Industrial & Engineering Chemistry Research最新文献

Amine-impregnated materials are considered crucial adsorbents for carbon capture from wet streams due to the enhancement of CO₂ adsorption in the presence of moisture. Nevertheless, there have been limited studies conducted to explore the coadsorption of water vapor and CO₂ on impregnated amines, resulting in challenges when modeling the binary adsorption behavior. In this study, single and binary component isotherms for the adsorption of CO₂ and H₂O on polyethylenimine-impregnated silica were analyzed and modeled using a realistic interactive Langmuir-BET (RBET) adsorption theory. Compared with single-component adsorption results, CO₂ adsorption capacities on amines were found to be enhanced by moisture, whereas water loadings were reduced when CO₂ was present. The RBET model, incorporating the interactions between CO₂ and adsorbed water, demonstrated excellent accuracy in describing the observed adsorption behavior. The binary adsorption capacities under different conditions were further calculated to guide the practical application of amine-impregnated adsorbents for carbon capture.

The operational flexibility of a chemical process refers to its ability to maintain feasible operations despite uncertain deviations from the nominal conditions. It is an important characteristic that ensures the system’s adaptability and resilience in the face of changing operating conditions. To quantify the feasible region and evaluate the flexibility of a given process design, the volumetric flexibility index is used by calculating the ratio between the hypervolume of the feasible region and the hypervolume of the region that encompasses all possible combinations of expected uncertain parameters. To deal with general problems involving nonlinear constraints, nonconvex, nonsimply connected, or high-dimensional feasible regions, we introduce a novel method that utilizes a deep regression network and a classification network to achieve a reliable and efficient evaluation of the flexibility index. We demonstrate the effectiveness of the proposed method through multiple numerical illustrations and case studies.

To enhance deoxygenation and cracking performance of microalgal biodiesel to produce a jet fuel-range hydrocarbon blend, an efficient Ni-carbon composite was prepared by pyrolyzing Ni-based metal–organic frameworks (Ni-1,3,5-benzenetricarboxylate, Ni-BTC) for catalytic conversion with a substantially reduced catalyst dosage. Coordinated Ni ions in the Ni-BTC precursor were converted into highly active Ni nanoparticles due to catalyst pyrolysis, while an increased specific surface area of the catalyst facilitated mass transfer in microalgal biodiesel conversion. X-ray absorption fine structure analysis confirmed the formation of Ni–Ni active sites, while density functional theory calculations revealed that the C═C bond was the initial site for the cracking reaction of long-chain fatty acids. The selectivity of jet-fuel-range products in methyl palmitate conversion over the Ni@C₅₀₀ (Ni-BTC pyrolyzed at 500 °C) catalyst increased to 71.46% with a substantially reduced catalyst dosage (the mass ratio of catalyst to reactant was 1:200). The Ni@C₅₀₀ catalyst exhibited excellent performance with high selectivity (71.6%) and conversion efficiency (97.46%) in deoxygenation and cracking of microalgal biodiesel for jet fuel-range hydrocarbon blend production.

Copper complex catalysts exhibit excellent activity for the oxidative carbonylation of methanol to produce dimethyl carbonate (DMC). However, the reaction mechanism over Cu(I) or Cu(II) complex catalysts is not fully understood. In this study, homogeneous CuCl/CuCl₂–NMI-m/n (N = N-methylimidazole; m/n = molar ratio of Cu(I) and Cu(II)) catalysts with organic ligand coordination are designed for oxidative carbonylation. The optimized CuCl/CuCl₂–NMI-0.3/0.7 catalyst showed a TOF as high as 3.4 h^–1 and a DMC selectivity of 67.2% based on oxygen, which were superior to those of CuCl–NMI or CuCl₂–NMI. Our experiments suggested that the high activity and selectivity were assigned to the synergistic effect between Cu(I) and Cu(II), in which Cu(I) and Cu(II) are mainly responsible for the rapid generation of copper carbonyl and copper methoxy intermediates, respectively. This synergistic effect not only enhances the reaction activity but also ensures high DMC selectivity.

Cu-mediated reversible deactivation radical polymerization (RDRP) is investigated as a method to produce (meth)acrylic polymers of high chain-end functionality and well-defined structure, enabling the production of uniform block copolymer materials. The use of inexpensive reagents with scale-appropriate reactor configurations is a key feature in overcoming the hurdles to commercialization. Using methyl acrylate (MA) as a model system, reaction conditions and feeding strategies were optimized in a semibatch system to reach >95% monomer conversion and 70 wt % polymer in solution in 1.5 h with excellent control (Đ = 1.10). It was concurrently demonstrated that prepolymerization in the copper tube reactor could be eliminated while still providing a chain-extendible species, a result that simplifies reactor operation, offers greater flexibility in initiator choice, and improves compositional control of the final product. The conditions developed for the homopolymerization system were applied to produce acrylate-acrylate and acrylate-methacrylate block copolymers, also exploring the influence of block order. Achieving high conversions for each monomer fed, reactions were completed in 4 h or less with no intermediate purification or additional catalyst, thus yielding a scalable method of producing block copolymer materials at Cu levels <100 ppm.

The synthesis of platform molecules from food wastes is a topic of interest for the development of sustainable biorefineries. Starchy food wastes can serve as feedstocks to produce fine chemicals, fuels, and polymers by the hydrolysis of starch and further conversion into platform molecules such as 5-hydroxymethylfurfural (5-HMF) and 5-chloromethylfurfural (5-CMF). Conventionally, the synthesis of 5-CMF has relied on the use of concentrated hydrochloric acid (HCl) as a catalyst. However, recent studies have explored alternative methods, including eutectic solvents containing metal chlorides, which have facilitated 5-CMF production. This study presents a novel approach to synthesizing 5-CMF from starch using eutectic solvents without the need for either HCl or metal chloride additives. The synthesis was conducted using a low transition temperature mixture of choline chloride, citric acid, and boric acid in a biphasic system with dichloromethane as the extracting solvent. The synthesis was optimized using the response surface methodology through a Box–Behnken design. At 100 °C and 90 min of reaction time, up to 17 mol % 5-HMF and 13 mol % 5-CMF were produced, and in the optimized conditions of 120 °C and 135 min, up to 33 mol % 5-CMF with less than 1 mol % 5-HMF was obtained from starch. Moreover, it was shown that the low transition temperature mixture used in this study could be reused at least five times.

Amorphous silica derived from tetraethoxysilane (TEOS) is known for its remarkable properties, including high chemical and thermal stabilities. However, its inherent structure presents challenges for effective CO₂/N₂ separation, owing to the difficulty in controlling the silica pore size, considering the similar sizes of CO₂ (0.33 nm) and N₂ (0.36 nm) molecules. In this study, we investigated the impact of trifluoroacetic acid (TFA) and amine (APTES: 3-aminopropyltriethoxysilyl) concentrations, aiming to leverage tailored silica structures with enhanced CO₂ affinity. Specifically, a two-stage investigation was conducted by first examining the influence of TFA on the pore structure of the TEOS networks, followed by an analysis of the CO₂ separation performance using composite TEOS–APTES membranes in the presence of TFA. While the TEOS (TFA) membrane exhibited a CO₂ permeance of 10^–6 mol m^–2 s^–1 Pa^–1, its CO₂/N₂ permselectivity remained low. However, introducing TFA into the TEOS–APTES structure resulted in a notable transformation of the primary amine (NH₂) groups into amide (−NHCOCF₃) functionalities, along with improved microporous properties. This was confirmed by FT-IR spectroscopy, reversible CO₂ adsorption/desorption, and the high uptake of adsorbed N₂. The resulting composite TEOS–APTES (TFA) membranes with APTES concentrations of 2 and 5 mol % demonstrated enhanced CO₂ permeation properties, achieving a CO₂/N₂ selectivity of 15 and 35, respectively. This improvement is attributed to the increased pore volume and the introduction of amide functionalities (−NHCOCF₃), which exhibit mild affinity for CO₂. These findings suggest that the developed composite (TEOS–APTES) membranes are promising for industrial applications that require efficient CO₂ separation.

Viable thermochemical biorefineries require valuable outputs with optimized carbon distributions. While catalytic refining of biomass pyrolysis oils can produce fuel-grade hydrocarbons, more carbon-efficient pathways are needed to sustainably produce both renewable hydrocarbons─including those suitable for sustainable aviation fuel (SAF)─and carbonaceous solid materials. Bio-oils of sufficient quality and stability can undergo distillation, and catalytic hydrotreatment can upgrade the distillates without the interference of high-molecular-weight coke precursors. To further utilize the residues, we tested solvent liquefaction for upgrading of bio-oil distillate residues. Pyrolysis bio-oils from a lignocellulosic (switchgrass) and an oleaginous/proteinaceous (spirulina) biomass were distilled, and the distillate residues underwent liquefaction at 300 °C in microreactors with various solvents (water, ethanol, NaOH (aq), and formic acid (aq)). Optimal solvent conditions were downselected based on gas chromatography-mass spectrometry (GC-MS) of the products. Larger-scale reactions in optimal solvents (100 mL Parr reactor, 300 °C, 1500 psi) produced oils and hydrochar, the latter of which can be calcined into coke for manufacturing applications. For spirulina oil residues, ethanol-based liquefaction produced a 46% yield of oil; this represents more than double the yield for the NaOH-based liquefaction of switchgrass oil residues (20%). The oils contained straight-chain aliphatic compounds, which can potentially improve the processability for SAF applications.

Cyclopentanone (CP), a cyclic hydrocarbon, is a potential biobased platform chemical for the synthesis of high-density jet fuel range cycloalkanes. The base-catalyzed self-condensation of CP yields 2-cyclopentylidene cyclopentanone (2-CP) and 2,5-dicyclopentylidene cyclopentanone (3-CP). 2-CP has applications in fuels, fragrances, and flavors, and 3-CP is used as a precursor for diesel-grade products. In this study, solid base activated carbon monolith (ACM)-supported hydrotalcite catalysts (HT/ACM) were synthesized using traditional thermal calcination, rehydration, and air plasma techniques and demonstrated for continuous cyclopentanone self-condensation. Among the ACM-supported hydrotalcites, the HT/ACM activated by air plasma at 100 W for 1 min (PHT/ACM-100W) displayed a higher 2-CP space time yield of 641 g L-cat^–1 h^–1 and selectivity of 27% (220 °C, 1 atm, 0.73 min vapor phase contact time). PHT/ACM-100W displayed a higher CP conversion (42%) compared to the unsupported calcined (34%, 500 °C for 4 h) and rehydrated (39.5%, 8 h at 105 °C) hydrotalcite catalysts yet significantly lower space time yields, suggesting low hydrotalcite distribution and loading on the carbon monolith. The plasma-activated carbon monolith-supported hydrotalcite catalysts synthesized in this work are promising alternatives to the thermally activated and rehydrated hydrotalcites for the catalytic upgrading of biobased cyclic and linear ketones.