Open Access
Comparative performance of coke oven gas, hydrogen and methane in a spark ignition engine
(Elsevier, 2020) Ortiz Imedio, Rafael; Ortiz, A.; Urroz Unzueta, José Carlos; Diéguez Elizondo, Pedro; Gorri, D.; Gandía Pascual, Luis; Ortiz, I.; Ingeniaritza; Institute for Advanced Materials and Mathematics - INAMAT2; Ingeniería
In this study, coke oven gas (COG), a by-product of coke manufacture with a high volumetric percentage of H2 and CH4, has been identified as auxiliary support and promising energy source in stationary internal combustion engines. Engine performance (power and thermal efficiency) and emissions (NOx, CO, CO2 and unburned hydrocarbons) of COG, pure H2 and pure CH4 have been studied on a Volkswagen Polo 1.4 L port-fuel injection spark ignition engine. Experiments have been done at optimal spark advance and wide open throttle, at different speeds (2000–5000 rpm) and various air-fuel ratios (λ) between 1 and 2. The obtained data revealed that COG combines the advantages of pure H2 and pure CH4, widening the λ range of operation from 1 to 2, with very good performance and emissions results comparable to pure gases. Furthermore, it should be highlighted that this approach facilitates the recovery of an industrial waste gas.
Open Access
In situ synthesis of SERS-active Au@POM nanostructures in a microfluidic device for real-time detection of water pollutants
(American Chemical Society, 2020) Lafuente Adiego, Marta; Pellejero, Ismael; Clemente, Alberto; Urbiztondo, Miguel A.; Mallada, Reyes; Reinoso, Santiago; Pina, María del Pilar; Gandía Pascual, Luis; Institute for Advanced Materials and Mathematics - INAMAT2; Gobierno de Navarra / Nafarroako Gobernua; Universidad Pública de Navarra / Nafarroako Unibertsitate Publikoa
We present a simple, versatile and low-cost approach for the preparation of SERS-active regions within a microfluidic channel 50 cm in length. The approach involves the UV-light-driven formation of polyoxometalate-decorated gold nanostructures, Au@POM (POM: H3PW12O40 (PW) and H3PMo12O40 (PMo)), that self-assemble in situ on the surface of the PDMS microchannels without any extra functionalization procedure. The fabricated LoCs were characterized by SEM, UV-Vis, Raman, XRD and XPS techniques. The SERS activity of the resulting Au@POM–coated lab-on-a-chip (LoC) devices was evaluated in both static and flow conditions using Rhodamine R6G. The SERS response of Au@PW–based LoCs was found superior to Au@PMo counterparts and outstanding when compared to reported data on metal@POM nanocomposites. We demonstrate the potentialities of both Au@POM–coated LoCs as analytical platforms for real time detection of the organophosphorous pesticide Paraoxon-methyl at 10-6 M concentration level.
Open Access
Oak wood extracts applied to the grapevine. An alternative to obtain quality Garnacha wines
(Elsevier, 2018) Jiménez Moreno, Nerea; Moler Cuiral, José Antonio; Urmeneta Martín-Calero, Henar; Suberviola Ripa, Julián; Cibriain Sabalza, Félix; Gandía Pascual, Luis; Ancín Azpilicueta, Carmen; Química Aplicada; Kimika Aplikatua; Institute for Advanced Materials and Mathematics - INAMAT2; Estadística e Investigación Operativa; Estatistika eta Ikerketa Operatiboa
Open Access
Outstanding performance of rehydrated Mg-Al hydrotalcites as heterogeneous methanolysis catalysts for the synthesis of biodiesel
(Elsevier, 2018) Navajas León, Alberto; Campo Aranguren, Idoia; Moral Larrasoaña, Ainara; Echave, Javier; Sanz, Oihane; Montes, Mario; Odriozola, José A.; Arzamendi Manterola, Gurutze; Gandía Pascual, Luis; Química Aplicada; Kimika Aplikatua; Institute for Advanced Materials and Mathematics - INAMAT2
There is still a need for active, selective and stable heterogeneous catalysts for the synthesis of biodiesel. In this work, magnesium-aluminium hydrotalcites with Mg/Al molar ratios within the 1.5–5 range were synthesized by coprecipitation and used as transesterification catalysts for the synthesis of biodiesel. The mixed oxides obtained after calcination recovered the hydrotalcite structure in the form of meixnerite after rehydration in boiling water. The solids were characterized by XRD, TGA, N2 adsorption-desorption, and SEM. Basic properties were assessed by means of Hammett indicators and CO2-TPD. Rehydrated materials with the highest Mg/Al ratios showed some distinctive features: low surface area, well defined flake-like crystals, high basicity and strong basic sites with H_ values above 11. They were also the most active catalysts allowing to achieve 51–75% sunflower oil methanolysis conversion after 8 h of reaction under mild conditions (60 °C, 1 atm), methanol/oil molar ratio of 12 using between 2 and 6 wt% of catalyst. The conversion increased up to 96% (92% fatty acid methyl esters yield) using 2 wt% catalyst and methanol/oil molar ratio of 48. Catalyst leaching was not a serious problem with these solids that could be reutilized maintaining very good activities. A general accordance between solids basic properties and their catalytic performance has been observed. These results are among the best reported in the literature for heterogeneous methanolysis catalysts and have been attributed to the high basicity of the rehydrated solids and the presence of strong and accessible basic sites probably consisting in interlayer hydroxide anions at the edges of the crystals.
Open Access
Rutas y retos para la valorización de biogás
(Universidad Libre (Colombia), 2017) Navarro Puyuelo, Andrea; Reyero Zaragoza, Inés; Moral Larrasoaña, Ainara; Bimbela Serrano, Fernando; Gandía Pascual, Luis; Química Aplicada; Kimika Aplikatua
Las tecnologías de digestión anaerobia para procesar corrientes residuales (fracción orgánica de residuos de vertedero, lodos de estaciones depuradoras de aguas residuales, purines, etc.) han originado un incremento de la producción de biogás. El biogás está compuesto principalmente por metano y dióxido de carbono, aunque contiene otros componentes minoritarios e impurezas que obligan a efectuar tratamientos para su purificación y acondicionamiento. Existen diversas alternativas para el aprovechamiento y la valorización de este gas, como son: su utilización directa en la generación de energía calorífica y/o eléctrica, su conversión a biometano, y la producción de gas de síntesis (H2+CO), que posteriormente permite producir combustibles líquidos y/o compuestos químicos de interés como el metanol. En este trabajo se presenta una revisión general de las alternativas de valorización de biogás, con énfasis en los procesos de reformado catalítico, tales como el reformado seco o con vapor de agua y procesos de reformado combinado incluyendo la oxidación parcial.
Open Access
Experimental study of the performance and emission characteristics of an adapted commercial four-cylinder spark ignition engine running on hydrogen-methane mixtures
(Elsevier, 2014) Diéguez Elizondo, Pedro; Urroz Unzueta, José Carlos; Marcelino Sádaba, Sara; Pérez Ezcurdia, Amaya; Benito Amurrio, Marta; Sáinz Casas, David; Gandía Pascual, Luis; Ingeniería; Ingeniaritza
The use of hydrogen/methane mixtures with low methane contents as fuels for internal combustion engines (ICEs) may help to speed up the development of the hydrogen energy market and contribute to the decarbonization of the transportation sector. In this work, a commercial 1.4 L four-cylinder Volkswagen spark-ignition engine previously adapted to operate on pure hydrogen has been fueled with hydrogen/methane mixtures with 5–20 vol.% methane (29.6–66.7 wt.%). An experimental program has been executed by varying the fuel composition, air-to-fuel ratio (λ), spark advance and engine speed. A discussion of the results regarding the engine performance (brake torque, brake mean effective pressure, thermal efficiency) and emissions (nitrogen oxides, CO and unburned hydrocarbons) is presented. The results reveal that λ is the most influential variable on the engine behavior due to its marked effect on the combustion temperature. As far as relatively high values of λ have to be used to prevent knock, the effect on the engine performance is negative. In contrast, the specific emissions of nitrogen oxides decrease due to a reduced formation of thermal NOx. A clear positive effect of reducing the spark advance on the specific NOx emissions has been observed as well. As concerns CO and unburned hydrocarbons (HCs), their specific emissions increase with the methane content of the fuel mixture, as expected. However, they also increase as λ increases in spite of the lower fuel concentration due to a proportionally higher reduction of the power. Finally, the effect of the increase of the engine speed is positive on the CO and HCs emissions but negative on that of NOx due to improved mixing and higher temperature associated to intensified turbulence in the cylinders.
Open Access
Conversion of a commercial gasoline vehicle to run bi-fuel (hydrogen-gasoline)
(Elsevier, 2012) Sáinz Casas, David; Diéguez Elizondo, Pedro; Sopena Serna, Carlos; Urroz Unzueta, José Carlos; Gandía Pascual, Luis; Ingeniería; Ingeniaritza
Bi-fuel internal combustion engine vehicles allowing the operation with gasoline or diesel and hydrogen have great potential for speeding up the introduction of hydrogen in the transport sector. This would also contribute to alleviate the problem of urban air pollution. In this work, the modifications carried out to convert a Volkswagen Polo 1.4 into a bi-fuel (hydrogen-gasoline) car are described. Changes included the incorporation of a storage system based on compressed hydrogen, a machined intake manifold with a low-pressure accumulator where the hydrogen injectors were assembled, a new electronic control unit managing operation on hydrogen and an electrical junction box to control the change from a fuel to another. Change of fuel is very simple and does not require stopping the car. Road tests with hydrogen fuel gave a maximum speed of 125 km/h and an estimated consumption of 1 kg of hydrogen per 100 km at an average speed of 90 km/h. Vehicle conversion to bi-fuel operation is technically feasible and cheap.
Open Access
Characterization of combustion anomalies in a hydrogen-fueled 1.4 L commercial spark-ignition engine by means of in-cylinder pressure, block-engine vibration, and acoustic measurements
(Elsevier, 2018) Diéguez Elizondo, Pedro; Urroz Unzueta, José Carlos; Sáinz Casas, David; Machín Mindán, Jorge; Arana Burgui, Miguel; Gandía Pascual, Luis; Institute for Advanced Materials and Mathematics - INAMAT2
Abnormal combustion phenomena are among the main hurdles for the introduction of hydrogen in the transportation sector through the use of internal combustion engines (ICEs). For that reason the challenge is to guarantee operation free from combustion anomalies at conditions close to the ones giving the best engine output (maximum brake torque and power). To this end, an early and accurate detection of abnormal combustion events is decisive in order to allow the electronic control unit deciding suitable correcting actions. In this work, an automotive size 4-cylinder 1.4 L naturally aspirated port-fuel injection spark ignition Volkswagen engine adapted to run on hydrogen has been investigated. Three distinct methods (in-cylinder pressure, block-engine vibration and acoustic measurements) have been employed to detect abnormal combustion phenomena provoked through the enrichment of the hydrogen-air mixture fed to the cylinders under a wide range of engine speeds (1000–5000 rpm). It has been found that the high-frequency components of the in-cylinder pressure and block engine acceleration signals obtained after a Fourier transform analysis can be used for very sensitive detection of knocking combustion cycles. In the case of the ambient noise measurements, a spectral analysis in terms of third octave bands of the signal recorded by a microphone allowed an accurate characterization. Combustion anomalies could be detected through more intense octave bands at frequencies between 250 Hz and 4 kHz in the case of backfire and between 8 kHz and 20 kHz for knock. Computational fluid dynamics simulations performed indicated that some characteristics of the engine used such as the cylinder valves dimensions and the hydrogen flow rate delivered by the injectors play important roles conditioning the likelihood of suffering backfire events.
Open Access
Catalytic performance of bulk and Al₂O₃-supported molybdenum oxide for the production of biodiesel from oil with high free fatty acids content
(MDPI, 2020) Navajas León, Alberto; Reyero Zaragoza, Inés; Jiménez Barrera, Elena; Romero Sarria, Francisca; Llorca Piqué, Jordi; Gandía Pascual, Luis; Zientziak; Institute for Advanced Materials and Mathematics - INAMAT2; Ciencias
Non-edible vegetable oils are characterized by high contents of free fatty acids (FFAs) that prevent from using the conventional basic catalysts for the production of biodiesel. In this work, solid acid catalysts are used for the simultaneous esterification and transesterification with methanol of the FFAs and triglycerides contained in sunflower oil acidified with oleic acid. Molybdenum oxide (MoO₃), which has been seldom considered as a catalyst for the production of biodiesel, was used in bulk and alumina-supported forms. Results showed that bulk MoO3 is very active for both transesterification and esterification reactions, but it suffered from severe molybdenum leaching in the reaction medium. When supported on Al₂O₃, the MoO₃ performance improved in terms of active phase utilization and stability though molybdenum leaching remained significant. The improvement of catalytic performance was ascribed to the establishment of MoO₃Al₂O₃ interactions that favored the anchorage of molybdenum to the support and the formation of new strong acidic centers, although this effect was offset by a decrease of specific surface area. It is concluded that the development of stable catalysts based on MoO₃ offers an attractive route for the valorization of oils with high FFAs content.
Open Access
Functionalization of 3D printed ABS filters with MOF for toxic gas removal
(Elsevier, 2020) Pellejero, Ismael; Almazán, Fernando; Lafuente, María; Urbiztondo, Miguel A.; Dobrek, Martin; Bechelany, Mikhael; Julbe, Anne; Gandía Pascual, Luis; Institute for Advanced Materials and Mathematics - INAMAT2; Gobierno de Navarra / Nafarroako Gobernua, PC052-23; Universidad Pública de Navarra / Nafarroako Unibertsitate Publikoa
Acrylonitrile butadiene styrene (ABS) is one of the most extensively used polymer in 3D printing manufacturing due to its competitive thermal and mechanical properties. Recently, a special attention has been devoted to novel ABS composites featuring extra functionalities e.g. in the area of VOC removal. Herein, we report on a facile protocol for the functionalization of 3D printed ABS filters with a MOF (Metal- Organic Framework) material (ZIF-8) targeting the conception of attractive gas filters. The proposed synthesis strategy consists in low temperature ALD (Atomic Layer Deposition) of ZnO on the ABS grid followed by the hydrothermal conversion of ZnO to ZIF-8, both steps being conducted at 60 °C. In such way, the method enables an effective growth of ZIF-8 without altering the stability of the polymeric ABS support. The as-fabricated ABS/ZIF-8 filters offer a promising adsorption behaviour for dimethyl methylphosphonate (~20.4 mg of DMMP per gram of ZIF-8), thus proving their potential for toxic gas capture applications.