Catalytic effect of montmorillonite nanoparticles on thermal decomposition of coal tar pitch to carbon

Abstract

The work studies the structure of two types of coal tar pitches (CTPs) modified with montmorillonite (MMT) in the form of nanopowder after annealing to 1000 and 2000 °C. The CTPs differed in polycyclic aromatic hydrocarbons (PAH) content and coking value (CV). The study of scanning electron microscope (SEM), transmission electron microscope (TEM) and x-ray diffraction (XRD) showed that the heat treatment of PAH-containing pitches modified with the ceramic filler to 1000 °C is a way to obtain a new clay-carbon nanocomposite, composed of turbostratic carbon, graphitic carbon, carbon nanotubes (CNT) and MMT. MMT act as a catalyst for carbon nanotubes growth via the gas phase at 1000 °C. Carbon nanotubes growth in pitch-derived carbon material occurred as a result of the presence of hydrocarbon compounds containing PAH evolved during thermal conversion to the carbon phase. Catalytic growth of carbon nanotubes from aromatic hydrocarbons-containing gaseous phase allows to reduce PAH emission during pitch-derived carbon thermal processing.The montmorillonite – modified carbon samples contained a graphitic phase built of preferred orientation crystallites. This phase consisted of well-ordered crystallites with the c-axis spacing, d002 = 0.335 nm. The process occurred due to catalytic graphitization at 1000 °C in the presence of montmorillonite.