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Recently, hydrogen has been explored as an aviation energy carrier to support various critical energy challenges for the upcoming decades. Thus, conventional and non-conventional hydrogen production methods have been developed worldwide. This paper investigates Steam Methane Reforming (SMR) and Alkaline Electrolysis (AWE) hydrogen production as primary processes from an energy requirement and life cycle perspective. Besides, It also considers hydrogen liquefaction for aviation use. In this context, an attributional, Cradle-to-Gate life cycle assessment was carried out to compare the environmental impact of SMR and AWE hydrogen production processes under four German energy mix scenarios. The assessment method selected was ReCiPe 2016, and the main impact categories were climate change and acidification potential. The results show that greenhouse gas emissions from each production method highly depend on energy sources. The CO2 emissions from SMR and AWE processes in a base case scenario are 12 and 51 kgCO2eq/kgH2, respectively, and these values decrease to 7 (SMR) and 22 kgCO2eq./kgH2 (AWE) in a 2050 renewable energy scenario. Concerning the energy requirements, each process requires different energy amounts to produce 1 kgH2 (functional unit). SMR requires 11.3 kWh, AWE 61.8 kWh, and hydrogen liquefaction 5.1 kWh. In brief, hydrogen is widely promoted as an alternative energy carrier in Germany; however, depending on the production process and technical considerations, further studies are required to support and explore its applications. [ABSTRACT FROM AUTHOR]

This study aimed to analyse and compare the effects of dip-coating with cellulose hydrogel coupons of Acrylonitrile Styrene Acrylate (ASA), polyamide (Nylon®), and Tritan® to produce hydrophilic structures for water uptake from fuels. In this process, the polymeric substrates were immersed in a cellulose solution after adding the crosslinking agent (epichlorohydrin). The samples were kept in the solution at 30 ºC for 1 h and then removed at a withdrawn speed of 98 or 410 mm.min-1. The coated and uncoated materials were characterized regarding contact angle, mass of hydrogel adhered and surface morphology. In addition, the roughness of the uncoated substrates was measured. The samples underwent sequential swelling and drying cycles to evaluate water retention and the possibility of reusing the material. Tukey test, at a 95 % confidence level, was used to assess differences in roughness, the mass of adhered hydrogel, contact angle, and swelling degree for each polymeric substrate and condition analysed. The coated coupons exhibited increased hydrophilicity when compared to the uncoated control group, reaching a water contact angle of around 50 º. ASA displayed the greatest incorporation of hydrogel; however, it was mainly retained in the grooves of the material, limiting its ability to interact with water. Meanwhile, the hydrogel film formed on Nylon® coupons achieved a higher degree of swelling (3.5-3.9 g.g-1). Thus, this study demonstrated that the material used in the coating process strongly influenced the characteristics of the hydrogel film formation and its performance regarding water retention. [ABSTRACT FROM AUTHOR]

Acetaldehyde has been historically synthesized from ethanol via oxidation. However, since the 1960s, the cost of feedstock and conversion process has gradually driven manufacturers to prefer the liquid-phase oxidation of ethylene. However, the aggravation of the effects of the climate crisis demands a shift from fossil feedstocks to renewable feedstocks to reduce society’s CO2 footprint. Moreover, sugarcane ethanol production is a more mature process nowadays, delivering a low-cost renewable chemical. Bearing all this in mind, this work analyzes the viability of the production of acetaldehyde via oxidation of sugarcane ethanol. The key idea is to integrate the process into a sugarcane biorefinery to take advantage of the surplus energy of optimized distilleries to provide renewable energy for acetaldehyde production. The oxidation process of ethanol to acetaldehyde in the gas phase was simulated using literature data. Process data for the remaining sections of the sugarcane biorefinery were based on literature data as well. Based on equipment sizing and processing capacity, a cash flow analysis was performed to determine the best operating conditions for acetaldehyde production via ethanol oxidation. Results have shown that the conversion of ethanol to acetaldehyde using this process is competitive and can increase the earnings of the biorefinery. A life cycle assessment was performed as well to compare the carbon intensity of acetaldehyde produced from ethanol to the carbon intensity of acetaldehyde produced via direct oxidation of ethylene, showing a reduction of 85%. Results demonstrate that the oxidation of ethanol represents a renewable alternative with economic potential when integrated into a sugarcane biorefinery. [ABSTRACT FROM AUTHOR]

Biomass consists of biodegradable and non-fossilized organic matter, including a wide range of materials such as forestry, agricultural, municipal, and industrial solid residues. Due to its renewable nature, high carbon content, and availability in several countries, biomass is a promising alternative to fossil fuels. In this context, thermochemical conversion processes such as fast pyrolysis can be an interesting option to produce heat, power, fuels, and chemicals of lower greenhouse gas emissions from biomass sources. Fast pyrolysis uses high temperatures (~500 °C), inert atmospheres (e.g., nitrogen), and short residence times (1 – 5 s) to convert biomasses mostly into bio-oil (liquid stream), also producing char (solid) and gas fractions. Biomass composition highly affects the bio-oil properties and, although much work has been done to understand such an effect focusing on heat and power production, little has been done aiming to design pyrolysis for high-added value chemicals. This work performed the kinetic simulation and multivariate analysis of a fast pyrolysis (FP) plant fed by multiple feedstocks to assess the effect of biomass composition on the bio-oil functional groups and provide guidelines to produce high-added value bio-oil components. The simulation was built in Aspen PlusTM v.10, validated against experimental data, and used to obtain a dataset correlating biomass compositions from 60 sources and FP outputs. The dataset was analyzed via hierarchical cluster analysis (HCA) and principal component analysis (PCA), showing the correlations between biomass and bio-oil properties and highlighting key biomass features to obtain specific high-value functional groups. Among the results, biomasses of higher cellulose and hemicellulose contents such as agricultural feedstocks may produce higher amounts of anhydrosugars, ketones, and aldehydes. In contrast, feedstocks of higher lignin contents such as wood may generate increased concentrations of phenols and aromatics. This work shows how simulation and multivariate analysis tools can be used in the design of fast pyrolysis aiming at multiple bio-oil applications. [ABSTRACT FROM AUTHOR]

Plastic waste generation, a global environmental concern, has more than doubled over the past two decades. Given the rising projections of plastic use and waste by 2060, immediate actions are required to improve waste management and reduce plastic leakage. Plastic-to-fuel technologies such as co-pyrolysis of plastic and biomass residues are interesting options for polymer chemical recycling. Co-pyrolysis happens at high temperatures, low residence times, and inert atmospheres and converts plastics and biomasses into liquid (biooil and wax), solid (char), and gaseous products of high heating value and economic interest. Although some development has been made in understanding the key aspects of biomass-plastic co-pyrolysis, little has been done toward representing such a process via simulation. In this context, this work developed, in Aspen PlusTM, a simulation of the co-pyrolysis of xylan, a hemicellulose type, and high-density polyethylene (PE). The simulation aimed at representing the main co-pyrolysis phenomena using a hybrid equilibrium-kinetic approach and properly predicting pyrolysis yields. The simulation was run at different temperatures (500–700 °C) and PE blending proportions (10–90 wt%) and the results were compared to experimental data. The results have shown that increasing pyrolysis temperatures produced higher bio-oil and gas yields as a result of higher degradation of the feedstock structure, while higher PE blending proportions had the opposite effect. As for the char yields, PE contents up to 70 wt% decreased the char yields, while higher PE levels resulted in an opposing trend. This work shows that combining polymer decomposition equilibrium and biomass fast pyrolysis kinetics reasonably predicts product yields and can be used for the design of co-pyrolysis processes and waste management chains [ABSTRACT FROM AUTHOR]