Intensification of polyester synthesis by continuous reactive distillation

The thesis starts with a brief overview of unsaturated polyesters. In particular, the usage of raw materials, the application of unsaturated polyester resins, and, the worldwide supply and demand of the unsaturated polyester resins are discussed. Unsaturated polyester is traditionally produced in a batch-wise-operating reaction vessel connected to a distillation unit. The total production time is around 12 hours and often leads to batch-to-batch inconsistency. Process intensification is required for the unsaturated polyester process to reduce the production time and to achieve a better quality of the product. An attractive alternative to batch-wise polyester production is reactive distillation. In chapter 1, the attractiveness of reactive distillation for the synthesis of unsaturated polyester is discussed. The goal of the thesis is to develop and evaluate a reactive distillation process for the production of unsaturated polyester from anhydrides and glycols. To accurately predict the behavior of reactive distillation process, reliable kinetic and thermodynamic models are required. Therefore, in chapter 2 a dynamic model for a batch-wise operating reaction vessel connected to a flash separation unit is developed in order to validate the kinetic and thermodynamic models and their parameters. This model includes kinetics, description of the change of rate order during the reaction, the polymer NRTL non-ideal thermodynamic model based on non-random theory of liquid (NRTL) and mass balances. The reaction between maleic anhydride and propylene glycol has been taken as a case study. The reaction scheme is complex and the proposed model takes four types of reactions into account; ring opening, polyesterfication, isomerization and saturation reactions. The acid value of the polyester, number-average molecular weight, distilled mass and glycol concentration in the distillate have been subsequently used to validate the model and the model predicts these important variables reliably. The process description is improved by using the vapor liquid equilibrium data predicted from the polymer NRTL model. After successful validation of the kinetic and thermodynamic models, the feasibility of the reactive distillation process for the unsaturated polyester is presented in chapter 3. Moreover, the simulation results of reactive distillation model are compared with the batch reactor model simulation results to determine advantages gained by the reactive distillation over the traditional batch process. The simulation study shows that the total production time of polyester in a continuous reactive distillation system is reduced to 1.8-2 hours compared to the12 hours of the industrial batch reactor process. The model demonstrated that reactive distillation has the potential to intensify the process by factor of 6 to 8 in comparison to the batch reactor process. After finding that reactive distillation is an attractive alternative for the polyesters synthesis, a more in depth analysis is performed. Particularly, the influence of the liquid back mixing on the description of the reactive distillation process, product transition time, the amount of undesired product formation during the product changeover is investigated. Since the current state of the art modelling approach does not account for liquid back mixing, the rate-based model is extended to account for liquid back mixing. The simulation results of extended rate-based model demonstrated that axial dispersion significantly influences the reactive distillation process and cannot be neglected. On the basis of current research work and literature review, a novel design methodology for the economical and technical evaluation of reactive distillation is proposed in chapter 4. Moreover, the applicability of various design methods for reactive distillation is discussed. The proposed framework for the economical evaluation determines the boundary conditions (e.g. relative volatilities, target purities, equilibrium conversion and equipment restriction), checks the integrated process constrains, evaluates economical feasibility, and provides guidelines to any potential reactive distillation process application. Providing that a reactive distillation process is economically attractive, a technical evaluation is performed afterward in order to determine the technical feasibility, the process limitations, working regime and requirements for internals as well as the models needed for reactive distillation. This approach is based on dimensionless numbers such as Damkohler and Hatta numbers, as well as the kinetic, thermodynamic and mass transfer limits. The proposed framework for economical and technical evaluation of reactive distillation allows a quick and easy feasibility analysis for a wide range of chemical processes. Several industrial relevant case studies (synthesis of di-methyl carbonate (DMC), methyl acetate hydrolysis, toluene hydro-dealkylation (HDA) process, fatty acid methyl esters (FAME) process and unsaturated polyesters synthesis) are used to illustrate the validity of the proposed framework. In chapter 4, it is found that the bubble column is the potential device for producing unsaturated polyesters by the reactive distillation. Moreover, the introduction of packing or partition trays in the bubble column significantly improves the unsaturated polyester process because packing or partition trays provide a better mass transfer and the multi-stage effect in the column. But considering the lack of information about the behavior of counter-currently operated bubble columns in the presence of structured packing or partition trays and in a viscous system, a systematic investigation on the gas holdup, axial dispersion and mass transfer in the packed bubble column and the trayed bubble column is undertaken in chapter 5. Four different types of structured packings (Super-Pak, Flexipac, Mellapak and Gauze) and two types of perforated partition trays (with 25% and 40% tray open area) are used to characterize the packed and trayed bubble column, respectively. It is observed that the packed and trayed bubble columns improve the gas holdup and mass transfer compared to the empty bubble column and reduces the axial dispersion significantly. Particularly, the Gauze packing improves the gas holdup and mass transfer and, sufficiently reduces the axial dispersion. In contrast, Super-Pak offers only a modest improvement because of its open structure. Comparison of the experimental data of the packed and trayed bubble column indicates that the partition trays improve the bubble column in the same order as packing. The gas holdup, axial dispersion and mass transfer depend more strongly on the gas velocity compared to the liquid velocity. The liquid viscosity also significantly influences these parameters and therefore the empirical correlations obtained from the air-water system cannot be applied for the viscous system. Moreover, experimental data of the packed, trayed and empty bubble column are correlated by dimensionless numbers. Empirical correlations for the gas holdup, Bodenstein number (for the axial dispersion coefficient) and Stanton number (for the volumetric mass transfer coefficient) as a function of the Froude and Gallilei dimensionless numbers are proposed. In chapter 6, an experimental pilot plant validation of the reactive distillation process for the polyester synthesis is presented. Two different configurations are investigated: 1) a reactive distillation column and 2) a reactive distillation column coupled with a pre-reactor. Due to a relatively short residence time of 0.32 hours and an operating temperature of 190oC in case of the first configuration, a maximum conversion of 37% was achieved; which indicates monoester formation in the reactive distillation column. In the case of the second configuration, a 90% conversion is achieved within 0.55 hours at a temperature of 250oC in the reactive distillation column coupled with a pre-reactor; which confirms the polyester formation in the reactive distillation column. The extended rate-based model developed in chapter 3 is used to simulate the pilot reactive distillation column. The model predicted the experimental data (acid value, conversion, isomerization and saturation fraction, number-average molecular weight, the degree of polymerization and water fraction in the distillate) adequately (5-22%). Moreover, the product specifications of the polyester produced at 250oC in the reactive distillation column is in the range of polyesters produced in the traditional industrial batch reactor setup. Furthermore, discoloration of the polyester was hardly noticed even though the column was operated at 250oC. Finally in chapter 7, the validated model is used to find the best suitable internal and feed configurations of the reactive distillation process for unsaturated polyester synthesis. Moreover, multi-product simulations are performed to find the operational parameters for producing two different grades of polyester in the same equipment. Finally, the product transition time during product changeover is determined. The criteria to select the best configuration are minimum volume and energy requirement to produce 100 ktonnes/year polyester. First the best suitable internal for the column is identified and then the best suitable feed configuration is identified. From simulations, we concluded that the configuration which contains the reactive stripping section as a packed bubble column and the reactive rectifying section as a packed column requires minimum volume and energy to produce 100 ktonnes/year polyester. With respect to the feed configuration, we concluded that the feeding of monoesters to the reactive distillation column significantly intensifies the polyester process compared to an anhydrous reactant fed to the column. Moreover, the product transition time in this configuration is also significantly lower compared to the other configurations. In conclusion, a reactive distillation column coupled with a pre-reactor is the most promising alternative to continuously produce unsaturated polyesters. It requires a factor 10 (90%) lower volume, a factor 15 (93%) lower production time and a factor 3 (66%) lower energy as compared to the traditional batch reactor process to produce 100 ktonnes/year of polyester. Hence, the reactive distillation process improves the unsaturated polyester synthesis in all domains of structure, energy and time compared to the traditional batch reactor process coupled with a distillation column

Performance Comparison of Various Textile Composition and Structure Through Full-Wave Electromagnetic Simulation and Measurement

This paper presents the performance of microstrip patch antenna integrated with textile as a substrate, designed for wearable application. Comparative study between cotton fabric as a substrate with copper tape as radiating element and FR-4 as a substrate with E-textile as a radiating element is performed to evaluate the performance of antennas. The antennas integrated in the proposed structures operate at resonant frequency of 5 GHz. Parameters such as fabric thickness and dielectric permittivity are determined through laboratory measurement prior to simulation to ensure accurate analysis and to take into account non-ideal conditions. Preliminary analysis is performed to observe and investigate the characteristics and electromagnetic performance of the antennas when different types of textile are used as the substrate. Antenna prototypes with two different compositions has been fabricated and tested for validation. The fabricated prototypes give good return loss performance which is -27dB at 4.3 GHz resonant frequency for prototype 1 and -22 dB at 4.7 GHz for prototype 2 (e-textile). However, the frequency for Prototype 2 (E-textile) is slightly shifted about 30% to the left due to non-ideal conditions of the textile materials. The ability of both antennas to radiate good signal is also measured. Based on the measurement data, Prototype 2 (E-textile) shows better performance with higher received power compare to Prototype 1 (copper tape) which is -43 dBm within 1 meter range, while - 58 dBm for Prototype 1

Anisotropic structural and optical properties of a-plane (11-20) AlInN nearly-lattice-matched to GaN

We report epitaxial growth of a-plane (11-20) AlInN layers nearly-lattice-matched to GaN. Unlike for c-plane oriented epilayers, a-plane Al_{1-x}In_{x}N cannot be simultaneously lattice-matched to GaN in both in-plane directions. We study the influence of temperature on indium incorporation and obtain nearly-lattice-matched Al_{0.81}In_{0.19}N at a growth temperature of 760^{o}C. We outline a procedure to check in-plane lattice mismatch using high resolution x-ray diffraction, and evaluate the strain and critical thickness. Polarization-resolved optical transmission measurements of the Al_{0.81}In_{0.19}N epilayer reveal a difference in bandgap of ~140 meV between (electric field) E_parallel_c [0001]-axis and E_perpendicular_c conditions with room-temperature photoluminescence peaked at 3.38 eV strongly polarized with E_parallel_c, in good agreement with strain-dependent band-structure calculations

Milk Yield Response of Bypass Protein on Smallholder Dairy Animals

Protein need for small holder dairy animals is very limited. Considering this problem one on-station and one on-farm trails were conducted in 2013 and 2014 in Nepal respectively. In on-station trial (2013) 15 milking buffaloes were randomly assigned to 5 dietary treatments (0, 0.5, 1, 1.5 and 2 kg de-oiled soybean meals/day/buffalo) and in on-farm trial (2014), 20 milking buffaloes were assigned to 0.5 kg de-oiled soybean meal/day/buffalo for two months dry period. From on-station trial, significantly higher (42 %) milk production was observed from 0.5 kg and 1 kg de-oiled soybean meal/day/buffalo feeding groups. From the on-farm trials in village dairy buffaloes 20 percent milk production increment was observed compared with the normal farmer's feeding practices (de-oiled soybean meals unfed condition). It was concluded that, in addition to normal diet, 0.5 to 1 kg de-oiled soybean meal (depending up on the body weight of animal and feeding situation) per day feeding as bypass protein sources could be beneficial during dry period where green fodder is scarce to maintain milk production from dairy animals

Veno-venous extracorporeal membrane oxygenation in pregnancy: does foetal viability matter?

With the increasing use of extracorporeal membrane oxygenation for adults with acute hypoxic respiratory failure, the indications for its use have expanded. We wanted to share the results of a recent case from our institution, of a woman who experienced respiratory failure secondary to hyperemesis gravidarum (HG). HG is a rare complication of pregnancy (0.3% to 2.0% of pregnancies), resulting in uncontrolled or excessive nausea and vomiting with dehydration and weight loss, typically in the first to mid second trimester, and is a diagnosis of exclusion

Engineering provitamin A synthesis pathway with β-carotene metabolism in rice endosperm of a restorer line BR827R

Vitamin A deficiency (VAD) is a serious public health problem in South Asia particularly in Bangladesh. Indica rice as a major staple in the country completely lacks vitamin A or compounds with provitamin A activity after milling. A combination of transgenes has been introduced enabling biosynthesis of provitamin A in the endosperm of a restorer line using biolistic system of transformation. The rice seed-specific glutelin promoter (Gt-1 P) was used to drive the expression of phytone synthase (psy), while lycopene b-cyclase (lcy) and phytoenedesaturase (crtI), fused to the transit peptide sequence of the pea-Rubisco small subunit, were driven by the constitutive cauliflower mosaic virus promoter (CaMV35s P). Transgenic plants were recovered through selection with CaMV35sP driven hph (hygromycinphosphotransferase) gene. Molecular analysis demonstrated stable integration and expression of the transgenes. The variable segregation pattern in T1 generation indicated single to multiple insertions of the transgenes in the genome. This is the first report of the development of a transgenic restorer line with carotenogenic pathway into the endosperm for use of hybrid rice improvement

Synthesis of titanate nanofibers co-sensitized with ZnS and Bi2S3 nanocrystallites and their application on pollutants removal

The synthesis of nanocomposite materials combining titanate nanofibers (TNF) with nanocrystalline ZnS and Bi2S3 semiconductors is described in this work. The TNF were produced via hydrothermal synthesis and sensitized with the semiconductor nanoparticles, through a single-source precursor decomposition method. ZnS and Bi2S3 nanoparticles were successfully grown onto the TNF's surface and Bi2S3-ZnS/TNF nanocomposite materials with different layouts were obtained using either a layer-by-layer or a co-sensitization approach. The samples' photocatalytic performance was first evaluated through the production of the hydroxyl radical using terephthalic acid as probe molecule. All the tested samples show photocatalytic ability for the production of this oxidizing species. Afterwards, the samples were investigated for the removal of methylene blue. The nanocomposite materials with best adsorption ability for the organic dye were the ZnS/TNF and Bi2S3ZnS/TNF. The removal of the methylene blue was systematically studied, and the most promising results were obtained considering a sequential combination of an adsorption-photocatalytic degradation process using the Bi2S3ZnS/TNF powder as a highly adsorbent and photocatalyst material.Comment: 26 pages, 10 figure

GC/MS analysis, free radical scavenging, anticancer and β-glucuronidase inhibitory activities of Trillium govanianum rhizome

The current study aims to investigate the phytochemical constituents, antioxidant, \u3b2-glucuronidase inhibitory and anticancer activities of Trillium govanianum rhizome. Phytochemical screening revealed the presence of steroidal glycosides, saponins, sterols, flavonoids and carbohydrates. GC/MS analyses of n-hexane fraction identified 12 compounds, including 70% unsaturated and 30% saturated fatty acids. Higher free radical scavenging capacity was observed in n-hexane and chloroform fraction compared with the other fractions. Based on IC50 (\u3bcg/mL) values, antiproliferative activity on HeLa cells was observed for chloroform (0.8 \ub1 0.2), ethyl acetate (1.4 \ub1 0.1) and butanol (1.6 \ub1 0.3) fractions by comparison to anticancer drug doxorubicin (0.3 \ub1 0.0). Similarly, all fractions exhibited cytotoxicity on PC-3 cells. Moreover, the methanol extract (IC50: 140.8 \ub1 3.8) and butanol fraction (196.2 \ub1 1.9) exhibited a moderate level of \u3b2-glucuronidase inhibitory activity. These findings may validate the folkloric uses of T. govanianum rhizome in cancer management, and can be a promising candidate as an anticancer agent

Reconfigurable multi-legs robot for pipe inspection: Design and gait movement

1132-1144This paper focuses on studies on reconfigurable multi-legs robotic system. The aim of this paper is to identify and acquire findings on how multi-legs robot can walk, climb vertical pipe and walk along the horizontal pipe after climbing. Three degrees of freedom (3DOF) multi-legs robot is designed and built to replace human involvement either at hazardous pipeline or to check on vertical and horizontal pipes. The robot system is tested to climb the vertical pipe and then move along horizontal pipe for inspection or other purposes. This can reduce the cost and percentage of human risk exposure during inspection on outer pipe. This multi-legs robot has more movement gaits compared to wheeled robot, but in terms of speed, wheeled robot possesses greater advantages. Therefore, this system design has combination of both wheel and multiple legs ensure that the to system has higher stability, more gait movement, and higher speed manoeuvrability. The gaits analysis for the system movement includes angle of the legs to move and selection of certain legs to perform a given operation, either walking, climbing or hanging. The target result is the system able to climb 500 mm height with 85 mm radius pipe. The potential applications for the system are: (i) to move along either on surface or underwater pipe and (ii) to be equipped with ultrasonic sensor to inspect the pipe.</em

The effects of macroscopic inhomogeneities on the magneto transport properties of the electron gas in two dimensions

In experiments on electron transport the macroscopic inhomogeneities in the sample play a fundamental role. In this paper and a subsequent one we introduce and develop a general formalism that captures the principal features of sample inhomogeneities (density gradients, contact misalignments) in the magneto resistance data taken from low mobility heterostructures. We present detailed assessments and experimental investigations of the different regimes of physical interest, notably the regime of semiclassical transport at weak magnetic fields, the plateau-plateau transitions as well as the plateau-insulator transition that generally occurs at much stronger values of the external field only. It is shown that the semiclassical regime at weak fields plays an integral role in the general understanding of the experiments on the quantum Hall regime. The results of this paper clearly indicate that the plateau-plateau transitions, unlike the the plateau-insulator transition, are fundamentally affected by the presence of sample inhomogeneities. We propose a universal scaling result for the magneto resistance parameters. This result facilitates, amongst many other things, a detailed understanding of the difficulties associated with the experimental methodology of H.P. Wei et.al in extracting the quantum critical behavior of the electron gas from the transport measurements conducted on the plateau-plateau transitions.Comment: 20 pages, 9 figure