Industrial & Engineering Chemistry Research最新文献

Thermoplastic polypropylene (PP) insulated cables, an alternative to cross-linked polyethylene, offer superior insulation, high operating temperature, recyclability, cost-effectiveness, and a limitless cable length. However, challenges such as brittleness at low temperatures and limited flexibility at room temperature impede the application of PP in the field of cable insulation. To address these issues, in-reactor alloy technology seems to be a promising strategy, creating a multiphase system with intrinsic elastomer dispersion in a homopolypropylene matrix. Most of the research on PP-based multiphase systems focuses on enhancing mechanical properties by controlling microscopic structures. A comprehensive understanding of structural evolution during processing and its correlation with the electrical performance of PP thermoplastic insulation materials remains in its infancy. In this study, PP in-reactor alloys with intrinsic elastomers were utilized as model polymeric materials. A novel technology of “melting extrusion–hot stretching–thermal annealing” was employed to manipulate the elastomer phase morphology and crystalline structure. Severe interfacial mismatch during hot stretching initially compromised the mechanical and electrical properties. After thermal annealing, the mechanical and electrical properties were recovered, arising from the reduced rubber deformation and increased crystalline reorganization. The work presented here is expected to help our understanding of the dependence of electrical and mechanical properties on the microstructure of PP in-reactor alloys, providing a valuable reference for the structural design of cable insulation.

The venting operation is a primary measure to mitigate overpressure in CO₂ transport pipelines. It involves intense oscillations and the threat of low temperatures arising from the throttling effect. Multistage throttling structures have been proven to effectively enhance the stability of the system, and the objective of this study is to explore the impact of multistage throttling structures on the pressure and temperature within the throttling structure using a one-dimensional model. The results indicate that by appropriately setting the numbering of valves, valve openings, and diameter of throttling pipes, multistage throttling can effectively elevate the temperature of the throttling structure. However, it is noteworthy that achieving the avoidance of low-temperature phenomena comes at the expense of reducing the pressure drop rate within the main pipeline. Therefore, the practical application should consider a balanced approach to both the low temperature in the throttling structure and the overpressure in the main pipeline.

Hydrogen is widely produced by a steam methane reforming (SMR) process, but CO₂ that is produced as a byproduct needs to be captured. For this purpose, amine absorption, one of the main carbon capture and utilization (CCU) techniques, is commonly integrated with the SMR process. A drawback of the amine absorption process is that captured CO₂ is recovered in the gas phase and must be liquefied or solidified to be suitable for transportation and storage. Traditionally, the liquefaction of CO₂ is achieved by a series of compression-cooling and expansions (e.g., the Linde–Hampson process), which is a costly and energy-intensive process. This study proposes using liquefied natural gas (LNG) not only as the source for hydrogen production and heat supply for the SMR reaction, but also to provide the necessary thermal energy requirement for the liquefaction of CO₂ using plate-fin heat exchangers. Aspen HYSYS is used to simulate a 300 Nm³/h scale SMR process, the amine absorber, and CO₂ Liquefaction processes. Energy, exergy, and cost efficiencies for a conventional Linde–Hampson process and two novel setups utilizing LNG cold energy are studied and compared. In summary, our results show the significant advantages of the proposed nonrecycling process over the conventional Linde–Hampson system. Specifically, it offers up to a 39.38% enhancement in overall exergy efficiency, achieves a net rational exergy efficiency as high as 95.72%, and reduces total capital costs by 30.83%.

A thorough cost analysis based on the conceptual process design of a two-step CO₂-to-methanol synthesis route is performed, comprising CO₂ hydrogenation in an electrified reverse water–gas shift (RWGS) reactor, followed by a conventional methanol synthesis reactor. In the former step, both thermal and nonthermal plasma reactors are considered, i.e., direct current (DC) arc and microwave (MW) plasma, respectively, and benchmarked against the conventional thermo-catalytic counterpart. It is found that employment of any type of plasma promotes higher CO₂ conversions in the RWGS step than the conventional thermo-catalytic reactors (82–90 vs 61%), thereby higher single-pass methanol yields (24–27 vs 17%). This comes at the expense of higher electricity demand, which minorly affects the process economics since green H₂ utilized in RWGS and methanol synthesis is the cost driver. The economic analysis shows that the current green H₂ prices (2022 scenario) render the two-step CO₂-to-methanol process economically unviable, regardless of the reactor technology used, attaining approximately a 4-fold higher levelized cost of methanol (LCOM), 1875–1900 €·ton^–1, compared to the state-of-the-art route, i.e., syngas production through steam methane reforming (SMR) and coal gasification, followed by WGS and methanol synthesis reactors. However, the two-step CO₂-to-methanol route could be viable for a long term (2050 scenario), driven by lower costs of electricity (10 €·MW h^–1) and green H₂ (1.0 €·kg^–1) along with the avoided emission credits. This originates from the lower greenhouse gas (GHG) emissions that the two-step CO₂-to-methanol route attains compared with the state-of-the-art. In the 2050 frame, plasma technologies are anticipated to be at least 45% more profitable than thermo-catalytic reactors, while the profitability of nonthermal plasmas will significantly improve if vacuum operation is avoided, mitigating the excessive compression energy demand and subsequently decreasing the operating cost.

This article presents the theory of dual-mode gradient elution chromatography considering simultaneous spatial and temporal changes in the column temperature and mobile phase composition. In this technique, both solvent and temperature gradients propagate independently along the axial coordinate of the chromatographic column. The mathematical model of the underlying process contains nonlinear convection-dominated partial differential equations for mass, volume fraction of the solvent, and energy, coupled with algebraic or differential equations. The linear solvent strength retention model and the modified van’t Hoff retention behavior are utilized for expressing coefficients of Henry’s, nonlinearity, axial dispersion, and heat conductivity as functions of temperature and solvent composition. An extended high-resolution semidiscrete finite volume method is utilized for the numerical approximation of model equations. Numerous case studies have been conducted to assess the column performance for a variety of operating conditions. The benefits of dual-mode gradient elution, influencing the propagation speeds of concentration profiles, are thoroughly explored compared to that of isocratic operation. The results show a significant reduction in the retention time and a better performance of the column. Outcomes of this study will be useful for optimizing the model parameters and for further improving the process performance.

In the iron and steel-making process, direct reduced iron (DRI) is the very first step that uses CO and H₂ to reduce iron ore and therefore contributes to fewer CO₂ emissions than the conventional blast furnace process. The CO and H₂ required for the DRI process are generated from bottom-fired reformers with reformer tubes filled with catalyst particles and transported to the shaft furnace for iron-ore reduction. Therefore, the DRI reforming process plays an essential role in DRI production by supplying reducing gases of the desired composition, flow rate, and temperature. In the present work, a 3D computational fluid dynamics model is developed to simulate the industrial-scale DRI reforming process that includes the multicomponent gas mixture flow in reactor tubes and burners, heat transfer from burner to tubes due to combustion on the burner side, and reforming reactions in catalyst-filled tubes. The pressure drop on the tube side due to the presence of the catalyst is calculated through a porous media approach. Results show the formation of a long and narrow flame on the burner side due to combustion, which led to an increase in the temperature of the tube wall and at the tube center. This enabled endothermic reforming reactions on the tube side and resulted in the consumption of CH₄ and H₂O and the formation of CO and H₂. The model predictions of tube outlet reformed gas temperature and composition and the temperature at different axial locations at the tube wall and center are in satisfactory agreement with ArcelorMittal’s plant data.

Catalysts for the hydrogenation of adiponitrile (ADN) have been extensively studied, but achieving high selectivity of hexamethylenediamine (HMDA) in the absence of additional alkali inhibitors still poses many challenges. Herein, we fabricated nickel-based catalysts modified with Na additives for the liquid-phase hydrogenation of ADN in a fixed-bed reactor. The results showed that suitable weak acid sites are more conducive to enhancing the selectivity for HMDA, while stronger acid sites tend to promote the formation of higher amines. Moreover, the introduction of an appropriate amount of Na additive facilitates the dispersion of nickel, increasing the content of Ni⁰ species. Its electron-donating capacity to nickel aids in hydrogen adsorption and dissociation, thereby enhancing hydrogenation activity and favoring the selectivity for HMDA. Under optimal conditions of 120 °C and 4 MPa, improved catalytic performance with 100% ADN conversion and 82.07% HMDA selectivity were achieved over the Ni-0.15Na/Al₂O₃ catalyst.

The purpose of carbon capture and sequestration (CCS) is to reduce CO₂ emissions from the use of fossil fuel. In this article, the effect of seeding on the Dead Sea water (DSW) CO₂ storage capacity was investigated. Three types of seed particles were used: rocks from the bottom of the DS, amorphous silica, and quartz sand; the influence of each type on the storage capacity of DSW toward CO₂ was studied. When seeds were added to DSW during or after CO₂ injection, different solid precipitates were formed depending on the seed type; with rock seeds collected from the DS basin, calcite and dolomite precipitates were formed, while aragonite, magnesite, and monohydrocalcite were precipitated when amorphous silica was used as seed. Quartz sand was used as received and also after acid washing; aragonite, magnesite, and monohydrocalcite were precipitated on the as-received sand, while no precipitate was observed on the acid-washed quartz sand. It was concluded that carbonate precipitation followed the crystal structure of the seed; the main condition for the overgrowth of one crystalline phase over another was crystal lattice compatibility. The crystal structure of the purified quartz was not found to be a good seed to the overgrowth of calcium or magnesium carbonate.

Fiber-reinforced rubber materials find extensive applications in tire manufacturing, hoses, conveyor belts, and various industrial sectors. Polyimide (PI) fibers offer superior fatigue resistance, tensile strength, modulus, and high-temperature durability compared to aramid fibers, positioning them as ideal substitutes in the belt layers of aircraft tire. To enhance the interfacial adhesion between polyimide fibers and rubber while minimizing the use of toxic and environmentally harmful materials, a novel eco-friendly carbon-reducing dipping system was devised. This system employs blocked diisocyanate and epoxy resin to activate PI fibers, and then uses a dipping solution, primarily composed of a blend of styrene–butadiene–vinylpyridine (VP) latex, lignin, tannic acid (TA), and glyoxal, to dip the fibers. This approach connects PI fibers and the rubber matrix through chemical bonds, thereby effectively enhancing the interfacial adhesion between the fibers and the rubber. The H pull-out force of the PI fiber cords treated by this system reached 179.6 N, with an average 180° peeling force of 14.7 N, and dynamic fatigue resistance exceeding 67,000 cycles, comparable to those achieved with the resorcinol-formaldehyde-latex (RFL) dipping system. These results indicate the efficacy of the developed system as a potential replacement for the RFL system. This research presents a sustainable and environmentally friendly approach to enhancing the interfacial adhesion of fiber-reinforced rubber composites, thereby contributing to the advancement of innovative high-performance fibers and biobased dipping system.

A kinetic model of the curing of methyl methacrylate adhesive (including nanocomposite methyl methacrylate adhesive) in the presence of the initiating systems “aryl peroxide + zirconocene dichloride” and “aryl hydroperoxide + zirconocene dichloride” is made. Computational experiments have been carried out which demonstrate the relationship of the curing rate with the curing temperature in the range of 323–343 K and with the ratio of the initial concentration of zirconocene dichloride to the initial concentration of the initiator [Mc]₀/[I]₀ for the following initiators: benzoyl peroxide (PB), ethylbenzene hydroperoxide (HPEB), and ethylbenzene hydroperoxide adduct with cadmium 2-ethyl hexanoate [HPEB·Cd(EH)₂]. It is shown that in order to increase the curing rate of the adhesive, curing should be carried out at a higher temperature (343 K) and at a higher value of the ratio [Mc]₀/[I]₀ = 10 in the presence of the most rapidly decomposing initiator HPEB·Cd(EH)₂. To increase the weight-average molecular weight of poly(methyl methacrylate), the proportion of syndiotactic triads in its composition, and consequently, to improve the adhesion strength and heat resistance of the adhesive joint, the curing of the adhesive must be carried out at the reduced temperature (323 K) and the reduced ratio of the [Mc]₀/[I]₀ = 0.1 in the presence of the least rapidly decomposing initiator HPEB.