Olefin Purification Research Articles

Optimizing olefin purification: An artificial intelligence-based process-conscious PI controller tuning for double dividing wall column distillation

This study investigates the light olefin separation using dual dividing wall columns (DWCs) and compares various proportional-integral (PI) controller tuning methods. A novel process-conscious reinforcement learning (RL) approach, utilizing Deep Deterministic Policy Gradient (DDPG), is developed by incorporating domain-specific knowledge into the reward function to ensure compliance with critical process variables and product purity. The DDPG-based PI tuning is evaluated against traditional methods such as Aspen’s recommended initial tuning, Ziegler-Nichols (ZN), and Cohen-Coon (CC). The result shows that the DDPG method significantly enhances control stability and accuracy, reducing error by factors of 11.9, 2.3, and 1.6 compared to Aspen, ZN, and CC, respectively. Additionally, DDPG demonstrates superior energy efficiency, consuming 13% less energy than the next best method. It also reduces purification costs by up to 13.5% and CO2 emissions by 20% compared to other methods. This study highlights the potential of integrating advanced RL techniques into industrial process control, delivering substantial improvements in stability, energy efficiency, economic, and environmental performance.

Leveraging Surface Chemistry and Pore Shape Engineering in a Metal‐Organic Framework for One‐Step Olefin Purification

AbstractPurifying olefin from ternary paraffin/olefin/alkyne mixtures through a one‐step adsorption process is extremely desirable. Herein, a stable zirconium(IV) metal‐organic framework with a customized pore surface composed of nonpolar phenyl and slightly polar thiophene rings is reported to access the adsorption preference of paraffin and alkyne over olefin. Noteworthily, this material displays a superior ability to discriminate C3 hydrocarbon molecules, which is principally more challenging compared with C2 ones and rarely documented. Computational studies disclose that its featured pore shape fits well with C3 gas molecules, enabling them to get close contact with the immobilized affinity sites. Leveraging surface chemistry and pore shape engineering synergistically gives rise to excellent C3 adsorption capacities (>5 mmol g−1) and concurrently high C3H8/C3H6 (1.4) and C3H4/C3H6 (1.9) selectivities (at 298 K and 1 atm). Dynamic column breakthrough experiments demonstrate that one‐step purification of C2H4 and C3H6 can be simultaneously realized on this material.

In Situ DRIFTS Analysis during Hydrogenation of 1-Pentyne and Olefin Purification with Ag Nanoparticles.

The catalytic performance of nanoparticles (NPs) of Ag anchored on different supports was evaluated during the selective hydrogenation of 1-pentyne and the purification of a mixture of 1-pentene/1-pentyne (70/30 vol %). The catalysts were identified: Ag/Al (Ag supported on ɣ-Al2 O3 ), Ag/Al-Mg (Ag supported on ɣ-Al2 O3 modified with Mg), Ag/Ca (Ag supported on CaCO3 ) and Ag/RX3 (Ag supported on activated carbon-type: RX3). In addition, in situ DRIFTS analysis of 1-pentyne adsorption on each support, catalyst, and 1-pentyne hydrogenation were investigated. The results showed that the synthesized catalysts were active and very selective (≥85 %) for obtaining the desired product (1-pentene). Different adsorbed species (-C≡C- and -C=C-) were observed on the supports and catalysts surface using in situ DRIFT analysis, which can be correlated to the activity and high selectivity reached. The role of the supports and electronic properties over Ag improve the H2 dissociative chemisorption during the hydrogenation reactions; promoting the selectivity and the high catalytic performance. Ag/Al and Ag/Al-Mg were the most active catalysts. This was due to the synergism between the active Ag/Ag+ species and the supports (electronic effects). The results show that Ag/Al and Ag/Al-Mg catalysts have favorable properties and are promising for the alkyne hydrogenation and olefin purification reactions.

Investigation and optimization of olefin purification in methanol-to-olefin process based on machine learning approach coupled with genetic algorithm

Investigation and optimization of olefin purification in methanol-to-olefin process based on machine learning approach coupled with genetic algorithm

Ultramicroporous material based parallel and extended paraffin nano-trap for benchmark olefin purification

Selective paraffin capture from olefin/paraffin mixtures could afford high-purity olefins directly, but suffers from the issues of low separation selectivity and olefin productivity. Herein, we report an ultramicroporous material (PCP-IPA) with parallel-aligned linearly extending isophthalic acid units along the one-dimensional channel, realizing the efficient production of ultra-high purity C2H4 and C3H6 (99.99%). The periodically expanded and parallel-aligned aromatic-based units served as a paraffin nano-trap to contact with the exposed hydrogen atoms of both C2H6 and C3H8, as demonstrated by the simulation studies. PCP-IPA exhibits record separation selectivity of 2.48 and separation potential of 1.20 mol/L for C3H8/C3H6 (50/50) mixture, meanwhile the excellent C2H6/C2H4 mixture separation performance. Ultra-high purity C3H6 (99.99%) and C2H4 (99.99%) can be directly obtained through fixed-bed column from C3H8/C3H6 and C2H6/C2H4 mixtures, respectively. The record C3H6 productivity is up to 15.23 L/kg from the equimolar of C3H8/C3H6, which is 3.85 times of the previous benchmark material, demonstrating its great potential for those important industrial separations.

Hydrophobic paraffin-selective pillared-layer MOFs for olefin purification

This work reports novel hydrophobic paraffin-selective pillared-layer MOFs realizing efficient adsorption separation of paraffins from olefins.

Computational investigation of cobalt and copper bis (oxothiolene) complexes as an alternative for olefin purification

Considering that olefins present a large volume feedstock, it is reasonable to expect that their purification is industrially critical. After the discovery of the nickel bis (dithiolene) complex Ni(S2C2(CF3)2)2 that exhibits electro-catalytic activity with olefins but tends to decompose by a competitive reaction route, related complexes have been explored experimentally and theoretically. In this paper, a computational examination is performed on differently charged cobalt and copper bis (oxothiolene) complexes [M (OSC2(CN)2)2] to test their potential applicability as the catalysts for olefin purification, using the simplest olefin, ethylene. Possible reaction pathways for ethylene addition on these complexes were explored, to determine whether some of these candidates can avoid the reaction route that leads to decomposition, which is distinctive from the nickel complex, and to form stable adducts that can subsequently release ethylene by reduction. Our calculations suggest that the neutral cobalt complex might be an alternative catalyst, because all its forms can bind ethylene to produce stable interligand adducts with moderate to low activation barriers, rather than to form intraligand adducts that lead to decomposition. The calculations also predict that these interligand adducts are capable of releasing ethylene upon reduction. In addition, it can produce the desired interligand adducts following two different reaction pathways, assigned as the direct and the indirect, with no need for anion species as co-catalysts, which is crucial for the nickel complex. Thus, the olefin purification process could be much simpler by using this catalyst.

Olefin Purification by Ag–exchanged X–type Zeolite Membrane

Olefin Purification by Ag–exchanged X–type Zeolite Membrane

Sulfur-Centered Reactivity of Oxidized Iron-Thiolate Complex toward Unsaturated Hydrocarbon Addition

The sulfur-based reactivity of transition-metal thiolate complexes toward alkenes has received extensive attention as a significant proposal for a potential olefin purification scheme. The one-electron oxidation of half-sandwich iron thioether-dithiolate complex [Cp*Fe(η3-tpdt)] (1, Cp* = η5-C5Me5; tpdt = S(CH2CH2S–)2) resulted in the formation of iron-stabilized thiyl radicals, which can interact with unsaturated hydrocarbons such as alkenes or alkynes to give the corresponding trithioether-iron adducts. Interestingly, during this transformation process, the formal oxidation state of the iron center changed from +IV to +II, which suggests a two-electron transfer from unsaturated hydrocarbons to the iron center. Furthermore, the electrochemical measurements reveal this C–S bond formation is an irreversible process, during which ethylene cannot release under electrochemical reductive conditions. These adducts were unambiguously identified by various spectroscopic and X-ray crystallographic characterizations.

Benchmarked Intrinsic Olefin Metathesis Activity: Mo vs. W

Combining Surface Organometallic Chemistry with rigorous olefin purification protocol allows evaluating and comparing the intrinsic activities of Mo and W olefin metathesis catalysts towards different types of olefin substrates. While well‐defined silica‐supported Mo and W imido‐alkylidenes show very similar activities in metathesis of internal olefins, Mo catalysts systematically outperform their W analogs in metathesis of terminal olefins, consistent with the formation of stable unsubstituted W metallacyclobutanes in the presence of ethylene. However, Mo catalysts are more prone to induce olefin isomerization, in particular when ethylene is present, probably because of their propensity to undergo more easily reduction processes.

Nickel Bis(diselenolene) as a Catalyst for Olefin Purification.

Nickel bis(dithiolene) reversibly binds olefins via a known interligand binding mechanism, but the complex has limited practical use, due to a competitive intraligand addition which results in decomposition. The present work examines an alternative nickel-based complex that eliminates the decomposition route. Specifically, we have examined the olefin binding processes of nickel bis(diselenolene) complexes using modern density functional theory. Both the inter- and intraligand adducts of the nickel bis(diselenolenes) are thermodynamically more stable than their dithiolene analogues. We have predicted that nickel bis(diselenolene) complexes do not decompose after the intraligand addition, and that the overall activation energies for the kinetically accessible products are quite small. In short, our computational work predicts that nickel bis(diselenolene) complexes are better electrocatalysts for olefin purification than the previous candidates, superior to the previously studied nickel bis(dithiolene) complexes.

Optimal Production of Light Olefins from Natural Gas via the Methanol Intermediate

This paper presents a comprehensive process synthesis superstructure toward the production of C2 to C4 olefins from natural gas via the methanol intermediate. The superstructure of alternatives includes multiple natural gas conversion pathways, multiple methanol conversion technologies, and an extensive olefin purification section. Simultaneous heat, power, and water integration is incorporated for the optimal utility usage within the refinery. A branch-and-bound global optimization framework approach is utilized to guarantee the global optimality. The profit of the proposed refinery is maximized across different scales and price levels. The optimal topology consistently includes the methanol-to-olefins, MTO, technology due to its high selectivity into high value olefins. The proposed refinery can be significantly profitable even under undesired price scenarios (June 2015 prices). The proposed plants yield positive net present values for scales above 500 MT/day, regardless of the price level investigated....

Promoted ceria catalysts for alkyne semi-hydrogenation

CeO2 is a highly selective catalyst for the partial hydrogenation of alkynes. However, due to its limited H2 splitting ability, a high operating temperature is required for the reaction, hampering the practical exploitation of this abundant oxide. In this work, we demonstrate that gallium promotes the activity of CeO2 for the semi-hydrogenation of acetylene and methylacetylene, enabling a reduction of the operating temperature to 373K, while maintaining an outstanding ethylene and propylene selectivity (80–97%), even in the presence of excess alkene in the feed. Oligomers comprised the main secondary product, while the selectivity to the corresponding alkane did not exceed 2%. The characterization of mixed Ce-Ga oxides reveals that the progressive incorporation of gallium into the ceria structure, forming a solid solution, boosts the oxygen storage capacity and the reducibility of the material. This is ascribed to the facilitated H2 activation on the Ga-promoted samples, as confirmed by in situ infrared spectroscopy and density functional theory simulations. The interplay between the advantage brought by the decreased barrier for H2 cleavage and the disadvantage due to the increased number of oxygen vacancies governs the reactivity of the CeGaOx catalysts in alkyne hydrogenation. The composition in the optimal catalyst, containing a molar Ce:Ga ratio of 95:5, was extrapolated to other trivalent cations. Indium incorporated in the ceria lattice favored the low-temperature H2 activation and led to an activity enhancement that surpassed that of gallium. However, aluminum did not form a solid solution with ceria and caused no effect. This work comprises the first application of promoted cerias in hydrogenation catalysis and may prompt further developments in olefin purification.

Computational exploration of alternative catalysts for olefin purification: cobalt and copper analogues inspired by nickel bis(dithiolene) electrocatalysis.

Olefin purification is an important process in petrochemistry. The behavior of the nickel bis(dithiolene) complex Ni(S2C2(CF3)2)2 (1(_Ni)) as an electrocatalyst for this process was thoroughly explored experimentally and computationally. Here, computational investigations with the ωB97X-D functional were conducted to explore alternative candidates [M(S2C2(CF3)2)2](n) (M = Co with n = 0, -1, -2, -3 and Cu with n = +1, 0, -1, -2) for olefin purification by using ethylene as a model. The reaction mechanism for these alternative catalysts was calculated to determine if any of these alternatives could block the decomposition route that exists for the Ni catalyst, bind ethylene efficiently to form the adducts, and release ethylene upon reduction. Calculations predict that the neutral cobalt complex 1(_Co) binds and releases olefin upon reduction with low activation barriers. Furthermore, 1(_Co), unlike 1(_Ni), catalyzes the desired reaction without the need of the anion as a cocatalyst. The Co atom directly coordinates with ethylene more favorably than Ni, facilitating the indirect pathway that is found to lead to the formation of the desired interligand adduct. The reduction and oxidation processes involved in the reaction are computed to occur under reasonable experiment conditions. Among the copper complexes, the calculations predict that the anionic copper complex 1(_Cu)(-) also may be an alternative catalyst, whose performance is somewhat worse than 1(_Ni). The reaction of 1(_Cu)(-) with ethylene is predicted to be thermodynamically neutral. New catalysts that need no electrochemical regenerations may be possible by designing appropriate dithiolene ligands for 1(_Cu)(-).

Composite phenolic resin-based carbon molecular sieve membranes for gas separation

Composite carbon molecular sieve membranes (c-CMSM) were prepared from phenolic resin loaded with boehmite by a single dipping–drying–pyrolysis step. The composite membrane was analyzed by scanning electron microscopy, high resolution transmission electron microscopy, X-ray diffraction, thermogravimetric analysis, mercury porosimetry, CO 2 adsorption and permeation experiments. It was produced a 2 μm thick composite uniform layer on top of a α-Al 2O 3 support. The composite top layer exhibited nanowires of Al 2O 3 1–2 nm thick and 10–30 nm long well dispersed in a microporous carbon matrix. The micropores network accounted for 63% of the total pore volume (DR isotherm). The c-CMSM exhibited ideal O 2/N 2 and C 3H 6/C 3H 8 permselectivities of 5 and 15, respectively. The performance of the c-CMSM for pair C 3H 6/C 3H 8 was above the upper bound curve for polymeric membranes, making it a promising vehicle for olefin purification.

Design methodology for a membrane/distillation column hybrid process

Hybrid processes consisting of a distillation column and a membrane separation module have gained some importance in the recent years due to their attractive capital and operating costs and potential in saving energy. For several applications hybrid processes proved to be superior to single separation processes. The aim of an optimal hybrid design should be to take advantage of the specific benefits of both separation methods. This paper introduces some guidelines and general rules which can be applied to distillation/membrane hybrid processes. The results of numerical calculations dealing with an olefin purification hybrid process using a distillation column and a facilitated transport vapor permeation membrane in different configurations are introduced and discussed. A McCabe-Thiele based approach is used to analyze different process configurations and find some short-cut methods to determine the optimal operating conditions for each configuration. Both new column design and augmentation of an existing distillation column by a membrane module are subjects of this paper.

Facilitated Transport Membrane Hybrid Systems for Olefin Purification

Abstract A new membrane system has been developed by BP for refinery and chemical plant olefin purification and recovery. This facilitated transport system, coupled with distillation, offers lower capital and operating costs than conventional distillation alone. Initial results on lab scale hollow fiber devices indicate membrane flux ranging from 8.75×10−6 to 8×10−5 m3/m2/sec (2.5 to 23 scfd/ft2) and selectivities from 150 to 300. Pilot plant experiments on propylene/propane and ethylene purge gas recovery over three to six months duration show membrane stability and product purity of 98.5% or greater using refinery grade propylene feed. Hybrid system optimization data for membranes and distillation indicate that using a side draw from the distillation tower provides advantages in terms of membrane area, purity of feed to the membrane, and low per-pass recovery coupled with high overall propylene recovery. Membrane performance data under various conditions will also be presented. In addition to performance data, economic evaluation and energy savings will be discussed.