Enhanced separation of azeotropic mixtures by ultrasound-assisted distillation process

The main objective of this study is to develop an ultrasound-assisted distillation process that can break minimum boiling azeotropes under various operating conditions for enhancing the effectiveness of distillation processes in providing solution to high purity separation requirement. As a case study, ethanol/ethyl acetate (ETOH/ETAC) separation process was considered. The effect of both intensity and frequency of the ultrasonic waves on the vapor–liquid equilibrium (VLE) of this system was experimentally studied. The sonication was found to affect the VLE significantly in a way which led to an alteration in the relative volatility and a complete elimination of the azeotropic point, with the preference towards a combination of low frequency and high intensity operation. A mathematical model describing the system was developed based on conservation principles, VLE of the system and sonication effects. The model, which took into account a single-stage VLE system enhanced with ultrasonic waves, was coded using the Aspen Custom Modeler. The effects of ultrasonic waves on the relative volatility and azeotropic point were examined and the experimental data were successfully used in validating the model with a reasonable accuracy. The mathematical model was exported to the Aspen Plus to form a model that represents the sonication equilibrium stages, which were connected serially to configure an ultrasound-assisted distillation (UAD) process for separation of ETOH/ETAC mixture. The simulation results revealed that ETAC can be recovered from the azeotropic mixture with a purity of 99 mol% using 27 sonication stages. To validate the suitability of UAD process for separation of other minimum boiling azeotropes, separation of other mixtures were tested such as ethanol/water, methanol/methyl acetate and nbutanol/ water. The developed model was found to have some limitations with respect to separation of maximum boiling azeotropes

Development of a small production platform for citronellal processing

The aim of the project was to develop a small production platform for citronellal processing. The objective of the study was to develop a single continuous flow reactor system for the synthesis of novel derivatives of citronellal and isopulegol. The first step was to develop a continuous flow reactor system for the isopulegol synthesis. The stainless steel tubular fixed-bed reactor equipped with a reaction column (I.D: 9.53 mm and length: 120 mm) was used for the study. The reactor column was packed with H-ZMS-5 zeolite extrusion catalyst. The solvent-free cyclisation reaction of citronellal was investigated and at optimum conditions, 100% of citronellal conversion and almost 100% selectivity towards isopulegol was achieved. A good catalytic performance was observed from the H-ZSM-5 catalyst and proved to be stable for a prolonged reaction time. The second reaction step was to develop a continuous flow reactor system for the synthesis of isopulegyl-ether derivatives. A UniQsis FlowSyn reactor system equipped with a stainless steel reactor column was used for the study. The reactor column was packed with amberlyst-15 dry catalyst. Wherein, n-propanol was employed as a model etherifying agent and as a reaction solvent. At optimum reaction condition, only 30% selectivity of isopulegyl propoxy-ether was achieved. The reaction was found to depend highly on temperature and residence time. The increase of these parameters was found to increase the side reactions and reduced the selectivity of the desired product. Other heterogeneous catalysts such as H-beta zeolite, aluminium pillared clay, Aluminium oxide and H-ZSM-5 were also evaluated in the reaction. Among these catalysts, a catalytic activity was observed with H-beta zeolite (19%) and aluminium pillared clay (5%). Based on these results, none of the evaluated catalysts provided the desired selectivity (greater than 70%) towards the isopulegyl propoxy-ether, therefore the process was not investigated further. In light of this, the isopulegol etherification synthetic route was terminated. Consequently, another analogue of citronellal was used as an alternative intermediate in place of isopulegol, namely para-menthane-3,8-diol (PMD). The initial studies for the synthesis of the novel PMD di-esters from isopulegol were performed in the batch-scale reactor. In a solvent-free reaction, acetic anhydride was initially used as a model acetylating agent. The reaction was performed using polymer-bound scandium triflate (PS-Sc(OTf)3) catalyst. The effect of reaction parameters such as temperature, molar ratio, and reaction time were studied towards the PMD conversion and di-esters selectivity. At optimum reaction conditions, PMD conversion of 70% and di-acetate selectivity of 67% were observed. The reaction was found to follow the zeroth-order kinetics with respect to PMD conversion and obeyed the Arrhenius equation. Other types of di-ester derivatives were synthesized from PMD by varying the carbon chain length of the acetylating agent. The prepared compounds were separated from the product mixtures by vacuum distillation, purified on a column chromatography and characterised by FT-IR, GC-MS, and 1H-NMR, 13C-NMR. The developed methodology was optimised in flow by using an ArrheniumOne microwave-assisted continuous-flow fixed-bed reactor system. A detailed experimental design was used to carry-out the reactions. The reaction parameters such as temperature and flow-rate were studied towards the PMD conversion and di-ester selectivity. From the experimental design analysis, the di-ester selectivity was found to depend highly on the residence time (flow-rate) and significantly on temperature. The PMD conversion and di-ester selectivity were found to increase with decrease in the flow-rate. The conversion and selectivity achieved in the continuous flow process were significantly higher than the achieved in the batch-scale process with respect to the residence time

Cell-free enzymatic biosystem for the conversion of glucose to malate

Platform chemicals are essential to industrial processes. Used as starting materials for the manufacture of diverse products, their cheap availability and efficient sourcing are an industrial requirement. Increasing concerns about the depletion of natural resources and growing environmental consciousness have led to a focus on the economics and ecological viability of biobased platform chemical production. Biobased strategies such as fermentation still have limitations that restrict their large scale industrial application. Current microbial biomanufacturing is hindered by the limitations caused by cells, as synthetic pathways and their optimizations are restricted by the physiological limits of the cellular production system. Cell-free metabolic engineering is pushing the boundaries of traditional bioengineering models by focusing on the use of in vitro combinations of catalytic enzymes prepared from purified proteins or crude lysates from cells, assembled in artificial cascades, for production of target commodities.This thesis describes a cofactor balanced, cell-free, 5 enzyme biosystem for the sustainable production of malic acid from glucose, whereby 5 thermophilic proteins (glucose dehydrogenase, dihydroxy-acid dehydratase, 2-keto-3-deoxygluconate aldolase, glyceraldehyde dehydrogenase and malate dehydrogenase) were successfully expressed, purified and demonstrated to display enzyme activity. Enzyme immobilization has been used by many researchers to overcome instability problems and facilitate the repetitive use of enzymes. Recombinant glucose dehydrogenase from S. solfataricus was successfully purified and immobilized onto novel supports and demonstrated great potential for gluconic acid production from glucose, as well as bread waste hydrolysate in a sustainable production approach. Coupling of cofactor recycling enzymes (glucose dehydrogenase and malate dehydrogenase) was also explored and successfully demonstrated the simultaneous production of chemicals and cofactor recycling capabilities. The experimental work also identified potential bottlenecks affecting the feasibility of the cell-free biosystem and paves the way for optimized characterization of enzymes in the cascade, in the free-state, individually immobilized and co-immobilized

Catalytic Conversion of Glycerol to Value-Added Chemical Products

Rapid expansion of biodiesel industry has generated a huge amount of crude glycerol. This thesis aimed to explore utilization of glycerol for the production of solketal as an oxygenated fuel additive and 1, 2-propanediol as a pre-polymer via catalytic conversion. The thesis work may be divided into two major parts. In the first part, the thermodynamics and kinetics of the glycerol ketalization for the synthesis of solketal were investigated in a batch reactor. From this information, a continuous-flow process was designed, developed and optimized using pure glycerol. Crude glycerol (13 wt% purity) was successfully upgraded into a purified crude glycerol product (\u3e 96 wt% purity) and was used as feedstock in a modified reactor for the synthesis of solketal whose economical feasibility was demonstrated. In the second part, B2O3 promoted Cu/Al2O3 catalysts were used for selective hydrogenolysis of glycerol to 1, 2-propanediol in a flow reactor. Surface properties, acidity, crystallinity, and reducibility of the catalysts were measured using N2 adsorption, NH3-temperature programmed desorption (TPD), X-ray diffraction (XRD), and H2-temperature programmed reduction (TPR), respectively. The fuels/chemicals products obtained were analyzed by GC-MS/FID and Fourier-transformation infrared spectroscopy (FTIR). The ketalization reaction equilibrium constants were determined experimentally in the temperature range of 293-323 K. The activation energy of the overall reaction was determined to be 55.6 ± 3.1 kJ mol-1. Langmuir-Hinshelwood equation was used to model the rate law. The activity of all catalysts tested in the flow reactor follows the order: Amberlyst wet » Zeolite » Amberlyst dry \u3e Zirconium Sulfate \u3e Montmorillonite \u3e Polymax. At optimum conditions (25 ˚C, 500 psi, acetone-to-glycerol molar ratio of 4 and 2 h-1 WHSV), the maximum solketal yield from pure glycerol was 94±2% over Amberlyst wet. Ketalization of purified crude glycerol over Amberlyst wet, led to 93± 3% glycerol conversion with 92 ±2% solketal yield at the optimum conditions. In the glycerol hydrogenolysis process with 10 wt% aqueous solution of glycerol as the feed, 5Cu-B/Al2O3 catalyst demonstrated a very high activity, yielding 98 ±1% glycerol conversion and 98±1% 1,2-propanediol selectivity at the optimum conditions (250 ˚C, 6 MPa H2, and 0.1h-1 WHSV)

Studies on the Chemical recycling of Poly(lactic acid) via Alcoholysis

Continual reduction of landfill space, rising CO2 levels, and plastic pollution are global issues that will only grow in time if not correctly addressed. The opportunity exists to replace petroleum-derived plastics with bioplastics. This, in conjunction with mechanical and chemical recycling, is a potential remedy that enables a circular economy. PLA is a leading bioplastic; its growing production capacity means its end-of-life treatment is becoming increasingly important. One beneficial disposal route for PLA is its chemical recycling via alcoholysis. The alcoholysis of PLA leads to the generation of value-added products alkyl lactates; this route also has potential for a circular economy. In this work, the alcoholysis of PLA was studied in a autoclave reactor. A range of alcohols were used as reactants to generate various alkyl lactates. Discrete synthesised catalysts and commercially available catalysts were investigated, as well as dual catalysis systems. Three kinetic models were applied to the experimental data: a simple first order model that only considers the initial degradation of PLA, a two-step consecutive model with irreversible second step, and a two-step consecutive model with the second step in equilibrium. This work concluded that increasing the nucleophilic alcohol chain length decreases alcoholysis reaction rate; the increased steric hinderance of a larger alcohol inhibits coordination to the catalyst and PLA ester groups. This work also concluded that dual catalyst synergy is only present if there is a great enough difference in pKa for each catalyst in addition to having both acid and base character. Further research is needed to fully explore synergistic Lewis acidsbase pairs; an understanding of their coordination and mechanism is required in order to fully exploit dual-catalysts systems for enhanced chemical recycling. The chemical recycling of PLA via alcoholysis is a promising end-of-life solution, adding value to the PLA supply chain through the generation of value-added ALs

Expression of multidisciplinary flavour science : proceedings of the 12th Weurman Symposium

The 12th Weurman Flavour Research Symposium contributed 177 lectures and posters to the wealth of flavor knowledge; these were presented in eight sessions: biology, retention and release, psychophysics, quality, thermal generation, bioflavors, impact molecules, and analytics. Emerging topics were discussed in three workshops dealing with flavor and health, in vivo flavor research, and flavor metabolomics. It has been an excellent forum for passionate exchange of recent results obtained in traditional and emerging fields of flavor research. The symposium allowed coverage of the broad diversity of flavor-related topics: comprising odor and taste; applying targeted and holistic approaches; using sensorial, chemical, biological, physical, and chemometric techniques; as well as considering nutrition and health aspects

Expression of multidisciplinary flavour science : proceedings of the 12th Weurman Symposium

The 12th Weurman Flavour Research Symposium contributed 177 lectures and posters to the wealth of flavor knowledge; these were presented in eight sessions: biology, retention and release, psychophysics, quality, thermal generation, bioflavors, impact molecules, and analytics. Emerging topics were discussed in three workshops dealing with flavor and health, in vivo flavor research, and flavor metabolomics. It has been an excellent forum for passionate exchange of recent results obtained in traditional and emerging fields of flavor research. The symposium allowed coverage of the broad diversity of flavor-related topics: comprising odor and taste; applying targeted and holistic approaches; using sensorial, chemical, biological, physical, and chemometric techniques; as well as considering nutrition and health aspects

SEPARATION AND PURIFICATION OF BIOFUELS AND SOLVENTS VIA PERVAPORATION PROCESS

Ph.DDOCTOR OF PHILOSOPH