Membrane materials in the pervaporation separation of aromatic/aliphatic hydrocarbon mixtures—A review

The separation of aromatic/aliphatic hydrocarbon mixtures is a significant process in chemical industry, but challenged in some cases. Compared with conventional separation technologies, pervaporation is quite promising in terms of its economical, energy-saving, and eco-friendly advantages. However, this technique has not been used in industry for separating aromatic/aliphatic mixtures yet. One of the main reasons is that the separation performance of existed pervaporation membranes is unsatisfactory. Membrane material is an important factor that affects the separation performance. This review provides an overview on the advances in studying membrane materials for the pervaporation separation of aromatic/aliphatic mixtures over the past decade. Explored pristine polymers and their hybrid materials(as hybrid membranes) are summarized to highlight their nature and separation performance. We anticipate that this review could provide some guidance in the development of new materials for the aromatic/aliphatic pervaporation separation.

A 2D numerical study on the condensation characteristics of three non-azeotropic binary hydrocarbon vapor mixtures on a vertical plate

To improve the transportation efficiency and reduce the supply cost,the liquefaction becomes an important technology to store and transport the natural gas.During the liquefaction,the various components(e.g.propane,ethane,methane etc.)undergo fractional condensation phenomenon due to their different boiling points.This means that when one component condenses,others play a role of non-condensable gas(NCG).In order to reveal the influence mechanism of NCG on this condensation process,a numerical method was employed in this paper to study the condensation characteristics of three non-azeotropic binary hydrocarbon vapor mixtures,namely the propane/methane(80%–95%),ethane/methane(65%–85%)and methane/nitrogen(2%–13%)mixtures,on a vertical plate.The model was proposed based on the diffusion layer model,and the finite volume method was used to solve the governing equations.A user defined function was developed by cell iterative method to obtain the source terms in the condensation process.The numerical results show that the gas phase boundary layer formed by the NCG becomes the main resistance to the reduction of heat transfer coefficient.And for the above three mixtures,there is a negative correlation between the NCG concentration and the heat transfer coefficient.Meanwhile,the results show a good agreement with the experimental data,meaning that the proposed model is reliable.Three mixtures within same non-condensable mole fraction of 20%were also investigated,indicating that the mixtures with a higher binary hydrocarbon molecular ratio have a lower heat transfer coefficient.As a result,the presence of the lighter NCG contributes to a thicker boundary layer.

Vapor-Liquid Equilibrium of Toluene-Polycyclic Aromatic Hydrocarbon System in Sub- and Supercritical State

The phase behaviors of toluene/polycyclic aromatic hydrocarbon mixture systems were investigated with a continuous-flow type apparatus at 573.2, 598.2, 623.2 and 648.2 K, while the pressure changed from 1 to 5MPa. The pseudo-binary phase behaviors were predicted with the Peng-Robinson equation of state with interaction parameters between toluene and pseudo-components considered. The phase diagrams of the system have been classified following the category of phase boundary diagram models. The extraction selectivity and efficiency of tolu-ene as a solvent was discussed by comparing with that of hexane. The prediction model for selectivity was also suggested.

Simple Fluorimetric Determination of Benzo[a]pyrene in Cigarette Smoke without Preseparation Procedure

Constant-energy synchronous fluorimetry was used for the identification of benzo[a]pyrene in mixtures with a detection limit of 1.34 nmol/L. The recovery experiments in cigarette smoke samples have also obtained satisfactory results of 99.1-103.5% for benzo[a]pyrene.

Simple Synchronous Fluorimetric Method for Determination of Benzo[a] pyrene in Airborne Particulates without a Pre-Separation Procedure

A sensitive analytical method, constant-energy synchronous fluorimetry, has been used to determine benzo[a]pyrene （BaP） selectively in airborne particulates （AP）. A constant-energy difference of 1 400 cm^-1 was selected for obtaining single spectral peak. The method could easily identify BaP in an 18-component polycylic aromatic hydrocarbons（PAHs） mixtures. Calibration plots in methanol solution and in sodium dodecylsulfate （SDS） micellar media show a good linearity （R〉0.999） in the BaP concentration range generally fotund in the environment. The method gives a detection limit of 0.40 nmol/L in SDS micellar medium and 1.34 nmol/L in methanol solution.

Group Contribution based Flammability Limit Estimation of Hydrocarbon-Inert Gas Mixture

As group contribution method is easy to apply and has a wide application range,current study has developed this model to predict flammability limit of hydrocarbons mixed with inert gas using the Marrero/Gani group contribution method,which is significative to the safe application of hydrocarbons in the ORC system.The whole modeling process is divided into two parts:pure compound prediction and mixture prediction.The contribution factors of inert gases and dilute concentration were first introduced in the group contribution method.Moreover,the respective 95%-confidence interval of the mixture based on linear superposition method has been proposed in the developed group contribution model to improve the safety coefficient.For CO2 as inert gas,the average relative error and correlation coefficient are 5.34%and 0.88 for lower flammability limit while 6.99%and 0.95 for upper flammability limit.For N2 as inert gas,the average relative error and correlation coefficient are 7.47%and 0.84 for lower flammability limit while 6.68%and 0.97 for upper flammability limit.Most importantly,this group contribution method has extended the application range to make up the shortcomings of other flammability limit prediction methods aiming at hydrocarbon and inert gas mixtures and proposed the uncertainty analysis to provide reliable prediction range.