Showing papers by "Tomas Ramirez Reina published in 2019"
TL;DR: In this article, the authors have analyzed several novel approaches, including catalytic transfer hydrogenation (CTH), combined reforming and hydrodeoxygenation, metal hydrolysis and subsequent hydrogenation along with non-thermal nitrogen tetramer (NTP) in order to avoid the supply of external H2.
Abstract: Catalytic hydrodeoxygenation (HDO) is a fundamental
process for bio-resources upgrading to produce transportation
fuels or added value chemicals. The bottleneck of this technology
to be implemented at commercial scale is its dependence on high
pressure hydrogen, an expensive resource which utilization also
poses safety concerns. In this scenario, the development of
hydrogen-free alternatives to facilitate oxygen removal in biomass
derived compounds is a major challenge for catalysis science but
at the same time it could revolutionize biomass processing
technologies. In this review we have analyzed several novel
approaches, including catalytic transfer hydrogenation (CTH),
combined reforming and hydrodeoxygenation, metal hydrolysis
and subsequent hydrodeoxygenation along with non-thermal
plasma (NTP) in order to avoid the supply of external H2. The
knowledge accumulated from traditional HDO sets the grounds
for catalysts and processes development among the hydrogen
alternatives. In this sense, mechanistic aspects for HDO and the
proposed alternatives are carefully analyzed in this work.
Biomass model compounds are selected aiming to provide an indepth
description of the different processes and stablish solid
correlations catalysts composition-catalytic performance which
can be further extrapolated to more complex biomass feedstocks.
Moreover, the current challenges and research trends of novel
hydrodeoxygenation strategies are also presented aiming to
spark inspiration among the broad community of scientists
working towards a low carbon society where bio-resources will
play a major role.
145 citations
TL;DR: In this paper, the authors demonstrate that the activity and selectivity of this system can be boosted by the addition of promoters such as Cu and Cs, which is an underexplored dopant whose marked electropositive character generates electronic perturbations on the catalyst surface.
Abstract: Mo2C is an effective catalyst for chemical CO2 upgrading via reverse water-gas shift (RWGS). In this work, we demonstrate that the activity and selectivity of this system can be boosted by the addition of promoters such as Cu and Cs. The addition of Cu incorporates extra active sites such as Cu+ and Cu0 which are essential for the reaction. Cs is an underexplored dopant whose marked electropositive character generates electronic perturbations on the catalyst’s surface leading to enhanced catalytic performance. Also, the Cs-doped catalyst seems to be in-situ activated due to a re-carburization phenomenon which results in fairly stable catalysts for continuous operations. Overall, this work showcases a strategy to design highly efficient catalysts based on promoted β-Mo2C for CO2 recycling via RWGS.
93 citations
TL;DR: In this paper, the authors demonstrate the advantage of using graphene oxide as a sacrificial template for the production of sintering-resistant catalysts with good catalytic performance at high temperatures.
Abstract: The development of novel fabrication methods to produce ceria catalysts with good high-temperature stability is critical for their implementation across a range of different applications. Herein, graphene oxide flakes are used as a sacrificial template in the synthesis of ceria particles to replicate the graphene oxide’s two-dimensionality. While performing the synthesis without graphene oxide results in large agglomerations of ceria crystallites, the addition of graphene oxide during the synthesis results in ceria nanoflakes ( 400 °C) which results in improved catalytic performance for the oxidation of carbon monoxide. This resistance versus sintering has also a beneficial effect when ceria flakes are used as catalytic support of nickel particles. Improved metal dispersion and high metal-support interaction leads to lower sintering during the dry reforming of methane than similarly prepared un-templated ceria nickel catalysts. These results demonstrate the advantage of using graphene oxide as a sacrificial template for the production of sintering-resistant catalysts with good catalytic performance at high temperatures.
47 citations
TL;DR: In this paper, the effect of varying compositions of model biogas (CH4/CO2 mixtures) on a promising multicomponent Ni-Sn/CeO2-Al2O3 catalyst was investigated.
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 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.
38 citations
TL;DR: In this paper, the use of water as reaction media and the utilization of multifunctional catalysts that are able to conduct multiple steps such as water activation and HDO was proposed.
Abstract: This work showcases an innovative route for biocompound upgrading via hydrodeoxygenation (HDO) reactions, eliminating the need for external high-pressure hydrogen supply. We propose the use of water as reaction media and the utilization of multifunctional catalysts that are able to conduct multiple steps such as water activation and HDO. In this study, we validate our hypothesis in a high-pressure batch reactor process using guaiacol as a model compound and multicomponent Ni-based catalysts. In particular, a comparison between ceria-supported and carbon/ceria-supported samples is established, the carbon-based materials being the suitable choice for this reaction. The physicochemical study by X-ray photoelectron spectroscopy, transmission electron microscopy, X-ray diffraction, and temperature-programmed reduction reveals the greater dispersion of Ni clusters and the strong metal-support interaction in the carbon/ceria-based samples accounting for the enhanced performance. In addition, the characterization of the spent samples points out the resistance of our catalysts toward sintering and coking. Overall, the novel catalytic approach proposed in this paper opens new research possibilities to achieve low-cost bio-oil upgrading processes.
37 citations
TL;DR: In this article, a Pt-based catalyst supported on N-doped activated carbon prepared from polypyrrole as the nitrogen source (Pt/N-AC) was developed and applied in the palm oil deoxygenation process to produce BHD in a fixed bed reactor system.
Abstract: Bio-hydrogenated diesel (BHD), derived from vegetable oil via hydrotreating technology, is
a promising alternative transportation fuel to replace nonsustainable petroleum diesel. In this work,
a novel Pt-based catalyst supported on N-doped activated carbon prepared from polypyrrole as the
nitrogen source (Pt/N-AC) was developed and applied in the palm oil deoxygenation process to
produce BHD in a fixed bed reactor system. High conversion rates of triglycerides (conversion of
TG > 90%) and high deoxygenation percentage (DeCOx% = 76% and HDO% = 7%) were obtained
for the palm oil deoxygenation over Pt/N-AC catalyst at optimised reaction conditions: T = 300 ◦C,
30 bar of H2, and LHSV = 1.5 h−1
. In addition to the excellent performance, the Pt/N-AC catalyst
is highly stable in the deoxygenation reaction, as confirmed by the XRD and TEM analyses of the
spent sample. The incorporation of N atoms in the carbon structure alters the electronic density of the
catalyst, favouring the interaction with electrophilic groups such as carbonyls, and thus boosting the
DeCOx route over the HDO pathway. Overall, this work showcases a promising route to produce
added value bio-fuels from bio-compounds using advanced N-doped catalysts.
35 citations
TL;DR: In this article, bimetallic 1Cu-Ni catalysts have been studied in the water-gas shift (WGS) reaction, and they have shown different levels of synergy and anti-synergy in terms of catalytic activity and selectivity to the desired products.
35 citations
TL;DR: In this article, a review of state-of-the-art catalysts for dry reforming of ethanol and glycerol is presented along with challenges and future opportunities to further develop the dry reforming routes as viable CO2 utilization alternatives.
Abstract: Dry reforming of ethanol and glycerol using CO2 are promising technologies for H2
production while mitigating CO2 emission. Current studies mainly focused on steam reforming
technology, while dry reforming has been typically less studied. Nevertheless, the urgent problem
of CO2 emissions directly linked to global warming has sparked a renewed interest on the catalysis
community to pursue dry reforming routes. Indeed, dry reforming represents a straightforward
route to utilize CO2 while producing added value products such as syngas or hydrogen. In the
absence of catalysts, the direct decomposition for H2 production is less efficient. In this mini-review,
ethanol and glycerol dry reforming processes have been discussed including their mechanistic
aspects and strategies for catalysts successful design. The effect of support and promoters is
addressed for better elucidating the catalytic mechanism of dry reforming of ethanol and glycerol.
Activity and stability of state-of-the-art catalysts are comprehensively discussed in this review along
with challenges and future opportunities to further develop the dry reforming routes as viable CO2 utilization alternatives.
34 citations
TL;DR: In this article, the potential application of Ni2P as highly effective catalyst for chemical CO2 recycling via dry reforming of methane (DRM) was reported, with the Ni hollow site being the most energetically stable site and Ni-P and P contributes as co-adsorption sites in DRM reaction steps.
Abstract: This study reports the potential application of Ni2P as highly effective catalyst for chemical CO2 recycling via dry reforming of methane (DRM). Our DFT calculations reveal that the Ni2P (0001) surface is active towards adsorption of the DRM species, with the Ni hollow site being the most energetically stable site and Ni-P and P contributes as co-adsorption sites in DRM reaction steps. Free energy analysis at 1000 K found CH-O to be the main pathway for CO formation. The competition of DRM and reverse water gas shift (RWGS) is also evidenced with the latter becoming important at relatively low reforming temperatures. Very interestingly oxygen seems to play a key role in making this surface resistant towards coking. From microkinetic analysis we have found greater oxygen surface coverage than that of carbon at high temperatures which may help to oxidize carbon deposits in continuous runs. The tolerance of Ni2P towards carbon deposition was further corroborated by DFT and micro kinetic analysis. Along with the higher probability of C oxidation we identify poor capacity of carbon diffusion on the Ni2P (0001) surface with very limited availability of C nucleation sites. Overall, this study opens new avenues for research in metal-phosphide catalysis and expands the application of these materials to CO2 conversion reactions.
29 citations
TL;DR: In this paper, a novel strategy for bio-methane production and magnesium chloride waste valorization is addressed, which is a potential alternative path to the already existing biogas upgrading technologies by carbon dioxide mineralization into valuable magnesium carbonate.
28 citations
TL;DR: The as prepared catalysts have been tested in a relevant reaction in the field of environmental catalysis such as the reduction of 4-nitrophenol leading to promising results.
Abstract: This work is a detailed study on how to optimize gold colloids preparation and their deposition to very different in nature carbon materials. The change of the continuous phase and its dielectric constant is used to assure the good dispersion of the hydrophilic/hydrophobic carbons and the successful transfer of the preformed small size colloids to their surface. The sintering behavior of the particles during the calcination step is also studied and the optimal conditions to reduce to a minimum the particle size increase during the protecting agent removal phase are found. The as prepared catalysts have been tested in a relevant reaction in the field of environmental catalysis such as the reduction of 4-nitrophenol leading to promising results. Overall, this work proposes an important methodology to follow when a carbonaceous material are selected as catalyst supports for green chemistry reactions.
TL;DR: The results indicate that acceptable precipitation efficiencies between 62 and 93% can be reached by fine tuning the studied parameters, and confirmed the technical feasibility of this alternative biogas upgrading process through CaCO3 production.
TL;DR: In this paper, an innovative route for bio-compounds upgrading via "hydrogen-free" hydrodeoxygenation (HDO) was proposed and evaluated using guaiacol as a model compound in a high-pressure batch reactor.
Abstract: An innovative route for bio‐compounds upgrading via “hydrogen‐free” hydrodeoxygenation (HDO) is proposed and evaluated using guaiacol as a model compound in a high‐pressure batch reactor. Experimental results showed that noble metal supported on activated carbon catalysts are able to conduct tandem multiple steps including water splitting and subsequent HDO. The activity of Ru/C catalyst is superior to other studied catalysts (i.e. Au/C, Pd/C and Rh/C) in our water‐only HDO reaction system. The greater dispersion and smaller metal particle size confirmed by the TEM micrographs accounts for the better performance of Ru/C. This material also presents excellent levels of stability as demonstrated in multiple reciclabylity runs. Overall, the proposed novel approach confirmed the viability of oxygenated bio‐compounds upgrading in a water‐only reaction system suppressing the need of external H2 supply and can be rendered as a fundamental finding for the economical biomass valorisation to produce added value bio‐fuels.
TL;DR: The effect of calcium and magnesium ions in carbonation experiments carried out to regenerate sodium hydroxide from a biogas upgrading unit indicates that calcium is much more prone than magnesium to reach high efficiencies in aqueous Carbonation experiments.
TL;DR: In this paper, the stability and geometries of selected RWGS intermediates on the MoP (0001) surface, in comparison to the Ni2P (0002) surface were investigated.
Abstract: Selective conversion of CO2 to CO via the reverse water gas shift (RWGS) reaction is an attractive CO2 conversion process, which may be integrated with many industrial catalytic processes such as Fischer−Tropsch synthesis to generate added value products. The development of active and cost friendly catalysts is of paramount importance. Among the available catalyst materials, transition metal
phosphides (TMPs) such as MoP and Ni2P have remained unexplored in the context of the RWGS reaction. In the present work, we have employed density functional theory (DFT) to first investigate the stability and geometries of selected RWGS intermediates on the MoP (0001) surface, in comparison to the Ni2P (0001) surface. Higher adsorption energies and Bader charges are observed on MoP (0001), indicating better stability of intermediates on the MoP (0001) surface. Furthermore, mechanistic investigation using potential energy surface (PES) profiles showcased that both MoP and Ni2P were active toward RWGS reaction with the direct path (CO2* → CO* + O*) favorable on MoP (0001), whereas the COOH-mediated path (CO2* + H* → COOH*) favors Ni2P (0001) for product (CO and H2O) gas generation. Additionally, PES profiles of initial steps to CO activation revealed that direct CO
decomposition to C* and O* is favored only on MoP (0001), while H-assisted CO activation is more favorable on Ni2P (0001) but could also occur on MoP (0001). Furthermore, our DFT calculations also ascertained the possibility of methane formation on Ni2P (0001) during the RWGS process, while MoP (0001) remained more selective toward CO generation.
TL;DR: In this article, a series of NiMo/SiO2 catalysts was synthesized by sol-gel method for heavy oil upgrading in supercritical water (SCW), and phenanthrene was used as substrate as it represents polyaromatic structures present in asphaltenes.
TL;DR: In this article, the authors investigated the physico-chemical evolution and oxidative reactivity of solid products of pyrolysis of citrus waste using TGA, TGA-Gravimetric Analysis (TGA), Differential Scanning Calorimetry (DSC), Electron Paramagnetic Resonance (EPR), and Raman spectroscopy.
TL;DR: This exhibition highlights the many uses of bulk gold, which have found use in art, cosmetic metallurgy and architecture, as well as providing its status as the most noble metal.
Abstract: Gold has long held the fascination of mankind. For millennia it has found use in art, cosmetic metallurgy and architecture; this element is seen as the ultimate statement of prosperity and beauty. This myriad of uses is made possible by the characteristic inertness of bulk gold; allowing it to appear long lasting and above the tarnishing experienced by other metals, in part providing its status as the most noble metal.
TL;DR: In this paper, a physicochemical comparison of the solid products obtained from two alternative processes that recycle waste sodium carbonate (Na2CO3) solution, which is produced following the absorption of CO2 in a biogas upgrading unit, is presented.
Abstract: BACKGROUND This paper presents a physicochemical comparison of the solid products obtained from two alternative processes that recycle waste sodium carbonate (Na2CO3) solution, which is produced following the absorption of CO2 in a biogas‐upgrading unit. Chemical regeneration processes offer an attractive alternative to the energetically demanding standard physical methods. In the first process, sodium hydroxide (NaOH) is regenerated as a precipitate from the chemical reaction of Na2CO3 with calcium hydroxide (Ca(OH)2). The second process shows a path to obtain a valuable sodium chloride (NaCl) and Calcium carbonate (CaCO3) rich brine from calcium chloride (CaCl2) acting as a precipitant agent. In both processes, Precipitated Calcium Carbonate (PCC) is obtained as the most valuable by‐product, but with varying properties due to the different origin. RESULTS The purpose of this work is to analyse physicochemically both variations of PCCs obtained and examining the differences between these solid samples in order to determine which method produces more desirable characteristics in the final product. To this end, FTIR, Raman, XRD and SEM were employed as characterization methods. The results reflect that both PCCs have a calcite crystal structure, or morph, being as both PCC products originate from CaCl2 that is more similar to commercial calcium carbonate calcite. CONCLUSION These results confirmed that a pure CaCO3 valuable by‐product can be obtained from a biogas upgrading unit with several industrial applications.
TL;DR: In this paper, the authors proposed various routes to integrate a fossil fuel-based system, such as an oil-refinery, with bio-refining processes aiming to enhance industry productivity.
TL;DR: In this paper, the synthesis and characterisation of a core-shell n-octacosane@silica nano-encapsulated phase change material obtained via interfacial hydrolysis and poly-condensation of tetraethyl orthosilicate in mini-emulsion was reported.
Abstract: This work reports the synthesis and characterisation of a core-shell n-octacosane@silica nano-encapsulated phase-change material obtained via interfacial hydrolysis and poly-condensation of tetraethyl orthosilicate in mini-emulsion. Silica has been used as the encapsulating material because of its thermal advantages relative to synthesised polymers. The material presents excellent heat storage potential, with a measured latent heat varying between 57.1 and 89 kJ∙kg-1 (melting point between 58 and 64°C) and a small particle size (between ~565 and ~227 nm). Degradation of the n-octacosane core starts between 150 and 180°C. Also, the use of silica as shell material gives way to a heat conductivity of 0.796 W∙m-1∙K-1 (greater than that of nano-encapsulated materials with polymeric shell). Charge/discharge cycles have been successfully simulated at low pressure to prove the suitability of the nano-powder as phase-change material. Further investigations will be carried out in the future regarding the use of the synthesised material in thermal applications involving nanofluids.
TL;DR: This work showcases the versatility of nanogold systems supported on Zn-doped ceria when applied in two important environmental processes, the total CO oxidation, and the liquid phase oxidation of glucose to gluconic acid.
Abstract: The present work showcases the versatility of nanogold systems supported on Zn-doped ceria when applied in two important environmental processes, the total CO oxidation, and the liquid phase oxidation of glucose to gluconic acid. In the CO oxidation the suitability of these materials is clearly demonstrated achieving full conversions even at sub-ambient conditions. Regarding the glucose oxidation our materials display high conversion values (always over 50%) and very importantly full or almost full selectivity toward gluconic acid—an added value platform chemical in the context of biomass upgrading routes. The key factors controlling the successful performance on both reactions are carefully discussed and compared to previous studies in literature. To our knowledge this is one of the very few works in catalysis by gold combining liquid and gas phase reactions and represents a step forward in the flexible behavior of nano gold catalysts.
TL;DR: In this article, a systematic study of the thermochemical stability of La0.6Sr0.4Co0.2 Fe0.8O3 and cobalt doped Ce0.9Gd0.1O (fluorite-type) is proposed.
01 Jan 2019
TL;DR: In this article, an integration system approach connecting an oil refinery and a bio-refinery is proposed, which can be connected through various pathways such as on-site power generation, utility systems and syngas production with the feed of refinery residue, bio-oil and other streams.
Abstract: In this work, an integration systems approach connecting an oil refinery and a bio-refinery is proposed. These plants can be connected through various pathways such as on-site power generation, utility systems and syngas production with the feed of refinery residue, bio-oil and other streams. One important pathway that is the focus in this work represents the production of chemicals produced via biomass sources into the petrochemical and transportation industry as valuable products. Focusing on the latter route of integration, the upgrading of Acetone, Butanol and Ethanol produced by sugar fermentation via bacterial species, has been chosen as a pathway to produce valuable products that could be utilised in both the chemical sector and the transportation industry. There is little current literature regarding this upgrading process, making it a relatively novel option of producing valuable products. The reaction systems studied consist of the self-condensation of the alcohols and cross condensation of alcohols and acetone using active metals supported on basic supports as catalysts at high temperatures and pressure in a batch reactor. Moreover, catalysts syntheses were conducted successfully to verify the proposed integration approach. The results have shown an outstanding performance for the catalysts in terms of conversion and selectivity, having conversions as high as 90%. The catalysts have also proven to yield valuable products with broad market options in the chemical Industry. In conclusion, this route has shown promising results in terms of providing valuable C2-C15 products, useful for both the petrochemical industry and the transportation sector while using economically favourable catalysts in comparison with previous studies.