Enhancing light aromatics production by pre-cracking and enriching effect in catalytic pyrolysis of waste polypropylene over encapsulated ZSM-5@SBA-15 composites

A novel approach to warm mix asphalt additive production from polypropylene waste plastic via pyrolysis

Hydrogen and aromatics recovery through plasma-catalytic pyrolysis of waste polypropylene

The effect of seawater aging on the thermal and catalytic pyrolysis of polypropylene (PP) was investigated using a thermogravimetric analyzer and pyrolyzer-gas chromatography/mass spectrometry. Although the surface properties of PP were of the oxidized form by seawater aging, the decomposition temperature and non-catalytic pyrolysis products of PP were relatively unchanged largely due to seawater aging. The catalytic pyrolysis of seawater-aged PP over all the catalysts produced smaller amounts of aromatic hydrocarbons than that of fresh PP due to catalyst poisoning caused by the residual inorganics. Among the catalysts, microporous HZSM-5 (SiO₂/Al₂O₃:23) produced the largest amount of aromatic hydrocarbons followed in order by microporous HY(30) and nanoporous Al-MCM-41(20) from seawater-aged PP due to the high acidity and appropriate pore size for the generation of aromatic hydrocarbons.

The escalating global production of plastics and the depletion of fossil fuel reserves underscore the urgency of sustainable waste-to-energy strategies. This study investigates the staged catalytic pyrolysis of polypropylene (PP), high-density polyethylene (HDPE), and their blends for the production of liquid fuels. Experiments were conducted in a semi-batch reactor at 450 °C (Stage A) and 500 °C (Stage B), with bentonite as catalyst. Product yields and compositions were quantified via mass balance and GC–FID analysis. Results revealed strong feedstock-dependent behaviors: HDPE exhibited superior liquid recovery (81.96% in Stage A, 88.24% in Stage B) with minimal char, whereas PP was prone to higher char and gas formation. Co-pyrolysis demonstrated synergistic effects, with asymmetric mixtures outperforming single-polymer systems. Notably, the 70% PP–30% HDPE blend achieved the highest liquid recovery (95.07%) and lowest gas fraction (4.92%) during secondary cracking, while the 30% PP–70% HDPE blend enhanced diesel- and kerosene-range fractions. GC–FID analysis confirmed that PP favored gasoline-range hydrocarbons, while HDPE enriched middle distillates. The tunability of hydrocarbon distribution through feed composition highlights staged pyrolysis as a robust pathway for transforming mixed plastic waste into targeted fuel-range hydrocarbons. These findings provide actionable insights into optimizing product selectivity and yield, advancing the integration of polyolefin pyrolysis into circular economy and sustainable energy frameworks.

A two-stage process was employed for high yield production of multi-walled carbon nanotubes (MWCNTs) via pyrolysis of polypropylene (PP) waste. In the first stage, a new design was used for the pyrolysis of PP waste at 500 °C to form a mixture of condensable hydrocarbons (≥C6) and non-condensable gases (C1–C5) inside a vertical reactor closed from the bottom and connected directly to a vertical condenser at the top. This pyrolysis technique permitted to form a large amount of non-condensable hydrocarbon gases, which were used in the second stage as a carbon source for the production of MWCNTs over Co-Mo/MgO catalyst. The influences of growth temperature (700–850 °C) and carrier gas flow rate of N2 (50–110 sccm) on the yield and morphology of as-deposited MWCNTs have been investigated. The fresh Co-Mo/MgO catalyst and the as-deposited carbon were characterized by XRD, FTIR, TPR, BET surface properties, TEM, Raman spectroscopy and TGA. The results demonstrated that the adjustment of growth temperature and N2 flow-rate caused a marked impact on the yield, type and quality of as-grown MWCNTs. The optimum MWCNTs yields of 32.6 and 38.3 g/gcatalyst have been achieved at the growth temperature of 800 °C and the carrier gas flow rate of 90 sccm, respectively. TEM images illustrated the formation of pure MWCNTs at the growth temperature range of 700–800 °C, whereas mixed materials of MWCNTs and graphene nanosheets (GNSs) were obtained at the growth temperature of 850 °C. Raman spectroscopy illustrated that highly graphitized and crystalline MWCNTs were produced at all operating conditions. TGA proved that all MWCNTs samples exhibited higher thermal stability.

Recovery of enhanced gasoline-range fuel from catalytic pyrolysis of waste polypropylene: Effect of heating rate, temperature, and catalyst on reaction kinetics, products yield, and compositions

Catalytic pyrolysis of polypropylene over Ga loaded HZSM-5

Thermal decomposition of plastics by pyrolysis into oil is a successful way of treating wastes. Nevertheless, the production of carbon nanotubes (CNTs) from wastes improves the feasibility of the waste management process. An experimental setup was developed to study the influence of different heating rates on the produced oil by pyrolysis of waste polypropylene (WPP), and the influence of using foamed nickel on the produced CNTs as a function of operating temperature and heating rate. Different heating rates of 5, 10, and 20 °C/min were examined, as well as the different carbon vapor deposition (CVD) temperatures of 600, 700, and 800 °C were studied. It has been found that increasing the heating rate from 5 to 20 °C/min increases the oil yield from 59.3 to 71%, but on the other hand it decreases the quality of the oil. It has been also found that increasing the heating rate decreases the quality of CNTs, i.e., uniform CNTs with small diameter and small wall thickness, and as well as the quantity. The physical properties of the produced CNTs have been improved by increasing the CVD temperature; however, the quantity of CNTs decreased. The highest yield of CNTs produced was 43.12% at the lowest CVD temperature and heating rate examined, i.e., 600 and 5 °C/min, respectively. The optimum heating rate and CVD temperature for the pyrolysis of waste polypropylene to achieve the highest quality of CNTs with moderate production of 39.34%, is the lowest heating rate examined, i.e., 5 °C/min, with a moderate CVD temperature of 700 °C.

The objective of this research is to produce oil from the catalytic pyrolysis of waste polypropylene (WPP) using a low-cost natural catalyst. Three natural catalysts were examined, i.e. Kaolin, Hematite, and white sand. Different catalyst-to-plastic ratios were examined, i.e. 1:1, 1:2, 1:4, 1:6, and 1:8. The utilized catalysts were elementally analyzed using the XRF analysis and the surface area was analyzed by the BET multi-point method. The WPP thermal degradation behavior was investigated by the thermogravimetric analysis (TGA), then the generated liquid oil was analyzed using the gas chromatography-mass spectrometry (GC–MS) and the differential scanning calorimetry (DSC). Thermal cracking without a catalyst produced a yield of 70 wt% of liquid oil, and the maximum oil yield in case of using Hematite and white sand as a catalysts were 70 wt% and 68 wt%, respectively. However, the ratio of 1:2 of the Kaolin to the WPP produced the highest oil yield of 80.75 wt%, and the ratio of 1:8 of the white sand to the WPP produced the highest gas yield, i.e. 44 wt%. Using Kaolin in the catalytic pyrolysis of WPP produced oil with the lowest percentage of heavy oils, i.e. 25.98%, and the highest percentage of light oils, which is 25.37%, when compared to other catalysts such as Hematite and white sand. Kaolin has the lowest cost of oil production compared to Hematite and white sand, which is 0.28 $/kg of oil. Kaolin is an economical catalyst that improves the quality, as well as the quantity of the produced oil in comparison to Hematite, white sand and the non-catalytic case.

Controlling Diels-Alder reactions in catalytic pyrolysis of sawdust and polypropylene by coupling CO2 atmosphere and Fe-modified zeolite for enhanced light aromatics production

Polyolefins can be converted into C2-C5 hydrocarbons and benzene-toluene-xylene (BTX) aromatics as high-demand petrochemical feedstocks via catalytic pyrolysis on acidic zeolites. Bro̷nsted and Lewis acid sites are responsible for cracking polyolefins into olefins and subsequent aromatic formation. In this study, we have subjected the parent HZSM-5 zeolite to postsynthetic partial metal exchange with Fe, Co, Ni, Cu, and Ce cations to perturb Bro̷nsted/Lewis acidity. We have investigated these metal-modified HZSM-5 on the catalytic pyrolysis of polypropylene (PP) in a micropyrolyzer connected to a two-dimensional gas chromatograph coupled to a time-of-flight mass spectrometer and flame ionization detector (Tandem Pyrolyzer-GC × GC-TOF-MS/FID setup). Whereas Fe-, Co-, Cu-, and Ce-exchanged zeolites (with 2.5, 2.3, 1.9, and 0.8 wt % metal, respectively) had comparable product yields with the parent zeolite, Ni-exchanged zeolites with Ni content of 0.5 to 2 wt % were associated with enhanced BTX formation (28-38 wt %) compared to that of the parent zeolite (22 wt %). Pyridine-FTIR indicated that the Bro̷nsted/Lewis acid ratio of the parent zeolite decreased upon metal ion exchange. According to Pyridine-TPD, the parent zeolite's medium-strength acid sites were redistributed into weak and strong acid sites in Ni-exchanged zeolites. The higher amount of carbon deposits on Ni-exchanged zeolites compared to the parent and other metal ion exchanged zeolites was attributed to the enhanced aromatization activity by the simultaneous decrease in the Bro̷nsted/Lewis acid ratio and emergence of strong acid sites.

Tailored HZSM-5 catalyst modification via phosphorus impregnation and mesopore introduction for selective catalytic conversion of polypropylene into light olefins

Reaction synergy of bimetallic catalysts on ZSM-5 support in tailoring plastic pyrolysis for hydrogen and value-added product production

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 aim of this study is to convert polypropylene waste into usable liquid fuel via pyrolysis technique using kaolin as a low-cost catalyst. Waste polypropylene was thermally and catalytically degraded in a chemical vapour deposition (CVD) horizontal glass reactor at a temperature of 450 °C, residence time of 30 min, and heating rate of 30 °C/min. The kaolin clay was characterized by XRF analysis while the ultimate and proximate analysis of the polypropylene feed carried out gave combustible materials content of 93.77 wt%, fixed carbon of 1.62 wt%, calorific value of 45.20 MJ/kg and elemental composition with carbon (83.65%), hydrogen (14.27%), oxygen (0.15%), sulphur (0.1%), chlorine (1.16%), and nitrogen (0.67%). Thermal cracking was carried out in the absence of catalyst and the process gave a yield of liquid, gaseous, and solid products of 67.48, 8.85, and 23.67 wt%, respectively. Furthermore, kaolin clay was employed as a catalyst in catalytic pyrolysis of the same feedstock for catalyst-to-plastic ratio of 1:1, 1:2, 1:3, and 1:4 at the same operating parameters as in thermal cracking. Optimum yield was obtained at a catalyst-to-plastic ratio of 1:3 with a yield of 79.85, 1.48, and 18.67 wt% for liquid, gaseous, and solid products, respectively. The liquid products obtained for both thermal and catalytic cracking at optimum conditions were characterized for their suitability as fuel. The properties determined were density, viscosity, flash point, fire point, pour point, and calorific value. The results suggest that catalytic pyrolysis produced liquid products, whose properties are comparable to conventional fuels (gasoline and diesel oil) than that produced through thermal pyrolysis. FTIR analysis of the liquid product from catalytic pyrolysis also shows that it contains hydrocarbons with different functional groups such as aromatics, olefins, carbonyl, amines, sulphides, and hydroxyl.