Estudo de Catalisadores Heterogêneos Sintetizados a Partir de Resíduos de Rochas Ornamentais Aplicados Para Obtenção de Biodiesel

Resumo

The processing of ornamental stones generates tons of waste that are either discarded into the environment
or deposited irregularly in landfills, leading to serious environmental problems. This study aimed at
investigating the synthesis of heterogeneous catalysts supported on a porous carbon matrix using ornamental
stone waste as source of calcium and magnesium oxides. Various synthesis routes (coprecipitation, Pechini
method and wet mixing) were explored and all materials were thermally treated at 800 °C for 3 h. The
catalysts were characterized by X-ray diffraction, thermogravimetry, textural analysis, solid-state ²³Na
nuclear magnetic resonance spectroscopy. The catalytic activity of the catalysts was evaluated in the
transesterification reaction of soybean oil with methanol to obtain biodiesel. The ornamental stone waste
used in this work contains 22.6 wt.% of Ca and 9.0 wt.% of Mg, primarily composed of CaMg(CO₃)₂ and
CaCO₃. The catalyst obtained starting from the mixture of NaOH, activated carbon, and ornamental stone
waste in an aqueous suspension is composed of carbon-supported CaO, MgO, and Na₂CO₃ particles, with
an ash content of 88,5% and a specific surface area of 151 m² g^-1, exhibiting a relatively large efficiency
in terms of biodiesel conversion (80%). The results demonstrate the feasibility of using ornamental stone
waste to develop heterogeneous catalysts supported on activated carbon via the proposed synthesis route
to deposit the particles of calcium and magnesium oxides.