from hydrotalcite-like (Htlc) precursors obtained in inverse microemulsions, were synthesized and characterized with XRF, XRD, SEM, TEM, H₂ temperature-programmed reduction (TPR), and N₂ adsorption/desorption at −196 °C. The Htlc precursors were precipitated either with NaOH or tetrabutylammonium hydroxide (TBAOH). Al was used as an element facilitating Htlc structure formation, and Ce and/or Zr were added as promoters. The composites calcined at 600 °C are mesoporous structures with similar textural characteristics. The copper–manganite spinel phases formed from the TBAOH-precipitated precursors are less crystalline and more susceptible to reduction than the counterparts obtained from the precursors synthesized with NaOH. The Cu–Mn-based composites are active in the combustion of toluene, and their performance improves further upon the addition of promoters in the following order: Ce < Zr < Zr + Ce. The composites whose active phases are prepared with TBAOH are more active than their counterparts obtained with the use of the precursors precipitated with NaOH, due to the better reducibility of the less crystalline mixed oxide active phase.