Abstract:The transition metal catalysed epoxidation of methyl oleate 1 by hydrogen peroxide was investigated using Ru(acac)3/dipicolinic acid as catalyst. Under optimised reaction conditions, the epoxidised methyl oleate 2 was obtained with a quantitative yield in short reaction time and under mild reaction conditions.Practical applications: Epoxidised fatty acids and their derivatives are produced by the Prilezhaev reaction and used in various applications in the chemical industry. Due to the known drawbacks of epoxid… Show more
“…1 ; Additional file 1 : Table S1). This strategy has also been reported in the literature where H 2 O 2 was added in a fed-batch manner to avoid its unproductive decomposition during epoxidation [ 30 – 32 ] and hydroxylation [ 33 – 35 ] reactions. Fig.…”
BackgroundStrategies to improve copper-catalyzed alkaline hydrogen peroxide (Cu-AHP) pretreatment of hybrid poplar were investigated. These improvements included a combination of increasing hydrolysis yields, while simultaneously decreasing process inputs through (i) more efficient utilization of H2O2 and (ii) the addition of an alkaline extraction step prior to the metal-catalyzed AHP pretreatment. We hypothesized that utilizing this improved process could substantially lower the chemical inputs needed during pretreatment.ResultsHybrid poplar was pretreated utilizing a modified process in which an alkaline extraction step was incorporated prior to the Cu-AHP treatment step and H2O2 was added batch-wise over the course of 10 h. Our results revealed that the alkaline pre-extraction step improved both lignin and xylan solubilization, which ultimately led to improved glucose (86 %) and xylose (95 %) yields following enzymatic hydrolysis. An increase in the lignin solubilization was also observed with fed-batch H2O2 addition relative to batch-only addition, which again resulted in increased glucose and xylose yields (77 and 93 % versus 63 and 74 %, respectively). Importantly, combining these strategies led to significantly improved sugar yields (96 % glucose and 94 % xylose) following enzymatic hydrolysis. In addition, we found that we could substantially lower the chemical inputs (enzyme, H2O2, and catalyst), while still maintaining high product yields utilizing the improved Cu-AHP process. This pretreatment also provided a relatively pure lignin stream consisting of ≥90 % Klason lignin and only 3 % xylan and 2 % ash following precipitation. Two-dimensional heteronuclear single-quantum coherence (2D HSQC) NMR and size-exclusion chromatography demonstrated that the solubilized lignin was high molecular weight (Mw ≈ 22,000 Da) and only slightly oxidized relative to lignin from untreated poplar.ConclusionsThis study demonstrated that the fed-batch, two-stage Cu-AHP pretreatment process was effective in pretreating hybrid poplar for its conversion into fermentable sugars. Results showed sugar yields near the theoretical maximum were achieved from enzymatically hydrolyzed hybrid poplar by incorporating an alkaline extraction step prior to pretreatment and by efficiently utilizing H2O2 during the Cu-AHP process. Significantly, this study reports high sugar yields from woody biomass treated with an AHP pretreatment under mild reaction conditions.Electronic supplementary materialThe online version of this article (doi:10.1186/s13068-016-0442-0) contains supplementary material, which is available to authorized users.
“…1 ; Additional file 1 : Table S1). This strategy has also been reported in the literature where H 2 O 2 was added in a fed-batch manner to avoid its unproductive decomposition during epoxidation [ 30 – 32 ] and hydroxylation [ 33 – 35 ] reactions. Fig.…”
BackgroundStrategies to improve copper-catalyzed alkaline hydrogen peroxide (Cu-AHP) pretreatment of hybrid poplar were investigated. These improvements included a combination of increasing hydrolysis yields, while simultaneously decreasing process inputs through (i) more efficient utilization of H2O2 and (ii) the addition of an alkaline extraction step prior to the metal-catalyzed AHP pretreatment. We hypothesized that utilizing this improved process could substantially lower the chemical inputs needed during pretreatment.ResultsHybrid poplar was pretreated utilizing a modified process in which an alkaline extraction step was incorporated prior to the Cu-AHP treatment step and H2O2 was added batch-wise over the course of 10 h. Our results revealed that the alkaline pre-extraction step improved both lignin and xylan solubilization, which ultimately led to improved glucose (86 %) and xylose (95 %) yields following enzymatic hydrolysis. An increase in the lignin solubilization was also observed with fed-batch H2O2 addition relative to batch-only addition, which again resulted in increased glucose and xylose yields (77 and 93 % versus 63 and 74 %, respectively). Importantly, combining these strategies led to significantly improved sugar yields (96 % glucose and 94 % xylose) following enzymatic hydrolysis. In addition, we found that we could substantially lower the chemical inputs (enzyme, H2O2, and catalyst), while still maintaining high product yields utilizing the improved Cu-AHP process. This pretreatment also provided a relatively pure lignin stream consisting of ≥90 % Klason lignin and only 3 % xylan and 2 % ash following precipitation. Two-dimensional heteronuclear single-quantum coherence (2D HSQC) NMR and size-exclusion chromatography demonstrated that the solubilized lignin was high molecular weight (Mw ≈ 22,000 Da) and only slightly oxidized relative to lignin from untreated poplar.ConclusionsThis study demonstrated that the fed-batch, two-stage Cu-AHP pretreatment process was effective in pretreating hybrid poplar for its conversion into fermentable sugars. Results showed sugar yields near the theoretical maximum were achieved from enzymatically hydrolyzed hybrid poplar by incorporating an alkaline extraction step prior to pretreatment and by efficiently utilizing H2O2 during the Cu-AHP process. Significantly, this study reports high sugar yields from woody biomass treated with an AHP pretreatment under mild reaction conditions.Electronic supplementary materialThe online version of this article (doi:10.1186/s13068-016-0442-0) contains supplementary material, which is available to authorized users.
“…Product 11 j (590 mg, 3.35 mmol, 89 %) was obtained as ac olorless solid. 1 Methyl8 -(5-octyl-2-oxo-1,3-dioxolan-4-yl)octanoate(11 k) [48a] Compounds 10 k [63] (1.10 g, 3.53 mmol) and 3f (66.0 mg, 0.176 mmol) were charged into in a4 5cm 3 stainless-steel reactor equipped with am agnetic stirrer.T he reactor was sealed and charged with 3.5 MPa CO 2 until equilibrium was reached. The reactor was heated to 100 8Cf or 24 ha nd the CO 2 pressure was kept constant at 5.0 MPa.…”
Numerous bifunctional organocatalysts were synthesized and tested for the atom-efficient addition of carbon dioxide and epoxides to produce cyclic carbonates. These catalysts are based on phosphonium salts containing an alcohol moiety in the side chain for substrate activation through hydrogen bonding. In the model reaction, converting 1,2-butylene oxide with CO2 , 19 catalysts were tested to determine structure-activity relationships. In total, 28 epoxides were converted with CO2 to give the respective cyclic carbonates in yields of up to 99%. Even at 45 °C, the most active catalyst was able to produce cyclic carbonates selectively in high yields. The carbonates were generally obtained as analytically pure products after simple filtration over silica gel. This single-component catalyst system works under neat and mild reaction conditions and tolerates several useful moieties.
“…The insertion of CO 2 into epoxidized methyl oleate cis ‐ 1 a to produce carbonated methyl oleate 2 a was chosen as the test reaction for the synthesis of carbonated oleochemicals 2 under solvent‐free conditions (Scheme ). The (racemic) test substrate cis ‐ 1 a is commercially available but can also be easily prepared through H 2 O 2 oxidation of methyl oleate . Depending on the reaction conditions and catalyst chemo‐ and stereoselectivity issues might arise.…”
Section: Methodsmentioning
confidence: 99%
“…The (racemic) test substrate cis-1a is commercially available but can also be easily prepared throughH 2 O 2 oxidation of methyl oleate. [17] Depending on the reactionc onditions and catalystc hemo-and stereoselectivity issues might arise. Although diastereomerically pure cis-1a is employed as starting material, the formation of cis-a nd trans-2a might be observed.…”
Bifunctional phosphorus-based organocatalysts proved to be highly efficient for the atom-economic reaction of CO and epoxidized oleochemicals. Notably, those products are obtained from CO and renewable feedstocks only. Structure-activity relationships have been deduced from a screening of 22 organocatalysts in a test reaction. Bifunctional catalysts based on a phosphonium salt bearing a simple phenolic moiety proved to be extraordinarily active under comparatively mild and solvent-free reaction conditions. In the presence of the most active organocatalyst 12 oleochemical carbonates were isolated in excellent yields up to 99 %. This organocatalyzed reaction represents an excellent example for the realization of the 12 Principles of Green Chemistry as well as the 12 Principles of CO Chemistry.
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