Methanol dehydration over ZrO2 supported-activated carbons

Resumen comunicación congreso internacionalDME is playing an important role due to its potential use as an alternative fuel in diesel engines. The use of this fuel produces lower NOx emissions, and less engine noise compared to traditional diesel fuels. Moreover, this compound is used as building block for many value-added chemicals such as lower olefins. DME is usually produced via catalytic dehydration of methanol over a solid acid. The use of activated carbons in catalytic processes, acting directly as catalyst and as catalyst support, is focussing much attention. They can be obtained from different types of lignocellulosic waste, producing not only an environmental but an economical profit. In this sense, the preparation of activated carbons with phosphoric acid produces catalytic supports with certain surface acidity, which have shown high activity for alcohol dehydration. In this study, ZrO2 supported activated carbons were prepared from an industrial byproduct as lignin for the methanol dehydration to DME. The activated carbon was prepared by chemical activation with H3PO4, using Alcell® lignin as precursor. The impregnation ratio value (H3PO4/lignin) used was 3. The impregnated sample was activated under N2 flow at 500 ºC for 2h, washed and dried. The activated carbon was loaded with different amounts of ZrO(NO3)2, dried at 120ºC for 24h, and calcined in air at 250ºC for 2h, obtaining ZrO2 loadings of 5 and 10%, respectively. For the sake of comparison, pure ZrO2 was also used. Catalytic tests were performed at atmospheric pressure in a fixed bed reactor, at different space times and partial pressures. The activated carbon (ACP) prepared shows a well-developed porous structure, with an apparent surface area higher than 2000 m2/g, and a high contribution of mesoporosity. After metal loading, a maximum decrease of 20% in all structural parameters of the ACP was observed.The results show that ZrO2 loading produces an enhancing in the catalytic activity of the carbon materials compared to the parent activated carbon (0.1 g·s/μmol, PCH3OH= 0.02 atm in helium and 350 ºC). In this sense, a methanol conversion of 25% was observed with the addition of 10% w/w ZrO2 (ACP-10Zr), at steady state conditions (Figure 1). ACP shows negligible conversion, at the same conditions and for pure ZrO2 the methanol conversion was of 10%. Very high selectivity to DME (~100%) was found at temperatures lower than 350 ºC. The methanol conversion increases with temperature, reaching a value of 67% at 475ºC, but a slight decrease in DME selectivity is observed, resulting in a higher production of light hydrocarbons, mainly CH4. The results suggest that the addition of only a 10% of ZrO2 over an activated carbon prepared by chemical activation with H3PO4 enhances significantly the performance of the catalyst, compared to pure ZrO2.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Vocabulary size, reading motivation, reading attitudes and reading comprehension performance among Filipino college learners of english

Reading is an indispensable tool in the academic world. Most, if not all, activities in varied collegiate courses entail the act of reading. There are many contributing factors that affect one’s ability to read and comprehend text materials effectively. Two of the many factors are the reader’s vocabulary size and their reading motivation. This study examined the relationship of the vocabulary size, reading strategies and the reading comprehension performance of college learners in a comprehensive university in the Philippines. A correlational analysis was employed to ascertain the relationship between the scores in the reading comprehension component of the course and the vocabulary levels tests by Nation [1]. The findings of this study hope to provide useful insights into the prediction of college learners’ reading performance and the teaching of vocabulary in the ESL context as well as the integration of learners’ reading motivation in the curriculum

Literacy in Pandemic: Practices, Challenges, and Coping Strategies of MKO’s in Online and Modular Learning Modalities

This paper investigated the literacy practices, challenges, and coping strategies of the More Knowledgeable Others (MKO) in helping the learners accomplish literacy tasks included in the online and modular worksheets during the lockdown period because of COVID-19 pandemic. MKO is a person who has a better understanding or a higher ability level than the learner; this includes the teachers, the parents, and the guardians. This study focused on the parents and guardians as they assume two significant roles during the time of pandemic, namely a teacher and a parent. Two hundred six parents and guardians were surveyed, and selected respondents were requested to participate in the semi-structured interview to provide opportunities to express their experiences during the pandemic. The results revealed that MKO’s practices include their role as a: (1) support in children’s school tasks; (2) spending read aloud time with their children; and (3) their use of Internet and gadgets. For the challenges, four subthemes emerged: (1) duality of roles; (2) lack of knowledge and skills; (3) Internet connectivity; and (4) financial challenges. With the challenges come MKO’s coping strategies: (1) managing time wisely; (2) they provide unfathomable moral support; and (3) their faith in God. With the findings, this paper recommends creation of consultative body among parents so they can be included in the curriculum design for the education of their children

Alcohol decomposition on basic/acid lignin-derived submicron diameter carbon fibers

The use of lignin, the second most abundant polymer in nature, along with a simple and versatile technique, electrospinning, represents an advantageous and promising approach for the preparation of carbon fibers. In previous studies, we have demonstrated that the incorporation of H3PO4 to the initial lignin solution allows for shortening the carbon fibers preparation process and that the resulting carbon fibers present P-surface groups that are of great interest for heterogeneous catalysis. Different carbon fibers catalysts have been prepared by electropinning of Alcell lignin in the absence or presence of H3PO4 as chemical activating agent. Carbonization at different temperatures between 500 and 1600 ºC allows for preparing carbon fibers with a high variety of porosity and chemical surface properties. Diverse oxygen surface groups are presented on the carbon catalysts surface. The isopropanol decomposition has been used as a catalytic test to study the acid or basic character of the prepared carbon fibers. Carbon fibers without phosphorus surface groups generate acetone as the main product of the isopropanol decomposition reaction, from 400 to 600 ºC, suggesting the basic character of these catalysts. On the contrary, phosphorus-containing carbon fibers show high acid character, producing selectivity to propylene of 100 % at temperatures between 250 and 350 ºC. The most acid carbon fiber catalyst produced a high selectivity to ethylene and dimethyl ether for the decomposition of ethanol and methanol, respectively. The conversion enhancement that the presence of oxygen in the gas phase produced for all these reactions was also studied.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech. MINECO (CTQ2015-68654-R). MINECO (PTA2015-11464-I)

Optoelectronic properties of Quantum Dots for biomedicine and energy-to-light conversion

En les últimes dècades, la nanociència ha sorgit com una nova tecnologia gràcies a la seva versatilitat per ser emprada en diferents camps. Dins d’aquets grup, un dels nanomaterials més prometedors, els punts quàntics han estat estudiats per la seva extraordinària propietats i la seva versatilitat per utilitzar-los en diferents camps. La present tesis doctoral es centra en la síntesi de diferents punts quàntics, així com en el seu ús en LEDs, cèl·lules solars perovskites i biosensors. S'han sintetitzat tres tipus de punts quàntics: cadmi, perovskites i punts quàntics de carboni. Els dos primers presenten una banda d’emissió estreta i un rendiment quàntic elevat. No obstant, la seva alta toxicitat és un inconvenient que s’ha de tenir en comte. Com alternativa al seu ús, hem sintetitzat punts quàntics fet de carboni. La seva baixa toxicitat i biocompatibilitat és una bona alternativa als nanomaterials que contenen metalls pesants. A més, el material basat en carboni es pot preparar amb productes comuns com ara glucosa o sucrosa i poden ser dissolts en dissolvents no clorats com ara l’etanol o l’aigua. El treball presentat en aquesta tesis es va dur a terme a l'Institut d'Investigació Química de Catalunya (ICIQ) i al centre tecnològic Eurecat de Catalunya, entre març de 2015 i març de 2019.En la última década, la nanociencia se ha convertido en una tecnología novedosa debido a su versatilidad para ser empleada en muchas áreas de investigación. Uno de los nanomateriales más prometedores, los puntos cuánticos coloidales, han sido estudiados en profundidad por su extraordinario optoelectrónico y su versatilidad para usar en diferentes campos. La presente tesis se centra en la síntesis de diferentes puntos cuánticos, así como su uso en LED, células solares de perovskita y biosensores. Se han sintetizado tres puntos cuánticos diferentes: cadmio, perovskita y puntos cuánticos de carbono. Los dos primeros materiales presentan un alto rendimiento cuántico y banda de emisión estrecha. Sin embargo, su alta toxicidad es una inconveniente que se tiene que tener en cuenta. Como alternativa a su uso, sintetizamos puntos cuánticos de carbono. Su baja toxicidad y su biocompatibilidad es una buena alternativa a los nanomateriales que contienen metales pesados. Además, el material a base de carbono se puede preparar utilizando productos de uso diario como azúcar o jugo de naranja y se puede resolver en solventes que no sean de cloro, como etanol o agua. El trabajo presentado en esta tesis se llevó a cabo en el Instituto de Investigación Química de Cataluña (ICIQ) y en Eurecat, el centro tecnológico de Cataluña, entre marzo de 2015 y marzo de 2019.In the last decades, nanoscience has emerged as a novel technology due to its versatility to be employed in many research areas. One of the most promising nanomaterials, colloidal quantum dots have been deeply studied for their extraordinary optoelectronic properties and their versatility in order to use in different fields. The present thesis is focused on the synthesis of different quantum dots as well as their use in LEDs, perovskites solar cells and biosensors. Three different Quantum Dots have been synthetized: cadmium, perovskites and carbon based quantum dots. The first two material present a high quantum yield and narrow emission band. However, their high toxicity is an important drawback. In order to avoid the use of those material we synthetized carbon quantum dots. Their low toxicity and biocompatibility is a good alternative to heavy metal-containing nanomaterials. In addition, carbon based material can be prepared using ordinary products as glucose or sucrose and solved in non-chloro solvents such as ethanol or water. The work discussed in this thesis was carried out at Institute of Chemical Research of Catalonia (ICIQ) and Eurecat the technological center of Catalonia, between March 2015 and March 2019

Reenvisioning the Classroom: Making Time for Students and Teachers to Play

Explores the benefits of play for students and teachers alike in a New York City elementary school that provides students with time to explore their interests through long-term projects of their choosing

High temperature treatments of porous activated carbon

The use of biomass waste for the preparation of activated carbon is of great industrial interest for reducing costs and increasing the sustainability, especially in the field of energy storage. A high temperature treatment is required to obtain a more ordered carbon material, thus increasing its conductivity. However, this high temperature treatment entails as a disadvantage a significant reduction in porosity. Therefore, a method to prepare activated carbons with a high porosity development as well as high conductivity could be of great interest for many applications. The aim of this work is to analyze the possible influence of phosphorus compounds on the physical-chemical properties of different carbon materials thermally treated at relatively high temperatures (1600 ºC). With this goal, it has been prepared activated carbons from different precursors (olive stone, lignin and hemp) and different conformations (powder, fibers and monoliths) by physical and chemical activation, with CO2 and H3PO4, respectively. Once the different activated carbon materials were prepared, they were thermally treated at 1600 ºC under inert atmosphere. The different samples were characterized by N2 and CO2 adsorption at 77 and 273 K, respectively, XPS, XRD and Raman techniques. The oxidation resistance was also evaluated in a thermogravimetric balance. High temperature treatments of activated carbon without the presence of P surface groups produced an important contraction of the porosity (from 900 to 150 m2 g-1). However, temperature treatments of phosphorus-activated carbon allowed for preparing carbon materials with a relatively high structural order and a well-developed porosity (c.a. 1100 m2 g-1), with a significant contribution of mesoporosity. These results suggest that these P-surface groups are responsible for the low contraction observed for the porous structure, avoiding, in a large extent, its collapse.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech. MINECO (CTQ2015-68654-R). MINECO (PTA2015-11464-I)

Flexible and low-cost binderless capacitors based on p- and n-containing fibrous activated carbons from denim cloth wastes

Activated carbon cloths have been prepared from denim cloth wastes (DCWs) through chemical activation with H3PO4. The effect of the H3PO4/DCWs impregnation ratio and the carbonization temperature on the porous texture, the chemical composition, the fibers morphology, and the electrochemical performance has been studied. Low H3PO4/DCWs impregnation ratios lead to flexible and microporous activated carbons cloths, whereas more fragile and rigid activated carbon cloths with higher external surface area are produced upon increasing the amount of H3PO4. The increase in the carbonization temperature allows for obtaining a more ordered and conductive carbon structure. The activated carbon prepared at 900 ºC with a H3PO4/DCWs impregnation ratio of 0.5 (w/w) exhibits the best performance as electric double layer capacitor. This electrode shows a specific surface area of 2016 m2 g-1 and the highest registered gravimetric capacitance (227 F g-1). Moreover, its flexibility minimizes the ohmic resistance of the electrode, thus increasing the feasibility of working at higher current densities than the other synthesized electrodes.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech; MINECO CTQ2015-68654-

Kinetic study of methanol dehydration over Zro2 supported-activated carbons

The growing concerns about climate change and energy consumption have been the driving force in seek of alternative fuels such as DME, mainly produced via methanol dehydration over a solid acid catalyst. The use of activated carbons for this aim has been little studied up to date. Only a few studies can be found in the literature, reporting all of them materials with a low thermal stability of the acid surface groups, which results into a fast deactivation of the catalyst. In this work, the preparation of activated carbons via chemical activation with phosphoric acid, their modification with different ZrO2 loads, and their application as methanol dehydration catalysts have been studied. The catalytic results showed that the best methanol conversion and selectivity towards DME were achieved with the activated carbon prepared with an impregnation mass ratio value (H3PO4 /precursor) of 2 and an activation temperature of 800 ºC, loaded with a 7 % (wt) of ZrO2 . This catalyst exhibits high steady state methanol conversion values even at temperatures as high as 400 ºC (XCH3OH= 80%, 0.1 g·s/μmol, PCH3OH= 0.08 atm in helium), keeping a selectivity to DME higher than 96%. The effect of oxygen in the reaction atmosphere was also analysed. In this sense, an increase of 15 % in the DME yield was obtained when using air instead of helium as reaction atmosphere (350 ºC, 0.1 g·s/μmol, PCH3OH= 0.04 atm). A kinetic study has been carried out on this catalyst in which two mechanisms (Eley Rideal and Langmuir Hinshelwood) for methanol dehydration have been analysed. The models proposed also consider the presence of oxygen in the reaction media.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech. MINECO (CTQ2015-68654-R). MECD (FPU13/02413)