Development of An Economically Viable H2O2-based, Liquid-Phase Ethylene Oxide Technology: Reactor Engineering and Catalyst Development Studies

Ethylene Oxide (C2H4O, abbreviated as EO), a high volume chemical intermediate is used as a raw material for a variety of consumer products, such as plastic bottles, anti-freeze, sports gear, detergents and paints. In 2009, approximately 19 million metric tons of EO were produced and its demand is projected to grow at an average rate of 3-4% per year over the next decade. Currently, EO is manufactured by the silver catalyzed ethylene epoxidation process which is highly energy intensive and wasteful because much of the ethylene (feedstock) and EO (product) burns to form carbon dioxide, a greenhouse gas. Worldwide, commercial production of EO releases 3.4 million metric tonnes of CO2 each year making it the second largest emitter of CO2 among all chemical processes. Furthermore, loss of ethylene feedstock to burning represents a loss of $1.1 billion per year worldwide. In this dissertation, an alternative liquid phase ethylene epoxidation technology (henceforth referred to as CEBC EO process) has been demonstrated with both homogeneous Re-based and heterogeneous Ce- and W-based catalysts. In this process, the ethylene gas is compressed under pressure (50 bars) and dissolved in a liquid reaction medium containing the oxidant 50 wt% H2O2/H2O, promoter pyridine N-oxide and catalyst (methyl trioxorhenium or W-KIT-6 or W-KIT-5). The ensuing catalytic reaction produces EO with near complete selectivity with no CO2 detected in either the liquid or gas phases. Methanol is employed as a co-solvent to enhance the ethylene solubility in the liquid phase. At the operating conditions (P = 50 bars, T = 20-40 °C), the volumetric expansion studies reveal that the liquid reaction phase (methanol+H2O2/H2O) is expanded by up to 12% by compressed ethylene. The corresponding ethylene solubility is 22 mole %, converting ethylene from being the limiting reactant in the liquid phase at ambient pressure to an excess reactant at the higher pressures. Fundamental engineering studies (volumetric expansion, mass transfer and conversion studies) essential for achieving pressure-intensification established the optimum agitation speed for Re-catalyzed ethylene epoxidation to be 1200 rpm. Operating at conditions that enhanced the ethylene solubility and eliminated interphase mass transfer limitations maximized the EO productivity (1.61-4.97 g EO/h/g metal) on MTO catalyst, rendering it comparable to the conventional silver-catalyzed process. Further, intrinsic kinetic parameters, estimated from fixed time semi-batch reactor studies, disclosed the moderate activation energy (57±2 kJ/mol). Based on a plant-scale simulation of the CEBC EO process using Aspen HYSYS®, preliminary economic and environmental assessments of the process are performed, both of which are benchmarked against the conventional silver-catalyzed ethylene epoxidation process. The capital costs for both processes lie within prediction uncertainty. The EO production cost for the conventional process is estimated to be 71.6 ¢/lb EO. The CEBC process has the potential to be competitive with the conventional process if the MTO catalyst remains active, selective and stable for at least six months at a leaching rate of approximately 0.11 lb MTO/h (or 5 ppm Re in the reactor effluent). Comparative cradle-to-gate life cycle assessments (LCA) reveal that the overall environmental impacts on air quality, water quality and greenhouse gas emissions are similar for both processes given the uncertainties involved in such predictions. The LCA results implicate sources outside the EO production plants as the major contributors to potential environmental impacts: fossil fuel-based energy required for natural gas processing (used for producing ethylene, hydrogen and methanol) in both processes and to the significant requirements of coal-based electrical power for compressing large volumes of recycled ethylene and other gases in the conventional process. These results of the economic analysis prompted the evaluation of alternative catalysts that are inexpensive and exhibit the best performance metrics (high activity, near complete selectivity towards desired product and high stability). These evaluation studies identified tungsten and cerium based catalysts as possible alternatives. W-based catalysts formed EO with near complete selectivity and recycle studies established catalyst durability. Further, the EO productivity with these catalysts (0.3-3.2 g EO/h/g W) is of the same order of magnitude as the Re-based and Ag-based catalysts

Reconceptualizing the Language of Ideas: ‘A Disciplinary Perspective’

It is a widespread view that ‘academic language’ is the most significant dimension of language. This aspect of language is widely used for academic purposes that contrast with the conversational language spoken outside of the classrooms. The ultimate focus on the linguistic features of academic syllabi overlooks the role everyday forms of conversational language play in academic work and how learners of marginalized backgrounds are capable of using their existing linguistic resources to navigate tasks within the classrooms. The paper intends to shift the focus from academic texts to the language of ideas used to navigate in disciplinary works, such as how the ideas and content can be expressed in various ways, and the linguistic resources learners of unprivileged backgrounds use to engage in the tasks

Modeling of the Phase behavior of light (C2 & C3) olefins in liquid phase epoxidation systems and experimental determination of gas/liquid mass transfer coefficients

Conventional technologies for the selective epoxidation of olefins such as ethylene and propylene to form their corresponding epoxides are either non selective and/or produce much waste. A novel biphasic process for the epoxidation of olefins has been developed by the researchers at Center for Environmentally Beneficial Catalysis (CEBC), employing environmentally benign substances (catalyst methyltrioxorhenium, oxidant aqueous H2O2) dissolved in a suitable solvent (determined to be methanol). HYSYS® software was used to study the phase behavior and generate quantitative data on the solubility of gaseous olefins in the liquid phase which aided in the optimization of the reaction conditions. A detailed stirred tank reactor model was developed to estimate the gas/liquid mass transfer coefficient which was determined to be 0.14 sec-1 at 1000 rpm which ensured operation outside the diffusion limited region. Inerts such as N2 and CO2 can be used to mitigate the flammability envelope of these highly flammable gases

Automated Essay Evaluation Using Natural Language Processing and Machine Learning

The goal of automated essay evaluation is to assign grades to essays and provide feedback using computers. Automated evaluation is increasingly being used in classrooms and online exams. The aim of this project is to develop machine learning models for performing automated essay scoring and evaluate their performance. In this research, a publicly available essay data set was used to train and test the efficacy of the adopted techniques. Natural language processing techniques were used to extract features from essays in the dataset. Three different existing machine learning algorithms were used on the chosen dataset. The data was divided into two parts: training data and testing data. The inter-rater reliability and performance of these models were compared with each other and with human graders. Among the three machine learning models, the random forest performed the best in terms of agreement with human scorers as it achieved the lowest mean absolute error for the test dataset

Barriers for immunization against HPV in developing countries (India)

Cervical cancer is one of the most common cancers in women. Incidence and mortality rates of cervical cancer are high in less developed and developing countries. In some countries, the acceptance of the HPV vaccine to prevent cervical cancer is low. Previous studies revealed that lack of awareness, income, and education were major barriers for accepting the HPV vaccine. Apart from the above-mentioned barriers, some socio-cultural barriers for accepting the HPV vaccine exist in less developed and developing countries. This study surveyed 250 women in India of age groups 18 years and above. The sample population for the study was chosen from a clinic\u27s database. Survey questionnaires and informed consents were mailed to the participants. The results of this study exposed various concerns of women like lack of knowledge about vaccine, fear about the impact on their relationships, and embarrassment to talk about the vaccine