ENADE: Researchers in Minnesota have shown that olefins can be produced from vegetable-oil-derived biodiesel

ENADE: Researchers in Minnesota have shown that olefins can be produced from vegetable-oil-derived biodiesel using methods that are more environmentally friendly than conventional methods.

The researchers have shown that soy-based biodiesel can be oxidized to valuable olefins efficiently and fairly selectively. The reaction is conducted in an autothermal catalytic reactor, in which heat is supplied by oxidation reactions, not by external heaters.

To carry out the oxidation process, the Minnesota group uses an automotive fuel injector to spray droplets of biodiesel, which consists of methyl oleate, methyl linoleate, and related compounds, onto the walls of the reactor where the droplets vaporize.

A mixture of the organic material and air is then passed over a catalyst that contains a few percent of rhodium and cerium supported on alumina.

By adjusting the ratio of biodiesel to oxygen (C/O) in the feed stream, the team is able to control the oxidation process and reactor conditions, such as catalyst temperature, and thereby tune the product distribution. For example, at a C/O ratio of roughly 1.3, the reaction yields about 25% ethylene and smaller concentrations of propylene, 1-butene, and -pentene. In contrast, at a C/O ratio of 0.9, the product stream consists mainly of hydrogen and CO. The researchers report that at all C/O ratios, the process yields less than 13% CO2 (an unwanted product). They add that the catalyst remains stable and resists deactivation by carbon buildup even under extreme conditions.

(Adapted from Chemical and Engeneering News, 83(1),10, 2005)

De acordo com o texto acima, é possível concluir:

(A) A transformação do biodiesel em olefinas se passa na ausência de calor.

(B) Combustíveis automotivos foram utilizados na produção de biodiesel.

(D) A composição final da mistura de olefinas é dependente da proporção biodiesel/oxigênio usada como material de partida.

(E) Ao aumentar a proporção de biodiesel em relação ao oxigênio, o produto da reação consiste basicamente de hidrogênio e CO.

QUESTÃO ANTERIOR:

- ENADE: O alumínio é o terceiro elemento mais abundante na crosta terrestre depois do oxigênio e do silício.

RESOLUÇÃO:

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GABARITO:

(D) A composição final da mistura de olefinas é dependente da proporção biodiesel/oxigênio usada como material de partida.