Production Of Olefins Research Articles

Rhodium(I)-Catalyzed Defluorinative Coupling of Boronic Acids with Monofluoroalkenes.

We herein describe a highly selective Rh(I)-catalyzed defluorinative coupling of boronic acids with (E)-β-monofluoroacrylates. In contrast to previous methods, the trisubstituted (Z)-alkene products were obtained in excellent dr with an inversion of double bond geometry. Experimental and computational studies established that Rh(I)-facilitated β-F elimination is favored over competing β-H elimination and protodemetalation.

Greenhouse gas benefits from direct chemical recycling of mixed plastic waste

Dealing with heterogeneous plastic waste – i.e., high polymer heterogeneity, additives, and contaminants – and lowering greenhouse gas (GHG) emissions from plastic production requires integrated solutions. Here, we quantified current and future GHG footprints of direct chemical conversion of heterogeneous post-consumer plastic waste feedstock to olefins, a base material for plastics. The net GHG footprint of this recycling system is −0.04 kg CO2-eq./kg waste feedstock treated, including credits from avoided production of virgin olefins, electricity, heat, and credits for the partial biogenic content of the waste feedstock. Comparing chemical recycling of this feedstock to incineration with energy recovery presents GHG benefits of 0.82 kg CO2-eq./kg waste feedstock treated. These benefits were found to increase to 1.37 kg CO2-eq./kg waste feedstock treated for year 2030 when including (i) decarbonization of steam and electricity production and (ii) process optimizations to increase olefin yield through carbon capture and utilization and conversion of side-products.

Analysis of thermodynamic equilibrium yield and process simulation for catalytic pyrolysis of light hydrocarbons based on one set of independent reactions

The catalytic pyrolysis of light hydrocarbons has been regarded as a promising route for satisfying the growing demand for light olefins. This study established a thermodynamic equilibrium model based on one set of independent reactions in the catalytic pyrolysis process, for predicting the thermodynamic equilibrium yield and analyzing the effects of the operating conditions on the equilibrium yields. The trend of the equilibrium yields was consistent with the trend of the experimental yields. Thus, under the present operating conditions, determined by applying the thermodynamic equilibrium model, the production of light olefins was increased and the propylene/ethylene (P/E) ratio could be tailored to meet market demands. Then, an actual reaction degree model based on independent reactions was established and incorporated in Aspen Plus to simulate the catalytic pyrolysis process, and the reliability was validated experimentally. The thermodynamic equilibrium model and process simulation are easy to implement and can help to optimize the operating conditions and to predict the product yields for the catalytic pyrolysis of light hydrocarbons.

Cross-metathesis of biomass to olefins: Molecular catalysis bridging the gap between fossil and bio-energy

Terminal olefins are important building blocks for the industry of biofuels, oligomers, and lubricants production. The industrial processes for production of olefins involving oligomerization of ethylene or cracking of petrochemical waxes have several flaws including low yield and high cost in product separation. Cross - metathesis of bio - derived unsaturated fatty esters and olefins with ethylene (ethenolysis), allows the conversion of sustainable waste biomass to various renewable olefins with much safer, less toxic, sustainable, and zero-CO 2 emission processes. To our best knowledge, however, a comprehensive summary of key advances in this field (since 2017) is yet to be available, particularly on molecular features of homogeneous and heterogeneous catalysts. This paper presents a critical review on molecular structures of metal complex and oxide catalysts for ethenolysis of olefins and oleochemicals. The influence of cationic centers, coordination conditions, nature of ligands, operating conditions on catalyst performances will be systematically discussed along with relevant reaction mechanism. The key challenges for rational design of coordinated cationic hybrids have been summarized, which will provide insights to technological advancement of large - scale production of oleochemical - derived olefins.

Lewis base promoted photoredox catalyzed addition of allylic radicals to Michael acceptors

Upon activation via photoredox reaction conditions, allylic boronic esters can generate allylic radicals that react readily with Michael acceptors. The functionalized alkene products formed via this reaction can then be further transformed to other synthetically useful structures. As an example of this, we synthesized lipid-like structures that could be utilized for nucleic acid delivery. The robustness of these organoboronic reactions will allow for derivatization of these branched lipid structures where amino groups and aliphatic tails may be tuned to optimize these ionizable excipients.

Alkali metal halide-coated perovskite redox catalysts for anaerobic oxidative dehydrogenation of n-butane.

Oxidative dehydrogenation (ODH) of n-butane has the potential to efficiently produce butadiene without equilibrium limitation or coke formation. Despite extensive research efforts, single-pass butadiene yields are limited to <23% in conventional catalytic ODH with gaseous O2. This article reports molten LiBr as an effective promoter to modify a redox-active perovskite oxide, i.e., La0.8Sr0.2FeO3 (LSF), for chemical looping–oxidative dehydrogenation of n-butane (CL-ODHB). Under the working state, the redox catalyst is composed of a molten LiBr layer covering the solid LSF substrate. Characterizations and ab initio molecular dynamics (AIMD) simulations indicate that peroxide species formed on LSF react with molten LiBr to form active atomic Br, which act as reaction intermediates for C─H bond activation. Meanwhile, molten LiBr layer inhibits unselective CO2 formation, leading to 42.5% butadiene yield. The redox catalyst design strategy can be extended to CL-ODH of other light alkanes such as iso-butane conversion to iso-butylene, providing a generalized approach for olefin production.

Wheat straw/HDPE co-reaction synergy and enriched production of aromatics and light olefins via catalytic co-pyrolysis over Mn, Ni, and Zn metal modified HZSM-5

The co-reaction synergy of wheat straw (WS) and high-density polyethylene (HDPE) plastic waste with varying mass ratios were evaluated at 550 °C in a fixed bed pyrolyzer reactor. Ex-situ catalytic co-pyrolysis of WS and HDPE feed mix (3:1) at a high feed to catalyst ratio (10:1) was performed over Mn, Ni, and Zn (1, 5, and 10 wt%) metal-modified HZSM-5 at 550 °C to study the effect of metal promotors variations on the production of aromatics and light olefins. The prepared catalysts were characterized by employing XRD, N2 physisorption, NH3-TPD, H2-TPR, and UV-Vis analytical techniques. The results obtained in the present work indicated that 1%-Zn modified HZSM-5 produced a more relative proportion of aromatics (25.12%) in the co-pyrolysis oil organic phase, followed by 5% Ni and 5%-Zn-loaded HZSM-5 at 16.22% and 15.76% respectively. Furthermore, 5% Ni-HZSM-5 has shown higher deoxygenation ability (58.43%) in reducing the oxygenates formed, followed by 5% Mn (40.96%) and 1% Zn (35.37%) respectively. While, 5% Mn-HZSM-5 generated pyrolytic gases with higher volumetric compositions of (C2-C4) light olefins at 15.84%, followed by 1% Mn (13.97%) and 10% Ni (13.61%) respectively and these volumetric yields were strongly correlated with intermediate acidity of catalysts. The physical properties (e.g. HHV ~ 41–43 MJ/kg) of the resultant organic fraction of catalytic co-pyrolysis bio-oil are almost analogous to conventional fuels such as diesel and light fuel oil (LFO). Additionally, the resultant catalytic pyrolytic gases possessed excellent calorific value (LHV ~ 30–31 MJ/Nm3) and are comparable to natural gas. Overall, the present study has successfully demonstrated the promising nature of the catalytic co-pyrolysis process for the conversion of biomass and waste plastic into useful chemicals and fuels.

Production of jet-fuel-range olefins via catalytic conversion of pentene and hexene over mesoporous Al-SBA-15 catalyst

The oligomerization of biomass-derived light olefins offers a promising potential for the synthesis of sustainable jet-fuels, which mostly comprise C10-C18 hydrocarbons. However, the selectivity control of oligomerization reaction remains a challenge. In this contribution, oligomerization of pentene and hexene mixtures was studied over acidic mesoporous Al–SBA–15 catalyst in continuous operation, and the impact of different process parameters on conversion and selectivity is thoroughly evaluated. Kinetics evaluation showed that the reactivity of pentene is higher than that of hexene. Selectivity to jet-fuel range products > 98 % were achievable at low-to-moderate conversions (<50 %), while higher conversions (ca. 90 %) resulted in selectivities of ca. 75 %. Notably, the product distribution at iso-conversion was unaffected by temperature, pressure, and weight hourly space velocity, implicating that adjusting the conversion is the primary way to tune the selectivity of the Al-SBA-15 catalyst. This understanding of the oligomerization process opens the door for the research devoted on the oligomerization of complex olefin mixtures, mimicking the process stream of olefins production units, in order to achieve “biomass to jet-fuel” transformation.

The Role of Vacancies in a Ti2CTx MXene‐Derived Catalyst for Butane Oxidative Dehydrogenation

AbstractMXenes are a new family of 2D carbides or nitrides that have attracted attention due to their layered structure, tunable surface groups and high electrical conductivity. Here, we report for the first time that the Ti2CTx MXene catalyses the selective oxidative dehydrogenation of n‐butane to butenes and 1,3‐butadiene. This catalyst showed higher intrinsic activity compared to a commercial TiC and TiO2 samples in terms of C4 olefin formation rate. We propose that the stabilisation of structural vacancies and the change in composition (from a carbide to a mixed phase oxide) in the MXene causes its higher catalytic activity. These vacancies can lead to a higher concentration of unpaired electrons in the MXene‐derived material, enhancing its nucleophilic properties and favouring the production of olefins.

Hydrocarbon Synthesis from CO2 and H2 Using the Ultrafine Iron-Containing Catalytic Systems Based on Carbonized Cellulose

Carbon materials were formed by the hydrothermal carbonization of cellulose, which were used as support for carbon dioxide hydrogenation catalysts (Fe/C and Fe-Mn/C). In the presence of these catalytic systems, CO2 conversion reached 50%. It is shown that the manganese introduction into the Fe-containing catalytic system significantly affects the distribution of gaseous С1-С4 products and liquid С5+ hydrocarbons. Promotion leads to the suppression of methane formation and an increase in the proportion of C2-C4 light olefins in gaseous products, as well as to intensification of secondary processes with the formation of a significant amount of iso-structures in liquid products. The different distribution of С1-С6 alcohols in the oxygen-containing products on the Fe/C and Fe-Mn/C catalysts indicates the manganese effect on the routes of their formation.

Catalytic fast pyrolysis of cellulose over different metal-modified ZSM-5 zeolites for light olefins

Light olefins (C2H4, C3H6 and C4H8) are important chemical building blocks in modern energy and material system. In this study, the effects of different metal-modified ZSM-5 catalysts on the production of light olefins from cellulose fast pyrolysis were investigated in a fixed bed. Fe, La, Cu, Mg, Al and Ce modified ZSM-5 were prepared by the impregnation method, and then the derived modified ZSM-5 catalysts were characterized by different analytical instruments. The correlation between catalyst characteristics and the production of light olefins was explored. The results showed that the specific MFI-type structure of ZSM-5 remained intact after modification, and the surface area, pore volume and the amount of acid sites of catalysts varied. The highest light olefins yield was obtained over Cu-ZSM-5 (7.64 C-mol%), while the lowest was achieved over Mg-ZSM-5 (3.75 C-mol%). Moreover, the formation of light olefins can be promoted with the increasing of ZSM-5 other-pore volume and surface area, medium and strong acidity, and the decreasing of micro-pore volume and surface area, weak acidity. The results may share some light on the design of high efficiency ZSM-5 catalyst for high light olefins production.

Production of light olefins by catalytic hydrogenation of CO2 over Y2O3/Fe-Co modified with SAPO-34

Direct conversion of CO2 to hydrocarbons by hydrogenation was used in the production of light olefins. Hydrothermal coating and physical blending procedures were used to synthesize Y2O3/Fe-Co-SAPO-34 in this study. Based on the results from characterization, a unique micro-mesoporous structural composite with co-existing basic and acidic sites was obtained without any excessive close-fitting between the active sites in the physically blended composite. The catalyst’s overall selectivity for the light olefins was 82.6% with CO2 conversion of 19.9% for H2/CO2 of 3.0, with space velocity of 10 L.g.cat −1 h−1 at 400 °C and 20 bars. Furthermore, an increase in the number of acidic-basic sites, meso-microporous structures, alongside the synergetic effects of the compositephases over the catalyst without any support, improved the catalyst’s activity for CO2 conversion which in turn yielded higher C2=–C4= selectivity. The hybrid catalyst had a commendable stability within 80-hours of operation without losing its activity

Incorporation of water-derived hydrogen into methane during artificial maturation of source rock under hydrothermal conditions

To investigate the origin of CH bonds in thermogenic methane (CH4), a solvent-extracted sample of organic-rich Eagle Ford shale was reacted with heavy water (D2O) under hydrothermal conditions (350 bar) in a flexible Au-TiO2 cell hydrothermal apparatus at a water-to-rock ratio of approximately 5:1. Temperature was increased from 200 to 350 °C over the course of one month and the concentrations of aqueous species and methane isotopologues were quantified as a function of time. In general, production of hydrogen, CO2, alkanes, and alkenes increased with time and temperature. Methane formed during the early stages of the experiment at 200 °C was primarily C1H4 with some CH3D. With progressively higher temperatures, increasing proportions of deuterated isotopologues were produced. Near the end of the experiment, the concentration of CD4 exceeded that of all other isotopologues combined. These results suggest that competition between rates of kerogen-water isotopic exchange and natural gas generation may govern the D/H ratio of thermogenic gases. Furthermore, hydrogenation of kerogen by water may be responsible for hydrocarbon yields in excess of those predicted by conventional models of source rock maturation in which hydrocarbon generation is limited by the amount of organically bonded hydrogen.

Catalytic [2+2+2] Tandem Cyclization with Alkyl Substituted Methylene Malonate Enabling Concise Total Synthesis of Four Malagasy Alkaloids

Catalytic [2+2+2] Tandem Cyclization with Alkyl Substituted Methylene Malonate Enabling Concise Total Synthesis of Four Malagasy Alkaloids

Nonlinear Reactor Design Optimization With Embedded Microkinetic Model Information

Despite the success of multiscale modeling in science and engineering, embedding molecular-level information into nonlinear reactor design and control optimization problems remains challenging. In this work, we propose a computationally tractable scale-bridging approach that incorporates information from multi-product microkinetic (MK) models with thousands of rates and chemical species into nonlinear reactor design optimization problems. We demonstrate reduced-order kinetic (ROK) modeling approaches for catalytic oligomerization in shale gas processing. We assemble a library of six candidate ROK models based on literature and MK model structure. We find that three metrics—quality of fit (e.g., mean squared logarithmic error), thermodynamic consistency (e.g., low conversion of exothermic reactions at high temperatures), and model identifiability—are all necessary to train and select ROK models. The ROK models that closely mimic the structure of the MK model offer the best compromise to emulate the product distribution. Using the four best ROK models, we optimize the temperature profiles in staged reactors to maximize conversions to heavier oligomerization products. The optimal temperature starts at 630–900K and monotonically decreases to approximately 560 K in the final stage, depending on the choice of ROK model. For all models, staging increases heavier olefin production by 2.5% and there is minimal benefit to more than four stages. The choice of ROK model, i.e., model-form uncertainty, results in a 22% difference in the objective function, which is twice the impact of parametric uncertainty; we demonstrate sequential eigendecomposition of the Fisher information matrix to identify and fix sloppy model parameters, which allows for more reliable estimation of the covariance of the identifiable calibrated model parameters. First-order uncertainty propagation determines this parametric uncertainty induces less than a 10% variability in the reactor optimization objective function. This result highlights the importance of quantifying model-form uncertainty, in addition to parametric uncertainty, in multi-scale reactor and process design and optimization. Moreover, the fast dynamic optimization solution times suggest the ROK strategy is suitable for incorporating molecular information in sequential modular or equation-oriented process simulation and optimization frameworks.

DsCER26 Affects the Leaf Dehydration Tolerance of Rice by Altering Cuticular Wax Alkane Production without Affecting the Grain Fatty Acid Content

DsCER26 Affects the Leaf Dehydration Tolerance of Rice by Altering Cuticular Wax Alkane Production without Affecting the Grain Fatty Acid Content

Iron(III)‐Catalyzed Difluoroalkylation of Aryl Alkynes with Difluoroenol Silyl Ether in the Presence of Trimethylsilyl Chloride

AbstractThe reaction of non‐fluorinated silyl enol ether with alkyne is useful for the synthesis of β,γ‐unsaturated carbonyl compounds. However, most of the existing methods for realizing such organic transformation usually employ stoichiometric amounts of relatively expensive Lewis acids/metallic salts. Herein, an iron(III)‐catalyzed difluoroalkylation of aryl alkynes with difluoroenol silyl ether was developed. The reactions proceeded smoothly in the presence of a catalytic amount of iron(III) chloride, stoichiometric amounts of trimethylsilyl chloride, and 4 Å molecular sieves in dichloroethane (DCE) to afford the corresponding α‐alkenyl‐α,α‐difluoroketones in modest to good yields. Remarkably, among the various metallic salts screened, cheap and less‐toxic iron(III) salt was found to be the most efficient Lewis acid catalyst for the present reaction. In addition, in the absence of iron(III) chloride or trimethylsilyl chloride, either no reaction occurred or considerably reduced reaction performance was observed. Moreover, the use of Brønsted acid to replace iron(III) chloride as reaction catalyst failed to promote the reaction. The reaction could be scaled up and the obtained difluoroalkylated carbonyl compound serves as a versatile building block which could be subjected to late‐stage diversification to be converted into useful organic molecules containing CF2H and CF2CF2 moieties. Deuterated experiments showed that the proton in the generated alkene product should originate from trace amounts of water present in the reaction system.magnified image

Fischer-Tropsch synthesis to olefins boosted by MFI zeolite nanosheets.

Catalytic reactions are severely restricted by the strong adsorption of product molecules on the catalyst surface, where promoting desorption of the product and hindering its re-adsorption benefit the formation of free sites on the catalyst surface for continuous substrate conversion1,2. A solution to this issue is constructing a robust nanochannel for the rapid escape of products. We demonstrate here that MFI zeolite crystals with a short b-axis of 90-110 nm and a finely controllable microporous environment can effectively boost the Fischer-Tropsch synthesis to olefins by shipping the olefin molecules. The ferric carbide catalyst (Na-FeCx) physically mixed with a zeolite promoter exhibited a CO conversion of 82.5% with an olefin selectivity of 72.0% at the low temperature of 260 °C. By contrast, Na-FeCx alone without the zeolite promoter is poorly active under equivalent conditions, and shows the significantly improved olefin productivity achieved through the zeolite promoter. These results show that the well-designed zeolite, as a promising promoter, significantly boosts Fischer-Tropsch synthesis to olefins by accelerating escape of the product from the catalyst surface.

Development of shape selectivity theory of methanol-to-olefins reaction over small-pore zeolite molecular sieves

The methanol-to-olefins reaction is regarded as an important technology capable of meeting today’s rising demand for light olefins. The regioselective confinement effect of small-pore, cage-type zeolites on hydrocarbon pool intermediates results in strong shape selectivity determining the product olefin distribution. Despite decades of effort, a direct correlation between zeolite cage topologies and olefin selectivity distributions had remained elusive. The cage-defining ring theory is the first general catalytic shape selectivity theory that can predict the selectivity distribution of product light olefins from the given crystallographic information of the small pore zeolite catalysts. This article outlines the development procedure of the cagedefining ring theory. To aid readers’ comprehension, brief introductions to the structures and properties of zeolites and related molecular sieves, which are an important class of ceramic catalysts, are also provided.

Cp*Co(III)-Catalyzed Selective C8-Olefination and Oxyarylation of Quinoline N-Oxides with Terminal Alkynes.

Herein we report Cp*Co(III)-catalyzed site-selective (C8)-H olefination and oxyarylation of quinoline N-oxides with terminal alkynes. The selectivity for C8-olefination and oxyarylation is sterically and electronically controlled. In the case of quinoline N-oxides (unsubstituted at the C2 position), only the olefination product was obtained irrespective of the nature of the alkynes. In contrast, oxyarylation was observed exclusively when 2-substituted quinoline N-oxides were reacted with 9-ethynylphenanthrene. However, alkynes with electron-withdrawing groups provided only olefination products with 2-substituted quinoline N-oxides. The developed strategy allowed a facile functionalization of quinoline N-oxides bearing natural molecules and an estrone-derived terminal alkyne to deliver the corresponding olefinated and oxyarylated products. To understand the reaction mechanism, control experiments, deuterium-labeling experiments, and kinetic isotope effect (KIE) studies were performed.