d-Glucose Isomerization with PAMAM Dendrimers as Environmentally Friendly Catalysts

Abstract

The isomerization of D-glucose to D-fructose plays a key role in the biochemical and chemical conversion of biomass, and it is therefore desirable to develop and improve catalysts for this reaction. In this study, the environmentally friendly polymer poly(amidoamine) (PAMAM) dendrimer's properties as catalysts for this isomerization are investigated. The experimental results showed that the PAMAM dendrimers, which have basic terminal groups, can effectively promote the D-glucose isomerization reaction. Under the optimized reaction conditions, D-fructose was generated with a 20% maximum yield and above 90% selectivity. 13C and 2 H isotope experiments by NMR were carried out to explore the reaction mechanism. When the reaction was performed in D 2 O, the C1 signal of D-fructose changed to a triplet, which confirmed that the C1 carbon binds to a deuterium atom, i.e., isotopic exchange. It was also found that the deuterium atom at the C2 position of D-glucose-2-d 1 cannot transfer to D-fructose. These data indicate that PAMAM dendrimers catalyze D-glucose isomerization through a mechanism, which includes deprotonation, formation of ene-diol intermediate, and proton exchange with the solvent.

Solvent Effects Enable Efficient Tandem Conversion of Cellulose and Its Monosaccharides Towards 5‐Hydroxymethylfurfural

“…Solvent composition has been shown to significantly affect the reaction process, and a rational design on solvent composition can increase the catalytic activity through lowering the reaction energy barrier and improving reaction rates. [57] Song et al [58] investigated the solvent effect of GVL on the generation of HMF from glucose. They found that the addition of GVL into H 2 O could significantly regulate the reaction rate, and distinct decreases in isomerization rate constants and increases in dehydration rate constants could be observed even in 1 % GVL/ H 2 O, as shown in Figure 5.…”

“…Solvent composition has been shown to significantly affect the reaction process, and a rational design on solvent composition can increase the catalytic activity through lowering the reaction energy barrier and improving reaction rates [57] . Song et al [58] .…”

Revealing the contributions of homogeneous and heterogeneous catalysis to isomerization of d-glucose into d-fructose in the presence of basic salts with low solubility

“…15 Solid bases 16 and solid Lewis acids 17 exhibit comparable catalytic activity for the isomerization though the Lewis acids catalyze co-formation of d -mannose in somewhat higher amounts. A broad range of solid bases exhibit catalytic activity for the isomerization, which includes MgO 14,18,19 and other alkaline earth metal (hydr)oxides, 20 MgO-doped ordered mesoporous carbon, 21 Mg–Al hydrotalcites, 14,15,18,22–30 Mg- or Ca-impregnated or exchanged zeolites, 31–35 attapulgite, 36,37 MgO–Nb phosphate, 38 Mg-doped carbon nitride, 39 Mg-containing titanosilicates, 40 CaO–ZrO 2 , 41 MgO–ZrO 2 , 42 MgO/biochar, 43 CaO–Al 2 O 3 , 44 CaO–MgO, 45 CaO/C, 46 alkaline earth metal titanates, 47 soluble amines 48–58 and N-containing solid catalysts, 50,51,54,55,59–63 silicates, 64 SiO 2 treated with ammonia, 65 zirconium carbonate, 66 ZrO 2 67 and basic hybrid catalysts. 68 Nevertheless, establishing structure–activity and structure-selectivity correlations between the textural properties of materials and their catalytic performance remains challenging.…”

Aqueous Isomerization of Glucose to Fructose Catalyzed by Guanidinium Ionic Liquids

“…Under optimized reaction conditions, D-fructose was generated with a maximum fructose yield of 20 %. [25] Amidoximated polyacrylonitrile with an amidoxime functional group was also used as an active heterogeneous catalyst for the isomerization of glucose to fructose. [26] Besides these organic bases, inorganic bases were used in the isomerization of glucose as well.…”

“…The poly(amidoamine) dendrimers, which have basic terminal groups, can also effectively promote the isomerization reaction of glucose. Under optimized reaction conditions, D‐fructose was generated with a maximum fructose yield of 20 % [25] . Amidoximated polyacrylonitrile with an amidoxime functional group was also used as an active heterogeneous catalyst for the isomerization of glucose to fructose [26] .…”