Production Of Olefins Research Articles

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.

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

AbstractPlastic 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.

On‐Purpose Production of Light Olefins Through Oxidative Dehydrogenation: An Overview of Recent Developments

AbstractProducts made from light olefins play an important role in our daily lives. Traditional light olefins production based on steam cracking and fluid catalytic cracking suffer from high energy consumption and CO2 emissions. Thereby, the continually increasing demand for light olefins needs to be met through more environmentally sustainable procedures. On‐purpose production routes are preferred choice among petrochemicals manufacturers, being energy efficient and having lower carbon footprint. Among them, oxidative dehydrogenation (ODH) of light paraffins is a thermodynamically favourable exothermic process as compared to non‐oxidative routes. They can be operated at lower temperatures and have propensity of low coke deposition on catalyst, thereby resisting rapid catalyst deactivation. Herein, we have analysed various catalytic systems utilised in the oxidative dehydrogenation process. We have reviewed role of support, chemical composition of catalyst, presence of dopant, oxidation state of active metal, controlled surface modification by oxidative and reductive pretreatments, and reaction factors for each system. The performance of various catalytic systems for ODH of ethane, propane and butane in the presence of O2, CO2, N2O and special oxidants have been reviewed. A short critical overview on emerging on‐purpose routes for the production of renewable 1,3 butadiene has also been discussed.

Selective catalytic conversion of model olefin and diolefin compounds of waste plastic pyrolysis oil: Insights for light olefin production and coke minimization

The primary challenges in ex-situ catalytic pyrolysis of plastic waste to produce light olefins lie in the selective conversion of larger olefins and diolefins downstream of the pyrolyzer. Hence, the catalytic cracking mechanism of plastic pyrolysis oil was explored using an α-olefin (1-decene) and a diolefin (1,9-decadiene) model compounds over an HZSM-5 zeolite-based catalyst in a fixed-bed reactor. Key objectives were to elucidate the reaction pathways for light olefin production, aromatization, and coke formation in catalytic cracking of larger olefins and diolefins. The investigation explored the impact of HZSM-5 steam treatment severity, contact time (∼58–226 ms), and reaction temperature (250–450 °C) on product yields. The severity of steam treatment was found to increase the 1-decene isomerization rate while decreasing the cracking rate and conversion of 1-decene to C3-4 light olefins. In the catalytic cracking of 1-decene, major product types included olefins (linear and nonlinear) and a few naphthenes, while in the case of 1,9-decadiene catalytic cracking, non-linear olefins were absent, with abundant naphthenes followed by lighter diolefins and C3-5 linear olefins. Temperature and contact time variations revealed that the catalytic cracking of 1-decene initiated with double bond rearrangement isomerization, progressing to skeletal isomerization, and intensified cracking reactions producing light C3-4 olefins. Conversely, in the catalytic cracking of 1,9-decadiene, cyclization was the primary reaction pathway, followed by β-scission, resulting in lighter conjugated dienes and light linear olefins. Thermal gravimetric analysis (TGA) of spent catalysts confirmed a higher coke amount generated during 1,9-decadiene cracking compared to 1-decene cracking, indicating that diene compounds serve as precursors for significant coke formation in plastic pyrolysis oil. These insights provide valuable understanding for catalytic upgrading of pyrolysis oil from polyolefin pyrolysis.

Non-Ionic Peterson-Type Olefination Reactivity and its Use in a Silicon-Promoted Carbonyl-Carbonyl Cross Coupling Reaction.

The [2+2] cycloaddition reaction between the Si=C double bond of adamantylsilene and the carbonyl group of aliphatic, aromatic or acetylenic ketones and aldehydes is demonstrated. The product of this reaction that is central to a non-ionic version of the Peterson olefination is an unusual four-membered 1,2-silaoxetane heterocycle that was characterized spectroscopically and crystallographically. In the presence of SiO2, the silaoxetane undergoes retro-cycloaddition with the formation of alkene products. As the [2+2] cycloaddition proceeds without the necessity of any base, enolizable ketones can be converted into olefins. In addition, it is shown that the adamantylsilene can be produced in situ by a sila-Peterson reaction, providing valuable input for the development of a new one-pot silicon-based reductive carbonyl-carbonyl cross coupling methodology.

Non‐Ionic Peterson‐Type Olefination Reactivity and its Use in a Silicon‐Promoted Carbonyl‐Carbonyl Cross Coupling Reaction

AbstractThe [2+2] cycloaddition reaction between the Si=C double bond of adamantylsilene and the carbonyl group of aliphatic, aromatic or acetylenic ketones and aldehydes is demonstrated. The product of this reaction that is central to a non‐ionic version of the Peterson olefination is an unusual four‐membered 1,2‐silaoxetane heterocycle that was characterized spectroscopically and crystallographically. In the presence of SiO2, the silaoxetane undergoes retro‐cycloaddition with the formation of alkene products. As the [2+2] cycloaddition proceeds without the necessity of any base, enolizable ketones can be converted into olefins. In addition, it is shown that the adamantylsilene can be produced in situ by a sila‐Peterson reaction, providing valuable input for the development of a new one‐pot silicon‐based reductive carbonyl‐carbonyl cross coupling methodology.

N2O Assisted Ethane Transformation into Ethylene Using NiO−CeO2−ZrO2 Catalysts

AbstractNiO−CeO2 and NiO−CeO2−ZrO2 catalysts have been synthesized, electrochemically characterized (Mott‐Schottky (MS) measurements and Electrochemical Impedance Spectroscopy), physicochemically characterized (by N2 adsorption, XRD, Transmission Electron Microscopy and XPS) and tested in the N2O assisted ethane oxydehydrogenation. The use of low Zr‐loadings (Zr/Ce=0.1 at. ratio) has led to the optimal results in the ethylene production, improving those obtained by the Zr‐free NiO−CeO2 catalyst. However, high Zr‐loadings have meant a decrease in the olefin production. The catalytic results obtained have been explained considering the amount of oxygen vacancies, the crystalline phases formed and, especially, the nature of the surface Ni species. Importantly, the use of N2O as an oxidizing agent leads to a remarkable improvement in the selectivity to the olefin compared to that obtained employing molecular O2. Then, for a given ethane conversion the selectivity to ethylene is ca. 15 points higher using N2O than using O2. Another additional positive aspect of this NiO−CeO2−ZrO2 catalyst is its high catalytic stability.

Steam cracking in a semi-industrial dual fluidized bed reactor: Tackling the challenges in thermochemical recycling of plastic waste

Steam cracking is an integral process in the plastic manufacturing industry. Conventional steam crackers are tubular reactors and use fossil-based feedstocks like naphtha and LPG. This work presents steam cracking in a dual fluidized bed (DFB) reactor as an alternative for the direct steam cracking of plastic waste. Experiments were performed on a semi-industrial DFB system using naphtha, clean polyolefins, real-life plastic wastes, and a polyolefin-derived pyrolysis oil. The results show that steam cracking in a DFB is fundamentally equivalent to steam cracking in tubular reactors. Selective production of light olefins and monoaromatics was achieved within a temperature range of 700–825 °C. Naphtha yielded up to 56 % light olefins and 7 % BTXS, with ethylene and BTXS production positively correlating with cracking severity, while C3 and C4 olefins show a negative correlation. These results confirm that the established steam cracking mechanisms also apply to large-scale DFB steam crackers. The yield of light olefins is consistently obtained at approximately 52 % relative to the polyolefin content of the feedstock, regardless of the non-polyolefin content. This highlights the DFB steam cracker’s ability to produce light olefins directly from plastic waste without presorting. However, steam cracking in DFB results in significantly higher CO and CO2 yields than conventional steam cracking, especially with feedstocks containing non-polyolefins like PET and cellulose. Additionally, steam cracking of an olefin-rich pyrolysis oil yields up to 50 % light olefins with minimal coke formation, highlighting the potential in processing plastic waste pyrolysis oils without pretreatment steps such as distillation and hydrotreatment.

Reshaping the substrate-binding pocket of acyl-ACP reductase to enhance the production of sustainable aviation fuel in Escherichia coli.

To reduce carbon emissions and address environmental concerns, the aviation industry is exploring the use of sustainable aviation fuel (SAF) as an alternative to traditional fossil fuels. In this context, bio-alkane is considered a potentially high-value solution. The present study focuses on the enzymes acyl-acyl carrier protein [ACP] reductase (AAR) and aldehyde-deformylating oxygenase (ADO), which are crucial enzymes for alka(e)ne biosynthesis. By using protein engineering techniques, including semi-rational design and site-directed mutagenesis, we aimed to enhance the substrate specificity of AAR and improve alkane production efficiency. The co-expression of a modified AAR (Y26G/Q40M mutant) with wild-type ADO in Escherichia coli significantly increased alka(e)ne production from 28.92 mg/L to 167.30 mg/L, thus notably demonstrating a 36-fold increase in alkane yield. This research highlights the potential of protein engineering in optimizing SAF production, thereby contributing to the development of more sustainable and efficient SAF production methods and promoting greener air travel.

Computational insight into the selectivity of [formula omitted]-valerolactone hydrodeoxygenation over Rh(111) and Ru(0001)

The observed difference in the selectivity towards alkane, ketone, and alcohol hydrodeoxygenation products over Ru and Rh catalysts is explored using a combination of density functional theory and microkinetics. Using γ-valerolactone as a model compound, we investigate the reaction mechanism in order to identify selectivity determining species. The effect of the coadsorbed water molecule as well as the higher adsorbate surface coverage on reaction barriers and energies is explored as well. The performed calculations suggest that the desired alkane product is formed from a ketone intermediate on Ru, and through both ketone and alcohol on Rh, although the selectivity towards alkane on Rh is much lower than on Ru.

New Insights for High-Throughput CO2 Hydrogenation to High-Quality Fuel.

In the case of CO2 thermal-catalytic hydrogenation, highly selective olefin generation and subsequent olefin secondary reactions to fuel hydrocarbons in an ultra-short residence time is a huge challenge, especially under industrially feasible conditions. Here, we report a pioneering synthetic process that achieves selective production of high-volume commercial gasoline with the assistance of fast response mechanism. In situ experiments and DFT calculations demonstrate that the designed NaFeGaZr presents exceptional carbiding prowess, and swiftly forms carbides even at extremely brief gas residence times, facilitating olefin production. The created successive hollow zeolite HZSM-5 further reinforces aromatization of olefin diffused from NaFeGaZr via optimized mass transfer in the hollow channel of zeolite. Benefiting from its rapid response mechanism within the multifunctional catalytic system, this catalyst effectively prevents the excessive hydrogenation of intermediates and controls the swift conversion of intermediates into aromatics, even in high-throughput settings. This enables a rapid one-step synthesis of high-quality gasoline-range hydrocarbons without any post-treatment, with high commercial product compatibility and space-time yield up to 0.9 kggasoline ⋅ kgcat -1 ⋅ h-1. These findings from the current work can provide a shed for the preparation of efficient catalysts and in-depth understanding of C1 catalysis in industrial level.

CO2 hydrogenation to light olefins over highly active and selective Ga-Zr/SAPO-34 bifunctional catalyst

The production of light olefins from the hydrogenation of CO2 is an efficient way to utilize CO2, where the surface oxygen vacancy in metal oxide plays an important role in CO2 adsorption and activation. Here, the Ga-Zr metal oxides were prepared by hydrolysis of urea at different temperatures and combined with SAPO-34 to prepare the bifunctional catalyst for CO2 hydrogenation to light olefins. The surface oxygen vacancy content of Ga-Zr oxide increases with increasing urea hydrolysis temperature, and a high CO2 conversion of 26.4% and C2=–C4= hydrocarbon selectivity of 87.2% were obtained by a well-matched amount of desorbed CO2 and H2. Using the CO2 and H2/HCOOH/CH3OH as probe molecules, the in-situ DRIFT spectra reveal that the CO2 could be activated on surface oxygen vacancy and converted to CO3* and HCO3* species, which were further hydrogenated to HCOO* and CH3O* species. While the by-product CO mainly originates from the decomposition of HCOO* and the presence of SAPO-34 converts CH3O* to C2=–C4=. The current study illustrates that boosting the surface oxygen vacancy in defected surfaces of metal oxide and providing a matching H2 dissociation ability is the key to improve the performance of CO2 hydrogenation to light olefins.

Deactivation of Cu/ZSM-5 Catalysts during the Conversion of 2,3-Butanediol to Butenes

This work determines the deactivation mechanisms of Cu/ZSM-5 catalysts used for the conversion of 2,3-butanediol to butene as part of an alcohol-to-jet route. The deactivation of the catalyst, reflected by a drop in the rate of the limiting hydrogenation step by over 90% in 24 h at a weight hourly space velocity of 5.92 h−1, proceeds via both the agglomeration of copper particles and the obstruction of copper surfaces due to carbonaceous deposits, although the former has less impact on the decrease in the hydrogenation rate. To reduce the detrimental effect of carbonaceous deposits on catalytic activity, ZMS-5 is modified through desilication of the HZSM-5 support with NaOH and CsOH solutions to generate a hierarchical structure with mesopores. The catalyst with the CsOH-treated support generates the highest overall yield of desired olefin products and experiences the slowest deactivation. This is a result of the lower Brønsted acidity and larger mesopores found in the CsOH-treated catalyst, leading to the slower formation of carbonaceous deposits and the faster diffusion of their precursors out of the pores.

Process Development and Techno-Economic Analysis for Combined and Separated CO2 Capture-Electrochemical Utilization

Combining CO2 capture and utilization into a single unit operation offers a feasible solution for converting a sustainable feedstock into marketable commodity chemicals, while reducing energy requirements from separated processes. In this research, we developed a process model and performed a techno-economic analysis (TEA) for point-source CO2 capture and electrochemical-based utilization in light olefins production under both separated and integrated scenarios. CO2 containing flue gas from a 500 MW power plant was utilized as a feed while CO2 utilization involved electrochemical reduction reactions to produce light olefins directly from CO2. A meticulous analysis was conducted, probing into the multifaceted impacts of various operating parameters, material properties, and downstream treatment units. Factors such as pressure, temperature, H2O/CO2 molar ratio, catalyst and adsorbent activities, deactivation rate, and heat integration were optimized to achieve 95 % CO2 recovery and > 90 % conversion, and > 85 % ethylene yield. Through a comprehensive TEA, our findings unveiled that the combined process utilizing bifunctional adsorbent/catalyst materials (BFMs) incurs costs of approximately $284/ton CO2, whereas the separated process reported expenses of ∼$516/ton CO2. This study, pivotal in its contributions, evaluated economic feasibility of combined capture-conversion method based on BFMs for CO2 removal and subsequent utilization via a promising advanced process model for sustainable feedstocks conversion to commodity chemicals.