Editorial

2 pages, 159 KiB

Open AccessEditorial

Solid Catalysts for the Upgrading of Renewable Sources

by Federica Zaccheria and Nicoletta Ravasio

Catalysts 2019, 9(1), 88; https://doi.org/10.3390/catal9010088 - 15 Jan 2019

Cited by 3 | Viewed by 2620

The use of renewable resources as raw materials for the chemical industry is mandatory in the transition roadmap toward the Bioeconomy [...] Full article

(This article belongs to the Special Issue Solid Catalysts for the Upgrading of Renewable Sources)

Research

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12 pages, 3429 KiB

Open AccessArticle

Pyrolyzing Renewable Sugar and Taurine on the Surface of Multi-Walled Carbon Nanotubes as Heterogeneous Catalysts for Hydroxymethylfurfural Production

by Huiping Ji, Jie Fu and Tianfu Wang

Catalysts 2018, 8(11), 517; https://doi.org/10.3390/catal8110517 - 05 Nov 2018

Cited by 5 | Viewed by 2778

Abstract

Conversion of biorenewable feedstocks into transportation fuels or chemicals likely necessitates the development of novel heterogeneous catalysts with good hydrothermal stability, due to the nature of highly oxygenated biomass compounds and the prevalence of water as a processing solvent. The use of carbon-based [...] Read more.

Conversion of biorenewable feedstocks into transportation fuels or chemicals likely necessitates the development of novel heterogeneous catalysts with good hydrothermal stability, due to the nature of highly oxygenated biomass compounds and the prevalence of water as a processing solvent. The use of carbon-based materials, derived from sugars as catalyst precursors, can achieve hydrothermal stability while simultaneously realizing the goal of sustainability. In this work, the simultaneous pyrolysis of glucose and taurine in the presence of multi-walled carbon nanotubes (MWCNTs), to obtain versatile solid acids, has been demonstrated. Structural and textural properties of the catalysts have been characterized by TEM, TGA, and XPS. Additionally, solid state nuclear magnetic resonance (ssNMR) spectroscopy has been exploited to elucidate the chemical nature of carbon species deposited on the surface of MWCNTs. Al(OTf)₃, a model Lewis acidic metal salt, has been successfully supported on sulfonic groups tethered to MWCNTs. This catalyst has been tested for C₆ sugar dehydration for the production of HMF in a tetrahydrofuran (THF)/water solvent system with good recyclability. Full article

(This article belongs to the Special Issue Solid Catalysts for the Upgrading of Renewable Sources)

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16 pages, 2901 KiB

Open AccessArticle

Effect of Calcination Atmosphere and Temperature on the Hydrogenolysis Activity and Selectivity of Copper-Zinc Catalysts

by Oleg Kikhtyanin, Violetta Pospelova, Jaroslav Aubrecht, Miloslav Lhotka and David Kubička

Catalysts 2018, 8(10), 446; https://doi.org/10.3390/catal8100446 - 11 Oct 2018

Cited by 19 | Viewed by 4412

Abstract

A series of CuZn catalysts with a Cu/Zn ratio of 1.6 was prepared by the calcination of a single precursor, CuZn-P consisting of an equimolar mixture of aurichalcite and zincian malachite, in three different calcination atmospheres (air, nitrogen, and hydrogen) at three temperatures [...] Read more.

A series of CuZn catalysts with a Cu/Zn ratio of 1.6 was prepared by the calcination of a single precursor, CuZn-P consisting of an equimolar mixture of aurichalcite and zincian malachite, in three different calcination atmospheres (air, nitrogen, and hydrogen) at three temperatures (220, 350, and 500 °C). All catalysts were characterized by XRD and N₂-physisorption to assess their phase composition, crystallite sizes and textural properties and tested in dimethyl adipate (DMA) hydrogenolysis in a batch reactor at 220 °C and 10 MPa H₂. The XRD examination of these catalysts proved that both parameters, calcination temperature and atmosphere, affected the resulting phase composition of the catalysts as well as their crystallite sizes. In an oxidizing atmosphere, CuO and ZnO in intimate contact prevailed whereas in inert or reducing atmosphere both oxides were accompanied by Cu₂O and Cu. The crystallite size of Cu₂O and Cu was larger than the size of CuO and ZnO thus indicating a less intimate contact between the Cu-phases and ZnO in catalysts calcined in nitrogen and hydrogen. Catalysts prepared by calcination at 220 °C and CuZn catalyst calcined in the air at 350 °C significantly outperformed the other catalysts in DMA hydrogenolysis with a 59–78% conversion due to the small crystallite size and intimate contact between the CuO and ZnO phases prior to catalyst reduction. Despite the low DMA conversion (<30%), transesterification products were the main reaction products with overall selectivities of >80% over the catalysts calcined in nitrogen or hydrogen at least at 350 °C. The obvious change in the preferred reaction pathway because of the atmosphere calcination and temperature shows that there are different active sites responsible for hydrogenolysis and transesterification and that their relative distribution has changed. Full article

(This article belongs to the Special Issue Solid Catalysts for the Upgrading of Renewable Sources)

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10 pages, 3491 KiB

Open AccessFeature PaperArticle

Brønsted and Lewis Solid Acid Catalysts in the Valorization of Citronellal

by Federica Zaccheria, Federica Santoro, Elvina Dhiaul Iftitah and Nicoletta Ravasio

Catalysts 2018, 8(10), 410; https://doi.org/10.3390/catal8100410 - 22 Sep 2018

Cited by 17 | Viewed by 4503

Abstract

Terpenes are valuable starting materials for the synthesis of molecules that are of interest to the flavor, fragrance, and pharmaceutical industries. However, most processes involve the use of mineral acids or homogeneous Lewis acid catalysts. Here, we report results obtained in the liquid-phase [...] Read more.

Terpenes are valuable starting materials for the synthesis of molecules that are of interest to the flavor, fragrance, and pharmaceutical industries. However, most processes involve the use of mineral acids or homogeneous Lewis acid catalysts. Here, we report results obtained in the liquid-phase reaction of citronellal with anilines under heterogeneous catalysis conditions to give tricyclic compounds with interesting pharmacological activity. The terpenic aldehyde could be converted into octahydroacridines with a 92% yield through an intramolecular imino Diels–Alder reaction of the imine initially formed in the presence of an acidic clay such as Montmorillonite KSF. Selectivity to the desired product strongly depended on the acid sites distribution, with Brønsted acids favoring selectivity to octahydroacridine and formation of the cis isomer. Pure Lewis acids such as silica–alumina with a very low amount of alumina gave excellent results with electron-rich anilines like toluidine and p-anisidine. This protocol can be applied starting directly from essential oils such as kaffir lime oil, which has a high citronellal content. Full article

(This article belongs to the Special Issue Solid Catalysts for the Upgrading of Renewable Sources)

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14 pages, 5280 KiB

Open AccessArticle

Ru-(Mn-M)O_X Solid Base Catalysts for the Upgrading of Xylitol to Glycols in Water

by Maxime Rivière, Noémie Perret, Damien Delcroix, Amandine Cabiac, Catherine Pinel and Michèle Besson

Catalysts 2018, 8(8), 331; https://doi.org/10.3390/catal8080331 - 14 Aug 2018

Cited by 9 | Viewed by 4523

Abstract

A series of Ru-(Mn-M)O_X catalysts (M: Al, Ti, Zr, Zn) prepared by co-precipitation were investigated in the hydrogenolysis of xylitol in water to ethylene glycol, propylene glycol and glycerol at 200 °C and 60 bar of H₂. The catalyst promoted [...] Read more.

A series of Ru-(Mn-M)O_X catalysts (M: Al, Ti, Zr, Zn) prepared by co-precipitation were investigated in the hydrogenolysis of xylitol in water to ethylene glycol, propylene glycol and glycerol at 200 °C and 60 bar of H₂. The catalyst promoted with Al, Ru-(Mn-Al)O_X, showed superior activity (57 h⁻¹) and a high global selectivity to glycols and glycerol of 58% at 80% xylitol conversion. In comparison, the catalyst prepared by loading Ru on (Mn-Al)O_X, Ru/(Mn-Al)O_X was more active (111 h⁻¹) but less selective (37%) than Ru-(Mn-Al)O_X. Characterization of these catalysts by XRD, BET, CO₂-TPD, NH₃-TPD and TEM showed that Ru/(Mn-Al)O_X contained highly dispersed and uniformly distributed Ru particles and fewer basic sites, which favored decarbonylation, epimerization and cascade decarbonylation reactions instead of retro-aldol reactions producing glycols. The hydrothermal stability of Ru-(Mn-Al)O_X was improved by decreasing the xylitol/catalyst ratio, which decreased the formation of carboxylic acids and enabled recycling of the catalyst, with a very low deactivation. Full article

(This article belongs to the Special Issue Solid Catalysts for the Upgrading of Renewable Sources)

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14 pages, 5941 KiB

Open AccessArticle

Acid–Base Bifunctional Hf Nanohybrids Enable High Selectivity in the Catalytic Conversion of Ethyl Levulinate to γ-Valerolactone

by Weibo Wu, Yan Li, Hu Li, Wenfeng Zhao and Song Yang

Catalysts 2018, 8(7), 264; https://doi.org/10.3390/catal8070264 - 29 Jun 2018

Cited by 22 | Viewed by 4645

Abstract

The catalytic upgrading of bio-based platform molecules is a promising approach for biomass valorization. However, most solid catalysts are not thermally or chemically stable, and are difficult to prepare. In this study, a stable organic phosphonate–hafnium solid catalyst (PPOA–Hf) was synthesized, and acid–base [...] Read more.

The catalytic upgrading of bio-based platform molecules is a promising approach for biomass valorization. However, most solid catalysts are not thermally or chemically stable, and are difficult to prepare. In this study, a stable organic phosphonate–hafnium solid catalyst (PPOA–Hf) was synthesized, and acid–base bifunctional sites were found to play a cooperative role in the cascade transfer hydrogenation and cyclization of ethyl levulinate (EL) to γ-valerolactone (GVL). Under relatively mild reaction conditions of 160 °C for 6 h, EL was completely converted to GVL with a good yield of 85%. The apparent activation energy was calculated to be 53 kJ/mol, which was lower than other solid catalysts for the same reaction. In addition, the PPOA-Hf solid catalyst did not significantly decrease its activity after five recycles, and no evident leaching of Hf was observed, indicating its high stability and potential practical application. Full article

(This article belongs to the Special Issue Solid Catalysts for the Upgrading of Renewable Sources)

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Review

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31 pages, 5907 KiB

Open AccessEditor’s ChoiceReview

Catalytic Transfer Hydrogenolysis Reactions for Lignin Valorization to Fuels and Chemicals

by Antigoni Margellou and Konstantinos S. Triantafyllidis

Catalysts 2019, 9(1), 43; https://doi.org/10.3390/catal9010043 - 04 Jan 2019

Cited by 47 | Viewed by 8166

Abstract

Lignocellulosic biomass is an abundant renewable source of chemicals and fuels. Lignin, one of biomass main structural components being widely available as by-product in the pulp and paper industry and in the process of second generation bioethanol, can provide phenolic and aromatic compounds [...] Read more.

Lignocellulosic biomass is an abundant renewable source of chemicals and fuels. Lignin, one of biomass main structural components being widely available as by-product in the pulp and paper industry and in the process of second generation bioethanol, can provide phenolic and aromatic compounds that can be utilized for the manufacture of a wide variety of polymers, fuels, and other high added value products. The effective depolymerisation of lignin into its primary building blocks remains a challenge with regard to conversion degree and monomers selectivity and stability. This review article focuses on the state of the art in the liquid phase reductive depolymerisation of lignin under relatively mild conditions via catalytic hydrogenolysis/hydrogenation reactions, discussing the effect of lignin type/origin, hydrogen donor solvents, and related transfer hydrogenation or reforming pathways, catalysts, and reaction conditions. Full article

(This article belongs to the Special Issue Solid Catalysts for the Upgrading of Renewable Sources)

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39 pages, 4292 KiB

Open AccessReview

Metal–Organic Frameworks-Based Catalysts for Biomass Processing

by Vera I. Isaeva, Oleg M. Nefedov and Leonid M. Kustov

Catalysts 2018, 8(9), 368; https://doi.org/10.3390/catal8090368 - 31 Aug 2018

Cited by 40 | Viewed by 8321

Abstract

Currently, metal–organic frame works (MOFs) as novel hybrid nanoporous materials are a top research interest, including endeavors in heterogeneous catalysis. MOF materials are promising heterogeneous catalytic systems due to their unique characteristics, such as a highly ordered structure, a record high surface area [...] Read more.

Currently, metal–organic frame works (MOFs) as novel hybrid nanoporous materials are a top research interest, including endeavors in heterogeneous catalysis. MOF materials are promising heterogeneous catalytic systems due to their unique characteristics, such as a highly ordered structure, a record high surface area and a compositional diversity, which can be precisely tailored. Very recently, these metal-organic matrices have been proven as promising catalysts for biomass conversion into value-added products. The relevant publications show that the structure of MOFs can contribute essentially to the advanced catalytic performance in processes of biomass refining. This review aims at the consideration of the different ways for the rational design of MOF catalysts for biomass processing. The particular characteristics and peculiarities of the behavior of different MOF based catalytic systems including hybrid nanomaterials and composites will be also discussed by illustrating their outstanding performance with appropriate examples relevant to biomass catalytic processing. Full article

(This article belongs to the Special Issue Solid Catalysts for the Upgrading of Renewable Sources)

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36 pages, 17032 KiB

Open AccessReview

Valorization of Biomass Derived Terpene Compounds by Catalytic Amination

by Irina L. Simakova, Andrey V. Simakov and Dmitry Yu. Murzin

Catalysts 2018, 8(9), 365; https://doi.org/10.3390/catal8090365 - 29 Aug 2018

Cited by 13 | Viewed by 6604

Abstract

This review fills an apparent gap existing in the literature by providing an overview of the readily available terpenes and existing catalytic protocols for preparation of terpene-derived amines. To address the role of solid catalysts in amination of terpenes the same reactions with [...] Read more.

This review fills an apparent gap existing in the literature by providing an overview of the readily available terpenes and existing catalytic protocols for preparation of terpene-derived amines. To address the role of solid catalysts in amination of terpenes the same reactions with homogeneous counterparts are also discussed. Such catalysts can be considered as a benchmark, which solid catalysts should match. Although catalytic systems based on transition metal complexes have been developed for synthesis of amines to a larger extent, there is an apparent need to reduce the production costs. Subsequently, homogenous systems based on cheaper metals operating by nucleophilic substitution (e.g., Ni, Co, Cu, Fe) with a possibility of easy recycling, as well as metal nanoparticles (e.g., Pd, Au) supported on amphoteric oxides should be developed. These catalysts will allow synthesis of amine derivatives of terpenes which have a broad range of applications as specialty chemicals (e.g., pesticides, surfactants, etc.) and pharmaceuticals. The review will be useful in selection and design of appropriate solid materials with tailored properties as efficient catalysts for amination of terpenes. Full article

(This article belongs to the Special Issue Solid Catalysts for the Upgrading of Renewable Sources)

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35 pages, 4662 KiB

Open AccessReview

Preparation and Application of Biochar-Based Catalysts for Biofuel Production

by Feng Cheng and Xiuwei Li

Catalysts 2018, 8(9), 346; https://doi.org/10.3390/catal8090346 - 24 Aug 2018

Cited by 168 | Viewed by 12007

Abstract

Firstly, this paper reviews two main methods for biochar synthesis, namely conventional pyrolysis and hydrothermal carbonization (HTC). The related processes are described, and the influences of biomass nature and reaction conditions, especially temperature, are discussed. Compared to pyrolysis, HTC has advantages for processing [...] Read more.

Firstly, this paper reviews two main methods for biochar synthesis, namely conventional pyrolysis and hydrothermal carbonization (HTC). The related processes are described, and the influences of biomass nature and reaction conditions, especially temperature, are discussed. Compared to pyrolysis, HTC has advantages for processing high-moisture biomass and producing spherical biochar particles. Secondly, typical features of biochar in comparison with other carbonaceous materials are summarized. They refer to the presence of inorganics, surface functional groups, and local crystalline structures made up of highly conjugated aromatic sheets. Thirdly, various strategies for biochar modification are illustrated. They include activation, surface functionalization, in situ heteroatom doping, and the formation of composites with other materials. An appropriate modification is necessary for biochar used as a catalyst. Fourthly, the applications of biochar-based catalysts in three important processes of biofuel production are reviewed. Sulfonated biochar shows good catalytic performance for biomass hydrolysis and biodiesel production. Biodiesel production can also be catalyzed by biochar-derived or -supported solid-alkali catalysts. Biochar alone and biochar-supported metals are potential catalysts for tar reduction during or after biomass gasification. Lastly, the merits of biochar-based catalysts are summarized. Biochar-based catalysts have great developmental prospects. Future work needs to focus on the study of mechanism and process design. Full article

(This article belongs to the Special Issue Solid Catalysts for the Upgrading of Renewable Sources)

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