On the Role of Protonic Acid Sites in Cu Loaded FAU31 Zeolite as a Catalyst for the Catalytic Transformation of Furfural to Furan.

The aim of the present paper is to study the speciation and the role of different active site types (copper species and Brønsted acid sites) in the direct synthesis of furan from furfural catalyzed by copper-exchanged FAU31 zeolite. Four series of samples were prepared by using different conditions of post-synthesis treatment, which exhibit none, one or two types of active sites. The catalysts were characterized by XRD, low-temperature sorption of nitrogen, SEM, H2-TPR, NMR and by means of IR spectroscopy with ammonia and CO sorption as probe molecules to assess the types of active sites. All catalyst underwent catalytic tests. The performed experiments allowed to propose the relation between the kind of active centers (Cu or Brønsted acid sites) and the type of detected products (2-metylfuran and furan) obtained in the studied reaction. It was found that the production of 2-methylfuran (in trace amounts) is determined by the presence of the redox-type centers, while the protonic acid sites are mainly responsible for the furan production and catalytic activity in the whole temperature range. All studied catalysts revealed very high susceptibility to coking due to polymerization of furfural.

Sonically modified hierarchical FAU-type zeolites as active catalysts for the production of furan from furfural.

In this study, the sonochemical-assisted desilication method was applied as a special and innovative way of preparing hierarchical zeolites. The physicochemical properties of the hierarchical zeolites prepared using the sonochemical route were compared with those prepared using the conventional desilication method. Commercial zeolite with FAU-type structure was desilicated with a sodium and tetrabutylammonium hydroxide aqueous solution (NaOH/TBAOH) for 30 min. The ultrasound treatment process was performed using a QSonica Q700 sonicator (Church Hill Rd, Newtown, CT, USA) equipped with a ½â€³ diameter horn. The average power of sonication was 60 W, and the frequency was 20 kHz. During the sonication procedure, the alkaline solution with the catalyst precursor and sonicator probe were placed in an ice bath to keep them at room temperature. The prepared catalyst samples were examined by ICP-OES, XRD, SEM, NMR, and nitrogen sorption techniques. The acidic properties of the prepared hierarchical zeolite samples were assessed by means of IR spectroscopy with ammonia and carbon monoxide sorption as probe molecules. All catalysts were studied in the decarbonylation of furfural into furan. Independently of the application of ultrasonic irradiation, desilication of zeolites with an NaOH/TBAOH mixture extracts comparable amounts of silicon, resulting in comparable crystallinity and acidity. On the other hand, the samples prepared in the presence of ultrasounds revealed higher both mesoporosity and enhanced catalytic properties in the reaction of decarbonylation of furfural into furan in comparison with their counterparts prepared using the conventional method.

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.

Novel Montmorillonite/TiO2/MnAl-Mixed Oxide Composites Prepared from Inverse Microemulsions as Combustion Catalysts.

A novel design of combustion catalysts is proposed, in which clay/TiO2/MnAl-mixed oxide composites are formed by intermixing exfoliated organo-montmorillonite with oxide precursors (hydrotalcite-like in the case of Mn-Al oxide) obtained by an inverse microemulsion method. In order to assess the catalysts' thermal stability, two calcination temperatures were employed: 450 and 600 °C. The composites were characterized with XRF (X-ray fluorescence), XRD (X-ray diffraction), HR SEM (high resolution scanning electron microscopy, N2 adsorption/desorption at -196 °C, and H2 TPR (temperature programmed reduction). Profound differences in structural, textural and redox properties of the materials were observed, depending on the presence of the TiO2 component, the type of neutralization agent used in the titania nanoparticles preparation (NaOH or NH3 (aq)), and the temperature of calcination. Catalytic tests of toluene combustion revealed that the clay/TiO2/MnAl-mixed oxide composites prepared with the use of ammonia showed excellent activity, the composites obtained from MnAl hydrotalcite nanoparticles trapped between the organoclay layers were less active, but displayed spectacular thermal stability, while the clay/TiO2/MnAl-mixed oxide materials obtained with the aid of NaOH were least active. The observed patterns of catalytic activity bear a direct relation to the materials' composition and their structural, textural, and redox properties.