Optimization of Co/Mn/Br-Catalyzed Oxidation of 5-Hydroxymethylfurfural to Enhance 2,5-Furandicarboxylic Acid Yield and Minimize Substrate Burning

Abstract

2,5-furandicarboxylic acid (FDCA) is a valuable non-phthalate biomass-based plastic precursor with the potential to replace terephthalic acid (TPA) in a variety of polymer applications. In this work, the Co/Mn/Br catalyzed semi-continuous oxidation of 5hydroxymethylfurfural (HMF) to FDCA has been carried out at temperatures lower than those of the traditional Mid-Century (MC) process. As HMF is more susceptible to side reactions (e.g. the over-oxidation to CO and CO 2 ), lower temperatures compared to the MC process are typically used to prevent substrate burning. However, lower temperatures afford much decreased FDCA yield compared to that of TPA in p-xylene oxidation. Therefore, optimization of other operating variables such as catalyst composition, water concentration in the acetic acid solvent and pressure are essential to maximize FDCA yield. Using such optimization, we show that the FDCA yield can be enhanced to 90% at 1/0.015/0.5 molar ratio of Co, Mn and Br, 7% (v/v) water, 30 bar (CO 2 /O 2 = 1/1, mol/mol) and 180 o C, the highest value reported for HMF oxidation using Co/Mn/Br catalyst. The use of Zr(IV) as co-catalyst facilitates FDCA formation, but only at lower temperatures (120-160 °C) where the FDCA yield is compromised. These findings broaden the scope of the application of the industrial MC catalytic process for FDCA production. use) by 65%. As a result, FDCA has been identified by DOE as one of the top twelve building blocks for the future green chemicals industry. 12, 13 The oxidation of HMF to FDCA was originally carried out in presence of strong oxidants, such as nitric acid or KMnO 4 . 2,14 Apart from environmental concerns, these systems produced only modest FDCA yield owing to substrate destruction under the harsh oxidizing conditions. Alternatively, oxidation with molecular oxygen, a much milder and cleaner oxidant, has been developed, employing noble metals such as platinum, 15-20 gold 21-27 and Pd 28-33 as active catalysts.During the past five years, these heterogeneous catalytic systems have been extensively studied and shown to provide nearly quantitative FDCA yield at relatively mild reaction temperatures (65-130 °C). However, because of its low solubility in the reaction medium, FDCA tends to precipitate out in the course of reaction, which might not only deactivate the catalysts by blocking the active sites but also causes separation problems. For this reason, sodium hydroxide is added in some cases to convert the diacid product into its sodium salt, which, after removal of the catalysts, must be treated with a strong acid for recovery of FDCA. 18,23,24 More recently, several base-free processes have been reported by using hydrotalcite-supported gold nanoparticles, 25 carbon nanotube-supported gold-palladium alloy nanoparticles 34 , covalent triazine supported ruthenium 35 and magnetic Fe 3 O 4 −CoO x 36 as catalysts. Nevertheless, even in these cases, the substrate (HMF) concentration needs to be maintained very low to avoid FDCA precipitation. The potential for practical appl...

Elektrokatalytische Oxidation von 5‐(Hydroxymethyl)furfural an Nickelborid mit großer Oberfläche

“…Die homogenkatalytische HMF‐Oxidation führt jedoch größtenteils nur zu geringen FDCA‐Ausbeuten und geringen Selektivitäten. Auch wenn optimierte, auf Metallbromiden basierende homogene Katalysatoren zu FDCA‐Ausbeuten von 90 % führen, bleibt ihre Abtrennung und Wiederverwertung eine Herausforderung . Demgegenüber stehen heterogene Katalysatoren, die einfacher von der Reaktionslösung abgetrennt werden können.…”

Electrocatalytic Oxidation of 5‐(Hydroxymethyl)furfural Using High‐Surface‐Area Nickel Boride

“…[6] However,homogeneous catalysis of HMF conversion often suffers from relatively low FDCA yields and poor selectivity.A n optimized metal bromide based homogenous catalyst developed already in 1958 provided FDCA yields of 90 %, but the separation of FDCA and catalyst recycling remain challenging. [7] On the other hand, heterogeneous catalysts can be separated from the reaction mixture more easily.T he high costs of the conventionally employed heterogeneous noblemetal catalysts,s uch as Pt, [8] Au, [9] Pd, [10] and Ru, [11] warrant efforts to replace them with transition-metal-based catalysts and to find alternative methods for HMF oxidation. In 1990, Grabowski and co-worker reported on the selective electrochemical oxidation of HMF to FDCA in NaOH (1.0 m)using aN i(OH) 2 electrode.H owever,t he yield was only 71 %.…”

Products of sugar beet processing as raw materials for chemicals and biodegradable polymers

“…The next step is the oxidation of HMF to FDCA. This requires suitable catalysts, such as supported noble metals 178,179 or bimetallic systems 180 deposited on carbon or metal oxides (such as aluminum, titanium or zirconium and others [181][182][183] ). The general concept of sugar-to-FDCA reactions seems fairly straightforward, but it should be noted that, besides the reactions which lead to the main product, there are a number of side reactions which greatly reduce the yield of the main process.…”