Selectively converting glucose to fructose using immobilized tertiary amines

MgO‐ZrO2 Mixed Oxides as Effective and Reusable Base Catalysts for Glucose Isomerization into Fructose in Aqueous Media

“…Particularly for the MgO-containing catalysts,t he initial rates show al inear increaset oamaximumo f6 3mmol min À1 g À1 with increasing catalyst basicity.A ll the catalysts exhibited almost the same turnover frequency (TOF,d etermined from initial rate of isomerization divided by total basicity given in Table 2) of % 7h À1 independents of Mg/Zr ratio, which is highert han that of the homogeneous AlCl 3 (1.6 h À1 )o rCrCl 3 (5.7 h À1 )c atalysts [30] and the heterogeneouss ilica-immobilized amine ( % 2.9h À1 ). [21] TheseT OFs results revealed that all the MgO-containing catalysts (i.e. as-prepared xMZ catalysts)h avet he same nature of active sites, consistentw ith FTIR which shows similar structural features in all the MgO-containing catalysts, and confirms imilar conclusion reported recently.…”

“…Particularly for the MgO‐containing catalysts, the initial rates show a linear increase to a maximum of 63 μmol min −1 g −1 with increasing catalyst basicity. All the catalysts exhibited almost the same turnover frequency (TOF, determined from initial rate of isomerization divided by total basicity given in Table ) of ≈7 h −1 independents of Mg/Zr ratio, which is higher than that of the homogeneous AlCl 3 (1.6 h −1 ) or CrCl 3 (5.7 h −1 ) catalysts and the heterogeneous silica‐immobilized amine (≈2.9 h −1 ) …”

“…Other types of heterogeneous catalysts such as alkali metal and alkaline earth metal titanates, metallosilicates, anion‐exchange resins, magnesium oxide, zirconium oxide, zirconium carbonate and immobilized amines have been investigated as efficient isomerization catalysts. Among them, interestingly, pure zirconia is found to be a good catalyst for glucose isomerization to fructose in the water affording 15 % yield for fructose at 200 °C, and the authors attributed its reactivity to the presence of basic active sites .…”

Examining Acid Formation During the Selective Dehydration of Fructose to 5‐Hydroxymethylfurfural in Dimethyl Sulfoxide and Water

“…[19] However,t he presence of base does not accurately capturet he reaction environment investigated because no base is presenti no ur baseline dehydration tests. [41,45,46] As an alternative, the post-reaction mixtures were analyzed by using a barium chloride precipitation test that is specific for sulfate ions in solution. [11] In addition, base is able to catalyzef ructosei somerization to glucose.…”

“…[19-21, 35, 36] Severalh ypotheses have been proposed by researchers to explain this increased reactivity in DMSO, including DMSO stabilization of transition states that reduces the reaction energy barrier and increases the rate of reaction, [10,37] DMSO acting as a catalystb yi nitiating hydroxy dehydration from fructose, [25,30] or DMSO degrading in situ into sulfuric acid, which is capable of catalyzing the reaction. Eliminating acid species could be beneficial in the eventt hat biomass processing of glucoset of ructose to HMF is performed in ac ascade manner using immobilized amines to catalyzet he isomerization of glucose [41] in water,w hichi sa lso the solvent of choicef or upstreamp rocesses. If DMSO is stabilizing transitions tates or acting as ac atalyst, an efficient catalystw ould potentially consist of sulfoxide speciest hat would provide the necessary interactions to promote selective dehydration.…”