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Recent Advances on Biomass Conversion and CO2 Valorization: Steeping towards a Circular Economy

A special issue of Molecules (ISSN 1420-3049). This special issue belongs to the section "Green Chemistry".

Deadline for manuscript submissions: 31 March 2025 | Viewed by 9216

Special Issue Editors

Dr. Ana Belén Dongil

E-Mail Website
Guest Editor
Institute of Catalysis and Petrochemistry, CSIC, c/Marie Curie No. 2, Cantoblanco, 28049 Madrid, Spain
Interests: heterogeneous catalysis; CO2; biomass
Special Issues, Collections and Topics in MDPI journals
Prof. Dr. José Antonio Odriozola

E-Mail Website
Guest Editor
Inorganic Chemistry Department and the Materials Science Institute, University of Seville, Av. Américo Vespucio 49, 41092 Sevilla, Spain
Interests: heterogeneous catalysis; CO2; biomass
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

The need to decrease current CO2 emissions due to human activity is clear as it has critical consequences for the environment. This has prompted research on alternatives to fossil-fuel use as well as technologies to capture CO2 and its utilization. There are several strategies that have been studied, such as increasing the efficiency of the current process, using carbon-neutral sources or capturing the CO2 produced to either store or use it.

Considering this, the aim of this Special Issue is to cover the recent state-of-the-art technology on CO2 and biomass conversion.

With this Special Issue, we welcome original contributions in the fields of biomass and CO2 conversion. The coverage of this Special Issue includes but is not limited to:

  • Materials for CO2 capture;
  • The catalytic conversion of CO2;
  • Biomass conversion;
  • Life cycle analysis, economic, environmental, and social aspects of CO2 capture, separation, storage or utilization.
  • Life cycle analysis, economic, environmental, and social aspects of biomass conversion.

Dr. Ana Belén Dongil
Prof. Dr. José Antonio Odriozola
Guest Editors

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Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Molecules is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2700 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • CO2 valorization
  • biomass conversion
  • circular economy
  • catalysis

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Published Papers (6 papers)

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Research

19 pages, 3979 KiB  
Article
Comprehensive Analysis of Biomass from Chlorella sorokiniana Cultivated with Industrial Flue Gas as the Carbon Source
by Arjun H. Banskota, Roumiana Stefanova, Joseph P. M. Hui, Tessa Bermarija, Kevin Stemmler, Patrick J. McGinn and Stephen J. B. O’Leary
Molecules 2024, 29(14), 3368; https://doi.org/10.3390/molecules29143368 - 18 Jul 2024
Viewed by 1256
Abstract
Chlorella sorokiniana, isolated from a pond adjacent to a cement plant, was cultured using flue gas collected directly from kiln emissions using 20 L and 25000 L photobioreactors. Lipids, proteins, and polysaccharides were analyzed to understand their overall composition for potential applications. [...] Read more.
Chlorella sorokiniana, isolated from a pond adjacent to a cement plant, was cultured using flue gas collected directly from kiln emissions using 20 L and 25000 L photobioreactors. Lipids, proteins, and polysaccharides were analyzed to understand their overall composition for potential applications. The lipid content ranged from 17.97% to 21.54% of the dry biomass, with carotenoid concentrations between 8.4 and 9.2 mg/g. Lutein accounted for 55% of the total carotenoids. LC/MS analysis led to the identification of 71 intact triacylglycerols, 8 lysophosphatidylcholines, 10 phosphatidylcholines, 9 monogalactosyldiacylglycerols, 12 digalactosyldiacylglycerols, and 1 sulfoquinovosyl diacylglycerol. Palmitic acid, oleic acid, linoleic acid, and α-linolenic acid were the main fatty acids. Polyunsaturated fatty acid covers ≥ 56% of total fatty acids. Protein isolates and polysaccharides were also extracted. Protein purity was determined to be ≥75% by amino acid analysis, with all essential amino acids present. Monomer analysis of polysaccharides suggested that they are composed of mainly D-(+)-mannose, D-(+)-galactose, and D-(+)-glucose. The results demonstrate that there is no adverse effect on the metabolite profile of C. sorokiniana biomass cultured using flue gas as the primary carbon source, revealing the possibility of utilizing such algal biomass in industrial applications such as animal feed, sources of cosmeceuticals, and as biofuel. Full article
(This article belongs to the Special Issue Recent Advances on Biomass Conversion and CO2 Valorization: Steeping towards a Circular Economy)
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22 pages, 5743 KiB  
Article
Potential Large-Scale CO2 Utilisation for Salicylic Acid Production via a Suspension-Based Kolbe–Schmitt Reaction in Toluene
by Omar Mohammad, Jude A. Onwudili and Qingchun Yuan
Molecules 2024, 29(11), 2527; https://doi.org/10.3390/molecules29112527 - 27 May 2024
Viewed by 1634
Abstract
Conversion of CO2 into organic chemicals offers a promising route for advancing the circularity of carbon capture, utilisation, and storage in line with the international 2050 Net Zero agenda. The widely known commercialised chemical fixation of CO2 into organic chemicals is [...] Read more.
Conversion of CO2 into organic chemicals offers a promising route for advancing the circularity of carbon capture, utilisation, and storage in line with the international 2050 Net Zero agenda. The widely known commercialised chemical fixation of CO2 into organic chemicals is the century-old Kolbe–Schmitt reaction, which carboxylates phenol (via sodium phenoxide) into salicylic acid. The carboxylation reaction is normally carried out between the gas–solid phases in a batch reactor. The mass and heat transfer limitations of such systems require rather long reaction times and a high pressure of CO2 and are often characterised by the low formation of undesirable side products. To address these drawbacks, a novel suspension-based carboxylation method has been designed and carried out in this present study, where sodium phenoxide is dispersed in toluene to react with CO2. Importantly, the addition of phenol played a critical role in promoting the stoichiometric conversion of phenoxide to salicylic acid. Under the optimal conditions of a phenol/phenoxide molar ratio of 2:1 in toluene, a reaction temperature of 225 °C, a CO2 pressure of 30 bar, a reaction time of 2 h, and stirring at 1000 rpm, an impressive salicylic acid molar yield of 92.68% has been achieved. The reaction mechanism behind this has been discussed. This development provides us with the potential to achieve a carboxylation reaction of phenoxide with CO2 more effectively in a continuous reactor. It can also facilitate the large-scale fixing of CO2 into hydroxy aromatic carboxylic acids, which can be used as green organic chemical feedstocks for making various products, including long-lived polymeric materials. Full article
(This article belongs to the Special Issue Recent Advances on Biomass Conversion and CO2 Valorization: Steeping towards a Circular Economy)
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15 pages, 5268 KiB  
Article
Investigating the Catalytic Influence of Boron on Ni-Co/Ca Catalysts for Improved Syngas Generation from Rice Straw Pyrolysis
by Jiaxiang Wang, Luqi Wang and Yueyao Li
Molecules 2024, 29(8), 1730; https://doi.org/10.3390/molecules29081730 - 11 Apr 2024
Viewed by 914
Abstract
A series of boron-promoted Ni-Co/Ca catalysts were synthesized by the sol–gel method to enhance syngas generation from biomass pyrolysis. The efficiency of these catalysts was evaluated during the pyrolysis of rice straw in a fixed-bed reactor, varying the Ni/Co ratio, boron addition, calcination [...] Read more.
A series of boron-promoted Ni-Co/Ca catalysts were synthesized by the sol–gel method to enhance syngas generation from biomass pyrolysis. The efficiency of these catalysts was evaluated during the pyrolysis of rice straw in a fixed-bed reactor, varying the Ni/Co ratio, boron addition, calcination temperature, and residence time. The catalysts underwent comprehensive characterization using X-ray diffraction (XRD), Brunauer–Emmett–Teller (BET) analysis, scanning electron microscopy (SEM), and hydrogen temperature-programmed reduction (H2-TPR). The results indicated that the Ni-Co/Ca catalysts yielded superior syngas compared to singular Ni or Co catalysts, suggesting a synergistic interplay between nickel and cobalt. The incorporation of 4% boron significantly decreased the particle size of the active metals, enhancing both the catalytic activity and stability. Optimal syngas production was achieved under the following conditions: a biomass-to-catalyst mass ratio of 2:1, a Ni-Co ratio of 1:1, a calcination temperature of 400 °C, a pyrolysis temperature of 800 °C, and a 20 min residence time. These conditions led to a syngas yield of 431.8 mL/g, a 131.28% increase over the non-catalytic pyrolysis yield of 188.6 mL/g. This study not only demonstrates the potential of Ni-Co/Ca catalysts in biomass pyrolysis for syngas production but also provides a foundation for future catalyst performance optimization. Full article
(This article belongs to the Special Issue Recent Advances on Biomass Conversion and CO2 Valorization: Steeping towards a Circular Economy)
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14 pages, 2813 KiB  
Article
Aerobic Oxidation of 5-Hydroxymethylfurfural (HMF) in Aqueous Medium over Fe-Doped-Poly(heptazine imide) Photocatalysts: Unveiling the Bad Role of Hydroxyl Radical Generation on the Catalytic Performance
by José B. G. Filho, Ingrid F. Silva, Mamdouh Alafandi and Jabor Rabeah
Molecules 2023, 28(24), 8077; https://doi.org/10.3390/molecules28248077 - 14 Dec 2023
Cited by 1 | Viewed by 1618
Abstract
5-hydroxymethylfurfural (HMF) oxidation in aqueous media using visible photocatalysis is a green and sustainable route for the valorization of lignocellulosic biomass derivatives. Several semiconductors have already been applied for this purpose; however, the use of Poly(heptazine imides), which has high crystallinity and a [...] Read more.
5-hydroxymethylfurfural (HMF) oxidation in aqueous media using visible photocatalysis is a green and sustainable route for the valorization of lignocellulosic biomass derivatives. Several semiconductors have already been applied for this purpose; however, the use of Poly(heptazine imides), which has high crystallinity and a special cation exchange property that allows the replacement of the cation held between the layers of C3N4 structure by transition metal ions (TM), remains scarce. In this study, PHI(Na) was synthesized using a melamine/NaCl method and used as precursor to prepare metal (Fe, Co, Ni, or Cu)-doped PHI catalysts. The catalysts were tested for selective oxidation of HMF to 2,5-diformylfuran (DFF) in water and O2 atmosphere under blue LED radiation. The catalytic results revealed that the 0.1 wt% PHI(Fe) catalyst is the most efficient photocatalyst while higher Fe loading (1 and 2 wt%) favors the formation of Fe3+ clusters, which are responsible for the drop in HMF oxidation. Moreover, the 0.1 wt% PHI(Fe) photocatalyst has strong oxidative power due to its efficiency in H2O2 production, thus boosting the generation of nonselective hydroxyl radicals (●OH) via different pathways that can destroy HMF. We found that using 50 mM, the highest DFF production rate (393 μmol·h−1·g−1) was obtained in an aqueous medium under visible light radiation. Full article
(This article belongs to the Special Issue Recent Advances on Biomass Conversion and CO2 Valorization: Steeping towards a Circular Economy)
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14 pages, 1579 KiB  
Article
Coffee Pulp Gasification for Syngas Obtention and Methane Production Simulation Using Ni Catalysts Supported on Al2O3 and ZrO2 in a Packed Bed Reactor
by Carlos Esteban Aristizábal-Alzate, Ana Belén Dongil and Manuel Romero-Sáez
Molecules 2023, 28(20), 7026; https://doi.org/10.3390/molecules28207026 - 11 Oct 2023
Viewed by 1266
Abstract
The methanation of CO2 is of great interest in power-to-gas systems and contributes to the mitigation of climate change through carbon dioxide capture and the subsequent production of high-added-value products. This study investigated CO2 methanation with three Ni catalysts supported on [...] Read more.
The methanation of CO2 is of great interest in power-to-gas systems and contributes to the mitigation of climate change through carbon dioxide capture and the subsequent production of high-added-value products. This study investigated CO2 methanation with three Ni catalysts supported on Al2O3 and ZrO2, which were simulated using a mathematical model of a packed bed reactor designed based on their chemical kinetics reported in the literature. The simulated reactive system was fed with syngas obtained from residual coffee pulp obtained after a solvent phytochemical extraction process under several gasification conditions. The results reflect a high degree of influence of the catalyst support, preparation method, and syngas composition on CO2 and H2 conversions and CH4 selectivity. For all the syngas compositions, the Ni/ZrO2 catalysts showed the best values for CO2 conversion and H2 conversion for the Ni/Al2O3 catalyst except in gasification at 700 °C and using the Ni/ZrO2p catalyst. Full article
(This article belongs to the Special Issue Recent Advances on Biomass Conversion and CO2 Valorization: Steeping towards a Circular Economy)
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22 pages, 3055 KiB  
Article
Renewable Hydrogen Production by Aqueous Phase Reforming of Pure/Refined Crude Glycerol over Ni/Al-Ca Catalysts
by Raquel Raso, Eduardo Abad, Lucía García, Joaquín Ruiz, Miriam Oliva and Jesús Arauzo
Molecules 2023, 28(18), 6695; https://doi.org/10.3390/molecules28186695 - 19 Sep 2023
Cited by 3 | Viewed by 1676
Abstract
Renewable hydrogen production by aqueous phase reforming (APR) over Ni/Al-Ca catalysts was studied using pure or refined crude glycerol as feedstock. The APR was carried out in a fixed bed reactor at 238 °C, 37 absolute bar for 3 h, using a solution [...] Read more.
Renewable hydrogen production by aqueous phase reforming (APR) over Ni/Al-Ca catalysts was studied using pure or refined crude glycerol as feedstock. The APR was carried out in a fixed bed reactor at 238 °C, 37 absolute bar for 3 h, using a solution of 5 wt.% of glycerol, obtaining gas and liquid products. The catalysts were prepared by the co-precipitation method, calcined at different temperatures, and characterized before and after their use by several techniques (XRD, ICP-OES, H2-TPR, NH3-TPD, CO2-TPD, FESEM, and N2-physisorption). Increasing the calcination temperature and adding Ca decreased the surface area from 256 to 188 m2/g, and its value after the APR changed depending on the feedstock used. The properties of the acid and basic sites of the catalysts influenced the H2 yield also depending on the feed used. The Ni crystallite was between 6 and 20 nm. In general, the incorporation of Ca into Ni-based catalysts and the increase of the calcination temperature improved H2 production, obtaining 188 mg H2/mol C fed during the APR of refined crude glycerol over Ni/AlCa-675 catalyst, which was calcined at 675 °C. This is a promising result from the point of view of enhancing the economic viability of biodiesel. Full article
(This article belongs to the Special Issue Recent Advances on Biomass Conversion and CO2 Valorization: Steeping towards a Circular Economy)
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