Relative Volatility Research Articles

Quantum chemistry of solvent selectivity and economic, exergy and environment analysis of extractive distillation process for separating binary azeotropic mixture

BackgroundAfter ammoniation of propacetamol hydrochloride, the liquor contains an azeotropic mixture of acetone and diethylamine. The mixture must be separated to reuse the solvent and the raw material. However, the separation of acetone and diethylamine is difficult because the boiling point difference is only 0.6°C. MethodsIn this study, the mechanism of separating azeotropes was studied by quantum chemical calculations of the σ-profiles, interaction energy and molecular conformation. The vapor-liquid equilibrium data were supplemented by experimental analysis of the vapor-liquid equilibrium for cyclohexanol and diethylamine. The relative volatility of the light and heavy components of the azeotrope was investigated after adding the solvent. Sequential iteration method was used to optimize the extractive distillation process. The parameters in process such as the feeding position, number of stages and the amount of solvent are optimized, and the minimum total annual cost is obtained. Significant findingsThe results showed that the two-column feed preheating extractive distillation process was the lowest. The results showed that the two-column feed preheating extractive distillation process afforded the lowest total annual cost. Thermodynamic and environmental analyses showed that the two-column feed preheating extractive distillation process afforded good energy-saving, with minimal environmental impact. This study is significant for implementing the extractive distillation process for azeotrope separation and the sustainable development of acetone and diethylamine products.

Effect of phosphorus P-π bonding on the volumetric properties and vapor-liquid equilibrium of phosphorus trichloride-benzene liquid mixtures

New density and vapor–liquid equilibrium data of PCl3-benzene binary system at atmospheric pressure (99.7–101.3 kPa) were carefully measured to provide crucial information for their industrial reaction and separation. The experimental mixture densities show excellent linear dependence on both solution composition and temperature and a generalized empirical correlation is proposed with an average relative deviation of 0.13%. The specific attractive P-π interaction between the phosphorus atom of PCl3 and the π cloud of benzene seems to be quite strong in solution, leading to large negative excess volumes. But the π-π antibonding effect from benzene dimers are predominant in PCl3 highly dilute solution, where positive excess volume and excess partial molar volumes of PCl3 were observed. Experimental bubble points of the binary mixture were corrected to those under 101.325 kPa. Two distinctive methods of coexistence equation and activity coefficient models of Wilson and NRTL equations were applied to model the VLE data, and they yielded very consistent results. Although no azeotrope were found, this mixture exhibited quite low relative volatility.

Inverted U-Shape Relationship Between Odor Concentration and Olfactory Short-Term Memory

We examined the return–volatility relationship for USO ETF oil price return and CBOE Crude Oil ETF Volatility Index, OVX. The data for the USO and OVX covers the period covering May 11, 2007 to February 28, 2013. Our OLS regression results suggest evidence of regular feedback and leverage effects. When we employ linear quantile regression techniques, we find evidence of regular and inverse feedback effects. The inverse feedback effects being noticeable in the upper quantile region of the oil return distribution. There is also support for a regular leverage effect in USO prices. We also examined the return–volatility relationship using quantile regression copula methods for measuring the degree of asymmetry in the relationships between the oil price return and implied volatility. The results of the analysis indicate, first, that there exists a negative relationship between contemporaneous oil VIX and USO ETF oil returns. Second, that the relationship between oil returns and implied volatilities depends on the quartile at which the relationship is being investigated. Third, there exists an inverted U-shaped dependency relationship between returns and implied volatilities across quantiles. Fourth, though an inverted U-shape exists, the shape is different from those observed in stock markets.

God's Model vs. Market Models

A thorough reading of Bergomi sheds new perspectives on rough volatility in relation to the meaning of the options market.

Experimental screening of ionic liquids as mass agents in the n-hexane/1-hexene extractive distillation

n-Hexane and 1-hexene are highly valued compounds within the petrochemical industry because of their wide range of applications. These compounds are generally found together in the same stream. Their separation is difficult to accomplish by conventional distillation due to their close boiling points. Technologies currently used to separate n-hexane and 1-hexene at industrial scale range from membrane processes to extractive distillation and liquid-liquid extraction with organic solvents. However, these processes present several technical and environmental drawbacks. A promising alternative is extractive distillation with ionic liquids as entrainers. In this work, a screening of ten ionic liquids was made to check their potential in the extractive distillation of n-hexane and 1-hexene mixtures. Firstly, the ionic liquids’ extractive properties were determined to establish which ionic liquids are suitable for the n-hexane/1-hexene extractive distillation. Five ionic liquids, namely [4bmpy][TCM], [4bmpy][Tf2N], [bmim]2[Co(SCN)4], [P66614][TCM] and [P66614][DCA] were selected. Secondly, vapor-liquid equilibrium experiments for the binary systems {n-hexane or 1-hexene + ionic liquid} were conducted at 343.2, 363.2 and 383.2 K to select the minimum solvent-to-feed ratio that guarantees homogenous ternary systems {n-hexane + 1-hexene + ionic liquid}. Then, the vapor-liquid equilibria for the ternary systems {n-hexane + 1-hexene + ionic liquid} were determined at the same three temperatures with a solvent-to-feed ratio on a mass basis of 10. Besides, solvent-to-feed ratios of 7.5 and 5 were also used for those systems containing [P66614]-based ionic liquids. n-Hexane/1-hexene relative volatilities up to 2.3 were obtained, overcoming those provided by other ionic liquids and organic solvents. Finally, the NRTL model was used to adjust the ternary data accuracy.

Bonds Don’t Need to Be Negatively Correlated with Equities

The current narrative that bonds no longer diversify equities because of low yields and a potential shift in bond-equity correlation fails to consider the relative importance of bond volatility in reducing overall portfolio volatility. Bonds will continue to provide diversification if bond volatility is lower than equity volatility, even if the correlation is positive. While better outcomes can be achieved under negative correlation, this is secondary to the impact of relative volatility. <b>Key Findings</b> ▪ The current narrative that bonds no longer reduce portfolio risk because of low yields and a potential shift in bond-equity correlation fails to consider the relative importance of bond volatility in reducing overall portfolio volatility. ▪ The role of bonds in the portfolio is to provide volatility reduction. Bonds will continue to lower portfolio volatility if bond volatility is lower than equity volatility, even if the correlation is positive. ▪ While better outcomes can be achieved under negative correlation, this is secondary to the impact of relative volatility.

A Simple Criterion for Feasibility of Heat Integration between Distillation Streams Based on Relative Volatilities

A Simple Criterion for Feasibility of Heat Integration between Distillation Streams Based on Relative Volatilities

Emerging Market Sell-Offs: India and the World

Capital flows to emerging markets are generally volatile, resulting in periodic "sudden stop” episodes – when capital inflows dry up abruptly, with significant negative effects on the economy and on financial variables. This paper reviews India’s experience with capital flows. The relative volatility of different kinds of capital flows in India is similar to that in other emerging markets. Our analyses suggest putting in place a medium-term policy framework that includes sound fiscal balance, a sustainable current account deficit, an environment conducive to investment, an appropriate level of reserves, avoidance of excessive appreciation or volatility of the exchange rate (through the use of reserves and macroprudential policy) and prepares the banks and firms to handle greater exchange rate volatility. In addition, it would be good for India to change the capital flow mix toward FDI flows and find ways to diversify the investor base toward investors with a longer-term view. It would also be useful to eventually graduate from the emerging market asset class. Finally, adopting a clear communication strategy to interact smoothly and transparently with market participants – involving regularly reasserting the commitment to sound policies, and reminders of the resilient underlying fundamentals – are likely to be helpful in risk-off times.

LABOR MARKET DYNAMICS UNDER TECHNOLOGY SHOCKS: THE ROLE OF SUBSISTENCE CONSUMPTION

This paper establishes new stylized facts about labor market dynamics in developing economies, which are distinct from those in advanced economies, and then proposes a simple model to explain them. We first show that the response of hours worked and employment to a technology shock—identified by a structural VAR model with either short-run or long-run restrictions—is substantially smaller in developing economies. We then present compelling empirical evidence that several structural factors related to the relevance of subsistence consumption across countries can jointly account for the relative volatility of employment to output and that of consumption to output. We argue that a standard real business cycle (RBC) model augmented with subsistence consumption can explain the several salient features of business cycle fluctuations in developing economies, especially their distinct labor market dynamics under technology shocks.

Lending Standards and Borrowing Premia in Unsecured Credit Markets

&lt;ns2:p&gt;Using administrative data from Y-14M and Equifax, we find evidence for large spreads in excess of those implied by default risk in the U.S. unsecured credit market. These borrowing premia vary widely by borrower risk and imply a nearly flat relationship between loan prices and repayment probabilities, at odds with existing theories. To close this gap, we incorporate supply frictions – a tractably specified form of lending standards – into a model of unsecured credit with aggregate shocks. Our model matches the empirical incidence of both risk and borrowing premia. Both the level and incidence of borrowing premia shape individual and aggregate outcomes. Our baseline model with empirically consistent borrowing premia features 45% less total credit balances and 30% more default than a model with no such premia. In terms of dynamics, we estimate that lending standards were unchanged for low risk borrowers but tightened for high risk borrowers at the outset of Covid-19. Borrowing premia imply a smaller increase in credit usage in response to a negative shock, which this tightening reduced further. Since spreads on loans of all risk levels are countercyclical, all consumers use less unsecured credit for insurance over the cycle, leading to 60% higher relative consumption volatility than in a model with no borrowing premia.&lt;/ns2:p&gt;

Implications of exchange rate volatility for trade: Volatility measurement matters

AbstractThe relationship between exchange rate volatility and trade is inconclusive in the current literature. I find evidence this is due to variation in definitions of exchange rate volatility. My results suggest common volatility measures weigh variation differently over time and economic conditions. Using an autoregressive distributed lag model, I demonstrate the importance of volatility measurement to the estimated relationship of volatility and exports. I find substantial variation across volatility measures, trading partners, and pre‐/post‐2008. When significant, the relationship is almost always negative, albeit unsubstantial. In order to overcome the literature's mixed results, the definition of volatility needs to be standardized.

Monitoring exchange rate instability in 12 selected Islamic economies

Exchange rate instability has become a key concern within economic policy circles ever since the 1973 breakdown of Bretton Woods agreement; after 47 years, central bankers realize the deleterious effect of exchange rate on the economy in the 12 selected OIC member countries we studied. The aim of this paper is to report the findings on a proposed measure of currency instability, namely the relative volatility, to test it with data relating to 12 OIC member Muslim-majority economies using more than 28 years data. We find that relative volatility is an effective measure for tracking currency instability and exchange rate targeting could be enhanced by including policy bands as well as recommended actions for each movement outside the policy band. Further, relative volatility is significantly correlated with monetary factors suggested by strong theories that drive the exchange rate equilibrium.

We the Animals and Honoring an Intimate Story of Brutal Love

In this edited interview, psychologists Nisha Gupta and Eric Greene interview filmmaker Jeremiah Zagar about We the Animals (2018), his film adaptation of the novel by Justin Torres. We the Animals is a coming-of-age story of an adolescent boy named Jonah who grows up with rambunctious brothers in a working class mixed-race family in upstate New York, and who must contend with both his volatile father and his emerging queer sexuality. Jonah’s mother and father have a volatile relationship that makes and unmakes the family many times over, often leaving the boys fending for themselves. As his brothers harden and grow into versions of their father, Jonah, who is the youngest, becomes increasingly aware of his desperate need to escape. Driven to the edge, Jonah embraces an imagined world all of his own. In this conversation, Jeremiah describes what it was like to honor novelist Justin’s intimate story by bringing it to screen, depict the nuanced realities of love interlaced with violence within family dynamics, and craft an immersive story that poses more questions than it answers.

ANALYSIS OF ENERGY CONSUMPTION OF EXTRACTIVE DISTILLATION FLOWSHEETS OF FOUR-COMPONENT SOLVENT MIXTURE

A comparative analysis of energy consumption for extractive distillation flowsheets was carried out. This was done by the example of methanol - ethanol - acetonitrile - mixture. These solvents are used in pharmaceutical industries. The basic system methanol - ethanol - acetonitrile - water contains four binary and one ternary minimum-boiling azeotropes. Pressure change has almost no effect on the location of separatric surfaces. Therefore, extractive distillation should be used to separate solvents mixtures of any composition. Industrial entrainers dimethyl sulfoxide and glycerol are considered as selective agents. The effect of entrainer on vapor-liquid equilibrium at 30 and 101.32 kPa was evaluated by the relative volatility of the components forming azeotropes and the selectivity of the agents. The simulation was carried out on the Aspen Plus V.10.0 program environment. Two extractive distillation flosheets for the methanol - ethanol - acetonitrile - water separation are investigated. Both schemes include a two-column complex for the extractive distillation of the base mixture: in the first column, organic solvents are separated from water, and in the second column, the agent is regenerated. For subsequent separation of acetonitrile, extractive distillation with dimethyl sulfoxide or glycerol is also used. But separation of methanol-ethanol - entrainert zeotropic mixtures differs in the order of separation of components in schemes I and II. In scheme I, regeneration of the agent and further separation of the alcohol mixture is provided, in scheme II, methanol is first isolated, and then ethanol is separated from the agent. The optimized results for both schemes at columns pressures 30 and 101.32 kPa are performed. Different sets of selective agents introduced into extractive distillation columns are considered. The concept of an effective set of entrainers is introduced. The evaluation of the design alternatives need the assessment of energy demands. Total energy consumption for separation (reboiler duty) for the scheme II at 35-38% higher than values for scheme I. On the criterion of the minimum total energy consumption for the separation the scheme I was recommended: pressure columns 30 kPa, effective set of entrainers: glycerol for dehydration of the base mixture and dimethyl sulfoxide for acetonitrile isolation.

Impact of physio-thermo properties on the azeotrope formation in benzene – 1-alkanol blends

First point of view of this report is briefly comments about the potential of azeotrope development in the blends of 1-alkanols (1-pentanol/1-hexanol/1-heptanol) with benzene. The relative volatility (r) calculation of all binary blends was used to prove this possibility of the azeotrope formation. Second point of view of this report is also concerned with the same idea but achieved by ultrasonic study using different parameters such as ultrasonic velocity (U), density (ρ), and viscosity (η), and few thermo–acoustical variables like adiabatic compressibility (β), free length (Lf), free volume (Vf), and internal pressure (πi), and their excess (AE) magnitudes. In this regard, the important standard magnitudes of the individual components and their mixtures are experimental measured. The origin of the existence of the suggested intermolecular interaction is found to be useful in predicting the possible azeotrope formation and in determining the exact mole fraction of such formations. The excess parameters are fitted to polynomial type Redlich-Kister equation and coefficients of the fitting are found to support the present investigations.

Energy efficiency comparison between a conventional tray column and a novel heat-intensified thermosyphon-assisted falling film distillation unit: an assessment for mixtures with different relative volatilities

An energy performance comparison between a novel thermosyphon-assisted falling film distillation unit and a conventional tray unit was carried out for three mixtures with different relative volatilities: ethanol-water, acetone-isopropanol, and acetone-water. Experimental data from the pilot-scale plant were used as targets in the simulation runs through the Hysys® software. Thus, the separation performed in the falling film unit was reproduced in a conventional tray column. The thermosyphon-assisted falling film unit required less energy, with reductions of 24% for acetone-isopropanol, 30% for ethanol-water, and 55% for the acetone-water mixture. The energy-use ratio also showed that for each kW consumed in the falling film unit, the conventional unit would consume 1.33 kW for acetone-isopropanol, 1.44 kW for ethanol-water, and 2.21 kW for acetone-water, based in the same separation. Therefore, this novel distillation apparatus is more advantageous as an energy-saving viable option for separating mixtures with different relative volatilities.

Influence of Solvent and Acid Properties on the Relative Volatility and Separation Selectivity for Extractive Distillation of Close-Boiling Acids

The increasing need for sustainable processes stimulates the production and recovery of renewable organic acids. The purification of these acids is often difficult because of similar acid volatilities but can be improved through extractive distillation. Generic insights into solvent effects on the separation efficiency for close-boiling acids are however lacking. This study provides insights into the effect of acidity, the acidity difference between the acids, the hydrogen-bonding strength of the solvent, and the solvent-to-feed ratio on organic acid separation efficiency. For an acetic acid–formic acid (AA–FA) mixture, the addition of high-boiling organic acids increases the relative volatility of FA over AA significantly. The addition of a Lewis base reverses the relative volatility, which depends on the applied solvent-to-feed ratio and the Lewis base BF3 affinity. For several binary acid mixtures (such as AA–FA and monochloroacetic acid–dichloroacetic acid), where the acids have a relatively big difference in acidity (ΔpKa ≥ 1), the separation selectivity appears practically independent of the acid strength of the individual acids and increases with increasing BF3 affinity of the Lewis base. For acid mixtures with a lower ΔpKa, a lower separation selectivity is obtained, as observed for separation of the pivalic acid–butyric acid and valeric acid–2-methyl butyric acid mixtures. When one of the acids in the mixture contains a secondary ketone group (i.e., levulinic acid in a levulinic acid–octanoic acid mixture), the strongest acid based on pKa is not necessarily attracted most by the added Lewis base. This, at first sight, unexpected behavior is most likely the result of complex intra- and intermolecular interactions and is quantitatively in line with COSMO-RS-based selectivity predictions.

In-line conductivity measurement to select the best distillation technique for improving the quality of apricot brandies

During column distillation of fruit brandies, reflux rates in the column can heavily impact the transition of less volatile congeners into the product contributing either to an unclean taste when too enriched or to a lack of aroma intensity when too depleted. The authors of this study demonstrated that besides the reflux rate other factors need to be taken into consideration, specifically when the fruit contains high levels of carboxylic acids. Using a novel in-line measurement technique for monitoring distillate conductivity, it was shown that the heating ramp of the pot is equally important as it easily impacts the relative volatility of tail congeners enabling them to enter the condenser already at the beginning of the distillation. Tail congeners present in the heart fraction may not only be detrimental for the final product quality by themselves but also shifting the point of tails which make conventional methods for automated tail separation more prone for failure. By means of a statistical approach a new model was proposed how to select the right balance between reflux conditions and heating parameters resulting in an improved product quality of apricot distillates.

Agricultural co-operatives participating in supply chain integration in China: A qualitative comparative analysis.

Agro-food supply chain integration (ASCI) plays a growingly important role in the stable and sustainable development of agriculture. However, it is challenging for core firms to integrate the small-scale and scatted farmers due to complex transaction processes and volatile relationships in China. Agricultural co-operatives are organizations that unite farmers’ power and help them achieve economic benefits. Our research focuses on ASCI from the perspective of co-operatives. A comprehensive cooperative framework, including trinity co-operatives and trinity federations, is conducted to figure out the position and process of agricultural co-operatives in ASCI, while QCA provides detailed collaborative patterns for agricultural co-operatives to adopt. Results show that agricultural co-operatives can achieve high economic and social/environmental performance when participating in ASCI. This study further completes the ASCI literature and offers many managerial and academic implications to co-operatives’ members and policy-makers.

Adaptive MPC Controller based Cascade Control of Distillation Column Parameters Estimation and Optimization

One of the key element of many industrial process plants is a crude oil distillation system. This system requires heat for the vaporization of a mixture of feed to the distillation column in vapor form. In the existing process of distillation, an abnormal change of heat is exhibited due to improper control and monitoring of disturbances affecting the plant. This would result for undesired loss of product and product purity to be reduced. The parameters that are expected to be considered in the analysis, model and control of a distillation system described under the proposed study are inlet feed temperature, distillation column temperature, feed composition, internal liquid and vapor composition, feed flow rate, reboiler temperature and an external reflux temperature to the distillation tower. Controlling distillation column parameters with Adaptive model predictive control allows for the determination of the predicted future instant values of the plant outputs. Using such control technique, the controlled plant outputs such as the temperature of distillation column, feed preheater, re boiler and the upper reflux is properly controlled and their parameters are estimated using recursive least squares approach in the entire process adaptation mechanism. From the analysis and optimization work made on the proposed system, the efficiency of the plant outputs in tracking their corresponding set point has improved based on the value of the transient system parameters as well as the value of relative volatility of feed mixture to the column. As per the finding in the analysis of the process, 95.4% and 93.5% improvement on the set point tracking and to amount of evaporation liquid feed has been obtained respectively. On the other hand an improvement on transient parameters has been achieved to all plant outputs. As per the result obtained from the analysis, the peak overshoot, settling time and peak time of the system response has found to be less than 40% including the effect of measured disturbance to the plant. Hence, entire process variable optimization has been performed using the parameters of the model predictive controller to provide the proper degree of stability. Finally the proposed method of study has compared with with other control strategies through which the performance the proposed design has been ensured.