Efficient green methanol synthesis from glycerol

Journal name:
Nature Chemistry
Volume:
7,
Pages:
1028–1032
Year published:
DOI:
doi:10.1038/nchem.2345
Received
Accepted
Published online

Abstract

The production of biodiesel from the transesterification of plant-derived triglycerides with methanol has been commercialized extensively. Impure glycerol is obtained as a by-product at roughly one-tenth the mass of the biodiesel. Utilization of this crude glycerol is important in improving the viability of the overall process. Here we show that crude glycerol can be reacted with water over very simple basic or redox oxide catalysts to produce methanol in high yields, together with other useful chemicals, in a one-step low-pressure process. Our discovery opens up the possibility of recycling the crude glycerol produced during biodiesel manufacture. Furthermore, we show that molecules containing at least two hydroxyl groups can be converted into methanol, which demonstrates some aspects of the generality of this new chemistry.

At a glance

Figures

  1. Catalytic activity of the metal-oxide and mixed metal-oxide materials.
    Figure 1: Catalytic activity of the metal-oxide and mixed metal-oxide materials.

    ag, Space-time yield (STY) is defined as the grams of methanol produced per kilogram of catalyst per hour, and is presented as a function of the reaction temperature. The activity of the catalysts generally increases with increasing temperature. a, Over MgO, BET surface area 144 m2 g−1. b, Mg3CaOx, 25 m2 g−1. c, MgCaOx, 17 m2 g−1. d, MgCa3Ox, 11 m2 g−1. e, CaO, 13 m2 g−1. f, MgSr3Ox, 3 m2 g−1. g, SrO, 3 m2 g−1. The experiments were carried out in a stainless-steel fixed-bed flow reactor housed in a furnace for temperature control. Experiments were performed under the following conditions: catalyst (0.5 g), feed flow (1 ml h−1, 10 wt% glycerol/H2O), inert carrier (100 ml min−1), three hours. Full reaction data concerning the conversion and selectivity are given in Supplementary Table 1.

  2. Catalytic conversion of glycerol over cerium oxide and selectivity to methanol.
    Figure 2: Catalytic conversion of glycerol over cerium oxide and selectivity to methanol.

    a, Effect of temperature on the conversion (mol%) of glycerol (10 wt%) and methanol selectivity (mol%), which indicates that the space–time yield (STY) of methanol reaches a plateau with increasing temperature. Experimental conditions: 0.5 g catalyst, 100 ml min−1 inert carrier, 1 ml h−1 feed flow, products collected for three hours. b, Influence of contact time on glycerol conversion (mol%) and methanol selectivity (mol%) at 613 K suggests that the MeOH selectivity can improve with increased contact time. Experimental conditions: 100 ml min−1 inert carrier, 1 ml h−1 feed flow, products collected for three hours. Experimental error is ±5% as represented by the error bars.

  3. The influence of reaction temperature on the conversion and product selectivities (mol%) over MgO (A) with different feed concentrations of 1,3-propanediol.
    Figure 3: The influence of reaction temperature on the conversion and product selectivities (mol%) over MgO (A) with different feed concentrations of 1,3-propanediol.

    The formation of methanol requires a reactant with at least two hydroxyl groups as no products were detected with 1- or 2-propanol. Reaction conditions: 1 ml h−1 feed flow, 100 ml min−1 inert carrier, 0.25 g catalyst (0.5 g for 10 wt% feed) for three hours. ‘Others’ represents a combination of acrolein, propionaldehyde, allyl alcohol and 1-propanol in mol%. Experimental error is ±5% as represented by the error bars.

  4. Proposed mechanism for the formation of methanol from glycerol (1).
    Figure 4: Proposed mechanism for the formation of methanol from glycerol (1).

    Over base catalysts glycerol can undergo dehydration to form reactive species, which results in the production of methanol as the major product and of other secondary products, such as acrolein (2), 2,3-butanedione (8) and ethanol (9). Taut, enol–keto tautomerism.

  5. Catalytic activity of CeO2 increases the glycerol feed concentration for both pure and crude glycerol.
    Figure 5: Catalytic activity of CeO2 increases the glycerol feed concentration for both pure and crude glycerol.

    The pure glycerol solutions were prepared by diluting glycerol (99.9%) with water, whereas the crude glycerol solutions were prepared by diluting crude glycerol (about 85 wt% in water). The catalyst is tolerant of impurities in the feed stream in the case of the reactions with crude glycerol; however, over three hours the conversion is lower than that with the corresponding pure solutions. Glycerol conversion is represented by open symbols and methanol selectivity by half-filled symbols. Reaction conditions: 1.0 g ceria, 1 ml h−1 feed flow, 100 ml min−1 inert carrier, three hours duration at 613 K. Experimental error is ±5% as represented by error bars.

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Author information

  1. Present address: Sabic Technology & Innovation Center (STC), PO Box 42503, Riyadh 11551, Kingdom of Saudi Arabia

    • Muhammad H. Haider

Affiliations

  1. Cardiff Catalysis Institute, School of Chemistry. Cardiff University, Cardiff CF10 3AT, UK

    • Muhammad H. Haider,
    • Nicholas F. Dummer,
    • David W. Knight,
    • Robert L. Jenkins,
    • Jacob Moulijn,
    • Stuart H. Taylor &
    • Graham J. Hutchings
  2. Hull Research & Technology Centre, Saltend, Hull HU12 8DS, UK

    • Mark Howard

Contributions

M.H.H. prepared and tested the catalysts and designed the initial experiments, N.F.D designed the reactor and provided assistance with experimental design and D.W.K. provided mechanistic insights into the chemistry. Detailed analysis was provided by R.L.J. S.H.T provided expertise on catalyst preparation. G.J.H. directed the overall research and all the authors contributed to the analysis of the data and the writing of the manuscript.

Competing financial interests

The authors declare no competing financial interests.

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