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This study investigates the cradle-to-gate life cycle assessment of four acrylic acid production routes. Acrylic acid, an important industrial chemical, is currently produced using fossil fuel-based propylene but it can be sustainably produced from biodiesel derived glycerol through different pathways that involve intermediates such as acrolein, allyl alcohol, or lactic acid. Environmental impacts, including global warming potential, water footprint, acidification, eutrophication, ozone layer depletion, photochemical smog, and human toxicity, are evaluated. Glycerol-based processes exhibit significant environmental impacts mainly due to the energy-intensive production of epichlorohydrin-derived glycerol. The total potential global warming for glycerol-based processes having intermediates allyl alcohol, lactic acid and acrolein, was 1.67 × 105, 1.80 × 105 and 1.34 × 105 kg CO2 eq. FU-1 respectively, with epichlorohydrinderived glycerol, whilst this value was 0.552 × 105 kg CO2 eq. FU-1 for the propylene-based process. However, changing the source of glycerol to purified crude glycerol from the biodiesel industry results in a considerable reduction of the environmental impact. A sensitivity analysis using the two-factor interaction (2FI) model showed that the global warming potential varies from 0.676 × 105 to 1.45 × 105 kg CO2 eq. FU-1 depending on the purification method used to purify crude glycerol and the glycerol content in the crude glycerol. It showed that a vacuum distillation purification process with 50% glycerol content had the least global warming values. This assessment provides insights into environmental performance trade-offs, guiding efforts towards more sustainable acrylic acid production and emphasizing the potential of using by-products from other industries to enhance the sustainability in chemical production processes. [ABSTRACT FROM AUTHOR]

Molecular transport is an important aspect in metal–organic frameworks (MOFs) as it affects many of their applications, such as adsorption/separation, drug delivery and catalysis. Yet probing the fundamental diffusion mechanisms in MOFs is challenging, and the interplay between the MOF's features (such as the pore structure and linker dynamics) and molecular transport remains mostly unexplored. Here, the pulsed-field gradient nuclear magnetic resonance (PFG NMR) technique is used to probe the diffusion of several probe molecules, i.e., water, xylenes and 1,3,5-triisopropylbenzene (TIPB), within the UiO-66 MOF and its derivatives (UiO-66NH2 and UiO-66Br). Exploiting differences in the size of probe molecules we were able to probe the diffusion rate selectively in the different pore environments of the MOFs. In particular, when relatively small molecules, such as water and small hydrocarbons, were used as probes, the PFG NMR log attenuation plots were non-linear with two distinctive diffusion regions, suggesting faster diffusion in the inter-crystalline space and slower diffusion within crystal aggregates, the latter occurring mostly inside the framework of the MOFs. Conversely, experiments with a larger probe molecule, i.e., TIPB, with a kinetic diameter of 0.95 nm, which makes it unable to access the framework windows of the MOF crystals, showed linear PFG NMR log attenuation plots, which indicates diffusion occurring in a single environment, most likely in the inter-crystalline space. Analysis of the apparent tortuosity values of the systems under investigation highlights the role of linker functionalisation in influencing the molecular diffusion of the probe molecules, which affects both intra-molecular interactions and pore accessibility within the MOF crystals. The findings of this work demonstrate that the diffusion behaviour of probe molecules within MOFs is influenced by the pore size, structure, functionalisation of the MOF linker and molecular interactions. Our study contributes to further advance the understanding of mass transport in MOFs by PFG NMR and provides insights that can inform the design and optimisation of MOF-based materials for various applications. [ABSTRACT FROM AUTHOR]

The behaviour of multiple fluid phases within a porous medium is hard to predict. NMR measurements offer an excellent tool to probe such systems in a fast and non-invasive way. Such systems can be relevant to hydrocarbon recovery, catalysis, and CO2 and H2 geo-storage, among others. Since electrolyte solutions are always present in subsurface reservoirs, understanding their behaviour within porous media is highly important. In this study, we use NMR relaxation and diffusion methods to investigate the diffusion coefficients and strength of interactions between alumina surfaces and brines at various NaCl concentrations, focusing on the effect of salt concentration on transport and interactions within the porous structure. Furthermore, we study the spontaneous displacement of dodecane, a model hydrocarbon, from the same alumina pellets using the same brine solutions. Results show that brines of lower salinity consistently displace more dodecane in total, after soaking dodecane-saturated pellets in a brine solution for several days. This indicates that increased salt concentrations can reduce wettability towards the aqueous phase in simple metal oxide surfaces and highlights the capabilities of NMR to efficiently study such systems. [ABSTRACT FROM AUTHOR]

The tobacco waste generated from the tobacco agriculture and industry, including the discarded stem and leaf, often needs dehydration pretreatment before thermal conversion utilization. In order to study the water activity and migration of tobacco waste during the pretreatment process, TG-NMR (Thermogravimetric Nuclear Magnetic Resonance) was used to obtain the drying curves and LF-NMR (Low Field Nuclear Magnetic Resonance) T2 inversion spectrum at each stage of tobacco drying. Meanwhile, the variation pattern of pore distribution during the dehydration process of two types of tobacco waste has been obtained. Combined with the pore distribution changes, a possible spatial migration mode of water was proposed. The change of adsorption energy of water during tobacco drying was calculated, and verified the above hypothesis. This study results provide reference for the optimization of dehydration pretreatment process for different tobacco waste in order to reduce energy consumption during recycling of tobacco biomass. [ABSTRACT FROM AUTHOR]

Photoreforming of lignocellulose biomass is widely recognised as a challenging but key technology for producing value‐added chemicals and renewable hydrogen (H2). In this study, H2 production from photoreforming of organosolv lignin in a neutral aqueous solution was studied over a 0.1 wt % Pt/TiO2 (P25) catalyst with ultraviolet A (UVA) light. The H2 production from the system employing the lignin (~4.8 μmol gcat−1 h−1) was comparable to that using hydroxylated/methoxylated aromatic model compounds (i. e. guaiacol and phenol, 4.8–6.6 μmol gcat−1 h−1), being significantly lower than that from photoreforming of cellulose (~62.8 μmol gcat−1 h−1). Photoreforming of phenol and reaction intermediates catechol, hydroquinone and benzoquinone were studied to probe the mechanism of phenol oxidation under anaerobic photoreforming conditions with strong adsorption and electron transfer reactions lowering H2 production from the intermediates relative to that from phenol. The issues associated with catalyst poisoning and low photoreforming activity of lignins demonstrated in this paper have been mitigated by implementing a process by which the catalyst was cycled through anaerobic and aerobic conditions. This strategy enabled the periodic regeneration of the photocatalyst resulting in a threefold enhancement in H2 production from the photoreforming of lignin. [ABSTRACT FROM AUTHOR]

CO2 utilization is an important process in the chemical industry with great environmental power. In this work we show how CO2 and H2 can be reacted to form methanol on an iron(II) center and highlight the bottlenecks for the reaction and what structural features of the catalyst are essential for efficient turnover. The calculations predict the reactions to proceed through three successive reaction cycles that start with heterolytic cleavage of H2 followed by sequential hydride and proton transfer processes. The H2 splitting process is an endergonic process and hence high pressures will be needed to overcome this step and trigger the hydrogenation reaction. Moreover, H2 cleavage into a hydride and proton requires a metal to bind hydride and a nearby source to bind the proton, such as an amide or pyrazolyl group, which the scorpionate ligand used here facilitates. As such the computations highlight the non‐innocence of the ligand scaffold through proton shuttle from H2 to substrate as an important step in the reaction mechanism. [ABSTRACT FROM AUTHOR]