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17 pages, 1924 KiB

Open AccessArticle

Conversion of Furfural as a Bio-Oil Model Compound over Calcium-Based Materials as Sacrificial Low-Cost Catalysts for Bio-Oil Upgrading

by Moritz Böhme, Peter A. Jensen, Martin Høj, Brian B. Hansen, Magnus Z. Stummann and Anker D. Jensen

Catalysts 2025, 15(6), 554; https://doi.org/10.3390/catal15060554 - 3 Jun 2025

Viewed by 608

Abstract

The stabilization and upgrading of biomass and waste-derived pyrolysis oils requires development of reliable, active and low-cost upgrading catalysts. Basic natural materials can act as such catalysts and convert reactive oxygenates present in biomass pyrolysis oils. The conversion of furfural as a model [...] Read more.

The stabilization and upgrading of biomass and waste-derived pyrolysis oils requires development of reliable, active and low-cost upgrading catalysts. Basic natural materials can act as such catalysts and convert reactive oxygenates present in biomass pyrolysis oils. The conversion of furfural as a model compound has been conducted in an autoclave reactor at 200 °C to 300 °C using different calcium-based materials. CaCO₃, Ca(OH)₂, CaO, cement raw meal (CRM) and calcined cement raw meal (cCRM) were screened for their catalytic activity and characterized using X-ray powder diffraction (XRD) and X-ray fluorescence (XRF), nitrogen physisorption, carbon dioxide temperature programmed desorption (CO₂-TPD) and thermogravimetric analysis (TGA). CaCO₃ and CRM had low basicity and showed no catalytic activity at 200 to 300 °C. Notably, 90% conversion of furfural was achieved at 200 °C using Ca(OH)₂ with products being mostly furfural di- and trimers. For the basic CaO and cCRM, a temperature of 250 °C or above caused rapid polymerization of furfural. The proposed mechanism follows the Cannizzaro reaction of furfural, catalyzed by basic sites, polymerization of furfuryl alcohol, decarboxylation of furoic acid and decarbonylation of furfural, releasing CO, CO₂ and H₂O. Calcined cement raw meal showed the most promise for application as low-cost, sacrificial, basic catalyst. Full article

(This article belongs to the Topic Advanced Bioenergy and Biofuel Technologies)

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16 pages, 3553 KiB

Open AccessArticle

Sulfur Analogs of the Core Formose Cycle: A Free Energy Map

by Jeremy Kua, Maria T. Peña, Samantha N. Cotter and John Leca

Life 2025, 15(1), 1; https://doi.org/10.3390/life15010001 - 24 Dec 2024

Cited by 1 | Viewed by 861

Abstract

Using computational methods, we examine if the presence of H₂S can tame the unruly formose reaction by generating a free energy map of the reaction thermodynamics and kinetics of sulfur analogs within the core cycle. With mercaptoaldehyde as the linchpin C [...] Read more.

Using computational methods, we examine if the presence of H₂S can tame the unruly formose reaction by generating a free energy map of the reaction thermodynamics and kinetics of sulfur analogs within the core cycle. With mercaptoaldehyde as the linchpin C₂ species, and feeding the cycle with CH₂O, selected aldol additions and enolizations are kinetically more favorable. Thione formation is thermodynamically less favored compared to aldehydes and ketones, but all these species can be connected by enolization reactions. In some sulfur analogs, the retroaldol transformation of a C4 species back into linchpin species is thermodynamically favorable, and we have found one route incorporating where incorporating sulfur selects for a specific pathway over others. However, as CH₂O diminishes, the aldol addition of larger species is less favorable for the sulfur analogs. Our results also suggest that competing Cannizzaro side reactions are kinetically less favored and thermodynamically disfavored when H₂S is abundant. Full article

(This article belongs to the Special Issue Feature Papers in Origins of Life 2024)

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18 pages, 1864 KiB

Open AccessArticle

Exploring the Core Formose Cycle: Catalysis and Competition

by Jeremy Kua and L. Philip Tripoli

Life 2024, 14(8), 933; https://doi.org/10.3390/life14080933 - 25 Jul 2024

Cited by 3 | Viewed by 1926

Abstract

The core autocatalytic cycle of the formose reaction may be enhanced or eroded by the presence of simple molecules at life’s origin. Utilizing quantum chemistry, we calculate the thermodynamics and kinetics of reactions both within the core cycle and those that deplete the [...] Read more.

The core autocatalytic cycle of the formose reaction may be enhanced or eroded by the presence of simple molecules at life’s origin. Utilizing quantum chemistry, we calculate the thermodynamics and kinetics of reactions both within the core cycle and those that deplete the reactants and intermediates, such as the Cannizzaro reaction. We find that via disproportionation of aldehydes into carboxylic acids and alcohols, the Cannizzaro reaction furnishes simple catalysts for a variety of reactions. We also find that ammonia can catalyze both in-cycle and Cannizzaro reactions while hydrogen sulfide does not; both, however, play a role in sequestering reactants and intermediates in the web of potential reactions. Full article

(This article belongs to the Special Issue Feature Papers in Origins of Life 2024)

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12 pages, 1684 KiB

Open AccessArticle

Reaction Mechanisms and Production of Hydrogen and Acetic Acid from Aqueous Ethanol Using a Rn-Sn/TiO₂ Catalyst in a Continuous Flow Reactor

by Takashi Nomura, Yuanyuan Zhao, Eiji Minami and Haruo Kawamoto

Catalysts 2024, 14(4), 249; https://doi.org/10.3390/catal14040249 - 9 Apr 2024

Viewed by 2071

Abstract

The catalytic reforming of bioethanol can produce green hydrogen (H₂) and acetic acid (AcOH). In the present study, the conversion of aqueous ethanol (EtOH) over 4 wt%Ru-4 wt%Sn/TiO₂ in a flow reactor was investigated at different temperatures at 0.1 MPa [...] Read more.

The catalytic reforming of bioethanol can produce green hydrogen (H₂) and acetic acid (AcOH). In the present study, the conversion of aqueous ethanol (EtOH) over 4 wt%Ru-4 wt%Sn/TiO₂ in a flow reactor was investigated at different temperatures at 0.1 MPa or at various pressures at 260 °C. The ethanol conversion was rather slow in liquid water, while the reactivity increased significantly when water was evaporated. Under gas-phase conditions at 0.1 MPa, the conversion rate increased with increasing reaction temperature, but the AcOH yield and H₂ purity decreased due to by-production of CH₄, CO, and CO₂. The CH₄ and CO generated by fragmentation of acetaldehyde (AA), an intermediate, were suppressed by increasing reaction pressure, although the formation of CH₄ and CO₂ generated from AcOH was pressure independent. Thus, the highest-pressure conditions in steam at a given reaction temperature are preferred for the production of pure H₂. The initial step, EtOH → AA, was the rate-determining reaction, and the model experiments using AA as a substrate showed that the Cannizzaro reaction of two AA molecules to form EtOH and AcOH occurred preferentially. This oxidation system was confirmed to be effective at EtOH concentrations of up to 500 g/L in water. Full article

(This article belongs to the Special Issue Catalytical Methods for the Production of Fine and Bulk Chemicals and Biomaterials from Biomass)

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13 pages, 4968 KiB

Open AccessArticle

Serpentinization-Associated Mineral Catalysis of the Protometabolic Formose System

by Arthur Omran, Asbell Gonzalez, Cesar Menor-Salvan, Michael Gaylor, Jing Wang, Jerzy Leszczynski and Tian Feng

Life 2023, 13(6), 1297; https://doi.org/10.3390/life13061297 - 31 May 2023

Cited by 4 | Viewed by 3510

Abstract

The formose reaction is a plausible prebiotic chemistry, famed for its production of sugars. In this work, we demonstrate that the Cannizzaro process is the dominant process in the formose reaction under many different conditions, thus necessitating a catalyst for the formose reaction [...] Read more.

The formose reaction is a plausible prebiotic chemistry, famed for its production of sugars. In this work, we demonstrate that the Cannizzaro process is the dominant process in the formose reaction under many different conditions, thus necessitating a catalyst for the formose reaction under various environmental circumstances. The investigated formose reactions produce primarily organic acids associated with metabolism, a protometabolic system, and yield very little sugar left over. This is due to many of the acids forming from the degradation and Cannizaro reactions of many of the sugars produced during the formose reaction. We also show the heterogeneous Lewis-acid-based catalysis of the formose reaction by mineral systems associated with serpentinization. The minerals that showed catalytic activity include olivine, serpentinite, and calcium, and magnesium minerals including dolomite, calcite, and our Ca/Mg-chemical gardens. In addition, computational studies were performed for the first step of the formose reaction to investigate the reaction of formaldehyde, to either form methanol and formic acid under a Cannizzaro reaction or to react to form glycolaldehyde. Here, we postulate that serpentinization is therefore the startup process necessary to kick off a simple proto metabolic system—the formose protometabolic system. Full article

(This article belongs to the Special Issue Origin of Life in Chemically Complex Messy Environments: 2nd Edition)

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13 pages, 2299 KiB

Open AccessCommunication

Oxidation of Aldehydes Used as Food Additives by Peroxynitrite

by Clara I. Alcolado, Luis Garcia-Rio, Juan C. Mejuto, Inmaculada Moreno, Francisco J. Poblete and Juan Tejeda

Antioxidants 2023, 12(3), 743; https://doi.org/10.3390/antiox12030743 - 17 Mar 2023

Cited by 11 | Viewed by 5245

Abstract

Benzaldehyde and its derivatives are used as food supplements. These substances can be used mainly as flavorings or as antioxidants. Besides, peroxynitrite, an oxidizing agent, could be formed in canned food. Both species could react between them. The present article has focused on [...] Read more.

Benzaldehyde and its derivatives are used as food supplements. These substances can be used mainly as flavorings or as antioxidants. Besides, peroxynitrite, an oxidizing agent, could be formed in canned food. Both species could react between them. The present article has focused on the kinetic study of the oxidation of aldehydes by peroxynitrite. A reaction mechanism that justifies all the experimental results is proposed. This mechanism, in acidic media, passes through three competitive pathways: (a) a radical attack that produces benzoic acid. (b) peracid oxidation, and (c) a nucleophilic attack of peroxynitrous acid over aldehyde to form an intermediate, X, that produces benzoic acid, or, through a Cannizzaro-type reaction, benzoic acid and benzyl alcohol. All rate constants involved in the third pathway (c) have been calculated. These results have never been described in the literature in acid media. A pH effect was analyzed. Full article

(This article belongs to the Section Aberrant Oxidation of Biomolecules)

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22 pages, 1235 KiB

Open AccessReview

Smart Food Packaging Designed by Nanotechnological and Drug Delivery Approaches

by Ludmila Motelica, Denisa Ficai, Ovidiu Cristian Oprea, Anton Ficai and Ecaterina Andronescu

Coatings 2020, 10(9), 806; https://doi.org/10.3390/coatings10090806 - 20 Aug 2020

Cited by 53 | Viewed by 7777

Abstract

This paper offers a general view of the solutions that are able to confer bioactivity to the packaging materials, especially antimicrobial and antioxidant activity. These properties can be induced by the nature of the polymers blend or due to the addition of ternary [...] Read more.

This paper offers a general view of the solutions that are able to confer bioactivity to the packaging materials, especially antimicrobial and antioxidant activity. These properties can be induced by the nature of the polymers blend or due to the addition of ternary components from natural agents (essential oils or other extracts) to synthetic organic and inorganic agents, including nanoparticles with a broad antimicrobial activity such as metals (e.g., Ag, Au, Cu) or metal oxide (e.g., TiO₂, ZnO) nanoparticles, and even bacterial cells such as probiotics. Many times, these components are synergistically used, each of them assuring a specific role or potentiating the role of the other components. The antimicrobial activity can be induced due to the applied coatings or due to the whole bulk material. Along with an increasing food stability which means a longer shelf-life some smart packaging can be exploited in order to highlight the freshness of the food. These act as a sensor (usually pH sensitive but also other mechanisms can be exploited such as aggregation/agglomeration of AuNPs leading to color change or even aldehyde-specific reactions such as the Cannizzaro reaction), and thus, consumers can be confident about the freshness of the food, especially perishable food such as seafood or fish. Full article

(This article belongs to the Special Issue Natural Materials in Functional Coatings)

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10 pages, 1268 KiB

Open AccessArticle

The Messy Alkaline Formose Reaction and Its Link to Metabolism

by Arthur Omran, Cesar Menor-Salvan, Greg Springsteen and Matthew Pasek

Life 2020, 10(8), 125; https://doi.org/10.3390/life10080125 - 28 Jul 2020

Cited by 50 | Viewed by 7908

Abstract

Sugars are essential for the formation of genetic elements such as RNA and as an energy/food source. Thus, the formose reaction, which autocatalytically generates a multitude of sugars from formaldehyde, has been viewed as a potentially important prebiotic source of biomolecules at the [...] Read more.

Sugars are essential for the formation of genetic elements such as RNA and as an energy/food source. Thus, the formose reaction, which autocatalytically generates a multitude of sugars from formaldehyde, has been viewed as a potentially important prebiotic source of biomolecules at the origins of life. When analyzing our formose solutions we find that many of the chemical species are simple carboxylic acids, including α-hydroxy acids, associated with metabolism. In this work we posit that the study of the formose reaction, under alkaline conditions and moderate hydrothermal temperatures, should not be solely focused on sugars for genetic materials, but should focus on the origins of metabolism (via metabolic molecules) as well. Full article

(This article belongs to the Special Issue From Messy Chemistry to the Origin of Life)

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17 pages, 8872 KiB

Open AccessArticle

Investigating the Mechanism behind ‘Ant Nest’ Corrosion on Copper Tube

by Riky Stepanus Situmorang and Hideki Kawai

Materials 2018, 11(4), 533; https://doi.org/10.3390/ma11040533 - 30 Mar 2018

Cited by 18 | Viewed by 7053

Abstract

A research investigation of “ant nest” corrosion (ANC) on copper tube was conducted in terms of the variables of the corrosion potential and pH value in 10³ ppm copper formate solution over 20 days. The paper presents the surface and cross-sectional observations [...] Read more.

A research investigation of “ant nest” corrosion (ANC) on copper tube was conducted in terms of the variables of the corrosion potential and pH value in 10³ ppm copper formate solution over 20 days. The paper presents the surface and cross-sectional observations and examines Cu₂O and H₂O as the stable chemical species produced. A Cannizzaro reaction as a disproportionation reaction from formic acid and a comproportionation reaction from the metallic copper tube and copper formate solution critically influenced the ANC mechanism. The paper also categorizes the ANC attack as a rapid reaction system from the electrochemical point of view by using a polarization resistance curve. Full article

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