Sucrose Is a Promising Feedstock for the Synthesis of the Platform Chemical Hydroxymethylfurfural

Efficient conversion of carbohydrates into 5-hydroxymethylfurfural using choline chloride-based deep eutectic solvents

In this study, the conversion of monosaccharides to 5-hydroxymethylfurfural (5-HMF) using different deep eutectic solvents (DESs) was investigated in various conditions. Among all the investigated DESs, [ChCl][trichloroacetic acid], based on choline chloride and trichloroacetic acid with the ratio 1:1, showed the highest catalytic activity. A maximum 5-HMF yield was 82 % for 1 h at 100 °C using [ChCl][trichloroacetic acid] as a catalyst from fructose. [ChCl][trichloroacetic acid] could be recovered and reused three times with a slight loss in activity. Our work demonstrated the low-cost and effective method for the synthesis of 5-HMF from carbohydrates.

Soluble and reusable polymer-based catalysts with Brønsted and Lewis acidity for the one-pot synthesis of hydroxymethylfurfural from glucose

One-pot synthesis of hydroxymethylfurfural from glucose using polymer-based catalysts with Brønsted and Lewis acidity.

Influence of Reaction Conditions on Hydrothermal Carbonization of Fructose

Hydrothermal carbonization is a powerful way to convert cellulosic waste into valuable platform chemicals and carbonaceous materials. In this study, to optimize the process, fructose was chosen as the carbon precursor and the influence of reaction time, acid catalysis, feed gas and pressure on the conversion products is evaluated. 5-hydroxymethylfurfural (HMF) is produced in high amounts in relatively short time. Both strong and weak acids accelerate fructose conversion. Levulinic acid (LevA) formation is faster than that of hydrothermal (HT) carbon in acidic conditions. Strong acid catalysts should be considered to target preferentially LevA production, whereas milder conditions should be preferred for HMF production. Moreover, a slight initial overpressure of the reactor is always beneficial in terms of conversion. FT-IR and ¹³ C ss-NMR spectroscopy and SEM showed that HT carbon evolves through time from a furanic-based structure with alkylic linkers to an increasingly cross-linked condensed structure. MALDI-ToF mass spectrometry showed the existence of a series of oligomers in a mass range within 650 Da and 1500 Da formed by condensation of repeating units.

Reaction Mechanism of the Microwave-Assisted Synthesis of 5-Hydroxymethylfurfural from Sucrose in Sugar Beet Molasses

5-hydroxymethylfurfural (HMF) stands out among the chemical products derived from biomass as a building block in the chemical industry. The conventional production of HMF is usually carried out from fructose, glucose, or other monosaccharides as feedstock, but sugar beet molasses, a by-product of the sugar industry containing sucrose (45–55%), is promising. This exploratory study used three aqueous stock solutions and one biphasic system as the sources of sucrose. The dehydration of sucrose to 5-hydroxymethylfurfural was assisted by microwave heating and subcritical water conditions. The maximum yield of HMF was 27.8 mol % for the aqueous solution of synthetic sucrose at 80 min of treatment. Although HMF yield was 7.1 mol % in the aqueous sugar beet molasses solution, it increased 2-fold after clarification (15.1 mol %) and 1.6-fold in the biphasic system (11.4 mol %). These are favorable outcomes since this is an exploratory investigation. The pseudo-first-order model fitted experimental data from the conversion of the sucrose from the stock solutions, and kinetic parameters were estimated and compared. The estimated reaction rate constant showed that inversion of sucrose is faster than fructose dehydration to HMF, but the latter reaction was the rate-determining step only for the biphasic system. The maximum partition coefficient value was four between 40 min and 60 min of reaction, calculated at room temperature. These predictions help investigators to estimate conversions and selectivity when pilot plants need to be simulated.

Cascade Membrane System for Separation of Water and Organics from Liquid By-Products of HTC of the Agricultural Digestate—Evaluation of Performance

New regulations aimed at curbing the problem of eutrophication introduce limitations for traditional ways to use the by-product of anaerobic digestion—the digestate. Hydrothermal carbonisation (HTC) can be a viable way to valorise the digestate in an energy-efficient manner and at the same time maximise the synergy in terms of recovery of water, nutrients, followed by more efficient use of the remaining carbon. Additionally, hydrothermal treatment is a feasible way to recirculate recalcitrant process residues. Recirculation to anaerobic digestion enables recovery of a significant part of chemical energy lost in HTC by organics dissolved in the liquid effluent. Recirculating back to the HTC process can enhance nutrient recovery by making process water more acidic. However, such an effect of synergy can be exploited to its full extent only when viable separation techniques are applied to separate organic by-products of HTC and water. The results presented in this study show that using cascade membrane systems (microfiltration (MF) → ultrafiltration (UF) → nanofiltration (NF)), using polymeric membranes, can facilitate such separation. The best results were obtained by conducting sequential treatment of the liquid by-product of HTC in the following membrane sequence: MF 0.2 µm → UF PES 10 → NF NPO30P, which allowed reaching COD removal efficiency of almost 60%.

Catalytic Conversion of Xylose to Furfural by p-Toluenesulfonic Acid (pTSA) and Chlorides: Process Optimization and Kinetic Modeling

Furfural is one of the most promising precursor chemicals with an extended range of downstream derivatives. In this work, conversion of xylose to produce furfural was performed by employing p-toluenesulfonic acid (pTSA) as a catalyst in DMSO medium at moderate temperature and atmospheric pressure. The production process was optimized based on kinetic modeling of xylose conversion to furfural alongwith simultaneous formation of humin from xylose and furfural. The synergetic effects of organic acids and Lewis acids were investigated. Results showed that the catalyst pTSA-CrCl₃·6H₂O was a promising combined catalyst due to the high furfural yield (53.10%) at a moderate temperature of 120 °C. Observed kinetic modeling illustrated that the condensation of furfural in the DMSO solvent medium actually could be neglected. The established model was found to be satisfactory and could be well applied for process simulation and optimization with adequate accuracy. The estimated values of activation energies for xylose dehydration, condensation of xylose, and furfural to humin were 81.80, 66.50, and 93.02 kJ/mol, respectively.

Seagrass-based platform strategies for sustainable hydroxymethylfurfural (HMF) production: toward bio-based chemical products

Today, sustainable chemistry is a key trend in the chemical manufacturing industry due mainly to concerns over the global environment and resource security. In sustainable chemical manufacture, the choice of a bio-based feedstock plays a pivotal pillar. In terms of feedstock utilization for producing HMF, which is a multivalent platform intermediate easily convertible to valuable chemical products; biopolymers, biofuels, and other important chemicals, seagrass biomasses can be more favorable feedstocks compared with land plant resources due primarily to easy availability and no systematic farming. Moreover, seagrass feedstocks could contribute cost-effectively and sustainably producing HMF by exploiting the beach-cast seagrasses on seagrass-prairies with no feedstock cost, indicating that seagrass biomasses could be a most promising biofeedstock source for sustainable HMF production. We afford a platform bioprocessing technology that has not been attempted before for sustainable HMF production using raw seagrass biomass. This bioprocess can be operated by simple reaction conditions using inorganic Brønsted acids (mainly HCl) and ionic liquid solvents at relatively low temperatures (120-130 °C). In addition, some bioengineering strategies for improving the growth of seagrass biomass and the quantity/quality of nonstructural carbohydrates (starch, sucrose) that can be used as the feeding substrates for HMF production are also discussed. The main aim of this review is to provide some important information about breakthrough bio/technologies conducive to cost-effective and sustainable HMF production.

Structural Effects of Cellulose on Hydrolysis and Carbonization Behavior during Hydrothermal Treatment

This study aims to investigate how the morphology of cellulose influences the hydrolysis and carbonization during hydrothermal treatment at temperatures between 180 and 240 °C. The morphology of cellulose, especially different crystallinities and degrees of polymerization, is represented by microcrystalline cellulose and α-cellulose. Kinetic analysis is considered a tool to allow the determination of the mechanisms of the two types of cellulose during the hydrothermal process. A kinetic model, in which cellulose is assumed to be hydrolyzed to a limited extent, is proposed. Five scenarios are used as models for pyrolysis of nonhydrolyzed cellulose that forms primary char, along with reaction pathways of hydrolyzable cellulose and its derivatives that latterly form secondary char. The morphologies of solid products are in good agreement with the results of the proposed model.

Isomerization of Glucose to Fructose in Hydrolysates from Lignocellulosic Biomass Using Hydrotalcite

The isomerization of glucose-containing hydrolysates to fructose is a key step in the process from lignocellulosic biomass to the platform chemical hydroxymethylfurfural. We investigated the isomerization reaction of glucose to fructose in water catalyzed by hydrotalcite. Catalyst characterization was performed via IR, XRD, and SEM. Firstly, glucose solutions at pH-neutral conditions were converted under variation of the temperature, residence time, and catalyst loading, whereby a maximum of 25 wt.% fructose yield was obtained at a 38 wt.% glucose conversion. Secondly, isomerization was performed at pH = 2 using glucose solutions as well as glucose-containing hydrolysates from lignocellulosic biomass. Under acidic conditions, the hydrotalcite loses its activity for isomerization. Consequently, it is unavoidable to neutralize the acidic hydrolysate before the isomerization step with an inexpensive base. As a neutralizing agent NaOH is preferred over Ba(OH)2, since higher fructose yields are achieved with NaOH. Lastly, a pH-neutral hydrolysate from lignocellulose was subjected to isomerization, yielding 16 wt.% fructose at a 32 wt.% glucose conversion. This work targets the application of catalytic systems on real biomass-derived samples.

HTC of Wet Residues of the Brewing Process: Comprehensive Characterization of Produced Beer, Spent Grain and Valorized Residues

Steady consumption of beer results in a steady output of residues, i.e., brewer’s spent grain (BSG). Its valorization, using hydrothermal carbonization (HTC) seems sensible. However, a significant knowledge gap regarding the variability of this residue and its influence on the valorization process and its potential use in biorefineries exists. This study attempted to fill this gap by characterization of BSG in conjunction with the main product (beer), taking into accounts details of the brewing process. Moreover, different methods to assess the performance of HTC were investigated. Overall, the differences in terms of the fuel properties of both types of spent grain were much less stark, in comparison to the differences between the respective beers. The use of HTC as a pretreatment of BSG for subsequent use as a biorefinery feedstock can be considered beneficial. HTC was helpful in uniformization and improvement of the fuel properties. A significant decrease in the oxygen content and O/C ratio and improved grindability was achieved. The Weber method proved to be feasible for HTC productivity assessment for commercial installations, giving satisfactory results for most of the cases, contrary to traditional ash tracer method, which resulted in significant overestimations of the mass yield.

Exploiting the Feedstock Flexibility of the Emergent Synthetic Biology Chassis Vibrio natriegens for Engineered Natural Product Production

A recent goal of synthetic biology has been to identify new chassis that provide benefits lacking in model organisms. Vibrio natriegens is a marine Gram-negative bacterium which is an emergent synthetic biology chassis with inherent benefits: An extremely fast growth rate, genetic tractability, and the ability to grow on a variety of carbon sources ("feedstock flexibility"). Given these inherent benefits, we sought to determine its potential to heterologously produce natural products, and chose beta-carotene and violacein as test cases. For beta-carotene production, we expressed the beta-carotene biosynthetic pathway from the sister marine bacterium Vibrio campbellii, as well as the mevalonate biosynthetic pathway from the Gram-positive bacterium Lactobacillus acidophilus to improve precursor abundance. Violacein was produced by expressing a biosynthetic gene cluster derived from Chromobacterium violaceum. Not only was V. natriegens able to heterologously produce these compounds in rich media, illustrating its promise as a new chassis for small molecule drug production, but it also did so in minimal media using a variety of feedstocks. The ability for V. natriegens to produce natural products with multiple industrially-relevant feedstocks argues for continued investigations into the production of more complex natural products in this chassis.

Direct Catalytic Route to Biomass-Derived 2,5-Furandicarboxylic Acid and Its Use as Monomer in a Multicomponent Polymerization

Efficient synthesis of valuable platform chemicals from renewable feedstock is a challenging, yet essential strategy for developing technologies that are both economical and sustainable. In the present study, we investigated the synthesis of 2,5-furandicarboxylic acid (FDCA) in a two-step catalytic process starting from sucrose as largely available biomass feedstock. In the first step, 5-(hydroxymethyl)furfural (HMF) was synthesized by hydrolysis and dehydration of sucrose using sulfuric acid in a continuous reactor in 34% yield. In a second step, the resulting reaction solution was directly oxidized to FDCA without further purification over a Au/ZrO₂ catalyst with 84% yield (87% selectivity, batch process), corresponding to 29% overall yield with respect to sucrose. This two-step process could afford the production of pure FDCA after the respective extraction/crystallization despite the impure intermediate HMF solution. To demonstrate the direct application of the biomass-derived FDCA as monomer, the isolated product was used for Ugi-multicomponent polymerizations, establishing a new application possibility for FDCA. In the future, this efficient two-step process strategy toward FDCA should be extended to further renewable feedstock.

Influence of the pH Value on the Hydrothermal Degradation of Fructose

The hydrothermal treatment of sugars features a promising technology for the production of fine and platform chemicals from renewable resources. In this work the hydrothermal decomposition of fructose was studied in a buffered medium at a pH range between 2.2 and 8.0. It is demonstrated that at lower pH values mainly 5-hydroxymethylfurfural (HMF), levulinic acid and humin are generated, while lactic acid and acetic acid are produced at higher pH values. The work shows that the use of moderate acidic conditions may have advantages for the hydrothermal HMF production over the use of strongly acidic conditions, as especially the degradation into levulinic acid is suppressed. Besides, this study deals with a rather complex reaction network, hence limitations and need for adaption of the kinetic model are discussed.

Improvement of hydrogen production from Chlorella sp. biomass by acid-thermal pretreatment

BACKGROUND

Owing to the high growth rate, high protein and carbohydrate contents, and an ability to grow autotrophically, microalgal biomass is regarded as a promising feedstock for fermentative hydrogen production. However, the rigid cell wall of microalgae impedes efficient hydrolysis of the biomass, resulting in low availability of assimilable nutrients and, consequently, low hydrogen production. Therefore, pretreatment of the biomass is necessary in order to achieve higher hydrogen yield (HY). In the present study, acid-thermal pretreatment of Chlorella sp. biomass was investigated. Conditions for the pretreatment, as well as those for hydrogen production from the pretreated biomass, were optimized. Acid pretreatment was also conducted for comparison.

RESULTS

Under optimum conditions (0.75% (v/v) H2SO4, 160 °C, 30 min, and 40 g-biomass/L), acid-thermal pretreatment yielded 151.8 mg-reducing-sugar/g-biomass. This was around 15 times that obtained from the acid pretreatment under optimum conditions (4% (v/v) H2SO4, 150 min, and 40 g-biomass/L). Fermentation of the acid-thermal pretreated biomass gave 1,079 mL-H2/L, with a HY of 54.0 mL-H2/g-volatile-solids (VS), while only 394 mL/L and 26.3 mL-H2/g-VS were obtained from the acid-pretreated biomass.

CONCLUSIONS

Acid-thermal pretreatment was effective in solubilizing the biomass of Chlorella sp. Heat exerted synergistic effect with acid to release nutrients from the biomass. Satisfactory HY obtained with the acid-thermal pretreated biomass demonstrates that this pretreatment method was effective, and that it should be implemented to achieve high HY.

Dehydration of fructose, sucrose and inulin to 5-hydroxymethylfurfural over yeast-derived carbonaceous microspheres at low temperatures

This work prepared carbonaceous microspheres by hydrothermal carbonization of yeast cells followed by sulfonation with concentrated sulphuric acid (98%) at room temperature. The obtained carbonaceous product (CM-SO₃H) had a high acid density (1.80 mmol g⁻¹). We evaluated CM-SO₃H as a solid catalyst for the dehydration of fructose-based carbohydrates to 5-hydroxymethylfurfural (5-HMF) in the ionic liquid 1-butyl-3-methylimidazolium chloride ([BMIM][Cl]). The effects of the catalyst and substrate loadings as well as the reaction temperature and time on the yield of 5-HMF were investigated. Under the optimum conditions, a 5-HMF yield of up to 83.5% was obtained from fructose with a reaction temperature of 80 °C for 30 min. Furthermore, 44.8% and 59.2% 5-HMF yields were obtained from sucrose (80 °C for 30 min) and inulin (80 °C for 60 min), respectively. CM-SO₃H and [BMIM][Cl] showed high stability and could be recycled between five and eight times without significant loss of catalytic activity. More importantly, the catalytic system could be applied to high substrate concentrations. CM-SO₃H combined with [BMIM][Cl] is a promising system for transforming fructose-based carbohydrates into 5-HMF.

This work prepared carbonaceous microspheres by hydrothermal carbonization of yeast cells followed by sulfonation with concentrated sulphuric acid (98%) at room temperature.

Hydrothermal Carbonization Brewer’s Spent Grains with the Focus on Improving the Degradation of the Feedstock

Hydrochar is a very interesting product from agricultural and food production residues. Unfortunately, severe conditions for complete conversion of lignocellulosic biomass is necessary, especially compared to the conversion of sugar compounds. The goal of this work is to improve the conversion of internal carbohydrates by application of a two-steps process, by acid addition and slightly higher water content. A set of experiments at different temperatures (180, 200, and 220 °C), reaction times (2 and 4 h), and moisture contents (80% and 90%) was performed to characterize the solid (high heating value (HHV), elemental) and liquid product phase. Afterwards, acid addition for a catalyzed hydrolysis reaction during hydrothermal carbonization (HTC) and a two-steps reaction (180 and 220 °C) were tested. As expected, a higher temperature leads to higher C content of the hydrochar and a higher fixed carbon (FC) content. The same effect was found with the addition of acids at lower temperatures. In the two-steps reaction, a primary hydrolysis step increases the conversion of internal carbohydrates. Higher water content has no significant effect, except for increasing the solubility of ash components.

BioEnergy and BioChemicals Production from Biomass and Residual Resources

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