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Worldwide use of hydrofluorocarbons (HFCs) is currently being regulated and phased out because of high global warming potentials (GWPs). Separation techniques for recycling refrigerants are needed so that HFCs can be dealt with responsibly. Many HFCs currently in use are azeotropic or near-azeotropic refrigerant blends and must be separated so that the components can be recycled and repurposed effectively. One such refrigerant is R

HighlightsThis study determined adsorption and desorption isotherms of long-grain hybrid rough rice in chilled environments.Parameters of the sorption models were evaluated by fitting experimental data in a thin layer drying equation.The moisture diffusivity and activation energy values of rough rice subjected to chilled environments were determined.The finite element method was used to simulate the heat and mass transfer of long-grain hybrid rice at low temperatures. Abstract. While chilling aeration technology for grains has found use in other countries, application in the U.S. for rice has not yet been widely adapted by the industry. The aim of this study was to determine the moisture sorption behavior of rough rice in chilled environments. Such data is vital for automated grain conditioning monitoring and control of aeration systems at cool ambient conditions. Adsorption and desorption isotherms of hybrid long-grain rough rice (XL745) subjected to temperature environments which are typical in U.S. storage conditions (5°C to 15°C) were measured. A dynamic vapor sorption analyzer, the IGAsorp, which consists of an ultrasensitive microbalance within a controlled environment was used to accurately measure water sorption in rice. Changes in sample weight were continuously monitored across a range of equilibrium relative humidity (10% to 70%) until a steady-state mass was attained. Nonlinear regression analysis was used to estimate empirical constants of five models used for describing grain sorption isotherms. The appropriateness of each model in describing the equilibrium data was evaluated to minimize the root mean square error (RMSE). The modified Chung-Pfost equation best described the experimental data with RMSEs of 0.557 and 0.912 for adsorption and desorption data, respectively. The equilibrium moisture content (EMC) of rice measured at 5°C with 10% relative humidity (RH) was 12.5% (dry basis), which was higher than the EMC value predicted from other studies by extrapolation at 30°C (9.1% d.b.). All five prediction models (modified Chung-Pfost, modified Henderson, modified Oswin, modified Halsey, and GAB) were in good agreement for experimental data at moderate temperature conditions (e.g., at 30°C). The results indicated that it is more accurate to use newly developed constants for EMC models of rice in chilled environments. A three-dimensional ellipsoid shape was used to describe rough rice geometry. Mathematical models were developed to predict the moisture and temperature distribution during the drying processes at 5°C and 15°C. Models were solved by the finite element method using Comsol Multiphysics® simulation program. Increasing the drying temperature from 5°C to 15°C increased the effective moisture diffusivity from 9.0×10-13 to 1.1×10-12 m2/s. The drying activation energy value was 25.1 kJ/mol in the chilled environments investigated. Keywords: Activation energy, Chilled environment, Equilibrium moisture content, Mathematical modeling, Moisture diffusivity, Rough rice.

Electric vehicles (EVs) are an increasingly popular option to decrease global greenhouse emissions in the transportation sector. The largest limiting factor is their range, significantly decreased by the cooling load required. In conjunction with the shift to incorporating low-Global Warming Potential (GWP) refrigerants in cooling systems, it is critical to reexamine the design of traditional air conditioning (AC) systems. To this end, a model of a cooling system for an EV was created, while incorporating an ultrahigh-speed miniature centrifugal compressor, allowing for the performance comparison of multiple refrigerants. From these simulations, a centrifugal compression system using HFC-134a provided sufficient cooling capacity for the modeled vehicle (13.07 kW) with lower input power requirements (2.05 kW) than a commercial EV AC system. However, this requires improved heat exchanger efficiencies. A straightforward system design may be attainable with lower operating pressures utilizing the low-GWP HFO-1336mzz(Z) while achieving a nearly equivalent cooling capacity (12.39 kW) at reduced power requirements (1.86 kW). Performance and safety tradeoffs were examined for a variety of refrigerants and azeotropic mixtures. The use of azeotropic refrigerants increased the cooling capacity and energy efficiency compared with the individual components, but with the tradeoff of higher pressure and compressor exit temperatures. Overall, this effort provides specified conditions for EVs while being among the first to demonstrate the potential of low-GWP and low-Ozone Depletion Potential refrigerants in AC systems utilizing ultrahigh-speed centrifugal compressors.

Hydrofluorocarbons (HFCs) have been used extensively as refrigerants over the past four decades; however, HFCs are currently being phased out due to large global warming potentials. As the next generation of hydrofluoroolefin refrigerants are phased in, action must be taken to responsibly and sustainably deal with the HFCs currently in circulation. Ideally, unused HFCs can be reclaimed and recycled; however, many HFCs in circulation are azeotropic or near-azeotropic mixtures and must be separated before recycling. Previously, pure gas isotherm data were presented for both HFC-125 (pentafluoroethane) and HFC-32 (difluoromethane) with zeolite 5A, and it was concluded that this zeolite could separate refrigerant R-410A (50/50 wt % HFC-125/HFC-32). To further investigate the separation capabilities of zeolite 5A, binary adsorption was measured for the same system using the Integral Mass Balance method. Zeolite 5A showed a selectivity of 9.6-10.9 for HFC-32 over the composition range of 25-75 mol % HFC-125. Adsorbed phase activity coefficients were calculated from binary adsorption data. The Spreading Pressure Dependent, modified nonrandom two-liquid, and modified Wilson activity coefficient models were fit to experimental data, and the resulting activity coefficient models were used in Real Adsorbed Solution Theory (RAST). RAST binary adsorption model predictions were compared with Ideal Adsorbed Solution Theory (IAST) predictions made using the Dual-Site Langmuir, Tóth, and Jensen and Seaton pure gas isotherm models. Both IAST and RAST yielded qualitatively accurate predictions; however, quantitative accuracy was greatly improved using RAST models. Diffusion behavior of HFC-125 and HFC-32 was also investigated by fitting the isothermal Fickian diffusion model to kinetic data. Molecular-level phenomena were investigated to understand both thermodynamic and kinetic behaviors.

Growing concerns about the global warming potential of hydrofluorocarbons (HFCs) has led to increasing interest in developing technologies to effectively recover and recycle these refrigerants. Ion...

Conventional strong liquid acids such as H2SO4 and HF are used for the majority of current commercial isobutane alkylation process to produce motor fuel alkylates, but these acids can have signific...

Hydrofluoroolefins (HFOs) are currently being developed to replace hydrofluorocarbons (HFCs) with high global warming potential (GWP) in air-conditioning and refrigeration systems. The development ...

Natural gas is one of the critical fossil fuel sources in the world to fulfill current energy demand in the global market. Methane is the primary component in natural gas and dependent on the sourc...

The solubility and diffusivity of bromodifluoromethane (CHF2Br, Halon-1201) were measured in three ionic liquids (ILs), [C2C1im][Tf2N], [C4C1im][BF4], and [C4C1im][PF6], using an intelligent gravim...

The demand for lithium-ion batteries (LiBs) is significantly increasing leading to a shortage in supply for critical metals, such as lithium and cobalt. Recycling LiCoO2 cathodes can provide a seco...

To support the phaseout of high global warming potential working fluids commonly used in air-conditioning and refrigeration systems, detailed knowledge about the thermodynamic and transport propert...

Introduction. It is estimated that 50% of vaccines produced annu- ally are wasted because effectivity is dependent on protein structure and heat exposure disrupts the intermolecular interactions that maintain this structure. Since 90% of vaccines require a temperature- controlled supply chain, it is necessary to create a cold chain system to minimize vaccine waste. We have developed a more sustainable technology via the adsorption of Invasion Plasmid Antigen D (IpaD) onto mesoporous silica gels, improving the thermal stability of pro- tein-based therapeutics. Methods.xThe solution depletion method using UV-Vis was uti- lized to study the adsorption of IpaD onto silica gels. The silica-IpaD complex is heated above the denaturing temperature of the protein and then the IpaD is removed using N,N-Dimethyldodecylamine N-oxide (LDAO) and their secondary structure is tested using cir- cular dichroism (CD). Results. Pore diameter, pore volume and surface area were charac- terized for seven different silica gels. Silica gels designated as 6389, 6378, and 6375 had an adsorption percentage above 95% at pore volumes of 2.2, 2.8 and 3.8 cm3 mg-1, respectively. CD analyses con- firmed that the adsorbed IpaD after the heat treatment displayed a similar “W” shape CD signal as the native IpaD, indicating the con- servation of α-helices. In contrast, the unprotected IpaD after being exposed to high temperature shows a flat CD signal, demonstrating the loss of secondary structure. Conclusion. We have successfully increased the thermo-tolerance for IpaD using mesoporous silica and continue to further optimize mesoporous silica’s physiochemical properties to improve adsorption and desorption yields.

The Bayer process holds an exclusive status for alumina extraction, but a massive amount of caustic “red mud” waste is generated. In this work, three oxalate reagents: potassium hydrogen oxalate (KHC2O4), potassium tetraoxalate (KHC2O4·H2C2O4), and oxalic acid (H2C2O4) were investigated for the Al and Fe extraction process from NIST SRM 600 – Australian Darling range bauxite ore. More than 90% of Al and Fe was extracted into the aqueous phase in less than 2 h with 0.50 M C2O42- for all three reagents. The Fe and Al can be selectively precipitated by hydrolyzing the aqueous phase. By acidifying the Al and Fe free filtrate, 80% of the C2O42- can be precipitated as KHC2O4·H2C2O4. Greater than 90% of the aqueous acid can also be recycled using a cation exchange resin. The proposed closed-loop process is an energy-efficient, cost-effective, environmentally-friendly route for extracting Al and Fe from bauxite ore.

The Bayer process holds an exclusive status for alumina extraction, but a massive amount of caustic “red mud” waste is generated. In this work, three oxalate reagents: potassium hydrogen oxalate (KHCO), potassium tetraoxalate (KHCO·HCO), and oxalic acid (HCO) were investigated for the Al and Fe extraction process from NIST SRM 600 – Australian Darling range bauxite ore. More than 90% of Al and Fe was extracted into the aqueous phase in less than 2 h with 0.50 M CO for all three reagents. The Fe and Al can be selectively precipitated by hydrolyzing the aqueous phase. By acidifying the Al and Fe free filtrate, 80% of the CO can be precipitated as KHCO·HCO. Greater than 90% of the aqueous acid can also be recycled using a cation exchange resin. The proposed closed-loop process is an energy-efficient, cost-effective, environmentally-friendly route for extracting Al and Fe from bauxite ore.

Combustible metal dust explosions continue to present a significant threat to metal handling and refining industries. Addition of noncombustible inert material to combustible dust mixtures, through...

Energy-efficient metal recovery and separation processes from a mixture of valuable metals are vital to the metallurgy and recycling industries. Oxalate has been identified as a sustainable reagent...

Binary liquid–liquid equilibria (LLE) for mixtures of dihydroxy alcohols and three imidazolium-based ionic liquids (ILs) were measured. The dihydroxy alcohols were 1,3-propanediol, 1,4-butanediol, ...

Solubility and diffusivity measurements of chlorodifluoromethane (HCFC-22) in four ionic liquids (ILs)—[emim][Tf2N], [bmim][BF4], [bmim][PF6], and [emim][TFES]—were conducted using an IGA gravimetr...

The high-pressure vapor–liquid equilibrium for the binary systems of carbon dioxide (CO2) and a series of 1-alkyl-1-methyl pyrrolidinium bis(trifluoromethylsulfonyl)imide ionic liquids ([CnC1pyr][N...

Alkylation of short-chain olefins with isobutane catalyzed by sulfuric acid is a common process for reformulated fuel. Here, pilot-plant and commercial C3 and C4 alkylates were examined for sulfur content, acid content, and emulsion formation. Even though the thermodynamic solubility of sulfuric acid in alkylate is negligible at process conditions, the C4 alkylate samples contained ∼20 ppm sulfur mostly from very dilute emulsions with ∼3 μm droplets of sulfuric acid and alkyl sulfates that were stable even after 6 months. The sulfur content and droplet size increased for propylene alkylation. However, no detectable emulsion or sulfur content could be generated synthetically by intense mixing with either 2,2,4-trimethylpentane (a model alkylate) or a treated pilot-plant alkylate with concentrated or spent sulfuric acid over the course of several hours. Thus, the alkylate sulfur content is most likely created during the acid-catalyzed chemical reaction steps and not from high-shear mixing.

The viscosities of mixtures of pyrrolidinium-based ionic liquids saturated with compressed CO2 were measured using a high-pressure viscometer at three different temperatures (298.15, 318.15, and 33...

The first vapor liquid equilibrium (VLE) measurements for the binary systems of ammonia (NH3) and three imidazolium-based ionic liquids (ILs) have been successfully measured using a gravimetric microbalance. ILs 1-butyl-3-methylimidazolium hexafluorophosphate ([C4C1im][PF6]), 1-butyl-3-methylimidazolium tetrafluoroborate ([C4C1im][BF4]), and 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([C2C1im][NTf2]) were measured at temperatures of 283.15, 298.15, 323.15, and 348.15 K and at pressures up to 0.7 MPa using the new Hiden XEMIS gravimetric microbalance. The VLE data were correlated using the Peng–Robinson equation of state and the Non-Random Two Liquid (NRTL) activity coefficient models. Both models are in excellent agreement with the experimental data. The Fickian diffusivities of NH3 in imidazolium-based ILs were obtained fitting experimental concentration to the one-dimensional (1D) mass diffusion equation, and found to be about 3 to 5 times lower than the diffusion of NH3 in water (H2O...

Acid catalysts derived from a well-known reaction of 1-methylimidazole and chlorosulfonic acid system are considered very important, but sufficient details are lacking on their structure information. We studied and report the structural characterization of products from a reaction of 1-methylimidazole and chlorosulfonic acid. Our results from crystallography, nuclear magnetic resonance spectroscopy (NMR), elemental analysis, thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC) indicate the formation of a unique reaction mixture of zwitterion-type salt [C1im-SO3] and ionic liquid [C1im-SO3H]Cl at a 7:3 ratio instead of only ionic liquids as proposed by others.

Measurements of in situ atmospheric water absorption and desorption in ionic liquids (ILs) (1-ethyl-3-methylimidazolium tetrafluoroborate [C2C1im][BF4], 1-butyl-3-methylimidazolium acetate [C4C1im][OAc], and 1-butyl-3-methylimidazolium chloride [C4C1im][Cl]) were made using a gravimetric microbalance at temperatures ranging from 283.15 to 315.15 K and relative humidity (RH) 0–70% at 101 kPa. Solubility data were well correlated using the nonrandom two-liquid (NRTL) activity model, and time dependent concentration data were used to determine the binary diffusion coefficients using one- and two-dimensional transport models of water in the IL–water systems. The solubility of water was highest in [C4C1im][OAc] (77.5 mol %), followed by [C4C1im][Cl] (68.6 mol %), and [C2C1im][BF4] (19.5 mol %) at equivalent conditions (303.15 K and 25.00% RH). The diffusion coefficients in order of increasing relative humidity ranged from 1.3 × 10–10 to 2.8 × 10–11 m2/s for [C2C1im][BF4], from 8.8 × 10–12 to 3.9 × 10–11 m2/s f...

Simulation software has experienced growing interest in chemical engineering curriculums for its usage in commercial engineering practices. This article describes the ASPEN Plus® version 10 (V10) simulations and a student teach students approach to integrate ASPEN in the chemical engineering curriculum at the University of Kansas (KU). Videos, handouts, and lectures created by the first author, an undergraduate senior, effectively teaches ASPEN to other chemical engineering students and enhances the learning experience of the classroom.

Green and sustainable recycling of lithium-ion batteries is an important problem that requires immediate attention to meet the rapid growth in critical materials demand for the electric vehicle (EV) market. In this work, a holistic study is presented to develop a closed-loop Li and Co metal recovery and separation process for LiCoO2 electrode materials using oxalate chemistry. More than 97% of Co and Li extraction and almost complete separation between these metals were found in the digestion using oxalic acid at a concentration of 0.46 M, a solid-to-liquid ratio of 15 g/L, agitator speed of 600 rpm, and a temperature of 100 °C. An optimum pH of about 2.5 was identified to achieve efficient extraction and separation between Li and Co. A novel oxalic acid regeneration process using ion-exchange resins is proposed to recover oxalate, reduce waste production, and lower the overall cost of the process. The experimental results are supported with a chemical speciation study and a shrinking core model based kinetic study to develop a deeper understanding of the interfacial processes.

Combustible dust explosions continue to present a significant hazard toward industries processing, storing, or pneumatically conveying metal dusts. Recent experimental investigations performed in a Siwek 20 L sphere combustion chamber characterized the explosion severity as a function of variable aluminum particle morphology (spherical, irregular granular, and flake aluminum powder). Contained ignition of suspended particulates with increasing surface irregularity exhibited a distinct rise in deflagration severity –fuel reactivity was modeled as a means of predicting hazard potential for distinct metal dust processing methods. Applying the shrinking particle theory with reaction and species diffusion limitations, previously reported pressure evolution outcomes were verified through development and implementation of closed-vessel mathematical modeling based on derivation of fundamental mass and thermal balance equations. Geometric equivalence methods were employed to estimate particle diameter for irregular dust morphologies. The consequence prediction models are in good agreement with experimental data sets; all relevant deviations are examined in detail.

Approximately half of all vaccines produced annually are wasted because effectivity is dependent on protein structure and heat exposure disrupts the intermolecular interactions needed to maintain the structure. Thus, most vaccines require a temperature-controlled supply chain to minimize waste. A more sustainable technology was developed via the adsorption of invasion plasmid antigen D (IpaD) onto mesoporous silica, improving the thermal stability of this protein-based therapeutic. Seven silicas were characterized to determine the effects of pore diameter, pore volume, and surface area on protein adsorption. The silica-IpaD complex was then heated above the IpaD denaturing temperature and N,N-dimethyldodecylamine N-oxide was used to remove IpaD from the silica. Circular dichroism confirmed that the adsorbed IpaD after the heat treatment maintained a native secondary structure rich in α-helix content. In contrast, the unprotected IpaD after heat treatment lost its secondary structure. Isotherms using Langmuir, Freundlich, and Temkin models demonstrated that the adsorption of IpaD onto silicas is best fit by the Langmuir model. If pores are less than 15 nm, adsorption is negligible. If the pores are between 15 and 25 nm, then monolayer coverage is achieved and IpaD is protected from thermal denaturing. If pores are larger than 25 nm, the adsorption is a multilayer coverage and it is easier to remove the protein from the silica because of a less-developed hydrogen bond network. This case study provides strong evidence that IpaD is thermally stabilized via adsorption on mesoporous silica with the proper range of pore sizes.

Aspen Plus® simulations using the Peng-Robinson (PR-EOS) and the COSMO-SAC models were performed to study absorption power cycles (APCs) using mixtures of R-134a with two ionic liquids, [C2C1im][Tf2N] or [C6C1im][Tf2N], and compared against an R-134a organic Rankine cycle (ORC) operating under similar conditions. The PR-EOS results were in agreement with calculations from a PR model fitted to the R-134a+IL experimental phase equilibrium data. The APCs have similar efficiencies and outperform the ORC by 3-46%, with the largest differences observed when operating with lower grade (lower TH) heating sources, lower quality cooling (higher TL) and lower subcooling in the pump inlet stream. The PR-EOS and the COSMO-SAC results follow similar trends, but numerical discrepancies are observed in the cycle efficiencies and stream flow rates and compositions due to differences in solubilities and enthalpy changes between both models, suggesting that improvements are needed to increase the accuracy of COSMO-SAC for these systems.

Introduction It is estimated that 50% of vaccines produced annually are wasted because effectivity is dependent on protein structure and heat exposure disrupts the intermolecular interactions that maintain this structure. Since 90% of vaccines require a temperature-controlled supply chain, it is necessary to create a cold chain system to minimize vaccine waste. We have developed a more sustainable technology via the adsorption of Invasion Plasmid Antigen D (IpaD) onto mesoporous silica gels, improving the thermal stability of protein-based therapeutics. Methods The solution depletion method using UV-Vis was utilized to study the adsorption of IpaD onto silica gels. The silica-IpaD complex is heated above the denaturing temperature of the protein and then the IpaD is removed using N,N-Dimethyldodecylamine N-oxide (LDAO) and their secondary structure is tested using circular dichroism (CD). Results Pore diameter, pore volume and surface area were characterized for seven different silica gels. Silica gels designated as 6389, 6378, and 6375 had an adsorption percentage above 95% at pore volumes of 2.2, 2.8 and 3.8 cm3 mg-1, respectively. CD analyses confirmed that the adsorbed IpaD after the heat treatment displayed a similar “W” shape CD signal as the native IpaD, indicating the conservation of α-helices. In contrast, the unprotected IpaD after being exposed to high temperature shows a flat CD signal, demonstrating the loss of secondary structure. Conclusion We have successfully increased the thermo-tolerance for IpaD using mesoporous silica and continue to further optimize mesoporous silica’s physiochemical properties to improve adsorption and desorption yields.

A Unit Operations Laboratory (UOL) is fundamental to undergraduate chemical engineering education. This article discusses a new course structure for the University of Kansas UOL and details for three new experiments covering the fundamentals of vapor-liquid equilibrium, fluid mechanics, and kinetics. Students apply knowledge from these courses as well as learn about safety, statistical data analysis, ASPEN Plus™ modeling, oral communication, report writing, referencing and comparing results with literature, leadership, ethics, and (most importantly) time-management.

Twenty years ago, research involving ionic liquids was a minor field of interest, and only a few chemists and even fewer engineers were interested in salts with melting points near room temperature. In April 2000, the first NATO advanced research workshop on ionic liquids was held in Heraklion, Crete. The conference was the first international meeting devoted to ionic liquids and attracted most of the active researchers at that time. Following that meeting, activity in the field began to flourish and the first books and international conferences devoted to ionic liquids began to appear. By the end of 2018, more than 80,000 scientific papers had been published, and 17,000 patents were applied for in the field of ionic liquids! This book provides an overview of the current and emerging industrial applications of ionic liquids covering the core processes and products, the practical implementation and technical challenges involved, and the potential future directions for research and development. The individual chapters were written by leading scientists in the field from industry and academia to address specific processes and products that are or will be soon commercialized. Examples include the use of a chloroaluminate ionic liquid as a next-generation alkylation catalyst to a new class of capillary gas chromatography (GC) columns with stationary phases based on ionic liquids. Over the past twenty years, there has been a growing realization that ionic liquids have moved from being mere academic curiosities to having genuine applications in fields as wide-ranging as advanced materials, biotechnology, catalysis, pharmaceuticals, renewable fuels, and sustainable energy. There are many optimistic indications that ionic liquids are on their way to becoming a commercial success story. This first book on “Commercial Applications of Ionic Liquids” provides over 50 applications that are either at the pilot scale or have been commercialized, which indicates that an exciting new chapter in the field of ionic liquids is about to begin!

Metal dust deflagrations continue to pose a critical threat toward safety in the metal processing industry. This paper begins with introduction of the fundamental requirements for an explosion and reviews the modern developments in explosion prevention techniques, while describing the challenges confronted with applying these techniques to nonstandard metal dust applications. Variability in several intrinsic properties associated with bulk solids conveyance (such as propagation behavior, degree of turbulence, particle size, and moisture content) contributes to metallic fuels having the increased potential to act as highly reactive explosion hazards. Upon ignition in a contained enclosure volume and propagation to interconnected vessels, metal dusts exhibit augmented explosion severity and sensitivity because of their large heats of combustion, higher burning temperatures, radiative heat transfer effects, and abnormally reactive interactions with water. These characteristics are specific to metal dust fuel...