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- Biodiesel production from residual cooking oils and its purification by adsorption processes based on adsorbents of natural originPublication . Garção, Maria Isabella Lima; Gomes, Maria Carolina Sérgi; Queiroz, Ana; Ribeiro, António E.; Brito, PauloTotal global energy consumption has increased significantly in recent decades, and nowadays the main sources of world energy are oil, coal and natural gas. In addition to environmental concerns, the limited availability of fossil fuels has increased the interest in exploring alternative energy sources. In this quest, biofuel is a promising renewable energy source with low carbon emissions, also, it can be produced from a variety of resources, including waste cooking oil (WCO). Biodiesel is renewable, biodegradable, non-toxic, sulfur-free and free of aromatic carcinogens
- Separation of nadolol racemates by high pH reversed-phase simulated moving bed chromatographyPublication . Arafah, Rami; Ribeiro, António E.; Rodrigues, Alírio; Pais, Luís S.Nadolol is a pharmaceutical drug marketed as a mixture of four stereoisomers, used to treat cardiovascular diseases. This drug is a mixture of two pairs of racemates, therefore, its complete separation represents a challenging task. Recently, our research group reported the pseudo-binary separation of nadolol by SMB chromatography using both coated Chiralpak AD and Chiralpak IA immobilized chiral stationary phases. In this work, we present an alternative strategy, implementing a first achiral separation step, by using C18 columns to perform the separation of the two pairs of nadolol racemates under reversed-phase mode. Extensive experimental and simulation results will be presented including solvent screening, measurement of equilibrium and kinetic data, and both fixed-bed and SMB preparative separations. Extensive experimental and simulation results will be presented, including solvent screening, measurement of equilibrium adsorption isotherms, breakthrough measurements, and SMB (FlexSMB-LSRE unit) experimental preparative separation using C18 columns.
- Purification of biodiesel using a natural based adsorbent in a packed-bed columnPublication . Smolich, Camilla Groxko; Guimarães, Miriam D.; Fabian, João Vitor; Gomes, Maria Carolina Sérgi; Queiroz, Ana; Brito, Paulo; Ribeiro, António E.In Europe, the Renewable Energy Directiva stimulates the development of renewable energy sources to reduce greenhouse gas emissions by at least 55% by the year 2030 and to become aclimate-neutral continent by 2050 [1]. Biodiesel presents advantages over diesel fuel in terms of sulfur content, biodegradability, flash point, no aromatic content, higher cetane number and miscibility in petroleum diesel in any ratio [2]. The most used feedstock is high quality vegetable oil, but the use of waste cooking oil adds to the global reduction of residue, lower costs, and competes less for vegetable oils against the food industry [3]. This biofuel is obtained through transesterification, and glycerol is formed as a coproduct. lts presence can cause damage to motors so it must be removed until its final concentration is lower than 0.02wt%. The most used method is wet washing, but the downside is the great amount of water used and long periods of time are needed to separate biodiesel from its contaminants through decantation [4]. A promising altemative is dry washing method through adsorption using biomass activated carbon. For a more practica! application, packed columns are frequently used in large scale adsorption processes. lt is one of the most efficient configurations for treating great volumes of effluent and adsorption-desorption cycles [5]. For this study, crude biodiesel was produced through transesterification from a waste cooking oil sample, using ethanol and a basic catalyst (NaOH). Afterwards the biodiesel produced was characterized in terms of glycerol content. In parallel, activated carbon materials were obtained from olive pits by physical activation at 800°C. The adsorbent materials performance for glycerol removal from crude biodiesel is assessed using a continuous system based on a packed-bed column according to the following parameters: fluid rate, removal capacity, pressure drop and adsorbent recovery.
- Production and characterization of different green adsorbents for the removal of free glycerine in the biodiesel purification processPublication . Guimarães, Miriam Domingues; De Prá, Marina Celant; Queiroz, Ana; Ribeiro, António E.; Brito, PauloThere is environmental concern due to the high use of oil as a primary fuel, which results in a significant emission of polluting gases, and one of the most promising solutions involves replacing it with biodiesel. Biodiesel is a fuel that can be produced using waste cooking oil (WCO) and has become an excellent alternative to ordinary diesel. A crucial stage in the production of biodiesel is the purification process. Among the various methods used, there are two main ones: the wet purification method, which uses water, and the dry purification method, which uses ion exchange resins or adsorbents. Dry purification using adsorbents removes contaminants such as water, soap, and traces of glycerine based on their chemical polarities and acidic and basic properties. Also, it avoids the generation of high volumes of effluents, and the adsorbents can be reused [1][2].
- Influence of environmental factors on α-tocopherol levels in Moringa oleifera extractsPublication . Kessler, Júlia C.; Manrique, Yaidelin A.; Martins, Isabel M.; Ribeiro, António E.; Rodrigues, Alírio; Barreiro, Filomena; Dias, Madalena M.Moringa oleifera L. extracts (Mo) have attracted attention as a sustainable and effective alternative to synthetic ingredients for cosmetic formulations. The unique and diverse phytochemical profile of the Mo tree enhances the quality and appeal of commercial products, as evidenced by numerous studies and patents. Supercritical carbon dioxide extraction (SFE-CO2) is particularly advantageous for this purpose, offering enhanced thermostability and selectivity of extracted compounds compared to conventional methods. This review examines the safety and efficacy of Mo seed, leaf, and root extracts as cosmetic ingredients, focusing on their bioavailability and performance by considering the thermodynamics and operational benefits of SFE-CO2. The collected data highlights the method’s efficiency in terms of the total extraction yield and the recovery of target compounds from Mo, providing insights from optimisation studies and linking the solvation power of supercritical CO2 with the significant non-polar and low-polar compounds present in Mo extracts.
- Separation of profens by chiral liquid chromatography: preliminary studiesPublication . Ribeiro, António E.; Pais, Luís S.; Rodrigues, Alírio
- Preparative separation of nadolol racemates using reversed-phase liquid chromatographyPublication . Arafah, Rami; Ribeiro, António E.; Rodrigues, Alírio; Pais, Luís S.Nadolol is a nonselective beta-adrenergic receptor antagonist ( -blocker) pharmaceutical drug, widely used in the treatment of cardiovascular diseases, such as hypertension, ischemic heart disease (angina pectoris), congestive heart failure, and certain arrhythmias. Its chemical structure has three stereogenic centers which allows for eight possible stereoisomers. However, the two hydroxyl substituents on the cyclohexane ring are fixed in the cis-configuration, which precludes four stereoisomers; in fact, two pairs of enantiomers. Nadolol is presently marketed as an equal mixture of the four stereoisomers, designated as the diastereoisomers, There are still few published works concerning the separation of nadolol stereoisomers. Most of these works refer the resolution at analytical scale and few refer the separation at preparative scale using the simulated moving bed (SMB) technology [2-4]. This technology is generally based on the use of chiral adsorbents which must have enough recognition for all the chiral species.
- Biodiesel production from waste cooking oils catalysed by ionic liquid [BMIM][HSO4]Publication . Almeida, Fretson Micaela; Queiroz, Ana; Ribeiro, António E.; Brito, PauloThe environmental and energy problems related to the burning of fuels from fossil resources, i.e. nonrenewable fuels such as oil, natural gas or coal, leading to an increased concern about global warming, have directed the scientific community to seek sustainable and renewable energy alternatives. In this context, biofuels have emerged as a promising way to replace non-renewable fuels, including biodiesel [1]. Biodiesel is defined as a mix of monoalkyl esters of long fatty acid chains (FAMEs), and can be obtained by converting vegetable oils or animal fats through transesterification or esterification reactions. Due to its advantages, such as biodegradability, low viscosity, high flash point and low environmental impacts, it has potential to be used directly in diesel engines without any modification [2]. The raw materials used in biodiesel production can be divided into edible and inedible. However, the high cost of edible oils, which correspond to about 70% of the total value of production, as well as competition with the food market and soil degradation due to large planting scales, are disadvantages for the production and commercialization of biodiesel [3]. Inedible materials such as Waste Cooking Oils (WCOs) can also be used. The reuse of WCOs is a sustainable and environmentally friendly solution, preventing millions of tons of this raw material from being dumped into sanitation systems giving rise to serious problems in wastewater treatment. Still, one of the disadvantages of using WCOs is its high Free Fatty Acid (FFA) content that leads to saponification reactions [2]. Homogeneous alkaline catalysts are the most used in the biodiesel production industry. Compared to homogeneous acid catalysts, they have many advantages, such as high productivity, low price, allow high reaction speed, shorter reaction time, low alcohol molar ratio:oil and lower corrosiveness. However, catalysis is mainly affected by the presence of free fatty acids, leading to decreased reaction yields. In addition, when using these conventional catalysts, a high amount of clean water is used during the purification process, resulting in high flows of waste water, which is deposited in rivers, lakes, seas, contaminating the environment. To solve this problem, the possibility arises of using new catalysts, such as ionic liquids (ILs), which allow high reaction yields, and can be recovered and reused, making them greener and more economical
- Optimization of simulated moving bed processes for multicomponent chiral separationsPublication . Ribeiro, António E.; Rodrigues, Alírio; Pais, Luís S.This work will present and discuss the experimental and simulation results obtained for the analytical and preparative separation of the four stereoisomers of nadolol, an important example of a non-selective beta-adrenergic receptor antagonist (beta-blocker) pharmaceutical drug, widely used in the treatment of cardiovascular system diseases, such as hypertension, ischemic heart disease (angina pectoris), congestive heart failure and certain arrhythmias. The main focus will be placed in the selection of the proper CSP/solvent combination for SMB operation. Experimental results will be presented using Chiralpak AD and Chiralpak IA CSP (Daicel, Europe) and different mixtures of alkanes, alcohols and acetonitrile as solvent.
- Removal of naproxen from water using adsorbents obtained from low-cost materialsPublication . Milani, Eduardo C.; Reis, Vinícius de Assis; Brito, Paulo; Queiroz, Ana; Ribeiro, António E.The continuous growth of world population together with the strong urbanization has triggered an increasing demand for freshwater which has resulted in a serious deterioration of water bodies1. Water pollution with pharmaceutical drugs is becoming a relevant problem. The concentration of nonsteroidal anti-inflammatory drugs, estrogens, personal care products, among others, in waterways is reaching hazardous levels, posing a threat to the environment and human health. Moreover, conventional cleaning and degradation processes applied on wastewater treatment plants are inefficient to eliminate or remove these compounds. Adsorption is a treatment process considered as effective process used to remove micropollutants such as pharmaceutical drugs from wastewaters2,3. This work will present the main experimental results obtained for the removal of naproxen, a representative anti-inflammatory drug, from water by adsorption using activated carbon obtained from olive stone. From the raw material, four different types of activated carbon adsorbent were prepared and characterized. The equilibrium adsorption isotherms were measured using the batch method. The most significant adsorption parameters were optimized, such as the solution pH, mass of the adsorbent, contact time and temperature. The physicochemical characterization of the pyrolyzed material shows a considerable superficial area of 608 m2/g when compared with other natural biomass-based materials. The adsorbent with the better performance allowed, using a contact time of 24 hr and a solution pH of 4.5, a removal efficiency of 100%. The Langmuir model was used to better described the adsorption behavior with the highest maximum adsorption capacity value of 35.2 mg naproxen/g adsorbent. The kinetics of the adsorption is well described by a pseudo-second order model.