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Raman spectroscopy is a promising method for the analysis of natural gas. It is necessary to account for the broadening effects on spectral lines to improve measurement accuracy. In this study, the broadening coefficients for methane lines in the region of the ν2 band perturbed by propane, n-butane, and isobutane at room temperature were measured. We estimated the measurement errors of the concentration of oxygen and carbon dioxide in the case of neglecting the broadening effects on the methane spectrum by the pressure of C2–C6 alkanes. The obtained data are suited for the correct simulation of the methane spectrum in the hydrocarbon-bearing gases and can be used to improve the accuracy of the analysis of natural gas by Raman spectroscopy.

The propagation speeds of premixed n-butane–air mixtures (2.0–5.7 vol%) were investigated under various initial conditions (pressures of 0.4–1.2 bar; temperatures of 289–500 K). The study consists of both, experimental measurements using two different enclosures (a sphere and a cylinder) and kinetic modeling via a dedicated computing program. The propagation speeds of premixed n-butane–air mixtures were obtained via the adiabatic model of flame propagation, which allows us to obtain these important parameters using the normal burning velocities and expansion coefficients. The expansion coefficients were calculated using thermodynamic data as the ratio of burnt to unburnt gas densities, assuming that an equilibrium was established in the flame front. The propagation speeds obtained based on the experimental burning velocities were analyzed for comparison with the computed velocities. Finally, the dependence of the propagation speed on the initial pressure and temperature was discussed.

Vanadium phosphorus oxide (VPO) catalysts promoted by phosphorus-based ionic liquids (ILs) as structure directing agent and promoters have been innovatively synthesized and investigated for selective oxidation of n-butane to maleic anhydride (MA). The catalytic performances showed that the IL addition notably improved the n-butane conversion and MA selectivity, during which the optimized 3%IL-VPO catalyst exhibited the maximum MA yield of 59.2% that is much better than that of blank VPO with 49.4% MA yield under the same reaction conditions. XRD, FI-IR, Raman, SEM, TG, BET, XPS and H 2 -TPR techniques were utilized combinatorically to elaborate the synergistic effect of cations and anions of ILs. Results demonstrated that IL-cations oriented synthesis of VPO precursor showing a vertically intercrossed slice structure morphology having smaller lamellar thickness. Correspondingly, it notably enhanced the specific surface area of the VPO catalysts and exposed the more active surface of (VO) 2 P 2 O 7 after activation. Meanwhile, IL-anions as promoters largely modulated the P/V ratio, valence state of V and oxygen species amounts on the surface of VPO catalyst, etc. All of these influence factors were subsequently discussed in detail and correlated to the catalytic performance of VPO catalysts. Graphic Abstract

The rational design of supported Lewis acid catalysts is frequently impeded by an incomplete understanding of how the support’s synthetic history governs its intrinsic acidity and catalytic efficacy. Herein, we elucidate the structure–property–performance relationship linking the aging dynamics of a boehmite precursor to the activity of the resultant chlorinated alumina (Al2O3–Cl) catalyst in n-butane isomerization. Using n-butane as the probe feedstock, we investigated how alumina supports with distinct physicochemical properties regulate the performance of Al2O3–Cl catalysts for n-butane isomerization. By systematically adjusting the aging parameters (stirring rate, temperature, and time), we reveal that the structural evolution of the alumina support transitions from initial particle aggregation to Ostwald ripening and surface reconstruction. A decisive structure–performance correlation is identified: precursor synthesis conditions govern both the population and accessibility of specific surface hydroxyls (notably Type II terminal OH groups), which act as anchoring sites for the generation of active Lewis acid centers upon chlorination. Optimal aging parameters (300 rpm, 90 °C, 6 h) promote the formation of a hierarchical pore architecture with a maximized density of accessible hydroxyls, thereby affording enhanced Lewis acidity and superior isomerization activity. This work provides a fundamental framework for tailoring solid acid catalysts by precisely engineering the precursor architecture.

Vanadium phosphorous oxide (VPO) catalysts have been recognized as heterogeneous catalyst for selective oxidation of low-carbon alkanes i.e., n-butane toward maleic anhydride. This process has widely gained attention globally due to its highly selective and cost-effective process. Herein, we employed Cd0.2Zn0.8S as a support for the VPO catalyst and evaluated its n-butane catalytic performance. Compared to the unpromoted catalyst (Blank-VPO), a higher n-butane conversion and MA yield were successfully obtained from the promoted catalyst (Cd0.2Zn0.8S@VPO). Interestingly, it reduces the byproducts, i.e., CO2 and CO emission. Characterization methods such as TGA, XRD, EDS, SEM, FTIR, NH3-TPD, XPS, TEM, and Raman spectroscopy were used to characterize the Cd0.2Zn0.8S, VPO precursor and catalyst.

The influences of acidic properties and pore structures of H-Beta and H-ZSM-5 zeolites on the reaction properties of n -butane isomerization at low temperatures were investigated. The results showed that bimolecular pathway of n -butane conversion predominates over H-ZSM-5 zeolites, while the monomolecular and bimolecular pathways occur simultaneously over H-Beta zeolites. The conversion rate of n -butane strongly relies on the amount of strong Brønsted acid sites regardless of zeolite topology. However, the topology of zeolites crucially determines the products distribution, and the density of strong Brønsted acid sites plays a secondary role. The cavities of zeolites, formed in the intersections of channels, provide the places for the bimolecular reaction. The formation of trimethyl C 8 intermediates is spatially restricted in the narrow channel intersections of H-ZSM-5 zeolites, resulting in higher contribution of n -butane disproportionation reaction. In addition, the narrow pore channels of H-ZSM-5 zeolite limit the monomolecular isomerization of n -butane molecules and affect the diffusion of heavier products (pentane) produced from bimolecular reaction, leading to the severe secondary reaction and high selectivity to propane. In contrast, the pore channels of H-Beta zeolite allow the monomolecular isomerization of n -butane and the deposition of coke. Graphical Abstract The topology of zeolites crucially determines the products distribution.

Recently, global warming is proving to be an increasing challenge for the sustainable human survival on planet earth. Worldwide, researchers are putting their efforts into controlling carbon emissions and have set the aim to achieve levels of overall carbon neutrality. Different industrial processes, especially oil refinery processes, release large amounts of low-carbon alkanes as gaseous byproducts directly into the air and pollute clean environments, which is one of the major reasons for sudden climate changes, ocean acidification, loss of biodiversity, and rising sea levels. The conversion of lighter alkanes, especially n-butane, into value-added chemicals can be beneficial for green economies and green environments. Presently, heterogeneous vanadium phosphorus oxide catalysts (VPOs) are considered potential candidates for n-butane selective oxidation toward maleic anhydride (MA). In this research, we developed a VPO catalyst with the assistance of copper-based ionic liquids (Cu-ILs), including [Bmim][OAc]–[Cu(OAc)2], [Bmim][Cl]–[CuCl], and [Bmim][Cl]–[CuCl2]. We observed significant improvement in the MA selectivity; meanwhile, the COx (CO and CO2) selectivity was decreased. Compared to the unpromoted catalyst (Blank-VPO), the Cu-IL-promoted catalyst, i.e., [Bmim][Cl]–[CuCl2]-VPO remarkably increased the MA selectivity (11%) and n-butane conversion (9.2%) and minimized the COx selectivity (11%). In addition to this the ratio of CO/CO2 has been reduced from 2.01 to 1.32. Therefore, this can be a helpful process for achieving carbon neutrality goals.

Currently, hydrogen-enriched n-butane blends present a real interest due to their potential to reduce emissions and increase the efficiency of combustion processes, as an alternative fuel for internal combustion engines. This paper summarises the recent research on laminar burning velocities of hydrogen-enriched n-C4H10–air mixtures. The laminar burning velocity is a significative parameter that characterises the combustion process of any fuel–air mixture. Accurately measured or computed laminar burning velocities have an important role in the design, testing, and performance of n-C4H10–H2 fuelled devices. With this perspective, a brief review on the influence of hydrogen amount, initial pressure and temperature, and equivalence ratio on the laminar burning velocity of hydrogen-enriched n-C4H10–air mixtures is presented. Hydrogen has a strong influence on the combustion of butane–air mixtures. It was observed that a parabola with a maximum at a value slightly higher than the stoichiometric ratio describes the variation in the laminar burning velocity of hydrogen-enriched n-butane–air mixtures with the equivalence ratio. An increase in initial pressure or hydrogen amount led to an increase in this important combustion parameter, while an increase in initial pressure led to a decrease in laminar burning velocity. Overall, these studies demonstrate that hydrogen addition to n-C4H10–air mixtures can increase the laminar burning velocity and flame temperature and improve flame stability. These findings could be useful for the optimisation of combustion processes, particularly in internal combustion engines and gas turbines. However, the literature shows a paucity of investigations on the laminar burning velocities of hydrogen-enriched n-C4H10–air mixtures at initial temperatures and pressures differing from those in ambient conditions. This suggests that experimental and theoretical investigations of these flames at sub-atmospheric and elevated pressures and temperatures are necessary.

A novel continuous subcritical n -butane extraction technique for Camellia seed oil was explored. The fatty acid composition, physicochemical properties, and benzo[a]pyrene content of Camellia seed oil extracted using this subcritical technique were analyzed. Orthogonal experiment design (L 9 (3 4 )) was adopted to optimize extraction conditions. At a temperature of 45 °C, a pressure of 0.5 MPa, a time of 50 min and a bulk density of 0.7 kg/L, an extraction yield of 99.12 ± 0.20 % was obtained. The major components of Camellia seed oil are oleic acid (73.12 ± 0.40 %), palmitic acid (10.38 ± 0.05 %), and linoleic acid (9.15 ± 0.03 %). Unsaturated fatty acids represent 83.78 ± 0.03 % of the total fatty acids present. Eight physicochemical indexes were assayed, namely, iodine value (83.00 ± 0.21 g I/100 g), saponification value (154.81 ± 2.00 mg KOH/g), freezing-point (−8.00 ± 0.10 °C), unsaponifiable matter (5.00 ± 0.40 g/kg), smoke point (215.00 ± 1.00 °C), acid value (1.24 ± 0.03 mg KOH/g), refrigeration test (transparent, at 0 °C for 5.5 h), and refractive index (1.46 ± 0.06, at 25 °C). Benzo[a]pyrene was not detected in Camellia seed oil extracted by continuous subcritical n -butane extraction. In comparison, the benzo[a]pyrene levels of crude Camellia seed oil extracted by hot press extraction and refined Camellia seed oil were measured at 26.55 ± 0.70 and 5.69 ± 0.04 μg/kg respectively.

In this study, the surface of NiCoCrAlHf alloy was preoxidized with a high-temperature flame to improve its high-temperature oxidation resistance. A dense Al 2 O 3 oxide scale was formed on the surface of NiCoCrAlHf after flame pre-oxidation, which has an important influence on the consumption of Al in the β-phase and the surface morphology after the oxidation experiment. The results show that the oxide-layer area of the original sample was 1.81-fold larger than that produced after the 48- and 300-h oxidation cycles, while the oxide-layer area of the flame-preoxidized sample was only 1.16-fold larger. In addition, the γ'-phase area of the original sample was 1.31-fold larger, while that of the flame-preoxidized sample was only 1.28-fold larger. The area changes of the oxide layer and the γ'-phase indicate that the high-temperature oxidation resistance of the NiCoCrAlHf alloy was further improved by Hf-doping modification. Graphical abstract