Conversion of corn stalk into furfural using a novel heterogeneous strong acid catalyst in γ-valerolactone

Exploitation of lignocellulosic-based biomass biorefinery: A critical review of renewable bioresource, sustainability and economic views

Urbanization has driven the demand for fossil fuels, however, the overly exploited resource has caused severe damage on environmental pollution. Biorefining using abundant lignocellulosic biomass is an emerging strategy to replace traditional fossil fuels. Value-added lignin biomass reduces the waste pollution in the environment and provides a green path of conversion to obtain renewable resources. The technology is designed to produce biofuels, biomaterials and value-added products from lignocellulosic biomass. In the biorefinery process, the pretreatment step is required to reduce the recalcitrant structure of lignocellulose biomass and improve the enzymatic digestion. There is still a gap in the full and deep understanding of the biorefinery process including the pretreatment process, thus it is necessary to provide optimized and adapted biorefinery solutions to cope with the conversion process in different biorefineries to further provide efficiency in industrial applications. Current research progress on value-added applications of lignocellulosic biomass still stagnates at the biofuel phase, and there is a lack of comprehensive discussion of emerging potential applications. This review article explores the advantages, disadvantages and properties of pretreatment methods including physical, chemical, physico-chemical and biological pretreatment methods. Value-added bioproducts produced from lignocellulosic biomass were comprehensively evaluated in terms of encompassing biochemical products , cosmetics, pharmaceuticals, potent functional materials from cellulose and lignin, waste management alternatives, multifunctional carbon materials and eco-friendly products. This review article critically identifies research-related to sustainability of lignocellulosic biomass to promote the development of green chemistry and to facilitate the refinement of high-value, environmentally-friendly materials. In addition, to align commercialized practice of lignocellulosic biomass application towards the 21st century, this paper provides a comprehensive analysis of lignocellulosic biomass biorefining and the utilization of biorefinery green technologies is further analyzed as being considered sustainable, including having potential benefits in terms of environmental, economic and social impacts. This facilitates sustainability options for biorefinery processes by providing policy makers with intuitive evaluation and guidance.

Novel Challenges on the Catalytic Synthesis of 5-Hydroxymethylfurfural (HMF) from Real Feedstocks

The depletion of fossil resources makes the transition towards renewable ones more urgent. For this purpose, the synthesis of strategic platform-chemicals, such as 5-hydroxymethylfurfural (HMF), represents a fundamental challenge for the development of a feasible bio-refinery. HMF perfectly deals with this necessity, because it can be obtained from the hexose fraction of biomass. Thanks to its high reactivity, it can be exploited for the synthesis of renewable monomers, solvents, and bio-fuels. Sustainable HMF synthesis requires the use of waste biomasses, rather than model compounds such as monosaccharides or polysaccharides, making its production more economically advantageous from an industrial perspective. However, the production of HMF from real feedstocks generally suffers from scarce selectivity, due to their complex chemical composition and HMF instability. On this basis, different strategies have been adopted to maximize the HMF yield. Under this perspective, the properties of the catalytic system, as well as the choice of a suitable solvent and the addition of an eventual pretreatment of the biomass, represent key aspects of the optimization of HMF synthesis. On this basis, the present review summarizes and critically discusses the most recent and attractive strategies for HMF production from real feedstocks, focusing on the smartest catalytic systems and the overall sustainability of the adopted reaction conditions.

Towards efficient and greener processes for furfural production from biomass: A review of the recent trends

As mentioned in several recent reviews, biomass-based furfural is attracting increasing interest as a feasible alternative for the synthesis of a wide range of non-petroleum-derived compounds. However, the lack of environmentally friendly, cost-effective, and sustainable industrial procedures is still evident. This review describes the chemical and biological routes for furfural production. The mechanisms proposed for the chemical transformation of xylose to furfural are detailed, as are the current advances in the manufacture of furfural from biomass. The main goal is to overview the different ways of improving the furfural synthesis process. A pretreatment process, particularly chemical and physico-chemical, enhances the digestibility of biomass, leading to the production of >70 % of available sugars for the production of valuable products. The combination of heterogeneous (zeolite and polymeric solid) catalyst and biphasic solvent system (water/GVL and water/CPME) is regarded as an attractive approach, affording >75 % furfural yield for over 80 % of selectivity with the possibility of catalyst reuse. Microwave heating as an activation technique reduces reaction time at least tenfold, making the process more sustainable. The state of the art in industrial processes is also discussed. It shows that, when sulfuric acid is used, the furfural yields do not exceed 55 % for temperatures close to 180 °C. However, the MTC process recently achieved an 83 % yield by continuously removing furfural from the liquid phase. Finally, the CIMV process, using a formic acid/acetic acid mixture, has been developed. The economic aspects of furfural production are then addressed. Future research will be needed to investigate scaling-up and biological techniques that produce acceptable yields and productivities to become commercially viable and competitive in furfural production from biomass.

Recent progress in direct production of furfural from lignocellulosic residues and hemicellulose

Furfural is a vital biomass-derived platform molecule, which can be used to synthesize a wide range of value-added chemicals. Furfural and its derivatives are promising alternatives to conventional petroleum chemicals. However, recent industrial production of furfural existed some thorny problems, including low efficiency, energy waste, and environmental pollution. Therefore, tremendous and continuous efforts have been made by researchers to develop novel furfural production processes with high economic viability, production efficiency, and sustainability. This review summarized the merits and shortcomings of disparate catalytic systems for the synthesis of furfural from biomass and biomass pretreatment hydrolysate on the basis of recently published literature. Furthermore, the suggestions for furfural production research were put forward.

Highly efficient conversion of sunflower stalk-hydrolysate to furfural by sunflower stalk residue-derived carbonaceous solid acid in deep eutectic solvent/organic solvent system

Sunflower stalk was utilized as a source of raw material and catalyst for furfural production, and efficient conversion of xylose-rich hydrolysate into furfural was developed in an aqueous deep eutectic solvent/organic solvent medium by carbonaceous solid acid catalyst SO₄^2-/SnO₂-SSXR. The structural characteristics of SO₄^2-/SnO₂-SSXR was characterized by Brunauer-Emmett-Teller (BET), Scanning Electron Microscopy (SEM), Fourier-transform Infrared Spectroscopy (FT-IR), X-ray Diffraction (XRD), Pyridine Adsorption Fourier-transform Infrared (Py-IR) and Raman. Under the optimum catalytic conditions, furfural (110.1 mM) yield reached 82.6% in a ChCl-MAA/toluene medium at 180 °C in 15 min by 3.6 wt% SO₄^2-/SnO₂-SSXR. Additionally, quite importantly, SO₄^2-/SnO₂-SSXR, ChCl-MAA and toluene had good recyclability for furfural production. The potential catalytic path of xylose dehydration into furfural was proposed by co-catalysis with SO₄^2-/SnO₂-SSXR and ChCl-MAA. This study revealed high potential sustainable application of furfural production.

Facile preparation protocol of magnetic mesoporous carbon acid catalysts via soft-template self-assembly method and their applications in conversion of xylose into furfural

Furfural is a valuable dehydration product of xylose. It has a broad spectrum of industrial applications. Various catalysts containing SO₃H have been reported for the conversion of xylose into furfural. Nevertheless, the multi-step preparation is tedious, and the catalysts are usually fine powders that are difficult to separate from the suspension. Novel magnetic mesoporous carbonaceous materials (Fe/MC) were successfully prepared via facile self-assembly in a single step. A facile subsequent hydrothermal sulfonation of Fe/MC with concentrated H₂SO₄ at 180°C gave mesoporous carbon bearing SO₃H groups (SO₃H@Fe/MC) without loss of the magnetic properties. Various techniques were employed to characterize the SO₃H@Fe/MC as a candidate catalyst. It showed strong magnetism due to its Fe particles and possessed a 243 m² g^-1 BET-specific surface area and a 90% mesopore volume. The sample contained 0.21 mmol g^-1 of SO₃H and gave a high conversion and an acceptable furfural yield and selectivity (100%, 45% and 45%, respectively) when used at 170°C for 1 h with γ-valerolactone as solvent. The catalyst was easily separated after the catalytic tests by using a magnet, confirming sufficient magneticstability. This article is part of the theme issue 'Bio-derived and bioinspired sustainable advanced materials for emerging technologies (part 2)'.

Synthesis of sulfonated lignin-derived ordered mesoporous carbon for catalytic production of furfural from xylose

Sulfonated lignin-derived ordered mesoporous carbon (OMC-SO₃H) solid acid was synthesized through solvent evaporation induced self-assembly (EISA) method followed by sulfonation, using lignin as carbon precursor and glyoxal as cross-linking agent during the preparation process. The as-synthesized OMC-SO₃H exhibited a typical 2D hexagonal meso-structure (space group p6mm) and showed a good catalytic performance for the catalytic conversion of hemicellulose-derived xylose to furfural. A highest furfural yield of 76.7% with 100% xylose conversion was achieved at 200 °C for 45 min in γ-valerolactone (GVL)-water (85:15 v/v%) mixture. The lignin-derived OMC-SO₃H solid acid catalyst showed superior stability and reusability, and was also applicable to the catalytic production of furfural from xylan. This work provides a promising strategy for the synthesis of ordered mesoporous carbon solid acid from green and sustainable lignin biomass resource, which has wide range of applications in the utilization of cellulose and hemicellulose.

Production of furfural from xylose catalyzed by a novel calcium gluconate derived carbon solid acid in 1,4-dioxane

A novel carbon-based solid acid catalyst (SC-GCa-800) was prepared by the high-temperature carbonization of calcium gluconate followed by sulfonation with 4-diazoniobenzenesulfonate at room temperature.

Total utilization of lignin and carbohydrates in Eucalyptus grandis: an integrated biorefinery strategy towards phenolics, levulinic acid, and furfural

BACKGROUND

Lignocellulosic biomass, which is composed of cellulose, hemicellulose and lignin, represents the most abundant renewable carbon source with significant potential for the production of sustainable chemicals and fuels. Current biorefineries focus on cellulose and hemicellulose valorization, whereas lignin is treated as a waste product and is burned to supply energy to the biorefineries. The depolymerization of lignin into well-defined mono-aromatic chemicals suitable for downstream processing is recognized increasingly as an important starting point for lignin valorization. In this study, conversion of all three components of Eucalyptus grandis into the corresponding monomeric chemicals was investigated using solid and acidic catalyst in sequence.

RESULTS

Lignin was depolymerized into well-defined monomeric phenols in the first step using a Pd/C catalyst. The maximum phenolic monomers yield of 49.8 wt% was achieved at 240 °C for 4 h under 30 atm H₂. In the monomers, 4-propanol guaiacol (12.9 wt%) and 4-propanol syringol (31.9 wt%) were identified as the two major phenolic products with 90% selectivity. High retention of cellulose and hemicellulose pulp was also obtained, which was treated with FeCl₃ catalyst to attain 5-hydroxymethylfurfural, levulinic acid and furfural simultaneously. The optimal reaction condition for the co-conversion of hemicellulose and cellulose was established as 190 °C and 100 min, from which furfural and levulinic acid were obtained in 55.9% and 73.6% yields, respectively. Ultimately, 54% of Eucalyptus sawdust can be converted into well-defined chemicals under such an integrated biorefinery method.

CONCLUSIONS

A two-step process (reductive catalytic fractionation followed by FeCl₃ catalysis) allows the fractionation of all the three biopolymers (cellulose, hemicellulose, and lignin) in Eucalyptus biomass, which provides a promising strategy to make high-value chemicals from sustainable biomass.

Composite coal fly ash solid acid catalyst in synergy with chloride for biphasic preparation of furfural from corn stover hydrolysate

A solid acid catalyst SO₄^2-/SnO₂-Al₂O₃-CFA was synthesized based on industrial waste coal fly ash (CFA) as carrier and applied in the conversion of oxalic acid pretreated corn stover hydrolysate to produce furfural. Physical properties of the solid acid catalyst were characterized by SEM, FTIR, XRD, BET, EDAX, and NH₃-TPD. Highly wrinkled structure of SO₄^2-/SnO₂-Al₂O₃-CFA could provide more specific surface area for the covalent linkage between SiO₂ and SnO₂. Factors influencing the efficacy of SO₄^2-/SnO₂-Al₂O₃-CFA were systematically explored. The highest furfural yield of 84.7% was reached in NH₄Cl-toluene biphasic system at 180 °C for 30 min. The recyclability of SO₄^2-/SnO₂-Al₂O₃-CFA and toluene could be achieved for five batches with stable performance in transformation of xylose-rich corn stover hydrolysate. This study provided a novel solid acid catalyst with promising potential in the synthesis of furfural from corn stover.

Impact of total carbon/sulfate on methane production and sulfate removal from co-digestion of sulfate-containing wastewater and corn stalk

During the process of preparing furfural by straw depolymerization with dilute sulfuric acid, large amounts of high temperature sulfate-rich organic wastewater were produced. It cannot be treated directly by anaerobic digestion and converted to bioenergy due to high concentrations of sulfate. In this study, anaerobic co-digestion of sulfate containing wastewater and corn stalk was performed at thermophilic conditions to investigate the influences of total carbon (TC)/sulfate (6, 16, 35 and 110) on methane production and sulfate removal. The results showed that the highest methane production of 260.14 mL g^-1 volatile solid (VS) was achieved at TC/sulfate of 35, which was significantly higher than 12.53 mL g^-1 VS obtained at TC/sulfate of 6. Moreover, the results of sulfate balance analysis showed a maximum sulfate removal of 93.43% was achieved at TC/sulfate of 16, and sulfate concentration in biogas slurry was less than 0.1 g/L regardless of TC/sulfate after 28 days of co-digestion. The microbial community was analyzed using 16S rDNA sequencing technology, the results showed that methane was mainly produced by Methanoculleus and Methanosarcina, and sulfate was removed via Desulfotomaculum, and the relative abundance of methanogenic archaea (MA) and sulfate reducing bacteria (SRB) were significantly correlated with methane production and sulfate removal. It can concluded that higher methane production and sulfate removal can be obtained by anaerobic co-digestion of sulfate containing wastewater and corn stalk at properly TC/sulfate.

One-pot co-catalysis of corncob with dilute hydrochloric acid and tin-based solid acid for the enhancement of furfural production

A newly synthesized solid acid catalyst SO₄^2-/SnO₂-diatomite was prepared for synthesizing furfural from corncob in the presence of homogeneous Brönsted acid. The relationship between pKa of Brönsted acid and turnover frequency (TOF) of co-catalysis with Brönsted acid plus SO₄^2-/SnO₂-diatomite was explored on the conversion of corncob to furfural. HCl (pKa = -7.0) (0.5 wt%) plus SO₄^2-/SnO₂-diatomite (3.6 wt%) gave the highest furfural yield (40.1%) with TOF value at 2.98 h^-1 in the aqueous media. In the γ-valerolactone-water (6:4, v:v) biphasic media containing 15 g/L ZnCl₂, one-pot conversion of corncob with co-catalysts gave a furfural yield of 68.9% at 170 °C for 30 min. Additionally, an efficient SO₄^2-/SnO₂-diatomite recycling was achieved with a productivity of 15.6 g furfural/(g solid acid·day) after 5 cycles of repeated use. Clearly, this one-pot co-catalysis process has high potential application for furfural production in future.

Efficient transformation of corn stover to furfural using p-hydroxybenzenesulfonic acid-formaldehyde resin solid acid

In this work, p-hydroxybenzenesulfonic acid-formaldehyde resin acid catalyst (MSPFR), was synthesized by a hydrothermal method, and employed for the furfural production from raw corn stover. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), N₂ adsorption-desorption, elemental analysis (EA), thermogravimetric analysis (TGA), and Fourier transform infrared spectroscopy (FT-IR) were used to characterize the MSPFR. The effects of reaction time, temperature, solvents and corn stover loading were investigated. The MSPFR presented high catalytic activity for the formation of furfural from corn stover. When the MSPFR/corn stover mass loading ratio was 0.5, a higher furfural yield of 43.4% could be achieved at 190 °C in 100 min with 30.7% 5-hydroxymethylfurfural (HMF) yield. Additionally, quite importantly, the recyclability of the MSPFR for xylose dehydration is good, and for the conversion of corn stover was reasonable.

5-Hydroxymethylfurfural (HMF) Production from Real Biomasses

The present paper reviews recent advances on the direct synthesis of 5-hydroxymethylfurfural (HMF) from different kinds of raw biomasses. In particular, in the paper HMF production from: (i) edible biomasses; (ii) non-edible lignocellulosic biomasses; (iii) food wastes (FW) have been reviewed. The different processes and catalytic systems have been reviewed and their merits, demerits and requirements for commercialisation outlined.

Hydrolysis of Hemicellulose and Derivatives-A Review of Recent Advances in the Production of Furfural

Biobased production of furfural has been known for decades. Nevertheless, bioeconomy and circular economy concepts is much more recent and has motivated a regain of interest of dedicated research to improve production modes and expand potential uses. Accordingly, this review paper aims essentially at outlining recent breakthroughs obtained in the field of furfural production from sugars and polysaccharides feedstocks. The review discusses advances obtained in major production pathways recently explored splitting in the following categories: (i) non-catalytic routes like use of critical solvents or hot water pretreatment, (ii) use of various homogeneous catalysts like mineral or organic acids, metal salts or ionic liquids, (iii) feedstock dehydration making use of various solid acid catalysts; (iv) feedstock dehydration making use of supported catalysts, (v) other heterogeneous catalytic routes. The paper also briefly overviews current understanding of furfural chemical synthesis and its underpinning mechanism as well as safety issues pertaining to the substance. Eventually, some remaining research topics are put in perspective for further optimization of biobased furfural production.

Enhanced furfural production from raw corn stover employing a novel heterogeneous acid catalyst

With the aim to enhance the direct conversion of raw corn stover into furfural, a promising approach was proposed employing a novel heterogeneous strong acid catalyst (SC-CaC_t-700) in different solvents. The novel catalyst was characterized by elemental analysis, N₂ adsorption-desorption, FT-IR, XPS, TEM and SEM. The developed catalytic system demonstrated superior efficacy for furfural production from raw corn stover. The effects of reaction temperature, residence time, catalyst loading, substrate concentration and solvent were investigated and optimized. 93% furfural yield was obtained from 150mg corn stover at 200°C in 100min using 45mg catalyst in γ-valerolactone (GVL). In comparison, 51.5% furfural yield was achieved in aqueous media under the same conditions (200°C, 5h, and 45mg catalyst), which is of great industrial interest. Furfural was obtained from both hemicelluloses and cellulose in corn stover, which demonstrated a promising routine to make the full use of biomass.

Catalytic conversion of corncob and corncob pretreatment hydrolysate to furfural in a biphasic system with addition of sodium chloride

Catalytic conversion of corncob pretreatment hydrolysate and raw corncob into furfural in a modified biphasic system by SO₄^2-/SnO₂^- MMT solid catalyst has been developed. The influence of the organic solvent type, organic to water phase ratio, sodium chloride concentration, reaction temperature and time on the furfural production were comparatively evaluated. The results showed that furfural yields of 81.7% and 66.1% were achieved at 190°C for 15mins and 190°C for 20mins, respectively, for corncob pretreatment hydrolysate and raw corncob by this solid catalyst. The solid catalyst used in this study exhibited good stability and high efficiency applied in the modified biphasic system in addition to excellent recyclability. The proposed catalytic system displayed high performance for catalytic conversion of lignocellulosic biomass into important platform chemicals and has great potential in industrial application.

Dehydration of glucose to 5-hydroxymethylfurfural and 5-ethoxymethylfurfural by combining Lewis and Brønsted acid

In this work, glucose was transformed into 5-hydroxymethylfurfural (HMF) and 5-ethoxymethylfurfural (EMF) in the presence of AlCl₃·6H₂O and a Brønsted solid acid catalyst (PTSA–POM).

p-Hydroxybenzenesulfonic acid–formaldehyde solid acid resin for the conversion of fructose and glucose to 5-hydroxymethylfurfural

SPFR solid acids. Novel solid acid resins were synthesized by an energy and time efficient hydrothermal method.

Production of furfural from xylose and corn stover catalyzed by a novel porous carbon solid acid in γ-valerolactone

An efficient catalytic system using S-RFC as catalyst was developed to produce furfural from xylose and corn stover in GVL.

A ternary composite oxides S2O82−/ZrO2–TiO2–SiO2 as an efficient solid super acid catalyst for depolymerization of lignin

The solid, super, acid catalyst S₂O₈²⁻/ZrO₂–TiO₂–SiO₂, which has both a strong Brønsted acid and Lewis acid, was prepared and applied in lignin depolymerization.

Efficient catalytic system for the direct transformation of lignocellulosic biomass to furfural and 5-hydroxymethylfurfural

A feasible approach was developed for the co-production of 5-hydroxymethylfurfural (5-HMF) and furfural from corncob via a new porous polytriphenylamine-SO₃H (SPTPA) solid acid catalyst in lactone solvents. XRD, SEM, XPS, N₂ adsorption-desorption, elemental analysis, TG-DTA, acid-base titration and FTIR spectroscopy techniques were used to characterize the catalyst. This study demonstrates and optimizes the catalytic performance of SPTPA and solvent selection. SPTPA was found to exhibit superior catalytic ability in γ-valerolactone (GVL). Under the optimum reaction conditions, simultaneously encouraging yields of furfural (73.9%) and 5-HMF (32.3%) were achieved at 448K. The main advantages of this process include reasonable yields of both 5-HMF and furfural in the same reaction system, practical simplicity for the raw biomass utilization, and the use of a safe and environmentally benign solvent.

Catalytic conversion of xylose and corn stalk into furfural over carbon solid acid catalyst in γ-valerolactone

A novel carbon solid acid catalyst was synthesized by the sulfonation of carbonaceous material which was prepared by carbonization of sucrose using 4-BDS as a sulfonating agent. TEM, N2 adsorption-desorption, elemental analysis, XPS and FT-IR were used to characterize the catalyst. Then, the catalyst was applied for the conversion of xylose and corn stalk into furfural in GVL. The influence of the reaction time, temperature and dosage of catalyst on xylose dehydration were also investigated. The Brønsted acid catalyst exhibited high activity in the dehydration of xylose, with a high furfural yield of 78.5% at 170°C in 30min. What's more, a 60.6% furfural yield from corn stalk was achieved in 100min at 200°C. The recyclability of the sulfonated carbon catalyst was perfect, and it could be reused for 5times without the loss of furfural yields.

One-pot catalytic conversion of carbohydrates into furfural and 5-hydroxymethylfurfural

Recently, there has been growing interest in the transformation of renewable biomass into value-added chemicals and biofuels.