Production Of Olefins Research Articles

Interpretation of interactions between low rank coal and polyethylene during co-pyrolysis from the bond cleavage perspective

Co-pyrolysis of low rank coal and plastic to extract oil is one of effective methods for solving the white pollution. The interactions between coal and plastic during the co-pyrolysis process significantly improve the yield and quality of tar. However, the understanding of the interactions during co-pyrolysis from microscopic perspective is still scarce. The effect of polyethylene on the cleavage of covalent bonds during Hami coal pyrolysis was investigated by combining TG-MS, Py-TOF-MS and ReaxFF MD simulations. The results showed that derivative DTG curves can be decoupled into 6 sets of covalent bonds. The addition of PE had no effect on the breakage of Cal-O bonds in HM from the chemical perspective, but it promoted the breakage of Cal-Cal bonds in both HM and PE. Furthermore, after the addition of PE, the breakage peak temperature of Car-Cal in HM to shift towards a higher temperature (from 532 to 545 °C), and the peak area decreased from 13.12 % to 9.22 %. According to in-situ Py-TOF-MS analysis, the addition of PE can promote the breaking of Cal-Cal bonds, resulting in the increase of alkene products and radicals such as alkene, alkadienes and alkane radicals. Meantime, the long-chain alkenes produced by PE cracking coats on the surface of HM during co-pyrolysis, which hinders the pyrolysis of the broken Cal-Car bonds in its structure and leads to the reduction of aromatics. Moreover, the results of ReaxFF MD simulations further confirmed that the results of experimental.

Alteration of acidity and porosity of Beta zeolite using fibrous silica for light olefin production

Traditional olefin production heavily depends on fossil fuels, which are a significant contributor to environmental issues. Methanol to olefin (MTO) is among non-fossil fuel alternatives to produce olefinic products from abundant resources, such as biomass, coal, and natural gas. Nevertheless, the catalytic reaction of MTO over commercial zeolite catalysts is hindered by their low activity, mainly due to the micropore structure and excessive acidity within the zeolite. Herein, Beta zeolite with fibrous silica structure was successfully synthesized via the microemulsion and Beta seed-assisted method. The catalysts were characterized using FESEM, N2 physisorption, and ammonia-TPD. FESEM results revealed a well-ordered spherical morphology of HFBETA with uniform particle size distribution. In surface analysis, the HFBETA exhibits higher BET surface area and mesopore volume compared to commercial HBETA by 35% and 86%, respectively. The introduction of fibrous silica within the Beta structure led to a significant drop in the acidity of the catalyst, as shown in ammonia-TPD results. These led to superior catalytic performance of HFBETA in the MTO process.

Production of Olefins by Dehydrogenation of Propane over Fe Modified ZSM-5

Production of Olefins by Dehydrogenation of Propane over Fe Modified ZSM-5

Green ethylene production in the UK by 2035: a techno-economic assessment

A techno-economic analysis comparing thermocatalytic and electrocatalytic routes to green ethylene from air-captured CO2 and off-shore wind electricity.

Flow chemistry enhances catalytic alcohol-to-alkene dehydration

Flow chemistry helped optimise the conversion of a branched primary alcohol to an alkene. Mass balance was achieved through the elimination of by-products, including alkene oligomers, and the setup could be optimised to give up to 98% alkene product.

Recent advances on metal–organic frameworks for deep purification of olefins

The efficient removal of trace impurities is significant for the production of high-purity olefins. This review summarizes the latest advancements in the deep purification of ethylene and propylene using MOF materials.

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. The number of acidic sites and the...

Comparative microwave catalytic pyrolysis of cellulose and lignin in nitrogen and carbon dioxide atmospheres

In this paper, a cleaner pyrolysis strategy combining microwave heating, catalyst and carbon dioxide was explored for converting biomass components into higher quality products. Catalytic pyrolysis was more favorable for the decomposition and conversion of complex biomass structures. For furfural residue pyrolysis, potassium sulfate contained in sample served as the main catalytic component. Potassium sulfate promoted the increase of phenols in bio-oil. Notably, carbon dioxide atmosphere promoted the decomposition of substances and exerted a significant effect on biomass pyrolysis, which increased bio-oil yield and declined gas yield. When the pyrolysis atmosphere was changed from nitrogen to carbon dioxide, the ID/IG ratio decreased from 1.07 to 0.74, indicating that carbon dioxide decreased defect structure in biochar. Carbon dioxide enriched the porous structure and surface roughness of biochar. Also, carbon dioxide as a carrier gas was found to be more effective than nitrogen in improving the heating values of biochar and the acidity of bio-oil under carbon dioxide was lower than that under nitrogen, which was conducive to the subsequent utilization of biochar and bio-oil. Carbon dioxide promoted the production of alcohols, alkenes, and alkanes in bio-oil. Beneficially, the interaction of cellulose and lignin inhibited the release of hydrogen chloride. At last, this study also provides insights into the mechanism of catalyst and CO2 on biomass microwave pyrolysis.

Selective production of bicyclic alkanes as high-density fuel additives by coupling lignocellulose-derived furanics and phenolics

High-density bicyclohexyl hydrocarbon fuel additives were selectively synthesized from lignin-derived monophenolics and carbohydrate-derived furanics.

The effect of Si/Al ratio of ZSM-12 zeolite on its morphology, acidity and crystal size for the catalytic performance in the HTO process.

In this research, ZSM-12 zeolite with six Si/Al ratios (20 to 320) was synthesized by a hydrothermal method and systematically investigated. The physicochemical properties of the synthesized nano zeolites were evaluated and compared by XRD, FE-SEM,ICP-AES, NH3-TPD, BET, FT-IR, and TGA analyses. The results show that when the Si/Al ratio increases, the amount of microcrystals increases with the dominant competitive phase of cristobalite by decreasing the MTW phase. The catalytic assessment of synthesized zeolites in the (n-hexane to olefins) HTO process in a fixed bed reactor under atmospheric pressure and WHSV equal to 4 h-1 at 550 °C was evaluated and various parameters such as selectivity towards light olefins, P/E ratio, production of light alkanes, and aromatic compounds (BTX) were investigated. The result of the n-hexane to olefins process indicated that the presence of cristobalite as an impurity phase strongly affects the activity of the catalysts. The Z80 zeolite, with a Si/Al ratio of 80, corresponds to the pure form of ZSM-12 and exhibits the highest light olefin yield at 52.5%. This zeolite demonstrates superior propylene selectivity (P/E = 1.75) owing to its well-suited pore structure, wide channels, and optimal acidity derived from the MTW zeolite. On the other hand, zeolite Z320 has a lower light olefin yield (19.4%) and a lower P/E (1.1) ratio. In addition, according to the results of the TGA analysis, the content of coke on the Z80 catalyst after the catalytic reaction is much less than other catalysts after the catalytic reactor test.

Soybean oil pyrolysis in a continuous bench-scale reactor for light olefin production

Soybean oil pyrolysis in a continuous bench-scale reactor for light olefin production

Chemically exfoliated boron nanosheets for efficient oxidative dehydrogenation of propane.

Oxidative dehydrogenation of propane (ODHP) is a promising technique for producing propene due to its low operative temperature and coke-resistant feature. Recently, boron-based catalysts have been widely investigated for ODHP owing to their brilliant performance. Herein, we report that boron in the form of nanosheets can be prepared feasibly by exfoliating layered MgB2 with hydrochloric acid, and can efficiently and stably catalyze ODHP. At 530 °C, the catalyst exhibits propene and ethene selectivities as high as 63.5% and 18.4%, respectively, at a 40% propane conversion. The olefin productivity reaches 2.48 golefin gcat-1 h-1, superior to the commercial h-BN and other reported boron-based catalysts. Even after testing for 100 h at 530 °C, the catalyst still maintains excellent stability. This work expands the effective boron-based catalyst family for ODHP and demonstrates the great potential of the new type of 2D material-boron nanosheet for energy and catalytic applications.

Chemical recycling of polyolefins via ring-closing metathesis depolymerization.

The current insufficient recycling of commodity polymer waste has resulted in pressing environmental and human health issues in our modern society. In the quest for next-generation polymer materials, chemists have recently shifted their attention to the design of chemically recyclable polymers that can undergo depolymerization to regenerate monomers under mild conditions. During the past decade, ring-closing metathesis reactions have been demonstrated to be a robust approach for the depolymerization of polyolefins, producing low-strain cyclic alkene products which can be repolymerized back to new batches of polymers. In this review, we aim to highlight the recent advances in chemical recycling of polyolefins enabled by ring-closing metathesis depolymerization (RCMD). A library of depolymerizable polyolefins will be covered based on the ring size of their monomers or depolymerization products, including five-membered, six-membered, eight-membered, and macrocyclic rings. Moreover, current limitations, potential applications, and future opportunities of the RCMD approach will be discussed. It is clear from recent research in this field that RCMD represents a powerful strategy towards closed-loop chemical recycling of novel polyolefin materials.

Electrocatalytic Semihydrogenation of Terminal Alkynes Using Ligand-Based Transfer of Protons and Electrons.

Alkyne semihydrogenation is a broadly important transformation in chemical synthesis. Here, we introduce an electrochemical method for the selective semihydrogenation of terminal alkynes using a dihydrazonopyrrole Ni complex capable of storing an H2 equivalent (2H+ + 2e-) on the ligand backbone. This method is chemoselective for the semihydrogenation of terminal alkynes over internal alkynes or alkenes. Mechanistic studies reveal that the transformation is concerted and Z-selective. Calculations support a ligand-based hydrogen-atom transfer pathway instead of a hydride mechanism, which is commonly invoked for transition metal hydrogenation catalysts. The synthesis of the proposed intermediates demonstrates that the catalytic mechanism proceeds through a reduced formal Ni(I) species. The high yields for terminal alkene products without over-reduction or oligomerization are among the best reported for any homogeneous catalyst. Furthermore, the metal-ligand cooperative hydrogen transfer enabled with this system directs the efficient flow of H atom equivalents toward alkyne reduction rather than hydrogen evolution, providing a blueprint for applying similar strategies toward a wide range of electroreductive transformations.

Stereodivergent atom transfer radical addition of α-functionalized alkyl iodides to alkynes: a strategy for selective synthesis of both E- and Z-iodoalkenes.

The geometrical control of atom transfer radical addition (ATRA) reactions to alkynes poses significant challenges. Herein, we present a uniform solution by developing a stereodivergent synthetic method for both isomers of the resulting alkene products, starting from the same materials. The synthesis of the thermodynamically more stable isomer utilizes the strategy of uphill catalysis while the accumulation of the less stable isomer is facilitated by a manganese-catalyzed iodo-abstraction/radical rebound process, taking advantage of its reversibility. Various substituted alkyl iodides can be used to provide easy access to both isomers of iodoalkene products with valuable functional groups such as CF3, CF2H, CN, ester, or amide at the allylic position.

Exponentially enhanced photocatalytic alkane production from biomass-derived fatty acid decarboxylation via self-heating induced conformational inversion

Heating is the most convenient means to enable unfavorable chemical reactions to scale application, but photocatalysis rarely uses it because its driving force has always been identified as the intensity...

Production of light olefins and monocyclic aromatic hydrocarbons from the pyrolysis of waste plastic straws over high-silica zeolite-based catalysts

Owing to the ever-increasing generation of plastic waste, the need to develop environmentally friendly disposal methods has increased. This study explored the potential of waste plastic straw to generate valuable light olefins and monocyclic aromatic hydrocarbons (MAHs) via catalytic pyrolysis using high-silica zeolite-based catalysts. HZSM-5 (SiO2/Al2O3:200) exhibited superior performance, yielding more light olefins (49.8 wt%) and a higher MAH content than Hbeta (300). This was attributed to the increased acidity and proper shape selectivity. HZSM-5 displayed better coking resistance (0.7 wt%) than Hbeta (4.4 wt%) by impeding secondary reactions, limiting coke precursor formation. The use of HZSM-5 (80) resulted in higher MAHs and lower light olefins than HZSM-5 (200) because of its higher acidity. Incorporation of Co into HZSM-5 (200) marginally lowered light olefin yield (to 44.0 wt%) while notably enhancing MAH production and boosting propene selectivity within the olefin composition. These observations are attributed to the well-balanced coexistence of Lewis and Brønsted acid sites, which stimulated the carbonium ion mechanism and induced H-transfer, cyclization, Diels-alder, and dehydrogenation reactions. The catalytic pyrolysis of plastic straw over high-silica and metal-loaded HZSM-5 catalysts has been suggested as an efficient and sustainable method for transforming plastic waste materials into valuable light olefins and MAHs.

Maximizing light olefin production via one-pot catalytic cracking of crude waste plastic pyrolysis oil

Energy-efficient processes for converting polyolefinic waste plastics into light olefins are critical for mitigating environmental pollution and reducing carbon emissions. In this study, an alternative recycling scheme, the catalytic cracking of crude waste plastic pyrolysis oil (WPPO) over microspherical P-modified steam-treated ZSM-5 (ms-P-HZSM5-S), was demonstrated and compared to a state-of-the-art commercial scheme, the thermal cracking of a hydrotreated naphtha range of WPPO. The C2–C4 olefins yield achieved by the catalytic WPPO cracking (56.6 wt%) exceeded those achieved by the thermal WPPO cracking (36.1 wt%), thermal naphtha cracking (23.1 wt%), and catalytic naphtha cracking (29.7 wt%), which indicated the superiority of WPPO over naphtha as a feedstock. However, during a deactivation test over ms-P-HZSM5-S, coke accumulation resulted in a rapid decline in the yields of ethylene (from 17.2 to 14.6 wt%), propylene (from 25.8 to 23.6 wt%), and benzene, toluene, and xylenes (from 16.1 to 13.4 wt%) after a reaction time of 810 s (temperature = 680 °C, weight hourly space velocity = 16 h−1). Nevertheless, the catalytic performance was fully restored through regeneration in air at 730 °C, which confirmed the viability of continuous operation involving successive reaction–regeneration cycles. These findings can be leveraged to devise a new approach, the catalytic cracking of WPPO integrated with a continuous regeneration (e.g., circulating fluidized bed reactor) system, which could offer several advantages over the commercial strategy, including the posttreatment-free utilization of the entire WPPO range, higher light olefins yields, continuous coke removal, reduced energy consumption, and non-necessity of H2.

Unraveling the complex interactions between structural features and reactivity of iron-based catalysts across various supports in the synthesis of light olefins from syngas

This study provides a systematic examination of the hydrogenation of CO over mixed Fe-Co-K catalysts on SiO2, TiO2, and Al2O3 supports for the production of light olefins. The unsupported FeCo/K catalyst, while demonstrating selectivity towards light olefins, yielded a low space–time yield (STY) for hydrocarbon formation. Additionally, the Fe3O4 phase in the spent catalyst appeared to promote an increased rate of CO2 formation. The SiO2-supported catalyst showed a high dispersion of isolated Fe particles but were less effective in synthesizing light olefins. The interaction of Fe species with TiO2 support was found to be strong, impeding the formation of the active Fe5C2 phase and thus lowering the yield of light olefins. Al2O3 stood out as the most effective support, ensuring an optimal dispersion of the Fe phase with minimal interaction, enabling the Fe to effectively synergize with K. This synergy promoted the formation of the iron carbide Fe5C2 phase, essential for efficient CO hydrogenation to light olefins, and achieved a notable STY of 17.2 mmol gcat−1 h−1 at 360 °C and 20 bar. Long-term stability testing underscored the influence of reaction temperature on light olefins yield, with paraffin wax formation at 300 °C leading to catalyst deactivation through adsorption and accumulation. Conversely, at 360 °C, a distinct carbon layer was observed, forming an extended structure that did not directly cover the catalyst's surface. These findings contribute valuable knowledge for the custom development of catalysts tailored for light olefins production from syngas, offering a promising avenue for future research.

Tailoring olefin distribution via tuning rare earth metals in bifunctional Cu-RE/beta-zeolite catalysts for ethanol upgrading

Bioethanol to middle distillate technologies have offered a unique solution to produce renewable aviation fuel for decarbonizing the hard-to-electrify sectors. Here, we have developed the series of bimetallic Cu- and rare earth-containing (RE) Beta zeolite catalysts that yield high C3+ alkene selectivity from ethanol upgrading (>80% selectivity at ∼100% conversion, 623 K). The formation rates of butene isomers to C5+ alkenes are linearly correlated with the strength of Lewis acidic RE identity, which follows the sequence of Yb12/Beta >Y7/Beta > Gd12/Beta > Ce10/Beta > La12/Beta. Rate measurements indicate that the RE selection plays the vital role in altering the rate of the key competitive reactions within the ethanol-to-alkenes reaction network, namely C4 alcohol dehydration and C-C chain growth, which dictate alkene product distributions. These findings indicate a feasible and promising method for tailoring alkene product distributions from ethanol upgrading, which is of notable significance to the generation of renewable middle distillates.