Chemical Engineering and Processing - Process Intensification最新文献

DME synthesis by direct CO₂ hydrogenation was studied on physical mixture of commercial CuZnO/Al₂O₃ (CZA) and in-house synthesized PTA (phosphotungstic acid)/γ-Al₂O₃ catalysts. Effects of PTA loading (0–50 % by mass) and relative amounts of the catalysts on CO₂ conversion and DME yield were investigated. The process was intensified through integration of in-situ steam separation by Zeolite 3A (Z3A) adsorbent mixed with the catalysts. Experiments were run at 498 K, 30 bar, H₂:CO₂=3:1 and GHSV=1750 h⁻¹ (based on CZA catalyst). Optimum PTA loading and CZA:PTA/γ-Al₂O₃ mass ratio were 30 % and 1:2, respectively, that gave ∼21 % CO₂ conversion and 6.3 % DME yield. These values remained below the respective thermodynamic limits (28.5 % and 21 %), which were exceeded upon adsorbent integration. Catalytic performance depended strongly on adsorbent quantity studied at the catalyst (CZA+PTA/γ-Al₂O₃):adsorbent mass ratio range of 1:0.33–4. Catalysts and the adsorbent remained stable during the pressure swing driven adsorption-regeneration cycles. Sorption assistance at catalyst:adsorbent ratio=1:4 increased catalyst productivity from 5.5×10⁻³ to 2×10⁻² kg_DME h⁻¹ kg_cat⁻¹. The latter value was comparable to those of the sorption enhanced CO₂+CO hydrogenation systems due to the PTA-based dehydration catalyst with strong acidic features and was promising when the strong thermodynamic limitations of CO₂-DME conversion was considered.

Microwave-assisted extraction (MAE) of natural antioxidants from food waste (FW) offers an economically appealing waste management strategy. However, MAE from mixed FW has received limited attention. We characterize five single waste streams (apple, coffee, olive, tomato, and potato peel waste) and study MAE of phenolic acids from select feedstocks and mixtures. This library of materials enables us to unravel the relationship of FW composition and physical properties with dielectric properties, heating, and extractive yields. Protein, ash, and moisture contents affect dielectric properties the most. Our study unveils the significance of moisture in free (> 20 wt%) and bound states (< 20 wt%) on FW dielectric properties, heating, and target acid yields (at least 33 % enhancement). Microwaves primarily heat the solvent (dimethylformamide) due to its superior dielectric properties compared to FW (dry and moist, single and mixtures) at ≤ 0.05 solid-to-liquid ratio (g/mL). High moisture content (> 20 wt%) provides higher phenolic yields at lower temperatures (< 100 °C) and shorter times (≤ 10 min) due to enhanced heat and mass transfer by microwaves. Further, our data indicates significant interactions between mixed FW components that drive 2–3x higher yields than those predicted from a simple additive model from single component results. Our work provides new insights for developing versatile MAE strategies to treat mixed FW feedstocks.

The influence of A. ferrooxidans on polymetallic nodules reductive dissolution in the imitated bioleaching medium was investigated. Firstly, the features related to metal extraction and manganese leaching kinetics of the nodule were determined using Fe²⁺ ions as reductants in the presence of A. ferrooxidans. The obtained apparent activation energy is 13.9 kJ mol^-1 for the Mn-reduction. Secondly, the courses of the dissolution of polymetallic nodules were measured by multi-transient and steady electrochemical methods. The obtained results indicated that in A. ferrooxidans simulated bio-leaching system, the reductive leaching of polymetallic nodules is characterized by step-step processing, and the interface chemical reaction is the rate-controlling process. The interface exchange reactions are expressed in a two-electron transfer process corresponding to the cathodic conversion of MnO₂/Mn²⁺, while in one-electron transfer of Fe²⁺to Fe³⁺ for anodic response with the presence of Fe³⁺ ions and A. ferrooxidans. Based on this study's findings, the role of A. ferrooxidans in the polymetallic nodule reductive dissolution is concluded with three effects: A. ferrooxidans as electron-proton carrier or buffer facilitate interfacial species transfer; A. ferrooxidans as catalyzer for the transformation of Fe³⁺/Fe²⁺pair cause Mn-oxide reducing quickly; A. ferrooxidans as enhancer promote intermediate and products migration and transformation.

Piezo-coupled catalysis, which is driven by dual-frequency ultrasound (DFUS) at high frequencies (>100 kHz), has emerged as a promising technique for intensifying the oxidation processes in aqueous media. This study aimed at evaluating the performance of high-frequency DFUS (0.12 + 1.7 MHz) coupled with ZnO microparticles (1 µm) and persulfate (S₂O₈²⁻) for disinfection of filtered natural surface water, spiked with E. coli and E. faecalis, as well as unfiltered natural water with indigenous microflora. Despite the longer treatment times required (as compared to deionized water), this hybrid system provided the fastest inactivation, exhibiting a synergy between DFUS+ZnO and DFUS+S₂O₈²⁻ processes and a high energy-efficiency (231.5 and 91.3 CFU/J for E. coli and E. faecalis, respectively). The obtained results revealed the feasibility of DFUS-driven piezo-coupled catalysis using persulfate for advanced water disinfection.

In the face of depleting conventional oil and natural gas reserves, the exploitation of shale oil resources increasingly important. However, the high stability of shale oil emulsions presents a significant challenge to its extraction. In this paper, the differences between shale oil and conventional crude oil and the reasons for the stability of shale oil emulsions were explored. In addition, different dehydration technologies for shale oil emulsions were compared and optimum operating parameters were determined through laboratory-scale experiments. The results show that shale oil emulsions contain much smaller droplets (< 2.25 μm) compared with conventional crude oil emulsions. Further, the high wax content of shale oil allows it to form a high-strength interfacial film at the oil-water interface under the combined action of fracturing fluids and natural emulsifiers, making the emulsion highly stable. Demulsification experiments showed that the use of high-frequency alternating current (AC) pulsed electric fields is an effective method for breaking shale oil emulsions. The optimal demulsification parameters were found to be an electric field frequency of 4 kHz, a field strength of 150 kV·m^-1, a residence time of 50 min, an operating temperature of 55 °C, and a demulsifier concentration of 100 ppm. Under these conditions, the dehydrated shale oil was able to meet the standards for commercial crude oil.

Membrane reactors have been proven to be effective in producing nanoparticles with reduced polydispersity indices. Recently, our group has incorporated this technology into the synthesis of ferromagnetic nanoparticles. In the initial phase, we conducted post-synthesis stabilization experiments to assess the performance of various polymeric agents. Polyacrylic acid (PAA) was chosen because of its notable affinity for the functional groups on the nanoparticle surface. Subsequently, in situ stabilization experiments were conducted using a membrane reactor, with variations in PAA addition flow rates ranging from 0.33 to 1.5 mL/min and maturation times in an ultrasonic bath ranging from 0.5 to 2 h. The samples were characterized in terms of their hydrodynamic diameter, polydispersity, and Z-potential. Notably, the smallest particle size was achieved at the intermediate point with a PAA flow rate of 0.66 mL/min. However, the influence of maturation time did not follow a predictable pattern; the most favorable characteristics, based on the analyzed variables, were observed at 1.5 and 2 h.

Proton exchange membrane (PEM) electrolytic hydrogen production has the advantages of high current density, high operating pressure, wide power regulation range and so on. It has good adaptability to wind and photovoltaic power with high volatility and recognized as an important way to solve the effective utilization of renewable energy. In PEM electrolyzer cell (PEMEC), anode flow field plate plays a crucial role in the process of water electrolysis to produce oxygen, which affects the of gas and liquid transfer. Among them, the channel blockage caused by bubble retention is an important factor limiting the performance of PEMEC. In this paper, an interdigital flow field plate is designed based on the plant leaf vein system. The two-phase flow behaviors within the interdigital flow field channel are studied. The results show that the interdigital flow field plate is superior to the traditional serpentine flow field in terms of electrolytic efficiency and voltage loss. The reaction kinetics rate is accelerated, the overall ohmic resistance is reduced by about 4.8 %, and the hydrogen production is increased by about 9.1 %. The above research can provide guidance for the structural improvement and performance improvement of PEMEC.

An ecologically beneficial process of vapor-recompression-assisted distillation was proposed, based on the conventional heterogeneous azeotropic distillation, for separating n-butanol and water. The heat integration was also adopted to improve the energy utilization rate of the process. The sequential iterative approach optimized the parameters relating to all those processes. The heat-integrated vapor-recompression-assisted heterogeneous azeotropic distillation arrangement reflects its economic superiority, for reducing total annual cost by 15.121 % and CO₂ emissions by 78.860 % and enhancing second-law efficiency by 102.156 %. An exergy analysis was performed on the intensified processes, which showed that the exergy increases in the configuration coupled with vapor recompression and heat integration were higher than those with only vapor recompression. Dynamic control characteristics were investigated for these three intensified configurations, and both product compositions were well controlled when confronting 20% production rate and feed composition disturbances, and no composition measurement loops were noted in the proposed control schemes.

Esters of acrylic acid have many industrial applications, but existing industrial processes are not economical. Ethyl acrylate, a precursor to polymers and other chemicals is one of them. The existing method of production of ethyl acrylate by esterification of acrylic acid with ethanol using a homogeneous catalyst and reactor-distillation combination has limitation in terms of product purity, corrosion and existence of possible side reactions. The present work proposes a novel reactive distillation (RD) column configuration for ethyl acrylate production, with 99.99 % acrylic acid conversion and 99.99 % ethyl acrylate purity with no effluent stream. The proposed configuration is analyzed using Aspen Plus steady-state simulation software. Sequential iterative sensitivity analysis is performed to obtain all structural and operating parameters leading to a minimum Total Annual Cost (TAC). The result shows that, there is 10.8 % improvement in the purity of aqueous stream using RD configuration compared to existing method and the overall TAC of the process at desired conditions is 87.77 × 10³ $/year.

Carbon dioxide (CO₂) is widely acknowledged as the primary contributor to the greenhouse effect. Microchannel reactors can be used for enhancing chemical processes, solving the problems of limited gas-liquid mass transfer, and have significant advantages in CO₂ capture. In this study, the deep eutectic solvent (DES) prepared by mixing ionic liquid (1-ethyl-3-methylimidazolium chloride, EmimCl) and Ethanolamine (MEA) in a molar ratio of 1:1 was selected for CO₂ capture in a microchannel. The structure and physical properties of the DES were investigated, and the effects of gas and liquid flow rates, water content, and CO₂ concentration on the CO₂ absorption properties were analyzed. The increase of the water content not only significantly reduces the viscosity of DES, but also improves the CO₂ absorption performance. In addition, the CO₂ absorption mechanism of this DES has been obtained by the NMR spectrum, showing that the absorption process is a rapid chemical absorption process between CO₂ and MEA. The Cl^- of EmimCl could stabilize the protonated amine and prevent it from further reacting with MEACO₂^-, furthermore increasing the CO₂ absorption rate.