Catalytic pyrolysis is a promising chemical recycling technology to supplement mechanical recycling since plastics can be broken down into monomers or converted to the required fuels and chemicals. In this study, a microwave (MW) -responsive SiC foam@zeoltie core-shell structured catalyst was proposed for the catalytic pyrolysis of polyolefins. Under microwave irradiation, the SiC foam core works as both microwave adsorber and catalyst support, thus concentrating the generated heat energy on the ZSM-5 zeolite shell, where the catalytic reaction takes place. SiC foam with an open cellular structure can also improve the global transport of mass and heat during plastics pyrolysis. In this work, the effects of the SiO₂/Al₂O₃ ratio and alkaline treatment of ZSM-5 zeolite coated SiC foam under MW irradiation on the variations in product distribution from low-density polyethylene (LDPE) pyrolysis were investigated at 450 °C. The results indicated that the appropriate acidity and pore structure were crucial to upgrading gas and liquid products. Particularly, the creation of a mesoporous structure in ZSM-5 zeolite via alkaline treatment could improve the diffusion of large molecules and products, thus significantly increasing the selectivity of high-valued light olefins and aromatics while inhibiting the formation of unwanted alkanes, which are expected in the chemical industry. Concretely, the concentration of olefins in gas increased to 51.0 vol% for ZSM-5(50)-0.25AT, and 65.6 vol% for ZSM-5 (50)-0.50AT, compared with 45.2 vol% for the parent ZSM-5(50). The relative concentration of aromatics in liquid decreased from 96.6% for ZSM-5(50) to 75.9% for ZSM-5(50)-0.25AT, and 71.1% for ZSM-5(50)-0.50AT. Given the respective yield of gas and liquid, the total selectivity of C2–C4 olefins and aromatics for mesoporous ZSM-5 zeolites could reach 58.6–64.9% during LDPE pyrolysis, which were higher than that for the parent ZSM-5 zeolite.

The catalytic hydrogenolysis of a typical model compound of mulching film waste, polyethylene, was investigated as a potential way to improve economic efficiency of mulching film recycling. Nickel-based heterogeneous catalysts are proposed for polyethylene hydrogenolysis to produce liquid hydrocarbons. Among catalysts supported on various carriers, Ni/SiO₂ catalyst shows the highest activity which may due to the interactions between nickel and silica with the formation of nickel phyllosilicate. As high as 81.18% total gasoline and diesel range hydrocarbon was obtained from the polyethylene hydrogenolysis at relatively mild condition of 280 °C, and 3 MPa cold hydrogen pressure. The result is comparable to what have been reported in previous studies using noble metal catalysts. The gasoline and diesel range hydrocarbon are n-alkanes with a distribution at a range of C₄–C₂₂. The gas products are primarily CH₄ along with a small amount of C₂H₆ and C₃H₈. High yield of CH₄ as much as 9.68% was observed for the cleavage of molecule occurs along the alkane chain.

In recent years, biochar has become of considerable interest for environmental applications, it can be used as a catalyst for sulfides reduction of perchloroethylene, but the crucial role of biochar properties played in catalyzing dechlorination remained ambiguous investigation. To pinpoint the critical functional groups, the modified biochars were respectively produced by HNO₃, KOH and H₂O₂ with similar dimensional structures but different functional groups. Combined with the adsorption and catalytic results of different biochars, the acid-modified biochar had the best catalytic performance (99.9% removal) due to the outstanding specific surface area and ample functional groups. According to characterization and DFT results, carboxyl and pyridine nitrogen exhibited a positive correlation with the catalytic rate, indicating that their contribution to catalytic performance. Customizing biochar with specific functional groups removed depth demonstrated that the carboxyl was essential component. Further, alkaline condition was conducive to catalytic reduction, while tetrachloroethylene cannot be reduced under acidic conditions, because HS⁻ and S²⁻ mainly existed in alkaline environment and the sulfur-containing nucleophilic structure formed with biochar was more stable under this condition. Overall, this study opens new perspectives for in situ remediation by biochar in chlorinated olefin polluted anoxic environment and promotes our insight of modifying for biochar catalyst design.

The narrow acid pH range and the nonselectivity of the dominant •OH limit the Fenton systems to remediate the organic wastewater. Inspired by the role of heme in physiological processes, we employed iron porphyrin as a novel homogeneous catalyst to address this issue. Multiple active species are identified during the activation of H₂O₂, including high-valent iron porphyrin ((por)Fe(IV)) species ((por)Fe(IV)–OH, (por)⁺•Fe(IV)=O) and oxygen-centered radicals (•OH, HO₂•/•O₂⁻), as well as atomic hydrogen (*H) and carbon-centered radicals. With the cooperation of these active species, the degradation of pollutants could be resistant to the interference of concomitant ions and proceed over a wide pH range. This cooperative behavior is further verified by intermediates identified from bisphenol A degradation. Specifically, the presence of *H could facilitate the cleavage of the C–C bond and the addition of unsaturated or aromatic molecules. (Por)⁺•Fe(IV)=O could hydroxylate substrates with an oxygen rebound mechanism. Hydrogen atom abstraction of contaminants could be performed by (por)Fe(IV)–OH to form desaturated products by attacking oxygen-centered radicals. The ecotoxicity of bisphenol A could be significantly decreased through degradation. This study would provide a new approach to wastewater treatment and shed light on the interaction between metalloporphyrin and peroxide in an aqueous solution.

Hybrid electric vehicle (HEV) technology is critical to reduce the impact of the internal combustion engines on air pollution and greenhouse gases. HEVs have an advantage in market penetration due to their lower cost and higher driving range compared to battery electric vehicles (BEVs). On the other hand, HEVs use an internal combustion engine and still emit air pollutants. It is hypothesized that HEV performance is impacted by the weather conditions as a result of many factors. It was beyond the scope of this work to systematically evaluate all factors so instead we measured emissions from two vehicles driving city and highway routes in Minneapolis, Minnesota in the winter (−5 °C) and looked for major differences in emissions relative to each vehicle and relative to results that would be obtained from a chassis dynamometer in a controlled laboratory setting at a higher temperature approximately 20 °C). The study then looked to associate differences in emissions with the prevailing conditions to gain new insights. Emissions of interest included the total particle number (TPN), solid particle number (SPN), particulate matter mass (PM), and NOx. One key difference in vehicle engine technology was PFI (port fuel injection) versus GDI (gasoline direct injection). We found the frequency at which the Prius hybrid engine reignited was much higher than the Sonata for city and highway driving, although for both vehicles the catalyst temperature remained high and appeared to be unaffected by the reignitions, despite the cold weather. For most conditions, the Prius emitted more NOₓ but fewer particles than the Sonata. In some cases, NOₓ and particle emissions exceeded the most comparable laboratory-based emissions standards.

Nitrocompounds are the major prime water contaminants. In this investigative study, toxic nitrocompounds (4-nitrophenol, 2,4-dinitrophenol, 2,4,6-trinitrophenol) were removed by using magnetic CuFe₂O₄, CoFe₂O₄, and NiFe₂O₄ material systems. The metal ferrites were synthesized through hydrothermal method and also followed with calcination process. The properties of metal ferrites were confirmed through using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS) and field emission scanning electron microscopy (FE-SEM) studies and results there on were presented. For the first time, the synthesized CuFe₂O₄, CoFe₂O₄, and NiFe₂O₄ material systems were used for the reduction of 4-nitrophenol (NP), 2,4-dinitrophenol (DNP), and 2,4,6-trinitrophenol (TNP) in aqueous medium. The UV–visible spectrometry was employed to monitor the removal of nitro compounds and formation of aminophenol. Among, the three catalysts, the CuFe₂O₄ displayed excellent removal activity for nitrocompounds. The CuFe₂O₄ nanoparticles completely removed the NP, DNP and TNP within 2, 5, 10 min, respectively. The NP reduction reaction follows the pseudo-first-order kinetics. Further, the investigated and proposed CuFe₂O₄, catalyst has given and demonstrated excellent kinetic rate constants 0.990, 0.317, 0.184 min⁻¹ for 4-NP, DNP and TNP respectively, which was very fast kinetic than the already published reports. Also, the aminophenol formation was confirmed for the above mentioned and select nitrocompounds. The obtained results confirm suggest that CuFe₂O₄ nanoparticles based material system could be one of the promising catalysts for nitro compounds removal process.

Recycling of waste glycerol derived from biodiesel production to high value-added chemicals is essential for sustainable development of Bio-Circular-Green Economy. This work studied the conversion of glycerol to 1,3-propanediol over Pt/WOₓ/Al₂O₃ catalysts, pointing out the impacts of catalyst pore sizes and operating conditions for maximizing the yield of 1,3-propanediol. The results suggested that both pore confinement effect and number of available reactive metals as well as operating conditions determined the glycerol conversion and 1,3-propanediol selectivity. The small-pore 5Pt/WOₓ/S–Al₂O₃ catalyst (6.1 nm) gave a higher Pt dispersion (32.0%), a smaller Pt crystallite size (3.5 nm) and a higher number of acidity (0.47 mmol NH₃ g⁻¹) compared to those of the large-pore 5Pt/WOₓ/L-Al₂O₃ catalyst (40.3 nm). However, glycerol conversion and 1,3-propanediol yield over the small-pore 5Pt/WOₓ/S–Al₂O₃ catalyst were significantly lower than those of the large-pore Pt/WOₓ/L-Al₂O₃ catalyst, suggesting that the diffusional restriction within the small-pore catalyst suppressed transportation of molecules to expose catalytic active sites, favoring the excessive hydrogenolysis of 1,3-propanediol, giving rise to undesirable products. The best 1,3-propanediol yield of 32.8% at 78% glycerol conversion were achieved over the 5Pt/WOₓ/L-Al₂O₃ under optimal reaction condition of 220 °C, 6 MPa, 5 h reaction time and amount of catalyst to glycerol ratio of 0.25 g mL⁻¹. However, the 1,3-propanediol yield and glycerol conversion decreased to 19.6% and 51% after the 4th reaction-regeneration which were attributed to the carbonaceous deposition and the agglomeration of Pt particles.

The valorization of municipal solid waste incineration bottom and fly ashes (IBA and IFA) as catalysts for thermochemical plastic treatment was investigated. As-received, calcined, and Ni-loaded ashes prepared via hydrothermal synthesis were used as low-cost waste-derived catalysts for in-line upgrading of volatile products from plastic pyrolysis. It was found that both IBA and air pollution control IFA (APC) promote selective production of BTEX compounds (i.e., benzene, toluene, ethylbenzene, and xylenes) without significantly affecting the formation of other gaseous and liquid species. There was insignificant change in the product distribution when electrostatic precipitator IFA (ESP) was used, probably due to the lack of active catalytic species. Calcined APC (C-APC) demonstrated further improvement in the BTEX yield that suggested the potential to enhance the catalytic properties of ashes through pre-treatment. By comparing with the leaching limit values stated in the European Council Decision, 2003/33/EC for the acceptance of hazardous waste at landfills, all the ashes applied remained in the same category after the calcination and pyrolysis processes, except the leaching of Cl⁻ from the ESP, which was around the borderline. Therefore, the use of ashes in catalytic reforming application do not significantly deteriorate their metal leaching behavior. Considering its superior catalytic activity towards BTEX formation, C-APC was loaded with Ni at 15 and 30 wt%. The Ni-loading favored an increase in overall oil yield, while reducing the gas yield when compared to the benchmark Ni loaded ZSM catalyst. However, Ni addition also caused the formation of more heavier hydrocarbons (C20–C35) that would require post-treatment to recover favorable products like BTEX.

Oxygen vacancy-enriched N/P co-doped cobalt ferrite (NPCFO) was synthesized using ionic liquid as N and P sources, and then the catalytic performance and mechanism of NPCFO upon peroxymonosulfate (PMS) activation for the degradation of organic pollutants were investigated. The as-synthesized NPCFO-700 exhibited excellent catalytic performance in activating PMS, and the degradation rate constant of 4-chlorophenol (4-CP) increased with the increase of OV concentration in NPCFO-x. EPR analysis confirmed the existence of ·OH, SO₄·⁻, and ¹O₂ in the NPCFO-700/PMS system, in which OV could induce the generation of ¹O₂ by PMS adsorption and successive capture, and also served as electronic transfer medium to accelerate the redox cycle of M²⁺/M³⁺ (M denotes Co or Fe) for the generation of radical to synergistically degrade organic pollutants. In addition, the contribution of free radical and nonradical to 4-CP degradation was observed to be strongly dependent on solution pH, and SO₄·⁻ was the major ROS in 4-CP degradation under acid and alkaline condition, while ¹O₂ was involved in the degradation of 4-CP under neutral condition due its selective oxidation capacity, as evidenced by the fact that such organic pollutants with ionization potential (IP) below 9.0 eV were more easily attacked by ¹O₂. The present study provided a novel insight into the development of transition metal-based heterogeneous catalyst containing massive OV for high-efficient PMS activation and degradation of organic pollutants.

To improve catalytic performance and stability of Ag nanoparticles (Ag NPs), a facile ultrasonication-assisted chemical reduction method was developed to fabricate reduced graphene oxide (rGO) aerogels loaded with 1–3 nm Ag NPs under the normal temperature and pressure. The ultrasonication facilitated the dispersion of Ag(I) in the form of silver ammonia and anchored onto GO nanosheets. Ag(I) and GO were simultaneously reduced to Ag(0) immobilizing onto 3D rGO hydrogels within the heterogeneous liquid phase, and ultimately formed 3D rGO-Ag NPs aerogels. The 3D rGO-Ag NPs aerogels displayed superb catalytic performance for the reduction of nitrobenzene (NB), 1,3-dinitrobenzene (DNB) and 4-nitrophenol (NP) into aniline, 1,3-diaminobenzene and 4-aminophenol, respectively. The individual reduction rate Kobs for NB, DNB and NP were 0.168 h−1, 0.109 h−1 and 0.092 h−1, which were much higher than those of other Ag NPs-based materials. Moreover, the immobilization of 1–3 nm Ag NPs in 3D rGO-Ag NPs was stable during the whole reduction reaction without aggregation and leaching. The high stability of Ag NPs in 3D rGO-Ag NPs and superb performance on catalytic reduction of nitroaromatic compounds (NACs) could be concluded into ultrasonication influence in the preparation procedure and synergistic effect of Ag NPs and 3D rGO in the catalytic reduction process. The simple ultrasonication-assisted chemical reduction approach provided a scaled-up application prospect in catalytic reduction of NACs by metal nanoparticle catalysts.