CO mixture gas separation using composite hollow fiber membranes prepared by interfacial polymerization method

Accepted Manuscript Title: H2 /CO mixture gas separation using composite hollow fiber membranes prepared by interfacial polymerization method Author: Wook Choi Pravin G. Ingole Jong-Soo Park Dong-Wook Lee Jong-Hak Kim Hyung-Keun Lee PII: DOI: Reference:

S0263-8762(15)00243-9 http://dx.doi.org/doi:10.1016/j.cherd.2015.06.037 CHERD 1948

To appear in: Received date: Revised date: Accepted date:

22-4-2015 25-6-2015 29-6-2015

Please cite this article as: Choi, W., Ingole, P.G., Park, J.-S., Lee, D.-W., Kim, J.-H., Lee, H.-K.,H2 /CO mixture gas separation using composite hollow fiber membranes prepared by interfacial polymerization method, Chemical Engineering Research and Design (2015), http://dx.doi.org/10.1016/j.cherd.2015.06.037 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

Graphical abstract

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H2/CO mixture gas separation using composite hollow fiber membranes prepared by

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interfacial polymerization method

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Wook Choi1,2, Pravin G. Ingole1, Jong-Soo Park1, Dong-Wook Lee1, Jong-Hak Kim2,

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Hyung-Keun Lee1*

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Korea Institute of Energy Research, 71-2 Jang-dong, Yuseong-gu, Daejeon, Korea

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Department of Chemical and Biomolecular Engineering, Yonsei University, Korea

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Research Highlights PES-HF membrane with selective thin layer was developed by IP for gas separation. CHMA was selected as aqueous monomer and TMC as organic monomer.

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The new thin-film composite membranes show excellent gas separation performance.

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Our results are instructive to develop TFC membranes for H2/CO gas separation.

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TFC membranes have superior industrial applications (Gas to Liquid Process).

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H2/CO mixture gas separation using composite hollow fiber membranes prepared by

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interfacial polymerization method

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Wook Choi1,2, Pravin G. Ingole1, Jong-Soo Park1, Dong-Wook Lee1, Jong-Hak Kim2,

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Hyung-Keun Lee1* 1

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Korea Institute of Energy Research, 71-2 Jang-dong, Yuseong-gu, Daejeon, Korea

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Department of Chemical and Biomolecular Engineering, Yonsei University, Korea

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Abstract

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This paper describes the study on H2/CO mixture gas separation through thin film

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composite (TFC) membranes prepared by interfacial polymerization method. Composite

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membranes have been widely applied in gas separation process. Polyethersulfone (PES)

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hollow fiber membranes (HFMs) are fabricated using dry-wet phase inversion method as high

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permeability substrates. H2/CO mixture gas selectivity and permeance were studied using

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different concentrations of aqueous and organic phase monomers. Cross-linked structures of

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TFC membranes by interfacial polymerization were confirmed and discussed by using the

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compiled results of characterization, such as ATR-FTIR, and FE-SEM, TEM. The

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performance of HFM using different monomer concentrations of 1,3-cyclohexanebis

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methylamine, CHMA (aqueous phase monomer) and trimesoyl chloride, TMC (organic phase

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monomer) towards H2/CO mixture gas selectivity and permeance have been studied, and the

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effects of operating pressures, retentate flow rates and stage-cuts on separation factor and

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permeance were also investigated in this work. The monomers concentrations affect the

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selectivity and permeability in H2/CO mixture gas separation. Experimental results confirmed

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that increasing of operating pressure and stage-cut led to higher separation factor and showed

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simulation of module design to consider characteristics of membrane and behaviors for

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H2/CO mixture gas separation. In this paper, also represent the membrane spinning,

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polymerization and Membrane process design.

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Keywords: Thin film composite (TFC) membrane; Interfacial polymerization; Gas

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separation; Membrane structure; H2/CO mixture gas; Membrane process design

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*Corresponding author: Tel.: +82-42-860-3647; Fax: +82-42-860-3134

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Email address: [email protected]

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(Hyung Keun Lee)

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1. Introduction

The study of membrane separation was proposed by Loeb and Sourirajan in 1960

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about cellulose acetate reverse osmosis membrane (Loeb and Sourirajan, 1963). Furthermore

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gas separation membranes were commercialized by Monsanto and Perma for hydrogen

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recovery. In recent years, gas separation technology was applied in many industries (Koros

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and Fleming, 1993). During the past five decades, lots of papers and patents regarding gas

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separation membranes were published. With oil price increasing rapidly and urgency of

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reducing the global CO2 emission, the hydrogen has emerged as an important and interesting

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synthetic fuel from natural gas. The hydrogen source fuel has the various advantages like

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clean, economy and environment friendly (Marban and Valdes-Solis, 2007). International

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Energy Agency (IEA) also forecasted that natural gas production will increase from 4.0 tcm

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(trillion cubic meters) in 2012 to 5.01 tcm in 2035 (IEA, 2012). Among the hydrogen

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energies, Gas–to-Liquid (GTL) technology is an attractive process from small and medium

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natural gas field to gain the clean synthetic oil and this process is divided into three parts.

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Fischer-Tropsch (FT) is reaction from synthesis gas using iron (Fe) and cobalt (Co) catalyst

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on high temperature condition for liquid hydrocarbon product and synthetic fuel was

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produced by upgrading process. Before the FT reaction, natural gas changed synthesis gas

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through the reforming reaction such as steam reforming, partial oxidation and auto thermal

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reforming, (Atersenasberg-Petersen et al., 2001; Requies et al., 2006; Rostrup-Nielsen, 2002).

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Synthesis gas is produced in the process. Depend on the synthesis gas ratio as reforming

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process and the product type demanded appropriate hydrogen and carbon monoxide mixture

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gas ratio. H2/CO mixture gas ratio is particularly important because it affects amount of

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production (Bian et al., 2002; Lee et al., 2011). Therefore, H2/CO ratio can be controlled by

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optimization but air separation unit is too bulky and very expensive (Park et al., 2014).

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However membrane processes have many economical advantages as intensive compact

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process, easy to control, and flexible process to respond condition (Kim et al., 2013). Many

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membranes and materials have been studied for H2/CO separation. Among them, David et al.

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studied a H2/CO mixture gas separation using Matrimid hollow fiber and flat sheet membrane

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(David et al., 2012a, 2012b). Peer et al. reported that polyimide membrane had good potential

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for H2/CO separation. They also simulated the membrane process for optimum operational

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condition using pure and mixture gas permeance and selectivity (Peer et al., 2007).

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In this paper, interfacial polymerization (IP) method was selected to prepare the

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membrane for separation of H2/CO mixture gas. IP method was reported by Mogan in 1960

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for interfacial polycondensation (Morgan, 1965). TFC membrane was made by interfacial

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polymerization method on the porous support layer and TFC has many advantages for high

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selectivity and gas permeance (Mulder, 1996). In general, IP method has been used for 6

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manufacturing reverse osmosis membrane. The polyamide active layer formed by IP method

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showed a high water flux and high salt rejection as TFC membrane. TFC membrane consist

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of different types of diamines such as m-phenylene diamine, p-phenylenediamine, 3,5-

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diaminobenzoic acid, piperazine (Xu et al., 2013; Buch et al., 2008).

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applied for gas separation. Sridhar et al. reported possibility of preparing a polyamide defect

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free membrane by interfacial polymerization for gas separation (Sridhar et al., 2007). Li et al.

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reported CO2 separation with another gas using IP method (Liu et al., 2011). Wang et al.

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studied about CO2 separation from flue gas (Wang et al., 2013). This study describes

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preparation of the hollow fiber membrane module for H2/CO separation by IP according to

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the aqueous and organic phase monomer concentrations, and H2/CO separation results under

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the various gas flow rates, gas ratios and operating pressures. The membrane modeling was

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initially performed for choice of materials, operating condition, and design of module

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condition. Using the simulation study in the hollow fiber membranes can be designed for

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optimal process about considering the flow pattern and the separation module, such as an

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array. In the design process, through the calculation of the change and the effective

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membrane area of the separation efficiency according to the hollow fiber membrane type and

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changes in operating conditions can be derived at the best operating conditions for minimize

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the economic loss (Chung et al., 1997; Pinnau et al., 1990). In this study, using manufactured

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membrane modules experiments were performed on the lab-scale. At this time, based on the

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experimental results of permeation behaviors were interpreted using simulation program

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(MATLAB) for the optimized process as maximized performance, reduced cost and

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satisfaction when the scale-up of H2/CO separation process.

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Recently, IP has been

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2. Experimental

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2.1 preparation of PES hollow fiber membrane The hollow fiber membrane was fabricated by dry/wet phase inversion method using

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PES as a substrate material. PES has excellent thermal and dimensional stability as well as

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strong chemical resistance (Kim et al., 2012). PES also has a high degree of chain rigidity

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because of its regular and polar backbone. The method to fabricate the hollow fiber

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membrane has been explained elsewhere (Park et al., 2008). The composition of the dope

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solution and the spinning conditions for the preparation of the PES substrate are listed in

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Table 1. The dope solution and internal coagulant (D. I. water) were passed through a double

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pipe spinneret of 0.16/0.9 mm inner counter diameter with an air gap maintained at 0.5 cm.

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The dope solution was composed of 18.0 wt.% PES (Ultrason® E6020P, BASF, Germany),

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77.0 wt.% N-methylpyrrolidone (NMP, Merck), and 5.0 wt.% lithium chloride (LiCl, sigma

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Aldrich, USA). NMP and LiCl were used as the solvent and additive respectively. After

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spinning, the fibers were washed in a bath of continually flowing (50 cm3/min) water (313K)

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for six days to remove the remaining solvent, and were post-treated with methanol for 2 h to

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improve the solvent. Finally, the fibers were dried for six days. Fig. SI1 (supporting

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information) showed schematic diagram of hollow fiber spinning process.

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Table 1

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2.2 Preparation of composite membrane on PES substrate using interfacial

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polymerization

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The composite membranes were prepared by coating selectivity layer in situ on the

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surface of polyethersulfone hollow fiber membrane by interfacial polymerization. 1,38

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cyclohexanebis methylamine (CHMA) was selected as the monomer of the aqueous phase

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and trimesoyl chloride (TMC) was selected as the monomer of the organic phase as shown in

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Fig. 1. Thoroughly washed PES hollow fiber membranes were immersed in an aqueous

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solution of CHMA for 5 min, followed by draining off for 3-5 min to remove excess solution.

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It was then immersed into hexane solution of TMC of desired concentration for 0.1-1.0 wt.%,

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followed by draining off excess solution. The polymerization reaction occurs on the surface

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of PES hollow fiber membrane resulting in the formation of an ultrathin layer of cross-linked

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co-polyamide. The composite membrane obtained was cured in hot air circulation at 70-80 °C

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for 5 min whereby polymer layer attains chemical stability (Ingole et al., 2012). After heat

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treatment, the membrane was kept at room temperature for 2 h. Table 2 disclosed the

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compositions of aqueous as well as organic phase monomer solutions and reaction times used

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for interfacial polymerization.

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Figure 1

2.3 Characterization of composite hollow fiber membranes

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The chemical characterization of composite hollow fiber membranes was

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accomplished by ATR-FTIR spectra (Bruker) at 600-4000 cm-1. The surface morphology of

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fiber surface and cross-section was examined by Scanning Electron Microscopy (SEM, S-

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4700, HITACHI). The complete dried sample fabrics were fractured by distilled water and

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refrigerated with liquid nitrogen. The thickness of all thin film selective layer was observed

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in Field-emission Transmission Electron Microscope (TEM) (JEOL, Japan, JEM-2100 TEM)

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at an accelerating voltage of 200 kV.

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Table 2 9

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2.4 Measurement of gas permeation The H2/CO mixture gas separation system was illustrated in Fig. 2. Experimental

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condition and mixture gas composition are listed in Table 3. The permselectivity was

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observed for operating pressure, change of feed flow rate and H2/CO mixture gas ratio

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(SAFETY GAS, Korea). Operating temperature was kept constant using air circulation inside

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the oven for balancing operating condition with hollow fiber module and feed gas flow. The

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permeate pressure was maintained at atmospheric pressure. The permeance and retentate gas

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flow rates were measured using bubble flow meter and H2, CO gases were analyzed by

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continuous gas analyzer (AO2020, ABB Inc., Germany). The gas permeance was calculated

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using following equation:

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P

QP (1) A  P

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where QP is the permeate flow rate through the membrane, △P is the gas pressure

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difference across the membrane, and A is the effective membrane area. Permeance units

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expressed as P = mol/(m2 s Pa) or cm3(STP/cm2 cmHg sec) in the SI system. However, it is

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more widely used and accepted for P is expressed in gas permeation units (GPU), where 1

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GPU = 1 x 10-6 cm3 (STP)/cm2 · cmHg · sec) (Yampolskii et al., 2006). H2/CO mixture gas

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permeance and selectivity can be determined by following equation (Peer et al., 2007).

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Pi 

Vi 1 1 1 A p f xi  pP yi

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(2)

(3)

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x is the logarithmic mean of feed and retentate compositions and is defined as follows:

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ln( xif / xir )

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where Pi is the permeance of component gas i (GPU) in the mixture. V is total

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permeate flow rate (cm3/sec) of component i, Pf is the fugacity of each component in the feed

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in eq. (2), PP is the permeate pressure (kPa), xif, xir are feed and retentate compositions of

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component i, respectively. The stage-cut is an important factor to determine the separation

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performance of the mixture gas, it is expressed as follows.

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stage cut( ) =

permeate side flow rate (ml/min) (5) total feeding flow rate (ml/min)

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The feed flow rate was showed by the sum of the permeate flow rate and retentate

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flow rate. Therefore, the feed flow rate was controlled by the retentate flow rate, and

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separation factor defined in mixture gas as follows:

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

[Ci / C j ] p [Ci / C j ]F

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where π is change of composition gas on feed and permeate side, Ci and Cj are

compositions of component i and j, respectively. F and P mean feed side and permeate side. Table 3 Figure 2

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2.5 Simulation of hollow fiber module process

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In the GTL process, not only H2/CO mixture gas ratio control but gas volume also is an

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important factor for amount of production. Therefore, the optimized H2/CO separation

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process simulated using multi stage. Gas separation is achieved by the gases having different

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permeability rate through the membrane. The analytical method of flow patterns in the

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module that are differentiated as mixed, plug, cross and cross-plug flow from the direction of

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permeate and rejected gas. In this paper on assumed that the plug-flow mode was simulated

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using MATLAB maintain the driving conditions of the counter-current flow. It is more

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favorable because of its ability to maintain a larger driving force (Krovvidi et al., 1992;

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Mccandless, 1990). Simulation conditions were based on the experiment results such as

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membrane area, each of the gas composition and gas flow rate that is permeated from

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permeate and the retentate side in actual module. The flux (Ji) can be calculated by the

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equation (7).

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J i  Pi ( p p xi  pr yi ), i  1, 2,..., n

(7)

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where, n is number of component, Pp and Pr are pressure of permeated gas on the permeate

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and retentate side Pi is permeace (m3m-2s-1kPa) of component i, and then equation (8) to (11)

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showed the mass transfer equations on the flow rate QP, QR and compositions xi, yi on

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permeate and retentate streams. Ji and Jj are showed flux (m3m-2s-1) of component i and j flux

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(m3m-2s-1). The pressure on the retentate stream assumed that Equation (12) i.e. Hagen-

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Poiseuille equation.

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dQR n   D0  i 1 J i dz

(8)

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(9)

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dQP n   D0  i 1 J i dz

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dxi dz

  D0 ( J i  x  i 1 J j ), i  1, 2,..., n  1 n

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QP

dy i dz

  D0 ( J i  y  i 1 J j ), i  1, 2,..., n  1 n

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dp 32  128 L   2 dz Di  Di 4

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(12)

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(10)

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where, Di and Do are the inside and outside diameters (m) of the hollow fiber membrane,

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respectively. μ is the viscosity of the mixed gas (kPa•s). υ and z are showed average velocity

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(m/s) of the retentate flow and inlet distance (m). About the simulation modeling our previous

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results showed in more details (Kim et al., 2013).

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3. Results and Discussion

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3.1 ATR-FTIR analysis

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The IR spectrum of composite membranes is listed in Fig. 3 (prepared by CHMA-

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TMC monomers). It shows a strong amide-I band at 1648 cm−1 which is the characteristic of

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the C=O stretching vibrations of the amide group. A strong characteristic amide-II band, 13

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which arises from the couplings of in-plane N-H bending and C-N stretching vibrations of the

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C-N-H group is observed at 1546 cm−1. These two bands (amide-I and amide-II) are

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characteristic for amides because of their constant position and strong intensities. The amide-

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II band splits into a multiplet, with peak positions at 1576, 1550, and 1545 cm−1. The split in

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amide-II band is caused by the difference in the dipoles of C-N bond of C(=O)-N-H and

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C(=O)-N- groups. It is well known that the ν(C=O) frequency shifts with the functional group

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that bonds directly to the carbon atom. Electron withdrawing substituents cause an

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electrostatic stabilization of the C=O group and a shift of the C=O frequency to higher values,

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while electron donating substituents destabilize the C=O group. In addition, the 2975 and

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2852 cm-1 peaks represented the asymmetric and symmetric stretching vibrations of the C-H

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bonds. The broad peak around 3200~3300 cm-1 is the O-H peak observed after oxidation of

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unreacted TMC.

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Figure 3

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3.2 SEM and TEM analysis results The morphology of composite membranes was observed in scanning electron

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microscope. Fig. 4 displays the effect of monomer concentration on thickness of TFC

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membranes. In the Fig. 4, The A showed characterization of PES substrate. B, C, D showed

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thickness of membrane prepared with different CHMA concentrations, and E, D, F showed

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that with different TMC concentrations. The surface thickness increases with increasing of

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monomer concentration. Therefore, increased aqueous phase monomer contributed increasing

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surface thickness by diffuse with organic phase monomer (Yu et al., 2010). According to the 14

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studies about the effect of organic phase monomer on gas permeance (Wang et al., 2013; Yu

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et al., 2010; Chai et al., 1994), the organic phase also increased thickness as the monomer

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concentration increased as shown in Fig. 4.

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Transmission electron microscopy (TEM) is highly significant technique to visualize

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the internal structure of thin layer of membranes due to its high-resolution power and

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possibility to achieve contrast between the areas having different chemical structure. TEM

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images of all TFC membranes are shown in Fig. 5. The thicknesses of all TFC membranes

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after interfacial polymerization are measured. According to the concentrations of monomers

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for thin film coating preparation the thickness show a discrepancy and it is confirmed by

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SEM as well as TEM analysis. There is little bit variation in the SEM and TEM thickness

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values because of in TEM, due to its high-resolution power after the post treatment of PES

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fiber there is some changes occurs on the surface of substrate membrane. However in TEM

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analysis that layer also looks like separate layer and is also measured so there is little

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variation in between TEM and SEM measured thickness values. The darker part of the skin is

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almost as thin as in the original membrane and no penetration of the pores of the support by

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the polymer is observed (Ingole et al., 2012; 2014). The micrograph shows that the amide

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dominated interlayer fills the cavities of the polyethersulfone supported hollow fiber

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membranes and largely varies in thickness. Fig. 5A-E shows the cross-sections of modified

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samples of TFC membranes.

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Figure 4 Figure 5

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3.3 Effects of aqueous phase monomer concentrations and retantate flow rates on stage-

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cut and permeance Figure 6 shows the effects of aqueous phase monomer concentrations and retentate

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flow rates on stage-cut and permeance. The experimental tests were performed using a

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mixture gas containing 75% (vol.) Hydrogen and 25% (vol.) Carbon monoxide. The

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operating pressure and temperature were 2 kgf/cm2 and 30 °C respectively. All modules were

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prepared under the same condition as organic monomer concentration (0.5 wt.%) and reaction

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time (5 min) with different concentration of aqueous phase monomers. As a result, according

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to the increase of aqueous monomer concentration, permeance of H2/CO gas mixture is

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decreases. The concentration of aqueous monomer affects the degree of cross-linking. The

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increased group of carboxylate and ether oxygen affects on the membrane permeance.

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However, when the concentration of aqueous monomer increased, the permeance decreased.

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The increment of aqueous monomer has a fast rate of polymerization (Liu et al., 2011; Wang

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et al., 2013). The stage-cut was controlled by retentate side flow rate using back pressure

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regulator. The stage cut decreased when the retentate flow rate increased under the same

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operating condition. Stage-cut is related with gas residence time in the module. Therefore, it

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is determined that permeance and selectivity of membrane is controlled by stage cut.

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Figure 6

Figure SI2 shows the H2/CO selectivity of the mixture gas as function of the H2

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permeance and aqueous phase monomer concentration. The increase of aqueous solution

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concentration caused reduction of permeance by the increase active layer thickness. H2/CO

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mixture gas selectivity was increased by increasing the aqueous phase solution concentration. 16

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In the Fig. 4, it showed an increasing active layer thickness 278, 313, 345 µm respectively.

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The aqueous phase monomer was momentary reacted with the organic monomer and the high

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solution concentration contributes to increase the thickness of active layer through the

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diffusion. It is reported that the high concentration of aqueous monomer enhance the degree

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of cross-linking because the almost chloride groups become amide groups in a fully cross-

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linked (Liu et al., 2011).

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3.4 Effects of organic phase monomer concentrations and retantate flow rates on stage-

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cut and gas permeance

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The different concentrations of TMC solutions were used as organic phase monomer

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to cross-link with CHMA to form a thin film composite layer on the PES substrate. The

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concentration of CHMA was fixed as 2.0 wt.% and TMC concentrations were changed as 0.1,

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0.5 and 0.75 wt.% respectively. TMC concentrations also affect the thickness of active TFC

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layer and the degree of cross-linking. Fig. 7 presents the effect of organic phase monomer

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concentration and retentate flow rate on stage-cut and permeance and Fig. SI3 shows H2/CO

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selectivity at H2/CO 3:1 ratio. As a result, the permeance of the membrane made from 0.1

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wt.% TMC is almost similar to that from 2.0 wt.%. When 0.75 wt.% concentration of TMC

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was used, the high permeance was obtained. Because polymerization reaction occurs rapidly

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at high concentration of TMC resulting in thick and defect free selective layer of composite

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membrane. It is well known that the defect free selective layer exhibits high permeance.

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However, in the case of H2/CO selectivity, the increased TMC concentration showed a rising

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trend until 0.75% it is due to most of carbonyl group of TMC was reacted with amine group

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of CHMA to form a dense membrane. Therefore, it shows higher selectivity compare to other

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membranes.

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3.5 Effects of operating pressure and gas ratio on mixed gas permeation

Figure 8 shows the results of binary H2/CO mixtures gas separation. It was tested at

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H2 and CO gas ratio of 3:1 using entry 1 module (CHMA and TMC 0.5 wt.%) and the module

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shows high permeability. Operating temperature maintained at 30 °C, and pressure difference

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was between 1-5 kgf/cm2, and retentate side flow rate was controlled at 300-1200 mL/min.

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The increased operating pressure presented increasing stage-cut as same retentate flow rate.

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When the operating pressure increased at same retentate flow rate condition, the permeance

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increased up to 10 GPU by increasing driving force. However, these changes of operating

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conditions show difference in permeability and separation behavior because of the control of

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operating pressure and stage cut influenced driving force in the membrane process. The

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stage-cut and operating pressure relate with permeability. Therefore, when the stage-cut

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decreased, retentate flow rate increased at same operating pressure. At the same retantate flow,

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when the stage-cut increased, the operating pressure also increased.

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Figure11 showed about selectivity of H2/CO gas in mixture gas for effect of the

19

monomer concentration and Fig. 8 and 9 described about separation factor, because the

20

separation factors represent actual performance and relate to the operating conditions of

21

membrane modules. Therefore, some parameters of feed flow rate and operating pressure,

22

stage-cut, and the mixture composition are important for the separation factor (Choi et al., 18

Page 17 of 39

2010). Fig. 9 showed separation factor of Fig. 8 experiment results. Separation factor

2

indicated fast gas permeation rate relatively on the concentration difference of feed side and

3

the permeate side in mixture gas. The increased operating pressure represented a large

4

separation factor. As expected, with increasing operating pressure, separation factor increased.

5

However, the value of separation factor was decreased according to the operation pressure,

6

because the competitive sorption occurred in the glass polymer during the mixture gas

7

separation. In the glass polymer, competitive sorption was associated to the non-equilibrium

8

excess volume. The limited available sorption site was competitive and the adsorption of H2

9

component lowered due to the presence of the CO component (Choi et al., 2010). Therefore,

10

when the operating pressure increased, CO permeance also increased and effect of

11

competitive sorption to make the hydrogen permeance decreased and increment of separation

12

factor decreased (Peer et al., 2007).

15

cr

us

an

M

d te

14

Figure 8 Figure 9

Ac ce p

13

ip t

1

Figure 10 represented the effect of H2/CO various gas ratio on separation factor and

16

permeance. At operating pressure 2 kgf/cm2, operating temperature maintained at 30 °C and

17

H2/CO Gas ratio changed at 3:1, 5:1 and 7:1 respectively using the hollow fiber membrane

18

module M1. As a result, the permeances of mixed gas increase when the H2/CO ratio

19

increased because H2 has high permeance than CO. Therefore, the increase of H2/CO gas

20

ratio means high permeance and separation factor at same stage-cut condition. However, in

21

the H2/CO separation process (applied in GTL process), increasing H2 gas concentration

22

required more membrane area to meet the target gas ratio (H2/CO ratio 2:1 control) at 19

Page 18 of 39

retentate side, because the higher stage-cut is, the more increased gas permeance is at same

2

membrane area. Therefore, it is possible to reduce stage-cut for H2/CO gas ratio control,

3

when the increased membrane area reduced each gas throughout.

4

Figure 10 3.6 Multi stage membrane separation process

cr

5

ip t

1

The simulation result of multistage membrane process is illustrated in Figure 11.

7

Operating condition of process estimated, operating temperature was maintained at 30 °C,

8

and pressure at 2 kgf/cm2. H2/CO gas ratio of feed and retentate stream was assumed to be

9

3:1 and 2:1 ratio as continuous flow. Hollow fiber modules arranged with minimized

10

membrane area for the optimized process operation to increase production of syngas by gas

11

ratio and volume control. In the Fig. 11, multi stage process was design using the two

12

modules. H2/CO mixture gas (Lf) was fed to S1 from where the permeate gas was directly fed

13

to S2. H2/CO gas concentration of R1 and R2 is kept at 2:1 ratio, each gas’s concentration is

14

showed in P1and P2. In the single-state, H2 and CO concentration was 85.5% and 14.5% and

15

while multi-stage simulation showed 91% and 1.98% of H2/CO concentration respectively. In

16

the previous experiment results as of Fig. 10, as increased H2/CO ratio of feed gas meant an

17

increased stage-cut on the same membrane area, which requires a certain amount of

18

membrane area to control the value R2. As a result, simulation process has been designed.

19

The membrane area increased 0.30, 0.21 m2 on M1 and M2 respectively, when the feed flow

20

rate is 5 L/min. The retantate flow rate of R1 is 2.54 L/min and R2 showed 0.56 L/min on

21

single and multi-stage respectively.

22

Ac ce p

te

d

M

an

us

6

Figure 11 20

Page 19 of 39

1

4. Conclusion In this study, various hollow fiber membrane modules were prepared with the PES

3

substrate using interfacial polymerization method to make a thin-film composite membrane.

4

These modules were used for the separation of H2/CO mixture gas and H2/CO ratio can be

5

controlled by optimization. The composite membranes were produced by CHMA as aqueous

6

phase monomer and TMC as organic phase monomer. The characteristic parameters of TFC

7

membranes were measured by SEM and FT-IR for morphology and functional group

8

characterization. These membrane modules were used to evaluate mixture gas permeance and

9

selectivity with different concentrations of monomers. Membrane process was designed for

an

us

cr

ip t

2

10

the optimization according to the operating condition difference.

11

separation performance depending on the various condition of permeance and stage-cut,

12

operating pressure, separation factor and the concentration ratio of the H2/CO mixture gas

13

respectively. As a result, appropriate concentration of aqueous and organic monomer shows

14

high effect on separation selectivity and permeability on the H2/CO mixture gas separation.

15

The increasing operating pressure and stage-cut led to increase separation factor. The process

16

is designed for the more products obtained on retentate side using multi-stage from increased

17

gas ratio on permeate side as membrane area.

19

M

d

te

Ac ce p

18

The results show

Acknowledgements

20

This work was supported by the Korea Institute of Energy Technology Evaluation

21

and Planning (KETEP) under the ‘‘Energy Efficiency & Resources Programs’’ (Project No.

22

2013201020178A) of the Ministry of Knowledge Economy, Republic of Korea. 21

Page 20 of 39

A

effective membrane area (m2)

3

Ci

concentration of i component

4

Di

inside diameter of hollow fiber membrane (m)

5

Do

outside diamante of hollow fiber membrane (m)

6

J

flux (m3/m2 s)

7

P

permeance (GPU)

8

QP

permeate flow rate (m3/s)

9

QR

retentate flow rate (m3/s)

10

lm

effective length of hollow fiber membrane (m)

11

V

total permeate flow rate (cm3/sec)

12

n

13

p

14

t

15

xi

16

yi

composition of component i on retentate stream

17

zi

composition of component i on feed stream

ip t

2

cr

Nomenclature

Ac ce p

te

d

M

an

us

1

number of component pressure (kPa)

average velocity (m/s)

composition of component i on permeate stream

22

Page 21 of 39

z

distance from inlet of module (m)

2

υ

viscosity of mixed gas (kPa s)

3

θ

separation factor

ip t

1

cr

4

Reference

6

Atersenasberg-Petersen, K., Bak Hansen, J.H., Christensen, T.S., Dybkjaer, I., Seier

7

Christensen, P., Stub Nielsen, C., Winter Madsen, S.E.L., Rostrup-Nielsen, J.R., 2001.

8

Technologies for large-scale gas conversion. App. Cat. 221, 379-387.

9

Bian, G., Nanda, T., Koizumi, N., Yamada, M., 2002. Changes in microstructure of reduced

10

cobalt catalyst during performing FT synthesis from syngas determined by in situ high-

11

pressure syngas adsorption. J. Mol. Cat. A-Chem. 178, 219-228.

12

Buch, P., Mohan, D., Reddy, A., 2008. Preparatin, characterization and chlorine stability of

13

aromatic-cycloaliphatic polyamide thin film composite membranes. J. Membr. Sci. 309, 36-

14

44.

15

Chai, G.Y., Krantz, W.B., 1994. Formation and characterization of polyamide membranes via

16

interfacial polymerization. J. Membr. Sci. 93, 175-192.

17

Choi, S. H., Brunetti, A., Drioli, E., Barbieri, G., 2010. H2 separation from H2/N2 and H2/CO

18

mixtures with co-polyimide hollow fiber module. Sep. Sci. Technol. 46, 1-13.

19

Chung, T.S., Teoh, S.K., Hu, X., 1997. Formation of ultrathin high-performance

Ac ce p

te

d

M

an

us

5

23

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polyethersulfone hollow-fiber membranes, J. Membr. Sci. 133, 161-175.

2

David, O.C., Gorri, D., Nijmeijer, K., Ortiz, I., Urtiaga, A., 2012. Hydrogen separation from

3

multicomponent gas mixures containing CO, N2, and CO2 using Matrimid asymmetric hollow

4

fiber membrane. J. Membr. Sci. 419-420, 49-56.

5

David, O.C., Gorri, D., Ortiz, I., Urtiaga, A., 2012. Mixed gas separation study for the

6

hydrogen recovery from H2/CO/N2/CO2 past combustion mixtures using a matrimid. J.

7

Membr. Sci. 378 359-368.

8

Golden Rules for a Golden Age of Gas, (2012). A Special Report Published by the IEA.

9

Ingole, P.G., Bajaj, H.C., Singh, K., 2012. Optical resolution of racemic lysine

10

monohydrochloride by novel enantioselective thin film composite membrane. Desalination

11

305, 54-63.

12

Ingole, P.G., Kim, K.H., Park, C.H., Choi, W.K., Lee, H.K., 2014. Preparation, modification

13

and characterization of polymeric hollow fiber membranes for pressure retarded osmosis.

14

RSC Adv. 4, 51430-51439.

15

Kim, K.H., Baik, K.J., Kim, I.K., Lee, H.K., 2012. Optimization of membrane process for

16

methane recovery from biogas, Sep. Sci. Technol. 47, 963-971.

17

Kim, K.H., Ingole, P.G., Kim, J.H., Lee, H.K., 2013. Separation performance of PEBAX. PEI

18

hollow fiber composite membrane for SO2/CO2.N2/ mixed gas. Chem. Eng J. 233, 242-250.

19

Koros, W.L., Fleming, G.K., 1993. Membrane based gas separation. J. Membr. Sci. 83, 1-80.

20

Krovvidi, K.R., Kovvali, A.S., Vemury, S., Khan, A.A., 1992. Approximate solutions for gas

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an

us

cr

ip t

1

24

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permeators separating binary mixtures. J. Membr. Sci. 66, 103-118.

2

Lee, Y.J., Hong, S.I., Moon, D.J., 2011. Studies on the steam and CO2 reforming of methane

3

for GTL-FPSO applications. Catal. Tod. 174, 31-36.

4

Liu, Y., He, B.Q., Li, J.X., Sanderson, R. D., Li, L., Zhang, S.B., 2011. Formation and

5

structural evolution of biphenyl polyamide thin film on hollow fiber membrane during

6

interfacial polymerization. J. Membr. Sci. 373, 98-106.

7

Loeb, S., Sourirajan, S., 1963. Sea water demineralization by means of an osmotic membrane.

8

Adv. Chem. Ser. 38, 117-132.

9

Marban, G., Valdes-Solis, T., 2007. Towards the hydrogen economy. J. Hydro. Ene. 32, 1625-

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us

cr

ip t

1

1637

11

Mccandless, F.P., 1990. Iterative solutions of multicomponent permeator model equations. J.

12

Membr. Sci. 48, 115-122.

13

Morgan. P.W., 1965. Condensation polymers: By interfacial and solution methods. In Polym.

14

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15

Mulder, M., 1996. Basic principles of membrane technology. Kluwer Academic Publishers,

16

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17

Park, D., Moon, D.J., Kim, T., 2014. Preparation and evaluation of a metallic form catalyst

18

for steam-CO2 reforming of methane in GTL-FPSO process. Fuel Proc. Technol. 124, 91-103.

19

Park, H.H., Deshwal, B.R., Kim, I.W., Lee, H.K., 2008. Absorption of SO2 from flue gas

20

using PVDF hollow fiber membranes in a gas-liquid contactor. J. Membr. Sci. 319, 29-37.

Ac ce p

te

d

M

10

25

Page 24 of 39

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2

from carbon monoxide using a hollow fiber polyimide membrane: experimental and

3

simulation. Chem. Eng. Technol. 30, 1418-1425.

4

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5

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6

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7

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8

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9

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an

us

cr

ip t

1

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11

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12

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13

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14

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15

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16

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17

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18

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19

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20

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21

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te

d

M

10

26

Page 25 of 39

Yu, X.W., Wang, Z., Wei, Z.H., Yuan, S.J., Zhao, J., Wang, J.X., 2010. Novel tertiary amino

2

containing thin film composite membranes prepared by interfacial polymerization for CO2

3

capture. J. Membr. Sci. 362, 265-278.

ip t

1

Ac ce p

te

d

M

an

us

cr

4

27

Page 26 of 39

Table Captions

2

Table 1 Composition of dope solution and spinning condition for preparation of PES hollow

3

fiber membrane.

4

Table 2 Composition of aqueous and organic solutions and reaction times used for the

5

preparation of selective layer.

6

Table 3 Experimental condition for mixture gas separation.

cr

ip t

1

us

7 8

an

10

Table 1 Composition of dope solution and spinning condition for preparation of PES hollow fiber membrane.

M

9

Composition

d

PES

77.0 wt.% 5.0 wt.%

Ac ce p

LiCl

te

NMP

18.0 wt.%

Spinning condition

11

Air gap

0 cm

Spinneret ID/OD

0.16/0.9 mm

Internal coagulant

D. I. water

12 13 14 28

Page 27 of 39

1

Table 2 Composition of aqueous and organic solutions and reaction times used for the

3

preparation of selective layer.

6 7 8 9

Reaction time (min)

TMC

(%w/w)

(%w/v) 0.5

5

0.5

5

0.5

5

0.1

5

0.5

5

0.75

5

0.5

M2

CHMA 1.0

1.0

M3

CHMA 2.0

2.0

M4

TMC 0.1

2.0

M5

TMC 0.5

2.0

M6

TMC 0.75

us

CHMA 0.5

M

M1

d

2.0

cr

CHMA

te

5

composition

Ac ce p

4

Membrane

an

Entry

ip t

2

10 11

12 29

Page 28 of 39

1 2

Table 3 Experimental condition for mixture gas separation.

300 / 600 / 900 / 1200 ml/min

cr

Controlled retentate flow rate

ip t

Experimental condition

1/ 2 / 3 / 4 / 5 kgf/cm2

Operating temperature

30 °C

us

Operating pressure

an

H2/CO mixture gas composition H2/CO ratio

3:1 / 5:1 / 7:1

M

3

Ac ce p

te

d

4

30

Page 29 of 39

Figure 1: Structure of polyamide skin layer formed by interfacial polymerization of CHMA

2

with TMC.

3

Figure 2: Schematic diagram of gas permeation experiment apparatus.

4

Figure 3: FT-IR results of composite membranes using different monomer concentrations.

5

Figure 4: SEM images of membrane cross section ([A] without coating (substrate), [B]-[D]

6

aqueous phase concentration of 0.5, 1.0, 2.0 wt.%, [E],[F] organic phase concentration of 0.1,

7

0.75 wt.% respectively ([B], TMC 0.5 wt.%)).

8

Figure 5: TEM images of membrane cross section, [A]-[C] aqueous phase concentration of

9

0.5, 1.0, 2.0 wt.%, [D],[E] organic phase concentration of 0.1, 0.75 wt.% respectively ([A],

an

us

cr

ip t

1

TMC 0.5 wt.%)).

11

Figure 6: Effect of aqueous monomer concentration and retantate flow rate on stage-cut and

12

permeance. (H2/CO=3:1 ratio, 2kgf/cm2, 30 °C)

13

Figure 7: Effect of organic monomer concentration and retantate flow rate on stage-cut and

14

permeance. (H2/CO=3:1 ratio, 2kgf/cm2, 30℃)

15

Figure 8: Effect of operating pressure and retantate flow rate on stage-cut and permeance.

16

Figure 9: Effect of operating pressure and stage-cut on separating factor.

Ac ce p

te

d

M

10

31

Page 30 of 39

Figure 10: Effect of H2/CO ration and stage-cut on permeance and separation factor at

2

2kgf/cm2.

3

Figure 11: Result of multi-stage process separation process simulation.

ip t

1

4

NH2 +

H O N C

an

M

H O N C

O C

CONH

*

NH

COOH

*

te

O C H N

H O N C

d

O H C N

Cl

Trimesoyl Chloride

IP O C

O

Cl

1,3-cyclohexanebis methylamine (CHMA)

*

O

cr

H2 N

Cl

us

O

5 6

Ac ce p

C O

*

n

n

7

Figure 1: Structure of polyamide skin layer formed by interfacial polymerization of CHMA

8

with TMC.

9 10 11

32

Page 31 of 39

ip t cr us an

1

te

d

M

Figure 2: Schematic diagram of gas permeation experiment apparatus

Ac ce p

2

33

Page 32 of 39

ip t cr us an M d te 2

Ac ce p

1

Figure 3: FT-IR results of composite membranes using different monomer concentrations.

34

Page 33 of 39

ip t cr us an M d te Ac ce p

1 2

Figure 4: SEM images of membrane cross section ([A] without coating (substrate), [B]-[D]

3

aqueous phase concentration of 0.5, 1.0, 2.0 wt.%, [E],[F] organic phase concentration of 0.1,

4

0.75 wt.% respectively ([B], TMC 0.5 wt.%)).

5

35

Page 34 of 39

ip t cr us an M d te Ac ce p

1 2

Figure 5: TEM images of membrane cross section, [A]-[C] aqueous phase concentration of

3

0.5, 1.0, 2.0 wt.%, [D],[E] organic phase concentration of 0.1, 0.75 wt.% respectively ([A],

4

TMC 0.5 wt.%)).

5 6

36

Page 35 of 39

CHMA 0.5 wt% CHMA 1.0 wt% CHMA 2.0 wt% 180

0.9

160

0.8

140 120

0.6

100

0.5

80

cr

Stage-cut

0.7

0.4

60 40

us

0.3 0.2

400

600

800

an

0.1 0.0 200

Permeance (GPU)

ip t

1.0

1000

1200

20 0

-20 1400

Retentate flow rate (ml/min)

2

Figure 6: Effect of aqueous monomer concentration and retantate flow rate on stage-cut and

3

permeance. (H2/CO=3:1 ratio, 2kgf/cm2, 30 °C)

d

M

1

Stage-cut

0.12

30

0.10

25

0.08

20

0.06

15

0.04

10

0.02

5

0.00 400

4

600

800

1000

1200

Permeance (GPU)

35

Ac ce p

0.14

te

TMC 0.1 wt% TMC 0.5 wt% TMC 0.75 wt%

0 1400

Retentate flow rate (ml/min)

37

Page 36 of 39

Figure 7: Effect of organic monomer concentration and retantate flow rate on stage-cut and

2

permeance. (H2/CO=3:1 ratio, 2kgf/cm2, 30℃)

1.2

160 140

d

Ac ce p

0.2

0.0 200

4

180

120 0.6

0.4

3

M

0.8

100

te

Stage-cut

1.0

200

400

Permeance (GPU)

us

1 kgf/cm2 2 kgf/cm2 3 kgf/cm2 4 kgf/cm2 5 kgf/cm2

an

1.4

cr

ip t

1

80 60

600

800

1000

1200

1400

Retentate flow rate (ml/min)

Figure 8: Effect of operating pressure and retantate flow rate on stage-cut and permeance.

38

Page 37 of 39

2.6 1 kgf/cm2 2 2 kgf/cm 3 kgf/cm2 2 4 kgf/cm 5 kgf/cm2

ip t

cr

2.2

2.0

us

Separation factor

2.4

1.6 0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

Stage-cut

M

1

Figure 9: Effect of operating pressure and stage-cut on separating factor.

d

2.6

te

400

H2:CO=5:1 H2:CO=7:1

Permeance (GPU)

Ac ce p

350

H2:CO=3:1

300

2.4

2.2

250

2.0

200

Separation factor

2

an

1.8

1.8

150 1.6 100 0.10

3

0.15

0.20

0.25

0.30

0.35

0.40

0.45

0.50

Stage-cut 39

Page 38 of 39

Figure 10: Effect of H2/CO ration and stage-cut on permeance and separation factor at

2

2kgf/cm2.

5

te

4

Figure 11: Result of multi-stage process separation process simulation.

Ac ce p

3

d

M

an

us

cr

ip t

1

40

Page 39 of 39