434 research outputs found
Reactions and Separations in Green Solvents
No full textMost chemical processes involve solvents in the reaction and the separation step. These solvents give rise to a heavy environmental and economical burden. Moreover, these solvents are based on non-sustainable resources like petroleum. The aim of this thesis has been to develop a number of alternative processes based upon green (sustainable) solvents, and to demonstrate that these processes can be economically and ecologically advantageous. The green solvents investigated were water (polar, protic), supercritical carbon dioxide (apolar, aprotic) and ionic liquids. Water was used for the recovery of soda and molybdate by eutectic freeze crystallization from an industrial waste stream, leading to a zero waste discharge process. Supercritical carbon dioxide was shown to be an excellent solvent for the extraction of natural products like cannabis, for the foaming of polystyrene and for the dyeing of cotton. In a number of reactions ionic liquids were good replacements for traditional solvents. The first generation ionic liquids are based upon petroleum chemicals. In this thesis ionic liquids based upon natural products were synthesized and successfully applied. Based upon these results it can be concluded that the replacement of oil based solvents by green solvents is only a question of time.Process and EnergyMechanical, Maritime and Materials Engineerin
Sustainable Production of Cannabinoids with Supercritical Carbon Dioxide Technologies
No full textThis thesis concerns the production of natural compounds from plant material for pharmaceutical and food applications. It describes the production (extraction and isolation) of cannabinoids, the active components present in cannabis. Many cannabinoids have medicinal properties but not all cannabinoids are available in the (large) quantities necessary to develop new medicines, because so far, for large scale production, there are no economically and technically viable methods to extract those cannabinoids present in low quantities in the plant. Moreover, the currently used production process for the most important cannabinoid, tetrahydrocannabinol (?9-THC), has many drawbacks, such as the large use of the organic solvents, which is not only a burden to the environment but also to the safety of the operators, the production costs as well as the treatment of the produced waste. In this thesis, an alternative process using supercritical carbon dioxide is presented for the production of cannabinoids, including ?9-THC, cannabinol (CBN), cannabigerol (CBG) and cannabidiol (CBD). One of the steps of ?9-THC production from cannabis plant material, is the decarboxylation reaction, transforming the ?9-THC-acid naturally present in the plant into the psychoactive ?9-THC. Experiments showed a pseudo first order reaction, with an activation barrier of 85 kJ.mol-1 and a pre-exponential factor of 3.7x108 s-1. Using molecular modeling, two options for an acid catalysed ?-keto acid type mechanism were identified. Each of these mechanisms might play a role, depending on the actual process conditions. Formic acid was shown to be a good model for a catalyst of such a reaction. A direct keto-enol mechanism catalyzed by formic acid seems to be the best explanation for the observed activation barrier and the pre-exponential factor of the decarboxylation of ?9-THC-acid. Evidence for this was found by performing an extraction experiment with Cannabis Flos. It revealed the presence of short chain carboxylic acids supporting this hypothesis. Then, in order to develop the supercritical fluid extraction process, the solubility of ?9-THC, CBN, CBG and CBD in supercritical carbon dioxide has been determined using an analytical method with a quasi-flow apparatus. First the solubility of ?9-THC has been determined at 315, 327, 334 and 345 K and in the pressure range from 13.2 to 25.1 MPa. The molar solubility for ?9-THC ranged from 0.20 to 2.95x10-4. Then, the solubility of CBN, CBG and CBD in supercritical carbon dioxide has been determined at 314, 327 and 334 K and in the pressure range from 11.3 to 20.6 MPa. The molar solubility of CBN, CBG and CBD ranged from 1.26 x 10-4 to 4.16 x 10-4, from 1.17 to 1.91 x 10-4 and from 0.88 to 2.69 x 10-4, respectively. These solubility data have been compared to each other. The solubility of the different cannabinoids in supercritical CO2 increases at 326 K in the following order: ?9-THC < CBG < CBD < CBN. The solubility data were correlated using the Peng-Robinson equation of state in combination with Van der Waals mixing rules. To continue, supercritical fluid extraction (SFE) using carbon dioxide was performed with Cannabis Sativa L. in a pilot scale set-up at 313 and 323 K in the pressure range from 18 to 23 MPa. The SFE yield of ?9-THC is at maximum 98 %, which is comparable to classical hexane extraction. CBN and CBG can be extracted in higher amounts with SFE than with hexane extraction. Waxes are co-extracted with the cannabinoids. They can be easily removed via a winterization step. The purity of the final extract after winterization was 85 % ?9-THC at the optimal experimental conditions found in these experiments. With a two-steps extraction, it is possible to selectively extract minor cannabinoids (i.e. CBN, CBD and CBG) in a first step at low pressure (~15 MPa), and ?9-THC in a second step at higher pressure (~20 MPa). The last step of the process is performed using Centrifugal Partition Chromatography. It uses a two-phase liquid system, instead of a solid stationary phase, as it is the case in High Pressure Liquid Chromatography (HPLC). Separation is realized by the partitioning of compounds between the two phases. With this technique, a successful separation of ?9- THC, CBN and CBG is presented using the two-phase system hexane / acetone / acetonitrile. A purity higher than 99% is achieved with ?9- THC. With CBN and CBG the best purity obtained is higher than 90%. To conclude, an economical and ecological evaluation of two production routes to obtain pure ?9-THC is presented: the current process using organic solvents is compared with the alternative process using supercritical carbon dioxide developed in this thesis. The alternative process is significantly cheaper than the current one, although the high price of the starting material cannabis dominates the ultimate cost price. From an ecological point of view, the alternative process is also more sustainable as it consumes less energy and generates less waste. Therefore, this alternative process is preferred from an economical and ecological point of view.Process and EnergyMechanical, Maritime and Materials Engineerin
Plasma anandamide and other N-acylethanolamines are correlated with their corresponding free fatty acid levels under both fasting and non-fasting conditions in women
No full textN-acylethanolamines (NAEs), such as anandamide (AEA), are a group of endogenous lipids derived from a fatty acid linked to ethanolamine and have a wide range of biological activities, including regulation of metabolism and food intake. We hypothesized that i) NAE plasma levels are associated with levels of total free fatty acids (FFAs) and their precursor fatty acid in fasting and non-fasting conditions and ii) moderate alcohol consumption alters non-fasting NAE levels. In a fasting and non-fasting study we sampled blood for measurements of specific NAEs and FFAs. In the fasting study blood was drawn after an overnight fast in 22 postmenopausal women. In the non-fasting study blood was sampled before and frequently after a standardized lunch with beer or alcohol-free beer in 19 premenopausal women. Fasting AEA levels correlated with total FFAs (r = 0.84; p <0.001) and arachidonic acid levels (r = 0.42; p <0.05). Similar results were observed for other NAEs with both total FFAs and their corresponding fatty acid precursors. In addition, AEA (r = 0.66; p <0.01) and OEA levels (r = 0.49;
Cold, no sweat: Eutectic freezing beats evaporation hands down
No full textResearchers at the Laboratory for Process Equipment at Delft University of Technology have developed an energy-friendly method to separate saline solutions into clean water and pure salt crystals. The method works by crystallizing the water and salt simultaneously though independently from each other. One of the many useful applications of what is known as eutectic freeze crystallisation is the extraction of valuable salts from waste water from the potato processing industry. The technique can also be used to separate industrial process flows into water and salts thus helping to reduce environmental damage and freeing the way for process flows that currently produce large quantities of saline waste to be treated in an ecologically and economically viable way. Efforts are now focused on scaling up the technology which has meanwhile been patented
Scaling-Up Eutectic Freeze Crystallization
No full textA novel crystallization technology, Eutectic Freeze Crystallization (EFC) has been investigated and further developed in this thesis work. EFC operates around the eutectic temperature and composition of aqueous solutions and can be used for recovery of (valuable) dissolved salts (and/or or acids) and water from a wide variety of aqueous process streams. Using EFC, processes producing large quantities of saline solutions could be carried out in an ecologically and economically attractive way. An introduction and a brief summary of earlier work are given in Chapter 1. The experimental study on pilot scale Cooled Disc Column Crystallizer (CDCC-2) designed for continuous EFC operation is presented in Chapter 2. CDCC-2 was tested for an industrial MgSO4 stream and evaluated in terms of heat transfer, ice and salt sizes, production and growth rates. Application of conductivity and refractive index measurement techniques for inline concentration and supersaturation measurements of MgSO4 solution was studied in Chapter 3. Chapter 4 presents the CDCC-3 and Skid Mounted Unit, designed and constructed for 130 ton/year MgSO4.7H2O and water production capacities. MgSO4 salt crystal structure at eutectic conditions was studied and reported in Chapter 5. The MgSO4 crystal hydrate formed below approximately 0 oC was proven to be MgSO4.11H2O instead of the common reported MgSO4.12H2O. Crystal structure analysis and the molecular arrangement of these crystals were determined using single crystal X-ray diffraction. Raman spectroscopy was used for characterizing MgSO4.11H2O and for comparing the vibrational spectra with MgSO4.7H2O. Thermo gravimetric analysis confirmed the stochiometry of MgSO4.11H2O. Additionally the Miller indices of the major faces of MgSO4.11H2O crystals were defined. Chapter 6 covers the discovery of the natural occurrence of the MgSO4.11H2O new mineral -Meridianiite- as salt inclusions in sea ice from Saroma Lake-Japan and in Antarctic ice. In Chapter 7 nucleation and crystal growth of MgSO4 aqueous solution on a cooled surface were studied theoretically and experimentally. Coupled heat and mass flux equations from non-equilibrium thermodynamics (Onsager theory with reciprocal relations) were defined for crystal growth and the temperature jump at the interface of the growing crystal. Chapter 8 aims to describe the Cyclic Innovation Model (CIM) and to set a path for commercialization of the EFC technology.Mechanical Maritime and Materials Engineerin
Development of scraped eutectic crystallizers
No full textMechanical Maritime and Materials Engineerin
Mixed Solvent Reactive Recrystallization of Sodium Carbonate
No full textInvestigation of the reactive recrystallization of trona (sodium sesquicarbonate) and sodium bicarbonate to sodium carbonate (soda) in a mixed solvent led to the design of several alternative, less energy consumptive, economically very attractive process routes for the production of soda from all principal sodium carbonate sources. The kinetics of the recrystallization as well as of the superimposed chemical reaction, the decomposition of the bicarbonate ion, have been measured, a thermodynamic model for the prediction of the transition temperatures for hydrate recrystallization is presented and the different occurring recrystallization mechanisms are explained in detail. In addition, several inline purification processes for the recycle of the mixed solvent have been investigated: electrodialysis, ion exchange and reactive extraction. The formed soda of mixed solvent reactive recrystallization was also found to possess higher chemical purity, higher mechanical stability and lower bulk density than commercially available soda (dense soda ash).Design, Engineering and Productio
Development of Supported Liquid Membrane Extraction Processes for Slurry Treatment
No full textMechanical Maritime and Materials Engineerin
Removal and Recovery of Phosphonate Antiscalants
No full textIn reverse osmosis (RO) desalination processes, the use of phosphonates prevents scaling, thus allowing for a higher product water recovery, which increases the efficiency of the process. However, a major concern associated with their use in RO desalination is the high cost and environmental impacts associated with the discharge of the waste brine or membrane concentrate containing phosphonates. Therefore, technologies are needed that can remove and recover phosphonate antiscalants from membrane concentrates. Chapters 2 to 5 of this thesis describe a process for the removal and recovery of phosphonate antiscalants by using adsorption technology. In Chapter 2 the phosphonate adsorption capacities of two commercially available anion exchange resins and activated carbon were compared to that of the cheap waste material iron-coated waste filtration sand (WFS). The results presented showed that, in contrast to the exchange resins, the equilibrium adsorption of nitrilotris(methylene phosphonic acid) (NTMP) on WFS is not suppressed at increasing ionic strength and is much less affected by the competitive anions carbonate and sulfate. The strong affinity of phosphonate with the iron oxy-hydroxide in the coating resulted in a relatively high adsorption capacity for NTMP of this waste material. Iron oxy-hydroxides perform very well in adsorbing phosphonates from membrane concentrates. Therefore, an iron oxy-hydroxide was selected that, in contrast with WFS, has a high purity and can be obtained commercially. Granular ferric hydroxide (GFH) was investigated as an adsorbent for NTMP in Chapter 3. Both the equilibrium and kinetics of NTMP adsorption on GFH were investigated. The adsorption kinetics were predicted fairly well with two models that considered either combined film-pore or combined film-surface diffusion as the main mechanisms for mass transport. It was demonstrated that phosphonate is preferentially adsorbed over sulfate by GFH and that the presence of calcium is beneficial for the adsorption process. Calcium causes a transformation in the equilibrium adsorption isotherm from a Langmuir type to a Freundlich type with much higher adsorption capacities. Spent GFH is reusable after regeneration with a sodium hydroxide solution, showing that NTMP can be recovered from the RO concentrate. In analogy with Chapter 3, the adsorption and desorption of NTMP from RO membrane concentrate on iron-coated waste filtration sand (WFS) has been investigated in Chapter 4. Equilibrium adsorption was described well with a Langmuir isotherm. Although the low cost and on-site availability of WFS is advantageous over GFH, the results revealed some drawbacks. WFS appeared to have a much lower adsorption capacity compared to GFH, which was related to the presence of impurities, the presence of manganese oxides, and aging of the ferrihydrite phase in the coating of WFS. The aim of Chapter 5 was to employ GFH in a packed bed adsorption column. The effective diffusivities and external film mass transfer coefficients estimated in Chapter 3 were used to predict the concentration of phosphonate in the effluent. Also, the regeneration of the saturated column with sodium hydroxide solution was investigated. In addition, it was investigated whether the regeneration solution containing the recovered phosphonate could be further concentrated by using a nano-filtration or a calcium-phosphonate precipitation step. The use of nano-filtration seemed to be more attractive. The first five chapters show that adsorptive removal of phosphonate antiscalants offers a viable way to improve RO concentrate treatment processes and enables the recovery of the phosphonate for reuse in the RO desalination process. Another way of tackling the unwanted discharge of phosphonates is minimizing their use. Smart sensors that predict the risk of scaling at an early stage can help to control the dosage of phosphonate antiscalants. This will allow for minimum usage of phosphonates without the risk of scaling. Chapters 6, 7, and 8 contribute to the development of such a sensor. Focus was on the development of the actuator part of the sensor that enhances crystal growth and precipitation by ultrasonic irradiation. In Chapter 6 the effect of ultrasonic irradiation on the crystallization of calcite was investigated. Seeded calcite growth experiments were conducted under constant composition conditions while the applied ultrasonic irradiation created cavitation bubbles throughout the suspension. In this way it was demonstrated that ultrasound enhances the crystallization rate of calcite substantially (i.e., 46 %), due to the ability of the generated cavitation bubbles altering the crystals’ habit and size. The increased surface area available for crystal growth resulted in enhancement of the observed crystallization rate. In Chapter 7, the cavitation phenomena that are responsible for the previously observed volumetric crystallization rate enhancement were visualized using high speed photography. Cavitation clusters cause attrition, disruption of aggregates and deagglomeration, whereas streamer cavitation causes deagglomeration only. Cavitation inception on the surface gave the small crystals momentum. However, it was shown that breakage of accelerated crystals by interparticle collisions is unrealistic because, upon bubble collapse, they subsequently experienced a deceleration much stronger than expected from drag forces. These direct observations contradict the general assumption that interparticle collisions always play an important role in particle attrition by cavitation. Scanning electron microscopy pictures of irradiated calcite crystals showed deep circular indentations, possibly caused by shockwave induced jet impingement. Moreover, the appearance of voluminous fragments with large planes of fracture indicated that acoustic cavitation can also cause the breakage of single crystal structures. The possibility of using ultrasound as a tool to enhance the demineralization of supersaturated calcium carbonate solutions (e.g., membrane concentrates) containing growth inhibitors was investigated in Chapter 8. The inhibiting effect of the phosphonate NTMP on crystal growth can be mitigated by ultrasonic irradiation. The results can be explained in part by breakage and attrition of poisoned crystals, resulting in an increase in fresh surface area. Mass spectroscopy analysis of sonicated NTMP solutions revealed that ultrasound can also degrade NTMP. These observations confirm in part the hypothesis that ultrasound can be used as actuator. As an alternative to the removal of phosphonates or minimizing their use by smart sensoring techniques, phosphonates may also entirely be replaced by environmental friendly antiscalants, which is the subject of Chapter 9. The effectiveness of such an alternative, carboxymethyl inulin (CMI) biopolymers, in inhibiting calcium carbonate crystallization was compared to two phosphonate antiscalants. Compared to the phosphonates, the biopolymers exhibited a stronger inhibitory effect on the crystal growth of calcite. It was shown that the ability of the biopolymers to mitigate the spontaneous precipitation of calcium carbonate is controlled by their degree of carboxylation. The biopolymers can affect the crystal habit similar to the phosphonates, which suggests that their function as crystal growth inhibitor is comparable. These results demonstrate that CMI biopolymers are effective calcium carbonate crystallization inhibitors, indicating they can replace phosphonates as antiscalant. In Chapter 10, the results presented in this work are being discussed and, where possible, placed into perspective of future desalination developments.Process and EnergyMechanical, Maritime and Materials Engineerin
Supercritical Fluid Extraction of Metals from Contaminated Solid Matrices
No full textMechanical Maritime and Materials Engineerin
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