Research

14 pages, 2519 KiB

Open AccessArticle

Mesoporous Activated Carbon Supported Ru Catalysts to Efficiently Convert Cellulose into Sorbitol by Hydrolytic Hydrogenation

by Fatima-Zahra Azar, M. Ángeles Lillo-Ródenas and M. Carmen Román-Martínez

Energies 2020, 13(17), 4394; https://doi.org/10.3390/en13174394 - 26 Aug 2020

Cited by 7 | Viewed by 2433

Abstract

Catalysts consisting of Ru nanoparticles (1 wt%), supported on mesoporous activated carbons (ACs), were prepared and used in the one-pot hydrolytic hydrogenation of cellulose to obtain sorbitol. The carbon materials used as supports are a pristine commercial mesoporous AC (named SA), and two [...] Read more.

Catalysts consisting of Ru nanoparticles (1 wt%), supported on mesoporous activated carbons (ACs), were prepared and used in the one-pot hydrolytic hydrogenation of cellulose to obtain sorbitol. The carbon materials used as supports are a pristine commercial mesoporous AC (named SA), and two samples derived from it by sulfonation or oxidation treatments (named SASu and SAS, respectively). The catalysts have been thoroughly characterized regarding both surface chemistry and porosity, as well as Ru electronic state and particle size. The amount and type of surface functional groups in the carbon materials becomes modified as a result of the Ru incorporation process, while a high mesopore volume is preserved upon functionalization and Ru incorporation. The prepared catalysts have shown to be very active, with cellulose conversion close to 50% and selectivity to sorbitol above 75%. The support functionalization does not lead to an improvement of the catalysts’ behavior and, in fact, the Ru/SA catalyst is the most effective one, with about 50% yield to sorbitol, and a very low generation of by-products. Full article

(This article belongs to the Special Issue Catalytic Conversion of Energy Resources into High Value-Added Products)

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19 pages, 5814 KiB

Open AccessArticle

Ni Supported on Natural Clays as a Catalyst for the Transformation of Levulinic Acid into γ-Valerolactone without the Addition of Molecular Hydrogen

by Adrián García, Rut Sanchis, Francisco J. Llopis, Isabel Vázquez, María Pilar Pico, María Luisa López, Inmaculada Álvarez-Serrano and Benjamín Solsona

Energies 2020, 13(13), 3448; https://doi.org/10.3390/en13133448 - 03 Jul 2020

Cited by 10 | Viewed by 2394

Abstract

γ-Valerolactone (GVL) is a valuable chemical that can be used as a clean additive for automotive fuels. This compound can be produced from biomass-derived compounds. Levulinic acid (LA) is a compound that can be obtained easily from biomass and it can be transformed [...] Read more.

γ-Valerolactone (GVL) is a valuable chemical that can be used as a clean additive for automotive fuels. This compound can be produced from biomass-derived compounds. Levulinic acid (LA) is a compound that can be obtained easily from biomass and it can be transformed into GVL by dehydration and hydrogenation using metallic catalysts. In this work, catalysts of Ni (a non-noble metal) supported on a series of natural and low-cost clay-materials have been tested in the transformation of LA into GVL. Catalysts were prepared by a modified wet impregnation method using oxalic acid trying to facilitate a suitable metal dispersion. The supports employed are attapulgite and two sepiolites with different surface areas. Reaction tests have been undertaken using an aqueous medium at moderate reaction temperatures of 120 and 180 °C. Three types of experiments were undertaken: (i) without H₂ source, (ii) using formic acid (FA) as hydrogen source and (iii) using Zn in order to transform water in hydrogen through the reaction Zn + H₂O → ZnO + H₂. The best results have been obtained combining Zn (which plays a double role as a reactant for hydrogen formation and as a catalyst) and Ni/attapulgite. Yields to GVL higher than 98% have been obtained at 180 °C in the best cases. The best catalytic performance has been related to the presence of tiny Ni particles as nickel crystallites larger than 4 nm were not present in the most efficient catalysts. Full article

(This article belongs to the Special Issue Catalytic Conversion of Energy Resources into High Value-Added Products)

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15 pages, 1244 KiB

Open AccessArticle

Application of Upgraded Drop-In Fuel Obtained from Biomass Pyrolysis in a Spark Ignition Engine

by Alberto Veses, Juan Daniel Martínez, María Soledad Callén, Ramón Murillo and Tomás García

Energies 2020, 13(8), 2089; https://doi.org/10.3390/en13082089 - 22 Apr 2020

Cited by 11 | Viewed by 2286

Abstract

This paper reports the performance of a spark ignition engine using gasoline blended with an upgraded bio-oil rich in aromatics and ethanol. This upgraded bio-oil was obtained using a two-step catalytic process. The first step comprised an in-situ catalytic pyrolysis process with CaO [...] Read more.

This paper reports the performance of a spark ignition engine using gasoline blended with an upgraded bio-oil rich in aromatics and ethanol. This upgraded bio-oil was obtained using a two-step catalytic process. The first step comprised an in-situ catalytic pyrolysis process with CaO in order to obtain a more stable deoxygenated organic fraction, while the second consisted of a catalytic cracking of the vapours released using ZSM-5 zeolites to obtain an aromatics-rich fraction. To facilitate the mixture between bio-oil and gasoline, ethanol was added. The behaviour of a stationary spark ignition engine G12TFH (9600 W) was described in terms of fuel consumption and electrical efficiency. In addition, gaseous emissions and polycyclic aromatic hydrocarbon (PAH) concentrations were determined. Trial tests suggested that it is possible to work with a blend of gasoline, ethanol and bio-oil (90/8/2 vol%, herein named G90E8B2) showing similar fuel consumption than pure gasoline (G100) at the same load. Moreover, combustion could be considered more efficient when small quantities of ethanol and organic bio-oil are simultaneously added. A reduction, not only in the PAH concentrations but also in the carcinogenic equivalent concentrations, was also obtained, decreasing the environmental impact of the exhaust gases. Thus, results show that it is technically feasible to use low blends of aroma-rich bio-oil, ethanol and gasoline in conventional spark ignition engines. Full article

(This article belongs to the Special Issue Catalytic Conversion of Energy Resources into High Value-Added Products)

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19 pages, 6637 KiB

Open AccessArticle

Nanostructured Carbon Material Effect on the Synthesis of Carbon-Supported Molybdenum Carbide Catalysts for Guaiacol Hydrodeoxygenation

by Elba Ochoa, Daniel Torres, José Luis Pinilla and Isabel Suelves

Energies 2020, 13(5), 1189; https://doi.org/10.3390/en13051189 - 05 Mar 2020

Cited by 8 | Viewed by 2319

Abstract

The impact of using different nanostructured carbon materials (carbon nanofibers, carbon nanotubes, graphene oxide and activated carbon) as a support for Mo₂C-based catalysts on the hydrodeoxygenation (HDO) of guaiacol was studied. To optimise the catalyst preparation by carbothermal hydrogen reduction (CHR), [...] Read more.

The impact of using different nanostructured carbon materials (carbon nanofibers, carbon nanotubes, graphene oxide and activated carbon) as a support for Mo₂C-based catalysts on the hydrodeoxygenation (HDO) of guaiacol was studied. To optimise the catalyst preparation by carbothermal hydrogen reduction (CHR), a thermogravimetric study was conducted to select the optimum CHR temperature for each carbon material, considering both the crystal size of the resulting β-Mo₂C particles and the extent of the support gasification. Subsequently, catalysts were prepared in a fixed bed reactor at the optimum temperature. Catalyst characterization evidenced the differences in the catalyst morphology as compared to those prepared in the thermogravimetric study. The HDO results demonstrated that the carbon nanofiber-based catalyst was the one with the best catalytic performance. This behaviour was attributed to the high thermal stability of this support, which prevented its gasification and promoted a good evolution of the crystal size of Mo species. This catalyst exhibited well-dispersed β-Mo₂C nanoparticles of ca. 11 nm. On the contrary, the other supports suffered from severe gasification (60–70% wt. loss), which resulted in poorer HDO efficiency catalysts regardless of the β-Mo₂C crystal size. This exhibited the importance of the carbon support stability in Mo₂C-based catalysts prepared by CHR. Full article

(This article belongs to the Special Issue Catalytic Conversion of Energy Resources into High Value-Added Products)

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14 pages, 4592 KiB

Open AccessArticle

Catalytic Steam Reforming of Toluene: Understanding the Influence of the Main Reaction Parameters over a Reference Catalyst

by Hua Lun Zhu, Laura Pastor-Pérez and Marcos Millan

Energies 2020, 13(4), 813; https://doi.org/10.3390/en13040813 - 13 Feb 2020

Cited by 13 | Viewed by 3670

Abstract

Identifying the suitable reaction conditions is key to achieve high performance and economic efficiency in any catalytic process. In this study, the catalytic performance of a Ni/Al₂O₃ catalyst, a benchmark system—was investigated in steam reforming of toluene as a biomass [...] Read more.

Identifying the suitable reaction conditions is key to achieve high performance and economic efficiency in any catalytic process. In this study, the catalytic performance of a Ni/Al₂O₃ catalyst, a benchmark system—was investigated in steam reforming of toluene as a biomass gasification tar model compound to explore the effect of reforming temperature, steam to carbon (S/C) ratio and residence time on toluene conversion and gas products. An S/C molar ratio range from one to three and temperature range from 700 to 900 °C was selected according to thermodynamic equilibrium calculations, and gas hourly space velocity (GHSV) was varied from 30,600 to 122,400 h⁻¹ based on previous work. The results suggest that 800 °C, GHSV 61,200 h⁻¹ and S/C ratio 3 provide favourable operating conditions for steam reforming of toluene in order to get high toluene conversion and hydrogen productivity, achieving a toluene to gas conversion of 94% and H₂ production of 13 mol/mol toluene. Full article

(This article belongs to the Special Issue Catalytic Conversion of Energy Resources into High Value-Added Products)

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10 pages, 2123 KiB

Open AccessArticle

Preparation of Solid Fuel Hydrochar over Hydrothermal Carbonization of Red Jujube Branch

by Zhiyu Li, Weiming Yi, Zhihe Li, Chunyan Tian, Peng Fu, Yuchun Zhang, Ling Zhou and Jie Teng

Energies 2020, 13(2), 480; https://doi.org/10.3390/en13020480 - 18 Jan 2020

Cited by 17 | Viewed by 3032

Abstract

Biomass energy is becoming increasingly important, owing to the decreasing supply of fossil fuels and growing environmental problems. Hydrothermal carbonization (HTC) is a promising technology for producing solid biofuels from agricultural and forestry residues because of its lower fossil-fuel consumption. In this study, [...] Read more.

Biomass energy is becoming increasingly important, owing to the decreasing supply of fossil fuels and growing environmental problems. Hydrothermal carbonization (HTC) is a promising technology for producing solid biofuels from agricultural and forestry residues because of its lower fossil-fuel consumption. In this study, HTC was used to upgrade red jujube branch (RJB) to prepare hydrochar at six temperatures (220, 240, 260, 280, 300, and 320 °C) for 120 min, and at 300 °C for 30, 60, 90, and 120 min. The results showed that the energy recovery efficiency (ERE) reached maximum values of 80.42% and 79.86% at a residence time of 90 min and a reaction temperature of 220 °C, respectively. X-ray diffraction results and Fourier transform infrared spectroscopy measurements show that the microcrystal features of RJB were destroyed, whereas the hydrochar contained an amorphous structure and mainly lignin fractions at increased temperatures. Thermogravimetric analysis shows that the hydrochar had better fuel qualities than RJB, making hydrochar easier to burn. Full article

(This article belongs to the Special Issue Catalytic Conversion of Energy Resources into High Value-Added Products)

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14 pages, 1478 KiB

Open AccessArticle

Investigating the Influence of Reaction Conditions and the Properties of Ceria for the Valorisation of Glycerol

by Paul J. Smith, Louise Smith, Nicholas F. Dummer, Mark Douthwaite, David J. Willock, Mark Howard, David W. Knight, Stuart H. Taylor and Graham J. Hutchings

Energies 2019, 12(7), 1359; https://doi.org/10.3390/en12071359 - 09 Apr 2019

Cited by 10 | Viewed by 2782

Abstract

The reaction of aqueous glycerol over a series of ceria catalysts is investigated, to produce bio-renewable methanol. Product distributions were greatly influenced by the reaction temperature and catalyst contact time. Glycerol conversion of 21% was achieved for a 50 wt.% glycerol solution, over [...] Read more.

The reaction of aqueous glycerol over a series of ceria catalysts is investigated, to produce bio-renewable methanol. Product distributions were greatly influenced by the reaction temperature and catalyst contact time. Glycerol conversion of 21% was achieved for a 50 wt.% glycerol solution, over CeO₂ (8 m² g⁻¹) at 320 °C. The carbon mass balance was >99 % and the main product was hydroxyacetone. In contrast, at 440 °C the conversion and carbon mass balance were >99.9 % and 76 % respectively. Acetaldehyde and methanol were the major products at this higher temperature, as both can be formed from hydroxyacetone. The space-time yield (STY) of methanol at 320 °C and 440 °C was 15.2 and 145 g_MeOH kg_cat⁻¹ h⁻¹ respectively. Fresh CeO₂ was prepared and calcined at different temperatures, the textural properties were determined and their influence on the product distribution at iso-conversion and constant bed surface area was investigated. No obvious differences to the glycerol conversion or product selectivity were noted. Hence, we conclude that the surface area of the CeO₂ does not appear to influence the reaction selectivity to methanol and other products formed from the conversion of glycerol. Full article

(This article belongs to the Special Issue Catalytic Conversion of Energy Resources into High Value-Added Products)

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14 pages, 2509 KiB

Open AccessArticle

Biogas Upgrading Via Dry Reforming Over a Ni-Sn/CeO₂-Al₂O₃ Catalyst: Influence of the Biogas Source

by Estelle le Saché, Sarah Johnson, Laura Pastor-Pérez, Bahman Amini Horri and Tomas R. Reina

Energies 2019, 12(6), 1007; https://doi.org/10.3390/en12061007 - 15 Mar 2019

Cited by 44 | Viewed by 4445

Abstract

Biogas is a renewable, as well as abundant, fuel source which can be utilised in the production of heat and electricity as an alternative to fossil fuels. Biogas can additionally be upgraded via the dry reforming reactions into high value syngas. Nickel-based catalysts [...] Read more.

Biogas is a renewable, as well as abundant, fuel source which can be utilised in the production of heat and electricity as an alternative to fossil fuels. Biogas can additionally be upgraded via the dry reforming reactions into high value syngas. Nickel-based catalysts are well studied for this purpose but have shown little resilience to deactivation caused by carbon deposition. The use of bi-metallic formulations, as well as the introduction of promoters, are hence required to improve catalytic performance. In this study, the effect of varying compositions of model biogas (CH₄/CO₂ mixtures) on a promising multicomponent Ni-Sn/CeO₂-Al₂O₃ catalyst was investigated. For intermediate temperatures (650 °C), the catalyst displayed good levels of conversions in a surrogate sewage biogas (CH₄/CO₂ molar ratio of 1.5). Little deactivation was observed over a 20 h stability run, and greater coke resistance was achieved, related to a reference catalyst. Hence, this research confirms that biogas can suitably be used to generate H₂-rich syngas at intermediate temperatures provided a suitable catalyst is employed in the reaction. Full article

(This article belongs to the Special Issue Catalytic Conversion of Energy Resources into High Value-Added Products)

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