Exploring the Impact of the Synthesis Variables Involved in the Polyurethane Aerogels-like Materials Design.

This research presents a novel approach to synthesising polyurethane (PUR)-based aerogels at the pilot scale, optimizing synthesis variables such as the gelation solvent, solids content, chain extender/isocyanate ratio, and dispersion mode. The solids content (2-11 wt.%) is the parameter with the most influence on the density of the aerogels, with a clear decrease in this property as the solids content decreases. On the other hand, it was demonstrated that minimizing the excess of ethylenediamine (used as chain extender) in relation to the isocyanate is a valuable consideration to improve the thermal conductivity of the aerogel. Related to the chain extender/isocyanate ratio, a compromise situation where the initial isocyanate reacts almost completely is crucial. Fourier-transform infrared spectroscopy was used to conduct such monitoring during the reaction. Once the conditions were optimised, the aerogel showing improved properties was synthesised using ethyl acetate as the gelling solvent, a 3.7 wt.% solids content, an ethylenediamine/isocyanate ratio of 0.20, and sonication as the dispersion mode, attaining a thermal conductivity of 0.030 W m-1 K-1 and a density of 0.046 g cm-3. Therefore, the synthesized aerogel emerges as a promising candidate for use in the construction and automotive industries.

Environmental and economic analysis of bioethanol production from sugarcane molasses and agave juice.

In this article, sugarcane molasses and agave juice were compared as potential feedstocks for producing bioethanol in Mexico in terms of their environmental impact and economic factors. Life cycle assessment (LCA) using SimaPro was carried out to calculate environmental impacts by using a cradle-to-gate approach. A preliminary economic analysis was performed to determine the economic feasibility of the studied options. Also, capital goods costs were obtained using the Aspen Plus economy package. Moreover, a sensitivity analysis was involved to compare the environmental and economic viability of producing bioethanol from sugarcane molasses and agave juice. LCA results revealed that cultivation and fermentation were the most harmful stages when producing bioethanol from sugarcane molasses and agave juice, respectively. Furthermore, when it was derived from agave juice rather than sugarcane molasses, it had more environmental benefits. This was ascribed to the lower consumption rate of fertilizers, pesticides, and emissions given off from the former. Regarding financial aspects, the preliminary analysis showed that producing bioethanol was not economically viable when grid energy alone was used. However, if power from the grid is partially replaced with renewable energy, producing bioethanol becomes economically feasible, and sugarcane molasses is the most suitable feedstock.

Long-Term Performance of Nanomodified Coated Concrete Structures under Hostile Marine Climate Conditions.

Epoxy resin coatings are commonly used to protect concrete structures due to their excellent chemical corrosion resistance and strong adhesion capacity. However, these coatings are susceptible to damage by surface abrasion and long-term contact with marine climate conditions, deteriorating their appearance and performance. This study aims to optimize the performance of cement-based epoxy resin coatings, bisphenol-A and polyol, in aggressive environments by functionalizing the selected systems with different nanoparticles such as activated carbon, surface modified nanoclay, silica and zinc oxide. Nanomodified coatings were applied to concrete specimens and subjected to three weeks in a spray salt chamber and three weeks in a QUV chamber. They were found to present improved thermal resistance and curing degree after the weathering test. Their water permeability, adhesion, and abrasion resistance properties were evaluated before and after this test. The results showed that the nature of the nanocomposites determined their water permeability; the bare resin presented the worst result. Additionally, nanomodified composites with activated carbon and silica showed the best adherence and abrasion resistance properties, due to the effect of this aging test on their thermal stability and curing degree.

Olive pomace versus natural gas for methanol production: a life cycle assessment.

Increasing demand for methanol production and global competition for the use of natural resources are key issues in finding new and environmentally routes for methanol production. In this work, life cycle assessment was performed using the software SimaPro v9 to analyze the environmental impact of methanol production process from olive pomace and compare with natural gas route. The main stages considered in the methanol production from olive pomace were olive production, olive oil extraction, and methanol production. In addition, the methanol production in turn can be divided in three main processes: olive pomace gasification, syngas purification, and methanol production which were also evaluated individually. Finally, the global environmental impacts associated with the methanol production from olive pomace were compared with a conventional methanol production from natural gas. This assessment determined that the production of methanol from the olive pomace had a greater environmental impact for all the categories studied except the one related to the shortage of fossil fuels. These results were directly related to the technical performance of the processes.

Fast pyrolysis as an alternative to the valorization of olive mill wastes.

BACKGROUND: The valorization of organic wastes through fast pyrolysis appears to be a highly promising option for decreasing pollutants and reducing consumption of natural resources. For this purpose, three different olive pomace samples were studied to determine how olive crop location and the extraction process could influence bio-oil product distribution. Olive pomace was selected as the feedstock due to the importance of the olive oil industry in Spain. RESULTS: In this study, the conditions of fast pyrolysis were optimized using lignin as a reference, with the optimum conditions being 500 °C, 20 °C ms-1 as the heating rate and 15 s as the vapour residence time. The olive pomace results determined that not only their chemical composition, but also their fat content had a remarkable effect on product distribution obtained after fast pyrolysis. However, whereas high lignin content enhanced phenol production, cellulose decomposed to carboxylic acids. In addition, due to current global warming, the carbon dioxide (CO2 ) burden of the three samples was calculated using mass spectroscopy. The OPGC sample gave off the lowest amount of greenhouse gases, followed by OPMNE and OPMN. CONCLUSIONS: The higher fat content in the sample enhanced carboxylic acid production. The difference in phenol production between OPMN and OPMNE could be attributed to the presence of potassium. From an environmental point of view, the use of olive pomace wastes could reduce CO2 emissions with further research and by developing experimental processes. © 2020 Society of Chemical Industry.

Utilization and reusability of hydroxyethyl cellulose alumina based aerogels for the removal of spilled oil.

Nowadays millions of oil tons are spilled into the environment causing important damage. Therefore, the development of new technologies and materials are needed to remediate this problem. In this study, hydroxyethyl cellulose alumina-based aerogels are synthesized by an environmentally friendly freeze-drying process to be used as sorbents for oil spills. It is demonstrated that the oil retention coefficient depends on the viscosity of the oil and the amount of hydroxyethyl cellulose contained in the aerogel, being 10% the optimal proportion. The aerogel synthetized with this content of hydroxyethyl cellulose displays the most favourable physicochemical and morphological properties to retain different oil spills, achieving 5.5 times its weight in comparison to its dry state. In addition, reusability experiments washing the aerogel with acetone or ethanol after the oil retention are carried out. Results show an improvement after a long washing of the sorbent with acetone, resulting in an oil weight gain of 38.7%.

Immobilized laccase on polyimide aerogels for removal of carbamazepine.

Since it is known that conventional wastewater treatment plants cannot completely remove pharmaceutical compounds, such as carbamazepine, the need for their removal has intensified. The use of biocatalysts, such as enzyme is an environmentally friendly method for carbamazepine biodegradation. Nevertheless, enzyme immobilization is required to facilitate the recovery and reusability and avoid the loss of enzyme. In this work, laccase was immobilized on modified polyimide aerogels by means of covalent bonding. Results showed that the immobilized laccase on polyimide aerogels possesses significantly improved activity under acidic or basic pH range in comparison with the free enzyme. Furthermore, for all the temperature range the activity of the immobilized enzyme was higher compared to the free enzyme form. The storage stability improved by the immobilization on this support material. The reusability tests towards oxidation of 2, 2'-azino-bis (3-ethylbenzothiazoline-6-sulphonicacid) (ABTS) showed that the immobilized laccase maintained 22% of the initial activity after 7 cycles. Immobilized laccase on polyimide aerogels for carbamazepine (CBZ) degradation exhibited 76% and 74% removal in spiked water and secondary effluent, respectively. Furthermore, after 7 cycles the CBZ removal efficiency remained higher (50% and 65% for spiked water and secondary effluent, respectively).

Stabilizer effects on the synthesis of gold-containing microparticles. Application to the liquid phase oxidation of glycerol.

Gold-containing poly(urea-formaldehyde) microparticles were prepared by the in situ polymerization method using a series of stabilization agents with different chemical nature. The effects of cetyltrimethylammonium bromide (CTAB), sodium dodecyl sulfate (SDS), polyvinyl pyrrolidone (PVP), polyvinyl alcohol (PVA) and tetrakis(hydroxymethyl)phosphonium chloride (THPC) on the morphology, the particle size of encapsulated gold, the gold particle size distribution and the encapsulation efficiency were investigated by using scanning electron microscopy, X-ray diffraction and atomic absorption analyses. The chemical nature of stabilizer had a marked influence on both the encapsulated gold particle size and the encapsulation efficiency. Both gold particle size and gold encapsulation efficiency increased when decreasing the stabilizer polarity number. All the microparticles here prepared were tested in the liquid phase selective oxidation of glycerol. The glycerol conversion increased and the glyceric acid selectivity decreased when decreasing gold particle sizes. Results showed that use of stabilizers with hydrophobic surfaces enhanced the selectivity to C3 products in the resulting catalysts. On the other hand, the use of stabilizers with hydrophilic surfaces increased the C-C bond cleavage products in the resulting catalysts.

Scale-up of a suspension-like polymerization process for the microencapsulation of phase change materials.

Microcapsules of polystyrene with a high level of encapsulated paraffin wax and a narrow size distribution were prepared by a suspension-like polymerization process. The scale-up of this microencapsulation process was carried out by designing a pilot plant that was geometrically proportional to that used on the laboratory scale with the aim of preparing microcapsules with a similar particle size and with the same phase change material (PCM) content as those obtained in the laboratory. In order to verify the effectiveness of the scale-up procedure, a number of experiments on the pilot plant were carried out using the optimal formulation found on the laboratory scale. Only slight differences in mean particle size and encapsulated paraffin content were observed between the two scales at higher stirring rates. The experimental values were fitted to the theoretical expression for the average dissipation rate as a function of the mean particle size. This showed that the classical nonintermittent Kolmogoroff theory is applicable on the laboratory scale, whereas in the pilot plant a large intermittence took place, thus limiting the scale-up to higher stirring rates at which an equal average dissipation rate in both scales led to the same mean particle size. The final results indicated that the assumptions made during the scale-up process were correct.