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3 pages, 182 KiB

Open AccessEditorial

Catalytic Transformation of Renewables (Olefin, Bio-Sourced, et al.)

by Nikolaos Dimitratos, Stefania Albonetti and Tommaso Tabanelli

Catalysts 2021, 11(3), 364; https://doi.org/10.3390/catal11030364 - 10 Mar 2021

Cited by 1 | Viewed by 1473

Abstract

The objective of this Special Issue is to provide new diverse contributions that can demonstrate recent applications in biomass transformation using heterogeneous catalysts [...] Full article

(This article belongs to the Special Issue Catalytic Transformation of Renewables (Olefin, Bio-sourced, et. al))

Research

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20 pages, 4735 KiB

Open AccessFeature PaperArticle

Oxidative Condensation of Furfural with Ethanol Using Pd-Based Catalysts: Influence of the Support

by Juan Antonio Cecilia, Carmen Pilar Jiménez-Gómez, Virginia Torres-Bujalance, Cristina García-Sancho, Ramón Moreno-Tost and Pedro Maireles-Torres

Catalysts 2020, 10(11), 1309; https://doi.org/10.3390/catal10111309 - 12 Nov 2020

Cited by 7 | Viewed by 2193

Abstract

PdO nanoparticles were deposited on several supports (β-zeolite, Al₂O₃, Fe₂O₃, MgO, and SiO₂), which displayed different crystallinity, textural properties, and amount of acid and basic sites. These catalysts were characterized by X-ray diffraction [...] Read more.

PdO nanoparticles were deposited on several supports (β-zeolite, Al₂O₃, Fe₂O₃, MgO, and SiO₂), which displayed different crystallinity, textural properties, and amount of acid and basic sites. These catalysts were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), N₂ adsorption–desorption isotherms at −196 °C, NH₃ and CO₂ thermoprogrammed desorption analyses (NH₃- and CO₂-TPD, and X-ray photoelectron spectroscopy (XPS). Pd-based catalysts were tested in the oxidative condensation of furfural with ethanol to obtain value-added chemicals. The catalytic results revealed high conversion values, although the presence of a high proportion of carbonaceous deposits, mainly in the case of the PdO supported on β-zeolite and Al₂O₃, is also noteworthy. The presence of basic sites led to a beneficial effect on the catalytic behavior, since the formation of carbonaceous deposits was minimized. Thus, the 2Pd-MgO (2 wt.% Pd) catalyst reached the highest yield of furan-2-acrolein (70%) after 3 h of reaction at 170 °C. This better catalytic performance can be explained by the high basicity of MgO, used as support, together with the large amount of available PdO, as inferred from XPS. Full article

(This article belongs to the Special Issue Catalytic Transformation of Renewables (Olefin, Bio-sourced, et. al))

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12 pages, 3376 KiB

Open AccessArticle

In Situ Synthesis of Sn-Beta Zeolite Nanocrystals for Glucose to Hydroxymethylfurfural (HMF)

by Kachaporn Saenluang, Anawat Thivasasith, Pannida Dugkhuntod, Peerapol Pornsetmetakul, Saros Salakhum, Supawadee Namuangruk and Chularat Wattanakit

Catalysts 2020, 10(11), 1249; https://doi.org/10.3390/catal10111249 - 28 Oct 2020

Cited by 28 | Viewed by 4346

Abstract

The Sn substituted Beta nanocrystals have been successfully synthesized by in-situ hydrothermal process with the aid of cyclic diquaternary ammonium (CDM) as the structure-directing agent (SDA). This catalyst exhibits a bifunctional catalytic capability for the conversion of glucose to hydroxymethylfurfural (HMF). The incorporated [...] Read more.

The Sn substituted Beta nanocrystals have been successfully synthesized by in-situ hydrothermal process with the aid of cyclic diquaternary ammonium (CDM) as the structure-directing agent (SDA). This catalyst exhibits a bifunctional catalytic capability for the conversion of glucose to hydroxymethylfurfural (HMF). The incorporated Sn acting as Lewis acid sites can catalyze the isomerization of glucose to fructose. Subsequently, the Brønsted acid function can convert fructose to HMF via dehydration. The effects of Sn amount, zeolite type, reaction time, reaction temperature, and solvent on the catalytic performances of glucose to HMF, were also investigated in the detail. Interestingly, the conversion of glucose and the HMF yield over 0.4 wt% Sn-Beta zeolite nanocrystals using dioxane/water as a solvent at 120 °C for 24 h are 98.4% and 42.0%, respectively. This example illustrates the benefit of the in-situ synthesized Sn-Beta zeolite nanocrystals in the potential application in the field of biomass conversion. Full article

(This article belongs to the Special Issue Catalytic Transformation of Renewables (Olefin, Bio-sourced, et. al))

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13 pages, 1775 KiB

Open AccessArticle

The Influence of the Gold Particle Size on the Catalytic Oxidation of 5-(Hydroxymethyl)furfural

by Oliver Schade, Paolo Dolcet, Alexei Nefedov, Xiaohui Huang, Erisa Saraçi, Christof Wöll and Jan-Dierk Grunwaldt

Catalysts 2020, 10(3), 342; https://doi.org/10.3390/catal10030342 - 19 Mar 2020

Cited by 21 | Viewed by 4521

Abstract

For the production of chemicals from biomass, new selective processes are required. The selective oxidation of 5-(Hydroxymethyl)furfural (HMF), a promising platform molecule in fine chemistry, to 2,5-furandicarboxylic acid (FDCA) is considered a promising approach and requires the oxidation of two functional groups. In [...] Read more.

For the production of chemicals from biomass, new selective processes are required. The selective oxidation of 5-(Hydroxymethyl)furfural (HMF), a promising platform molecule in fine chemistry, to 2,5-furandicarboxylic acid (FDCA) is considered a promising approach and requires the oxidation of two functional groups. In this study, Au/ZrO₂ catalysts with different mean particle sizes were prepared by a chemical reduction method using tetrakis(hydroxymethyl)phosphonium chloride (THPC) and tested in HMF oxidation. The catalyst with the smallest mean particle size (2.1 nm) and the narrowest particle size distribution was highly active in the oxidation of the aldehyde moiety of HMF, but less active in alcohol oxidation. On the other hand, increased activity in FDCA synthesis up to 92% yield was observed over catalysts with a larger mean particle size (2.7 nm), which had a large fraction of small and some larger particles. A decreasing FDCA yield over the catalyst with the largest mean particle size (2.9 nm) indicates that the oxidation of both functional groups require different particle sizes and hint at the presence of an optimal particle size for both oxidation steps. The activity of Au particles seems to be influenced by surface steps and H bonding strength, the latter particularly in aldehyde oxidation. Therefore, the presence of both small and some larger Au particles seem to give catalysts with the highest catalytic activity. Full article

(This article belongs to the Special Issue Catalytic Transformation of Renewables (Olefin, Bio-sourced, et. al))

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15 pages, 1686 KiB

Open AccessArticle

Autocatalytic Fractionation of Wood Hemicelluloses: Modeling of Multistage Operation

by Mar López, Valentín Santos and Juan Carlos Parajó

Catalysts 2020, 10(3), 337; https://doi.org/10.3390/catal10030337 - 17 Mar 2020

Cited by 4 | Viewed by 2640

Abstract

Eucalyptus globulus wood samples were treated with hot, compressed water (autohydrolysis) in consecutive stages under non-isothermal conditions in order to convert the hemicellulose fraction into soluble compounds through reactions catalyzed by in situ generated acids. The first stage was a conventional autohydrolysis, and [...] Read more.

Eucalyptus globulus wood samples were treated with hot, compressed water (autohydrolysis) in consecutive stages under non-isothermal conditions in order to convert the hemicellulose fraction into soluble compounds through reactions catalyzed by in situ generated acids. The first stage was a conventional autohydrolysis, and liquid phase obtained under conditions leading to an optimal recovery of soluble saccharides was employed in a new reaction (second crossflow stage) using a fresh wood lot, in order to increase the concentrations of soluble saccharides. In the third crossflow stage, the best liquid phase from the second stage was employed to solubilize the hemicelluloses from a fresh wood lot. The concentration profiles determined for the soluble saccharides, acids, and furans present in the liquid phases from the diverse crossflow stages were employed for kinetic modeling, based on pseudohomogeneous reactions and Arrhenius-type dependence of the kinetic coefficients on temperature. Additional characterization of the reaction products by High Pressure Size Exclusion Chromatography, High Performance Anion Exchange Chromatography with Pulsed Amperometric Detection, and Matrix Assisted Laser Desorption/Ionization Time of Flight Mass Spectrometry provided further insight on the properties of the soluble saccharides present in the various reaction media. Full article

(This article belongs to the Special Issue Catalytic Transformation of Renewables (Olefin, Bio-sourced, et. al))

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16 pages, 4051 KiB

Open AccessArticle

5-Hydroxymethylfurfural and Furfural Base-Free Oxidation over AuPd Embedded Bimetallic Nanoparticles

by Camila P. Ferraz, Natalia J. S. Costa, Erico Teixeira-Neto, Ângela A. Teixeira-Neto, Cleber W. Liria, Joëlle Thuriot-Roukos, M. Teresa Machini, Rénato Froidevaux, Franck Dumeignil, Liane M. Rossi and Robert Wojcieszak

Catalysts 2020, 10(1), 75; https://doi.org/10.3390/catal10010075 - 4 Jan 2020

Cited by 19 | Viewed by 4228

Abstract

The heterogeneous catalytic partial oxidation of alcohols and aldehydes in the liquid phase usually needs the addition of a homogeneous base, which in turn makes the products’ recovery cumbersome, and can further induce undesired side reactions. In the present work, we propose the [...] Read more.

The heterogeneous catalytic partial oxidation of alcohols and aldehydes in the liquid phase usually needs the addition of a homogeneous base, which in turn makes the products’ recovery cumbersome, and can further induce undesired side reactions. In the present work, we propose the use of novel catalysts based on metallic Au, Pd and bimetallic AuPd nanoparticles embedded in a titanosilicate matrix. The as-prepared catalysts showed good efficiency in the base-free partial oxidation of furfural and 5-hydroxymethylfurfural. Au₄Pd₁@SiTi catalyst showed high selectivity (78%) to monoacids (namely, 5-formyl-2-furancarboxylic acid and 5-hydroxymethyl-2-furancarboxylic acid) at 50% 5-hydroxymethylfurfural (HMF) conversion. The selectivity even reached 83% in the case of furfural oxidation to furoic acid (at 50% furfural conversion). The performances of the catalysts strongly depended on the Au–Pd ratio, with an optimal value of 4:1. The pH of the solution was always below 3.5 and no leaching of metals was observed, confirming the stabilization of the metal nanoparticles within the titanosilicate host matrix. Full article

(This article belongs to the Special Issue Catalytic Transformation of Renewables (Olefin, Bio-sourced, et. al))

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12 pages, 2586 KiB

Open AccessArticle

Liquid Phase Furfural Oxidation under Uncontrolled pH in Batch and Flow Conditions: The Role of In Situ Formed Base

by Alessandra Roselli, Yuri Carvalho, Franck Dumeignil, Fabrizio Cavani, Sébastien Paul and Robert Wojcieszak

Catalysts 2020, 10(1), 73; https://doi.org/10.3390/catal10010073 - 3 Jan 2020

Cited by 22 | Viewed by 4924

Abstract

Selective oxidation of furfural to furoic acid was performed with pure oxygen in aqueous phase under mild conditions and uncontrolled pH using hydrotalcite-supported gold nanoparticles as catalyst. Hydrotalcites with different Mg: Al ratios were tested as support. The effects of reaction time, temperature [...] Read more.

Selective oxidation of furfural to furoic acid was performed with pure oxygen in aqueous phase under mild conditions and uncontrolled pH using hydrotalcite-supported gold nanoparticles as catalyst. Hydrotalcites with different Mg: Al ratios were tested as support. The effects of reaction time, temperature and furfural/catalyst ratio were evaluated. The catalyst Au/HT 4:1 showed the highest activity and selectivity to the desired product, achieving a complete conversion of furfural to furoic acid after 2 h at 110 °C. Further, stability tests were carried out in a continuous stirred-tank reactor and a progressive deactivation of the catalyst due to the leaching of Mg²⁺ cations from the support inducing changes in the pH of the reaction medium was observed. Full article

(This article belongs to the Special Issue Catalytic Transformation of Renewables (Olefin, Bio-sourced, et. al))

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16 pages, 4644 KiB

Open AccessFeature PaperArticle

Capping Agent Effect on Pd-Supported Nanoparticles in the Hydrogenation of Furfural

by Shahram Alijani, Sofia Capelli, Stefano Cattaneo, Marco Schiavoni, Claudio Evangelisti, Khaled M. H. Mohammed, Peter P. Wells, Francesca Tessore and Alberto Villa

Catalysts 2020, 10(1), 11; https://doi.org/10.3390/catal10010011 - 19 Dec 2019

Cited by 29 | Viewed by 4915

Abstract

The catalytic performance of a series of 1 wt % Pd/C catalysts prepared by the sol-immobilization method has been studied in the liquid-phase hydrogenation of furfural. The temperature range studied was 25–75 °C, keeping the H₂ pressure constant at 5 bar. The [...] Read more.

The catalytic performance of a series of 1 wt % Pd/C catalysts prepared by the sol-immobilization method has been studied in the liquid-phase hydrogenation of furfural. The temperature range studied was 25–75 °C, keeping the H₂ pressure constant at 5 bar. The effect of the catalyst preparation using different capping agents containing oxygen or nitrogen groups was assessed. Polyvinyl alcohol (PVA), polyvinylpyrrolidone (PVP), and poly (diallyldimethylammonium chloride) (PDDA) were chosen. The catalysts were characterized by ultraviolet-visible spectroscopy (UV-Vis), Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). The characterization data suggest that the different capping agents affected the initial activity of the catalysts by adjusting the available Pd surface sites, without producing a significant change in the Pd particle size. The different activity of the three catalysts followed the trend: Pd_PVA/C > Pd_PDDA/C > Pd_PVP/C. In terms of selectivity to furfuryl alcohol, the opposite trend has been observed: Pd_PVP/C > Pd_PDDA/C > Pd_PVA/C. The different reactivity has been ascribed to the different shielding effect of the three ligands used; they influence the adsorption of the reactant on Pd active sites. Full article

(This article belongs to the Special Issue Catalytic Transformation of Renewables (Olefin, Bio-sourced, et. al))

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21 pages, 1888 KiB

Open AccessArticle

First-Principles-Based Simulation of an Industrial Ethanol Dehydration Reactor

by Kristof Van der Borght, Konstantinos Alexopoulos, Kenneth Toch, Joris W. Thybaut, Guy B. Marin and Vladimir V. Galvita

Catalysts 2019, 9(11), 921; https://doi.org/10.3390/catal9110921 - 5 Nov 2019

Cited by 6 | Viewed by 4746

Abstract

The achievement of new economically viable chemical processes often involves the translation of observed lab-scale phenomena into performance in an industrial reactor. In this work, the in silico design and optimization of an industrial ethanol dehydration reactor were performed, employing a multiscale model [...] Read more.

The achievement of new economically viable chemical processes often involves the translation of observed lab-scale phenomena into performance in an industrial reactor. In this work, the in silico design and optimization of an industrial ethanol dehydration reactor were performed, employing a multiscale model ranging from nano-, over micro-, to macroscale. The intrinsic kinetics of the elementary steps was quantified through ab initio obtained rate and equilibrium coefficients. Heat and mass transfer limitations for the industrial design case were assessed via literature correlations. The industrial reactor model developed indicated that it is not beneficial to utilize feeds with high ethanol content, as they result in lower ethanol conversion and ethene yield. Furthermore, a more pronounced temperature drop over the reactor was simulated. It is preferred to use a more H₂O-diluted feed for the operation of an industrial ethanol dehydration reactor. Full article

(This article belongs to the Special Issue Catalytic Transformation of Renewables (Olefin, Bio-sourced, et. al))

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16 pages, 4551 KiB

Open AccessArticle

Tandem Hydrogenation/Hydrogenolysis of Furfural to 2-Methylfuran over a Fe/Mg/O Catalyst: Structure–Activity Relationship

by Carlo Lucarelli, Danilo Bonincontro, Yu Zhang, Lorenzo Grazia, Marc Renom-Carrasco, Chloé Thieuleux, Elsje Alessandra Quadrelli, Nikolaos Dimitratos, Fabrizio Cavani and Stefania Albonetti

Catalysts 2019, 9(11), 895; https://doi.org/10.3390/catal9110895 - 27 Oct 2019

Cited by 18 | Viewed by 5440

Abstract

The hydrodeoxygenation of furfural (FU) was investigated over Fe-containing MgO catalysts, on a continuous gas flow reactor, using methanol as a hydrogen donor. Catalysts were prepared either by coprecipitation or impregnation methods, with different Fe/Mg atomic ratios. The main product was 2-methylfuran (MFU), [...] Read more.

The hydrodeoxygenation of furfural (FU) was investigated over Fe-containing MgO catalysts, on a continuous gas flow reactor, using methanol as a hydrogen donor. Catalysts were prepared either by coprecipitation or impregnation methods, with different Fe/Mg atomic ratios. The main product was 2-methylfuran (MFU), an important highly added value chemical, up to 92% selectivity. The catalyst design helped our understanding of the impact of acid/base properties and the nature of iron species in terms of catalytic performance. In particular, the addition of iron on the surface of the basic oxide led to (i) the increase of Lewis acid sites, (ii) the increase of the dehydrogenation capacity of the presented catalytic system, and (iii) to the significant enhancement of the FU conversion to MFU. FTIR studies, using methanol as the chosen probe molecule, indicated that, at the low temperature regime, the process follows the typical hydrogen transfer reduction, but at the high temperature regime, methanol dehydrogenation and methanol disproportionation were both presented, whereas iron oxide promoted methanol transfer. FTIR studies were performed using furfural and furfuryl alcohol as probe molecules. These studies indicated that furfuryl alcohol activation is the rate-determining step for methyl furan formation. Our experimental results clearly demonstrate that the nature of iron oxide is critical in the efficient hydrodeoxygenation of furfural to methyl furan and provides insights toward the rational design of catalysts toward C–O bonds’ hydrodeoxygenation in the production of fuel components. Full article

(This article belongs to the Special Issue Catalytic Transformation of Renewables (Olefin, Bio-sourced, et. al))

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16 pages, 4645 KiB

Open AccessArticle

One-Pot Catalytic Conversion of Cellobiose to Sorbitol over Nickel Phosphides Supported on MCM-41 and Al-MCM-41

by Wipark Anutrasakda, Kanyanok Eiamsantipaisarn, Duangkamon Jiraroj, Apakorn Phasuk, Thawatchai Tuntulani, Haichao Liu and Duangamol Nuntasri Tungasmita

Catalysts 2019, 9(1), 92; https://doi.org/10.3390/catal9010092 - 16 Jan 2019

Cited by 12 | Viewed by 4704

Abstract

MCM-41- and Al-MCM-41-supported nickel phosphide nanomaterials were synthesized at two different initial molar ratios of Ni/P: 10:2 and 10:3 and were tested as heterogeneous catalysts for the one-pot conversion of cellobiose to sorbitol. The catalysts were characterized by X-ray diffractometer (XRD), N2 adsorption-desorption, [...] Read more.

MCM-41- and Al-MCM-41-supported nickel phosphide nanomaterials were synthesized at two different initial molar ratios of Ni/P: 10:2 and 10:3 and were tested as heterogeneous catalysts for the one-pot conversion of cellobiose to sorbitol. The catalysts were characterized by X-ray diffractometer (XRD), N2 adsorption-desorption, scanning electron microscope (SEM), transmission electron microscope (TEM), ²⁷Al-magnetic angle spinning-nuclear magnetic resonance spectrometer (²⁷Al MAS-NMR), temperature programmed desorption of ammonia (NH₃-TPD), temperature-programmed reduction (H₂-TPR), and inductively coupled plasma optical emission spectrophotometer (ICP-OES). The characterization indicated that nickel phosphide nanoparticles were successfully incorporated into both supports without destroying their hexagonal framework structures, that the catalysts contained some or all of the following Ni-containing phases: Ni⁰, Ni₃P, and Ni₁₂P₅, and that the types and relative amounts of Ni-containing phases present in each catalyst were largely determined by the initial molar ratio of Ni/P as well as the type of support used. For cellobiose conversion at 150 °C for 3 h under 4 MPa of H₂, all catalysts showed similarly high conversion of cellobiose (89.5–95.0%). Nevertheless, sorbitol yield was highly correlated to the relative amount of phases with higher content of phosphorus present in the catalysts, giving the following order of catalytic performance of the Ni-containing phases: Ni₁₂P₅ > Ni₃P > Ni. Increasing the reaction temperature from 150 °C to 180 °C also led to an improvement in sorbitol yield (from 43.5% to 87.8%). Full article

(This article belongs to the Special Issue Catalytic Transformation of Renewables (Olefin, Bio-sourced, et. al))

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13 pages, 1200 KiB

Open AccessArticle

Selective Synthesis of Furfuryl Alcohol from Biomass-Derived Furfural Using Immobilized Yeast Cells

by Xue-Ying Zhang, Zhong-Hua Xu, Min-Hua Zong, Chuan-Fu Wang and Ning Li

Catalysts 2019, 9(1), 70; https://doi.org/10.3390/catal9010070 - 10 Jan 2019

Cited by 27 | Viewed by 4757

Abstract

Furfuryl alcohol (FA) is an important building block in polymer, food, and pharmaceutical industries. In this work, we reported the biocatalytic reduction of furfural, one of the top value-added bio-based platform chemicals, to FA by immobilized Meyerozyma guilliermondii SC1103 cells. The biocatalytic process [...] Read more.

Furfuryl alcohol (FA) is an important building block in polymer, food, and pharmaceutical industries. In this work, we reported the biocatalytic reduction of furfural, one of the top value-added bio-based platform chemicals, to FA by immobilized Meyerozyma guilliermondii SC1103 cells. The biocatalytic process was optimized, and the tolerance of this yeast strain toward toxic furfural was evaluated. It was found that furfural of 200 mM could be reduced smoothly to the desired product FA with the conversion of 98% and the selectivity of >98%, while the FA yield was only approximately 81%. The gap between the substrate conversion and the product yield might partially be attributed to the substantial adsorption of the immobilization material (calcium alginate) toward the desired product, but microbial metabolism of furans (as carbon sources) made a negligible contribution to it. In addition, FA of approximately 156 mM was produced within 7 h in a scale-up reaction, along with the formation of trace 2-furoic acid (1 mM) as the byproduct. The FA productivity was up to 2.9 g/L/h, the highest value ever reported in the biocatalytic synthesis of FA. The crude FA was simply separated from the reaction mixture by organic solvent extraction, with the recovery of 90% and the purity of 88%. FA as high as 266 mM was produced by using a fed-batch strategy within 15.5 h. Full article

(This article belongs to the Special Issue Catalytic Transformation of Renewables (Olefin, Bio-sourced, et. al))

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14 pages, 11607 KiB

Open AccessArticle

A Comparative Study of MFI Zeolite Derived from Different Silica Sources: Synthesis, Characterization and Catalytic Performance

by Jianguang Zhang, Xiangping Li, Juping Liu and Chuanbin Wang

Catalysts 2019, 9(1), 13; https://doi.org/10.3390/catal9010013 - 26 Dec 2018

Cited by 36 | Viewed by 6312

Abstract

In this paper, a comparative study of MFI zeolite derived from different silica sources is presented. Dry gel conversion (DGC) method is used to synthesize silicalite-1 and ZSM-5 with MFI structure. Two kinds of silica sources with different particle sizes are used during [...] Read more.

In this paper, a comparative study of MFI zeolite derived from different silica sources is presented. Dry gel conversion (DGC) method is used to synthesize silicalite-1 and ZSM-5 with MFI structure. Two kinds of silica sources with different particle sizes are used during the synthesis of MFI zeolite. The as-prepared samples were characterized by X-ray diffraction (XRD), N₂-sorption, Fourier transform infrared spectroscopy (FTIR), Scanning electron microscopy (SEM) and X-ray fluorescence spectrometer (XRF). From the characterization results, it could be seen that the high-quality coffin-like silicalite-1 was synthesized using silica sphere with particle size of 300 nm as silica source, with crystallization time being shortened to 2 h. The schematic diagram of silicalite-1 formation using silica sources with different particle sizes is summarized. ZSM-5 was obtained by adding Al atoms to raw materials during the synthesis of MFI zeolite. The performance of aqueous phase eugenol hydrodeoxygenation over Pd/C-ZSM-5 catalyst is evaluated. Full article

(This article belongs to the Special Issue Catalytic Transformation of Renewables (Olefin, Bio-sourced, et. al))

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0 pages, 5013 KiB

Open AccessArticle

RETRACTED: The Influence of Texture on Co/SBA–15 Catalyst Performance for Fischer–Tropsch Synthesis

by Jun Han, Zijiang Xiong, Zelin Zhang, Hongjie Zhang, Peng Zhou and Fei Yu

Catalysts 2018, 8(12), 661; https://doi.org/10.3390/catal8120661 - 16 Dec 2018

Cited by 8 | Viewed by 3833 | Retraction

Abstract

The influence of the Co/SBA–15 catalyst texture, such as pore size and pore length on Fischer–Tropsch (FT) Synthesis, was investigated in this paper. The morphology, structure, and microstructures of Co/SBA–15 catalysts were characterized by SEM, Brunauer–Emmett–Teller (BET), TPR, HRTEM, and XRD. The experimental [...] Read more.

The influence of the Co/SBA–15 catalyst texture, such as pore size and pore length on Fischer–Tropsch (FT) Synthesis, was investigated in this paper. The morphology, structure, and microstructures of Co/SBA–15 catalysts were characterized by SEM, Brunauer–Emmett–Teller (BET), TPR, HRTEM, and XRD. The experimental results indicated that the increase of pore size could improve the activity of the Co/SBA–15 catalyst, and the further increase of pore size could not significantly promote the activity. Moreover, it was also found that the pore length of the Co/SBA–15 catalyst played a key role in the catalytic activity. CO₂ and C4+ selectivity were 2.0% and 74% during the simulated syngas (64% H₂: 32% CO: balanced N₂) FT over the Co/SBA–15 catalysts, and CO conversion rate and CH₄ selectivity were 10.8% and 15.7% after 100 h time on stream. Full article

(This article belongs to the Special Issue Catalytic Transformation of Renewables (Olefin, Bio-sourced, et. al))

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12 pages, 3589 KiB

Open AccessArticle

MPV Reduction of Furfural to Furfuryl Alcohol on Mg, Zr, Ti, Zr–Ti, and Mg–Ti Solids: Influence of Acid–Base Properties

by Jesús Hidalgo-Carrillo, Almudena Parejas, Manuel Jorge Cuesta-Rioboo, Alberto Marinas and Francisco José Urbano

Catalysts 2018, 8(11), 539; https://doi.org/10.3390/catal8110539 - 13 Nov 2018

Cited by 18 | Viewed by 4752

Abstract

The Meerwein–Ponndorf–Verley (MPV) reaction is an environmentally-friendly process consisting of the reduction of a carbonyl compound through hydrogen transfer from a secondary alcohol. This work deals with MPV reduction of furfural to furfuryl alcohol on different ZrO_x, MgO_x, TiO [...] Read more.

The Meerwein–Ponndorf–Verley (MPV) reaction is an environmentally-friendly process consisting of the reduction of a carbonyl compound through hydrogen transfer from a secondary alcohol. This work deals with MPV reduction of furfural to furfuryl alcohol on different ZrO_x, MgO_x, TiO_x, and Mg–Ti, as well as Zr–Ti mixed systems. The solids were synthesized through the sol–gel process and subsequently calcined at 200 °C. Characterization was performed using a wide range of techniques: ICP-MS, N₂ adsorption-desorption isotherms, EDX, TGA-DTA, XRD, XPS, TEM, TPD of pre-adsorbed pyridine (acidity) and CO₂ (basicity), DRIFT of adsorbed pyridine, and methylbutynol (MBOH) test reaction. ZrO_x showed the highest conversion and selectivity values, which was attributed to the existence of acid–base pair sites (as evidenced by the MBOH test reaction), whereas the introduction of titanium resulted in the drop of both conversion and selectivity probably due to the increase in Brönsted-type acidity. As for MgO_x, it had a predominantly basic character that led to the production of the condensation product of one molecule of furfural and one molecule of acetone, and thus resulted in a lower selectivity to furfuryl alcohol. The TiO_x solid was found to be mainly acidic and exhibited both Lewis and Brönsted acid sites. The presence of the latter could account for the lower selectivity to furfuryl alcohol. All in all, these results seemed to suggest that the MPV reaction is favored on Lewis acid sites and especially on acid–base pair sites. The process was accelerated under microwave irradiation. Full article

(This article belongs to the Special Issue Catalytic Transformation of Renewables (Olefin, Bio-sourced, et. al))

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21 pages, 16049 KiB

Open AccessReview

Zeolites as Acid/Basic Solid Catalysts: Recent Synthetic Developments

by Valentina Verdoliva, Michele Saviano and Stefania De Luca

Catalysts 2019, 9(3), 248; https://doi.org/10.3390/catal9030248 - 8 Mar 2019

Cited by 69 | Viewed by 24490 | Correction

Abstract

The zeolites are porous solid structures characterized by a particular framework of aluminosilicates, in which the incorporation of the Al⁺³ ions generates an excess of negative charge compensated by cations (usually alkali or alkali earth) or protons. In the latter case, they [...] Read more.

The zeolites are porous solid structures characterized by a particular framework of aluminosilicates, in which the incorporation of the Al⁺³ ions generates an excess of negative charge compensated by cations (usually alkali or alkali earth) or protons. In the latter case, they are employed as catalysts for a wide variety of reactions, such as dehydration, skeletal isomerization and cracking, while the catalytic activity of basic zeolites has not found, up to now, any industrial or whatever relevant application in chemical processes. In the present review, we firstly intend to give an overview of the fundamental chemical composition, as well as the structural features of the zeolite framework. The purpose of this paper is to analyze their key properties as acid, both Lewis and Brønsted, and basic solid support. Their application as catalysts is discussed by reviewing the already published works in that field, and a final remark of their still unexplored potential as green, mild, and selective catalyst is also reported. Full article

(This article belongs to the Special Issue Catalytic Transformation of Renewables (Olefin, Bio-sourced, et. al))

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