Fuel Processing Technology最新文献

Steam reforming of biomass-derived pyrolysis liquids (bio-oil) to produce hydrogen with carbon-based Ni catalysts is gaining attention due to their advantages in terms of cost, sustainability and activity. However, the catalytic activity at long times on stream is compromised by either coke deposition or gasification of the support. To face these drawbacks, two activated carbons have been studied as Ni catalyst support: a microporous carbon of high purity and a mesoporous carbon with phosphorus surface groups. The activity and long-term stability of these catalysts have been studied for the steam reforming of model compounds of bio-oil. The microporous support provided a slightly higher H₂ production and lower contribution of methanation reaction. However, gasification of this support after 20 h led to a decline in the activity, and massive formation of carbon nanotubes and coke. Nevertheless, the resulting material maintained an outstanding stability with high and stable H₂/CO ratio for 50 h. The P-containing catalyst showed a remarkable long-term stability, but lower H₂/CO ratio. Carbon gasification was less significant in this catalyst due to the presence of surface phosphorus groups, and the generation of nickel phosphides, which hampers the growth of pyrolytic carbon and carbon nanotubes, leading to a superior stability.

The microwave pyrolysis (MWP) of sewage sludge (SS) was conducted to investigate the impact of the organic composition of SS on the yield and composition of the derived bio-oil. The experiments were conducted in a microwave oven at 900 °C with a heating rate of 50 °C/min and achieved the product yield of 43.10 ± 2.23% bio-oil, 48.07 ± 1.26% bio-char, 8.83 ± 1.65% bio-gas. The chemical composition of bio-oil was investigated using gas chromatography–mass spectrometry and 145 species were identified. Protein and lipid contents in SS are the primary source of bio-oil yield, while bio-gas are predominantly derived from lignocellulosic materials. The unique non-thermal effects of microwaves can facilitate the ring-opening of small cycloalkanes to form straight olefins through hydrogen transfer reactions. Additionally, they can promote aldol condensation reactions, Pinacol rearrangements, and methoxy cleavage to form phenolic and aromatic structures with methyl groups. Furthermore, microwaves can aid in the dehydration, condensation, and cyclization reactions of amino acids to produce N-heterocycles while also facilitating lipid depolymerization into fragments for Diels–Alder cyclization. The results of this study will be beneficial for deeply understanding reactant characteristics and the reaction process during the MWP of SS.

This paper assesses the potential of plastics valorization by pyrolysis and in line catalytic dry reforming for syngas production. Previous studies showed the suitability of a continuous process made up of a conical spouted bed reactor for fast pyrolysis and a fluidized bed reactor for catalytic steam reforming. In order to step further in the application of this technology under dry reforming conditions, equilibrium simulation was approached to analyze process performance, as the development and optimization of this technology for the production of high-quality syngas requires understanding in detail the complex influence of process parameters. Thus, this study deals with the influence of main process parameters, namely, temperature, CO₂/C ratio and the type of plastic, on the process performance. Furthermore, the role played by steam co-feeding in the dry reforming in order to adjust syngas H₂/CO ratio was evaluated by varying the steam/carbon ratio. The obtained results clearly show that a strict control of process conditions is required to ensure high conversion to syngas and avoid undesired reactions, such as reverse WGS. Among the plastics studied, polyolefins are those of highest potential for syngas production, but polystyrene allows producing a high quality syngas through a combined reforming strategy.

Steam cracking in fluidized beds offers an alternative to conventional steam cracking for sustainable hydrocarbon production. This approach has gained interest, particularly in the context of recycling plastics to generate valuable hydrocarbons. Integrating this process into existing petrochemical clusters necessitates a thorough characterization of the products derived from this new feedstock. This work focuses on addressing the challenges associated with species quantification and characterization time for assessing the product mixture resulting from a steam cracking process. The experiments were conducted in a semi-industrial scale dual fluidized bed steam cracker, utilizing polyethylene as the feedstock. To sample species spanning from C1 to C18, cooling, scrubbing, and adsorption were introduced. These steps were integrated with GC-VUV (Gas Chromatography with Vacuum Ultraviolet Spectroscopy) and other widely recognized analytical methods to quantify the sampled species. The primary focus was on GC-VUV analysis as a suitable characterization method for identifying and quantifying C4 to C18 species, which can constitute up to 35% of the product mixture obtained from polyethylene steam cracking (750 °C to 850 °C). Quantifying C6 to C18 hydrocarbons becomes the time-critical step, with GC-VUV potentially achieving this in 1/6th of the analysis time and with relatively optimal quantification compared to the traditional characterization methods.

The electric-field assisted deposition is successfully proposed as a method for the manufacturing of carbon nanostructured films with tunable properties, benefiting from the superimposition of electric fields on the thermophoretic deposition. Morphology, optical, and thermo-resistive properties of the carbon nanoparticle (CNP) films have been studied by UV–vis Absorption Spectroscopy, Scanning Electron Microscopy, Atomic Force Microscopy, and Current-Voltage analysis. In comparison to thermophoresis alone, the introduction of an electric field results in a six-fold increase in the deposition rate characterized by a non-linear film growth influenced by a three-fold augmentation in surface roughness and polarization effects. Notably, the surface morphology of the CNP films undergoes modification, exhibiting larger grains and a reduced optical band gap energy. Moreover, while maintaining a non-ohmic behaviour, the electric field plays a crucial role in increasing by about two orders of magnitude the electrical conductance of CNP films at ambient temperature. This effect is accompanied by a decrease in temperature sensitivity, attributed to the low and nearly temperature-independent activation energy for the tunneling of electrons in the percolative network. In summary, electric-field assisted deposition is a promising approach to tailor the thermal response of CNP films, which could be beneficial for the development of next-generation sensors.

Catalytic combustion of volatile organic compounds from industrial flue gases at low temperatures remains a challenge. Herein, we developed a mesoporous Mn-Co-Ti catalyst for o-xylene degradation by a solvothermal strategy. The optimized Mn_0.1Co-TiO₂ catalyst possessed a nanoflower structures with a surface area of 83.1 m²/g and mesoporous volume of 0.1191 cm³/g. Mn-doping modulated the electronic interactions between Mn and Co, which promoted the formation of MnCo₂O_4.5 phase and increased Co³⁺ and Mn⁴⁺ content of the catalyst. The Mn_0.1Co-TiO₂ catalyst had an improved reduction capacity from 170 to 644 °C, with a maximum H₂ consumption of 4.56 mmol/g. The Mn_0.1Co-TiO₂ catalyst achieved 50% o-xylene conversion at 193 °C at a GHSV of 60,000 h⁻¹, whereas the equivalent catalyst prepared by impregnation required 315 °C for 50% o-xylene conversion. In the presence of NO, the generated NO₂ accelerated o-xylene conversion because it promoted the generation of more Mn⁴⁺-O-Co³⁺ active sites and accumulation of intermediates such as maleate and acetate species. NH₃ and H₂O had slight inhibitory effects on o-xylene conversion, which were attenuated by abundant mesopores and redox ability of catalyst. SO₂ gas caused inactive sulfates and chemical deactivation on catalyst surface, thus leading to excessive formation of benzoquinone products.

In this study, hydrothermal conversion of passion fruit husk powder (PFHP) into levulinic acid (LA) was achieved using SO₃H-functionalized ionic liquids (ILs) as catalyst. The investigation focused on the impact of IL types and reaction conditions (temperature, time, water quantity and catalyst loading) on LA yield. Among the selected ILs, [C₄SO₃Hmim][HSO₄] exhibited the highest LA yield at 66.6%, achieved under specific conditions: 4 h of reaction time, 180 °C temperature, 0.2 g of PFHP, 1.5 g of IL, and 6.0 g of deionized water. Remarkably, [C₄SO₃Hmim][HSO₄] displayed consistent stability and catalytic efficiency throughout four recycling cycles. Comprehensive analyses, including scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and X-ray diffraction (XRD), were conducted on the solid residues of passion fruit husk obtained at different reaction times. These analyses revealed significant alterations in surface morphology, functional groups, and crystallinity index of the solid residues with prolonged reaction times. Notably, hemicellulose and lignin removal occurred within the first 0.5–1 h of the reaction, leading to the formation of by-products after 3 h. This one-pot process for LA production from agricultural waste showcases a promising avenue for converting sustainable biomass resources into valuable chemicals, emphasizing the potential for future biomass utilization.

The boom of the biodiesel industry has led to an oversupply of by-product glycerol as a direct consequence, which has been detrimental to its market value. The chemical reactivity that this compound possesses makes it an exceptional building block from which many synthetic routes can originate. In the past two decades, as a way to upgrade glycerol, there have been great developments in experimental approaches to obtain different products with applications as fuel additives, green solvents or precursors to other materials. These works have focused mainly on the development of catalytic and biotechnological processes and optimization of operation conditions to obtain chemicals like glycerol carbonate, acetals, esters, ethers, 1,2- and 1,3-propanediol, acrolein, halogenated products and different organic acids. Throughout these years an increasing amount of articles have reported thermodynamic information and kinetic models for different reactions using glycerol of substrate, whose knowledge is essential for subsequent reactor and process design. For the first time, these aspects for transformation reactions from glycerol are compiled and presented in a systematic way in this comprehensive review that also touches on process intensification strategies to enhance glycerol conversion.

The effects of ammonia and hydrogen addition on soot formation characteristics in n-decane laminar diffusion flames were studied. The addition of argon was specifically considered to identify the chemical effect of ammonia. The flame temperature, particle morphology, and oxidation characteristics were analyzed. Results showed that both ammonia and hydrogen addition increase the flame height and suppress soot formation, while the suppression effect of ammonia is more pronounced. The addition of argon or ammonia reduces the temperature of flame upstream and yields the similar flame temperature, while hydrogen addition increases the flame temperature. Compared to the flame with argon, the addition of ammonia delays particle nucleation, indicating that the soot nucleation and growth process are chemically inhibited. In contrast, doping hydrogen leads to an earlier nucleation process and aggregation phenomenon. Further analysis on particle nanostructure indicated that the addition of ammonia yields shorter lattice fringes, larger interlayer spacings and amorphous carbon contents, demonstrating a looser and higher disorder internal structure. The addition of hydrogen yields longer fringes and smaller interlayer spacings, showing the particles have a more compact internal structure and higher degree of graphitization. This indicates hydrogen addition reduces the oxidation activity of the particles, which is confirmed by thermogravimetric analysis.

Pyrolysis is a promising way to treat the waste tires for high value carbon black production. However, the carbon black formation mechanism is still unclear due to the complex decomposition and polymerization reactions during the pyrolysis of tire components. In this study, the production behavior, characters, and mechanism of carbon black from pyrolysis of natural rubber (NR), butadiene rubber (BR), and styrene-butadiene rubber (SBR) were investigated. The yield of carbon black was increased from 20.8%–24.4% to 47.9%–56.7% with the increase of pyrolysis temperature from 1100 to 1300°C. Although the carbon black production yield from NR was lower than that of BR and SBR at 1300°C, the graphitization degree (I_D/I_G = 2.22), microcrystal length (3.17 nm) and mean particle diameter (90.3 nm) of the carbon black derived from NR were the highest. The volatile evolution, carbon black nucleation mechanisms were revealed by reactive force-field molecular dynamics simulations. The pyrolysis of BR and SBR generated more C₂H₂, C₂H₃⋅, long carbon-chains and cyclic molecules than NR, which probably resulted in a higher carbon black yield than NR. With few defect borders, regular stacking and wrapping of the aromatic layers, the carbon black from NR exhibited more ordered nucleation and high graphitization degree.