Asia-Pacific Journal of Chemical Engineering最新文献

The attrition behavior of HZSM-5 zeolite catalyst particles at room temperature was investigated in a laboratory-scale fluidized bed. The effects of three fluidization conditions on particle attrition were investigated, and a new attrition model was proposed. The results demonstrate that the attrition rate is inversely proportional to the initial particle size and proportional to the apparent gas velocity. After increasing to 80 μm and .3 m/s respectively, they are no longer the main factor affecting attrition. The effect of bed pressure on attrition rate is nonlinear, and the lowest attrition rate is obtained when the diameter-height ratio is 1:1. Unsteady attrition stage can be divided into initial stage and deceleration stage. Surface delamination dominates particle attrition throughout the whole process, and bulk fracture is the dominant mechanism only in the deceleration stage. Based on the Gwyn equation, a new attrition model in the form of cubic polynomial is established with the ratio of total attrition rate to unstable attrition rate P as a parameter. The model has high accuracy and repeatability and is suitable for various fluidization conditions. It can effectively describe the attrition process and change rule of particles and reasonably predict the fluidization attrition rate of particles.

In this study, we synthesized eight palladium-based catalysts using two carriers, ZrO₂ and MCM-41. These catalysts were used for the degradation of condensed tannins extracted from larch bark. The average polymerization degree and degradation rate of the products were used as indicators to evaluate the efficiency of degradation. The effects of different Pd:Cu loading ratios under the same carrier conditions and the effects of different carriers under the same Pd:Cu loading ratio were investigated. The results revealed that when the carrier was kept constant, the Pd:Cu ratio of 1:1 exhibited the highest efficiency in degrading condensed tannins. Moreover, when the Pd:Cu loading ratio was the same, the degradation efficiency was higher when ZrO₂ was used as the carrier. Based on these findings, the catalyst (Pd₁-Cu₁)₅/ZrO₂ (where “1” are the molar ratios of Pd to Cu added during the preparation of the catalyst and where ‘5’ is the mass percentage of Pd/Cu metal to total catalyst, i.e., 5 wt%), with ZrO₂ as the carrier and a Pd:Cu ratio of 1:1, demonstrated the highest degradation efficiency, with a degradation rate of 73.89%. This catalyst successfully reduced the average polymerization degree of condensed tannins from 9.5 to 2.48.

In this study, the adsorption of thiophene compounds (TCs), including thiophene (T), benzothiophene (BT), and dibenzothiophene (DBT), from model fuels was investigated using modified activated carbon (AC). The model fuel, prepared as a single-solute model at a concentration of 2000 ppm based on a mixture concentration of 3000 ppm, served as the basis for the adsorption experiments. Additionally, an examination of thiophene adsorption from commercial fuels, specifically kerosene, was conducted. Experimental data were used to calculate correlated parameters of adsorption isotherms, kinetic models, and the Fisher factor. The pseudo-second-order model demonstrated the best fit to the experimental data. Notably, the adsorbent consisting of 10% Cu⁺ supported on acid-washed activated carbon (A1CN10) exhibited the highest adsorption capacity for TCs, achieving removal percentages of 78%, 96%, and 100% for T, BT, and DBT, respectively. Various methods were employed to investigate the physicochemical properties of the adsorbents, including N₂ adsorption–desorption surface analysis (BET), scanning electron microscopy (SEM), X-ray diffraction (XRD), and energy dispersive spectroscopy (EDS). Furthermore, the regeneration of the adsorbent was studied using two techniques: agitation and ultrasound.

The high aromaticity of fluidized catalytic cracking (FCC) slurry makes it a superior raw material for the production of high-performance carbon materials. In this study, direct thermal polycondensation of aromatic-rich FCC slurries is conducted to synthesize mesophase pitches with a significant anisotropic content. The effects of stirring speed and the pressurized-atmospheric two-stage reaction on the structure and composition of the products are investigated. Thermal stability analysis using thermogravimetric (TG) test, observation of mesophase content and optical structure through polarized light microscopy, characterization of material composition and molecular structure via Fourier transform infrared spectroscopy (FT-IR) and nuclear magnetic resonance hydrogen spectrum (¹H NMR), as well as comparison of crystal structures using X-ray diffraction (XRD) are performed. The experimental results demonstrate that an increase in the stirring rate leads to a more homogeneous molecular distribution within the reaction system, thereby facilitating molecular contact polycondensation and promoting mesophase growth and development. Furthermore, the pressurized-atmospheric two-stage reaction process also contributes to mesophase development, resulting in products with more cycloalkane structure, improved thermal stability, and optimized optical structure transitioning from mosaic to flow or even domain.

This study aimed to improve the catalytic activity and hydrothermal stability of Cu-SSZ-39 zeolite by coupling it with cerium zirconium oxides (CeZrO_x), which possesses excellent oxidizing ability, and a hybrid catalyst CeZrO_x/Cu-SSZ-39 was prepared. It is found that it exhibited enhanced low-temperature activity, high-temperature activity, and a wider effective temperature range compared to Cu-SSZ-39. Characterization results showed that the CeZrO_x/Cu-SSZ-39 catalyst had a higher concentration of active Cu²⁺ ion species and improved redox properties, which could potentially promote the NH₃-SCR reaction. Additionally, the CeZrO_x/Cu-SSZ-39 catalyst had increased chemisorbed oxygen species on its surface, facilitating the oxidation of NO to NO₂ and enhancing the rate of the SCR reaction. Moreover, even after undergoing hydrothermal aging treatment, the CeZrO_x/Cu-SSZ-39 catalyst exhibited superior catalytic activity and improved hydrothermal stability, surpassing the performance of Cu-SSZ-39. It is found the CeZrO_x coupling allowed the hybrid catalyst to maintain a better specific surface area and pore structure during hydrothermal aging, resulting in reduced activity loss. Therefore, the addition of CeZrO_x enhanced the NH₃-SCR activity of Cu-SSZ-39 zeolite, leading to improved catalytic activity and hydrothermal stability. CeZrO_x/Cu-SSZ-39 catalyst has shown promising aspect for reducing NOx emissions from diesel vehicle exhaust.

Because of the increasingly deteriorating quality of petroleum coke raw materials, abnormal furnace conditions, such as “firing and blasting”, frequently arise during the calcination of petroleum coke with a high powder/coke ratio in a vertical shaft calciner. This poses an urgent technical challenge that needs to be addressed. In iron and steel metallurgy, the burden distribution system is an important way to regulate blast furnace conditions and improve the permeability of a particle packed bed. In this work, advanced burden distribution concepts were introduced into the calcination process of petroleum coke in a vertical shaft calciner. Experimental devices were established to determine the resistance characteristics of a petroleum coke particle packed bed, along with a cold physical model of a 1/8 scale vertical shaft calciner. The influence of particle size and burden distribution methods on the resistance characteristics and particle motion behavior of the petroleum coke particle packed bed was systematically studied. The research findings indicate that both particle size and burden distribution methods significantly impact the resistance characteristics of petroleum coke particle packed beds. The smaller the particle size, the poorer the permeability of the bed. The layered burden distribution, symmetrical burden distribution, and dual-particle mixed conventional burden distribution all contribute to improving the permeability of the petroleum coke particle packed bed in the vertical shaft calciner. Furthermore, employing symmetrical burden distribution in Bed-3, which is packed with petroleum coke particles of diameters −3.2 + 2.5 mm and −1.0 + 0.8 mm, results in the smallest unit pressure drop, at only 1.7% of that of the conventional burden distribution of unscreened raw materials. This is the most effective means of improving the permeability of the bed. During the discharging process, particle size and symmetrical burden distribution have no significant impact on the motion characteristics of petroleum coke particles in the vertical shaft calciner. In general, in the calciner area, particles primarily move in a plug flow pattern and gradually transform into funnel flow in the cooling water jacket area. These research results provide the theoretical basis for addressing the technical challenges associated with powder coke calcination in vertical shaft calciners through reasonable burden distribution methods for fine and coarse particles.

The adsorption behavior of NH₄⁺ and Mg²⁺ at kaolinite surfaces was investigated by using molecular dynamics (MD) simulations, considering the factors such as ion concentration, NH₄⁺/Mg²⁺ mixing ratio, and layer charge of kaolinite. The results showed that the increase in ion concentration did not affect the adsorption modes of NH₄⁺ and Mg²⁺ ions but promote the increase in the adsorption capacity. The total adsorption capacities of Mg²⁺ and NH₄⁺ were 3.25 × 10⁻⁶ and 2.85 × 10⁻⁶ μmol·mm⁻² at the ion concentration of 1.5 mol·L⁻¹, respectively. When NH₄⁺ and Mg²⁺ were co-adsorbed, they could inhibit the adsorption of each other at the surface of kaolinite, except that the inner-sphere (IS) adsorption of NH₄⁺ at aluminum hydroxyl (Al–OH) surface could be enhanced by the presence of Mg²⁺. Both NH₄⁺ and Mg²⁺ tended to adsorb at the siloxane (Si–O) surface of kaolinite rather than Al–OH surface. When layer charge occurred in kaolinite, a small number of Mg²⁺ began to adsorb in the IS complexes at 1.7 and 2.3 Å above the Al and O atoms of the lattice-substituted tetrahedra of the Si–O surface, and at 1.7 Å above the hexahedra of the Al–OH surface. However, most of NH₄⁺ were adsorbed in IS complexes at 1.7 Å above the center of the oxygen six-membered ring of the Si–O surface and above the hexahedron of the Al–OH surface. The adsorption capacity of Mg²⁺ changed little with the increase of layer charge density, while the IS and total adsorption capacity of NH₄⁺ increased significantly.

Recovering ethane from natural gas involves significant energy consumption. Globally, the recycle split vapor process (RSV) is widely adopted as an efficient method for ethane recovery. Nonetheless, one major challenge faced by the RSV process is the lack of adequate heat integration, despite its overall effectiveness. In this article, we investigate the heat integration of the RSV process and propose two novel ethane recovery processes: the recycle split vapor process with direct heat integration of the feed gas (RSV-DTI) and the recycle split vapor process with split heat integration of the feed gas (RSV-SHI). A comparative analysis is conducted among these three processes, focusing on integrated energy consumption, exergy efficiency, and economic investment. The study's findings reveal the following: (1) The RSV-DTI process distinguishes itself with its reduced energy consumption, enhanced stability, and minimized refrigerant usage. In comparison to the RSV process, the RSV-DTI process achieves a reduction of over 15% in total compression duty and a remarkable decrease of 68% in propane usage. (2) Electricity emerges as the predominant energy consumed in the ethane recovery process, and the RSV-DTI process significantly improves upon this aspect. Notably, the RSV-DTI process incurs the lowest investment cost, yielding a swift payback period of approximately 1 year for the plant. The characteristics of the RSV-DTI process are investigated, and the effect of changes in feed gas conditions on the heat integration of the RSV-DTI process is analyzed. The characteristics of the RSV-DTI process show the following: (1) Different pressures of feed gas existing in the main cold box have different minimum heat integration temperatures (MHIT). When the feed gas temperature is lower than the MHIT, heat integration becomes difficult, and the heat energy can be supplied by hot liquid propane at 48°C. When the feed gas temperature is higher than the MHIT, changes in feed gas temperature have little effect on the process, only affecting the external gas temperature. (2) The heat transfer duty of the demethanizer sideline outlet stream is affected by the feed gas pressure. To enhance heat integration, it is recommended to set the heat transfer duty of the low-temperature sideline outlet stream (DLTSS) between 40% and 90% of the reboiler duty and the heat transfer duty of the high-temperature sideline outlet stream (DHTSS) between 40% and 75% of the reboiler duty.

For the in situ growth method, the reaction time is important because increasing the reaction time may make it possible for the crystallized ZIF-8 to fully cover the GO sheets; the excess of ZIF-8 particles reduces the aspect ratio of the GO sheet. The reaction time will significantly change the morphology, affecting the composite's ability to absorb selective gas and, in turn, affect the gas selectivity. The present work identifies the reaction time for in situ growth of ZIF-8 nanoparticles on GO sheets. The composite was synthesized at different reaction times of 2, 4, 6, and 8 h and incorporated into the PSF matrix. The fabricated membranes were characterized by FTIR, TGA, SEM, and XRD. The novel synthesized reaction time (6 h) was identified for better enhancement of CO₂/CH₄ separation. For pure gas studies, the results investigated that the CO₂ permeability and CO₂/CH₄ selectivity were increased by 223% and 98%, respectively, compared with plain PSF membrane. In mixed gas (CO₂/CH₄) studies, the CO₂ permeability and CO₂CH₄ selectivity were increased by 349% and 854%, respectively, compared with plain PSF membrane. Hence, the in situ growth method helps synthesize MOF@GO composites in the application of gas separation.

In this study, UiO-66 was employed for the first time as an adsorbent to separate phenolic acid analogues, specifically 4-hydroxyisophthalic acid and salicylic acid, from impurities. Synthesized in-house, UiO-66 was shown to exhibit high selectivity towards 4-HIPA/4-HBA and SA/4-HBA when a molar equivalent of acetic acid modulator to terephthalic acid was set at 44. The adsorption capacities for 4-HBA, 4-HIPA, and SA were determined to be 56.34, 55.02, and 60.34 mg/g, respectively. Furthermore, it was observed that after six regeneration cycles, the adsorption capacity for 4-HBA remained nearly unchanged, whereas those for 4-HIPA and SA decreased by 5.6% and 2.6%, respectively. FTIR and XPS analyses revealed that all three compounds were adsorbed at the same dominant Zr cluster site on UiO-66, primarily through hydrogen bonding and electrostatic interaction. Dynamic adsorption experiments revealed that 4-HBA was the first to elute, maintaining the residual contents of 4-HIPA and SA below 0.1 wt%. Compared to traditional separation techniques, this paper provided a simple and effective method to purify industrial grade 4-hydroxybenzoic acid.