Batch and Continuous‐Flow Preparation of Biomass‐Derived Furfural Acetals over a TiO₂ Nanoparticle‐Exfoliated Montmorillonite Composite Catalyst

Abstract

Furfural acetals with high octane value, high calorific value and high oxidation resistance are considered promising biofuels or fuel precursors with huge potential demand. However, there are few studies on efficient scalable catalyst systems, including continuous-flow catalyst systems, for their preparation. In this work, TiO 2 nanoparticles supported on exfoliated montmorillonite, with strong Lewis acid sites and abundant accessible Brønsted acid sites, is used to catalyze the acetalization reactions of biomass-derived furfural and alcohols. Low dosage of the catalyst made the reaction reach equilibrium in a very short time (TOF = 690-1305 min À 1 ) at room temperature with the acetal as the only product. In continuous-flow reactions, the catalyst showed a stable product output with conversion close to that for the batch reaction with a short catalyst-reactant contact time of 150 s. Contrast experiments revealed that both Lewis and Brønsted acid sites on the catalyst were indispensable for maximizing the catalytic performance, and simultaneously activating both furfural and alcohol on the adjacent Lewis and Brønsted acid sites was proposed to be responsible for the high catalytic performance.

Nano‐Au Anchored in Organic Base Group‐Grafted Silica Aerogel: A Durable and Robust Catalysts for Green Oxidative Esterification of Furfural

“…The peaks at 1541 cm À 1 , 1440 cm À 1 , and 1490 cm À 1 are the characteristic peaks of pyridine interacting with Brønsted acidic sites, Lewis acidic sites, and both Lewis and Brønsted acidic sites, respectively. [29] Both SAÀ 10 %Au and SAÀ NH 2 -10 %Au showed a obvious peak related to the Lewis acid sites, while SAÀ NH 2 did not show any obvious peaks corresponding to Lewis or Brønsted acid sites, indicating its very weak acidity. Moreover, the characteristic peak area is proportional to the amount of acidic sites, and the acid contents calculated at 150 °C, 250 °C and 350 °C correspond to the total number of acid sites, the number of medium and strong acid sites, and that of strong acid sites, [29] respectively (Table 2).…”

“…[29] Both SAÀ 10 %Au and SAÀ NH 2 -10 %Au showed a obvious peak related to the Lewis acid sites, while SAÀ NH 2 did not show any obvious peaks corresponding to Lewis or Brønsted acid sites, indicating its very weak acidity. Moreover, the characteristic peak area is proportional to the amount of acidic sites, and the acid contents calculated at 150 °C, 250 °C and 350 °C correspond to the total number of acid sites, the number of medium and strong acid sites, and that of strong acid sites, [29] respectively (Table 2). Obviously, the numbers of total acid sites and Lewis acid sites in SAÀ 10 %Au and SAÀ NH 2 À 10 %Au, respectively, are ChemCatChem much higher than those in SAÀ NH 2 , manifesting that the Lewis acid sites mainly come from Au.…”

“…With respect to SAÀ NH 2 -10 %Au, the selectivity to MF reached 100 % [a] The acid contents at 150 °C, 250 °C and 350 °C correspond to the total number of acid sites, the number of medium and strong acid sites, and that of strong acid sites, respectively. [29]…”

“…In N 2 atmosphere, MF, the product of oxidative esterification reaction, was obtained with a yield of 3 % over SAÀ NH 2 À 10 %Au (Figure 7c), which is consistent with the result reported in the literature, [10d] indicating that the catalytic reaction follows a path of oxidative dehydrogenation. [10d] The yield of FDMA, obtained through Lewis acid or Brønsted acid catalysis, [29] was also very low (3 %), demonstrating that the Lewis acid sites of SAÀ NH 2 À 10 %Au can not effectively catalyze the acetalation of furfural. However, the yield of FDMA is 61 % in 1 MPa of O 2 atmosphere, revealing that the existence of O 2 promoted the acetalization reaction over SAÀ NH 2 À 10 %Au.…”

Direct Diels-Alder reaction of chitin derived 3-acetamido-5-acetylfuran

“…materials, energy, drug discovery). 3,[5][6][7][8][9][10][11][12][13][14][15][16][17] Importantly, furfural/HMF derivatives undergo reversible DA with dienophiles to yield 7oxanorbornenes . This dynamic character has solely led to extensive research on understanding interactions and mechanistic nuances governing furan diene/dienophile DA and fine tuning reactants to bypass reactivity stability of the 7-ONB products issues (Scheme 1A).…”