ISGC2, 21-24 Mail 2013, La Rochelle, France
Selective production of HMF from mono-, di- and poly-saccharides using solid acid catalysts Prasenjit Bhaumika, Paresh Laxmikant Dhepea a
Catalysis & Inorganic Chemistry Division, National Chemical Laboratory, Dr. Homi Bhabha Road, Pune, India E-mail:
[email protected]
In the green chemistry aspects, replacement of dwindling non-renewable fossil reserves with sustainable renewable resource, biomass is necessary to secure the society need of chemicals as well as to protect our environment from global warming. In US DOE report on “top value-added chemicals from biomass”, 5-hydroxymethyl furfural (HMF) has been described as one of the most important platform chemical1 which can be synthesized from variety of substrates such as fructose, glucose and their dimers and polymers. Heterogeneous catalysts provide a green synthetic pathway for HMF rather than homogeneous catalysts by catalyst recycling. Robust poly-saccharides are acid hydrolysed to yield glucose and glucose to fructose isomerization is known to be a base catalysed process. Further fructose dehydration to HMF is possible in the presence of acid. So the direct transformation of poly-saccharides to HMF is a complicated scheme and it is a challenge to develop a suitable catalyst.
Scheme: Production of HMF from mono-, di- and poly-saccharide.
Earlier it was shown that fructose to HMF reactions are carried out in biphasic system to improve the HMF yield and to suppress formation of formic acid and levulinic acid. So it is recommended that catalyst should be more hydrophilic as fructose is soluble in water. In the same time, catalyst should be hydrothermally stable. Considering this, synthesis of silicoaluminophosphate (SAPO) materials were undertaken as they were known to be more hydrothermally stable (ca. 600C in presence of 20% steam) and more hydrophilic in nature due to local electronegativity difference between framework Si, Al and P2 compared to HMOR which is a well-known catalyst for the fructose dehydration to HMF. In this work, three SAPO materials were synthesized viz. SAPO-44, SAPO-5 and SAPO-11 having varying surface area, pore size and total acid amount and subjected to reaction with fructose, glucose, maltose, cellobiose and starch separately. SAPO-44 is very active catalyst and can convert fructose selectively to 74% yield of HMF (Selectivity = 88%) within 1 h time. Yield of HMF is comparable to that in other reports but selectivity is more with SAPO-44 catalyst. Recycle study showed marginal decrease in the HMF yield upto 4 runs. Physico-chemical characterization of catalyst showed that slight morphology change occurs after reaction. Glucose conversion using SAPO-44 catalyst showed 64% HMF yield with 77% selectivity within 4 h. Dimer maltose and cellobiose also produced HMF selectively (ca. 52% yield) within 4 h and 6 h respectively. Direct conversion of starch was done using SAPO-44, produced 65% of HMF yield. Table: HMF production from mono-, di- and poly-saccharide. Reaction Time (h) Substrate Fructose Yield (%) Glucose Yield (%) 1 Fructose 6 4 Glucose 14 4 Maltose 5 5 6 Cellobiose 3 4 6 Starch 8 11 Reaction condition: substrate (10 wt%), 175C, water + MIBK = 1:5 (v/v).
HMF Yield (%) 74 64 53 50 65
An important platform chemical, HMF was produced selectively in high yield from variety of renewable feedstocks. Optimization of reaction condition was done by changing several parameters. SAPO catalyst can be reused minimum upto 4 recycle run with slight decrease in activity (74±12%). Catalyst structure-activity correlation will be discussed during presentation.
References 1. T. Werpy, G. Petersen, Top Value-Added Chemicals from Biomass, US Department of Energy, Oak Ridge, USA 2004. 2. B. M. Lok, C. A. Messina, R. L. Patton, R. T. Gajek, T. R. CaPnnan, E. M. Flanigen, Journal of American Chemical Society 1984, 106, 6092.
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