Renewable Chemicals: Dehydroxylation of Glycerol and Polyols

Arundhathi RACHADepartment of Materials Engineering Science,

Graduate School of Engineering Science,Toyonaka, Osaka University- Osaka 560-8531,

Japan

OSAKA UNIVERSITYOSAKA UNIVERSITY

DOI 10.1002/cssc.201100162

Renewable Chemicals: Dehydroxylation of Glycerol and Polyols (Jeroen ten Dam and Ulf Hanefeld)

(ChemSusChem 2011,4,1017-1034; DOI 10.1002/cssc.201100162)

Renewable chemicals from natural resources e.g, sugars, cellulose and hemicellulose in a sustainable way.

Dehydroxylation, a fundamentally different approach of defunctioanlize of hydroxyl groups to yield renewable chemicals.

Defunctionalizing of biomass vs. functionalizing of oil

Design of catalysts that can selectively remove some of the functionalities .

Selective conversion of polyols, i.e dehydration and hydrogenation.

Selective dehydroxylation of Biomass

Six approaches for deoxgenation

1. Dehydration of vicinal diols and hydrogenation of carbonyl groups

2. Dehydration of alcohols and hydrogenation of carbon–carbon double bonds

3. Condensation of alcohols and hydrogenolysis of the resulting cyclic ethers

4. Hydrogenolysis of ethers

5. Ketonization of carboxylic acids

6. Hydrogenation of carboxylic acids

Selective dehydroxylation of polyols

Acid-catalyzed E1 mechanism

Base-catalyzed E2 mechanism

Hydrogenolysis

Sequential elimination (dehydration) and hydrogenation process.

Endothermic (dehydration) versus exothermic (hydrogenation) –product selectivity.

Need for design the catalyst which directs the overall process to occur via one specific dehydration pathway.

Dehydration -Hydrogenation

Dehydration selectivity determining the value-added chemicals from glycerol

Bronsted acid assist in eliminating secondary hydroxyl group

Lewis acid assist in eliminating primary hydroxyl group

Dehydration of alcohols and hydrogenation of carbon–carbon double bonds

Condensation of alcohols and hydrogenolysis of the resulting cyclic ethers

The reaction sequence is not applicable to glycerol, since the condensation of alcohols in order to form cyclic ethers is limited to five-membered (or larger) ring systems.

Glycerol to 1,2-propanediol

Under alkaline conditions, 12PD is being formed via glyceraldehyde

Under acidic conditions, acetol is generally is the key intermediate

!,2-propanediol from Glycerol

Glycerol to 1,3-propanediol

Selective production of 13PD is more challenging than 12PD

Active catalyst for 12PD production, selective catalyst for 13PD production

The factors that are important to influence 13PD formation are slowly being unraveled

Effect of impregnated metals and solvent on WO3/ZrO2

support for 13-PD selectivity

Protic solvent improves the reaction towards 13PD by facilitating proton transfer from solid acid to secondary alcohol by stabilizing a charged intermediate.

Additives improving the conversion and selctivity towards 13PD Pt/WO3/ZrO2 facilitates the homolytic cleavage of hydrogen on platinum and subsequent spillover

Pt/WO3/ZrO2

Pt/WO3/TiO2

Pt/WO3/TiO2/SiO2

Cu-STA/SiO2

Fixed bed reactor70% Conv.; 46% Selec.

403 K

7.5% Conv.; 44% Selec.

15% Conv.; 51% Selec.

70% Conv.; 46% Selec.

(Quin et al.)

(Gong et al.)

(Gong et al.)

(Huang et al.)

Tungsten additive for the improving Gly Conv and Selc towards 13PD

Rhenium additive for the improving Gly Conv. and Selc. towards 13PD

Rh/SiO2

Rh-ReOx/SiO2

Ir-ReOx/SiO2

Pt-Re/C

14.3% Conv.; 9.8% Selec.

79% Conv.; 14% Selec.

50% Conv.; 49% Selec.

20% Conv.; 34% Selec.

(Furikado et al.)

(Daniel et al.)

(Furikado et al.)

(Furikado et al.)

Pt-Re/C 45% Conv.; 29% Selec.

(Tomishige et al.)

Glycerol to acrolein

Glycerol to Lactic acid

Glycerol to Acrylonitrile

Glycerol to Epichlorohydrin

Glycerol to Ethylene glycol

Longer Chain polyols

5-Hydroxymethylfurfural (HMF formation form D-Glucose)

Conclusions

1. The smallest polyol Glycerol can be deoxygenated into a range of useful chemicals .

2. Major deoxygenation products from Glycerol are 12PD, 13PD and acrolein.

3. The catalyst for acrolein formation might be a good lead for new catalyst development for 13Pd, as both share the same intermediate.

4. The process can also be applied for long chain polyols for the production of important derivative like 5-HMF.

References:Please refer to Renewable chemicals: Dehydroxylation of Glycerol and Polyols Jeroen ten Dam and Ulf HanefeldChemSusChem 2011, 4, 1017-1034; DOI: 10.1002/cssc.201100162