The catalytic pyrolysis (CP) of different thermoplastics, polyethylene (PE) and polypropylene (PP), over two types of mesoporous catalysts, desilicated Beta (DeBeta) and Al-MSU-F (AMF), was investigated by thermogravimetric analysis (TGA) and pyrolyzer-gas chromatography/mass spectrometry (Py-GC/MS). Catalytic TGA of PE and PP showed lower decomposition temperatures than non-catalytic TGA over both catalysts. Between the two catalysts, DeBeta decreased the decomposition temperatures of waste plastics further, because of its higher acidity and more appropriate pore size than AMF. The catalytic Py-GC/MS results showed that DeBeta produced a larger amount of aromatic hydrocarbons than AMF. In addition, CP over AMF produced a large amount of branched hydrocarbons.

The catalytic co-pyrolysis of a seaweed biomass, Laminaria japonica, and a typical polymer material, polypropylene, was studied for the first time. A mesoporous material Al-SBA-15 was used as a catalyst. Pyrolysis experiments were conducted using a fixed-bed reactor and pyrolysis gas chromatography/mass spectrometry (Py-GC/MS). BET surface area, N₂ adsorption-desorption isotherms, and NH₃ temperature programmed desorption were measured to examine the catalyst characteristics. When only L. japonica was pyrolyzed, catalytic reforming slightly increased the gas yield and decreased the oil yield. The H₂O content in bio-oil was increased by catalytic reforming from 42.03 to 50.32 wt% due to the dehydration reaction occurring on the acid sites inside the large pores of Al-SBA-15. Acids, oxygenates, mono-aromatics, poly aromatic hydrocarbons, and phenolics were the main components of the bio-oil obtained from the pyrolysis of L. japonica. Upon catalytic reforming over Al-SBA-15, the main oxygenate species 1,4-anhydro-d-galactitol and 1,5-anhydro-d-manitol were completely removed. When L. japonica was co-pyrolyzed with polypropylene, the H₂O content in bio-oil was decreased dramatically (8.93 wt% in the case of catalytic co-pyrolysis), contributing to the improvement of the oil quality. A huge increase in the content of gasoline-range and diesel-range hydrocarbons in bio-oil was the most remarkable change that resulted from the co-pyrolysis with polypropylene, suggesting its potential as a transport fuel. The content of mono-aromatics with high economic value was also increased significantly by catalytic co-pyrolysis.

The catalytic pyrolysis of Laminaria japonica was carried out over a hierarchical meso-MFI zeolite (Meso-MFI) and nanoporous Al-MCM-48 using pyrolysis gas chromatography/mass spectrometry (Py-GC/MS). The effect of the catalyst type on the product distribution and chemical composition of the bio-oil was examined using Py-GC/MS. The Meso-MFI exhibited a higher activity in deoxygenation and aromatization during the catalytic pyrolysis of L. japonica. Meanwhile, the catalytic activity of Al-MCM-48 was lower than that of Meso-MFI due to its weak acidity.

High-density polyethylene (HDPE) was co-fed into the catalytic pyrolysis (CP) of mandarin peel (MP) over different microporous catalysts, HY and HZSM-5, with different pore and acid properties. Although the non-catalytic decomposition temperature of MP was not changed during catalytic thermogravimetric analysis over both catalysts, that of HDPE was reduced from 465 °C to 379 °C over HY and to 393 °C over HZSM-5 because of their catalytic effects. When HDPE was co-pyrolyzed with MP over the catalysts, the catalytic decomposition temperatures of HDPE were increased to 402 °C over HY and 408 °C over HZSM-5. The pyrolyzer-gas chromatography/mass spectrometry results showed that the main pyrolyzates of MP and HDPE, which comprised a large amount of oxygenates and aliphatic hydrocarbons with a wide carbon range, were converted efficiently to aromatics using HY and HZSM-5. Although HY can provide easier diffusion of the reactants to the catalyst pore and a larger amount of acid sites than HZSM-5, the CP of MP, HDPE, and their mixture over HZSM-5 revealed higher efficiency on aromatics formation than those over HY due to the strong acidity and more appropriate shape selectivity of HZSM-5. The production of aromatics from the catalytic co-pyrolysis of MP and HDPE was larger than the theoretical amounts, suggesting the synergistic effect of HDPE co-feeding for the increased formation of aromatics during the CP of MP.

Oxidation of biodiesel (BD) obtained from the decomposition of biomass can damage the fuel injection and engine parts during its use as a fuel. The excess heating of vegetable oils can also cause polymerization of the biodiesel. The extent of BD oxidation depends on its fatty acid composition. In this study, an accelerated oxidation test of BDs at 95 °C was investigated according to ASTM D 2274 by applying a long-term storage test for 16 weeks. The density, viscosity, and total acid number (TAN) of BDs increased because of the accelerated oxidation. Furthermore, the contents of unsaturated fatty acid methyl esters (FAMEs), C18:2 ME, and C18:3 ME in BDs decreased due to the accelerated oxidation. The ¹H-nuclear magnetic resonance spectrum of BDs that were obtained from the accelerated high temperature oxidation at 180 °C for 72 h differed from that of fresh BDs. The mass spectrum obtained from the analysis of the model FAME, linoleic acid (C18:2) methyl ester, which was oxidized at high temperature, indicated the formation of dimers and epoxy dimers of linoleic acid (C18:2) methyl ester by a Diels-Alder reaction.

The catalytic co-pyrolysis (CCP) of Kraft lignin (KL) with refuse-derived fuels (RDF) over HZSM-5, Ni/HZSM-5, and NiDHZSM-5 (Ni/desilicated HZSM-5) was carried out using pyrolyzer-gas chromatography/mass spectrometry (Py-GC/MS) to determine the effects of the nickel loading, desilication of HZSM-5, and co-pyrolysis of KL with RDF. The catalysts were characterized by Brunauer–Emmett–Teller surface area, X-ray diffraction, and NH₃-temperature programed desorption. The nickel-impregnated catalyst improved the catalytic upgrading efficiency and increased the aromatic hydrocarbon production. Compared to KL, the catalytic pyrolysis of RDF produced larger amounts of aromatic hydrocarbons due to the higher H/C_eff ratio. The CCP of KL with RDF enhanced the production of aromatic hydrocarbons by the synergistic effect of hydrogen rich feedstock co-feeding. In particular, Ni/DHZSM-5 showed higher aromatic hydrocarbon formation owing to its higher acidity and mesoporosity.