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Renewable chemicals: dehydroxylation of glycerol and polyols.

ten Dam J, Hanefeld U - ChemSusChem (2011)

Bottom Line: This new chemical toolbox needs to be designed to guarantee the demands of future generations at a reasonable price.The surplus of functionality in sugars and glycerol consists of alcohol groups.To yield suitable renewable chemicals these natural products need to be defunctionalized by means of dehydroxylation.

View Article: PubMed Central - PubMed

Affiliation: Gebouw voor Scheikunde, Afdeling Biotechnologie, Technische Universiteit Delft, Julianalaan 136, 2628 BL Delft, The Netherlands.

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Homolytic cleavage of hydrogen on platinum and subsequent spillover.
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fig02: Homolytic cleavage of hydrogen on platinum and subsequent spillover.

Mentions: Qin et al. also used Pt/WO3/ZrO2 as a catalyst. Using a fixed-bed reactor they were able to obtain both high conversion (70 %) and good 13PD selectivity (46 %) using aqueous glycerol at only 403 K (Table 2, entry 19).[54] The authors ascribe the low reaction temperature to the ability of the catalyst to activate hydrogen as proton and hydride. First, hydrogen is homolytically split into hydrogen atoms (1, Figure 2), which can spillover onto the WO3/ZrO2 surface (2, Figure 2). Here the hydrogen atom can donate an electron to a Lewis acidic site, generating a proton (3, Figure 2). This proton can be transferred to the substrate alcohol and a second hydrogen atom, acting as an acid, combines with the electron to form a hydride (4, Figure 2), stabilized on the Lewis acid site. This hydride is then finally used as a reductant.[62, 63] This hypothesis is supported by NH3 chemisorption measurements using supports that were calcined at different temperatures. Increasing the calcination temperature leads to higher acidity, resulting in higher conversion.[54]


Renewable chemicals: dehydroxylation of glycerol and polyols.

ten Dam J, Hanefeld U - ChemSusChem (2011)

Homolytic cleavage of hydrogen on platinum and subsequent spillover.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3277901&req=5

fig02: Homolytic cleavage of hydrogen on platinum and subsequent spillover.
Mentions: Qin et al. also used Pt/WO3/ZrO2 as a catalyst. Using a fixed-bed reactor they were able to obtain both high conversion (70 %) and good 13PD selectivity (46 %) using aqueous glycerol at only 403 K (Table 2, entry 19).[54] The authors ascribe the low reaction temperature to the ability of the catalyst to activate hydrogen as proton and hydride. First, hydrogen is homolytically split into hydrogen atoms (1, Figure 2), which can spillover onto the WO3/ZrO2 surface (2, Figure 2). Here the hydrogen atom can donate an electron to a Lewis acidic site, generating a proton (3, Figure 2). This proton can be transferred to the substrate alcohol and a second hydrogen atom, acting as an acid, combines with the electron to form a hydride (4, Figure 2), stabilized on the Lewis acid site. This hydride is then finally used as a reductant.[62, 63] This hypothesis is supported by NH3 chemisorption measurements using supports that were calcined at different temperatures. Increasing the calcination temperature leads to higher acidity, resulting in higher conversion.[54]

Bottom Line: This new chemical toolbox needs to be designed to guarantee the demands of future generations at a reasonable price.The surplus of functionality in sugars and glycerol consists of alcohol groups.To yield suitable renewable chemicals these natural products need to be defunctionalized by means of dehydroxylation.

View Article: PubMed Central - PubMed

Affiliation: Gebouw voor Scheikunde, Afdeling Biotechnologie, Technische Universiteit Delft, Julianalaan 136, 2628 BL Delft, The Netherlands.

Show MeSH