Interest in biodiesel has been growing due to its potential role in moderating global climate change by lowering net CO2 emissions from fuels used for transportation. Most biodiesel fuels are currently synthesized by transesterification using alkaline catalysts and methanol. Heterogeneous transesterification catalysts have begun to be considered as alternatives, but many drawbacks remain. The costs of production and environmental concerns resulting from the ester washing step: neutralization of residual catalyst, removal of soap, glycerol, methanol and absorbent in some cases have prompted the search for more environmentally friendly processes and solid catalysts. Therefore, it is desirable to replace homogeneous or heterogeneous transesterification with the use of heterogeneous catalysts in direct thermocatalytic cracking. In principle, this could reduce the cost of biodiesel production, as it removes the need for alcohol and numerous downstream processing steps which add to the substantial running costs of transesterification. In addition the problem of glycerol in the product is eliminated. Four sulphated zirconia catalysts were synthesized via conventional wet-precipitation and solvent-free methods with different molar ratios of the sulphating agent. Their activity for direct thermocatalytic cracking of rapeseed oil was evaluated at a temperature of 270oC and atmospheric pressure. The nature and concentration of the active Brønsted and Lewis acid sites on the catalysts were examined. Brønsted acid sites were found to be important in the catalytic reaction. The catalysts at this temperature exhibited different selectivities towards formation of saturated and unsaturated methyl esters. The solvent-free catalysts were more active with a conversion of 78% in 21/2 hours, while the wet-precipitated catalysts had a maximum of 66% conversion after two hours. The catalysts prepared by the solvent-free method had 59% yield for methyl ester, with 75% of these being unsaturated. The wet-precipitated catalysts exhibited a lower yield for methyl esters (maximum: 32%), but within this a greater proportion (68%) were saturated. After regeneration, the solvent-free catalysts regained their catalytic properties, whereas the conventional catalysts did not. Three of the catalysts exhibited substantial leaching, with one of the conventional catalysts losing 100% of the sulphate responsible for its activity. Thus, to improve their properties the catalysts were supported with meta-kaolin which resulted in higher Brønsted acidity and better stability.

The production of biodiesel by the transesterification reaction of glycerides (rapeseed oil) with methanol, in a continuous-flow fixed-bed catalytic reactor was explored. Based on data in the literature, lanthanum oxide and strontium oxide (SrO) catalyst systems were selected for this work. In preliminary experiments in a batch reactor (300 cm3; with 160 cm3 of oil), ceramic monoliths (61 cells cm-2; hydraulic cell diameter = 1.1 mm) acted as catalyst supports. At the conditions tested (T= 120ºC; P = 8 bar(g); molar ratio methanol:oil = 6:1), the monoliths coated with SrO (19.6 wt% SrO), were found to be sufficiently active to proceed to the continuous flow fixed-bed trials. A study of the solubility of methanol in oil, showed that in a pressurized autoclave at 100ºC, the methanol dissolved at a 6:1 molar ratio, and at 120ºC this increased up to 9:1, providing useful information for the design of a continuous flow reactor. The SrO slurry coated monolith was then tested in a single-tube fixed-bed reactor (i.d. = 6.2 mm; L = 200 mm). In experiments at a 7:1 molar ratio of methanol:oil, at T = 195 ºC, and P = 20 bar(g), although catalytic activity was cyclic in nature, it was maintained over a 300 h period (not continuous) of operation. This led to the performance of experiments in a multi-tubular reactor, which consisted of 5 tubes, connected in series (each tube with an i.d. = 22 mm; L = 550 mm). It was now possible to perform experiments with a longer overall length of monolith sections, and to take samples between each tube. Experiments were performed with a monolith bed length of 2300 mm and a molar ratio of methanol:oil = 7:1 (T = 150ºC, P = 15 bar(g)), with overall conversions ranging from 20 to 50%.

Intelligent control techniques that emulate characteristics of biological system offer opportunities for creating control products with new capabilities. Intelligence is a mental quality that consists of the abilities to learn from experience, adapt to new situations. Artificial intelligence as the ability of a digital computer to perform tasks commonly associated with intelligent beings. The objective of this PhD studies is to undertake extensive research activities to simulate, design and implement various types of intelligent controllers such as error-base adaptive, conventional fuzzy logic, self-tuning fuzzy using Iterative Learning Control (ILC), inverse Adaptive NeuroFuzzy Inference System (ANFIS) controller, genetic-ANFIS controller, and adaptive PID controller. These techniques aimed to control and monitor in real time the performance of the microwave reactor to produce a biodiesel from any fats or waste cooking oil, with a potential of scale up system to be characterised for use in industrial environments. The other objective of the project is to use for the first time a microwave reactor to speed up the process of transesterification reaction in order to produce higher yield. Within the biodiesel production system the microwave reactor plays an important role. However, due to its non-linear nature then a complex control of the reactor is required as unsuccessful reaction step due to any disturbances or changes in the reaction conditions can have a significant impact on the transesterification reaction, leading to an incomplete conversion of waste oil to biodiesel. Ultimately this can lead to a reduction in product yield and quality, an issue which is further compounded by complex heat and mass transfer characteristics, frequent overshoot of temperature and oscillation of pressure within the reactor. Therefore, good control is essential for quality biodiesel production.

The work reported in this thesis presents an investigation into the various alternative sources of oil for biodiesel production that are considered not to compete with sources of oil for food. Croton megalocarpus seeds, an oil seed from a tree commonly found in eastern Africa has been selected for this study. Currently, Croton megalocarpus tree is used for timber and building poles and as barriers among farmlands. The tree is large and grows to about 30 to 40m high and the seeds produced oil (30 - 35%) but are not consumed because of its cathartic property. The tree grows on marginal lands where no agronomic practices are required. It also serves as a mulching tree that helps to restore the forest vegetation. Field work was undertaken to Kenya for this study. The Croton megalocarpus seeds were studied for their physical and mechanical properties. The size, shape, surface area, angle of repose, coefficient of friction, moisture content and the compression behaviour of the seeds were studied and reported on. The oil from Croton seeds was studied and reported upon for its properties and constituents such as density, gross calorific value, ash content, carbon, hydrogen and oxygen at the fuel oil bunker and analysis services (FOBAS), Llyods Register London. The oil was converted to biodiesel following the method outlined in BS 14105 method. The Croton oil was found to have a calorific value of 40,280kJlkg. The biodiesel properties were analysed on a GC machine to find out the compositions of its methyl ester. The biodiesel was then tested according to BS8186-C on a Perkins D3142, 3 cylinder, 4 stroke, DI marine engine to determine the performance and exhaust emissions as compared to a no 2 diesel. The performance of the biodiesel has been found to be comparable to the normal hydrocarbon diesel and the exhaust emissions has shown a significant drop in the regulated exhaust gases (CO, PM, Smoke, HC), with a slight increment in the exhaust of NO x at some speed and load range. The results of the research presented the Croton properties that lead to a conclusion that Croton oil is a viable and alternative source of biodiesel. Recommendations were made as to ways of improving the oil yields and better agronomic practices to shorten the maturity period of the tree.

Biodiesel is a mixture of an alkyl ester of long chain fatty acids produced by transesterification of triglycerides with lower alcohols such as methanol, in the presence of acid or base catalysts. Nearly all biodiesel processes use homogeneous base catalysts that cannot be recovered and necessitate neutralisation of the glycerol-rich phase (a by- product of the reaction). This increases the number of downstream separation steps, thereby increasing the capital cost of biodiesel production processes. Replacing liquid homogeneous catalysts with solid heterogeneous catalysts can intensify the process, by reducing the total number of process steps, eliminate or reduce waste streams and result in lower production costs, as the catalyst will not have to be continually replaced. Strong anion exchange resins with QN+OR, have the potential to be developed and employed as heterogeneous catalyst for transesterification, as they are chemically stable to leaching of the functional group. In this present work, nine different synthesized anion exchange resins (SIERI-9) were prepared by suspension polymerization of vinylbenzyl chloride-divinylbenzene (YBC-DYB) copolymers in the presence of n- heptane as a pore-forming agent. These SIERs were evaluated as catalysts for transesterification of triacetin. It was found that the "SIER-6" catalyst prepared with the highest dilution degree (200%) and the lowest DYB content (10% DYB), achieved the highest triacetin conversion (95.6% after 4h). This catalyst had the highest true pore volume (0.89 cm3/g) and surface area (398.8 m2/g). In contrast, the "SIER-7" catalyst synthesized with the lowest dilution degree (50%), but highest DYB content (40%), resulted in the lowest triacetin conversion at 64.3%. Although there is a considerable improvement in the physicochemical properties of the IERs, such as surface area, 'true pore' volume and diameter, transesterification using rapeseed oil was rather poor with only 16 wt. % of FAME obtained over SIER-6 after 6h reaction. Overall, the ion exchange resin-catalyzed reaction were well-described by the Eley- Rideal model. Significantly, the ER model data fitted the experimental data for all ion exchange resins studied in this work.

Biodiesel is a diesel-related fuel manufactured from vegetable oils, recycled grease, or animal fats. It is technically competitive with, or offers technical advantages when compared to, conventional diesel fuel. However, the freezing and gelling behaviour of many biodiesel formulations are potentially limiting their applications. It is known that the use of additives is an efficient way to improve the cold flow properties of formulated, so it is very important to clarify the mechanism and effect of additives. Molecular cluster modelling work has been explored to study the effect of additives on crystallization temperature, meta-stable zone width and solubility. A new method has been developed for the prediction of crystallisability through the comparison of structural variability of molecular clusters of pure naphthalene, pure biphenyl, and naphthalene in the presence of biphenyl and vice versa. The approach has been validated through the experimental determination of crystallization temperatures and meta-stable zone width. The predicted growth morphologies of methyl stearate have been derived through attachment energy calculations and the resulting surface chemistry of the morphological habit faces characterized. Molecular simulations using grid search methods combined with experimental observed images were used to investigate the solvent-mediated effect on crystal habits of methyl stearate. Tubidometric studies employing a 100ml batch crystallizer operating in a polythermal mode confirmed the change of crystallization temperature and the meta-stable zone width of methyl stearate with or without additives. Related crash-cooling studies enabled the characterization of crystallization kinetics with or without additives through examination of set paints as a function of supersaturation.

No description available.

Τη σημερινή εποχή, η εξάντληση των αποθεμάτων των ορυκτών καυσίμων, σε συνδυασμό με τις αυξανόμενες ενεργειακές ανάγκες, οδήγησε στην παραγωγή των βιοκαυσίμων. Με αυτό τον όρο νοείται κάθε καύσιμο που παράγεται από βιομάζα. Ένα από τα δημοφιλέστερα βιοκαύσιμα στην Ευρώπη είναι το βιοντίζελ, το οποίο λαμβάνεται μετά από μετεστεροποίηση τριγλυκεριδίων που περιέχονται σε φυτικά έλαια και ζωικά λίπη. Οι λόγοι που οδήγησαν στην παραγωγή βιοντίζελ είναι περιβαλλοντικοί αλλά και οικονομικοί, καθώς η αύξηση της χρήσης των ορυκτών καυσίμων επιβάρυνε και συνεχίζει μέχρι σήμερα την ατμοσφαιρική ρύπανση αλλά και η αύξηση της τιμής του πετρελαίου δυσχεραίνει την οικονομική κατάσταση πολλών χωρών που εισάγουν ορυκτά καύσιμα. Στην παρούσα διπλωματική εργασία, παρουσιάζονται τα βιοκαύσιμα 1ης και 2ης γενιάς, οι πρώτες ύλες από τις οποίες προέρχονται, πως αξιοποιούνται, ποια είναι τα πλεονεκτήματα και τα μειονεκτήματα αυτών και στη συνέχεια δίνεται μεγαλύτερη έμφαση στο φυτό Jatropha curcas, το οποίο αποτελεί την πηγή για την παραγωγή βιοντίζελ 2ης γενιάς. Στο τρίτο κεφάλαιο αυτής της διπλωματικής εργασίας, γίνεται παρουσίαση του φυτού, ανάλυση των μορφολογικών χαρακτηριστικών του, περιγραφή της καλλιέργειάς του, των αναγκών του, αναφέρονται οι χώρες στις οποίες έχει διαδοθεί, ο τρόπος επεξεργασίας του, και οι χρήσεις του σε άλλες διεργασίες μέχρι σήμερα. Ακόμη γίνεται γνωστό το κόστος παραγωγής του, η απόδοσή του σε έλαιο και συγκρίνεται με τις βασικές πρώτες ύλες μέχρι στιγμής για την παραγωγή βιοντίζελ. Τέλος, αναφέρονται ευρωπαϊκά και παγκόσμια προγράμματα και πειράματα, στα οποία έχει μελετηθεί η απόδοσή του. / --

As the global population rises to an estimated 9.4bn by 2050, the pressure for food, fuel and freshwater will continue to increase. Current renewable energy technologies are not widely applicable to the transport sector, which requires energy dense liquid fuels that drop into our existing infrastructure. Algal biofuels promise significantly higher yields than plants, without the displacement of valuable agricultural resources and have the potential to meet the global demand for transport fuel. Fossil fuel energy is largely ‘a legacy of algal photosynthesis’, with algae accounting for ~50% of global CO2 fixation today. In addition, these curious organisms show remarkable diversity in form, behaviour and composition. Recently there has been a global resurgence of interest in microalgae as a resource of biomass and novel products. With the present level of technology, knowledge and experience in commercial scale aquaculture, the capital cost and energy investment for algal biomass production is high. Culturing, harvesting and disrupting microalgal cells account for the largest energy inputs with more positive energy balances requiring low energy designs for culture, dewatering and extraction, efficient water and nutrient recycling with minimal waste. Little is known about the variable cell wall of microalgae, which presents a formidable barrier to the extraction of microalgal products. Staining, transmission electron microscopy (TEM) and enzymatic digestion were all utilised in an attempt to visualise, digest and characterise the cell wall of stock strains of Chlorella spp. and Pseudochoricystis ellipsoidea. The presence of algaenan, a highly resistant biopolymer, rendered staining and enzymatic digestion techniques ineffective. TEM revealed that algaenan is present in the outer walls of microalgae in a variety of conformations which appeared to impart strength to cells. A preliminary investigation utilising Fusarium oxysporum f.sp. elaeidis as a novel source of enzymes for the digestion of algaenan has also been described. Methods were developed for the mutagenesis of Chlorella emersonii and P. ellipsoidea using EMS and UV with the intent of generating cell-wall mutants. Although no viable cell wall mutants were produced, a viable pale mutant of C. emersonii was recovered 5 from UV mutagenesis. Growth rates of the pale mutant were significantly slower than the wild type, yet FAME profile was largely unaffected. Fluorescence activated cell sorting (FACS) was also investigated as a means for the rapid screening of mutagenized cells for cell wall mutants. In an attempt to reduce cooling costs of closed-culture systems, temperature tolerant species of microalgae were sought by bioprospecting the thermal waters of the Roman Baths. Numerous methods for isolation and purification of microalgae from the Baths were employed, ultimately yielding seven diverse isolates including cyanobacterial, eukaryotic, filamentous and single celled species. Despite some species possessing an increased tolerance to higher temperatures, none showed marked temperature tolerance coupled with high productivity. Further improvements to the culture conditions may have improved the productivity at higher temperatures. All seven isolates were deposited to the Culture Collection of Algae and Protozoa (CCAP). A variety of extraction methods including soxhlet, beadbeating, sonication and microwaving was investigated for efficacy of extracting fatty acid methyl esters (FAMEs) from C. emersonii. Beadbeating proved most effective in the extraction of FAMEs from C. emersonii. Microwaving showed potential as a rapid method of extraction yet was coupled with degradation of FAMEs, requiring further method development to resolve this issue. Method development has been a significant component of the work described in this thesis.