Research Outputs
Stable Reusability of Nanocellulose Aerogels with Amino Group Modification in Adsorption/Desorption Cycles for CO2 Capture
This study evaluated the stability and reusability of amino-functionalized nanocellulose aerogels as CO2-adsorbent materials. The modified aerogels, synthesized via a controlled silylation using N-[3-(trimethoxysilyl) propyl] ethylenediamine (DAMO), demonstrated excellent thermal stability up to 250 °C (TGA) and efficient CO2 adsorption through chemisorption, which was the main adsorption mechanism. The performance of the aerogels was assessed using both adsorption isotherms and the decay pressure technique, revealing that CO2 adsorption capacity increased with higher amino group loading (4.62, 9.24, and 13.87 mmol of DAMO). At 298 K and 4 bar, CO2 adsorption capacity increased proportionally with the amino group concentration, reaching values of 3.17, 5.98, and 7.86 mmol of CO2 g−1 polymer, respectively. Furthermore, over 20 adsorption/desorption cycles, the aerogels maintained 95% CO2 desorption at ambient temperature, indicating their potential for industrial use. These findings highlight the aerogels suitability as stable, reusable materials for large scale CO2 capture and storage technologies.
Small-medium scale polygeneration systems: Methanol and power production
The feasibility and attractiveness of the integrated production of chemicals and electrical power is dependent upon on the nature of the products and their demands. This study focuses on the small-to-medium scale combined production of methanol (200,000 tonnes/year) and electrical power (200 MW). The integrated system considers both recycle (recycle ratio = 5) and once-through (no recycle) modes of methanol synthesis. The results of simulations show that, when compared to separate stand-alone plants for methanol and power production, the integrated systems show lower consumption of total fresh synthesis gas for recycle and once-through operation of 2.8% and 3.7%, respectively. In addition, simulations show that the advantage over stand-alone plants increases further in the face of decreasing catalyst activity or selectivity, rising to over 10% in several scenarios. This is because the off-spec material from methanol production in an integrated plant can be diverted to the power generation section of the plant. These savings in operating costs are over and above the substantial capital cost savings which can be realized in the design of a once-through integrated plant.
Performance of small-medium scale polygeneration systems for dimethyl ether and power production
Polygeneration systems have been shown to be a flexible arrangement which can meet seasonal product demands for electric power, fuels and chemicals. This is especially relevant for small markets such as isolated small-medium size communities demanding electricity, and fuels. This work is focused on the feasibility of a polygeneration system based on a single-step DME plant to produce 200,000 tonnes/year of DME and 200 MW of electricity. An economic analysis is carried out to assess different configurations and feedstocks for syngas production. The DME-production was simulated at different possible recycle ratios and under the condition of potentially reduced catalyst performance. In all cases, the once-through polygeneration system showed significant improvement over all other configurations e up to 11.6% reduction in the amount of synthesis gas required to produce DME and power e with a corresponding reduction in “wasted” feed leaving as effluent CO2. The flexibility of an integrated system meant that, in cases of decreased catalyst activity or selectivity, the advantages of the integrated system over standalone configurations are even greater e up to 18.6%. Moreover, polygeneration systems show further economic advantages depending upon the selling price of electricity for both fossil fuel and biomass sources of the syngas feedstock.
Hydrodynamic effects of use of eductors (Jet-Mixing Eductor) for water inlet on circular tank fish culture
Trials were conducted in circular tanks used in aquaculture (1.2 m diameter and 0.4 of useful depth) in order to evaluate the effect of different water injection devices on the tangential velocity of the water, its uniformity pattern, the mixing time and the removal of solids through the bottom drain. Two injection devices, without fishes, were evaluated at the tank: a Vertical Spray, considered as standard in aquaculture and an eductor (Jet-Mixing Eductor) which is used in chemical and petrochemical industry to homogenize and keep in movement great volumes of water. The devices were evaluated under the same operating conditions: inlet flow of 4, 6 and 8 l/min and water injection angle of 0° and 45°. In each trial, the water velocity inside the tank was measured, also the mixing time and the time in which the 100% of pellets of fish food were eliminated from the tank through the bottom drain. The results indicate that, for all inlet flows, the eductor operating at 45° presents significantly (p < 0.001) better result in terms of hydraulic variables such as tangential velocity, uniformity, mixing time and solids removal time from the tank (self-cleaning effect). In the case of eductors, although an increase of inlet flow produces improvements of hydraulic variables, a change of water injection angle, from 0° to 45°, produces significantly better results (p < 0.001). Differences of hydraulic performance between the eductor and Vertical Spray are mainly owing to the multiplicative effect of the outlet flow that is generated by the eductor. This means that, for similar values of impulse force and water velocity at the exit of the nozzle injection (V2), the eductors generate significantly higher tangential velocity and uniformity, lower mixing times and secondary flow patterns, which ensure the self-cleaning of solid waste. In terms of power consumption, eductors overcome Vertical Spray in the trial performed. However, when comparing them under equal requirements of hydraulic performances (velocity, mix and/or self-cleaning), eductors present the same or lower energy consumption. Comparatively eductors would generate, under similar operating conditions, clear benefits for produced species in aquaculture, by generating hydraulic conditions that ensure a better quality of water and patterns and uniformity of velocity, which are more suitable for their health and normal growth.
Effect of nanostructured ceria as support for the iron catalysed hydrogenation of CO2 into hydrocarbons
This paper demonstrates the key role of the property–structure relationship of the support on iron/ceria catalysts on the hydrocarbon selectivity and olefin-to-paraffin ratio for the direct hydrogenation of carbon dioxide into hydrocarbons. The effect is directly related to the reducibility of the different nanostructured ceria supports and their interaction with the iron particles. Herein, we demonstrate that the iron-based catalysts can be modified not only by the addition of promoters, commonly reported in the literature, but also by careful control of the morphology of the ceria support.
Shape-selectivity effects in syngas-to-dimethyl ether conversion over Cu/ZnO/Al2O3 and zeolite mixtures: Carbon deposition and by-product formation
The conversion of syngas into dimethyl ether has been studied over physical mixtures of a Cu/ZnO based catalyst and a zeolite. Theta-1, ZSM-23, ferrierite, ZSM-5 and mordenite were used. The zeolites were separated after reaction and characterised by temperature programmed oxidation, XRD, and GC–MS of the entrained hydrocarbons. Theta-1 and ferrierite were found to have the most stable performance and the highest selectivity to DME. Deactivation is shown to be faster for structures with enough space to accommodate bulky carbonaceous deposits such as mordenite and ZSM-5. Longer diffusion paths associated with larger crystallites also contributed to rapid loss of activity for ZSM-23. The zeolite topology was found to influence the nature of the entrained alkylbenzenes.