Enhanced Transfer Hydrogenation Activity of Zr‐Doped Mesoporous Silica through Sol‐Gel Method for the Reduction of Biomass‐Derived Unsaturated Carbon‐Oxygen Bonds

Abstract

Efficient reduction of unsaturated functionalities of biomass derived molecules enables the production of new value‐added chemical. Herein, we reported a highly efficient and robust mesoporous silica catalyst (SBA‐15) doped with Zr metal sites for the reduction of biomass derived unsaturated molecules through transfer hydrogenation reaction. Specifically, ethyl levulinate was selected as model compound to investigate the reduction activities of the as‐prepared catalysts. An almost quantitative γ‐valerolactone (GVL) yield of 99%, through the ketone reduction and intramolecular cyclisation, was obtained at 160 °C for 18 h in the presence of hydrogenation donor 2‐Butanol (2‐BuOH). Comparative experiments among different type of Zr catalysts showed that the mesoporous structure of SBA‐15 was beneficial for maximizing the activity and the stability of the Zr sites though highly metal dispersion and metal‐chelation effect, respectively. Detailed studies on the catalyst characterization and optimization revealed the ratio of Si/Zr also affected the above reactivity. Mechanistic studies revealed that the interaction between polar C=O group was key to the reaction efficiency and poisoning experiments confirmed the existence of acid‐base sites for transfer hydrogenation process. The catalyst was also successfully recycled without much loss in reactivity. Finally, the catalyst was also applied to the reduction of a variety of unsaturated molecules with high yields.

Mechanistic Insights into the Solvent-Driven Adsorptive Hydrodeoxygenation of Biomass Derived Levulinate Acid/Ester to 2-Methyltetrahydrofuran over Bimetallic Cu–Ni Catalysts

“…The aqueous phase reforming (APR) process allows the mild and selective conversion of lignocellulose to versatile value-added chemicals and fuel molecules that has greatly enriched the downstream chemical family. , Several building blocks were selected by the US Department of Energy as platform molecules, which can be readily prepared from raw biomass and further converted to multifunctional chemicals through different technologies . Levulinic acid (LA) and its esters were included as platform molecules due to their ease of scale-up production via acid-hydrolysis/alcoholysis from carbohydrates and high reactivity to be transformed into a wide range of chemicals such as γ-valerolactone, − 2-methyltetrahydrofuran (2-MTHF), 1,4-pentanediol (1,4-PeD), , and valerate acid/ester. − Particularly, 2-methyltetrahydrofuran (2-MTHF) has drawn much attention as a fuel molecule, possessing good hydrophobicity, high heating value, and a suitable octane number, indicating that it can be directly blended up to 70% of regular gasoline …”

Hafnium-Doped Mesoporous Silica as Efficient Lewis Acidic Catalyst for Friedel–Crafts Alkylation Reactions

“…In the small angle XRD spectra, all Hf/SBA-15 catalysts showed three diffraction peaks around 0.9°, 1.6°, and 1.8°, which can be assigned to the (100), (110), and (200) diffraction peaks of a two-dimensional (2D) hexagonal p6mm structure, respectively. They were also the characteristic patterns of SBA-15, furthering confirming the successful construction of the SBA-15 framework [20]. In addition, the orderliness of the SBA-15 structure was well reserved after the incorporation of Hf metal, which might benefit the mass diffusion within the catalyst’s structure during the reaction.…”

Micro/mesoporous LTL derived materials for catalytic transfer hydrogenation and acid reactions of bio-based levulinic acid and furanics

“…To the best of our knowledge, this is the first study for LTL zeotype catalysts for LA conversion to GVL. Supplementary Table S4 further compares the catalytic performance of yHf-D-HL(x) to literature data for the reaction of LA to GVL, in the presence of micro/mesoporous zeotypes or mesoporous silicas/silicates, using an alcohol as reducing agent ( Kuwahara et al, 2014 ; Antunes et al, 2015 , 2016a , 2016b ; Hengne et al, 2016 ; Winoto et al, 2016 ; Kuwahara et al, 2017 ; Xu et al, 2017 ; Zhou et al, 2018 ; Kumar and Srivastava, 2019 ; Morales et al, 2019 ; Tang et al, 2019 ; He et al, 2020 ; Kumaravel et al, 2020 ; López-Aguado et al, 2020 ; García et al, 2021 ; Ostovar et al, 2021 ; Antunes et al, 2022a ). The different studies were carried out using different reaction conditions, making it difficult to establish clear comparisons.…”

“…Without considering the differences in reaction conditions, and based solely on GVL yields, the best result for 0.28Hf-D-HL(0.28) (91% GVL yield, entry 5) was comparable to some of the best results indicated in Supplementary Table S4 . GVL yields of at least 90% were reported for micro/mesoporous zeotypes such as Hf-WdeSAlBeta-m (entry 7) ( Antunes et al, 2022a ), Hf-USY (entry 17) ( Tang et al, 2019 ) and Zr-AlBeta (entry 11) ( López-Aguado et al, 2020 ) which led to 99% (180°C/24 h), 95% (150°C/10 h) and 92% GVL yield (170°C/6 h), respectively, and some Zr-containing mesoporous SBA-15 type catalysts (synthesized using the relatively expensive polymeric template Pluronic P123) which led to 90–95% GVL yield (entries 19, 20) ( Kuwahara et al, 2014 , 2017 ; Zhou et al, 2018 ). Catalyst 1.12Hf-D-HL(0.28) led to 64% GVL yield at 200°C/1 h ( Figure 9B ), which was higher than that reported for Ni-Sepiolite (<1% yield at 180°C/2 h, entry 25) ( García et al, 2021 ).…”