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A brief review of the supercritical antisolvent (SAS) technique for the preparation of nanocatalysts to be used in biodiesel production

Publication . Santos, Samuel; Puna, Jaime; Gomes, João F. P.

In an era where sustainability is becoming the main driving force for research and development, supercritical fluids-based techniques are presented as a very efficient alternative technology to conventional extraction, purification, and recrystallization processes. Supercritical antisolvent (SAS) precipitation is a novel technique that can replace liquid antisolvent precipitation techniques. Additionally, through the optimization of precipitation operating conditions, morphology, particle size, and particle size distribution of nanoparticles can be controlled. As an antisolvent, supercritical carbon dioxide (scCO2) is far more sustainable than its conventional liquid counterparts; not only does it have a critical point (304 K and 73.8 bar) on its phase diagram that allows for the precipitation processes to be developed so close to room temperature, but also its recovery and, consequently, the precipitated solute purification stage is considerably simpler. This technique can be used efficiently for preparing nanocatalysts to be used in biodiesel production processes.

2022-12-10Journal article

Open access

Clean forest—project concept and early results

Publication . Gomes, João; Puna, Jaime; Marques, António; Gominho, Jorge; Lourenço, Ana; Galhano dos Santos, Rui; Ozkan, Sila

The Clean Forest project aims to valorize forest biomass wastes (and then prevent their occurrence as a fuel source in forests), converting it to bioenergy, such as the production of 2nd generation synthetic biofuels, like bio-methanol, bio-DME, and biogas, depending on the process operating conditions. Valorization of potential forest waste biomass thus enhances the reduction of the probability of occurrence of forest fires and, therefore, presents a major value for local rural communities. The proposed process is easy to implement, and energetically, it shows significantly reduced costs than the conventional process of gasification. Additionally, the input of energy necessary to promote electrolysis can be achieved with solar energy, using photovoltaic panels. This paper refers to the actual progress of the project, as well as the further steps which consist of a set of measures aimed at the minimization of the occurrence of forest fires by the valorization of forest wastes into energy sources.

2022-12-07Journal article

Open access

Clean forest – project concept and preliminary results

Publication . Gomes, João; Puna, Jaime; Marques, António; Gominho, Jorge; Lourenço, Ana; Santos, Rui Galhano dos; Ozkan, Sila

2022Book part

Open access

Liquified biomass utilization in water co-electrolysis for Synthesis gas production

Publication . Martins, Diogo Miguel Mouta Rodrigues; Puna, Jaime Filipe Borges; Santos, Rui Galhano Dos

Nas últimas décadas, o aumento das necessidades energéticas mundiais resultou num consumo crescente de fontes de energia não renováveis e, consequentemente, em graves impactes ambientais. Por esta razão, existe uma aposta cada vez maior no desenvolvimento de fontes alternativas de energia sustentáveis (biomassa, energia solar e eólica, entre outras). Desenvolvida no âmbito de um projeto de I&DT pela start-up GSYF, Lda, esta unidade piloto de 1 kW visa a recuperação de biomassa previamente liquefeita de resíduos florestais lignocelulósicos, para uso como fonte de carbono em co-eletrólise para produção de gás de síntese (H2, O2,CO , e CO2), também conhecido como syngas. Por sua vez, este será transformado noutros produtos de valor acrescentado, como o metano, o metanol ou o biodiesel. Esta investigação centra-se no desenvolvimento desta unidade através de testes de otimização para determinar as condições ideais para a produção de syngas, destinado a ser utilizado como matéria-prima para a produção de metano. O trabalho experimental dividiu-se em duas partes principais, sendo a primeira um conjunto de ensaios sem adição de biomassa e com uma gama mais alargada de condições (3, 4 e 5 bar relativos, e 90, 100 e 110 ºC usando eletrólito 1M NaOH ou KOH) que serviram de base para o segundo conjunto de ensaios onde foram testadas duas amostras de biomassa liquefeita (designadas por Acácia e Energreen). O gás de síntese produzido deve ter um baixo teor de O2, um rácio CO2:H2 próximo do rácio 1:4 encontrado na reação de Sabatier e uma boa relação entre a energia gasta e a quantidade de gás produzido. Na primeira parte, pressões e temperaturas mais elevadas favoreceram o processo. Além disso, dos dois eletrólitos testados, a solução de NaOH provou ser a melhor escolha devido ao menor gasto de energia e por ser mais fácil de trabalhar. Com estes resultados, foi escolhida uma gama de condições mais restrita (4 e 5 bar relativos, e 100 e 110 ºC utilizando apenas o eletrólito NaOH 1M) para ser utilizada em testes futuros. Na segunda parte, as adições de biomassa liquefeita aumentaram a produção de CO2, o que, consequentemente, também reduziu as concentrações de O2. A Acacia é melhor na redução do teor de O2, enquanto a Energreen tem um consumo de energia mais baixo. Ao considerar os pontos fortes de cada biomassa, ambas apresentaram os melhores resultados a 4 bar de pressão a 110 ºC com 2,5 % de biomassa.

2023Master thesis

Open access

Unlocking nature’s potential: modelling Acacia melanoxylon as a renewable resource for bio-oil production through thermochemical liquefaction

Publication . Ozkan, Sila; Sousa, Henrique; Gonçalves, Diogo; Puna, Jaime; Carvalho, Ana; Bordado, João; Santos, Rui Galhano dos; Gomes, João

This study is focused on the modelling of the production of bio-oil by thermochemical liquefaction. Species Acacia melanoxylon was used as the source of biomass, the standard chemical 2-Ethylhexanol (2-EHEX) was used as solvent, p-Toluenesulfonic acid (pTSA) was used as the catalyst, and acetone was used for the washing process. This procedure consisted of a moderate acid-catalysed liquefaction process and was applied at 3 different temperatures to determine the proper model: 100, 135, and 170 ◦C, and at 30-, 115-, and 200-min periods with 0.5%, 5.25%, and 10% (m/m) catalyst concentrations of overall mass. Optimized results showed a bio-oil yield of 83.29% and an HHV of 34.31 MJ/kg. A central composite face-centred (CCF) design was applied to the liquefaction reaction optimization. Reaction time, reaction temperature, as well as catalyst concentration, were chosen as independent variables. The resulting model exhibited very good results, with a highly adjusted R-squared (1.000). The liquefied products and biochar samples were characterized by Fourier transformed infrared (FTIR) and thermogravimetric analysis (TGA); scanning electron microscopy (SEM) was also performed. The results show that invasive species such as acacia may have very good potential to generate biofuels and utilize lignocellulosic biomass in different ways. Additionally, using acacia as feedstock for bio-oil liquefaction will allow the valorisation of woody biomass and prevent forest fires as well. Besides, this process may provide a chance to control the invasive species in the forests, reduce the effect of forest fires, and produce bio-oil as a renewable energy.

2024-09-30Journal article

Open access