| dc.description.abstract | Propylene is a chemical compound with high value added, widely used in the industry and
usually obtained from petroleum. However, there is the need of the development of alternative
routes for the production of this compound from renewable sources. The use of acetone for
the production of propylene is a good option, because this oxygenated compound can be
obtained by biomass conversion. The use of a one step process also adds an advantage to the
propylene production from acetone, uniting in a single reactor two consecutive reactions:
acetone hydrogenation, followed by dehydration of the formed isopropanol. For this, there are
necessary two catalysts with distinct properties, one containing metallic sites, for
hydrogenation, and another where there are acidic sites, for dehydration. The main objective
of this work is to obtain propylene from acetone in one single step, using Cu/Zn/Al mixed
oxide derived from hydrotalcite-like compounds and acid form of Beta zeolite as catalysts.
For that, the catalysts were obtained by the coprecipitation method at variable pH followed by
calcination, for the mixed oxide, and by hydrothermal synthesis, for the zeolite. The catalysts
were also characterized as their with distinct properties. The hydrogenation and dehydration
reactions have been studied individually and together by varying the catalyst or mixture of
catalysts employed and the composition and flow rate of the feed. First, they were evaluated
the thermodynamic boundaries of the reaction systems in which was observed that the acetone
hydrogenation is strongly limited by the equilibrium and which are the preferential products
of each reaction. For the reaction test, it was used the factorial experimental design, where the
feeding conditions and reaction temperature were varied, and as response variables it was
obtained the composition of the organic fraction at the reactor outlet. In the hydrogenation
reaction, only isopropanol was obtained and the acetone conversion was close to that of
equilibrium. In the dehydration reaction of isopropanol, propylene was preferably formed,
with only small concentrations of diisopropyl ether at low temperatures, being obtained
complete alcohol conversion in some experimental conditions. The complete process of
acetone conversion into propylene was carried out at eleven distinct experimental conditions
and the olefin fraction was up to 65 % of the organic fraction. It was possible the parameters
estimation of simplified kinetic models, considering the Langmuir-Hinshelwood hypothesis,
appropriate to the prediction of the molar fractions of the compounds in the organic fraction
for both individual as simultaneous reactions. The kinetic models were used to the analysis of
the effect of process variables on the reaction products in the three reaction systems
considered. | |
