Daiyu Song

Pore morphology-controlled preparation of ZrO2-based hybrid catalysts functionalized by both organosilica moieties and Keggin-type heteropoly acid for the synthesis of levulinate esters

A series of ZrO2-based hybrid catalysts functionalized by both organosilica groups and Keggin type heteropolyacid, H3PW12O40/ZrO2–Si(Et/Ph)Si and H3PW12O40/ZrO2–Si(Ph), with different structural orderings and pore geometries were controllably prepared by a one-pot template-assisted sol–gel co-condensation–hydrothermal treatment route. The pore morphologies, textural properties and acidity of as-prepared hybrid catalysts were characterized by XRD, TEM, nitrogen gas porosimetry, in situ pyridine-FTIR spectroscopy and titration, while the structural integrity of the incorporated functionalities was studied by FT-IR, 31P MAS NMR, 13C CP-MAS NMR and 29Si MAS NMR. As the novel solid acid catalysts, the catalytic performance of as-prepared materials was evaluated by esterification of levulinic acid with various alcohols under mild conditions. Meanwhile, comparative studies were carried out to find out the influences of acidity, porosity and surface hydrophobicity on the catalytic activity of the catalysts. Finally, the recyclability of the catalysts was tested.

Design of a highly ordered mesoporous H3PW12O40/ZrO2–Si(Ph)Si hybrid catalyst for methyl levulinate synthesis

A highly ordered mesoporous ZrO2-based material functionalized by benzene-bridged organosilica groups and the Keggin type heteropolyacid, prepared in a single co-condensation–hydrothermal treatment step, exhibited much higher catalytic activity towards methyl levulinate synthesis compared to alkyl-free H3PW12O40/ZrO2.

Design of organosulfonic acid functionalized organosilica hollow nanospheres for efficient conversion of furfural alcohol to ethyl levulinate

A series of propylsulfonic or arenesulfonic acid functionalized ethane- or benzene-bridged organosilica hollow nanospheres (Pr/ArSO3H-Et/Ph-HNS) were demonstrated by a one-step condensation method combined with in situ H2O2 oxidation. The key preparation route included using nonionic surfactant F127 as the soft template, 1,3,5-trimethylbenzene as the micelle expanding agent and adjusting suitable molar ratios of total Si to F127 in the initial gel mixture. The inner diameter of the Pr/ArSO3H-Et/Ph-HNS materials was ca. 10 nm, and their shell thickness was ca. 3–5 nm. As the novel organic–inorganic hybrid solid acid catalysts, the catalytic activity of the Pr/ArSO3H-Et/Ph-HNS was evaluated by ethanolysis of biomass-derived furfural alcohol to ethyl levulinate. The obtained acid catalytic activity that was superior to that of their bulk mesoporous counterparts was explained in terms of their strong Bronsted acidity and unique hollow nanospherical morphology. Finally, the recyclability of the hybrid catalysts was studied through four consecutive catalytic runs.

Morphology Tailoring of Sulfonic Acid Functionalized Organosilica Nanohybrids for the Synthesis of Biomass‐Derived Alkyl Levulinates

Morphology evolution of sulfonic acid functionalized organosilica nanohybrids (Si(Et)Si-Pr/ArSO3 H) with a 1D tubular structure (inner diameter of ca. 5 nm), a 2D hexagonal mesostructure (pore diameter of ca. 5 nm), and a 3D hollow spherical structure (shell thickness of 2-3 nm and inner diameter of ca. 15 nm) was successfully realized through P123-templated sol-gel cocondensation strategies and fine-tuning of the acidity followed by aging or a hydrothermal treatment. The Si(Et)Si-Pr/ArSO3 H nanohybrids were applied in synthesis of alkyl levulinates from the esterification of levulinic acid and ethanolysis of furfural alcohol. Hollow spherical Si(Et)Si-Pr/ArSO3 H and hexagonal mesoporous analogues exhibited the highest and lowest catalytic activity, respectively, among three types of nanohybrids; additionally, the activity was influenced by the -SO3 H loading. The activity differences are explained in terms of different Brønsted acid and textural properties, reactant/product diffusion, and mass transfer rate, as well as accessibility of -SO3 H sites to the reactant molecules. The reusability of the nanohybrids was also evaluated.

Heteropoly acid and ZrO2 bifunctionalized organosilica hollow nanospheres for esterification and transesterification

Single-micelle-templated preparation of heteropoly acid and ZrO2 bifunctionalized organosilica hollow nanospheres (H3PW12O40/ZrO2-Et-HNS) is developed by co-hydrolysis and -condensation of bissilylated organic precursor, 1,2-bis(trimethoxysilyl)ethane (BTMSE), with a zirconium source (Zr(OC4H9)4) in the presence of H3PW12O40, triblock copolymer surfactant F127 and 1,3,5-trimethylbenzene (TMB) followed by boiling ethanol washing. Through tuning the molar ratios of Si/Zr in the initial gel mixture, the morphology transformation from the 3D interconnected mesostructure to the hollow spherical nanostructure is realized. The inner diameter of the H3PW12O40/ZrO2-Et-HNS materials is in the range of 6–12 nm, and their shell thickness is ca. 2 nm. As novel organic–inorganic hybrid catalysts, the catalytic activity of H3PW12O40/ZrO2-Et-HNS is evaluated by the model reactions of esterification of levulinic acid (LA) with methanol to methyl levulinate and transesterification of yellow horn oil with methanol to biodiesel at refluxing temperature (65 °C) and atmospheric pressure. The obtained excellent heterogeneous acid catalytic activity of H3PW12O40/ZrO2-Et-HNS is explained in terms of their strong Bronsted and Lewis acidity, unique hollow nanospherical morphology and hydrophobic surface. Finally, the recyclability of the hybrid catalysts is tested through three consecutive catalytic runs.

Ethane-Bridged Organosilica Nanotubes Functionalized with Arenesulfonic Acid and Phenyl Groups for the Efficient Conversion of Levulinic Acid or Furfuryl Alcohol to Ethyl Levulinate

A series of ethane‐bridged organosilica nanotubes functionalized with arenesulfonic acid and phenyl groups (ArSO3H‐Si(Et)Si‐Ph‐NTs) was fabricated successfully by a P123‐directed sol–gel co‐condensation route combined with hydrothermal treatment with a carefully adjusted P123‐to‐bis‐silylated organic precursor‐to‐HCl molar ratio in the starting system. The morphological characteristics, textural properties, Brønsted acidity, surface hydrophobicity, and structural integrity of the carbon/silica framework were characterized. The ArSO3H‐Si(Et)Si‐Ph‐NTs materials were applied in the synthesis of ethyl levulinate from the esterification of levulinic acid and the ethanolysis of furfuryl alcohol, and the excellent catalytic activity was explained in terms of the strong Brønsted acidity, unique hollow nanotube morphology, and enhanced surface hydrophobicity. Reusability tests confirmed that ArSO3H‐Si(Et)Si‐Ph‐NTs can be reused for three or five times without a significant loss of activity.

Design of Ordered Mesoporous Sulfonic Acid Functionalized ZrO2/organosilica Bifunctional Catalysts for Direct Catalytic Conversion of Glucose to Ethyl Levulinate

Ordered mesoporous sulfonic acid functionalized ZrO2/organosilica catalysts (SO42−/ZrO2‐PMO‐SO3H) bearing tunable Brønsted, and Lewis acid site distributions were prepared by a P123‐directed sol‐gel co‐condensation route followed by ClSO3H functionalization. As‐prepared catalysts were applied in the conversion of glucose to ethyl levulinate in ethanol medium. The SO42−/ZrO2‐PMO‐SO3H‐catalyzed target reaction followed a glucose‐ethyl glucoside‐ethyl fructoside‐5‐ethoxymethylfurfural‐ethyl levulinate pathway dominated by the synergistic effect of the super strong Brønsted acidity, and moderate Lewis acidity of the catalysts. Additionally, by combining the advantages of the considerably high Brønsted (696 μeq g−1), Lewis acid site density (703 μeq g−1), optimal Brønsted/Lewis molar ratio (0.99), and excellent porosity properties, the SO42−/ZrO2‐PMO‐SO3H1.0 obtained at an initial Si/Zr molar ratio of 1.0 exhibited the highest ethyl levulinate yield (42.3 %) among the various tested catalysts. Moreover, the SO42−/ZrO2‐PMO‐SO3H can be reused three times without obvious changes in activity, morphology, and chemical structure.