Amar N. Goswami

THE REMOVAL OF FURFURAL FROM WATER BY ADSORPTION WITH POLYMERIC RESINS

The removal of furfural from water by adsorption on a polymeric resin XAD-4 was studied. Equilibrium isotherm measurements were made and column dynamic data collected under various sets of operating conditions. The axial-dispersed plug-flow model was used to simulate the experimental data. The linear driving force parameters required in these simulations were determined independently of the column measurements, providing a more versatile simulation model. The model predicts the breakthrough curves with a fair degree of accuracy.

Carbon Di-Oxide Removal with Mesoporous Adsorbents in a Single Column Pressure Swing Adsorber

Abstract A five-step PSA cycle was studied for CO2 separation from CO2-N2 gas mixture in a single column at elevated temperatures using Poly-ethyleneimine (PEI) impregnated mesoporous silica SBA-15 as adsorbent. The PSA cycle study included a strong adsorptive rinse step in which the strongly adsorbed component, i.e., CO2 was used for rinsing the adsorbent bed in order to increase the purity of CO2 product. The study indicates that the adsorbent is regenerable under typical PSA conditions. The productivity of the adsorbent studied for CO2 separation was found to be comparable with commercial zeolite adsorbents as reported in literature.

Isobaric vapour—liquid equilibria of the systems: Benzene—triethylene glycol, toluene—triethylene glycol and benzene—N-methylpyrrolidone

Abstract Isobaric vapour—liquid equilibria have been determined at 101.325 kPa for three binary mixtures: benzene—triethylene glycol, toluene—triethylene glycol and benzene— N -methylpyrrolidone. The data have been correlated with reasonable accuracy using the NRTL, Wilson and UNIQUAC equations using a non-linear regression approach based on the maximum-likelihood principle.

Effect of emulsion breakage on selectivity in the separation of hydrocarbon mixtures using aqueous surfactant membranes

In liquid membrane separation processes emulsion breakage results in non-selective physical mixing of the feed mixture with the receiving solvent phase. In this paper a model is developed for describing the interphase transfer process, which takes emulsion breakage into account. The overall transfer is envisaged as a result of two parallel transfer mechanisms: (i) diffusive transport across the membrane and (ii) non-selective physical mixing of the feed with the receiving phase due to emulsion breakage. For selective removal of aromatics from non-aromatics in a feed mixture the “ideal” selectivity, β, obtained in the absence of non-selective breakage, will he given as the ratio of the products of the distribution coefficients times the diffusivity in the aqueous membrane phase. Experiments were carried out in a batch stirred cell to determine the permeation rates for a benzene-n-heptane mixture. From the experimentally observed selectivities the contribution due to emulsion breakage was estimated. This fractional breakage was in good agreement with values determined independently using a water-insoluble dye tracer technique, lending support to the developed model. Further experiments were carried out with the system 1-methylnaphthalene-dodecane, and breakage-corrected transfer rates were determined. The model developed in this paper, together with the experimental studies, sheds light on the mechanism of liquid membrane permeation and should aid in scaling-up processes for dearomatization of naphtha and kerosine.

Studies on the permeation of aromatic hydrocarbons through liquid surfactant membranes

Abstract The effect of operating parameters on the batch scale permeation of hydrocarbons from benzene—heptane mixtures and a straight run naphtha through liquid membrane is reported. The thirteen operating parameters studied include: mixing intensity, surfactant concentration, treat ratios, contact times, temperature and additives. The variations observed in the two key properties of selectivity and aromatic recoveries as well as in product compositions with change in operating parameter is discussed. Surfactant concentration contact time during permeation, type and concentration of additive used appear to exert a marked effect on the enrichment obtained. The careful optimization of operating parameters give selectivities as high as 50 and aromatic recoveries of 75% in one stage at 30°C. Comparison of data with batch liquid—liquid extraction data from extraction of similar feed mixtures with the most widely used solvent, sulpholane, under typical industrial conditions, has shown that selectivities and aromatic recoveries in liquid membrane permeation (LMP) are much higher. Batch scale LMP experiments with straight run naphtha as feed show that under optimum conditions of membrane stability and operating parameters the dearomatization of naphtha from an initial aromatic level of 22 vol.% to 10.5 vol.% is possible in one stage at 30°C with a raffinate yield of 63%. The results obtained on benzene—heptane model mixture compare fairly well with those obtained on naphtha feed.

Surface Diffusion Kinetics in the Adsorption of Acetic Acid on Activated Carbon

Abstract The recovery of acetic acid from industrial wastewaters is an important separation problem, and one of the routes suggested for this application is liquid phase adsorption on activated carbon adsorbents. Designing an adsorber for such applications requires knowledge of equilibrium isotherm as well as adsorption rate data. In the present work the kinetics of adsorption of acetic acid on activated carbon has been studied. A three-parameter isotherm model has been used to correlate the equilibrium data, and a combined external film transfer-surface diffusion model has been used to simulate the experimental adsorption rate data. The surface diffusivity values obtained range from 6 to 8.5 × 10−7 cm2/s, and the values show a dependence on surface loading. These surface diffusivity values can be used in modeling the column breakthrough behavior for this system.

Studies on permeation of hydrocarbons through liquid membranes in a continuous contactor

Abstract This paper reports experimental studies, in a continuous cocurrent packed column, on the removal of aromatics from hydrocarbon streams by making use of selective transfer through aqueous surfactant membranes. Two types of feed mixtures were used: (i) benzene—heptane and (ii) straight run naphtha from Bombay High crude oil. The receiving phase in both cases was kerosene. The height of a mass transfer unit (HTU) was determined and found to largely lie in the range 2-2.5 m, irrespective of feed composition and solvent/feed ratio. The experimental study confirms the feasibility of a liquid membrane process for dearomatization and provides HTU data for further feasibility and scale-up studies.

Mass transfer studies in liquid membrane hydrocarbon separations

Abstract The effects of operating parameters on mass transfer coefficients of benzene permeating through liquid surfactant membranes have been studied. The study indicates that major resistance to mass transfer lies in the aqueous membrane phase. Mixing intensities used in forming the emulsion and dispersing it in the external phase have relatively less influence. Using a simple membrane film model approach, these mass transfer coefficients can be predicted within reasonable limits. The membrane film thickness to be used in these predictions varies with the holdup of micro phase in the emulsion, and can be estimated from the recently proposed equation of Kataoka .

Dearomatisation of a refinery kerosene by liquid surfactant membranes - prediction of extraction rates

Abstract A possible low energy alternative to solvent extraction processes for kerosene dearomatisation to meet product specifications of low aromatic content in jet fuels/superior kerosene, is the liquid surfactant membrane (LSM) process as demonstrated in several recent papers. However, for design of separation equipment by this process, predictive mass transfer models are required. The present study shows that the analytical solution to the transient diffusion equation as developed by Vorstmann and Thijssen for liquid-liquid extraction can be used to predict the extraction rate of kerosene aromatics through LSM. The parameters required in the model calculations can be measured experimentally or can be estimated independently. The calculations are based on the assumption that the kerosene aromatics can be represented by a model hydrocarbon, 1-methylnaphthalene. The model should prove a useful tool in design/simulation calculations for a kerosene LSM refining process.

Effect of surfactant type on selectivity for the separation of 1-methylnaphthalene from dodecane using liquid membranes

The selective removal of aromatics from kerosine for the purposes of smoke-point improvement and to meet the specifications for aviation turbine fuel is an industrially important operation. The present study is part of a programme for developing an energy-efficient aqueous surfactant membrane process with high selectivities for aromatics removal. In the experimental studies, carried out in a batch mixer-settler unit, the kerosine feed was modelled using a synthetic mixture of 1-methylnaphthalene and dodecane. The objective of the experimental study was to study the influence of the surfactant type on the selectivity for removal of l-methylnaphthalene. Eight different types of surfactants were used in the studies, with HLB (hydrophile-lipophile balance) numbers ranging from 12.8 to 17.8. The selectivity β, defined as the ratio of the mass transfer coefficients for transfer of aromatics to that of the non-aromatics, was determined after correcting for nonselective transport due to emulsion breakage. The selectivity thus obtained correlated very well with W, the work of transfer, which reflects the ease of adsorption of the surfactant to form a monolayer relative to the ease of micellization. For high W (i.e., lower ease of micellization) the selectivities are higher, as might be expected because micelle formation leads to non-selective transport through the membrane barrier. The study sheds light on the appropriate choice of surfactant to obtain increased selectivities.