Catalysts For Dehydrogenation Of Ethylbenzene Research Articles

A novel high-efficiency In-based catalyst for ethylbenzene dehydrogenation with CO2

A novel high-efficiency In-based catalyst for ethylbenzene dehydrogenation with CO2

Promotional effect and mechanism of SiO2 on Cr-Al2O3 catalysts for N2O-assisted oxidative dehydrogenation of ethylbenzene

A series of Cr-SiO2-Al2O3 (abbreviated as Cr-Si-Al) catalysts were synthesized using an evaporation induced self-assembled (EISA) method and applied to the N2O-assisted dehydrogenation of ethylbenzene (EB), offering a versatile solution for greenhouse gas recycling and a novel pathway for styrene (ST) production. Notably, the Cr-5Si-Al catalyst calcinated at 850 °C exhibited remarkable performance with a high EB conversion of 71% and a good ST selectivity of 62%, resulting in an optimal ST yield of nearly 44%. To elucidate the impact of calcination temperature and reveal the underlying promoting mechanism, numerous types of characterization particularly in-situ DRIFTS were used. Results indicated that the Cr-5Si-Al-850 catalyst possessed a distinctively ordered mesoporous structure, which improved the specific surface area and facilitated the dispersion of active species. The interaction among the multiple species in the catalyst was enhanced under the high calcination temperatures, leading to an increased ratio of Cr6+ and Oα, and thus promoting the dehydrogenation of EB. Furthermore, in situ DRIFTS revealed two favorable reaction pathways: one involving the reaction between adsorbed N2O and EB, and the other involving the reaction between adsorbed EB and N2O. These pathways led to the formation of a similar intermediate, observed at a wavenumber of 1285 cm−1. The improved adsorption of EB played a pivotal role in the excellent catalytic performance of the Cr-5Si-Al-850 catalyst.

Amorphous phosphorus oxynitride as a robust catalyst for steam-free direct dehydrogenation of ethylbenzene to styrene: effect of calcination temperature

A metal-free catalyst of phosphorus oxynitride (simplified as PNO) for direct dehydrogenation (DDH) of ethylbenzene was synthesized via calcinating hexachlorocyclotriphosphazene (HCCP) under an ammonia–oxygen atmosphere.

Ce-promoted Fe-K-Mg catalyst and its application in dehydrogenation of ethylbenzene

The continuous pursuit of green, low-carbon, and efficient processes in catalysis necessitates a deep understanding of catalytic reaction mechanisms and the structure-performance relationship of catalysts. Styrene, a vital monomer in the chemical industry, is primarily produced through the catalytic dehydrogenation of ethylbenzene over Fe-based catalysts. This study prepared a series of Fe-K-Mg catalysts promoted with different CeO2 contents. Various techniques such as mercury intrusion, particle strength tests, scanning electron microscopy, Raman spectroscopy, X-ray diffraction, Mössbauer spectroscopy, and temperature-programmed techniques were employed to characterize the catalysts' physical properties, surface, and bulk structures. The results indicate that the bulk density and crush strength of the catalyst are closely related to the pore structure and grain size of potassium β-ferrite. The surface of the Ce-promoted catalyst contains potassium β-ferrite KFe11O17, cerium dioxide, and potassium carbonate, while the bulk structure consists of potassium β-ferrite and cerium dioxide. The addition of Ce enhances the catalytic activity of ethylbenzene dehydrogenation, but the selectivity of styrene shows the opposite trend. The Fe-K-Mg catalyst containing 12% CeO2 exhibited the highest single-pass yield of styrene, reaching 70.9%. This study also discusses the possible effect of CeO2 on the performance of the Fe-K-Mg catalyst for ethylbenzene dehydrogenation.

The promoting effect of boron oxide on the FeOx/Si3N4 catalyst for oxidative dehydrogenation of ethylbenzene

Stronger interaction created by B2O3 modification mitigates the oxygen reactivity of FeOx, promoting styrene selectivity in the oxidative dehydrogenation of ethylbenzene.

A study on the catalytic role of Ce-Co species and coke deposited on ordered mesoporous Al2O3 in N2O-assisted oxidative dehydrogenation of ethylbenzene

The ordered mesoporous Al2O3 material was employed as support to prepare the CeO2-Co3O4 binary oxide catalysts for N2O-assisted oxidative dehydrogenation of ethylbenzene (EB), which was treated both as an effective method of styrene (ST) production and a high value-added utilization of the greenhouse gas. The catalytic performance was observed for the optimal 0.3Ce-7Co/OMA catalyst, which achieved 52.1% EB conversion with 88.7% selectivity toward ST at temperature as low as 500 ºC, far exceeding any other reported catalyst systems. Characterization results showed that an increase in the Co content led to a partial destruction of the order degree of pores, but maintained the mesoporous structure. The Ce modification not only decreased the particle size (<12 nm), considerably boosting the specific surface area, but also weakened the Co-O bond, making more O species available for the EB conversion. Studies on the carbon deposition formed during the catalytic runs revealed that the carbon deposited at the initial stage of reaction acted directly as the catalytically active sites enhanced the EB conversion. As the reaction progressed, the dynamic equilibrium between carbon deposition and burning relieved the loss of active sites and maintained the stability of catalyst activity. In addition, the excellent regeneration property of 0.3Ce-7Co/OMA catalyst indicated that N2O, which was used as an oxidizing agent, protected the catalyst against the formation of inactive carbonaceous deposition.

Potassium-promoted single-atom Co-N-C catalyst for direct dehydrogenation of ethylbenzene

Potassium-promoted single-atom Co-N-C catalyst for direct dehydrogenation of ethylbenzene

Introducing Co–O Moiety to Co–N–C Single-Atom Catalyst for Ethylbenzene Dehydrogenation

Introducing Co–O Moiety to Co–N–C Single-Atom Catalyst for Ethylbenzene Dehydrogenation

Remarkable Support Effect on the Reactivity of Sn-Based Catalyst for Ethylbenzene Dehydrogenation

Remarkable Support Effect on the Reactivity of Sn-Based Catalyst for Ethylbenzene Dehydrogenation

Superior performance of K/Co2AlO4 catalysts for the oxidative dehydrogenation of ethylbenzene to styrene with N2O as an oxidant

This study explored the feasibility of coupling N2O decomposition with ethylbenzene (EB) oxidative dehydrogenation, as an alternative approach for greenhouse gas elimination and styrene (ST) production, on the Co-Al mixed oxides and K-modified catalysts. It was found that N2O could decompose completely over the K/Co2AlO4 catalyst, accompanied with 62.0% of EB conversion and 85.1% of styrene selectivity, which were much better than the existing catalyst systems for EB oxidative dehydrogenation. Characterization results showed that despite the decreased specific surface area of the catalysts with increasing the Co/Al molar ratio, the improved reducibility, the reduced acid properties as well as the higher ratio of Co3+/Co2+ were responsible for the enhanced performance. The K modification not only changed the electronic properties of active metal, resulting from the charge transfer from K cation to the Co species, but also weakened the binding energy of Co3+-O−, leading to the complete decomposition of N2O. Furthermore, the optimized strong acid properties inhibited the dealkylation or ring-opening reactions and significantly reduced the coke deposition on the catalyst surface, thus improving the ST selectivity.

Plastering Sponge with Nanocarbon-Containing Slurry to Construct Mechanically Robust Macroporous Monolithic Catalysts for Direct Dehydrogenation of Ethylbenzene.

Nanocarbons have shown great potential as a sustainable alternative to metal catalysts, but their powder form limits their industrial applications. The preparation of nanocarbon-based monolithic catalysts is a practical approach for overcoming the resulting pressure drop associated with their powder form. In our previous work, a ploycation-mediated approach was used to successfully prepare nanocarbon-containing monoliths. Unfortunately, because there are no macropores in the monolith, it needs to be crashed into millimeter-sized particles before application. Therefore, developing a facile method for preparing mechanically robust nanocarbon-based macroporous monolithic catalysts is vital but still challenging. Herein, evoked by swallows building their nests, we report an approach for successfully preparing a mechanically robust nanodiamond-based macroporous monolith catalyst by plastering melamine sponge (MS) with a slurry composed of nanodiamonds (NDs) and poly(imidazolium-methylene) chloride (PImM) followed by an annealing process. The macroporous monolith catalyst (ND/NCMS-NCPImM) containing NDs well dispersed in N-doped carbon is mechanically robust with enriched macroscopic pores. It exhibits outstanding catalysis toward ethylbenzene to styrene through a direct dehydrogenation reaction with a high styrene rate in a steady state (5.50 mmol g-1 h-1) and high styrene selectivity (99.5%). ND/NCMS-NCPImM shows much higher activity than powder ND by 1.9 fold. In addition, this work solves the significant problem of large pressure drop encountered with conventional powdered nanocarbon catalysts in the flow reactor. This work not only creates an excellent nanodiamond-based macroporous monolithic ethylbenzene direct dehydrogenation catalyst but also presents a promising avenue for preparing other macroporous monolithic catalysts for diverse transformations.

Changes in the physicochemical and catalytic properties of iron-potassium catalysts during their operation in a reactor for ethylbenzene to styrene dehydrogenation at PJSC «Nizhnekamskneftekhim»

The paper presents the results of studying the iron-potassium catalysts for dehydrogenation of ethylbenzene (EB) to styrene, both fresh and spent, under industrial conditions: Cat-1 (imported), Cat-2 and Cat-3 (domestic). The initial samples are the multiphase systems consisting of potassium ferrites, hematite and cerianite (CeO2). After two years of operation, the phase composition of the catalysts was represented mostly by magnetite and cerianite, and potassium (K+) content in Cat-1, Cat-2 and Cat-3 samples decreased by 40, 20 and 26 %, respectively. Therewith, the Cat-2 sample retained a uniform K+ distribution in the spent catalyst grain. According to XRD data, the coherent scattering region (CSR) of CeO2 crystals in this sample did not change significantly. In the Cat-3 sample, the CSR size of CeO2 crystals decreased from 302 to 110 Å, while in Cat-1 it increased from 284 to 419 Å. After a two-year operation, the highest EB conversion equal to 72.1 % was observed on the Cat-2 sample, whereas on Cat-3 it decreased from 72.3 to 57.4 %. A 6÷11-fold decrease in the crushing strength was found for the spent samples, which made them unsuitable for further application.

In situ growth of phosphorus-doped boron nitride on commercial alumina as a robust catalyst for direct dehydrogenation of ethylbenzene

The obtained PBN@Al2O3(N) synthesized by in situ growth of thin PBN layers on commercial Al2O3 exhibited a significantly improved stability with relatively high ethylbenzene conversion and styrene selectivity.

Highly efficient and stable ordered mesoporous Ti-Al composite oxide catalyst for oxidative dehydrogenation of ethylbenzene to styrene with CO2

Ordered mesoporous Ti-Al composite oxides (OMTA-x) with variable Al/Ti atomic ratios have been prepared by a facile approach, and were evaluated as catalysts for oxidative dehydrogenation of ethylbenzene to styrene with CO2 (CO2-ODEB). Compared to Al2O3-supported titania catalyst, the resultant catalysts OMTA-x displayed inspiringly improved catalytic performance. For example, catalyst OMTA-2 demonstrated notable activity up to 20 h with maximum styrene yield of 69.4%, even after five times regeneration by calcination. The superior catalytic performance of OMTA-x can be attributed to the highly homogenous dispersion of Ti, the obviously improved surface acidity and redox properties, and the excellent textural and structural properties. The bridging oxygen in the surface Ti4+OAl3+ bonds with enhanced reactivity with H were concluded as the critical active sites for dehydrogenation of ethylbenzene, and new understanding for the development of TiO2-based catalysts with superior catalytic activity, stability, and reusability for CO2-ODEB was provided.

Research on ethylbenzene dehydrogenation over the Fe-Al-based catalysts in a circulating fluidized-bed unit

BackgroundIn the traditional ethylbenzene dehydrogenation process, much superheated steam is needed to ensure the activity and stability of the catalyst, inevitably leading to high energy consumption. MethodsA novel ethylbenzene dehydrogenation process based on a circulating fluidized bed (CFB) reactor was used for the ethylbenzene dehydrogenation reaction under a low steam-to-oil ratio. In this work, a series of Fe-Al-based catalysts were prepared by a sol-gel method and the effect of alumina content on the catalytic performance of Fe-Al-based catalyst for ethylbenzene dehydrogenation was investigated. Significant findingsAmong a series of Fe-Al-based catalysts, the FeAl40 catalyst (the Fe-Al-based catalyst with 40 wt. % alumina) had the highest dehydrogenation activity and suitable attrition resistance for the CFB reactor. Further investigation found that the adding alumina could inhabit the formation of KFe11O17, leading to poor stability. Interestingly, the high activity of the FeAl40 catalyst could be completely recovered through a reaction-regeneration operation. Compared with the conventional ethylbenzene dehydrogenation process, the CFB process benefits from high activity, low steam-to-oil ratio and no induction period. Consequently, the FeAl40 catalyst had high dehydrogenation activity (∼51 wt. % yield of styrene) and low preparation cost, showing an extraordinary potential for industrial application.

A Highly Selective Metal‐Free Boron‐Based Catalyst for Oxidative Dehydrogenation of Ethylbenzene

Main observation and conclusionOxidative dehydrogenation of ethylbenzene is considered as an alternative route to styrene because of its exothermic and irreversible reaction nature, but encounters low styrene selectivity due to the deep‐oxidation over metal oxide‐based catalysts. Herein, we reported that a metal‐free boron‐based catalyst consisting of boron phosphate and boron nitride (BPO4/BN) exhibited high activity and selectivity in oxidative dehydrogenation of ethylbenzene to styrene. High selectivity of styrene (95.1%) was achieved at 27.7% ethylbenzene conversion level over the optimized BPO4/BN catalyst. The tetra‐coordinated boron (BO4) species of BPO4 was speculated to be responsible for the ODH of ethylbenzene, and a synergistic effect between BPO4 and BN can remarkably improve the catalytic performance of the BPO4/BN catalyst. The optimized BPO4/BN catalyst showed a higher styrene formation rate of 4.0 mmol gcat−1·h−1, compared individually to BPO4 (2.8 mmol·gcat–1·h–1) and BN (0.5 mmol·gcat–1·h–1).

Phosphorus-doped h-boron nitride as an efficient metal-free catalyst for direct dehydrogenation of ethylbenzene

The N2PO and N3P–OH sites of PBN synergistically catalyzed the direct dehydrogenation reaction of ethylbenzene with a styrene production rate of 6.63 mmolST g−1 h−1 even after 100 h.

Study of oxidative dehydrogenation of ethylbenzene with CO2 on supported CeO2-Fe2O3 binary oxides

Nano-sheets Al2O3 supported CeO2-Fe2O3 binary oxides were prepared by the vacuum impregnation method. The structural and textural properties were characterized by pertinent techniques, and the materials were evaluated as catalysts for the oxidative dehydrogenation of ethylbenzene with carbon dioxide (CO2-ODEB). The characterization results show that all samples maintain the hierarchical structure, and CeO2-like and Fe2O3-like solid solutions were formed when changing the Ce-to-Fe molar ratio. The catalytic performances indicate that CeO2-Fe2O3 binary oxides were effective for CO2-ODEB, and the activity is determined by mobile oxygen, which can facilitate the dehydrogenation process. The DFT studies further identified the reaction pathway and rate-determining step. The inter-transmission of oxygen species and the presence of CO2 refill the oxygen vacancies and restore the redox cycle of CeO2-Fe2O3 binary oxides.

Improved catalytic properties of Co3O4-impregnated La2O3/MgO over Co3O4/MgO catalyst in the oxidative dehydrogenation of ethylbenzene

A series of lanthanum oxide (La2O3—2–14 wt%)-encapsulated Co3O4/MgO catalysts and bare Co/MgO solid oxides were prepared by wetness impregnation method. Among all catalysts, La2O3-promoted Co3O4/MgO (CM) was found to be remarkable in terms of superior promotional effect of La oxide species. Therefore, La2O3-incorporated Co3O4/MgO (LCM) catalysts afforded unusual catalytic activity efficiency with respect to high EB conversion and styrene selectivity due to the synergistic effect of Co–La species. By contrast, bare Co3O4/MgO solid oxide (CM) catalyst afforded low EB conversion with mild catalytic activity due to the absence of promotional role of La oxide.

Nonmetallic boron nitride embedded graphitic carbon catalyst for oxidative dehydrogenation of ethylbenzene

Nonmetallic BN embedded graphitic carbon hybrid had abundant carbonyl groups as the active site and enriched BO species as the oxygen adsorption sites, exhibiting a high catalytic performance for oxidative dehydrogenation of ethylbenzene to styrene with high yield.