Epoxidation of light olefins on titanium silicates

The topic of present work was the epoxidation of light olefins on titanium silicate catalysts. Epoxidation of single olefins (ethene, propene, 1-butene and iso-butene) and mixtures of them were investigated. A material study allowed an extensive comparison of titanium silicate catalysts (TS-1 and Ti-MWW) and active sites, revealing the reactant-catalyst interactions present in the activation of the active titanium sites. The epoxidation of olefins was performed in a laboratory-scale trickle bed reactor operating under transient and stationary states. An extensive set of conditions was screened for each case in these gas-liquid-solid systems. Hydrogen peroxide was the epoxidation agent, while methanol and acetonitrile were used as solvents. The reactants and products were analyzed by gas chromatography. The single olefin epoxidation experiments in the trickle bed reactor revealed the changes in the dynamic behavior depending of the alkene chain length and the molecular structure. The epoxidation of olefin mixtures demonstrated to improve the catalyst stability. Nonetheless, the product selectivity was strongly affected by the number of olefins in the mixtures. Ternary mixtures displayed to be highly selective compared to binary olefin mixtures. The comparison of titanium silicates demonstrated important differences between these otherwise similar materials. Both materials displayed to be active under comparable mild conditions. However, Ti-MWW exhibited a better performance as acetonitrile was used as solvent, allowing a higher selectivity to the epoxide. TS-1 displayed to be more active, nevertheless, the utilization of methanol as the solvent generated a higher concentration of methoxy species as by-products. The analysis of the synthesis conditions of Ti-MWW demonstrated important changes with the calcination temperature. The acidity and surface areas demonstrated to be affected by this synthesis parameter. The analysis of reactant-catalyst interactions indicated differences in the titanium active site response depending on the material. The spectroscopic analysis of the materials was carried out in an ATR-FTIR system allowing the contact of the reactants and the catalyst under controlled conditions. The ex-situ analysis allowed the observation of changes in the framework titanium vibration, and the utilization of in-situ modulation excitation spectroscopy permitted the observation of changes in the vibration due to time dependent concentration gradients. The present study is a broad approach to the epoxidation on titanium silicates, being the reactants, materials and active sites studied. The utilization of transient techniques as step responses demonstrated to be a highly valuable tool to understand the behavior of reactive systems.El tema del presente trabajo fue la epoxidación de olefinas ligeras sobre catalizadores de titanosilicato. Se investigó la epoxidación de olefinas individuales (eteno, propeno, 1-buteno e isobuteno) y mezclas de ellas. Un estudio de materiales permitió una comparación exhaustiva de los titanosilicatos (TS-1 y Ti -MWW) y sus sitios activos, revelando las interacciones reactivocatalizador presentes en la activación de los sitios activos de titanio. La epoxidación de olefinas se realizó en un reactor trickle-bed a escala de laboratorio que operaba en estados transientes y estacionarios. Se evaluó un amplio conjunto de condiciones para cada caso en estos sistemas gas-líquido-sólido. El peróxido de hidrógeno fue el agente de epoxidación y se utilizaron metanol y acetonitrilo como disolventes. Los reactivos y productos se analizaron por cromatografía de gases. Los experimentos de epoxidación de olefinas individuales en el reactor trickle-bed revelaron los cambios en el comportamiento dinámico en función de la longitud de la cadena del alqueno y la estructura molecular. La epoxidación de mezclas de olefinas mejoró la estabilidad del catalizador. No obstante, la selectividad del producto se vio fuertemente afectada por el número de olefinas en las mezclas. Las mezclas ternarias mostraron ser altamente selectivas en comparación con las mezclas de olefinas binarias. La comparación de silicatos de titanio demostró diferencias importantes entre estos materiales por lo demás similares. Ambos materiales mostraron ser activos en condiciones comparables. Sin embargo, Ti-MWW exhibió un mejor desempeño ya que se usó acetonitrilo como solvente, lo que permitió una mayor selectividad al epóxido. TS-1 mostró ser más activo, sin embargo, la utilización de metanol como solvente generó una mayor concentración de especies metoxi como subproductos. El análisis de las condiciones de síntesis de Ti-MWW demostró cambios importantes con la temperatura de calcinación. La acidez y las áreas superficiales demostraron verse afectadas por este parámetro de síntesis. El análisis de las interacciones reactivo-catalizador indicó diferencias en la respuesta del sitio activo de titanio según el material. El análisis espectroscópico de los materiales se realizó en un sistema ATR-FTIR que permite el contacto de los reactivos y el catalizador en condiciones controladas. El análisis ex-situ permitió la observación de cambios en la vibración de titanio presente en la estructura de la zeolita, la utilización de espectroscopia de excitación de modulación in situ permitió la observación de cambios en la vibración debido a gradientes de concentración dependientes del tiempo. El presente estudio es un análisis amplio de la epoxidación sobre titanosilicatos, siendo analizados los reactivos, materiales y sitio activo. La utilización de técnicas transitorias como respuestas escalon demostró ser una herramienta muy valiosa para comprender el comportamiento de los sistemas reactivos.Temat för detta doktorsarbete är epoxiderig av lätta olefiner på titansilikatkatalysatorer. Epoxidering av enskilda olefiner (eten, propen, 1-buten och isobuten) samt blandningar av dem studerades ingående. Undersökning av katalytiska material möjliggjorde en omfattande jämförelse av titansilikatkatalysatorerna TS-1 och Ti-MWW inklusive aktiva säten i dessa material. Dessa studier avslöjade växelverkningar mellan reaktanterna och de aktiva sätena på katalysatorytan. Epoxidering av olefinerna genomfördes i en tricklebäddreaktor som arbetade i laboratorieskala under transienta och stationära betingelser. En omfattande kartläggning gjordes för det komplicerade gas -vätske-fastfassystemet. Alkenerna epoxiderades i metanol- och acetonitrillösningar, där väteperoxid användes som epoxideringsmedel. Reaktanterna och produkterna analyserades med gaskromatografi. Epoxideringsexperimenten av enskilda olefiner i tricklebäddreaktorn visade förändringar i det dynamiska beteendet beroende på alkenens kedjelängd och molekylstruktur. Närvaron av nya produkter bekräftades med hjälp av kromatografisk analys. Epoxidering av olefinblandningar förbättrade katalysatorns stabilitet. Produktselektiviteten påverkades dock starkt av antalet olefiner i reaktionsblandningen. Trekomponentblandningar av olefiner visade sig vara mera selektiva än binära blandningar. En jämförelse av titansilikater avslöjade väsentliga skillnader mellan dessa till synes liknande material. Båda materialen var aktiva under jämförbara milda reaktionsbetingelser. Ti-MWW presterade dock bättre, då acetonitril användes som lösningsmedel och gav en högre selektivitet av epoxider. TS-1 var mera aktiv men användningen av metanol som lösningsmedel ledde till ökad bildning av metoxikomponenter som biprodukter. En analys av syntesbetingelserna för Ti-MWW visade väsentliga förändringar beroende på kalcineringstemperaturen. Katalysatorns surhet och specifika ytarea påverkades av denna syntesparameter. En analys av växelverkningarna mellan reaktanterna och den fasta katalysatorn indikerade skillnader mellan responser som härstammade från aktiva titansäten på katalysatormaterialet. Spektroskopisk analys genomfördes i ett ATR-FTIR-system, vilket möjliggjorde en kontakt mellan reaktanterna och katalysatorn under välkontrollerade betingelser. Med in situ –analys kunde förändringar i vibrationerna i titanramverket observeras och utnyttjandet av moduleringsexcitationsspektroskopi avslöjade förändringar i vibrationerna p.g.a. tidsberoende koncentrationsgradienter. Detta arbete är en bred analys av alkenepoxidering på titansilikater genom att reaktanter, katalysatormaterial och aktiva säten studerades med olika metoder. Användningen av transienta experimentella metoder i form av stegsvar visade sig vara ett synnerligen värdefullt verktyg för en djupare förståelse av reaktiva system

Relación entre funcionalidad motriz y factores antropométricos de riesgo cardio metabólico en bomberos de la región de Valparaíso, Chile

[ES] Objetivo: El objetivo de este estudio fue describir la funcionalidad motriz de bomberos por medio de la batería Functional Movement Screen (FMS), e identificar su relación con factores antropométricos de riesgo cardiovascular (RC). Método: Participaron un total de 139 bomberos, de los cuales 122 corresponden a hombres y 17 a mujeres pertenecientes a 16 compañías de bomberos de la comuna de Valparaíso, Chile. Se aplicó la batería de evaluación FMS y se tomaron medidas de perímetro cintura (PC), índice de masa corporal (IMC) y el índice cintura-estatura (ICE). Resultados: Para las mujeres se reportaron correlaciones bajas entre el FMS y las variables antropométricas de RC, mientras que para los hombres estas correlaciones fueron significativas y negativas entre FMS y las variables PC, ICE e IMC (r = -,37, p < ,001; r = -,34, p < ,001; –-,40, p < ,002), respectivamente. El 64,02% de los participantes en ICE se clasificó en un alto RC (e» ,50) y en el IMC un 73% en las categorías de sobrepeso y obesidad. De acuerdo con los resultados de la evaluación FMS, el 45,33% de los participantes presentan una baja funcionalidad motriz. Conclusión: La baja funcionalidad motriz y los elevados valores en parámetros antropométricos de RC son factores que debería preocupar a comunidades como las compuestas por bomberos, quienes desarrollan labores de alta exigencia física y mental, en condiciones extremas que muchas veces pueden poner en peligro la salud de los propios voluntariosS

Reducing parent-school information gaps and improving education outcomes: Evidence from high-frequency text messages

We conducted an experiment in low-income schools in Chile to test the effects and behavioral changes triggered by a program that sends attendance, grade, and classroom behavior information to parents via weekly and monthly text messages. Our 18-month intervention raised average math GPA by 0.09 of a standard deviation and increased the share of students satisfying attendance requirements for grade promotion by 4.5 percentage points. Treatment effects were larger for students at higher risk of later grade retention and dropout. Leveraging existing school inputs for a light-touch, cost-effective, and scalable information intervention can improve education outcomes in lower-income settings

Epoxidation of Light Olefin Mixtures with Hydrogen Peroxide on TS-1 Catalyst

The direct epoxidation of mixed ethene and propene feedstocks using hydrogen peroxide over a titanium silicalite (TS-1) catalyst was investigated within a continuous trickle bed reactor operating in laboratory scale. Methanol was employed as the reaction solvent. This study aimed to streamline the epoxidation process by obviating the need for prior separation of alkenes, thereby enhancing process efficiency. An extensive array of operational parameters was explored in a trickle bed reactor, encompassing experimental parameters such as temperature, total pressure, hydrogen peroxide concentration, liquid flow rate, and gas composition. In contrast to prior investigations involving separate ethene and propene epoxidation, this study revealed a reduction in epoxide selectivity. The principal by-products observed were methoxy species, formed through the interaction between the epoxide and methanol, resulting in a ring-opening reaction. The influence of water on this ring-opening process was negligible. Notably, the tunability of the system was demonstrated, highlighting low temperature and elevated partial ethene pressure as pivotal factors for augmentingthe epoxide selectivity. The findings suggest that binary olefin mixtures exhibit diminished selectivity but improved stability. This behavior is potentially linked to the olefin solubility in methanol, or alterations in the surface species concentrations, typically associated with catalyst activity variations. These insights offer a valuable foundation for understanding and optimizing the direct epoxidation of mixed ethene and propene feedstock. Graphical Abstract: [Figure not available: see fulltext.]</p

Antifungal Nanoformulation for Biocontrol of Tomato Root and Crown Rot Caused by Fusarium oxysporum f. sp. radicis-lycopersici

Tomatoes (Solanum lycopersicum L.) are the most cultivated and important vegetable crop in the world. These plants can wilt during crop growth due to fusarium wilt (fusariosis), a disease that damages tomato vascular systems. The Fusarium isolated and analyzed in this work correspond to Fusarium oxysporum f. sp. radicis-lycopersici. The isolates were molecularly identified, and analysis was done on the in vitro effects of the nanoemulsions (previously obtained from extracts of Chilean medicinal plants of the genera Psoralea and Escallonia) to inhibit mycelial and conidial germination of the isolates. Subsequently, the nanoemulsions were evaluated under greenhouse conditions for preventive control of fusariosis in the root and crown, with high levels of disease control observed using the highest concentrations of these nanoemulsions, at 250 and 500 ppm

Aqueous phase reforming of birch and pine hemicellulose hydrolysates

Abstract The current work focuses on studying the aqueous phase reforming (APR) of pine and birch hydrolysate obtained from waste wood by using organic acids available from biorefineries. Processing of representative synthetic mixtures was utilized in the work in order to support data interpretation related to the influence of different chemical compound and processing parameters on the APR of the actual hydrolysates. It was shown, that hydrogenation of the hydrolysates prior to APR was not feasible in the presence of formic acid, which ruled out one potential processing route. However, it was successfully demonstrated that birch and pine hydrolysates could be directly processed obtaining close to full conversion. The best results were obtained with tailored bimetallic Pd-Pt/sibunit catalyst in a trickle bed reactor system in the temperature range 175 °C–225 °C

Detecting mood disorder in resource-limited primary care settings: Comparison of a self-administered screening tool to general practitioner assessment

Objectives: Although efficacious treatments for mood disorders are available in primary care, under-diagnosis is associated with under-treatment and poorer outcomes. This study compares the accuracy of self-administered screening tests with routine general practitioner (GP) assessment for detection of current mood disorder. Methods: 197 consecutive patients attending primary care centres in Santiago, Chile enrolled in this cross-sectional study, filling out the Patients Health Questionnaire-9 (PHQ-9) for depression and the Mood Disorder Questionnaire (MDQ) for bipolar disorder, after routine GP assessment. Diagnostic accuracy of these self-administered tools was compared with GP assessment, with gold standard diagnosis established by a structured diagnostic interview with trained clinicians (SCID-I). Results: The sample was 75% female, with a mean age of 48.5 (SD 16.8); 37% had a current mood disorder (positive SCID-I result for depression or bipolar disorder). Sensitivity of the scre