On the role of oxocarbenium ions formed in Brønsted acidic condition on γ-Al2O3 surface in the ring-opening of γ-valerolactone

Mechanistic Approaches toward Rational Design of a Heterogeneous Catalyst for Ring-Opening and Deoxygenation of Biomass-Derived Cyclic Compounds

“…DFT calculations by our group suggested toward the formation of oxocarbenium intermediates on the γ-Al 2 O 3 surface in the presence of the Brønsted acid on the γ-Al 2 O 3 surface, which facilitated ring-opening of GVL leading to higher overall product yield. As shown in Figure (v), ring-opening of the oxocarbenium ion of GVL occurred with a significantly low activation barrier ( E a = 13 kJ/mol) (Figure (v), a to b), leading to the formation of a γ-carbenium ion . This intermediate was unlikely to be formed with the adsorbed GVL structure on the γ-Al 2 O 3 surface in absence of a Brønsted acid.…”

“…(i) Reaction scheme for the conversion of GVL to produce 1-butene (ii) formation of oxocarbenium ions of GVL in the presence of Brønsted acidic proton in water as predicted in ab initio molecular dynamics (AIMD) simulations (iii) reaction energy diagram for GVL ring-opening to 3-pentenoic acid in Brønsted acidic environment (iv) reaction energy diagram for GVL ring-opening to 1-butene on a Lewis acidic γ-Al 2 O 3 surface (v) reaction diagram for GVL ring-opening in the presence of a Brønsted acid via the formation of an oxocarbenium ion to pentenoic acid on the γ-Al 2 O 3 surface. Adapted from references , and .…”

“…As shown in Figure 1(v), ringopening of the oxocarbenium ion of GVL occurred with a significantly low activation barrier (E a = 13 kJ/mol) (Figure 1(v), a to b), leading to the formation of a γ-carbenium ion. 44 This intermediate was unlikely to be formed with the adsorbed GVL structure on the γ-Al 2 O 3 surface in absence of a Brønsted acid. Bond et al 45 also suggested γ-carbenium ion as an intermediate in the ring-opening of GVL in the presence of the Brønsted acid.…”

“…42 Total C 4 product yield was observed to increase to 80% on adding 20 wt % WO x to γ-Al 2 O 3 . DFT calculations by our group 44 suggested toward the formation of oxocarbenium intermediates on the γ-Al 2 O 3 surface in the presence of the Brønsted acid on the γ-Al 2 O 3 surface, which facilitated ring-opening of GVL leading to higher overall product yield. As shown in Figure 1(v), ringopening of the oxocarbenium ion of GVL occurred with a significantly low activation barrier (E a = 13 kJ/mol) (Figure 1(v), a to b), leading to the formation of a γ-carbenium ion.…”

High Aluminum Content Beta Zeolite as an Active Lewis Acid Catalyst for γ-Valerolactone Decarboxylation

“…GVL decarboxylation reaction occurred under harsh conditions (e.g., 350 °C or high pressure) due to the low activity of the catalysts used before. A number of materials have been used for catalyzing the GVL decarboxylation reaction, including ZSM-5 zeolites, ASA (amorphous silica–alumina), − , γ-Al 2 O 3 , ,, and supported catalysts. , Among these samples, the high Al ZSM-5 sample (H-ZSM-5-30) was the most active sample for GVL decarboxylation reaction due to the abundant Brønsted acid sites and intrinsic activity of crystalline materials . Even though many kinds of solid acids have been used for GVL decarboxylation, Lewis acid zeolites used for this reaction have not been reported. − …”