Production Of Olefins Research Articles

Chemical Looping: A Sustainable Approach for Upgrading Light Hydrocarbons to Value-Added Olefins.

In recent times, chemical looping offered a sustainable alternative for upgrading light hydrocarbons into olefins. Olefins are valuable platform chemicals that are utilized for diverse applications. To close the wide shortfall in their global supply, intensified efforts are ongoing to develop on-purpose production technologies. Herein, we provide discussions on the emerging olefin production routes and chemical looping as a frontier concept in catalytic production of chemicals, especially light olefins. Moreover, we discuss the various rational strategies for designing and tuning of oxygen carriers with high catalytic activity and tailored selectivity to desired products. These strategies include creation of oxygen vacancies, controlled doping, synergistic metal-support interactions, regulating oxygen mobility, modulation of crystal structure, functionalization and controlled treatment. The insights presented aim to inspire the development of robust, stable, and efficient oxygen carriers, ensuring catalytic activity, selectivity, and prolonged operational stability.

Efficient Photocatalytic Propane Direct Dehydrogenation to Propylene Over PtO2 Clusters.

The direct dehydrogenation of alkanes to olefins under mild conditions is challenging due to the inert nature of alkyl C─H bonds. Herein, an efficient photocatalytic system is developed for propane direct dehydrogenation (PDH) to propylene, consisting of ≈1.30nm sized PtO2 clusters immobilized on a layered double hydroxide -derived ZnO/Al2O3 support (LD-Ptn). Under UV excitation (365nm), photogenerated holes in ZnO migrate to Pt sites at PtO2/ZnO interfaces, thereby activating and dissociating C─H bonds in propane. A propylene production rate of almost 1mmol g-1h-1 and a nearly 100% selectivity are achieved for the compositionally optimized LD-Ptn photocatalyst. Control experiments and density functional theory calculations further verify that the excellent photocatalytic PDH performance of LD-Ptn stems from synergism between ZnO semiconductor and the loaded Pt species. This work identifies a promising new route for direct production of olefins from alkanes.

Boosting Electrocatalytic Hydrogenation of Phenylacetylene via Accelerating Water Electrolysis on a Cr-Cu2O Surface.

Electrochemical alkyne reduction with H2O as a hydrogen source represents a sustainable route for value-added olefin production. However, the reaction efficiency is hampered by the high voltage and low activity of Cu electrodes due to their weak adsorbed hydrogen (*H) generation property. In this article, we present the enhanced electrocatalysis of phenylacetylene to styrene over a highly dispersive Cr-doped Cu2O nanowire (Cr-Cu2O) cathode. The Cr-Cu2O demonstrates improved catalytic activity compared to pure Cu2O, achieving a high conversion of about 94.7% and a selectivity of 87.9% with a Faraday efficiency of 64.5% at a low potential of -1.15 V vs Hg/HgO. The combination of electrochemical characterization techniques and theoretical calculations demonstrated the key role of introduced Cr atoms in lowering the activation energy barrier of surface water electrolysis to *H and facilitating the adsorption of phenylacetylene, which promotes the effective hydrogenation of phenylacetylene with *H via an electrocatalytic hydrogenation mechanism. In short, this work provides a feasible strategy to enrich interfacial *H, thus improving the semihydrogenation performance of phenylacetylene.

Selective production of olefins from methanol over a heteroatomic SAPO-34 zeolite.

The methanol-to-olefins (MTO) process has the potential to bridge future gaps in the supply of sustainable lower olefins. Promoting the selectivity of propylene and ethylene and revealing the catalytic role of active sites are challenging goals in MTO reactions. Here, we report a novel heteroatomic silicoaluminophosphate (SAPO) zeolite, SAPO-34-Ta, which incorporates active tantalum(V) sites within the framework to afford an optimal distribution of acidity. SAPO-34-Ta exhibits a remarkable total selectivity of 85.8% for propylene and ethylene with a high selectivity of 54.9% for propylene on full conversion of methanol at 400°C. In situ and operando synchrotron powder X-ray diffraction, diffuse reflectance infrared Fourier transform spectroscopy and inelastic neutron scattering, coupled with theoretical calculations, reveal trimethyloxonium as the key reaction intermediate, promoting the formation of first carbon-carbon bonds in olefins. The tacit cooperation between tantalum(V) and Brønsted acid sites within SAPO-34 provides an efficient platform for selective production of lower olefins from methanol.

Hierarchical ZSM-5 nanosheets for production of light olefins and aromatics by catalytic cracking of oleic acid

The bolaform surfactant C6H13-N+(CH3)2-C6H12-N+(CH3)2-C6H12-O-C6H4-C6H4-O-C6H12-N+(CH3)2-C6H12-N+(CH3)2-C6H13 (BCPH-6-6-6) was synthesized and used to guide the synthesis of hierarchical ZSM-5 nanosheets (HZN) for use as zeolite catalysts.

Reusability Studies with Lewis and Brønsted Acid Catalysts for Dehydration of the Primary Alcohol 1-Hexanol under Energy-Saving Conditions

In general there is an urgent current need to switch from fossil-based materials to renewable sources and this is also the case for production of alkenes with a chain length...

Design and analysis of a CO2-to-olefins process, using renewable energy

This paper presents a light olefins production plant that hydrogenates carbon dioxide to C2-C4 using green hydrogen and electricity produced from solar and wind energy resources. In this regard, combining Fischer-Tropsch and methanol-mediated pathways on a large scale is analyzed as a new method to increase light olefins production. Additionally, an optimized hybrid renewable energy system comprised of solar panels, wind turbines, electrolyzers, batteries, converters, and so on is designed to supply the necessary utilities for the plant. The simulation results indicate that 590.9, 744.8, and 522.9 kg/h of ethylene, propylene, and butylene can be produced by processing 10% of carbon dioxide emitted from a cement factory, resulting in the negative emission of 2.14 kg CO2/kg C2-C4. This plant needs 1420 kg/h of hydrogen to convert carbon dioxide into light olefins and 32 MW of electricity to meet hot, cold, and electric utility requirements, all powered by renewable energy. The optimization results demonstrate that the initial capital and net present costs of the renewable energy system are $1.15B and $1.38B, respectively, leading to the levelized costs of hydrogen and electricity of 3.56 $/kg and 0.12 $/kWh, respectively.

Shape-selective catalysis in cavity-type molecular sieves: cavity-controlled catalytic principle.

The methanol-to-olefins (MTO) process, driven by zeolites or molecular sieves, a cornerstone of C1 chemistry, has established a substantial pathway for generating olefin products from non-petroleum sources. Molecular sieves exhibit significant benefits in catalysis with shape selectivity due to the unique confinement environment and acidic properties, featuring their molecular sieving and confinement effects. Significantly, eight-membered ring (8-MR) and cavity-type molecular sieve catalysts, characterized by large cage volumes and restricted window openings, exhibit distinctive host-guest interactions between the cavity structure and the reactants, intermediates, and products within the confined space, thereby revealing the cavity-controlled methanol conversion principle in molecular adsorption and diffusion, intermediate formation, reaction pathway, and catalyst deactivation processes. This review mainly summarizes molecular adsorption characteristics and diffusion behavior, as well as the mechanisms of the MTO reaction and catalyst deactivation within cavity-type molecular sieves. A comprehensive introduction is provided on the variations in preferential adsorption sites and diffusion behavior of guest molecules induced by different cavity structures within cavity-type molecular sieves. Furthermore, the critical intermediate generation governed by cavity structure and the nonuniform distribution of coke species within the catalyst were also discussed. The cavity-controlled catalytic principle of the MTO reaction driven by 8-MR and cavity-type molecular sieves provides valuable insights for the modification of molecular sieve catalysts and the optimization of the MTO process and also promotes broader application of these catalysts in other C1 chemical reactions.

C-H Bond Activation by Sulfated Zirconium Oxide is Mediated by a Sulfur-Centered Lewis Superacid.

Sulfated zirconium oxide (SZO) catalyzes the hydrogenolysis of isotactic polypropylene (iPP, Mw=13.3 kDa, Đ=2.4, <mmmm>=94 %) or high-density polyethylene (HDPE, Mn=2.5 kDa, Đ=3.6) to branched alkane products. We propose that this reactivity is driven by the pyrosulfate sites SZO, which open under mild conditions to transiently form adsorbed SO3 and sulfate groups. This adsorbed SO3 is a very strong Lewis acid that binds 15N-pyridine or triethylphosphineoxide (TEPO) (ΔEads>-39 kcal mol-1), reacts with Ph3CH to form Ph3C+, and mediates H/D exchange in dihydroanthracene-d4. DFT studies show that pyrosulfate sites open with a modest 26.1 kcal mol-1 barrier to form the adsorbed SO3 and sulfate in the presence of a tetramer of propylene. Hydride abstraction from the tertiary C-H in this model is exothermic and subsequent β-scission forms cleaved products. Analysis of the energetics provided here brackets the hydride ion affinity (HIA) of the adsorbed SO3 between 226.2 to 237.9 kcal mol-1, among largest values reported for a formally neutral Lewis acid. This study explains how SZO, a classic heterogeneous catalyst, can form carbocations by a redox neutral hydride abstraction reaction by very strong Lewis sites.

Green diesel alkanes production by hydrodeoxygenation of neem seed oil over nickel-zeolite based catalyst

Production of green diesel alkanes (DA) from vegetable oils is highly efficient in reducing dependence on finite fossil fuels. Catalytic hydrodeoxygenation (HDO) of non-edible extracted Neem seed oil (NSO) in a batch reactor over Ni/nano zeolite catalyst was investigated. The main issues of the effective HDO in terms of high yield and selectivity towards long-chain alkanes in mild operating conditions have been addressed. It was revealed that in the HDO reaction of NSO over 30% Ni/nano zeolite, the highest DAs (C10–C18) yields is 88.84% at 350 °C, process time of 4 h and hydrogen pressure of 8 bar. This performance can be attributed to the well-distributed Ni in the support surface as well as the acidity of the catalyst and proper textural properties. The results from current study demonstrated that the 30% Ni/nano zeolite catalyst is a potential HDO catalyst for the production of green diesel. In most experiments, the transformation of NSO into DAs was accomplished through decarboxylation (DCO2) and decarbonylation (DCO) routes. However, the progress of the process to the obtained products from the HDO pathway was surprisingly increased at temperatures above 300 °C.

Role of different alumina supports and reduction method on performance of Pt-Sn catalysts: Individual and mixed-paraffin dehydrogenation for olefin production

Role of different alumina supports and reduction method on performance of Pt-Sn catalysts: Individual and mixed-paraffin dehydrogenation for olefin production

Process Simulations and Technoeconomic Analysis of Ethylene Production By Electrochemical Reduction of Carbon Capture Solutions

Electrocatalytic reduction offers an alternate route for production of olefins from non-traditional feedstocks such as CO2, resulting in a lower carbon footprint if coupled with renewable sources of energy.Electrolyzer architectures employing bipolar membranes (BPMs) to convert aqueous alkaline carbonates (carbon capture solution) into hydrocarbons are a potential solution to overcome the limitations of high H2 production and crossover rates that limit CO2 conversion in conventional CO2 gas-fed electrochemical systems. Current literature lacks a full process analysis of such a system for C2+ hydrocarbons production, especially the inclusion of direct air capture of CO2 as part of the process and identification of the key tradeoffs involved in such systems. To address this important issue, here we present comprehensive process simulations, process design analysis, and technoeconomic evaluation of integrated electrolysis-based systems (beginning with CO2 capture and ending in electrolyzer product separation and stream recycling) for ethylene production from carbonates. Process simulations revealed the importance of upstream concentration of the captured carbonate feed stream by a membrane system operable at alkaline conditions, which makes the overall process economically feasible. Electrolyzer sizing, scale-up, and configuration are examined in more detail. Costing of the electrolyzer was approached with nonlinear scaling to better account for economies of scale relevant for electrochemical systems. Three different scenarios were considered for a 2 million metric tons (MMT)/yr ethylene plant. A set of key projected performance metrics has been determined for future profitable large-scale production of ethylene from alkaline carbonates. This BPM-based conversion process was evaluated with both direct air capture (DAC) and flue gas capture scenarios for carbonate production, demonstrating roughly equivalent economic feasibility (<8% difference between the 2 cases). Ongoing improvements in BPM-based processes can lead to ethylene minimum selling prices (MSPs) comparable to MSPs from naphtha-based processes, which are also projected to be lower than those of more conventional CO2 gas-fed electrochemical processes.

A functional group-based approach containing catalyst properties to modeling catalytic pyrolysis of multiple hydrocarbon mixtures

The intricate composition of naphtha poses a significant challenge in formulating a comprehensive modeling approach for the production of light olefins. In this study, the intricate composition of the feedstock was described based on the weight percentage of the functional groups. At the same time, the distribution variations of the pyrolysis products were characterized using their stoichiometric coefficients (SCs). Consequently, a functional group-based approach was proposed to model the catalytic pyrolysis of multiple hydrocarbon mixtures over ZSM-5 based catalysts by establishing a quantitative correlation between the composition of the functional groups and the SCs of the pyrolysis products. Furthermore, a comprehensive functional group-based approach was developed to integrate catalyst properties by relating their acidity to the SCs of pyrolysis products. This modeling approach allows for precise forecasting of product compositions across a range of feedstocks and catalyst systems, with a maximum error of 1.15 wt%. In addition, this modeling method can also be used to optimize feedstock blends and tailor acid properties to maximize light olefin production, highlighting its potential for use in various hydrocarbon mixtures.

Cr6+ Loaded Lewis Acidic Sn‐Beta Zeolites as Reusable Catalysts for Selective Production of Light Olefins via Polyolefin Cracking

AbstractCatalysts for the selective recovery of light olefins from polyolefins should be developed to save limited fossil resources. It is previously revealed that Brønsted acid‐free Sn‐Beta zeolites selectively produced light olefins from polyolefin cracking. Brønsted acid sites ionize olefins by protonation and the generated carbenium ions are converted into other hydrocarbons via various reactions, thereby the elimination of their effects led to the improvement of light olefin production ability. However, the deactivation of zeolites by coke deposition is a critical problem for industrialization. Inhibition of coking deactivation is previously achieved by doping Cr6+ species connected to silanol groups in zeolites. This work aimed to inhibit coke deposition and realize selective and continuous production of light olefins through repetitive polyolefin catalytic cracking. Sn‐Beta zeolites are prepared with various crystallinity by changing the feed fluoride ions content in their synthesis and found that their activity on low‐density polyethylene (LDPE) cracking strongly depended on the feed F/Si ratios, implying the active sites for polyolefin cracking are Lewis acidic open‐Sn sites. Moreover, Cr6+‐doped Sn‐Beta zeolites showed over 45% light olefin yields even in the third LDPE cracking test, although excess Cr adding led to reduce the catalytic activity of Sn‐Beta zeolites.

Intermolecular 1,2-Aminoboration of Alkynes and the Critical Role of Electron-Rich Alkynes.

The intramolecular 1,2-aminoboration of alkynes by aminoboranes is rare and invariably requires a catalyst to proceed, while the intermolecular aminoboration of alkynes is yet entirely unknown. Through an exploration of the significance of electronics in alkynes for activating the B-N σ-bond of aminoboranes, we demonstrate in this work the first intermolecular 1,2-aminoboration of alkynes. These reactions employ a series of (amino)dihaloboranes and aminoboronic esters, mild reaction conditions, and no catalysts, yielding syn-addition alkene products with the incorporation of two crucial functionalities: amino and boryl. While highly electron-rich examples can afford the aminoborated products (Z)-2-borylethenamines, other alkynes, including unactivated and less electron-rich examples, do not lead to the corresponding aminoborated products due to the fundamental impediment that the reactions are significantly endergonic.

Study on the effects of aging on the pyrolysis of plastic and the synergistic mechanisms of co-pyrolysis with lignite

Co-pyrolysis of waste plastic with low-rank coal explored how photoaging impacts the pyrolysis of plastics and delves into the synergistic mechanisms involved in co-pyrolysis. The results of elemental analysis, X-ray powder diffraction and Fourier transform infrared spectroscopy showed that photoaging primarily involves oxidizing and breaking the aliphatic chains in polyethylene (PE), as well as generating oxygen-containing functional groups like hydroxyl (-OH), carbonyl (-C=O), and ether (-C-O), thereby reducing the crystallinity of PE. The results of individual plastic pyrolysis showed that photoaging is beneficial to the generation of gas and tar. Pyrolysis tar of PE samples contains significant amounts of alcohols, and olefins and alkynes (O&As). The results of co-pyrolysis indicated that photoaging can enhance the yields of gas and oil from the co-pyrolysis between PE and Naomaohu (NMH) coal. Co-pyrolysis effectively reduced the relative content of O&As in the tar from the pyrolysis of PE samples alone by 8.0%–29.0 %. The synergistic mechanism of co-pyrolysis between aged PE and NMH involved supplying a significant quantity of hydrogen and hydroxyl radicals by NMH, which react with alkyl radicals generated from PE pyrolysis, leading to the production of additional alkanes and alcohols. These findings offered new insights for a deeper understanding of the co-pyrolysis behaviors between waste plastic and lignite.

Mechanistic insight into accelerating of light olefin products by surface OH* group on the Fe5C2 catalyst

The conversion of CO2 into high-value-added chemicals via the Fischer-Tropsch Synthesis (FTS) reaction has gathered a lot of attention. The surface oxygenation environment is a significant factor affecting performance of the catalyst. In this work, spin-polarized density-functional theory calculations have been used to investigate the OH* modulation mechanism on CO2 hydrogenation to generate C1 and C2 species. On the pure Fe5C2(510) surface, CH4 is formed through the hydrogenation of dissociated carbon by CO2 activation. At low OH* coverage, the C–C coupling reactions are dramatically promoted compared to methane formation. In addition, CO2 hydrogenation reactions are facilitated by the OH* species, indicating a high activatity and C2+ selectivity. At high OH* coverage, C2 products preferentially form through the CsH2-CdH2* intermediates, contributing to the high selectivity of light olefin products. The results demonstrate that maintaining the surface environment with OH* could be an indispensable measure to obtain the target product in the iron-based CO2 Fischer-Tropsch synthesis system.

Boosting light olefin production from pyrolysis of low-density polyethylene: A two-stage catalytic process

The increasing production of waste plastics poses significant environmental and health risks. Low-density polyethylene (LDPE), a major component of plastic waste, is a high-quality feedstock for pyrolysis due to its high carbon and hydrogen content. Traditional pyrolysis methods, such as thermal cracking and one-step catalytic pyrolysis, have limitations in yield and selectivity of valuable products like light olefins. This study introduces a two-stage catalytic pyrolysis (TSCP) process aimed at enhancing the production of light olefins from LDPE. In the first stage, LDPE undergoes pyrolysis with MCM-41 catalyst, yielding a substantial number of liquid products and a minor portion of light olefins. The second stage utilizes Mg-ZSM-5 catalyst to further crack the high-temperature volatile matter into light olefins. The optimal conditions identified were 450 °C in the first stage and 500 °C in the second stage, achieving a maximum light olefin yield of 45.80 wt% and a low reaction temperature, decreasing the energy consumption. Additionally, the MCM-41 catalyst demonstrates excellent regeneration performance, with only a slight decrease in liquid yield after nine cycles. The Mg-ZSM-5 catalyst maintains high stability, with light olefin yield remaining at 83.60 % of the initial yield after 48 h of operation.

Tuning CO2 Hydrogenation to Light Olefin Selectivity via Cu/Zn/Zr Supported on Modified SAPO‐34

AbstractTo alleviate CO2 emissions and reduce reliance on fossil fuels, a groundbreaking bifunctional catalyst system was introduced, which ingeniously merged CZZ with modified SAPO‐34 zeolite, to convert CO2 into light olefins. Different metals were impregnated into SAPO‐34 to form MeSAPO‐34 (Me = Zn, Zr, Mn) and the metal Zr content was altered. Furthermore, CZZ and MeSAPO‐34 was combined into CZZ/MeSAPO‐34 composite catalysts, which was used for CO2 hydrogenation. The MeSAPO‐34 and xZrSAPO‐34 catalysts were rigorously characterized by various techniques, revealing key physicochemical attributes. This innovative approach harnessed the synergistic effects between the metallic CZZ component and the modified zeolite to facilitate a series of reactions, effectively generating C2‐C4‐rich hydrocarbons. Benefiting from weak acid, higher oxygen vacancy concentration and interactions between components, the CZZ/ZrSAPO‐34 catalyst system has shown remarkable efficiency in enhancing the light olefin selectivity. The key aspects of this system are its ability to modulate surface acidity and oxygen vacancy concentration, thus creating favorable conditions for light olefin production via enhanced tandem reaction based on CO2 hydrogenation. This work enriches our insight into designing novel composite catalysts for promoting CO2 conversion and hence mitigating CO2 emissions.

Ultra-Narrow Alkane Product Distribution in Polyethylene Waste Hydrocracking by Zeolite Micro-Mesopore Diffusion Optimization.

Plastic pollution poses a pressing environmental challenge in modern society. Chemical catalytic conversion has emerged as a promising solution for upgrading waste plastics into valuable liquid alkanes and other high value products. However, the current methods yield mixed products with a wide carbon distribution. To address this challenge, we present a bifunctional catalytic system consisting of β zeolite mixed hierarchical Pt@Hie-TS-1, designed for the conversion of low-density polyethylene (LDPE) into liquid alkanes. This system achieves a 94.0 % yield of liquid alkane, with 84.8 % of C5-C7 light alkanes. Combined with in situ FTIR and molecular dynamics simulation, the shape-selective mechanisms is elucidated, which ensures that only olefins of the appropriate size can diffuse to the encapsulated Pt sites within the zeolite for hydrogenation, resulting in an ultra-narrow product distribution. Furthermore, by optimizing the micro-mesopores of Pt@Hie-TS-1, the scaling relationship between the pore structure and the conversion/selectivity is identified. The rapid diffusion of olefins within these micro-mesopores significantly enhances the catalytic efficiency. Our findings contribute to the design of efficient catalysts for plastic waste valorization.