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Selective hydrodeoxygenation of 2-furancarboxylic acid to valeric acid over molybdenum-oxide-modified platinum catalyst Takehiro Asano, Masazumi Tamura, Yoshinao Nakagawa, and Keiichi Tomishige ACS Sustainable Chem. Eng., Just Accepted Manuscript • DOI: 10.1021/ acssuschemeng.6b01640 • Publication Date (Web): 28 Sep 2016 Downloaded from http://pubs.acs.org on October 3, 2016
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Selective hydrodeoxygenation of 2-furancarboxylic acid to valeric acid over
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molybdenum-oxide-modified platinum catalyst
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Takehiro Asano [a] , Masazumi Tamura [a,b] , Yoshinao Nakagawa* [a,b ] , and Keiichi
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Tomishige* [a,b ]
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[a]Department of Applied Chemistry, School of Engineering, Tohoku University,
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6-6-07, Aoba, Aramaki, Aoba-ku, Sendai 980-8579, Japan
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[b] Research Center for Rare Metal and Green Innovation, Tohoku University, 468-1,
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Aoba, Aramaki, Aoba-ku, Sendai 980-0845, Japan
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*Corresponding authors: Yoshinao Nakagawa and Keiichi Tomishige
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Department of Applied Chemistry, School of Engineering, Tohoku University,
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6-6-07, Aoba, Aramaki, Aoba-ku, Sendai, 980-8579, Japan
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E-mail:
[email protected];
[email protected] 16
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Abstract
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2-Furancarboxylic acid (FCA), produced by oxidation of furfural, is rarely used as a
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platform molecule. Metal-oxide supported Pt-MoO x catalysts were effective for
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hydrodeoxygenation of FCA to valeric acid (VA) in water solvent. The highest VA
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yield is 51% over Pt-MoO x /TiO 2 catalyst under 1.5 MPa H 2 at 413 K. Other metal
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combinations (M-MoO x , M = Rh, Pd, Ru, Ir, Au, None; Pt-M’O x , M’= V, W, Re, None)
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showed
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hydrodeoxygenation of 2,5-furandicarboxylic acid (FDCA), and adipic acid (AA) was
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obtained with 21% yield at 473 K.
very
low
VA
yield.
This
catalyst
system
was
applicable
to
the
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Keywords: platinum, molybdenum,
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biomass
bimetallic catalyst,
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2-furancarboxylic acid,
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Utilization of biomass resources, especially inedible ones, has attracted more and
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more
attention
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5-hydroxymethylfurfural (HMF), which are produced from pentoses and hexoses,
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respectively, are well-known platform compounds in the conversion of biomass to
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useful fuels and chemicals.[2-9] There are number of reports for conversions of
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furfural
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condensation, oxidation, and so on.[10,11] Oxidation of furfural and HMF can produce
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2-furancarboxylic acid (FCA) and 2,5-furandicarboxylic acid (FDCA), respectively, in
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high yield.[12-16] Esters of FCA can be used as pharmaceutical raw materials, and
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FDCA has been regarded as a promising alternative to terephthalic acid.[17] However,
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the reports on the use of FCA or FDCA as a platform compound are very limited. T. R.
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Boussie, et al. reported in their patent that adipic acid can be produced from FDCA
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with two-step system using stoichiometric amount of reagent [18]: hydrogenation of
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furan-ring over Pd/SiO 2 catalyst, and hydrodeoxygenation with HI over Pd/SiO 2
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catalyst. Here, we propose a new catalytic conversion method of furan carboxylic
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acids: one-step catalytic hydrodeoxygenation of furan ring in FCA to valeric acid (VA).
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Esters of VA are used as perfumes, and their use as fuel has been also studied.[19]
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Although production of VA or VA esters from biomass-derived levulinic acid with
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excellent yield (90~99%) has been reported, there is no report on VA production from
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FCA, to the best of our knowledge.[20-24] In addition, the system of VA production
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from levulinic acid cannot be applied to other products such as adipic acid.
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Preliminary test of this system for production of adipic acid from FDCA is also
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included in this study.
and
in
view
of
carbon-neutral
concept.[1]
HMF, and the reactions include hydrogenation,
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Furfural
and
hydrogenolysis,
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We explored supported noble metal catalysts modified with group 5-7 metals for
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selective reduction of FCA since these catalysts, in particular, MoO x -modified noble
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metal catalysts,
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oxygenates.[25-31]
showed
excellent performance
for the
reduction
of various
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The results of the reduction of FCA over various catalysts are shown in Table 1. The
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molar ratio of the modifier to noble metal was set at 0.25. Pt-MoO x /TiO 2 catalyst gave
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the highest VA yield of 51% (entry 1). Other metal oxide-supported Pt-MoO x catalysts
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also gave some amount of VA; however, the yields were lower than that over
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Pt-MoO x /TiO 2 (entries 2-6). Carbon-supported Pt-MoO x catalysts showed very low
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yield
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tetrahydrofuran-2-carboxylic acid (THFCA), which is the ring-hydrogenated product,
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δ-valerolactone (DVL), 5-hydroxyvaleric acid (HVA), and 5-oxovaleric acid (OVA)
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(Scheme 1). Small amount of CO 2 was also formed probably via Pt-catalyzed aqueous
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phase reforming.[32-34] Hydrogenation products of the carboxyl group such as
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1-pentanol and 1,5-pentanediol were hardly observed. Carbon balance by FID-GC
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analysis was significantly lower than 100% in Pt-MoO x catalyst systems. On the other
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hand, analysis of total organic carbon (TOC) in the aqueous phase showed that larger
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amount of organic material remained in the aqueous phase (TOC: 90%; entry 1) than
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total amount of GC-detected compounds in liquid phase (80%). Some amounts of
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heavy water-soluble compounds are suggested to be formed.
of
VA
(entry
7).
The
main
byproducts
on
Pt-MoO x
catalysts
were
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In the cases of Rh-MoO x /TiO 2 and Pd-MoO x /TiO 2 , the main products were THFCA
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and 5-OVA, and VA was hardly observed (entries 8-9). This behavior agreed well with
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the previous reports on higher activity of Pd and Rh in furan-ring hydrogenation than 4
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that of Pt [35-38]. Ir-MoO x /TiO 2 , Ru-MoO x /TiO 2 , Au-MoO x /TiO 2 , and MoO x /TiO 2
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showed very low activity (entries 10-13). The catalytic activity of Pt/TiO 2 with other
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modifier than Mo was also much lower and only trace amount of VA was observed
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(entries 14-17). The physical mixture of Pt/TiO 2 and MoO x /TiO 2 showed no
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promotional effect on activity and selectivity to VA (entry 18). From these results, it is
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concluded that the combination of Pt and Mo on the same support is essential for the
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production of VA from FCA. The Pt-MoO x /TiO 2 catalysts with different Mo/Pt ratio
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were also tested (Table S1). Too much (Mo/Pt=1) or less (Mo/Pt=0.13) Mo addition
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decreased activity than Mo/Pt=0.25. At almost full conversion (over 90%), the catalyst
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with Mo/Pt=0.25 gave the highest VA yield and the lowest loss of carbon balance in
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Pt-MoO x /TiO 2 catalysts. Other byproduct yields were almost unchanged in the range of
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Mo/Pt ratio from 0.13 to 1.0.
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The time-course of hydrodeoxygenation of FCA over Pt-MoO x /TiO 2 (Mo/Pt=0.25)
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catalyst was shown in Figure 1 (detailed data are shown in Table S2). The formation of
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VA was clearly observed even at low conversion. The highest VA yield was 51%, which
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was obtained at 4 h. The formation amount of main byproducts such as THFCA, DVL,
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and 5-HVA was not large at all reaction times, and the amount increased gradually at
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longer reaction time, suggesting that VA was not formed via these byproducts. To
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confirm this, reduction of THFCA and DVL over Pt-MoO x /TiO 2 was conducted (Table
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S3). The reactivity of THFCA was much lower than FCA, and the reduction of THFCA
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gave only small amount of 1,5-pentanediol (4% yield) and DVL (1% yield). The main
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products in the DVL reduction were 1,5-pentandiol (20% yield) and 5-HVA (12%
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yield). An important point is that VA was hardly formed in both cases of THFCA and 5
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DVL, which supports the idea that THFCA and DVL are not intermediates of VA
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formation. These results indicate that the high reactivity of FCA is caused by the
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presence of furan-ring, and suggest that the C-O bonds dissociated before the
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hydrogenation of C=C bonds. Higher reactivity of furanic compounds than the
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corresponding tetrahydrofuran derivatives has been also reported for ring-opening
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reaction of furfural or furfuryl alcohol.[39-43] The effect of H 2 pressure was
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investigated (Tables S4). High H 2 pressure decreased VA yield and increased the yield
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of 1,5-difunctionalized products (DVL + 5-HVA + 5-OVA). The yields of THFCA, CO 2 ,
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and over-reduction products such as 1-pentanol were almost unchanged.
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Reusability of Pt-MoO x /TiO 2 (Mo/Pt= 0.25, 4 wt% Pt) catalyst was tested and the
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results are shown in Table S5. In order to avoid the effect of air exposure, the used
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catalyst was collected by decantation under N 2 and it was tested for the next run (Table
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S5, entry 2). The conversion decreased to 64% from 97%, and the catalyst deactivation
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was observed to some extent, even considering the 10% loss of the catalyst during the
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recovery process. One possible cause of the catalyst deactivation is the deposited
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carbonaceous species. Therefore, the catalyst was reused after the calcination (Table
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S5, entry 3). The conversion was 70%, and it was comparable to the case without air
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exposure, suggesting that the carbon deposition is not the main cause. In addition, the
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ICP-AES analysis of the reaction solution of the first run using the fresh catalyst
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indicates that leaching of Pt and Mo was negligible (
