Article pubs.acs.org/EF
Deep Eutectic Solvents As Tuning Media Dissolving Cu+ Used in Facilitated Transport Supported Liquid Membrane for Ethylene/ Ethane Separation Rong Deng,† Yongli Sun,*,† Hanrong Bi,† Haozhen Dou,† Huawei Yang,† Baoyu Wang,† Wenjun Tao,† and Bin Jiang† †
School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072, People’s Republic of China S Supporting Information *
ABSTRACT: In the petrochemical industry, it is critical to separate the light olefins/paraffins mixtures via an efficient and economic method. In this work, a series of deep eutectic solvents (DESs) (choline chloride (ChCl)-glycerol (G), ChCl-ethylene glycol (EG), 1-butyl-3-methylimidazolium chloride ([Bmim][Cl])-G, and [Bmim][Cl]-EG) dissolving CuCl were used as novel membrane liquids to fabricate supported liquid membranes (SLMs) for the C2H4/C2H6 mixture separation. Interactions based on a hydrogen bond network in different DESs were characterized by time-of-flight mass spectroscopy (TOF-MS), nuclear magnetic resonance (1H NMR), and Fourier transform infrared (FT-IR) spectroscopy. Moreover, by absorption experiments, the Cu+ activity was quantitatively described based on a first-order equilibrium model. The effects of DESs species, CuCl concentration, transmembrane pressure, temperature, and time on separation performances were investigated by C2H4/C2H6 mixture permeation experiments. CuCl/ChCl-EG-based SLMs possessed good permeability and comparable permslectivity, as well as good long-term stability, surpassing the reported polymeric membrane upper bound. Systemic study demonstrated that the strength of the hydrogen bond networks in DESs could be tailored by optimizing the combinations of the HBAs and HBDs, and eventually improved the separation performances of the CuCl/DES-based SLMs.
1. INTRODUCTION Light olefins, such as ethylene, are essential building blocks for many products and chemicals in the petrochemical industry.1 Light olefins are primarily produced via the pyrolysis or catalytic cracking of the crude oil component, such as naphtha and gas oil. In addition, a significant amount of the light olefins produced during the refining of crude oil is used as refinery fuel.2,3 Among the mentioned process, the olefins usually exists as the olefins/parraffins mixtures, so the separation technology is critical to enhance the utilization efficiency of light olefins.4−6 Unfortunately, because of the low boiling points and the close relative volatilities of the light olefin and paraffin species, especially with the similar carbon numbers, traditional cryogenic distillation technology requires huge capital and energy cost, such as the very low operational temperature and the numerous trays.7 Therefore, many researchers were devoted to finding novel, efficient, and economic olefins/paraffins separation methods, such as membrane distillation,8,9 metal−organic frameworks adsorbent,10,11 ionic liquid absorption,12−14 cross-linkable membranes,15,16 polymer electrolyte membranes,17,18 supported liquid membranes,19−21 and so on. Among all the meaningful attempts, supported liquid membranes (SLMs) based on facilitated transport mechanism are believed to be promising technologies. These facilitated transport membranes incorporate mobile liquid media containing specific chemical carriers which can selectively and reversibly react with target gases.21,22 As a result, their permeation and selectivity of the target gases are higher than the conventional polymeric membranes with low diffusivity and inert absorptivity.7 © XXXX American Chemical Society
However, the permeation performance of this membrane deteriorates with evaporation of the membrane liquid. To circumvent the problem, ionic liquids (ILs), which are a class of room-temperature molten salts with negligible vapor pressure, high stability, and designable structure were introduced to prepare the supported ionic liquid membranes (SILMs).23−25 Although many researchers demonstrated the potential of SLMs to separate the olefins/paraffins, their practical applications were somewhat confined, because of the low efficiency for the carrier, as well as high cost for facilitated transport media. Deep eutectic solvent (DES) is a novel class of functional green solvents, constructed from a eutectic mixture of hydrogen-bond acceptor (HBA) and hydrogen-bond donor (HBD). DESs have some analogous properties with ILs, such as negligible vapor pressure as well as designable structure, but their preparations are more convenient and economical, from both environmental and atomic standpoints.26 Thus, DESs have been widely used in the areas of separation, reaction, and electrochemistry.27−31 Moreover, the typical existence of hydrogen bond network in DESs brings about some interesting physical and chemical properties.32,33 Related studies have indicated that DES systems possess high metal compound solubility and high reaction activity, which seemed to be ideal media for the SLMs.34−36 Received: May 6, 2017 Revised: August 26, 2017
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DOI: 10.1021/acs.energyfuels.7b01305 Energy Fuels XXXX, XXX, XXX−XXX
Article
Energy & Fuels
Hydranal-water standard (1.00 mg/g). This standard was supplied in glass ampules from Sigma−Aldrich (Malaysia). 2.2. Preparation of CuCl/DES-Based SLMs. CuCl/DES-based SLMs were prepared using a membrane permeation apparatus (Figure 2, presented later in this paper) as follows. First of all, the nylon microfiltration membranes were applied under vacuum (
