Letter pubs.acs.org/journal/ascecg
One-Pot Transformation of Levulinic Acid to 2‑Methyltetrahydrofuran Catalyzed by Pt−Mo/H‑β in Water Tomoo Mizugaki,† Keito Togo,† Zen Maeno,† Takato Mitsudome,† Koichiro Jitsukawa,† and Kiyotomi Kaneda*,†,‡ †
Department of Materials Engineering Science, Graduate School of Engineering Science, Osaka University, 1-3 Machikaneyama, Toyonaka, Osaka 560-8531, Japan ‡ Research Center for Solar Energy Chemistry, Osaka University, 1-3 Machikaneyama, Toyonaka, Osaka 560-8531, Japan S Supporting Information *
ABSTRACT: One-pot transformation of levulinic acid to 2methyltetrahydrofuran is facilely promoted by a H-β-zeolitesupported Pt−Mo bimetallic catalyst in water without any additives. The Pt−Mo species efficiently promotes hydrogenation of levulinic acid to 1,4-pentanediol, which is subsequently dehydrated to form 2-methyltetrahydrofuran by H-β zeolite in the aqueous phase. The Pt−Mo/H-β catalyst is recoverable and reusable while retaining its high activity and selectivity.
KEYWORDS: Levulinic acid, 2-Methyltetrahydrofuran, Pt−Mo bimetallic catalyst, H-β zeolite, One-pot transformation
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INTRODUCTION The development of simple synthetic methods to produce value-added chemicals from biogenic compounds offers a significant solution to the problem of reducing CO2 emissions. Catalysts play a key role in the valorization of biomass-derived chemicals.1−3 Among a diversity of biomass derivatives, levulinic acid (LA), produced from lignocellulose, is a promising C5 platform chemical selected as one of 15 most valuable biogenic chemicals by the U.S. Department of Energy.4−6 Because of the increasing attention given to the diverse applications of LA, the development of efficient catalysts for transforming LA to levulinate esters,7,8 angelica lactones,9,10 γ-valerolactone (GVL)11−13 and 1,4-pentanediol (1,4-PeD)14−17 has been widely studied. Catalytic transformations of LA to 2-methyltetrahydrofuran (MTHF) are rare despite its usefulness as a green fuel additive18 and an ethereal solvent.19,20 Moreover, reported catalyst systems have disadvantages such as requirements for organic solvents,17,21−24 additives,14,17,22 severe reaction conditions such as high temperature and/or high H2 pressure,14,21,23,24 and tedious workup in order to separate the catalysts and prepare them for reuse.14,17,22 Therefore, the development of more efficient catalytic systems for the transformation of LA to MTHF would be advantageous. We recently reported the use of a platinum−molybdenum bimetallic catalyst for highly selective hydrogenation of LA to 1,4-PeD in water without the use of any additives.25 Inspired by this finding, we envisioned that immobilization of a platinum− © XXXX American Chemical Society
molybdenum bimetallic species on a solid acid would allow for a one-pot transformation of LA to MTHF via subsequent dehydrative cyclization of the intermediate 1,4-PeD catalyzed by the solid acid (eq 1). The success of this attempt overcomes several problems that the previous reports have faced (Table S1).
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RESULTS AND DISCUSSION A bimetallic Pt−Mo species supported on H-β zeolite (Pt− Mo/H-β) was prepared by a coimpregnation method. Other Pt−Mo catalysts were also prepared in a similar way using HZSM-5, H-USY, SiO2, SO42−/ZrO2, and SiO2−Al2O3 as solid acid supports (see the Supporting Information for the Received: January 26, 2016 Revised: February 20, 2016
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DOI: 10.1021/acssuschemeng.6b00181 ACS Sustainable Chem. Eng. XXXX, XXX, XXX−XXX
Letter
ACS Sustainable Chemistry & Engineering Table 1. Effects of Various Supports on the Formation of MTHF from LA Using Pt−Mo Catalystsa
yield [%]b entry
catalyst
conv. [%]b
MTHF
1,4-PeD
GVL
2-PeOH
1-PeOH
1 2 3 4c 5d 6 7 8 9 10 11e 12e,f
Pt−Mo/H-β Pt−Mo/H-β (reuse 1) Pt−Mo/H-β (reuse 2) Pt−Mo/H-β Pt−Mo/H-β Pt−Mo/H-ZSM-5 Pt−Mo/H-USY Pt−Mo/SiO2 Pt−Mo/SO42−/ZrO2 Pt−Mo/SiO2−Al2O3 Pt/H-β MoOx/H-β
>99 >99 >99 >99 >99 >99 >99 >99 >99 >99 >99
