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14 pages, 2119 KiB

Open AccessArticle

Hydrodynamic Cavitation-Assisted Photo-Fenton Pretreatment and Yeast Co-Culture as Strategies to Produce Ethanol and Xylitol from Sugarcane Bagasse

by Carina Aline Prado, Ana Júlia E. B. da Silva, Paulo A. F. H. P. Fernandes, Vinicius P. Shibukawa, Fanny M. Jofre, Bruna G. Rodrigues, Silvio Silvério da Silva, Solange I. Mussatto and Júlio César Santos

Catalysts 2025, 15(5), 418; https://doi.org/10.3390/catal15050418 - 24 Apr 2025

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Abstract

This study explored innovative approaches to produce ethanol and xylitol from sugarcane bagasse using a hydrodynamic cavitation-assisted photo-Fenton process as the pretreatment, and yeast co-culture for hydrolysate fermentation. Pretreatment conditions were optimized (20 mg/L of iron sulfate, pH 5.0, and reaction time of [...] Read more.

This study explored innovative approaches to produce ethanol and xylitol from sugarcane bagasse using a hydrodynamic cavitation-assisted photo-Fenton process as the pretreatment, and yeast co-culture for hydrolysate fermentation. Pretreatment conditions were optimized (20 mg/L of iron sulfate, pH 5.0, and reaction time of 14 min) resulting in glucan and xylan hydrolysis yields of 96% and 89%, respectively. The hydrolysate produced under these conditions was fermented using a co-culture of Saccharomyces cerevisiae IR2 (an ethanol-producing strain) and Candida tropicalis UFMGBX12 (a xylitol-producing strain). Optimal co-culture conditions consisted of using an inoculum concentration of 1.5 g/L for each yeast strain. After 36 h of fermentation, ethanol and xylitol concentrations reached 20 g/L and 13 g/L, respectively. These results demonstrate the potential of combining hydrodynamic cavitation-assisted photo-Fenton pretreatment with co-culture fermentation to simultaneously produce ethanol and xylitol. This strategy presents a promising approach for enhancing the efficiency of lignocellulosic biorefineries. Full article

(This article belongs to the Special Issue Topical Advisory Panel Members' Collection Series: Biomass Catalytic Conversion)

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19 pages, 3763 KiB

Open AccessFeature PaperArticle

Synthesis of Nitrogen-Doped Biomass-Based Activated-Carbon-Supported Nickel Nanoparticles for Hydrazine Oxidation

by Virginija Ulevičienė, Aldona Balčiūnaitė, Daina Upskuvienė, Ance Plavniece, Aleksandrs Volperts, Galina Dobele, Aivars Zhurinsh, Gediminas Niaura, Loreta Tamašauskaitė-Tamašiūnaitė and Eugenijus Norkus

Catalysts 2025, 15(4), 400; https://doi.org/10.3390/catal15040400 - 19 Apr 2025

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Abstract

In this study we present an application of wood biomass—alder wood char—as the carbon precursor for the synthesis of novel and sustainable nitrogen-doped activated-carbon-supported nickel nanoparticle catalyst (AWC-Ni-N) for hydrazine oxidation. For comparison, the wood-based carbon material doped with nitrogen only (AWC-N) was [...] Read more.

In this study we present an application of wood biomass—alder wood char—as the carbon precursor for the synthesis of novel and sustainable nitrogen-doped activated-carbon-supported nickel nanoparticle catalyst (AWC-Ni-N) for hydrazine oxidation. For comparison, the wood-based carbon material doped with nitrogen only (AWC-N) was also synthesized. Extensive characterization, including SEM, Raman spectroscopy, XPS, and XRD revealed the catalysts’ microstructure and properties. Electrochemical testing demonstrated that the AWC-Ni-N catalyst significantly enhanced the efficiency of the hydrazine oxidation reaction. In addition, direct N₂H₄-H₂O₂ single-fuel-cell tests were conducted using the prepared AWC-N and AWC-Ni-N catalysts as the anodes and cathodes. Peak power densities of up to 10.8 mW cm⁻² were achieved at 25 °C, corresponding to a current density of 27 mA cm⁻² and a cell voltage of 0.4 V when the AWC-Ni-N catalyst was used as both the anode and cathode. Furthermore, the peak power density increased by approximately 1.6 and 2.9 times, respectively, when the operating temperature was raised from 25 °C to 55 °C for the AWC-N and AWC-Ni-N catalysts. Overall, the AWC-N and AWC-Ni-N catalysts demonstrated significant potential as anode and cathode materials in direct N₂H₄-H₂O₂ fuel cells. Full article

(This article belongs to the Special Issue Topical Advisory Panel Members' Collection Series: Biomass Catalytic Conversion)

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21 pages, 6034 KiB

Open AccessArticle

Silver-Modified Biochar: Investigating NO₂ Adsorption and Reduction Efficiency at Different Temperatures

by Flavia Tavares, Fernanda F. Camilo, Mohamed Zbair, Lionel Limousy and Jocelyne Brendle

Catalysts 2025, 15(4), 392; https://doi.org/10.3390/catal15040392 - 17 Apr 2025

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Abstract

This study investigates the adsorption and reduction of NO₂ on biochar (BCC) and silver-modified biochar (Ag-BCC) in a continuous flow. Ag-BCC showed a higher NO₂ adsorption capacity (11.78 mg/g) than BCC (11.04 mg/g) at 200 °C, despite its lower surface area [...] Read more.

This study investigates the adsorption and reduction of NO₂ on biochar (BCC) and silver-modified biochar (Ag-BCC) in a continuous flow. Ag-BCC showed a higher NO₂ adsorption capacity (11.78 mg/g) than BCC (11.04 mg/g) at 200 °C, despite its lower surface area (345 vs. 402 m²/g). While neither material decomposed NO₂ at 22 °C, Ag-BCC achieved a NO/NO₂ ratio of 20% (vs. 9% for BCC) at 200 °C, highlighting the catalytic role of silver in NO₂ conversion. Breakthrough curve modeling identified the Dose–Response model as optimal, accurately describing adsorption kinetics at all temperatures (22–200 °C). Adsorption rate constants decreased with increasing temperature, confirming exothermicity. Overall, the results highlight the enhanced performance of Ag-BCC for NO₂ capture and conversion, underlining the potential of surface-modified biochars in the sustainable mitigation of air pollution. Full article

(This article belongs to the Special Issue Topical Advisory Panel Members' Collection Series: Biomass Catalytic Conversion)

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20 pages, 15770 KiB

Open AccessFeature PaperArticle

Microwave-Assisted Oxidative Degradation of Lignin Catalyzed by Hydrogen Peroxide–Alkaline Ionic Liquid System

by Yuxin Qin, Dan Li, Subhan Mahmood, Jiajun Che, Tianhong Xiang and Shun Yao

Catalysts 2025, 15(4), 367; https://doi.org/10.3390/catal15040367 - 9 Apr 2025

Viewed by 323

Abstract

In recent years, various green solvents have played more and more important roles in catalysis and biomass studies. In this work, three imidazolium anion-based alkaline ionic liquids (ILs, including [BMIM]Im, [Ch]Im, and [N₄₂₂₂]Im) were selected to catalyze the oxidative degradation of [...] Read more.

In recent years, various green solvents have played more and more important roles in catalysis and biomass studies. In this work, three imidazolium anion-based alkaline ionic liquids (ILs, including [BMIM]Im, [Ch]Im, and [N₄₂₂₂]Im) were selected to catalyze the oxidative degradation of alkaline lignin by a microwave-assisted hydrogen peroxide–alkaline ionic liquid system for the first time, which aimed to promote the depolymerization and high-value conversion of lignin and increase the number of alcohol hydroxyl groups and the reactivity of lignin. The changes in the number of the alcohol hydroxyl groups of lignin before and after degradation were taken as the primary indices. As the main conditions, the influence of the microwave exposure time, microwave power, ionic liquid concentration, and hydrogen peroxide concentration on the degradation efficacy was subsequently examined for the ionic liquid that exhibited the most effective degradation performance. In addition, the extracted lignin degradation reaction solution was analyzed in combination with gas chromatography–mass spectrometry (GC–MS), and the degraded lignin solids were characterized by scanning electron microscopy (SEM), ultraviolet and visible (UV–Vis) spectroscopy, Fourier-transform infrared spectroscopy (FT–IR), and thermogravimetric and derivative thermogravimetric (TG–DTG) methods, which determined the composition of the degradation products, the degradation mechanism, and the intuitive structural changes in the lignin, thereby providing insights into the extent of lignin degradation with green solvents. Full article

(This article belongs to the Special Issue Topical Advisory Panel Members' Collection Series: Biomass Catalytic Conversion)

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15 pages, 3249 KiB

Open AccessFeature PaperArticle

Understanding Lipase-Deep Eutectic Solvent Interactions Towards Biocatalytic Esterification

by Can Liu and Jian Shi

Catalysts 2025, 15(4), 358; https://doi.org/10.3390/catal15040358 - 6 Apr 2025

Viewed by 277

Abstract

Deep eutectic solvents (DESs) have shown promise as a medium for extracting polar volatile fatty acids (VFAs) and in situ esterification of the extracted molecules using lipases. This solvent enhanced biocatalysis process can potentially streamline VFA separation from fermentation broth by integrating conversion [...] Read more.

Deep eutectic solvents (DESs) have shown promise as a medium for extracting polar volatile fatty acids (VFAs) and in situ esterification of the extracted molecules using lipases. This solvent enhanced biocatalysis process can potentially streamline VFA separation from fermentation broth by integrating conversion and extraction steps. Two commercial lipases from Aspergillus oryzae (AoL) and Candida rugosa (CrL) were evaluated in reaction systems containing hydrophilic or hydrophobic DESs using a newly optimized lipase assay. The optimal pH for both lipases was around 5.0, with a slight reduction in activity at pH 8.0 and a significant inhibition at pH 2.0. The impact of DES concentration on lipase activity varied depending on the specific DES–lipase pairs. Most hydrophilic DESs show good compatibility with the tested lipases. Specifically for choline chloride/ethylene glycol (1:2) and choline chloride/levulinic acid (1:2), taking into account the influence of pH, CrL activity increased with DES concentration. However, the hydrophobic DES thymol/2,6-dimethoxyphenol (1:2) demonstrated enhanced inhibitory effects on both lipases. Docking simulation helped explain the ligand–protein interactions but showed limited capability in predicting the compatibility of specific DES–lipase pairs due to its constraints in simulating flexible protein structures and the complex interactions between DES components and water. Full article

(This article belongs to the Special Issue Topical Advisory Panel Members' Collection Series: Biomass Catalytic Conversion)

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31 pages, 9891 KiB

Open AccessFeature PaperArticle

Selective Conversion of Glycerol to Acetol: Effect of the Preparation Method of CuAl Catalysts and Reaction Phase

by Francisco Maldonado-Martín, Lucía García, Joaquín Ruiz, Miriam Oliva and Jesús Arauzo

Catalysts 2025, 15(4), 348; https://doi.org/10.3390/catal15040348 - 2 Apr 2025

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Abstract

A group of CuAl catalysts were synthesized with a Cu/Al molar ratio of 1:1 using different preparation methods: coprecipitation, surfactant assisted coprecipitation, polymeric precursor, and self-combustion and then screened for the selective dehydration of glycerol to acetol. The catalysts were employed in glycerol [...] Read more.

A group of CuAl catalysts were synthesized with a Cu/Al molar ratio of 1:1 using different preparation methods: coprecipitation, surfactant assisted coprecipitation, polymeric precursor, and self-combustion and then screened for the selective dehydration of glycerol to acetol. The catalysts were employed in glycerol conversion at the same temperature (227 °C) in two different laboratory-scale systems, the first one at atmospheric pressure (gas phase) and the second one in a pressurized system at 34 absolute bar (liquid phase). The preparation method of the CuAl catalysts influenced the carbon yield to liquids and acetol selectivity. However, the reaction phase had a greater influence than the preparation method of the catalyst. In the gas phase, the carbon yield to liquids reached values above 40% and the carbon selectivity to acetol was higher than 90%. The highest acetol yield, 462.6 mg_acetol/g_glycerol, was obtained with the CuAl catalyst prepared by the surfactant-assisted coprecipitation method. This study provides a new perspective on catalyst design by highlighting the crucial role of preparation techniques in determining CuAl catalyst performance in the liquid and gas phases. Full article

(This article belongs to the Special Issue Topical Advisory Panel Members' Collection Series: Biomass Catalytic Conversion)

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12 pages, 2914 KiB

Open AccessArticle

Carbon-Coated Cobalt-Catalyzed Hydrodeoxygenation of Lipids to Alcohols

by Long Chen, Jing Wu, Ai Chang, Guo-Ping Lu and Chun Cai

Catalysts 2025, 15(3), 254; https://doi.org/10.3390/catal15030254 - 6 Mar 2025

Viewed by 654

Abstract

The abundant metal-catalyzed selective hydrodeoxygenation of lipids to alcohols has great industrial application potential. Herein, a carbon-coated Co catalyst has been fabricated by a simple detonation-reduction method. This material exhibits outstanding performance for the selective hydrodeoxygenation of lipids to alcohols (200 °C, 5 [...] Read more.

The abundant metal-catalyzed selective hydrodeoxygenation of lipids to alcohols has great industrial application potential. Herein, a carbon-coated Co catalyst has been fabricated by a simple detonation-reduction method. This material exhibits outstanding performance for the selective hydrodeoxygenation of lipids to alcohols (200 °C, 5 h, 2 MPa H₂, over 5 runs), which mainly benefits from the carbon layer on the Co surface. This carbon layer optimizes substrate adsorption, which enhances the H₂ adsorption process. The carbon coating also inhibits the oxidation of Co particles, resulting in the co-existence of Co⁰ and CoO, which is beneficial for H₂ activation. In addition, kinetic studies indicate that hydrogen activation should be included in the rate-determining step of this reaction. Full article

(This article belongs to the Special Issue Topical Advisory Panel Members' Collection Series: Biomass Catalytic Conversion)

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12 pages, 2909 KiB

Open AccessArticle

Ultrasound-Induced Construction of Cu_xCo_3−xO₄/Attapulgite for Catalytic Degradation of Toluene

by Haitao Zhang, Jian Shi, Chaoya Han, Zhizhao Song, Yao Xiao and Xiazhang Li

Catalysts 2025, 15(3), 252; https://doi.org/10.3390/catal15030252 - 6 Mar 2025

Viewed by 555

Abstract

With the increasing demand for air pollution control, the development of efficient and stable catalysts to degrade hazardous VOCs such as toluene has become particularly important. Herein, various copper-doped attapulgite-supported cobalt oxide spinel composites (Cu_xCo_3−xO₄/ATP) were synthesized [...] Read more.

With the increasing demand for air pollution control, the development of efficient and stable catalysts to degrade hazardous VOCs such as toluene has become particularly important. Herein, various copper-doped attapulgite-supported cobalt oxide spinel composites (Cu_xCo_3−xO₄/ATP) were synthesized using an ultrasonic-assisted precipitation method. The results showed that the abundant Si-OH groups on the surface of ATP played a crucial role in anchoring Co, and the instantaneous high-energy input of ultrasonication facilitated the formation of Si-O-Co bonds in Co₃O₄/ATP. The doping of Cu ions induced the expansion of the Co₃O₄ lattice, resulting in a significant number of oxygen vacancies. The ultrasound-induced synthesized Cu_0.1Co_2.9O₄/ATP catalyst exhibited the best catalytic oxidation performance, achieving a 99% toluene degradation rate at 300 °C under a weight hourly space velocity (WHSV) of 10,000 mL·g⁻¹ h⁻¹ and initial toluene concentration of 1000 ppm, along with high stability during 12 h of continuous running. This work presents a new strategy for the cost-effective catalytic elimination of VOCs. Full article

(This article belongs to the Special Issue Topical Advisory Panel Members' Collection Series: Biomass Catalytic Conversion)

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19 pages, 3854 KiB

Open AccessFeature PaperArticle

One-Step Ball Milling Synthesis of Zr-Based Mixed Oxides for the Catalytic Study of Methyl Levulinate Conversion into γ-Valerolactone Under Microwave Irradiation

by Noelia Lázaro, Marina Ronda-Leal, Carolina Vargas, Weiyi Ouyang and Antonio Pineda

Catalysts 2025, 15(1), 35; https://doi.org/10.3390/catal15010035 - 3 Jan 2025

Viewed by 813

Abstract

Several mixed oxides composed of Fe₃O₄, ZrO₂, and Al₂O₃ with different molar ratios were synthesized through a direct and simple mechanochemical approach. Subsequently, their physicochemical properties were investigated using a wide range of techniques, [...] Read more.

Several mixed oxides composed of Fe₃O₄, ZrO₂, and Al₂O₃ with different molar ratios were synthesized through a direct and simple mechanochemical approach. Subsequently, their physicochemical properties were investigated using a wide range of techniques, including TEM (transmission electron microscopy), XPS (X-ray photoelectron spectroscopy), XRD (X-ray diffraction), and N₂ adsorption/desorption, among others. These materials showed high surface areas and increased acidity compared to their respective counterparts. The catalytic activity of the synthesized materials was evaluated in the conversion of methyl levulinate (MEL) to γ-valerolactone (GVL) under microwave irradiation conditions, employing different alcohols as H-donor solvents (ethanol, 2-propanol, and 2-butanol). Due to their improved physicochemical properties originating from the ball-milling method, the as-synthesized materials (ZrFeOx 1:1, AlZrFeOx (5), and AlZrFeOx (10)) exhibited conversion rates of up to 99%, with complete selectivity for GVL after a relatively short reaction time of 30 min. Full article

(This article belongs to the Special Issue Topical Advisory Panel Members' Collection Series: Biomass Catalytic Conversion)

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12 pages, 2216 KiB

Open AccessArticle

Enhanced Thermostability of Laccase from Myceliophthora thermophila Through Conjugation with mPEG-SC

by Leonardo L. O. García, Raissa H. S. Florindo, Vivian Saez, Robert Wojcieszak, Jose Ramon and Ivaldo Itabaiana Jr.

Catalysts 2024, 14(12), 887; https://doi.org/10.3390/catal14120887 - 3 Dec 2024

Viewed by 1042

Abstract

The search for more sustainable reaction conditions has been necessary to obtain more selective processes. In this context, laccases have gained great notoriety in recent years. However, these enzymes are unstable in organic solvents and have low thermal stability. Alternatively, conjugation with PEG [...] Read more.

The search for more sustainable reaction conditions has been necessary to obtain more selective processes. In this context, laccases have gained great notoriety in recent years. However, these enzymes are unstable in organic solvents and have low thermal stability. Alternatively, conjugation with PEG (PEGylation) can be essential to overcome these problems. In this work, the commercial laccase from Myceliophthora thermophila (LacMT) was subjected to PEGylation with PEG functionalized as succinimidyl carbonate (mPEG-SC), followed by assessing its thermal stability and catalytic activity. Mono-PEGylated LacMT derivatives were obtained, with less than 50% of the enzyme remaining in its native form. In addition, 10% of the bi-PEGylated species was successfully obtained according to gel electrophoresis analysis. The PEGylated derivatives showed a significantly reduced ABTS oxidation activity (98 ± 3 U/mg) compared to the native LacMT (407 ± 9 U/mg) but higher than the control enzyme without PEGylation (51 ± 2 U/mg), demonstrating that the addition of activated PEG to the protein resulted in better protection against the harmful action of the pH change required in the process. PEGylated LacMT retained more than twice the initial activity of the native protein at 40 °C during 24 h. In addition, PEGylated LacMT exhibited kinetic changes, whereas the catalytic turnover rate (k_cat) of the PEGylated enzyme was reduced by 27% compared to the control. These findings are being reported for the first time. This sets precedents for constructing efficient catalytic systems involving laccases since no immobilized biocatalyst or commercial conjugate contains these proteins. Full article

(This article belongs to the Special Issue Topical Advisory Panel Members' Collection Series: Biomass Catalytic Conversion)

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13 pages, 872 KiB

Open AccessFeature PaperArticle

Heterogeneization of Biodiesel Production by Simultaneous Esterification and Transesterification of Oleins

by Vanesa Domínguez-Barroso, Concepción Herrera, María Ángeles Larrubia, Carlos Gonzalo López, Diego Bouzas Ramos and Luis J. Alemany

Catalysts 2024, 14(12), 871; https://doi.org/10.3390/catal14120871 - 29 Nov 2024

Viewed by 1080

Abstract

The production of biodiesel via simultaneous esterification and transesterification reactions of residual fats such as palm oleins, with variable TG and FFA composition, using methanol and methane sulfonic acid (MSA) or an acid carbon-based structured catalyst (SO₃H-C) as homogeneous and heterogeneous [...] Read more.

The production of biodiesel via simultaneous esterification and transesterification reactions of residual fats such as palm oleins, with variable TG and FFA composition, using methanol and methane sulfonic acid (MSA) or an acid carbon-based structured catalyst (SO₃H-C) as homogeneous and heterogeneous catalysts respectively, has been investigated. The influence of various parameters, such as methanol to oil molar ratio, operating temperature, amount of catalyst, or nature and composition of the raw materials on the fatty acid methyl esters (FAME) yield was studied. It was determined that increasing the methanol to oil molar ratio resulted in an increase in the conversion of TG and FFA and a higher FAME yield; besides, reaction temperature has a strong effect. The best conditions tested to obtain the highest FAME yield (99.2%) was a methanol to oil molar ratio of 12:1, 120 °C (12 bar), a reaction time of at least 1 h, and 3% MSA as a homogeneous catalyst. The work demonstrated that an acidic solid catalyst, SO₃H-C, homemade prepared, could be used as a heterogeneous catalyst in the simultaneous process under the optimized reaction conditions, achieving a complete esterification conversion with some limitations with respect to the transesterification reaction and a FAME yield close to 90.5%. Full article

(This article belongs to the Special Issue Topical Advisory Panel Members' Collection Series: Biomass Catalytic Conversion)

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20 pages, 3760 KiB

Open AccessArticle

Carbon-Based Catalysts from H₃PO₄ Activation of Olive Stones for Sustainable Solketal and γ-Valerolactone Production

by Javier Torres-Liñán, Miguel García-Rollán, Ramiro Ruiz-Rosas, Juana María Rosas, José Rodríguez-Mirasol and Tomás Cordero

Catalysts 2024, 14(12), 869; https://doi.org/10.3390/catal14120869 - 28 Nov 2024

Viewed by 765

Abstract

The use of activated carbon-based catalysts for the production of solketal and γ-valerolactone (GVL), two products of interest for biorefinery processes, was investigated. Activated carbons (ACs) were prepared by chemical activation of olive stones, an agricultural byproduct, using H₃PO₄ to [...] Read more.

The use of activated carbon-based catalysts for the production of solketal and γ-valerolactone (GVL), two products of interest for biorefinery processes, was investigated. Activated carbons (ACs) were prepared by chemical activation of olive stones, an agricultural byproduct, using H₃PO₄ to olive stone mass impregnation ratios (IRs) of 1:1 and 3:1, and under nitrogen or air atmosphere. The ACs showed S_BET values of 1130–1515 m²/g, owing to the presence of micropores (0.45–0.60 cm³/g). The use of an IR of 3:1 delivered a wider pore size distribution, with mesopore volume increasing up to 1.36 cm³/g. XPS confirmed the presence of phosphorus groups with surface concentrations of 2.2–3.2 wt% strongly bonded the AC surface through C-O-P bonds. The ACs were tested as acid catalysts for the acetalization of glycerol in a stirred batch reactor at temperatures of 30–50 °C, glycerol concentrations of 1.5 to 3.4 mol/L, and 1–3 wt% catalytic loading. The catalytic activity was clearly correlated with the quantity of C-O-P acid groups determined by TPD, which increased when ACs were prepared under air atmosphere. The AC prepared with IR 3:1 under air achieved full selectivity to solketal, with activation energy of 49 kJ/mol and conversion of up to 70%, matching the equilibrium conversion value under the optimum reaction conditions. A bifunctional catalyst was prepared over this AC by deposition of 5 wt% zirconium and tested in stirred batch reactor for the hydrogenation of levulinic acid (LA) using isopropyl alcohol (IPA) as solvent and H₂ donor, with LA:IPA ratios from 1:1 to 1:7 and temperatures between 160–200 °C. The catalyst reached full LA conversion and a GVL yield higher than 80% after only 12 h at 200 °C. A test conducted in the presence of water revealed that it was an inhibitor of the reaction. The identification of isopropyl levulinate as an intermediate suggests that the most likely reaction pathway was dehydration, followed by hydrogenation and cyclization, to obtain GVL. Kinetic modelling of the results showed a value of 42 kJ/mol for the hydrogenation step. The reusability of the catalyst was tested for five consecutive reaction cycles, maintaining most of the activity and selectivity towards GVL. Full article

(This article belongs to the Special Issue Topical Advisory Panel Members' Collection Series: Biomass Catalytic Conversion)

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19 pages, 3245 KiB

Open AccessArticle

Catalytic Transformation of Biomass-Derived Hemicellulose Sugars by the One-Pot Method into Carboxylic Acids Using Heterogeneous Catalysts

by Natalia Sobuś, Marcin Piotrowski and Izabela Czekaj

Catalysts 2024, 14(12), 857; https://doi.org/10.3390/catal14120857 - 25 Nov 2024

Viewed by 691

Abstract

This article presents the conditions for the transformation of pulp containing mixtures that occur in the hemicellulose fraction derived from lignocellulosic biomass. Selected materials with strong acid centers were used as catalytic materials: ion exchange resins, including AMBERLYST 15(H) and DOWEX DR-G8(H), and [...] Read more.

This article presents the conditions for the transformation of pulp containing mixtures that occur in the hemicellulose fraction derived from lignocellulosic biomass. Selected materials with strong acid centers were used as catalytic materials: ion exchange resins, including AMBERLYST 15(H) and DOWEX DR-G8(H), and selected zeolite in the hydrogen form of the Beta type (H-BEA). The group was marked with the abbreviations M1, M2 and M3, where it differs in the content of xylose, mannose, galactose, glucose, rhamnose and uronic acids. The catalytic process was carried out in the reactor as a one-pot technique at temperatures of 180–250 °C for 1–5 h. Based on the collected results, the transformation products of hemicellulose pulp were determined and the catalytic abilities of selected materials were determined. The proposed conditions led to the production of organic acids. Levulinic acid was obtained with a selectivity of 25.95% after 1 h of the process at a temperature of 250 °C with the participation of H-BEA, and lactic acid was obtained with a selectivity of 73.28% after 5 h of the process at a temperature of 250 °C using DOWEX DRG8(H). The presence of oxalic, propionic and acetic acids was also observed. Full article

(This article belongs to the Special Issue Topical Advisory Panel Members' Collection Series: Biomass Catalytic Conversion)

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11 pages, 962 KiB

Open AccessFeature PaperArticle

Analysis of Reaction Conditions in Palmitic Acid Deoxygenation for Fuel Production

by Karoline K. Ferreira, Lucília S. Ribeiro and Manuel Fernando R. Pereira

Catalysts 2024, 14(12), 853; https://doi.org/10.3390/catal14120853 - 24 Nov 2024

Viewed by 1189

Abstract

The development of effective catalytic systems for deoxygenation reactions is critical to the conversion of renewable feedstocks into sustainable fuels. In this work, the influence of various reaction parameters on the conversion of palmitic acid into alkanes, such as temperature, stirring rate, reaction [...] Read more.

The development of effective catalytic systems for deoxygenation reactions is critical to the conversion of renewable feedstocks into sustainable fuels. In this work, the influence of various reaction parameters on the conversion of palmitic acid into alkanes, such as temperature, stirring rate, reaction time, H₂ pressure, amount of catalyst and substrate concentration was evaluated using the commercial Co-Mo/Al₂O₃ catalyst. In parallel, bimetallic Co-Mo catalysts supported on carbon nanotubes (CNTs) were prepared and characterized using various techniques, and their catalytic performance was assessed under the optimized conditions. The results showed that palmitic acid can be efficiently converted at 350 °C for 6 h at 30 bar H₂ pressure, stirring at 150 rpm and using 0.25 g of catalyst and 0.50 g of palmitic acid in 50 mL of n-decane. Under these conditions, a complete substrate conversion and yields of 89.4 and 4.8% of C₁₆ and C₁₅ were achieved. In addition, Co-Mo/CNT_ox presented a similar catalytic performance as the commercial one, with a final result of 90.9% yield in C₁₆. These findings point out the potential of using Co-Mo/CNT_ox as a competitive alternative to liquid fuel production. Full article

(This article belongs to the Special Issue Topical Advisory Panel Members' Collection Series: Biomass Catalytic Conversion)

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24 pages, 4263 KiB

Open AccessArticle

Production of Aviation Fuel-Range Hydrocarbons Through Catalytic Co-Pyrolysis of Polystyrene and Southern Pine

by Ayden Kemp, Tawsif Rahman, Hossein Jahromi and Sushil Adhikari

Catalysts 2024, 14(11), 806; https://doi.org/10.3390/catal14110806 - 9 Nov 2024

Viewed by 2206

Abstract

Sustainable aviation fuels (SAFs), produced from waste and renewable sources, are a promising means for reducing net greenhouse gas emissions from air travel while still maintaining the quality of air transportation expected. In this work, the catalytic co-pyrolysis of polystyrene and pine with [...] Read more.

Sustainable aviation fuels (SAFs), produced from waste and renewable sources, are a promising means for reducing net greenhouse gas emissions from air travel while still maintaining the quality of air transportation expected. In this work, the catalytic co-pyrolysis of polystyrene and pine with red mud (bauxite residue) and ZSM-5 catalysts at temperatures of 450 °C, 500 °C, and 550 °C was investigated as a method for producing aromatic hydrocarbons with carbon numbers ranging from 7 to 17 for use as additives to blend with SAF produced through other methods to add the required quantity of aromatic molecules to these blends. The maximum yield of kerosene-range aromatic hydrocarbons was 620 mg per gram of feedstock (62% of feedstock was converted to kerosene-range hydrocarbons) obtained at 550 °C in the presence of ZSM-5. Additionally, it was noted that a positive synergy exists between pine and polystyrene feedstocks during co-pyrolysis that cracks solid and liquid products into gaseous products similarly to that of a catalyst. The co-pyrolysis of pine and polystyrene without a catalyst produced on average 17% or 36.3 mg more kerosene-range hydrocarbons than predicted, with a maximum yield of 266 mg of C7–C17 aromatic hydrocarbons per gram of feedstock (26.6% conversion of initial feedstock) obtained at 550 °C. Full article

(This article belongs to the Special Issue Topical Advisory Panel Members' Collection Series: Biomass Catalytic Conversion)

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18 pages, 3031 KiB

Open AccessArticle

Synergistic Effects of Nonthermal Plasma and Solid Acid Catalysts in Thermo-Catalytic Glycerol Dehydration

by Lu Liu, Fei Yu, Siqun Wang and Xiaofei Philip Ye

Catalysts 2024, 14(11), 790; https://doi.org/10.3390/catal14110790 - 6 Nov 2024

Viewed by 722

Abstract

To enhance the bio-based synthesis of acrolein from glycerol, a hybrid approach combining in situ nonthermal plasma (NTP) with thermo-catalytic dehydration was employed. This study investigated the impact of the reaction temperature and NTP discharge field strength on glycerol conversion, acrolein selectivity, byproduct [...] Read more.

To enhance the bio-based synthesis of acrolein from glycerol, a hybrid approach combining in situ nonthermal plasma (NTP) with thermo-catalytic dehydration was employed. This study investigated the impact of the reaction temperature and NTP discharge field strength on glycerol conversion, acrolein selectivity, byproduct formation, and coke deposition using two catalysts of silicotungstic acid supported on mesoporous alumina and silica. The results revealed that, while the reaction temperature and NTP field strength exhibited complex interactions, the in situ application of NTP markedly improved both glycerol conversion and acrolein selectivity when optimized for specific temperature–NTP field strength combinations. Additionally, the reaction mechanisms of glycerol dehydration with the two catalysts, in the presence and absence of NTP, were systematically analyzed and discussed based on the experimental data. Full article

(This article belongs to the Special Issue Topical Advisory Panel Members' Collection Series: Biomass Catalytic Conversion)

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17 pages, 4953 KiB

Open AccessArticle

Oxidation of Geraniol on Vermiculite—The Influence of Selected Parameters on the Oxidation Process

by Sylwia Gajewska, Agnieszka Wróblewska, Anna Fajdek-Bieda, Adrianna Kamińska, Joanna Sreńscek-Nazzal, Piotr Miądlicki and Beata Michalkiewicz

Catalysts 2024, 14(10), 714; https://doi.org/10.3390/catal14100714 - 12 Oct 2024

Cited by 1 | Viewed by 1420

Abstract

Geraniol is a compound belonging to the group of monoterpenes that finds many applications in organic syntheses, medicine and cosmetics. The following properties of geraniol and its derivatives are of particular interest in medicine: its anti-inflammatory, antioxidant, antimicrobial and anticancer effects. The geraniol [...] Read more.

Geraniol is a compound belonging to the group of monoterpenes that finds many applications in organic syntheses, medicine and cosmetics. The following properties of geraniol and its derivatives are of particular interest in medicine: its anti-inflammatory, antioxidant, antimicrobial and anticancer effects. The geraniol oxidation process was carried out using a mineral of natural origin—vermiculite. Vermiculite is a catalyst that perfectly fits into modern trends in the organic industry, where the aim is to use cheap, renewable and relatively easily available catalytic materials (vermiculite is found on continents including Africa, North America, South America, Australia and Asia). Preliminary studies on the oxidation process of geraniol on vermiculite was carried out in a glass apparatus using molecular oxygen supplied by means of a bubbler and magnetic stirrer with a heating function. During the oxidation process of geraniol on vermiculite, the influence of the following parameters was examined: the temperature, amount of catalyst and reaction time. The main parameters of the process, on the basis of which the most favorable process conditions were selected, were the selectivity of the transformation to 2,3-epoxygeraniol, citral and 2,3-epoxycitral, and the conversion of geraniol. The composition of the post-reaction mixtures was determined qualitatively and quantitatively using the gas chromatography method. In addition, vermiculite was subjected to instrumental tests, such as XRD, SEM, EDX, FTIR and UV-VIS. Moreover, the specific surface area, pore volume and pore volume distribution were estimated on the basis of N2 sorption at −196 °C and also the acid-site concentration in vermiculite was established. Full article

(This article belongs to the Special Issue Topical Advisory Panel Members' Collection Series: Biomass Catalytic Conversion)

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14 pages, 3381 KiB

Open AccessArticle

Optimizing Algal Oil Extraction and Transesterification Parameters through RSM, PCA, and MRA for Sustainable Biodiesel Production

by Lingdi Tang, Ali Raza Otho, Mahmood Laghari, Abdul Rahim Junejo, Sheeraz Aleem Brohi, Farman Ali Chandio, Sohail Ahmed Otho, Li Hao, Irshad Ali Mari, Jahangeer Dahri and Jamshed Ali Channa

Catalysts 2024, 14(10), 675; https://doi.org/10.3390/catal14100675 - 30 Sep 2024

Viewed by 1780

Abstract

This study presents a comprehensive optimization of algal oil extraction and transesterification for sustainable biodiesel production. Freshwater Spirogyra algae underwent Soxhlet extraction using n-hexane. response surface methodology (RSM), principal component analysis (PCA), and multivariate regression analysis (MRA) were employed to investigate the effects [...] Read more.

This study presents a comprehensive optimization of algal oil extraction and transesterification for sustainable biodiesel production. Freshwater Spirogyra algae underwent Soxhlet extraction using n-hexane. response surface methodology (RSM), principal component analysis (PCA), and multivariate regression analysis (MRA) were employed to investigate the effects of biomass–solvent ratio (BSR), algae particle size (APS), and extraction-contact time (E-CT) on algal oil yield (AOY). The extracted oil was then converted to biodiesel via transesterification, and the impacts of the methanol–oil ratio (MOR) and transesterification-contact time (T-CT) on biodiesel conversion efficiency (BCE) were analyzed. Results demonstrate that optimal BSR, APS, and E-CT for maximal AOY are 1:7, 400 µm, and 3–4 h, respectively. For transesterification, a MOR of 12:1 and a T-CT of 4 h yielded the highest BCE. Predictive models exhibited exceptional accuracy, with R² values of 0.916 and 0.950 for AOY and BCE, respectively. The produced biodiesel complied with ASTM D6751 and EN 14214, showcasing its potential for renewable energy applications. Full article

(This article belongs to the Special Issue Topical Advisory Panel Members' Collection Series: Biomass Catalytic Conversion)

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12 pages, 5519 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Biomass-Derived Co/MPC Nanocomposites for Effective Sensing of Hydrogen Peroxide via Electrocatalysis Reduction

by Mei Wang, Jin Cai, Lihua Jiao and Quan Bu

Catalysts 2024, 14(9), 624; https://doi.org/10.3390/catal14090624 - 16 Sep 2024

Viewed by 1167

Abstract

Utilizing the full potential of reproducible biomass resources is crucial for the sustainable development of humanity. In this study, biochar (MPC) was prepared through the microwave-assisted pyrolysis of sugarcane bagasse. Subsequently, Co nanoparticles were introduced by microwave-assisted hydrothermal treatment to form a highly [...] Read more.

Utilizing the full potential of reproducible biomass resources is crucial for the sustainable development of humanity. In this study, biochar (MPC) was prepared through the microwave-assisted pyrolysis of sugarcane bagasse. Subsequently, Co nanoparticles were introduced by microwave-assisted hydrothermal treatment to form a highly dispersive Co/MPC material. Characterization results indicated that Co nanoparticles were wrapped by thin carbon layers and uniformly dispersed on a carbon-based skeleton via a microwave-assisted hydrothermal synthesis approach, providing high-activity space. Thus, the prepared material was limited to glassy carbon; on the electrode surface, a cobalt-based sensing platform (Co/MPC/GCE) was built. On the basis of this constructed sensing platform, a linear equation was fitted by the concentration change of current signal I and H₂O₂. The linear range was 0.55–100.05 mM; the detection limit was 1.38 μM (S/N = 3); and the sensitivity was 103.45 μA cm⁻² mM⁻¹. In addition, the effect this sensor had on H₂O₂ detection of actual water samples was conducted by using a standard addition recovery method; results disclosed that the recovery rate and RSD of H₂O₂ in tap water samples were 94.0–97.6% and 4.1–6.5%, respectively. Full article

(This article belongs to the Special Issue Topical Advisory Panel Members' Collection Series: Biomass Catalytic Conversion)

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16 pages, 2560 KiB

Open AccessArticle

Investigation into the Fuel Characteristics of Biodiesel Synthesized through the Transesterification of Palm Oil Using a TiO₂/CH₃ONa Nanocatalyst

by Cherng-Yuan Lin and Shun-Lien Tseng

Catalysts 2024, 14(9), 623; https://doi.org/10.3390/catal14090623 - 16 Sep 2024

Cited by 1 | Viewed by 1282

Abstract

Biodiesel is a renewable and sustainable alternative fuel to petrol-derived diesel. Decreasing the operating costs by improving the catalyst’s characteristics is an effective way to increase the competitiveness of biodiesel in the fuel market. An aqueous solution of sodium methoxide (CH₃ONa), [...] Read more.

Biodiesel is a renewable and sustainable alternative fuel to petrol-derived diesel. Decreasing the operating costs by improving the catalyst’s characteristics is an effective way to increase the competitiveness of biodiesel in the fuel market. An aqueous solution of sodium methoxide (CH₃ONa), which is a traditional alkaline catalyst, was immersed in nanometer-sized particles of titanium dioxide (TiO₂) powder to prepare the strong alkaline catalyst TiO₂/CH₃ONa. The immersion method was used to enhance the transesterification reaction. The mixture of TiO₂ and CH₃ONa was calcined in a high-temperature furnace in a range between 150 and 450 °C continuously for 4 h. The heterogeneous alkaline catalyst TiO₂/CH₃ONa was then used to catalyze the strong alkaline transesterification reaction of palm oil with methanol. The highest content of fatty acid methyl esters (FAMEs), which amounted to 95.9%, was produced when the molar ratio of methanol to palm oil was equal to 6, and 3 wt.% TiO₂/CH₃ONa was used, based on the weight of the palm oil. The FAMEs produced from the above conditions were also found to have the lowest kinematic viscosity of 4.17 mm²/s, an acid value of 0.32 mg KOH/g oil, and a water content of 0.031 wt.%, as well as the highest heating value of 40.02 MJ/kg and cetane index of 50.05. The lower catalyst amount of 1 wt.%, in contrast, resulted in the lowest cetane index of 49.31. The highest distillation temperature of 355 °C was found when 3 wt.% of the catalyst was added to the reactant mixture with a methanol/palm oil molar ratio of 6. The prepared catalyst is considered effective for improving the fuel characteristics of biodiesel. Full article

(This article belongs to the Special Issue Topical Advisory Panel Members' Collection Series: Biomass Catalytic Conversion)

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Review

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40 pages, 16582 KiB

Open AccessReview

Cold Plasma Techniques for Sustainable Material Synthesis and Climate Change Mitigation: A Review

by Nitesh Joshi and Sivachandiran Loganathan

Catalysts 2024, 14(11), 802; https://doi.org/10.3390/catal14110802 - 8 Nov 2024

Viewed by 1933

Abstract

In recent years, the emission of greenhouse gases (GHGs) has increased significantly, contributing to global warming. Among these GHGs, CH₄, CO₂, and CO are particularly potent contributors. Remediation techniques primarily rely on materials capable of capturing, storing, and converting [...] Read more.

In recent years, the emission of greenhouse gases (GHGs) has increased significantly, contributing to global warming. Among these GHGs, CH₄, CO₂, and CO are particularly potent contributors. Remediation techniques primarily rely on materials capable of capturing, storing, and converting these gases. Catalytic processes, particularly heterogeneous catalysis, are essential to chemical and petrochemical industries as well as environmental remediation. Due to the growing demand for catalysts, efforts are being made to reduce energy consumption and make technologies more environmentally friendly. Green chemistry emphasizes minimizing the use of hazardous reactants and harmful solvents in chemical processes. Achieving these principles should be paired with processes that reduce time and costs in catalyst preparation while improving their efficiency. Non-thermal plasma (NTP) has been widely used for the preparation of supported metal catalysts. NTP has attracted significant attention for its ability to improve the physicochemical properties of catalysts, enhancing process efficiency through low-temperature operation and shorter processing times. NTP has been applied to various catalyst synthesis techniques, including reduction, oxidation, metal oxide doping, surface etching, coating, alloy formation, surface treatment, and surface cleaning. Plasma-prepared transition-metal catalysts offer advantages over conventionally prepared catalysts due to their unique material properties. These properties enhance catalytic activity by lowering the activation energy barrier, improving stability, and increasing conversion and selectivity compared to untreated samples. This review demonstrates how plasma activation modifies material properties and, based on extensive literature, illustrates its potential to combat climate change by converting CO₂, CH₄, CO, and other gases, showcasing the benefits of plasma-treated materials and catalysts. A succinct introduction to this review outlines the advantages of plasma-based synthesis and modification over traditional synthesis techniques. The introduction also highlights the various types of plasma and their physical characteristics across different factors. Additionally, this review addresses methods by which materials are synthesized and modified using plasma. The latter section of this review discusses the use of non-thermal plasma for greenhouse gas mitigation, covering applications such as the dry reforming of CH₄, CO and CH₄ oxidation, CO₂ reduction, and other uses of plasma-modified catalysts. Full article

(This article belongs to the Special Issue Topical Advisory Panel Members' Collection Series: Biomass Catalytic Conversion)

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29 pages, 10746 KiB

Open AccessReview

Selective Control of Catalysts for Glycerol and Cellulose Hydrogenolysis to Produce Ethylene Glycol and 1,2-Propylene Glycol: A Review

by Jihuan Song, Dan Wang, Qiyuan Wang, Chenmeng Cui and Ying Yang

Catalysts 2024, 14(10), 685; https://doi.org/10.3390/catal14100685 - 2 Oct 2024

Viewed by 1478

Abstract

The bioconversion of cellulose and the transformation of glycerol can yield various diols, aligning with environmental sustainability goals by reducing dependence on fossil fuels, lowering raw material costs, and promoting sustainable development. However, in the selective hydrogenolysis of glycerol to ethylene glycol (EG) [...] Read more.

The bioconversion of cellulose and the transformation of glycerol can yield various diols, aligning with environmental sustainability goals by reducing dependence on fossil fuels, lowering raw material costs, and promoting sustainable development. However, in the selective hydrogenolysis of glycerol to ethylene glycol (EG) and 1,2-propylene glycol (1,2-PG), challenges such as low selectivity of catalytic systems, poor stability, limited renewability, and stringent reaction conditions remain. The production of diols from cellulose involves multiple reaction steps, including hydrolysis, isomerization, retro-aldol condensation, hydrogenation, and dehydration. Consequently, the design of highly efficient catalysts with multifunctional active sites tailored to these specific reaction steps remains a significant challenge. This review aims to provide a comprehensive overview of the selective regulation of catalysts for producing EG and 1,2-PG from cellulose and glycerol. It discusses the reaction pathways, process methodologies, catalytic systems, and the performance of catalysts, focusing on active site characteristics. By summarizing the latest research in this field, we aim to offer a detailed understanding of the state-of-the-art in glycerol and cellulose conversion to diols and provide valuable guidance for future research and industrial applications. Through this review, we seek to clarify the current advancements and selective control strategies in diol production from glycerol or cellulose, thereby offering critical insights for future investigations and industrial scale-up. Full article

(This article belongs to the Special Issue Topical Advisory Panel Members' Collection Series: Biomass Catalytic Conversion)

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34 pages, 3135 KiB

Open AccessFeature PaperEditor’s ChoiceReview

The Role of Catalysts in Life Cycle Assessment Applied to Biogas Reforming

by Sergio Nogales-Delgado and Juan Félix González González

Catalysts 2024, 14(9), 592; https://doi.org/10.3390/catal14090592 - 3 Sep 2024

Cited by 1 | Viewed by 1223

Abstract

The real implementation of biogas reforming at an industrial scale to obtain interesting products (like hydrogen or syngas) is a developing research field where multidisciplinary teams are continuously adding improvements and innovative technologies. These works can contribute to the proliferation of green technologies [...] Read more.

The real implementation of biogas reforming at an industrial scale to obtain interesting products (like hydrogen or syngas) is a developing research field where multidisciplinary teams are continuously adding improvements and innovative technologies. These works can contribute to the proliferation of green technologies where the circular economy and sustainability are key points. To assess the sustainability of these processes, there are different tools like life cycle assessment (LCA), which involves a complete procedure where even small details count to consider a certain technology sustainable or not. The aim of this work was to review works where LCA is applied to different aspects of biogas reforming, focusing on the role of catalysts, which are essential to improve the efficiency of a certain process but can also contribute to its environmental impact. In conclusion, catalysts have an influence on LCA through the improvement of catalytic performance and the impact of their production, whereas other aspects related to biogas or methane reforming could equally affect their catalytic durability or reusability, with a subsequent effect on LCA. Further research about this subject is required, as this is a continuously changing technology with plenty of possibilities, in order to homogenize this research field. Full article

(This article belongs to the Special Issue Topical Advisory Panel Members' Collection Series: Biomass Catalytic Conversion)

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