Relative volatility

About: Relative volatility is a research topic. Over the lifetime, 545 publications have been published within this topic receiving 7333 citations.

Extractive Distillation: A Review

Abstract: Extractive distillation is more and more commonly applied in industry, and becomes an important separation method in chemical engineering. This paper provides an in‐depth review for extractive distillation. Separation sequence of the columns, combination with other separation processes, tray configuration and operation policy are included in process of extractive distillation. Since the solvent plays an important role in the design of extractive distillation, such conventional and novel separating agents as solid salt, liquid solvent, the combination of liquid solvent and solid salt, and ionic liquid are concerned. The prominent characteristics of extractive distillation is that one new solvent with high boiling‐point, i.e. separating agent, is added to the components to be separated, so as to increase their relative volatility. Selection of a suitable solvent is fundamental to ensure an effective and economical design. CAMD as a useful tool is applied for screening the solvents and thus reducing the expe...

The Nature of Ionic Liquids in the Gas Phase

Abstract: Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS) experiments showed that when aprotic ionic liquids vaporize under pressure and temperature conditions similar to those of a reduced-pressure distillation, the gas phase is composed of discrete anion-cation pairs. The evolution of the mass spectrometric signals recorded during fractional distillations of binary ionic liquid mixtures allowed us to monitor the changes of the gas-phase composition and the relative volatility of the components. In addition, we have studied a protic ionic liquid, and demonstrated that it exists as separated neutral molecules in the gas phase.

Influence of Ionic Liquids on the Phase Behavior of Aqueous Azeotropic Systems

Abstract: The use of ionic liquids (ILs) in chemistry and electrochemistry has been studied for some decades. Only recently, researchers have focused on the suitability of ILs as selective solvents in the field of separation technology. ILs represent suitable entrainers and extraction solvents for the separation of azeotropic mixtures by means of extractive distillation and solvent extraction. In this work, ternary vapor−liquid and liquid−liquid equilibria of the azeotropic mixtures ethanol + water and THF + water containing different kinds of commercially available ILs are presented. The four ionic liquids used are derived from butyl-methylimidazolium tetrafluoroborate [BMIM]+ [BF4]- by systematic variation of the cation or the anion. The influence of the IL structure on the relative volatility of the low boiling component in extractive distillation and on the selectivity in solvent extraction processes is discussed in this work.

Process for liquefying a natural gas stream containing at least one freezable component

Abstract: This invention is a process for producing pressurized liquid (19) rich in methane from a multi-component feed stream (10) containing methane and a freezable component having a relative volatility less than that of methane. The multi-component feed stream (10) is introduced into a separation system (31) having a freezing section operating at a pressure above about 1,380 kPa (200 psia) and under solids forming conditions for the freezable component and a distillation section positioned below the freezing section. The separation system (31) produces a vapor stream (14) rich in methane and a liquid stream (12) rich in the freezable component. At least a portion of the vapor stream is cooled to produce a liquefied stream rich in methane having a temperature above about -112 °C (-170 °F) and a pressure sufficient for the liquid to be at or below its bubble point to produce a product (20) and a stream (21) to provide refrigeration to the separation system.

Review of Extractive Distillation. Process design, operation optimization and control

Abstract: Extractive distillation processes enable the separation of non-ideal mixtures, including minimum or maximum boiling azeotropes and low relative volatility mixtures. Unlike azeotropic distillation, the entrainer fed at another location than the main mixture induces an extractive section within the column. A general feasibility criterion shows that intermediate and light entrainers and heterogeneous entrainers are suitable along common heavy entrainers. Entrainer selection rules rely upon selectivity ratios and residue curve map (rcm) topology including univolatility curves. For each type of entrainer, we define extractive separation classes that summarize feasibility regions, achievable products and entrainer – feed flow rate ratio limits. Case studies are listed as supplementary materials. Depending on the separation class, a direct or an indirect split column configuration will allow to obtain a distillate product or a bottom product, which is usually a saddle point of rcm. Batch and continuous process operations differ mainly by the feasible ranges for the entrainer – feed flow rate ratio and reflux ratio. The batch process is feasible under total reflux and can orient the still path by changing the reflux policy. Optimisation of the extractive process must systematically consider the extractive column along with the entrainer regeneration column that requires energy and may limit the product purity in the extractive column through recycle. For the sake of reducing the energy cost and the total cost, pressure change can be beneficial as it affects volatility, or new process structures can be devised, namely heat integrated extractive distillation, extractive divided wall column or processes with preconcentrator.