Tchapda A.H.,EMS Energy Institute |
Pisupati S.,Pennsylvania State University
31st Annual International Pittsburgh Coal Conference: Coal - Energy, Environment and Sustainable Development, PCC 2014 | Year: 2014
Understanding the initial stage of solid fuels conversion is essential to mastering their subsequent chemical and physical transformations with relevance in the design, modeling and improvement of commercial and lab scale solid fuels thermochemical conversion systems. In this regard, coal and biomass chars produced during pyrolysis in an entrained flow reactor in CO2 atmosphere at 1300 °C, 1400 °C, and 1500 °C are characterized using various analytical techniques. The conversion level of the two fuels in the entrained flow reactor is significantly different, varying from 50 to 64% for coal and 87 to 91% for biomass and increasing with the operating temperature. This level of conversion is directly reflected to the particle densities as coal chars display a vertical parabola trend, meaning that chemical and physical transformations are still taking place. Biomass chars on the other hand display an increasing linear trend, which suggests that these chars are approaching their optimum structural changes. This hypothesis is confirmed by the BET surface area, which is very close for all biomass chars. The BET surface area of coal chars increases slightly from 1300 °C to 1400 °C but drops significantly at 1500 °C. A plausible justification of this observation is the coalescence of the pore structure, typical to entrained flow reactor chars. This hypothesis is substantiated by the SEM images of coal char showing visible structure collapse at 1500 °C. Coal chars generated at 1400 °C and 1500 °C have comparable reactivities to CO2 at 800 °C and 900 °C, significantly lower that the reactivity of coal char generated at 1300 °C. A similar trend is found with biomass chars suggesting that the deactivation of reactive sites for heterogeneous reactions is initiated after 1300 °C.
Phase behavior of the CO2-H2O system at temperatures of 273-623 K and pressures of 0.1-200 MPa using Peng-Robinson-Stryjek-Vera equation of state with a modified Wong-Sandler mixing rule: An extension to the CO2-CH4-H2O system
Zhao H.,China University of Petroleum - Beijing |
Lvov S.N.,EMS Energy Institute
Fluid Phase Equilibria | Year: 2016
We modified the binary interaction parameter in Wong-Sandler mixing rule for cubic EOS as a two-parameter linear function of composition. We then incorporated the Non-Random-Two-Liquid excess Gibbs energy model into the modified Wong-Sandler mixing rule to correlate the phase boundaries of the CO2-H2O system through the φ-φ approach by using Peng-Robinson-Stryjek-Vera equation of state. The proposed EOS/Gex model has four adjustable temperature-dependent parameters for polar molecules; and it can be reduced smoothly to the van der Waal one-fluid mixing rule with only one binary interaction parameter for hydrocarbon systems. An excellent result was obtained when compared the modeling results with a large amount of the vapor-liquid equilibria experimental data (more than 1300 experimental data points located in a P-T region of 273-623 K and 0.1-200 MPa) for the CO2-H2O system. The average absolute deviations (AAD%) of modeling results from experimental data (mutual solubilities of CO2 and H2O) are less than 7.5% for both phases. In addition, the proposed model can be easily extended to a multi-component system on condition that the binary interaction parameters of each binary pair in the multi-component system are known. We provided a calculation example for the ternary CO2-CH4-H2O system and found that the modeling result agrees very well with experimental data for this ternary system. © 2016 Elsevier B.V.
At the 2015 United Nations Climate Change Conference in Paris, 195 countries agreed to investigate and adopt methods to reduce emissions of gases including carbon dioxide. Carbon dioxide is released into the atmosphere in two basic ways: naturally, through plant respiration and decomposition, as well as from human activities, such as deforestation, cement production and energy generation from burning fossil fuels. Song plans to use carbon dioxide as a raw material to create fuels, chemicals and materials that are traditionally produced from petroleum. He's a world leader in this approach, known as carbon dioxide conversion or carbon dioxide utilization, and chairs a committee for the International Conference on Carbon Dioxide Utilization (ICCDU). In Song's laboratory on the University Park campus, he has seen results that indicate carbon dioxide conversion could be the best long-term solution to reduce excess carbon dioxide in the atmosphere. Song's primary goal in his research—and the dream that has fueled more than a decade of his carbon dioxide conversion studies—is to develop a sustainable energy cycle for the future. Part of this involves addressing what he sees as an imbalance in the world's natural global carbon cycle. "Normally, carbon dioxide in the air is absorbed by growing plants through photosynthesis, and plants either are eaten by animals or they die. Matter from decomposing animals and plants is used by microbes for respiration, and this process releases carbon back into the atmosphere, which continues the cycle," says Song, who is a distinguished professor of fuel science. However, the rapid consumption of fossil fuels, which releases carbon dioxide, has offset that balance, he says. "Most of the coal, petroleum, natural gas and other fossil fuels we use today for power originated between 280 and 300 million years ago," Song says. "They are burned in a matter of minutes, which means we're using them up millions of times faster than they were formed. There's no way you can be sustainable in this fashion." Song believes the global carbon cycle balance can be restored by changing how we view carbon dioxide. Instead of looking at it as a pollutant or a waste product, Song sees carbon dioxide as a valuable ingredient for creating fuels, industrial chemicals and other materials. The goal of carbon conversion is to break apart carbon dioxide into its parts—carbon and oxygen molecules—and then use those parts as building blocks for different materials. Song's approach requires three main ingredients: carbon dioxide, a chemical catalyst and hydrogen, which can be created when water molecules are chemically separated using renewable energy, such as through the chemical process of electrolysis. Catalysts are chemicals that influence how carbon and hydrogen molecules fit together, and they play a critical role in what products can be created through carbon conversion. They modify the surface properties, such as surface electron density, of the molecules, which allows the molecules to fit together in new and different ways. For example, it could allow for more carbon or hydrogen atoms to be added to the desired molecule, or it could change the types of bonds between carbon and hydrogen atoms. It's similar to modifying the shape of a puzzle piece so that it can connect to a new puzzle. Every change made at the atomic level affects the end product and how that product functions. To develop new, selective catalysts for carbon dioxide conversion, Song has been working with Xiao Jiang, a postdoctoral scholar in the EMS Energy Institute; Wenjia Wang, Ph.D. student in energy and mineral engineering; Nuttakorn Bore, a visiting Ph.D. student from Chulalongkorn University in Thailand; and collaborating researchers at Dalian University of Technology in China. They have created and tested several new catalysts within the past several years, and have seen promising results. "We've known for many years that you can create hydrocarbons such as propane and ethane using carbon dioxide conversion, but through our work with surface modification and the creation of novel catalysts, we're showing that it's possible to selectively produce valuable chemicals and fuels," says Song. By modifying the surface of the molecules in the recipe, Song has been able to transform carbon dioxide directly in a one-step reaction to ethylene and propylene, among other transformations. These two materials belong to a group of molecules known as olefins and are widely used to manufacture many useful materials: bottles for water and soda, wrinkle-resistant fibers, plastic bags, bottles and films in the food industry and machine parts used in medical devices. The possibilities for materials that can be created through carbon dioxide conversion are seemingly endless, depending on the catalyst used. Iron combined with cobalt is among the catalysts Song's group has used to produce olefins. He has also designed a different catalyst, copper coupled with palladium, to convert carbon dioxide directly in a one-step reaction to methanol, which is widely used in chemicals and fuels. But Song isn't just making new materials—he's also focusing on optimizing the different carbon conversion processes. Additionally, he's investigating the feasibility of incorporating renewable energy sources to provide the extra energy needed for the conversion. "Some of the criticism in the past has been that the carbon dioxide conversion process requires extra energy for hydrogen production, which uses natural gas or coal today, so there's a net loss of energy and the process wouldn't actually be sustainable. But we will use renewable energy for hydrogen production, and in fact researchers at Penn State and elsewhere are investigating the use of renewable energies like solar or wind to generate hydrogen, which can sustain the process," he says. He has been able to increase the efficiency of some of his carbon dioxide conversion processes by 300 percent over the conventional state-of-the-art processes in the past few years, by adjusting catalysts and tweaking his process. Song hopes that the development of new catalysts and the optimization of his carbon dioxide conversion processes will underscore the importance and reliability of carbon dioxide conversion as a method of reducing greenhouse gas emissions and decreasing our dependence on fossil resources. "It has been my dream to develop a sustainable green energy cycle that communities around the world can use, and I think that carbon dioxide conversion provides a promising path forward. It really is a sustainable way to build a new energy cycle," he says. Explore further: Study finds that soil carbon may not be as stable as previously thought
Hall D.M.,EMS Energy Institute |
Beck J.R.,EMS Energy Institute |
Lvov S.N.,EMS Energy Institute |
Lvov S.N.,Pennsylvania State University
Electrochemistry Communications | Year: 2015
The hydrogen reaction in concentrated HCl(aq) solutions is a key reaction for the CuCl(aq)/HCl(aq) electrolytic cell. Here, electrochemical impedance spectroscopy (EIS) and linear sweep voltammetry (LSV) were used to obtain new data for the hydrogen reaction on platinum submerged in highly concentrated acidic solutions at 25 °C and 0.1 MPa. LSV and EIS data were collected for Pt in 0.5 mol/L H2SO4(aq), 1 mol/L HCl(aq) and 7.71 mol/L HCl(aq) solutions. It was found that exchange current density (j0) values varied between 1 and 2 mA/cm2. An equivalent circuit model was used to obtain comparable j0 and limiting current density values from EIS data relative to values obtained with LSV data. It was found that as the concentration of acid increased, a noticeable decrease in the performance was observed. © 2015 Elsevier B.V. All rights reserved.
Liu M.,Dalian University of Technology |
Jia S.,Dalian University of Technology |
Jia S.,Dalian National Laboratory for Clean Energy |
Gong Y.,Dalian University of Technology |
And 4 more authors.
Industrial and Engineering Chemistry Research | Year: 2013
Sulfonated sucrose-derived carbon, glucose-derived carbon, and nut shell activated carbon (NSAC) catalysts were prepared and characterized by Fourier transform infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS). FT-IR and XPS spectra showed that -SO3H groups could be introduced into the carbon precursors after the sulfonation treatment. Higher concentration of -SO3H groups in the sulfonated sucrose-carbon and glucose-carbon most likely accounts for their higher activities compared to sulfonated NSAC. Hydrolysis of microcrystalline cellulose was examined in a common ionic liquid, 1-butyl-3-methylimidazolium chloride ([BMIM]Cl), with the sulfonated carbon catalysts. Maximum yields of glucose (59%) and total products (80%, defined as the sum of glucose, cellobiose, and 5-hydroxymethylfurfural) could be obtained with sulfonated sucrose-carbon at 120 C for 4 h. With a regeneration procedure, the catalyst could be reused. © 2013 American Chemical Society.