1,207 research outputs found

    BENZILAÇÃO DO GLICEROL COM AQUECIMENTO POR MICROONDAS

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    A infinidade de aplicações da glicerina incentivou inúmeras pesquisas voltadas ao reaproveitamento do principal coproduto do biodiesel. Destaca-se a produção de aditivos oxigenados para combustíveis, como os éteres, os acetais e os ésteres de glicerina, processos estes que demandam um tempo de reação muito prolongado. Considerando que a aplicação da irradiação de microondas pode influenciar na cinética das reações químicas, o presente trabalho investigou a reação de benzilação do glicerol via catálise homogênea ácida, sob a irradiação de microondas. Foi constatado que o fator variação da potência das micro-ondas apresentou a maior conversão do glicerol dentre todas as variáveis estudadas. Em contrapartida, esta variável também influenciou uma reação indesejável, a autoeterificação do álcool benzílico.Palavras-chave: Benzilação. Glicerol. Álcool benzílico. Microondas.BENZYLATION OF GLYCEROL WITH HEATING BY MICROWAVEAbstract: The multitude of applications of glycerin has encouraged countless researches directed to the reutilization of the main byproduct of biodiesel. Highlighting the production of additives for oxygenated fuels, such as the ethers, the acetal and the esters of glycerin, those processes require a very long reaction time. Whereas the application of irradiation of microwave can influence on the kinetics of chemical reactions, the present work investigated the benzylation reaction of glycerol via catalysis homogeneous acid, in the irradiation of microwave. It was found that the factor power variation of microwave presented the greatest conversion of glycerol among all the variables studied. In contrast, that variable also influenced an undesirable reaction, the self-etherification of benzyl alcohol.Keywords: Benzylation. Glycerol. Benzyl alcohol. Microwave.BENZILACIÓN GLICERINA CON EL CALOR EN MICROONDASResumen: La grande cantidad de aplicaciones de la glicerina ha alentado numerosos estudios dirigidos a la reutilización del principal subproducto de biodiesel. Destacando la producción de aditivos oxigenados de combustibles para motores, tales como éteres, acetales y ésteres de glicerina, estos procedimientos requieren un tiempo de reacción muy largo. Considerando que la aplicación de irradiación de microondas puede influir en la cinética de las reacciones químicas, este estudio investigó la reacción de bencilación de glicerol a través de catálisis homogénea ácida bajo irradiación con microondas. Se encontró que la variación del factor potencia de microondas mostró la mayor conversión de glicerol entre todas las variables evaluadas. En contraste, esta variable también influenció una reacción indeseable, la auto-eterificación de alcohol bencílico.Palabras clave: Bencilación. Glicerol. Alcohol bencílico. Microondas

    Constraints on the χ_(c1) versus χ_(c2) polarizations in proton-proton collisions at √s = 8 TeV

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    The polarizations of promptly produced χ_(c1) and χ_(c2) mesons are studied using data collected by the CMS experiment at the LHC, in proton-proton collisions at √s=8  TeV. The χ_c states are reconstructed via their radiative decays χ_c → J/ψγ, with the photons being measured through conversions to e⁺e⁻, which allows the two states to be well resolved. The polarizations are measured in the helicity frame, through the analysis of the χ_(c2) to χ_(c1) yield ratio as a function of the polar or azimuthal angle of the positive muon emitted in the J/ψ → μ⁺μ⁻ decay, in three bins of J/ψ transverse momentum. While no differences are seen between the two states in terms of azimuthal decay angle distributions, they are observed to have significantly different polar anisotropies. The measurement favors a scenario where at least one of the two states is strongly polarized along the helicity quantization axis, in agreement with nonrelativistic quantum chromodynamics predictions. This is the first measurement of significantly polarized quarkonia produced at high transverse momentum
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