ACS Engineering Au
ISSN / EISSN : 2694-2488 / 2694-2488
Published by: American Chemical Society (ACS) (10.1021)
Total articles ≅ 16
Latest articles in this journal
ACS Engineering Au, Volume 1; https://doi.org/10.1021/egv001i001_1523131
ACS Engineering Au, Volume 1, pp 1-3; https://doi.org/10.1021/acsengineeringau.1c00024
ACS Engineering Au, Volume 1; https://doi.org/10.1021/egv001i001_1523132
ACS Engineering Au, Volume 1, pp 7-38; https://doi.org/10.1021/acsengineeringau.1c00011
The paper comprehensively reviews durable polylactic acid (PLA)-based engineered blends and biocomposites supporting a low carbon economy. The traditional fossil fuel derived nonrenewable durable plastics that cannot be circumvented have spawned increased environmental concerns because of the continuous rise of their carbon footprint during processing and disposal. It is anticipated that the production of biodegradable and nonbiodegradable (durable) plastics from the year 2020 to 2025 will rise ∼47% and ∼21%, respectively. The carbon footprint can be reduced in durable (nonrenewable) plastics by decreasing or replacing the “fossil carbon” content with “renewable carbon” content. The replacement will enable us to attain a sustainable environment, a low carbon footprint, energy security, and effective resource management. Thus, PLA-based durable products need to be developed with an enhanced service life that strikes a balance between environment-friendliness and product performance for engineering high-performance applications. The recent progress for enhancing the durability of PLA-based products consisting of hybrid nonrenewable and renewable carbon has been attained by incorporating synthetic plastics, synthetic fibers (glass and carbon), natural fibers, and other biofillers (biocarbon). Further, the effects of additives such as initiators, nucleating agents, chain extenders, compatibilizers, impact modifiers, and toughening agents to prepare such blends and composites have been discussed. This Review further critically examines the advances centering on processability, heat resistance, flame retardancy, strength, and toughness. In addition to that, current and prospective applications such as automotive, electronic, medical, textile, and housing of PLA-based products are discussed. However, the challenges for tailoring durable PLA-based products that still need to be addressed, such as improved processability, striking stiffness–toughness balance, enhanced heat resistance, and improved interfacial adhesion between the polymer–polymer, polymer–filler, and hybrid polymer–filler in respective polymer blends, composites, and hybrid composites, are summarized and analyzed in this Review. Hence, the opportunities for improvement to overcome the challenges lie ahead.
ACS Engineering Au; https://doi.org/10.1021/acsengineeringau.1c00015
In this work, we present a hybrid fundamental-empirical model to monitor and predict the catalyst lifetime of an operating industrial reactor. The hybrid model combines a fundamental adiabatic reactor model to calculate the activity of the catalyst bed with an empirical partial least-squares model to predict the catalyst activity at different operating conditions. A baseline model was trained on process data and validated separately using analytical data, showing good agreement between the measured reactant breakthrough of the reactor train and the predicted values from the model over 18 years of continuous operation of four industrial production reactors. To implement the model for catalyst activity monitoring, the model must closely match the current catalyst charge performance. Therefore, the baseline model parameters are updated automatically with new plant data using a filter algorithm.
ACS Engineering Au; https://doi.org/10.1021/acsengineeringau.1c00016
Pt and Pd supported on beta zeolites, with different silica to alumina ratios (SARs), are examined in the form of diesel oxidation catalysts (DOCs) for the oxidation of CO, NO, C3H8, and C3H6. The effect of SARs on the physicochemical properties of the catalysts, their subsequent oxidation activity, and sulfur tolerance was investigated. A beta zeolite with a high SAR has low acidity and high hydrophobicity, which induces the agglomeration of either Pt or Pd in the catalysts during preparation and thermal treatment. The effect of sintering is more severe on Pt than on Pd catalysts. High-SAR zeolites retained Pt in a more metallic fraction in the obtained catalysts, whereas this effect was not significant for the Pd-based catalyst, wherein Pd exists mostly in the oxide form. High-SAR Pt/BEA and Pd/BEA catalysts exhibit better conversion of CO, NO, C3H8, and C3H6 than low-SAR catalysts. A linear relationship for turnover frequency (TOF) with SAR (and with average particle size) was found for all four oxidation reactions, namely, the higher is the SAR, the higher is the TOF. This suggests that the catalysts are tailorable by adjusting the SAR of the zeolite supports. A five-cycle test indicated that zeolite-based catalysts have greater stability than alumina-based catalysts. The activity for NO oxidation was very stable for the high-silicious Pt/BEA catalyst with time-on-stream, which was not the case for the Pt/Al2O3 catalyst. The Pd/BEA catalysts were more susceptible to sulfur poisoning than their Pt counterparts; however, they were easily regenerated. Also, the Pt/BEA catalysts were effectively regenerated, especially for the highest SAR.
ACS Engineering Au; https://doi.org/10.1021/acsengineeringau.1c00014
Isolated Ni(II) sites supported on zeolites and other porous materials transform in situ during alkene dimerization to form active Ni(II)-alkyl centers, and their density influences the kinetic orders and mechanisms of deactivation of Ni-Beta zeolites during ethene dimerization (453 K). Ni-Beta containing high Ni site densities shows deactivation rates that are second-order in Ni, consistent with a dual-site deactivation mechanism involving the formation of unreactive Ni-alkyl-Ni intermediates, as confirmed by DFT calculations. Under the same reaction conditions, by contrast, Ni-Beta containing low Ni site densities shows deactivation rates that are first-order in Ni, consistent with a single-site deactivation mechanism reflecting inhibition by strongly bound intermediates derived from heavier alkene oligomers. On Ni-Beta containing low Ni site densities, cofeeding H2 along with ethene results in a higher number of Ni(II)-alkyl intermediates formed at initial reaction times and a concomitant change to deactivation kinetics that become second-order in Ni. These findings reveal the strong influence of the density of active Ni(II)-alkyl centers in porous supports, which depends both on material properties and reaction conditions that generate active centers in situ, on the kinetics and mechanisms of deactivation during alkene oligomerization.
ACS Engineering Au; https://doi.org/10.1021/acsengineeringau.1c00010
Hydrothermal processes are promising technologies for an efficient valorization of wet biomass feedstocks or wastes. Their performance strongly depends on the composition of the feedstock, and methods to analyze such complex mixtures along with the produced effluents are in constant progress. Herein, catalytic hydrothermal gasification (cHTG) was used to valorize process water produced from the hydrothermal liquefaction of pine wood. A detailed analysis of the effluents and streams at various points of the process was performed. About 54% of the feed’s chemical energy could be transferred to synthetic natural gas while an excellent extraction of minerals (98%) into a concentrated brine (27 wt % dry matter) could be achieved. The low gasification efficiency observed and the origin of the 41% and 44% loss of chemical energy and carbon in the brine, respectively, were investigated by high-pressure liquid chromatography–high-resolution mass spectrometry (HPLC–HRMS) analysis of the feed and the effluents from the salt separator. This allowed for identifying mono- and polycarboxylates accounting for 71% of the carbon in the brine. Increasing temperature in the salt separator to favor decarboxylation reaction was identified as pivotal to improve synthetic natural gas yields, with a 20-fold decrease of carboxylate concentration being reached with a temperature rise from 723 to 768 K. The use of two new approaches to estimate the high heating value (HHV) of this feed rich in volatile organic compounds is also reported.
ACS Engineering Au; https://doi.org/10.1021/acsengineeringau.1c00007
Alkaline industrial wastes (e.g., slags: ordered crystalline solids, and fly ashes: disordered solids) represent abundant reservoirs of elements such as silicon and calcium. Rapid elemental extractions from these wastes, however, have often relied on the use of “stoichiometric additives” (i.e., acids or bases). Herein, we demonstrate that acoustic stimulation enhances the release of network-forming Si species from crystalline blast furnace slags and amorphous fly ashes at reaction temperatures less than 65 °C. These additive-free enhancements are induced by cavitation processes which reduce the apparent activation energy of solute dissolution (Ea, kJ/mol) by up to 40% as compared to unstimulated conditions. Because of the reduction in the apparent activation energy, acoustic stimulation features an energy intensity that is up to 80% lower in promoting dissolution, as compared to other additive-free methods such as enhancing the solute’s surface area, introducing heat, or convectively mixing the solvent. Based on atomic topology analysis, we show that the reduction in apparent dissolution activation energy upon acoustic stimulation scales with the number of weak topological constraints per atom in the atomic network of the dissolving solute, independent of their ordered or disordered nature. This suggests that sonication breaks the weakest constraints in the solute’s atomic network, which, in turn, facilitates dissolution. The results suggest the ability of acoustic stimulation to enhance waste utilization and circularity, by enabling efficient resource extraction from industrial wastes.
ACS Engineering Au; https://doi.org/10.1021/acsengineeringau.1c00012
Hydrate formation could be looked upon as multicomponent and multiphase reaction which is heavily dependent on mass transfer and heat transfer limitations even under favorable thermodynamic conditions. Gas uptake measurement is one of the easiest ways to understand the kinetics of hydrate growth. In a typical gas uptake measurement, one could easily observe three phases of hydrate formation: in phase-I, hydrate forming gas dissolves in the liquid phase which leads to hydrate nucleation; in phase-II, fast hydrate growth is observed; and in phase-III, hydrate grows slowly for relatively longer time periods. In a batch reactor, a slow down in hydrate growth rate as seen in phase-III is either due to a drop in the pressure of the reactor during hydrate growth and/or reduced mass transfer due to hydrate accumulation at the interface. In this work, a model is developed to predict phase-II events. The model proposed is based on an earlier model available in the literature which captured the intrinsic kinetics of gas hydrate growth for a semibatch reactor. Model discussed in the current study works for batch and semibatch reactor, it captures the kinetics for different stirrer speeds, water to gas ratios and different thermodynamic conditions. Experimental validation was done in a batch reactor at 274 K and 6 MPa with methane as the hydrate forming gas. A batch reactor with two different stirrer arrangements, different water-to-gas ratios, and different stirrer speeds were considered, and the mass transfer limitations for both the reactor configurations were studied. Further, a comparison study with the existing model and the modified model (current study) showed that the current model can be extended to other reactor types.