Thermocatalytic Degradation Research Articles

Thermal conversion of irradiated LLDPE waste into sustainable sponge-like compounds: a novel approach for efficient trace-level oil–water removal

The newest method for recycling waste linear low-density polyethylene (LLDPE) is the thermo-catalytic degradation technique known as catalytic pyrolysis. Typically, it is limited by 500–800 °C high temperatures. Catalytic pyrolysis releases toxins and forms harmful carbonized char. The current study is based on exposing wasted LLDPE to different gamma irradiation doses and then pyrolysis in castor oil (150–300 °C). The output product of Ir-(rLLDPE) is turned into another compound with a new structural architecture (sponge-like). SEM analysis confirms conversion, showing sponge-like spicules and layers. Ir-(rLLDPE) is sponge-like with a soft, malleable, absorbent texture. The DSC demonstrates altered thermal properties, with a melting point at 121 °C splitting into two peaks (endothermic at 117 °C and exothermic at 160 °C). The exothermic peaks signify the curing process of the sponge-like material. Ir-(rLLDPE) is assessed as an adsorbent for aqueous oils and solvents. The study examines irradiation doses, pyrolysis temperature, and time on adsorbent capacity. The oil removal obeys the Langmuir isotherm with monolayer adsorption, with a maximum adsorption capacity of 24.75 g/g of waste oil and 43 g/g of 1,1,2,2-tetrachloroethane. Squashing maintains adsorption after 20 reuses. Data shows sponges effectively clean marine oil spills and solvents.

Thermocatalytic Degradation of Gaseous Formaldehyde Using Transition Metal-Based Catalysts.

Formaldehyde (HCHO: FA) is one of the most abundant but hazardous gaseous pollutants. Transition metal oxide (TMO)-based thermocatalysts have gained much attention in its removal due to their excellent thermal stability and cost-effectiveness. Herein, a comprehensive review is offered to highlight the current progress in TMO-based thermocatalysts (e.g., manganese, cerium, cobalt, and their composites) in association with the strategies established for catalytic removal of FA. Efforts are hence made to describe the interactive role of key factors (e.g., exposed crystal facets, alkali metal/nitrogen modification, type of precursors, and alkali/acid treatment) governing the catalytic activity of TMO-based thermocatalysts against FA. Their performance has been evaluated further between two distinctive operation conditions (i.e., low versus high temperature) based on computational metrics such as reaction rate. Accordingly, the superiority of TMO-based composite catalysts over mono- and bi-metallic TMO catalysts is evident to reflect the abundant surface oxygen vacancies and enhanced FA adsorptivity of the former group. Finally, the present challenges and future prospects for TMO-based catalysts are discussed with respect to the catalytic oxidation of FA. This review is expected to offer valuable information to design and build high performance catalysts for the efficient degradation of volatile organic compounds.

Kinetic Analysis of Thermal Degradation of Recycled Polypropylene and Polystyrene Mixtures Using Regenerated Catalyst from Fluidized Catalytic Cracking Process (FCC).

The pyrolysis process is a thermochemical recycling process that in recent years has gained importance due to its application in plastic waste, which is one of the biggest environmental problems today. Thus, it is essential to carry out kinetic and thermodynamic analyses to understand the thermocatalytic degradation processes involved in plastic waste mixtures. In this sense, the main objective of this study is to analyze the degradation kinetics of the specific mixture of polypropylene (25%) and polystyrene (75%) with 10% mass of regenerated FCC catalyst which was recovered from conventional refining processes using 3 heating rates at 5, 10 and 15 K min-1 by thermogravimetric analysis (TGA). The obtained TGA data were compared with the isoconversional models used in this work that include Friedman (FR), Kissinger Akahira Sunose (KAS), Flynn-Wall-Ozawa (FWO), Starink (ST) and Miura-Maki (MM) in order to determine the one that best fits the experimental data and to analyze the activation energy and the pre-exponential factor; the model is optimized by means of the difference of minimum squares. Activation energy values between 148 and 308 kJ/mol were obtained where the catalytic action has been notorious, decreasing the activation energy values with respect to thermal processes.

Accelerated Thermo-Catalytic Degradation of Perfluoropolyether (PFPE) Lubricants for Space Applications

Perfluoropolyethers (PFPE) are a class of frequently used lubricants in space applications due to their high stability under demanding conditions. However, they are susceptible to aging, with the aging mechanism being dependent on the specific material combination and storage condition. A Lewis-acid-induced thermo-catalytic degradation mechanism is of concern, for example, under steel-on-steel sliding contact, and can be relevant for long-term storage (LTS). Accelerated aging experiments were performed on Fomblin® Z25 and Krytox™ 143AC to investigate thermal stability under the influence of iron(III) fluoride (FeF3) at elevated temperatures (180 °C, 200 °C, and 220 °C) up to a total duration of 2000 h. The degradation effects were monitored via selected analysis techniques: mass loss of the samples due to degradation and subsequent evaporation during aging, FTIR spectroscopy to investigate changes to the chemical structure, dynamic viscosity measurements for the investigation of a potential impact due to changes in molecular mass, and a ball-on-disc tribological test setup to obtain friction behavior of the aged lubricants. Distinct differences between the two types of PFPE lubricants regarding stability to thermo-catalytic degradation were found. Fomblin® Z25 was highly affected by the presence of FeF3 within the selected aging conditions, exhibiting high mass loss, a significant drop in dynamic viscosity, and an increased coefficient of friction due to degradation reactions.

Kinetic and mechanistic investigations of the oxidation of organics by near-infrared light driven thermocatalytic activation of peroxydisulfate with Fe3O4

The utilization of renewable solar energy through near-infrared (NIR)-driven photothermal catalysts offers a potential novel strategy for environmental remediation. In this work, we reported an initial demonstration of the peroxydisulfate (PDS) activation in oxidative degradation of organics (represented by bisphenol A (BPA)) via a unique NIR light-to-heat conversion effect using cost-effective and biocompatible nanoparticles (NPs). The systematical investigation of the photothermal experiments found that Fe3O4 magnetic NPs exhibit great photothermal conversion efficiency (65.4%) and have the capability to quickly elevate the system temperature to 61°C. The increased reaction temperature leads to the homolytic fission of the OO bond for producing sulfate radical (SO4−) and the derivative hydroxyl radical (OH), as confirmed by the radical quenching and electron paramagnetic resonances (EPR) tests, and in turn accelerates the thermocatalytic degradation reaction of BPA. The BPA degradation reaction rate of the NIR/Fe3O4/PDS system is about 25.8 times and 9.4 times of that in the NIR/PDS and Fe3O4/PDS systems, respectively. Both photothermal heating and surface valence states conversion of Fe2+/Fe3+ on Fe3O4 under dark conditions make a contribution to the observed oxidation reactions. Moreover, this NIR light-to-heat activation system exhibits efficient photocatalytic degradation of BPA molecules in deep water by virtue of the deep penetration capability of NIR light in water, highlighting NIR-driven photothermal catalysts hold the excellent potential to be applied in practical water restoration through PDS activation.

Kinetic study for thermocatalytic degradation of waste mixed cloth over antibiotic residue derived carbon-based solid acids

In the present study, the kinetics for waste mixed cloth (WMC) pyrolysis over antibiotic residue derived carbon-based solid acids was investigated for the first time. The kinetic parameters for direct pyrolysis and WMC catalyzed pyrolysis were calculated through isoconvertional method, and different types of mechanism function models were employed to elucidate the catalytic pyrolysis process of WMC. Meanwhile, the most suitable pyrolysis mechanism model was determined by matching the apparent activation energy (Ea). From the kinetical results, the carbon-based solid phosphoric acids significantly reduced the Ea of the main reaction of WMC pyrolysis, which significantly decreased from 366.79 ∼ 434.26 kJ/mol to 141.07 ∼ 184.85 kJ/mol. The matching of mechanistic models confirmed that the catalytic reaction largely depended on both phase boundary control and diffusion control, which corresponded to the interaction of the primary pyrolysis products with the outer surface and inner acidic sites from carbon-based solid acids, respectively. The more acidic sites on the outer surface of the catalyst, the better its catalytic pyrolysis kinetic process matches the phase boundary-control model. This kinetical investigation will provide a promising reference for the rational design of carbon-based solid acids in WMC pyrolysis, with the aim of realizing the high-value utilization of organic solid wastes.

Reusable and highly stable MoS[formula omitted] nanosheets for photocatalytic, sonocatalytic and thermocatalytic degradation of organic dyes: Comparative study

The presence of emerging pollutants in industrial wastewater is a global problem and requires appropriate treatment techniques. Herein, reusable, stable and highly efficient MoS2 nanosheets are prepared via a one-step hydrothermal process. The prepared MoS2 nanosheets are proposed as an environmentally friendly catalyst for treating polluted waters. The comparative effectiveness of the photocatalytic, sonocatalytic, and thermocatalytic degradation processes for the elimination of Rhodamine B (RhB) is investigated. The morphology, composition, and optical properties of the prepared MoS2 nanostructure are characterized using different tools. The vertically aligned MoS2 nanosheets are confirmed by TEM. Moreover, the D-spacing of the nanosheets and corresponding band gap are found to be 0.6 nm and 1.19 eV, respectively. The remarkable catalytic degradation performance of MoS2 nanosheets via the three advanced oxidation processes (AOPs) is attributable to its two-dimensional stacked layers. By using various active species traps, it is proven that the superoxide anion is the major reactive species in the photocatalytic and sonocatalytic degradation of RhB dye. In the case of the thermocatalytic process, holes have the main role. Maximum catalytic efficiency over MoS2 nanosheets is observed with removal percentages of 100 %, 100 % and 80 % after 15 min for photocatalytic, sonocatalytic, and thermocatalytic degradation, respectively. Moreover, the dye degradation and mineralization are confirmed by high COD removal. The MoS2 nanosheets showed high chemical stability after recycling. Consequently, these hydrothermally prepared MoS2 nanosheets can be considered as a promising catalyst for the degradation of emerging pollutants from an aqueous solution.

THERMOLYSIS OF MEDICAL PLASTIC WASTES USING ZEOLITE A CATALYST-KINETIC STUDY, EXPERIMENTAL OPTIMISATION AND VALIDATION

This work reports the thermo-catalytic conversion of medical plastic wastes to fuel oil using the detergent grade Zeolite A as the catalyst. The effect of catalyst on the pyrolysis is ascertained from the kinetic data obtained from thermogravimetric analysis assuming it to be a first-order reaction. A significant reduction in activation energy of the thermal degradation reaction is found in presence of the Zeolite A catalyst. The pyrolysis runs were performed at different temperatures from 400–550 °C in a stainless-steel batch reactor system to obtain an optimum condition for suitable waste to energy process. The highest oil yield of 79% was obtained at 500 °C with 10% catalyst concentration. The thermogravimetric analysis and the batch pyrolysis experimental result indicated a promising effect of the catalyst in terms of the enhanced rate of reaction and conversion. The oil fraction obtained in the optimum condition of catalytic pyrolysis was analysed for its composition and fuel properties. It confirmed the presence of branched alkane and alkene with composition C10–C18. Again, the fuel properties of the oil such as specific gravity (0.793), viscosity (3.75Cst@ 30 °C), and flash point (<11 °C) resemble that of the petro fuels. Neural Networks (NNs) are used to recognize patterns, and relationships in data and validate the experimental results of this reaction and the results indicate that the use of ANN in thermo-catalytic degradation of medical waste to fuel oil is a feasible option that should be considered for real-time applications.

Conversion of Polypropylene Waste into Value-Added Products: A Greener Approach.

Plastic has made our lives comfortable as a result of its widespread use in today’s world due to its low cost, longevity, adaptability, light weight and hardness; however, at the same time, it has made our lives miserable due to its non-biodegradable nature, which has resulted in environmental pollution. Therefore, the focus of this research work was on an environmentally friendly process. This research work investigated the decomposition of polypropylene waste using florisil as the catalyst in a salt bath over a temperature range of 350–430 °C. A maximum oil yield of 57.41% was recovered at 410 °C and a 40 min reaction time. The oil collected from the decomposition of polypropylene waste was examined using gas chromatography-mass spectrometry (GC-MS). The kinetic parameters of the reaction process were calculated from thermogravimetric data at temperature program rates of 3, 12, 20 and 30 °C·min−1 using the Ozawa–Flynn–Wall (OFW) and Kissinger–Akahira–Sunnose (KAS) equations. The activation energy (Ea) and pre-exponential factor (A) for the thermo-catalytic degradation of polypropylene waste were observed in the range of 102.74–173.08 kJ·mol−1 and 7.1 × 108–9.3 × 1011 min−1 for the OFW method and 99.77–166.28 kJ·mol−1 and 1.1 × 108–5.3 × 1011 min−1 for the KAS method at a percent conversion (α) of 0.1 to 0.9, respectively. Moreover, the fuel properties of the oil were assessed and matched with the ASTM values of diesel, gasoline and kerosene oil. The oil was found to have a close resemblance to the commercial fuel. Therefore, it was concluded that utilizing florisil as the catalyst for the decomposition of waste polypropylene not only lowered the activation energy of the pyrolysis reaction but also upgraded the quantity and quality of the oil.

Kinetic Study for Thermocatalytic Degradation of Waste Mixed Cloth Over Carbon-Based Solid Acids

Kinetic Study for Thermocatalytic Degradation of Waste Mixed Cloth Over Carbon-Based Solid Acids

Abatement of oil residues from produced water using a thermocatalytic packed bed reactor

Produced water is a major waste and environmental concern in the oil and gas industry, since it contains dispersed oil and dissolved compounds, which may harm the aquatic environment. Thus, focus on the offshore treatment of the produced water is required. Current methods include hydrocyclones and water clarifiers that cannot achieve full abatement of the oily contaminants. Here we propose a novel thermocatalytic degradation of the dispersed oil using a thermocatalyst, namely Sr0.85Ce0.15FeO3 perovskite that benefits from the thermal energy contained in the produced water, which has temperatures of 40–50 °C when reaching the cleaning phase. It is found that the oil is removed faster with higher perovskite concentrations, and the initial removal is mainly adsorption to the perovskite surface followed by catalytic degradation. Based on batch testing, a lab-scale packed bed reactor (PBR) is modelled showing that oil can be continuously removed by sufficient residence time in the reactor.

Tailor made CuO/ZIF-8 hybrid structure as a potential candidate for thermocatalytic degradation of nitrocellulose

CuO/ZIF-8 hybrid structure was obtained by adding the PVP-modified foliaceous CuO microstructures during the preparation of ZIF-8 polygon particles as a promising candidate for promoting the thermolysis process of NC. Thermoanalysis and pyrolysis kinetics based on the DSC and TG/DTG data revealed that the CuO/ZIF-8-NC decomposition had a weightlessness rate of 77.81%, heat release of 2882.5 J⋅g–1, the exothermic peak temperature of 471.25 K, and activation energy of 172.2 ± 16.0 kJ⋅mol–1, indicating that CuO/ZIF-8 has better catalytic activity than CuO and ZIF-8. The reconstructed nth-order kinetic models for NC/catalysis complexes were obtained using a modified fitting algorithm based on the results of isoconversional kinetic analysis, indicating that CuO/ZIF-8, CuO, and ZIF-8 had different catalytic effects on the thermolysis pathways of NC. This study suggests that CuO/ZIF-8 composite may have prospective application as a high potential and unique catalyst for accelerating NC pyrolysis.

Thermocatalytic degradation of lignin monomer coniferyl aldehyde by aluminum–boron oxide catalysts

Thermocatalytic degradation of lignin monomer coniferyl aldehyde by aluminum–boron oxide catalysts

Thermocatalytic degradation of common polymers: A microscale combustion calorimetry study

This paper presents the first application of the microscale combustion calorimetry (MCC) to study catalyzed pyrolysis of the practical polymers comprising most of currently produced plastic wastes. The polymers considered include olefines (HDPE, LDPE, and PP), PS, PMMA, PET, PC, and PVC. Each of the polymers is mixed with one of the two catalysts, ZSM-5 or MgO, and the measurements are undertaken for the catalyst mass fractions of 0.1, 0.2, and 0.3 at several heating rates ranging from 15 to 60 K/min. Strong catalytic effect of ZSM-5 has been demonstrated for the polyolefin polymers (HDPE, LDPE, and PP). Such effect manifests itself in a significant reduction of characteristic pyrolysis temperatures and apparent activation energy; the latter is shown to decrease greatly (by a factor of about two) when the catalyst is added. As the catalyst mass fraction increases up to 0.1 (0.2 for LDPE + ZSM-5 mixture), the saturation is attained, and further addition of the catalyst has no effect. The heat of combustion of pyrolysis volatiles does not reveal a definitive dependence on the catalyst mass fraction, while in some cases the width of pyrolysis temperature interval as well as the char yield are affected. Decomposition of the remaining polymers in presence of ZSM-5 or MgO is either catalyzed rather weakly or even inhibited such as that in PS + ZSM-5 mixture. Among the polymers examined, PC turns out to be the only polymer that is considerably catalyzed by MgO. For the mixtures in which significant catalytic effect was detected, the formal kinetic models have been derived from the microscale measurements and shown to replicate the MCC data at different heating rates. These polymers, both individually and mixed with the catalyst, are often characterized by the non-monotonic conversion function which cannot be approximated by the n-th order reaction model.

Influence of tailored CuO and Al/CuO nanothermites on the thermocatalytic degradation of nitrocellulose and combustion performance of AP/HTPB composite propellant

Influence of tailored CuO and Al/CuO nanothermites on the thermocatalytic degradation of nitrocellulose and combustion performance of AP/HTPB composite propellant

Evaluation of the Synthesis of Zeolite SSZ-13 using Choline Chloride and Different Crystallization Seeds and its Application in the Thermocatalytic Degradation of Ultra-High Molecular Weight Polyethylene

The synthesis of SSZ-13 was studied by evaluating the influence of two types of crystallization seeds with CHA structure (S1 seeds prepared in fluoride medium and S2 seeds by the conversion of zeolite Y), SiO2/Al2O3 (28, 40, 60 and 100) and OH/SiO2 (0.6 and 0.8) ratios. Choline chloride was used as the structure-directing agent and the crystallizations occurred at 140 ºC from 24 to 96 h. S1 seeds led to the coexistence of zeolites SSZ-13 and P, while S2 seeds promoted in all SiO2/Al2O3 ratios and OH/SiO2 = 0.8, the formation of pure SSZ-13 after 24 h. The SSZ-13 samples are formed by clusters of crystals with cuboid-like morphology and exhibited textural properties typical of CHA framework. SSZ-13 zeolite led to a decrease in the temperature and the activation energy required for the degradation of ultra-high molecular weight polyethylene polymer, demonstrating its efficiency as catalyst in this process.

Thermo-catalytic degradation of PE and UHMWPE over zeolites with different pore systems and textural properties

Abstract The thermo-catalytic degradation of polyethylene (PE) and ultra-high molecular weight polyethylene (UHMWPE) was studied in the presence of zeolites (ZSM-5, ZSM-22, and ferrierite) with different pore systems and textural properties. The zeolites were physically mixed with polymers in the proportion of 30 wt% and submitted to thermogravimetric analysis at heating rates of 5, 10, 20, and 30 °C.min-1. The activation energy of the degradation process was determined using the Flynn-Wall-Ozawa method. The addition of zeolites to polymers has considerably reduced the temperature of degradation. ZSM-22 demonstrated greater efficiency in the degradation of PE because it has a smaller crystallite size, promoting a shorter diffusional path for the polymer fragments coming from the surface. Ferrierite showed a lower energy level in the degradation of UHMWPE, showing the need for synergy between the accessibility of the structure and acidity of the catalyst to promote the cracking of this polymer.

Thermo-catalytic degradation of different consumer plastic wastes by zeolite a catalyst: A kinetic approach

This research work includes the effect of Zeolite-A catalyst on the thermal degradation behavior of six different consumer plastic wastes like high density polyethylene (HDPE), polypropylene (PP), polyethylene terephthalate (PET), polymethylene methacralate (PMMA), polystyrene (PS) and polytetrafluoro ethylene (PTFE) through kinetic approach by using thermogravimetric analysis (TGA) data. Kinetic parameters such as reaction order, activation energy, and Arrhenius constant for the degradation of different waste plastics is determined using model fitting Coats–Redfern method. All the plastics show one-step degradation in the temperature range of 300–600°C. There is a significant decrease in activation energy (Ea) for the thermo-catalytic decomposition of the plastics in presence of Zeolite A catalyst. The extent of catalytic effect is found different for different plastics in the order of HDPE < PP < PS < PET < PMMA < PTFE. The order of the thermal degradation reaction is also found different for different types of plastics. The order of the reaction is altered in case of PET, PS and PTFE in presence of the catalyst but it is unaffected in case of remaining plastics. This treatment would reduce the energy consumption of pyrolysis process and also make the process economical viable.

Kinetic study of thermocatalytic degradation of UHMWPE over microporous and hierarchical ZSM-23 zeolite

The catalytic degradation of ultra high molecular weight polyethylene was studied in the presence of microporous and hierarchical ZSM-23 zeolites by thermogravimetric analysis. The ZSM-23 was synthesized using different structure-directing agents and subsequently subjected to post-synthesis treatment. The materials characterization were carried out by dispersive energy X-ray spectrometry, X-ray diffraction, temperature programmed desorption of ammonia and nitrogen adsorption-desorption measurements. The obtained zeolites were physically mixed with polymer in the proportion of 30 %wt and submitted to thermogravimetric analyses at heating rates of 5, 10, 20 and 30 °C.min−1. The average activation energy for the process was determined from the model-free kinetic proposed by Flynn-Wall-Ozawa. The modified zeolites presented a secondary porosity, which reflected in high values of external surface area and acidity, and demonstrated higher conversion efficiency and lower energy level required in polymer degradation compared to the parent samples.

Pyrolysis of polypropylene over a LZ-Y52 molecular sieve: kinetics and the product distribution

The present work demonstrates the decomposition kinetics of polypropylene in the presence of LZ-Y52 molecular sieve. The pyrolysis was performed at different heating rates in the temperature range 30–600 °C in an inert atmosphere. The kinetics parameters were calculated by applying Ozawa–Flynn–Waal, Tang–Wanjun, and Coats–Redfern (modified) methods. The activation energy (Ea) and frequency factor (A) were found in the range of 52.44–74.50 kJ mol−1 and 1.5 × 10−2 to 9.05 × 108 min−1, respectively. Based on the activation energy data, all three methods agreed well. Moreover, pyrolysis was performed at 350–390 °C in a pyrolysis chamber and the conditions were optimized for maximum oil production. A 10% catalyst amount, at 370 °C, nitrogen flow rate 16 mL/min, and reaction time 60 min were the optimum conditions during experimental work. The products collected were analyzed by gas chromatography/mass spectrometry. In the case of thermal degradation, no oil was obtained; however, thermo-catalytic degradation resulted in more than 40% oil at 370 °C for 1 h. Fuel properties of the oil obtained were determined. These properties were in good agreement with standard values and therefore it has potential applications for replacing fuel oil.