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The inefficient reuse and recycling of plastics—and the current surge of medical and take-out food packaging use during the pandemic—have exacerbated the environmental burden. This impels the development of alternative recycling/upcycling methods to pivot toward circularity. We report the use of the Mannich three-component coupling reaction for the modification of polystyrene (PS) recovered with a 99.1% yield from waste food containers to form functionalized nitrogen and oxygen-rich PS derivatives. A series of functionalized PS with increasing moles of formaldehyde (F) and morpholine (M) (0.5 × 10−2, 1.0 × 10−2, and 2.0 × 10−2 mol) was achieved using a sol–gel-derived Fe-TiO2 catalyst in a solvent-free, microwave-assisted synthesis. Modified polymers were characterized with viscometry, 1H NMR, 13CNMR (DEPT) FTIR, XPS, UV, and TGA. Functionalization scaled with an increasing ratio, validating the 3CR approach. Further functionalization was constrained by a competing oxidative degradation; however, the varying hydrogen bond density due to nitrogen and oxygen-rich species at higher ratios was shown to compensate for molecular weight loss. The integration of the N-cyclic quaternary ammonium cations exhibited the potential of functionalized polymers for ion-exchange membrane applications. [ABSTRACT FROM AUTHOR]

The inefficient reuse and recycling of plastics—and the current surge of medical and take-out food packaging use during the pandemic—have exacerbated the environmental burden. This impels the development of alternative recycling/upcycling methods to pivot toward circularity. We report the use of the Mannich three-component coupling reaction for the modification of polystyrene (PS) recovered with a 99.1% yield from waste food containers to form functionalized nitrogen and oxygen-rich PS derivatives. A series of functionalized PS with increasing moles of formaldehyde (F) and morpholine (M) (0.5 × 10−2, 1.0 × 10−2, and 2.0 × 10−2 mol) was achieved using a sol–gel-derived Fe-TiO2 catalyst in a solvent-free, microwave-assisted synthesis. Modified polymers were characterized with viscometry, 1H NMR, 13CNMR (DEPT) FTIR, XPS, UV, and TGA. Functionalization scaled with an increasing ratio, validating the 3CR approach. Further functionalization was constrained by a competing oxidative degradation; however, the varying hydrogen bond density due to nitrogen and oxygen-rich species at higher ratios was shown to compensate for molecular weight loss. The integration of the N-cyclic quaternary ammonium cations exhibited the potential of functionalized polymers for ion-exchange membrane applications.

2‐Methylfuran (MF) is a candidate to be a high‐quality fuel additive. For the first time, efficient Co‐Cu/ZrO2 catalysts were prepared by the sol‐gel method and herein used for MF synthesis from furfural. Although a 9.2% MF yield and no MF was obtained using Cu/ZrO2 and Co/ZrO2, respectively, a 77.5% MF yield was observed at 200°C, under 1.5 MPa initial H2 pressure for 4 hours using a Co‐Cu/ZrO2 catalyst. The Co amount was changed in the catalyst structure and the effect of the Co amount on furfural hydrogenation was investigated. The most effective catalyst was the Co‐Cu/ZrO2 catalyst, with 0.08 g/g (8 mass%) Cu and 0.118 g/g (11.8 mass%) Co. The activity tests of the catalysts were carried out for hydrogenation of furfural to MF by changing reaction parameters such as pressure, loading of catalyst, temperature, and time. A 94.1% MF yield was achieved in the presence of the Co‐Cu/ZrO2 catalyst with 0.08 g/g (8 mass%) Cu and 0.118 g/g (11.8 mass%) Co at 200°C for 6 hours under 1.5 MPa H2 pressure. The catalyst also showed good reusability properties after the fifth use. The catalysts were characterized by Brunauer‐Emmet‐Teller method, X‐ray diffraction, X‐ray photoelectron spectroscopy, and temperature programmed reduction techniques. [ABSTRACT FROM AUTHOR]

First commercialized in the second half of the 1990s as organosilica-entrapped lipases, sol–gel catalysts share several unique properties that make them ideally suited for process chemistry, namely synthetic organic chemistry in the fine chemicals industry. Is their application potential fully realized? What are the obstacles to their widespread uptake in the specialty and fine chemicals industry? Can they also be employed in visible-light photocatalysis? Highlights: Sol–gel catalysts share several unique properties that make them ideally suited for process chemistry. With their high activity and ultralow leaching, these catalysts can often displace homogeneous catalysts as drop-in replacements, requiring little or no changes to existing processes. Production costs lower, thanks to streamlined chemical processes requiring no expensive catalyst–product separation. Sol–gel catalysts are increasingly used by industry but their application potential is far from being fully realized. [ABSTRACT FROM AUTHOR]

Furfuryl alcohol (FA), a valuable compound from furfural (FF) was synthesized by efficient Ni-Cu/ZrO2 catalysts. The catalysts with varying Ni and Cu loading were developed by sol-gel method and characterized by Brunauer-Emmet-Teller (BET) method, X-ray diffraction, Temperature Programmed Reduction (TPR), X-ray photoelectron spectroscopy techniques. Cu/ZrO2 and Ni/ZrO2 catalysts were also tested to compare the effect of the Ni-Cu/ZrO2 catalyst. Both Ni and Cu showed the synergistic effect on FA formation. The Ni-Cu/ZrO2 catalyst was used for hydrogenation of FF by changing pressure, catalyst loading, temperature and time. A 93% FA yield was achieved over the 7Ni-Cu/ZrO2 catalyst with 0.07 g Ni and 0.1 g Cu/1 g ZrO2 at 200 °C for 4 h under 1.5 MPa H2 pressure. The sol-gel Ni-Cu/ZrO2 catalyst without the use of expensive noble metals is effective on the hydrogenation of FF to FA relatively in mildly reaction pressure. The Ni-Cu/ZrO2 catalyst was used for hydrogenation of FF by changing pressure, catalyst loading, temperature and time. A 93% FA yield was achieved over the 7Ni-Cu/ZrO2 catalyst with 0.07 g Ni and 0.1 g Cu/1 g ZrO2 at 200 °C for 4 h under 1.5 MPa H2 pressure. The sol-gel Ni-Cu/ZrO2 catalyst without the use of expensive noble metals is effective on the hydrogenation of FF to FA relatively in mildly reaction pressure. [ABSTRACT FROM AUTHOR]

Sol–gel Ru/SiO2, Co/SiO2, and Ru-Co/SiO2 catalysts were prepared for 5-hydroxymethylfurfural (HMF) hydrogenation to 2,5-dimethylfuran (DMF). Catalysts were characterized by BET, XRD, TPR, TEM, and XPS. Reactions were run with catalysts that were reduced at 500 °C for 1 h. Reaction time, temperature and hydrogen pressure effects were studied for hydrogenation. In the presence of both Ru and Co, the easier reduction was observed at Ru-Co/SiO2 catalyst. Although no DMF yield was observed with Ru/SiO2 and Co/SiO2, 96% DMF was obtained at 180 °C, under 15 bar H2 pressure for 2 h. Moreover >99.9% DMF yield was achieved with Ru-Co/SiO2 at 120 °C for 8 h and at 140 °C for 4 h, respectively. DMF yield did not change significantly after third use, however deactivation was observed after fifth use of catalyst. It may be attributed to oxidation of cobalt active sites during recycle runs. Highlights: A new Sol–gel Ru-Co/SiO2 catalyst was tested for 5-HMF hydrogenation to DMF. >99.9% DMF yield was achieved at 120 °C under 15 bar H2 pressure for 8 h. Synergetic effect was observed between Ru and Co in reduction that affects the catalytic properties. [ABSTRACT FROM AUTHOR]

Abstract: Heterogeneous photocatalysis is a convenient tool for mercury(II) reduction, because it uses inexpensive chemicals and near-UV light. However, structural features of titania (band gap at 3.2eV) make extending its optical absorption in the visible region difficult. This key factor results in low photocatalytic efficiency, as about only 5% of the solar spectrum is used. This study focuses on the characterization and evaluation of the photocatalytic activity of TiO2. The titania preparation method (commercial and sol–gel), the presence of metal on the surface of the oxide (2% wt. Ag), and the calcination temperature (350 and 500°C) were evaluated. The characterization techniques used were: temperature-programmed reduction (TPR), determination of specific surface area (BET method), X-ray diffraction (XRD), scanning electron microscopy (SEM), and photoacoustic spectroscopy. The photocatalytic reduction of Hg2+ to Hg0 was performed by aqueous solution containing formic acid. The results showed that the presence of Ag on the surface of TiO2 (commercial and sol–gel) decreased the band gap energy and increased the photoactivity efficiency, i.e., all the Hg2+ in the solution was reduced to Hg0. [Copyright &y& Elsevier]

Abstract: A 20wt% Co/SiO2 catalyst grafted on a stainless steel substrate was used for Fischer–Tropsch synthesis (FTS) in a micro-chamber reactor. The fabrication of the catalyst was a complex process involving several steps. The first one, the pre-treatment of the AISI316L substrate through a plasma assisted chemical vapour deposition process (PACVD), allowed the formation of a silicon based polymer. This thin polymeric film was thermally degraded into a silicon oxide bonding layer. The coating of this bonding layer with sol–gel precursor of the Co/SiO2 catalysts was done with a spray coating process. The sequential combination of these steps led to a multilayered catalyst with a complex morphology. This material demonstrated high activity under FTS reaction. Activity and selectivity were higher under micro-chamber conditions than in a classical fixed-bed catalytic test. This was attributed to the increase of mass and heat transfers within the micro-device. Moreover distribution of metallic masses within the catalyst showed significant evolutions post FTS, including steel compound migrations and possible cobalt segregation. [Copyright &y& Elsevier]

SiO2 and Al2O3 supported Ni catalysts were synthesized in the form of xerogels: the SiO2 based materials were prepared starting from Ni propionate or glycolate salts and reacting them with tetraethoxysilane (TEOS) in propionic acid, Si(ethylene glycolate) or sodium silicate. The Al2O3 supported catalysts were prepared similarly from Ni propionate salts with Al iso-propoxide salts. Narrow metal particles and strong metal support interactions are observed in the sol-gel catalysts. The metal dispersion was higher for Al2O3 based materials than the SiO2 ones and it deeply depends on the Ni precursor for the silica supported Ni. Wet impregnated oxides with similar Ni loading have higher metal surface area than those from sol-gel processing. The influence of surface differences on the catalytic activity of the materials was studied following the CH4 and CO2 reaction in dry reforming conditions by pulse reaction tests. [ABSTRACT FROM AUTHOR]

Al2O3, CeO2–Al2O3, CeO2–Tb4O7–Al2O3 and ZrO2–Al2O3 supported Pd samples have been prepared by sol–gel methods. Extents and mechanisms of N2O production in CO–NO and CO–NO–O2 reactions on these have been considered. This occurs most selectively under oxidising (lean-burn) conditions or in the presence of CeO2 and CeO2–Tb4O7 promoters near the CO–NO light off temperature. Over Pd/ZrO2–Al2O3 the CO–NO reaction at 573 K has CO and NO conversions that are second order with respect to pCO and pNO. Over this catalyst NO conversion is faster than that of CO until O2(g) is added, causing CO conversion and N2O production at 573 K to rise simultaneously. CeO2 or CeO2–Tb4O7 incorporation into a Pd/Al2O3 catalyst enhances N2O production near the CO–NO light-off temperature in the absence of added O2 without CO conversion being raised. There is current attention on pollution control opportunities through lean-burn conditions, Pd catalysts and oxygen storage capacity enhancement. The present work suggests that their role in N2O production may need to be better understood and controlled. For the moment N2O formation provides a window on mechanisms of TWC operation. [ABSTRACT FROM AUTHOR]