Experimental study of polyethylene pyrolysis and combustion over HZSM-5, HUSY, and MCM-41

Catalytic Pyrolysis of Polypropylene for Cable Semiconductive Buffer Layers

With the progress of the power grid system, the coverage area of cables is widening, and the problem of cable faults is gradually coming to affect people's daily lives. While the vast majority of cable faults are caused by the ablation of the cable buffer layer, polypropylene (PP), as a common cable buffer material, has pyrolysis properties that critically impact cable faults. Studying the semiconductive buffer layer of polypropylene (PP) and its pyrolysis properties allows us to obtain a clearer picture of the pyrolysis products formed during PP ablation. This understanding aids in the accurate diagnosis of cable faults and the identification of ablation events. In this study, the effects of temperature and catalyst (H-Zeolite Standard Oil Corporation Of New York (Socony) Mobil-Five (HZSM-5)) content on the PP thermolysis product distribution were studied by using an online tubular pyrolysis furnace-mass spectrometry (MS) experimental platform. The results showed that PP/40% HZSM-5 presented the highest thermolytic efficiency and relative yield of the main products at 400 °C.

Value-Added Products from Catalytic Pyrolysis of Lignocellulosic Biomass and Waste Plastics over Biochar-Based Catalyst: A State-of-the-Art Review

As the only renewable carbon resource on Earth, lignocellulosic biomass is abundant in reserves and has the advantages of environmental friendliness, low price, and easy availability. The pyrolysis of lignocellulosic biomass can generate solid biochar with a large specific surface area, well-developed pores, and plentiful surface functional groups. Therefore, it can be considered as a catalyst for upgrading the other two products, syngas and liquid bio-oil, from lignocellulosic biomass pyrolysis, which has the potential to be an alternative to some non-renewable and expensive conventional catalysts. In addition, as another carbon resource, waste plastics can also use biochar-based catalysts for catalytic pyrolysis to solve the problem of accumulation and produce fuels simultaneously. This review systematically introduces the formation mechanism of biochar from lignocellulosic biomass pyrolysis. Subsequently, the activation and modification methods of biochar catalysts, including physical activation, chemical activation, metal modification, and nonmetallic modification, are summarized. Finally, the application of biochar-based catalysts for lignocellulosic biomass and waste plastics pyrolysis is discussed in detail and the catalytic mechanism of biochar-based catalysts is also investigated.

Experimental Thermal Hazard Investigation of Pressure and EC/PC/EMC Mass Ratio on Electrolyte

Electrolytes are involved in the thermal runaway (TR) process of cells, which is a potential hazard in lithium-ion batteries (LIBs). Therefore, the effects of different mass ratio of carbonate solvents (ethylene carbonate (EC)/propylene carbonate (PC)/ethyl methyl carbonate (EMC)) with LiBF4 and different environmental pressure on the combustion characteristics of electrolyte such as flame centerline temperature, mass loss rate (MLR) and heat release rate (HRR) were analyzed. The combustion process could be divided into four stages: ignition, stable combustion stage, stable combustion with flame color change stage and extinguishing; with the decrease of pressure, the MLR of electrolyte declined and the combustion time prolonged, while the temperature of flame centerline increased.

Experimental and numerical perspective on the fire performance of MXene/Chitosan/Phytic acid coated flexible polyurethane foam

Recent discoveries of two-dimensional transitional metal based materials have emerged as an excellent candidate for fabricating nanostructured flame-retardants. Herein, we report an eco-friendly flame-retardant for flexible polyurethane foam (PUF), which is synthesised by hybridising MXene (Ti[Formula: see text]) with biomass materials including phytic acid (PA), casein, pectin, and chitosan (CH). Results show that coating PUFs with 3 layers of CH/PA/Ti[Formula: see text] via layer-by-layer approach reduces the peak heat release and total smoke release by 51.1% and 84.8%, respectively. These exceptional improvements exceed those achieved by a CH/Ti[Formula: see text] coating. To further understand the fundamental flame and smoke reduction phenomena, a pyrolysis model with surface regression was developed to simulate the flame propagation and char layer. A genetic algorithm was utilised to determine optimum parameters describing the thermal degradation rate. The superior flame-retardancy of CH/PA/Ti[Formula: see text] was originated from the shielding and charring effects of the hybrid MXene with biomass materials containing aromatic rings, phenolic and phosphorous compounds.

The Use of Heterogeneous Catalysis in the Chemical Valorization of Plastic Waste

Plastic solid waste (PSW) is an ever-growing environmental challenge for our society, as it not only ends up in landfills but also in waterways and oceans and is consequently entering the food chain. A key strategy to overcome this problem while also preserving carbon resources is to use PSW as a feedstock, evolving towards a circular economy. To implement this, mechanical as well as chemical recycling technologies must be developed. Indeed, owing to the high volume of PSW generated each year, mechanical recycling alone is not adequate for addressing this global challenge. Because of this, chemical recycling via thermal and heterogeneous catalytic conversion has received growing attention. This process has the potential to take PSW and convert it into usable monomers, fuels, synthesis gas, and adsorbents under more sustainable conditions than thermal degradation. This Review highlights the recent research advances in catalytic technologies for PSW conversion and valorization.

Different reaction behaviours of light or heavy density polyethylene during the pyrolysis with biochar as the catalyst

Polyethylene is a major contributor of plastic waste, which can be converted into liquid fuel via catalytic pyrolysis. In this study, the pyrolysis of light or heavy density polyethylene (LDPE and HDPE) and their mixture with the biochar produced from gasification of poplar wood as catalyst was investigated. The results showed that, during the co-pyrolysis of LDPE and HDPE in absence or presence of biochar catalyst, cross-interaction of reaction intermediates originated from the degradation of LDPE and HDPE substantially promoted the formation of gaseous products and the evolution of heavy organics with π-conjugated structures in the tar. During the pyrolysis of HDPE, more heavy tar while less wax was produced, while it was contrary during the pyrolysis of LDPE. In the catalytic pyrolysis of LDPE, the volatiles could be effectively cracked over the biochar catalyst, forming more gases, while in the catalytic pyrolysis of HDPE, instead of catalyzing the cracking of the heavy components, the biochar catalyzed the polymerisation reactions. The properties of the biochar catalyst in terms of crystallinity, surface functionality, and internal structures also changed remarkably due to the transfer of oxygen-containing species from the polyethylene to biochar and the interaction of biochar with volatiles in the pyrolysis.

Real time monitoring of slow pyrolysis of polyethylene terephthalate (PET) by different mass spectrometric techniques

In the context of waste upgrading of polyethylene terephthalate (PET) by pyrolysis, this study presents three on-line mass spectrometric techniques with soft ionization for monitoring the emitted decomposition products and their thermal dependent evolution profiles. Pyrolysis experiments were performed using a thermogravimetric analyzer (TGA) under nitrogen atmosphere with a heating rate of 5 °C/min from 30 °C to 600 °C. Single-photon ionization (SPI at 118 nm/10.5 eV) and resonance enhanced multiple photon ionization (REMPI at 266 nm) were used with time-of-flight mass spectrometry (TOF-MS) for evolved gas analysis (TGA-SPI/REMPI-TOFMS). Additionally, the chemical signature of the pyrolysis products was investigated by atmospheric pressure chemical ionization (APCI) ultra high resolution Fourier Transform ion cyclotron resonance mass spectrometry (FT-ICR MS) which enables assignment of molecular sum formulas (TGA-APCI FT-ICR MS). Despite the soft ionization by SPI, the fragmentation of some compounds with the loss of the [O-CH = CH2] fragment is observed. The major compounds were acetaldehyde (m/z 44), benzoic acid (m/z 122) and a fragment of m/z 149. Using REMPI, aromatic species were selectively detected. Several series of pyrolysis products were observed in different temperature intervals, showing the presence of polycyclic aromatic hydrocarbons (PAHs), especially at high temperatures. FT-ICR MS data showed, that the CHO₄ class was the most abundant compound class with a relative abundance of 45.5%. The major compounds detected with this technique corresponded to m/z 193.0495 (C₁₀H₉O₄⁺) and 149.0233 (C₈H₅O₃⁺). Based on detailed chemical information, bulk reaction pathways are proposed, showing the formation of both cyclic monomer/dimer and linear structures.