Upgrading of Total Isomerization Processes with Metal-Organic Frameworks

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Separation of Branched Alkane Feeds with Metal-Organic Frameworks

Publication . Henrique, Adriano; Brântuas, Pedro; Zafanelli, Lucas F.A.S.; Aly, Ezzeldin; Rodrigues, Alírio; Maurin, Guillaume; Serre, Christian; Silva, José A.C.

The production of high-quality gasoline is currently achieved through the Total Isomerization Process that separates n/iso-paraffins in the pentane (C5) and hexane (C6) range while not reaching the ultimate goal of a research octane number (RON) higher than 92. This work demonstrates two promising alternatives/strategies using metal-organic frameworks (MOF) that lead to a novel adsorptive separation process to overcome this limitation. Here, the efficient discrimination of C5/C6 alkane isomers into valuable fractions of high RON (HRON – 2,3-dimethylbutane (23DMB; RON 105), 2,2-dimethylbutane (22DMB; RON 94), and isopentane (iC5; RON 93.5)) and low RON (LRON – n-pentane (nC5; RON 61.7), (nC6; RON 30), 2-methylpentane (2MP; RON 74.5), and 3-methylpentane (3MP; RON 75.5)) compounds is achieved.

2024Conference object

Open access

Separation of branched alkanes feeds by a synergistic action of zeolite and metal-organic framework

Publication . Brântuas, Pedro; Henrique, Adriano; Wahiduzzaman, Mohammad; Wedelstedt, Alexander von; Maity, Tanmoy; Rodrigues, Alírio; Nouar, Farid; Lee, U-Hwang; Cho, Kyung Ho; Silva, José A.C.; Serre, Christian; Maurin, Guillaume

Zeolites and metal-organic frameworks (MOFs) are considered as “competitors” for new separation processes. The production of high-quality gasoline is currently achieved through the total isomerization process that separates pentane and hexane isomers while not reaching the ultimate goal of a research octane number (RON) higher than 92. This work demonstrates how a synergistic action of the zeolite 5A and the MIL-160(Al) MOF leads to a novel adsorptive process for octane upgrading of gasoline through an efficient separation of isomers. This innovative mixed-bed adsorbent strategy encompasses a thermodynamically driven separation of hexane isomers according to the degree of branching by MIL-160(Al) coupled to a steric rejection of linear isomers by the molecular sieve zeolite 5A. Their adsorptive separation ability is further evaluated under real conditions by sorption breakthrough and continuous cyclic experiments with a mixed bed of shaped adsorbents. Remarkably, at the industrially relevant temperature of 423 K, an ideal sorption hierarchy of low RON over high RON alkanes is achieved, i.e., n-hexane ≫n-pentane ≫2-methylpentane > 3-methylpentane⋙ 2,3-dimethylbutane > isopentane ≈ 2,2-dimethylbutane, together with a productivity of 1.14 mol dm−3 and a high RON of 92, which is a leap-forward compared with existing processes.

2022Journal article

Open access

A microporous multi‐cage metal–organic framework for an effective one‐step separation of branched alkanes feeds

Publication . Zhou, Lin; Brântuas, Pedro; Henrique, Adriano; Reinsch, Helge; Wahiduzzaman, Mohammad; Grenèche, Jean‐Marc; Rodrigues, Alírio; Silva, José A.C.; Maurin, Guillaume; Serre, Christian

The improvement of the Total Isomerization Process (TIP) for the production of high-quality gasoline with the ultimate goal of reaching a Research Octane Number (RON) higher than 92 requires the use of specific sorbents to separate pentane and hexane isomers into classes of linear, mono- and di-branched isomers. Herein we report the design of a new multi-cage microporous Fe(III)-MOF (referred to as MIP-214, MIP stands for materials of the Institute of Porous Materials of Paris) with a flu-e topology, incorporating an asymmetric heterofunctional ditopic ligand, 4-pyrazolecarboxylic acid, that exhibits an appropriate microporous structure for a thermodynamic-controlled separation of hydrocarbon isomers. This MOF produced via a direct, scalable, and mild synthesis route was proven to encompass a unique separation of C5/C6 isomers by classes of low RON over high RON alkanes with a sorption hierarchy: (n-hexane >> n-pentane approximate to 2-methylpentane>3-methylpentane)(low RON)>>(2,3-dimethylbutane approximate to i-pentane approximate to 2,2-dimethylbutane)(high RON) following the adsorption enthalpy sequence. We reveal for the first time that a single sorbent can efficiently separate such a complex mixture of high RON di-branched hexane and mono-branched pentane isomers from their low RON counterparts, which is a major achievement reported so far.

2024Journal article

Open access

Separation of Hexane Isomers in ZIF-8 by Fixed Bed Adsorption

Publication . Henrique, Adriano; Rodrigues, Alírio; Silva, José A.C.

The performance of porous metal organic framework ZIF-8 in the separation of all five hexane isomers (nC6, 2MP, 3MP, 23DMB, 22DMB) is evaluated through a series of multicomponent breakthrough adsorption experiments, at the temperatures of 373, 423, and 473 K and up to total hexane isomers pressure of 0.5 bar. The reported data show for all experiments the following sorption hierarchy: nC6 ≫ 2MP > 3MP ≫ 23DMB > 22DMB. At the temperature of 373 K and total hydrocarbon pressure of 0.5 bar the mixture loading of hexane isomers can go up to 2.15 mol·kg-1. In addition, at the same temperature the selectivities measured by the ratio of the loadings between linear plus monobranched (nC6, 2MP, 3MP) relatively to the dibranched (23DMB, 22DMB) isomers range between 34-55. The results also show that the sorption of nC6 is equilibrium based in contrast with the sorption of branched isomers which is kinetically controlled. The dibranched isomer 22DMB is practically excluded from the framework followed closely by 23DMB. The adsorption equilibrium experimental data are modeled by the Sips isotherm and the breakthrough data are simulated through a mathematical model developed in Matlab code using the method of lines (MOL), the results being in qualitative agreement. From the numerical simulations it was found that diffusivity of the branched paraffins in ZIF-8 is 2 orders of magnitude lower than for the linear nC6, and that the diffusivity of the dibranched paraffins is three times lower than for the monobranched ones. This work shows that ZIF-8 has the ability to purely separate the linear nC6 from its branched isomers and partially separate mono- from dibranched isomers if proper experimental conditions are setup, the result being important for the octane upgrade of gasoline.

2019Journal article

Open access

Separation of branched alkanes feeds by a synergistic action of zeolite 5A and metal-organic framework MIL-160(Al)

Publication . Henrique, Adriano; Brântuas, Pedro; Zafanelli, Lucas F.A.S.; Aly, Ezzeldin; Rodrigues, Alírio; Maurin, Guillaume; Serre, Christian; Silva, José A.C.

The total isomerisation process (TIP) developed by the universal oil products (UOP) for upgrading the octane rating of light hydrocarbon fractions, especially mixed feedstocks containing pentane (C5) and hexane (C6) isomers, is among the first and most successful adsorption processes applied in the industry. Typically, the light naphtha, characterised by a low research octane number (RON, ≈70), undergoes an incomplete catalytic isomerisation that generates an effluent containing unconverted linear paraffins, mostly n-pentane (nC5; RON 61.7) and n-hexane (nC6; RON 30), mixed with their respective branched isomers, i.e., isopentane (iC5; RON 93.5), 2-methylpentane (2MP; RON 74.5), 3-methylpentane (3MP; RON 75.5), 2,2-dimethylbutane (22DMB; RON 94), and 2,3-dimethylbutane (23DMB; RON 105). After that, the output of the isomerisation reactor is fed into an adsorber packed with zeolite (LTA type) that behaves as a molecular sieve, adsorbing only the linear paraffins (which are then recycled to the catalytic reactor for further processing). This results in a final branched isomerate product with an average RON ≈87–90. However, with the actual TIP process, the monobranched hexanes 2MP and 3MP represent up to 30% of the final product composition, which is detrimental to the octane improvement of gasoline for RON values higher than 90. Accordingly, this work shows a novel adsorptive separation process, based on the synergistic action of the zeolite 5A and the MIL-160(Al) metal-organic framework (MOF), to efficiently fractionate C5/C6 alkane isomers according to classes of high RON (HRON – 22DMB, 23DMB, and iC5) and low RON (LRON – nC5, nC6, 2MP, and 3MP) compounds.

2024Conference object

Open access