Ethylbenzene Conversion Research Articles

Production of Styrene from Dehydrogenation of Ethylbenzene

AbstractA pseudo‐homogeneous model based on intrinsic rate equations for dehydrogenation of ethylbenzene to styrene in an adiabatic fixed‐bed reactor is developed. Steam and ethylbenzene are the main reactants with styrene as the desired product, and benzene and toluene as by‐products. Styrene production is an endothermic reaction depends on various factors such as temperature, pressure, steam to ethylbenzene ratio, styrene to ethylbenzene ratio in feed. These factors affects the properties like styrene selectivity, ethylbenzene and by‐product conversion etc. The development of the mathematic model includes the application of mass balance, energy balance, and basic thermodynamic relations, momentum balance, Langmuir and Hinshelwood model, Ergun relation, etc. The effects of temperature as well as of the steam‐to‐ethylbenzene and styrene‐to‐ethylbenzene molar ratios in the feed on the selectivity for styrene, ethylbenzene conversion, and conversion to by‐products are also evaluated. The maximum selectivity for styrene can be achieved at increased steam‐to‐ethylbenzene feed ratio and a lower ethylbenzene conversion.

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.

Catalytic synergistic effect of bis-ZSM-5 zeolite with different crystal sizes for xylene isomerization

High-performance xylene isomerization catalysts were prepared by physical mixing of two types of ZSM-5 after reasonable modification. Here, SZ/LZ catalysts were prepared by simple physical mixing of two modified Pt–3Si/SZ-5 and Mo/LZ-5 with different crystal sizes. The catalytic performance of the catalysts was evaluated in the mixed xylene isomerization reaction on a fixed bed. The catalysts were characterized by XRD, BET, SEM, TEM, XPS, Py-IR, NH 3 -TPD and probe molecular reactions. The results demonstrated that the deposition of silica finely adjusted the size of the pore opening and passivated the acid sites on the external surface of the SZ-5 zeolite. The loading of MoO 3 reduced the distribution of acidic site density of LZ-5. The reaction sites of ethylbenzene, m-xylene and o-xylene were precisely distributed by the 2SZ/8LZ catalyst. Optimizing the mixing ratio and reaction temperature of the catalysts further improved their synergistic catalysis. High EB conversion rate (74.9%), high PX yield (23.3%) and low xylene loss (1.41%) were obtained by controlling the reaction path of ethylbenzene, m-xylene and o-xylene. High performance xylene isomerization catalysts (2SZ/8LZ) were obtained by a simple mixture of the dealkylation catalyst (Pt–3Si/SZ-5) and the isomerization catalyst (Mo/LZ-5). It demonstrates excellent catalytic activity in mixed xylene isomerization reactions. • The SiO 2 deposition effectively covers the acidic sites on the external surface and adjusts the pore-opening size. • The modification of MoO 3 reduces the acidic site density of LZ-5 with large crystal size and improves the MX and OX isomerization activity. • The ethylbenzene conversion rate, xylene loss rate and PX yield of 2SZ/8LZ reached 74.9%,1.41% and 23.3% at 380 °C, respectively.

Ultrasonic Synthesis of Al‐SBA‐15 Nanoporous Catalyst for t-Butylation of Ethylbenzene

Mesoporous Al‐SBA‐15 (Si/Al = 25) catalysts were synthesised by the ultrasonic (US) irradiation method at different time durations (1, 3, and 5 h) using the pluronic P123 triblock copolymer as a template. The synthesised catalysts were examined in detail by XRD, ICP‐AES, N2 adsorption‐desorption, SEM, TEM, FT‐IR, and TGA characterization techniques. The characterization results reveal that the catalysts possess a well‐ordered hexagonal mesoporous structure. The catalytic activity of synthesised materials was investigated in the tert-butylation of ethylbenzene at different reaction conditions, and their identified products are para-tert‐butylethylbenzene (p-tert‐BEB) and meta-tert‐butylethylbenzene (m-tert‐BEB). It was found that high ethylbenzene conversion (69%) is achieved at 200°C with high selectivity towards p-tert‐butylethylbenzene (80%). The optimum feed ratio (ethylbenzene: t‐butyl alcohol) was 1 : 2, and the feed rate was 2 ml/h for high conversion and product selectivity. All these synthesised Al‐SBA‐15 (US) catalysts are compared with hydrothermally synthesised Al‐SBA‐15 (HT) at the same reaction conditions.

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.

Continuous flow photooxidation of alkyl benzenes using fine bubbles for mass transfer enhancement

Selective photooxidation of alkyl benzenes was studied in a custom-built continuous flow photochemical reactor equipped with fine bubble generator and a low power UV light source. Fine bubbles of air were used as an oxidizing agent along with water-soluble sodium anthraquinone sulfonate as catalyst. The fine bubble containing slug-flow system using air was 1.4 times more efficient at lower feed-flow rate of 2 mL/min and 1.8 times more efficient at higher feed-flow rate of 5 mL/min. Ethylbenzene was selectively oxidized in continuous flow to acetophenone at room-temperature, with 90% ethylbenzene conversion and 92% selectivity to acetophenone, with a short residence time of 5 min. The enhanced gas/liquid mass transfer afforded by the fine bubble generator significantly increased reactor productivity, giving rise to high conversion and yield. Due to enhanced mass transfer and greater efficiency, compressed air can be used as oxidant instead of pure O2, thus alleviating potential safety concerns and making the process safer and more amenable for scale up.

High-efficient metal-free aerobic oxidation of aromatic hydrocarbons by N, N-dihydroxypyromellitimide and 1,4-diamino-2,3-dichloroanthraquinone

Metal-free organic catalytic system combining with N, N-dihydroxypyromellitimide (NDHPI) and 1,4-diamino-2,3-dichloroanthraquinone (DADCAQ) was developed for the selective oxidation of hydrocarbon. Being able to simultaneously show good catalytic activity for the oxidation of hydrocarbon and alcohol, NDHPI/DADCAQ was found to be efficient for the conversion of hydrocarbon to ketone. In addition, due to its specific molecular structure, NDHPI was found to be more stable and could supply a PIDNO (pyromellitimide N, N-dioxyl free radical) during the catalytic process. So, higher catalytic activity could be obtained than the famous NHPI even with only half usage, which resolved the problem of high usage (usually 10 mol%) for the organic N-OH compounds to some extent. With 5 mol% NDHPI and 1.25 mol% DADCAQ being used under the conditions of 110 °C and 0.3 MPa molecular oxygen for 7 h, high conversion of ethylbenzene (89.6%), tetralin (98.8%), indene (96.9%), and inert toluene (50.7%) could be selectively converted to the products of acetophenone (93.4%), α-tetralone (97.3%), 1-indanone (98.9%), and benzoic acid (92.4%), respectively.

A generalized approach to adjust the catalytic activity of borocarbonitride for alkane oxidative dehydrogenation reactions

The borocarbonitrides (BCNs) have exhibited enormous potential as non-metallic catalysts for alkane oxidative dehydrogenation (ODH) reactions. However, the poor electron transportation ability in BCN leads to a low reactivity of oxygen functional groups (CO and BOH). Herein, we present a generalized strategy to promote the catalytic activity of BCN through in situ encapsulation of transition-metal (Fe, Co, Ni) nanoparticles within BCN nanotubes (BCNNTs). Among them, individual metal particles themselves do not contribute directly on ODH reactions and mainly serve as electron modulators to tune the electron density of CO and BOH active sites on BCNNTs. As a result, catalytic activities of all metal@BCNNTs catalysts surpass pure BCN in ethylbenzene (EB) ODH reactions, among which Fe@BCNNTs displays a significant activity enhancement with 36 % EB conversion with the styrene (ST) selectivity remaining >98% under gentle reaction conditions. Structural and kinetic analyses proved that the promotion effect originated from the strong interactions between metal nanoparticles and BCNNTs. The theoretical calculations disclosed that the enhanced ODH activity was due to the electron transfer from the encapsulated metal to BCNNTs, which increases the electron transportation ability and electron density of BCNNTs, thus promoting the nucleophilicity of CO and BOH active sites, leading to the reduced activation energy barrier for CH bond dissociation. The present work sets forth the structure-function relationship, identifying opportunities for rational design of highly efficient BCN catalysts for ODH reactions.

Ethyl benzene oxidation under aerobic conditions using cobalt oxide imbedded in nitrogen-doped carbon fiber felt wrapped by spiral TiO2-SiO2

Carbon fiber felt (CFF) as a carbonaceous framework has received great attention in catalysis applications. In this work, a novel nanocomposite composed of cobalt oxide micro-sized particles (MPs) incorporated in nitrogen-doped carbon and wrapped by coil-like TiO2-SiO2 layer was fabricated through a co-assembly protocol including MPs implanting, hydrolysis and calcination steps. The structural properties and performance of the prepared Co/N-CFF@TiO2-SiO2 catalyst was evaluated by different techniques. Mechanical, chemical and thermal stabilities of CFF were stepwise improved and the results explain how the N-CFF matrix and strong spiral envelope promoted textural features in the final composite. Moreover, the catalyst exhibited good activity in oxidation of ethyl benzene by molecular oxygen. Under optimized conditions (130 °C, 12 h, 5 mL of ethylbenzene, 20 bar O2 pressure), the ethyl benzene conversion and acetophenone selectivity were 25% and 88%, respectively. The novel Co/N-CFF@TiO2-SiO2 catalyst showed excellent long-term stability over 6 consecutive cycles, which permits to consider it as an ideal platform for application at industrial scales due to its green and bulk nature.

Photo-fluorination of nanodiamonds catalyzing oxidative dehydrogenation reaction of ethylbenzene

Styrene is one of the most important industrial monomers and is traditionally synthesized via the dehydrogenation of ethylbenzene. Here, we report a photo-induced fluorination technique to generate an oxidative dehydrogenation catalyst through the controlled grafting of fluorine atoms on nanodiamonds. The obtained catalyst has a fabulous performance with ethylbenzene conversion reaching 70% as well as styrene yields of 63% and selectivity over 90% on a stream of 400 °C, which outperforms other equivalent benchmarks as well as the industrial K−Fe catalysts (with a styrene yield of 50% even at a much higher temperature of ca. 600 °C). Moreover, the yield of styrene remains above 50% after a 500 h test. Experimental characterizations and density functional theory calculations reveal that the fluorine functionalization not only promotes the conversion of sp3 to sp2 carbon to generate graphitic layers but also stimulates and increases the active sites (ketonic C=O). This photo-induced surface fluorination strategy facilitates innovative breakthroughs on the carbocatalysis for the oxidative dehydrogenation of other arenes.

One-pot pyrolysis method to fabricate Co/N co-doped hollow mesoporous spheres with carbon/silica binary shells for selective oxidation of arylalkanes

Hollow mesoporous silica spheres have an excellent application prospect in the field of catalysis due to high specific surface area, tunable pore size, structural stability and void-confinement effect. In this work, rasberry-like Co/N co-doped hollow mesoporous spheres with carbon/silica binary shells were synthesized by a facile one-pot pyrolysis method, and the catalysts with different properties can be obtained easily by adjusting the factors such as the pyrolysis temperature and the introduction approach of the active substance cobalt porphyrin. The results indicated that pyrolysis temperature could exert influence on the specific surface areas and defects of catalysts. Moreover, the active sites introduced through different ways played an important role in utilizing the enrichment effect of reactants originated from the void-confinement effect. As a result, the obtained catalysts showed remarkable activity and stability for selective oxidation of ethylbenzene under moderate reaction condition. Additionally, the optimal catalyst that achieved 95.9% ethylbenzene conversion and 99.3% acetophenone selectivity also exhibited outstanding catalytic performance for lots of arylalkanes. The superior performance was due to the large specific surface area and the well-dispersed active sites stabilized by the hollow structures with carbon/silica binary shells, which could maximize the enrichment of reactants to accelerate the reaction.

Fe assisted Co-containing hydrotalcites catalyst for the efficient aerobic oxidation of ethylbenzene to acetophenone

Various Co-containing hydrotalcites (LDHs) with different cations (Fe, Al, Ga and MgAl) were prepared, characterized, and investigated in the aerobic oxidation of ethylbenzene to acetophenone. The results indicated that the coupled cations have significant effect on the catalytic performance, and Co2Fe-LDH exhibited the highest catalytic activity. Synergistic effect between Co and Fe species has been obviously observed, and Fe species was able to significantly assist the catalytic oxidation over Co-containing LDHs. The high catalytic performance was proposed to be related to the high Co2+ content and its increased intrinsic activity, and electron transfer between Co and Fe species in the reaction. Under the optimized conditions, a 97.6 % conversion of ethylbenzene with a high 94.9 % selectivity to acetophenone could be obtained. According to the analysis of structure-activity relationship, hammett experiments and a series of control experiments, the possible reaction pathways for the aerobic oxidation of ethylbenzene over Co2Fe-LDH have been proposed.

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).

Numerical investigation of ethylbenzene dehydrogenation and nitrobenzene hydrogenation in a membrane reactor: Effect of operating conditions

This paper is a numerical study about ethylbenzene (EB) dehydrogenation and nitrobenzene (NB) hydrogenation in a membrane reactor. Both sides of the membrane reactor were filled with an appropriate catalyst. Effect of different parameters in the dehydrogenation side including inlet temperature, pressure, catalyst porosity, and initial ethylbenzene concentration was investigated on temperature distribution and ethylbenzene and nitrobenzene conversion in the membrane reactor. Generally, the results showed that an increase in all parameters except the catalyst porosity can improve ethylbenzene and nitrobenzene conversion. The temperature was firstly decreased in the dehydrogenation side as the reactions were endothermic but there was an increase in temperature after a shorter distance from the entrance because of transferring heat from hydrogenation side into dehydrogenation side. Change in pressure has a considerable effect on the hydrogen transferring from dehydrogenation side into hydrogenation side. The styrene yield was not improved by increasing the initial ethylbenzene concentration from 5 to 20 mol/s but it has a positive influence on the yields of benzene and toluene. It was possible to achieve 0.97 of ethylbenzene conversion at 950 K.

Hydrogenation of Ethylbenzene Over Ru/γ-Al₂O₃ Catalyst in Trickle-Bed Reactor.

The objective of this study is to evaluate the catalytic performance of pellet-type Ru/γ-Al₂O₃ as a catalyst during liquid-phase hydrogenation of the aromatic hydrocarbon. The Ru/γ-Al₂O₃ catalyst was prepared using a wet impregnation method. After adding a binder to Ru/γ-Al₂O₃, a pellet-type catalyst was obtained through an extrusion method. Nanoporous structures are well developed in the pellet-type Ru/γ-Al₂O₃ catalyst. The average pore sizes of the Ru/γ-Al₂O₃ catalysts were approximately 10 nm. The catalytic performance of the pellet-type Ru/γ-Al₂O₃ catalyst during ethylbenzene hydrogenation was evaluated in a trickle-bed reactor. When the ruthenium loading increased from 1 to 5 wt%, the number of active sites effective for the hydrogenation of ethylbenzene increased proportionally. In order to maximize the conversion of ethylbenzene to ethylcyclohexane, it was necessary to maintain a liquid phase hydrogenation reaction in the trickle bed reactor. In this regards, the reaction temperature should be lower than 90 °C. The conversion of ethylbenzene to ethylcyclohexane on the Ru(5 wt%)/γ-Al₂O₃ catalyst was highest, which is ascribed to the largest number of active sites of the catalyst.

EFFECT OF CARBON DIOXIDE ON OXIDATIVE ETHYLBENZENE DEHYDROGENATION IN THE PRESENCE OF ALUMINUM-CHROMIUM CATALYSTS

In order to create a more efficient process for the production of styrene from ethylbenzene by selective oxidation of the resulting hydrogen, model aluminum-chromium catalysts with different modifier (Cu) contents were prepared, and O2, CO2 and a mixture of CO2:air were used as an oxidant. It has been es-tablished that the process of obtaining of styrene from ethylbenzene on alumochromic catalysts is characterized by a high intensity. Alumochromic catalysts modified by Cu and promoted by 15 mass.% K2CO3 in the presence of carbon dioxide increase the conversion of ethylbenzene by 14%, and the selectivity of the formation of styrene by 10% as a result of the transferring dehydrogenation of compaction products to the products of oxidative compaction. The presence of oxygen in the oxidizing mixture CO2:air blocks the participation of carbon dioxide in the selective oxidation of hydrogen isolating at the dehydrogenation of ethylbenzene. It has been established that the most selective alumochromic catalysts in the oxidative dehydrogenation of ethylbenzene to styrene contain 1.5–2.5 mass.% of the modifying component (Cu)

Hydrotalcite-based CoxNiyAl1Ox mixed oxide as a highly efficient catalyst for selective ethylbenzene oxidation

• Co-Ni-Al layered double hydroxide was prepared via a simple coprecipitation method. • After calcination, the CoNiAlO mixed oxide with nanosheet structure was obtained. • The catalyst exhibits high efficiency in the selective oxidation of ethylbenzene. • It is attributed to the interactions between Co-Ni species and special structure. In this study, a series of Co–Ni–Al–layered double hydroxides (Co x Ni y Al 1 –LDHs) was successfully prepared via a simple co-precipitation method with Na 2 CO 3 and NaOH as the precipitants. After the calcination of the Co x Ni y Al 1 –LDH precursors, the Co–Ni–Al–O mixed oxides were formed and used as highly efficient catalysts in the selective oxidation of ethylbenzene to acetophenone. The Ni addition to CoAlO x can induce the formation of interactions between Co–Ni species and affect the dispersion of metal active centers, thereby greatly influencing the catalytic performance. The typical Co 2 Ni 1 Al 1 O x sample with a Co:Ni molar ratio of 2:1 exhibited the highest surface area (165 m 2 /g) and the best catalytic performance (80.0% ethylbenzene conversion and 88.9% acetophenone selectivity). The high catalytic efficiency was mainly attributed to the high-efficiency synergistic effect between the highly dispersed active center Co and the promoter Ni species. More importantly, the good recyclability and stability of the Co 2 Ni 1 Al 1 O x catalyst made it more competitive. A Co 2 Ni 1 Al 1 O x mixed oxide catalyst was obtained from the Co-Ni-Al layered double hydroxide precursor, which exhibited the high catalytic performance in the selective oxidation of ethylbenzene to acetophenone.

Transition Metal Salts of Carboxylated Multiwalled Carbon Nanotubes in Combination with N-hydroxyphthalimide as Catalytic Systems for Hydrocarbon Oxidation.

In this study, the transition metal (Co (II), Cu (II), and Mn (II)) salts of carboxylated carbon nanotubes were synthesized and characterized (the determined metal contents were in the range of 0.89–1.16%). The catalytic activity and the possibility for recovery and reuse of the obtained heterogeneous salts were then studied in the solvent-free oxidation of ethylbenzene with oxygen. The oxidation processes were carried out at 80 °C under atmospheric pressure in the presence of N-hydroxyphthalimide. The highest conversion of ethylbenzene, 27%, was obtained with a system consisting of the Cu (II) salt of the carboxylated carbon nanotubes, N-hydroxyphthalimide, and the azo initiator AIBN.

Promotional role of Ceria in N2O assisted selective oxidative dehydrogenation of ethylbenzene over Ce–Co2AlO4 spinel catalysts

The coupling of N2O decomposition with ethylbenzene (EB) dehydrogenation is a promising technique for greenhouse gas elimination and chemical production. The Ce–Co2AlO4 catalyst synthesized by the one-pot hydrothermal method was found to be effective for the oxidative dehydrogenation of ethylbenzene with N2O to form styrene (ST), and characterized by BET, XRD, TEM, TPR, TPD, and XPS techniques. Results showed that 0.10Ce–Co2AlO4 catalyst exhibited high EB conversion (61%) and good ST selectivity (80%), which was remarkable superior to the previously reported catalyst systems. The crystallite size of the catalyst showed a clear increasing trend with the increasing of Ce/Co molar ratio, resulting in an increased specific surface area. Among the factors determining catalytic performance, the larger number of oxygen vacancies and better reducibility of 0.10 Ce–Co2AlO4 catalyst significantly influenced the N2O adsorption and EB dehydrogenation processes. It was found that the good moderate acidic condition of 0.10Ce–Co2AlO4 catalyst was attributed to the masking of surface strong acid sites by Ce oxide, which weakened the ring-opening and dealkylation reactions during the dehydrogenation process, thus decreasing the accumulation of the deposited coke on the catalyst surface. The inter-transmission of oxygen species and N2O promotes the occupation of the oxygen vacancies and restores the redox cycle of the Co–Ce oxides, in accordance with the redox mechanism.

Synthesis and Characterization of Nano-Sized Pt/HZSM–5 Catalyst for Application in the Xylene Isomerization Process

The xylene isomerization is a well-established process in the aromatic-based petrochemical complex. This process aims to convert ethylbenzene (EB), meta- and ortho-xylene to para-xylene (PX). Active metal such as platinum (Pt) on the zeolite support is a commonly used catalyst for isomerization reactions. Different catalysts with different acidic strength of zeolite (Si/Al ratios = 32, 50, and 150) are synthesized in this study. The physical and chemical properties of the synthesized catalysts are characterized using X-ray diffraction (XRD), inductively coupled plasma (ICP), and Brunauer, Emmett, and Teller (BET) surface area analyses. Then, the effect of catalyst types and operating parameters such as temperature (370, 375, 380, and 385 °C), hydrogen partial pressure (2.4, 2.6, 2.8, and 3.0), and weight hourly space velocity (3.2, 3.4, 3.8 and 4.1 h−1) investigated on the xylene isomerization process. Indeed, the variation of EB conversion, xylene loss, and the ratio of PX produced to the PX in equilibrium condition (PXATE) by these influential factors is experimentally monitored in a laboratory-scale xylene isomerization reactor. Results show that the catalyst with a small Si/Al ratio of 32 has higher acidic strength and provides the best isomerization performance. Moreover, the temperatures of 375 °C, hydrogen partial pressure (H2/hydrocarbon) of 2.6, and weight hourly space velocity (WHSV) of 3.5 h−1 are the optimum operating conditions for the xylene isomerization process.