Heterogeneous catalysis for biodiesel production via esterification has emerged as a preferred route as it permits to overcome the disadvantages associated to homogeneous catalysis, which presents ...serious drawbacks that affect biodiesel production and increase its costs such as corrosivity, difficult removal, and non-reuse of the catalyst. This study evaluated the esterification of oleic acid (OA) using CoFe
2
O
4
and MnFe
2
O
4
ferrite magnetic nanoparticles (MNPs) coated with sulfonated lignin (SL). SL was synthesized from sugarcane bagasse lignin employing acetyl sulfate (sulfonating agent). Two different proportions of reactants were adopted, obtaining the solids SL5 and SL7.5—posteriorly incorporated into the MNPs. Reaction parameters evaluated were as follows: time (4 and 6 h) and temperature (80 and 100 °C), with other parameters fixed. The catalysts were characterized by XRD, BET method, SEM, TGA, and elemental analysis. The sulfonic group contents were determined by acid–base titration. The conversion of OA into methyl esters was determined by GC–MS and FTIR. Elemental analysis showed that SL5 and SL7.5 have 2.68% of sulfur content by mass and the following minimal molecular formulas C
9
H
10,52
O
5,62
(SO
3
H)
0,18
and C
9
H
10,52
O
5,62
(SO
3
H)
0,17
. XRD and TGA data evidenced that coated MNPs exhibit incorporation percentage of SL higher than 50%, with the best results for CoFe
2
O
4
-SL5 (79.5%) and CoFe
2
O
4
-SL7.5 (78.5%). GC–MS and FTIR data revealed that the highest OA conversions were achieved under 6 h and 100 °C. In addition, CoFe
2
O
4
-SL5 and MnFe
2
O
4
-SL7.5 exhibited the best catalytic performances in the esterification reactions with conversions of OA into fatty acid methyl esters of approximately 80%.
Graphical abstract
This study describes the cellulases (CLS), hemicellulases (HCS), and reducing sugars (RS) production by
Pleurotus ostreatus
PLO6 growth under solid state fermentation (SSF) using stems and leaves ...mixture of
Alstroemeria sp.
(AW) as lignocellulosic (LC) substrate (also named biomass). SSF involved, at the same time, CLS and HCS biosynthesis, and its subsequent action over the substrate in order to obtain RS, which are considered as precursors of bioethanol and other bioproducts. The first stage of this research was performed to verify simultaneous obtaining of hemicellulolytic and cellulolytic enzymes, and RS by means of univariate experimentation (response variables: hemicellulolytic and cellulolytic enzyme activities and RS concentration, factor: time). In this preliminary study,
P. ostreatus
PLO6 was able to synthesize endoglucanases, exoglucanases, β-glucosidases, endoxylanases, β-xylosidases, and RS concurrently. Afterwards, temperature (
T
), substrate concentration (SC), and time (
t
) effects on simultaneous obtaining of hemicellulolytic and cellulolytic enzymes and RS were assessed. A statistical factorial design 2
3
was developed using the same response variables indicated at the preliminary phase. With a significance level of 0.05, temperature was the most significant effect on enzymatic activities (excepting β-xylosidases) and RS production. CLS activities and RS production were maximized at 24 °C, while HCS activities were better at 32 °C. The SC was statistically significant too, when it was maintained at 30%, the CLS (excepting endoglucanases) and HCS production was favorable. The RS highest production was of 44.8 mg·g
−1
(respective to raw AW) and 124.3 mg·g
−1
(respective to cellulose) at 24 °C, 20% of SC and 8 days of SSF.
Graphical abstract
This study assessed bioplastics made from different mass proportions of commercial chitosan and banana plant pseudostem-derived hemicelluloses. The bioplastics were prepared by the casting method and ...characterized for moisture content, water solubility, opacity, water absorption, tensile strength, and thermogravimetric properties. The formulations with hemicelluloses addition showed higher moisture content and water solubility than the chitosan-only bioplastic, the maximum values of these properties (22.3 and 22.4%) were achieved when hemicelluloses were added at the proportion of 10 and 5%, respectively. A positive linear correlation (
r
= 0.86) was found between added hemicelluloses and opacity, with the highest opacity (1.95 mm
−1
) achieved in the formulation with the maximum hemicellulose incorporation. The bioplastics containing hemicelluloses exhibited lower swelling (water absorption) than that made only of chitosan, with the formulation featuring the highest hemicelluloses content showed the lowest swelling (229.2%). A negative linear correlation (
r
= 0.95) was observed between added hemicelluloses and swelling values. The formulation with the highest hemicelluloses content demonstrated statistically significant differences and exhibited the highest tensile strength (18.7 MPa) and Young’s modulus (66.1 MPa). Thermogravimetric analysis revealed four stages of mass loss in the bioplastics. Hemicelluloses addition decreased the temperature at maximum mass loss, and the formulation with the lowest hemicelluloses content showed a higher degradation rate than the others.
This study researched the steam explosion effect catalysed by citric acid and sodium hydroxide on the chemical and structural properties of sugarcane bagasse and on the enzymatic hydrolysis process. ...Chemical and structural characterisation of raw and pretreated biomass was performed by reference methodologies for lignocellulosic materials, FTIR, XRD, TGA and SEM. Enzymatic hydrolysis was performed with a final volume of 20 mL consisting 3% sugarcane bagasse (dry weight), sodium citrate buffer 50 mM (pH = 5.0) and 1 g enzyme/100 g cellulose of Cellic
®
Cetec 3 enzyme complex. The total reducing sugars were determined by a 3,5-dinitrosalicilic acid method. In explosion pretreatment catalysed by citric acid, a biomass was obtained with a lesser amount of hemicelluloses (16.16%), a higher initial degradation temperature and formation of cracks in fibre cell wall. Pretreated bagasse by NaOH steam explosion showed complete destructuring of fibre, lignin removal of 65% and hemicellulosic fraction preservation. Sugarcane bagasse obtained after NaOH steam explosion showed the highest production of reducing sugars (9.07 g L
−1
), which can be attributed to greater exposure of carbohydrate fraction promoted by lignin removal, since these parameters showed a strong negative correlation (r = −0.99, p < 0.05).
Recentemente, a escassez global dos combustíveis fosseis, além de questões políticas, econômicas e ambientais impulsionaram a busca por combustíveis oriundos de fontes renováveis. Neste contexto, o ...biodiesel surge como um promissor combustível sucedâneo ao diesel mineral, seja parcial ou totalmente. O Brasil é o segundo maior produtor e consumidor mundial de biodiesel, sendo que o sebo bovino é o segundo insumo mais utilizado para a produção deste biocombustível no país, atrás apenas da soja. Diante disso, este artigo de revisão bibliográfica aborda as principais vantagens e limitações relacionadas ao uso desta matéria-prima para obtenção de biodiesel no Brasil, destacando fatores econômicos e ambientais, suas características físico-químicas, além de aspetos relativos à sua cadeia produtiva.
El objetivo de este artículo es presentar los resultados de investigación sobre las posibles alternativas locales de mitigación, que se pueden aplicar para aminorar los efectos del cambio ...climático, a partir de la cuantificación de Gas Efecto Invernadero (GEI) en fincas ganaderas lecheras altoandinas, ubicadas en la zona suroccidental en los municipios de Cumbal y Guachucal, por encima de los 2.800 metros sobre el nivel del mar (m.s.n.m.) en el departamento de Nariño (sur de Colombia). Se partió de un análisis clúster para identificar grupos de fincas con características similares; de cada grupo resultante se escogió una Finca Tipo (FT) y una Finca Replica (FR) para su caracterización socioeconómica y biofísica, con 18 variables que incluyeron el inventario de ganado en cada una de ellas. Se realizó así la estimación anual de GEI con metodologías IPCC nivel 1, a partir de fuentes de emisiones de GEI como: Dióxido de Carbono, Metano, Oxido Nitroso, entre otros. Gracias a los valores obtenidos para los dos municipios de estudio (0,247 ton-c-año para Cumbal, y 0,340 ton-c-año para Guachucal) y, teniendo en cuenta las tipologías generadas: Fincas Ganaderas Lecheras Grandes (FGLG), Fincas Ganaderas Lecheras Medianas (FGLM) y, Fincas Ganaderas Pequeñas (FGLP), se proponen alternativas de mitigación, basadas en el mejoramiento de la alimentación con el ensilaje, picado, bloques nutricionales y manejo de estiércoles, a través de compostaje y biodigestores que pueden reducir más de la mitad de las emisiones actuales.Â
Objetivo: describir los resultados obtenidos en las pruebas de funcionamiento del prototipo Instrumento de Medición Olfatoria. Método: estudio cuantitativo, no experimental y con alcance descriptivo. ...Participaron 60 personas, hombres y mujeres con edades entre 18 a 61 años, en Facatativá y Madrid, Colombia. Las respuestas de los participantes frente a la percepción que tuvieron del cambio, el reconocimiento del nombre o la categoría y la intensidad de las fragancias se registraron en un cuestionario virtual hecho en Google Forms. Para el análisis de datos se utilizó el programa Letrap 5. Resultados: un 83 % de la muestra percibió el cambio de olor; para el reconocimiento se encontró que, en promedio, se identificaron 6 de las 13 fragancias presentadas, y en cuanto a la intensidad la puntuación promedio en toda la prueba fue 2,2 que se identificaron como olores moderados. Conclusiones: el prototipo parece funcionar en relación con las características propuestas para la percepción al cambio de fragancia y el reconocimiento de las fragancias. No obstante, se evidenció dificultad en la percepción de la intensidad de la fragancia.
The rare-earth-free MnAlC alloy is currently considered a very promising candidate for permanent magnet applications due to its high anisotropy field and relatively high saturation magnetization and ...Curie temperature, besides being a low-cost material. In this work, we presented a simple fabrication route that allows for obtaining a magnetically enhanced bulk
-MnAlC magnet. In the fabrication process, an electric arc-melting method was carried out to melt ingots of MnAlC alloys. A two-step solution treatment at 1200 °C and 1100 °C allowed us to synthesize a pure room-temperature
-MnAlC ingot that completely transformed into
-MnAlC alloy, free of secondary phases, after an annealing treatment at 550 °C for 30 min. The Rietveld refinements and magnetization measurements demonstrated that the quenched process produces a phase-segregated
-MnAlC alloy that is formed by two types of
-phases due to local fluctuation of the Mn. Room-temperature hysteresis loops showed that our improved
-MnAlC alloy exhibited a remanent magnetization of 42 Am
/kg, a coercive field of 0.2 T and a maximum energy product, (BH)
, of 6.07 kJ/m
, which is higher than those reported in previous works using a similar preparation route. Experimental evidence demonstrated that the synthesis of a pure room-temperature
-MnAlC played an important role in the suppression of undesirable phases that deteriorate the permanent magnet properties of the
-MnAlC. Finally, magnetic images recorded by Lorentz microscopy allowed us to observe the microstructure and magnetic domain walls of the optimized
-MnAlC. The presence of magnetic contrasts in all the observed grains allowed us to confirm the high-quality ferromagnetic behavior of the system.
PDF
