Catalytic Dehydrogenation Of Ethylbenzene Research Articles

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.

Dynamic simulation of manufacture of styrene by the catalytic dehydrogenation of ethyl benzene

Styrene is an important chemical compound derived from benzene. It is produced conventionally by the catalytic dehydrogenation of ethylbenzene in the presence of iron oxide catalyst. The reaction is reversible endothermic and is carried out in a series of adiabatic packed bed reactors. The present study deals with the dynamic simulation of the process of styrene manufacture using the Honeywell UniSim design suite. The control parameters of various controllers in the process have been derived using the auto-tune feature of the software. Various scenarios of servo problems were studied. The dynamic behaviour of the process parameters during various scenarios in the operating chemical plant is also studied. The results are very much useful for conducting the hazard analysis of the plant and thereby designing the trip systems of the plant.

CFD analysis of Pd-Ag membrane reactor performance during ethylbenzene dehydrogenation process

In this study, the catalytic dehydrogenation of ethylbenzene (EB) to styrene production was investigated in a tubular Pd-Ag membrane reactor (MR) in presence of a commercial iron oxide catalyst. To this purpose, a 2D-axisymmetric, isothermal model based on computational fluid dynamic (CFD) method is presented to investigate the Pd-Ag MR performance during EB dehydrogenation process for styrene and hydrogen production. The proposed CFD model provides the local information of velocity, pressure and component concentration for the driving force analysis. After investigation of mesh independency of CFD model, the validation of model results was carried out by experimental data and a good agreement between model results and experimental data was achieved. It was found that the efficient removal of hydrogen in the Pd-Ag MR could significantly increase the EB conversion. Moreover, using CFD simulation runs, effects of operating parameters such as reaction temperature, pressure and gas hour space velocity (GHSV) values on the Pd-Ag MR performance with two various flow patterns was evaluated in terms of EB conversion and COx-free hydrogen recovery. It can be concluded that the EB conversion realized in Pd-Ag MR with countercurrent flow is higher than the ones achieved for Pd-Ag MR with cocurrent flow and also for traditional reactor (TR) during EB dehydrogenation reaction, in all the studied cases. In particular, under the optimal reaction conditions, 40% enhancement in EB conversion can be obtained in the Pd-Ag MR with countercurrent flow with respect to TR.

Simulation of the styrene production process via catalytic dehydrogenation of ethylbenzene using CHEMCAD® process simulator

Background: Process simulation has been extensively used in recent years to design, evaluate or optimize processes, systems and specific operations of the chemical industry and its related disciplines. Currently, CHEMCAD® constitute one of the most used process simulators because of the great number of chemical and petrochemical processes that can be simulated.Method: The simulation of the production process of styrene via catalytic dehydrogenation of ethyl-benzene is carried out by using the process simulator CHEMCAD® version 5.2.0, in order to determine the composition and mass flow-rate of each process involved in the production, as well as the main operating parameters of the equipment used. Two sensitivity studies were carried out: firstly, the influence of the temperature and pressure values applied at the LLV Separator on the amounts of ethyl-benzene and styrene to be obtained by the intermediate and top currents of this equipment; secondly, the influence of the operating pressure of the Distillation Column No. 1 (benzene-toluene column) on the quantity of ethyl-benzene and styrene obtained at the bottom stream. The simulating software MATLAB® version 7.8.0 was used to process the results obtained.Results: Around 9234.436 kg/h of styrene is obtained in the last distillation column with 99.6% purity. Additionally, it was found that the water is the main impurity found on this stream, which represents 0.35% of the weight.Conclusions: The LLV Separator must operate at a low temperature (5 – 10 ºC) and at a relatively high pressure (10 bar), whereas the Distillation Column No. 1 must work at a pressure near atmospheric (1.0 bar), or preferably under vacuum conditions in order to obtain the highest yields of styrene and ethyl-benzene.

Evaluation of the Parameters and Conditions of Process in the Ethylbenzene Dehydrogenation with Application of Permselective Membranes to Enhance Styrene Yield.

Styrene is an important monomer in the manufacture of thermoplastic. Most of it is produced by the catalytic dehydrogenation of ethylbenzene. In this process that depends on reversible reactions, the yield is usually limited by the establishment of thermodynamic equilibrium in the reactor. The styrene yield can be increased by using a hybrid process, with reaction and separation simultaneously. It is proposed using permselective composite membrane to remove hydrogen and thus suppress the reverse and secondary reactions. This paper describes the simulation of a dehydrogenation process carried out in a tubular fixed-bed reactor wrapped in a permselective composite membrane. A mathematical model was developed, incorporating the various mass transport mechanisms found in each of the membrane layers and in the catalytic fixed bed. The effects of the reactor feed conditions (temperature, steam-to-oil ratio, and the weight hourly space velocity), the fixed-bed geometry (length, diameter, and volume), and the membrane geometry (thickness of the layers) on the styrene yield were analyzed. These variables were used to determine experimental conditions that favour the production of styrene. The simulation showed that an increase of 40.98% in the styrene yield, compared to a conventional fixed-bed process, could be obtained by wrapping the reactor in a permselective composite membrane.

A new perspective on catalytic dehydrogenation of ethylbenzene: the influence of side-reactions on catalytic performance

The dehydrogenation of ethylbenzene to styrene over CrOx/Al2O3 proceeds via a partially oxidative mechanism due to in situ formation of CO2. Coke formation also plays a key role in dictating catalytic performance.

Optimization of Styrene Reactor Using Tabu Search and Genetic Algorithm Methods

This paper deals with multi-objective optimization of styrene reactor using Tabu search (TS) and genetic algorithm (GA) methods. Styrene is produced commercially by catalytic dehydrogenation of ethyl benzene. As styrene is an important monomer, the capacity of the plant is usually very high, as a result the investment cost is also very high, and even a small enhancement in the plant operation can generate major income. The adiabatic reactor using the pseudo homogeneous model was considered in this study for maximizing the styrene conversion and selectivity. A computer program was written to simulate an adiabatic reactor in order to evaluate the possibility of optimizing the process in simulation environment. The simulation results were compared with the experimental data. This comparison indicated that the value of overall mean squarer of errors for conversion of the compounds was 7.09E-05 and overall means relative error of them was 2.18 percent. In order to optimize the performance of the reactors, conversion of styrene was adopted as the objective function. Six decision variables, namely, ethyl benzene feed temperature at the entrance of each bed, pressure, the ratio of steam to ethyl benzene and initial ethyl benzene flow rate were used for the optimization. The results of GA optimization showed final conversion of styrene increased from an initial value of 0.710 to 0.75 after 100 generation of population. Applying Tabu algorithm optimization, the value rose from 0.725 to 0.813 after generation of 100 neighborhoods. The results revealed that the CPU time needed to optimize the reactor for TS was shorter than that of GA method. In addition, using the same iteration numbers for both methods, the optimum value of styrene conversion was greater when TS method was applied.

Mesoporous MAl 2O 4 (M = Cu, Ni, Fe or Mg) spinels: Characterisation and application in the catalytic dehydrogenation of ethylbenzene in the presence of CO 2

The catalytic properties of nanostructured MAl 2O 4 (M = Cu, Ni, Fe or Mg) were investigated in the dehydrogenation of ethylbenzene with CO 2. The catalysts were characterised by XRD, Raman spectroscopy, textural properties, acidity (TPD-NH 3) and basicity (CO 2-TPD) measurements, SEM and TEM analyses and TPR techniques. XRD revealed the spinel structure of MAl 2O 4, except for the NiO, CuO, Fe 2O 3 and MgO phases. All solids exhibited the nanostructured features of the SBA-15 template, including high values of textural properties and morphologies characteristic of the mesoporous silica. The acidic strength follows the electronegativity trends of the cations present on the spinel aluminates: CuAl > NiAl > FeAl and MgAl, which is the inverse order of the basicities. The selectivities in the dehydrogenation of ethylbenzene with CO 2 showed that styrene was the predominant product for all catalysts except for those based on Ni, which was highly selective for the production of toluene. The FeAl 2O 4 catalyst provided the best catalytic performance among the solids studied due to the continuous oxidation of Fe 3+ sites by the CO 2 from the reaction. This solid has the additional advantage of being stable over the timescale of the reaction, as compared to the traditional Fe-based catalysts, due to its nanostructured features.

Behaviors of V-doped Titanium Mixed Oxides in the Catalytic Dehydrogenation of Ethylbenzene

By an acid-catalyzed sol–gel method the V-doped titanium oxides (VxDTOs, x mol% of V/(V + Ti) molar ratio) were prepared and systematically characterized by the techniques of XRD, TEM, H2-TPR, XPS and TGA, indicating that most of the vanadium in the catalyst was highly dispersed on the surface of and in the bulk phase of TiO2. The effect of V5+ doping level (1–9 mol% V5+) on the surface of TiO2 and VxDTOs catalytic performance was analyzed. From the catalytic activity evaluation of VxDTOs in the dehydrogenation of ethylbenzene to styrene in the presence of CO2 (CO2-EBDH) at 450 °C, V6DTOs catalyst had the highest activity. Its higher activity in CO2 than in N2 clearly shows that CO2 markedly enhanced the dehydrogenation of ethylbenzene. The activity of V6DTOs catalyst could almost be resumed after regeneration by air while partly resumed after regeneration by CO2.

Studies of catalytic activity and coke deactivation of spinel oxides during ethylbenzene dehydrogenation

Catalytic dehydrogenation of ethylbenzene with CO 2 to produce styrene was carried out on MAl 2O 4 (where M = Cu 2+, Ni 2+, or both), and also with pure NiO and CuO catalysts. The synthesized materials were characterized by various physico-chemical techniques and catalytic activity, coke deactivation, and recycling of spent catalysts were studied. The NiAl 2O 4 phase showed the highest activity under moderate conditions (activity = 160 × 10 −3 mol g −1 h −1; selectivity to styrene = 90.7%). Pure NiO and CuO were virtually inactive in the reaction due to the easy reduction of the phases in these oxides. NiAl 2O 4, an active phase for the reaction, was cooperatively associated with Cu in a highly stable ternary system (Cu-Ni-Al). However, this association did not result in high conversion or selectivity. Analyses of the coked catalysts revealed the presence of carbon on the solid surface that was in the form of graphite and polyaromatics. Deactivation studies on NiAl 2O 4 proved that Ni 2+ sites were covered with a moderate amount of crystalline graphite that grew progressively and was subsequently eliminated by using higher CO 2/EB ratios. These results suggest that a reverse water shift reaction may be occurring when this solid is used. On the other hand, polyaromatic carbons were not eliminated and were the leading cause of the catalyst deactivation, rather than the physical degradation (reduction) of the solid. Recycling studies have demonstrated the high tendency of NiAl 2O 4 to regain the oxidation state of nickel, and thus, the styrene selectivity was maintained for over 40 h. The conditions leading to the highest conversion were a CO 2/EB ratio of 30 and a T = 550 °C at ambient pressure. Under these conditions, activities were comparable to those of Fe-K commercial catalysts for dehydrogenation, leading over the steam.

High Performance of Fe–K Oxide Catalysts for Dehydrogenation of Ethylbenzene to Styrene with an aid of ppm-order Pd

Styrene is manufactured industrially through catalytic dehydrogenation of ethylbenzene on Fe–K oxide-based catalysts. It was invented by Sud-Chemie Group that the activity of the industrial ethylbenzene dehydrogenation catalysts (Styromax) based on the oxides of Fe and K is highly promoted by the addition of small amount (hundreds ppm-order) of precious metals such as Pd. The present work is intended to elucidate the role of Pd on the Fe–K catalyst empirically by use of a periodical pulse technique from a mechanistic point of view. The oxidative dehydrogenation was faster than the simple dehydrogenation, and it proceeded by consuming the surface lattice oxygen in the catalyst. The lattice oxygen was subsequently supplied from steam. Palladium added to the Fe–K oxide catalysts was found to enhance the rate of regeneration (supplying) of the lattice oxygen, although it hardly changed the rate of dehydrogenation of ethylbenzene or consumption of surface lattice O2− anions. This study demonstrated that steam works not only as a diluent but also as a reactant to form hydrogen and lattice oxygen.

Dehydrogenation of Ethylbenzene to Styrene with Carbon Dioxide Over ZrO2-based Composite Oxide Catalysts

We have been exploring various new catalyst systems for the utilization of carbon dioxide as a soft oxidant in the catalytic dehydrogenation of ethylbenzene (EB) to styrene. The utilization of CO2 as a soft oxidant for the commercially important catalytic dehydrogenation of EB to styrene has received enormous attention recently due to its several attractive features. This review summarizes the results of our most recent findings on zirconia-based composite oxide catalyst systems exploited for this reaction. Under this systematic and comprehensive investigation various zirconia-based composite oxide catalysts namely, TiO2-ZrO2, MnO2-ZrO2, CeO2-ZrO2, K2O/TiO2-ZrO2, B2O3/TiO2-ZrO2 and CeO2-ZrO2/SBA-15 have been synthesized, characterized by various techniques and evaluated for the title reaction. Most of these composite oxide catalysts were found to exhibit very interesting physicochemical characteristics and exceptionally better catalytic properties for this reaction. As revealed by characterization results, a large number of acid–base sites with moderate strength are essential for a high conversion and product selectivity of this reaction with CO2 as the soft oxidant.

An Overview on the Dehydrogenation of Alkylbenzenes with Carbon Dioxide over Supported Vanadium–Antimony Oxide Catalysts

Utilization of carbon dioxide as a soft oxidant for the catalytic dehydrogenation of ethylbenzene (CO2-EBDH) has been recently attempted to explore a new technology for producing styrene selectively. This article summarizes the results of our recent attempts to develop effective catalyst systems for the CO2-EBDH on the basis of alumina-supported vanadium oxide catalysts. Its initial activity and on-stream stability were essentially improved by the introduction of antimony oxide as a promoter into the alumina-supported catalyst. Insertion of zirconium oxide into alumina support substantially increased the catalytic activity. Modification of alumina with magnesium oxide yielded an increase of catalyst stability of alumina-supported V–Sb oxide due to the coking suppression. Carbon dioxide has been confirmed to play a beneficial role of selective oxidant in improving the catalytic performance through the oxidative pathway, avoiding excessive reduction and maintaining desirable oxidation state of vanadium ion (V5+). The positive effect of carbon dioxide in dehydrogenation reactions of several alkylbenzenes such as 4-diethylbenzene, 4-ethyltoluene, and iso- and n-propylbenzenes was also observed. Along with the easier redox cycle between fully oxidized and partially reduced vanadium species, the optimal surface acidity of the catalyst is also responsible for achieving high activity and catalyst stability. It is highlighted that supra-equilibrium EBDH conversions were obtained over alumina-supported V–Sb oxide catalyst in CO2-EBDH as compared with those in steam-EBDH in the absence of carbon dioxide.

Catalytic Dehydrogenation of Ethylbenzene in Helium and Reductive Dealkylation in Hydrogen on Nb, Mo, Ta, W, and Re Halide Clusters

Halide clusters of [(Nb6Cl12)Cl2(H2O)4]⋅4H2O and (H3O)2[(M6Cl8)Cl6]⋅ 6H2O (M=Mo, W), which have an octahedral metal framework, and Re3Cl9, which has a triangular metal framework, developed catalytic activity for the dehydrogenation of ethylbenzene selectively to yield styrene when the halide clusters were treated in a stream of helium at 450°C. In the case of the Mo cluster, this catalytic activity appeared at 300°C. The activity increased with increasing temperature. Above 400°C, the catalytic activity decreased with time, and the selectivity for benzene increased noticeably. The reduction in the activity was caused by the formation of coke attributable to ethylene produced as a by-product. When the Nb and Ta clusters of the same structure were treated in a stream of hydrogen in the same way, no catalytic reaction proceeded. However, the Mo and W clusters in a stream of hydrogen catalyzed reductive dealkylation of ethylbenzene selectively yielding toluene and benzene. In the case of the Mo cluster, the catalytic activity appeared at 400°C, and increased with increasing temperature. The activity did not decrease with time even at high temperatures. The Re cluster, which was reduced to the metal by the treatment in hydrogen, catalyzed ring-opening degradation to yield gaseous hydrocarbons.

Catalytic dehydrogenation of ethylbenzene with carbon dioxide: promotional effect of antimony in supported vanadium–antimony oxide catalyst

Alumina-supported vanadium oxide, VO x /Al 2O 3, and binary vanadium–antimony oxides, VSbO x /Al 2O 3, have been tested in the ethylbenzene dehydrogenation with carbon dioxide and characterized by S BET, X-ray diffraction, X-ray photoelectron spectroscopy, hydrogen temperature-programmed reduction and CO 2 pulse methods. VSbO x /Al 2O 3 exhibited enhanced catalytic activity and especially on-stream stability compared to VO x /Al 2O 3 catalyst. Incorporation of antimony into VO x /Al 2O 3 increased dispersion of active VO x species, enhanced redox properties of the systems and formed a new mixed vanadium–antimony oxide phase in the most catalytically efficient V 0.43Sb 0.57O x /Al 2O 3 system.

Coke Formation and Gasification in the Catalytic Dehydrogenation of Ethylbenzene

A detailed kinetic model for coke formation and gasification on an industrial potassium-promoted iron oxide catalyst during ethylbenzene dehydrogenation is developed. The kinetic parameters are estimated from a set of transient experiments in an electrobalance reactor, operated under differential conditions. The gasification was found to proceed through an edge recession mechanism. The coke formation occurs as a sequence of precursor formation followed by growth. The coupling of this coke formation/gasification model with a detailed model for the main and the side reactions allows an accurate prediction of the amount of CO2 formed in a multibed pilot-plant unit. The model is used to evaluate some recently proposed modifications to the process operation.

Ação promotora do berílio em catalisadores da síntese do estireno

The catalytic dehydrogenation of ethylbenzene in presence of steam is the main commercial route to produce styrene. The industrial catalysts are potassium- and chromia-doped hematite which show low surface areas leading to bad performance and short life. In order to develop catalysts with high areas, the effect of beryllium on the textural properties and on the catalytic performance of this iron oxide was studied. The influence of the amount of the dopant, the starting material and the calcination temperature were also studied. In sample preparations, iron and beryllium salts (nitrate or sulfate) were hydrolyzed with ammonia and then calcinated. The experiments followed a factorial design with two variables in two levels (Fe/Be= 3 and 7; calcination temperature= 500 and 700oC). Solids without any dopant were also prepared. Samples were characterized by elemental analysis, infrared spectroscopy, surface area and porosity measurements, X-ray diffraction, DSC and TG. The catalysts were tested in a microreactor at 524oC and 1 atm, by using a mole ratio of steam/ ethylbenzene=10. The selectivity was measured by monitoring styrene, benzene and toluene formation. It was found that the effect of beryllium on the characteristics of hematite and on its catalytic performance depends on the starting material and on the amount of dopant. Surface areas increased due to the dopant as well as the nature of the precursor; samples produced by beryllium sulfate showed higher areas. Beryllium-doped solids showed a higher catalytic activity when compared to pure hematite, but no significant influence of the anion of starting material was noted. It can be concluded that beryllium acts as both textural and structural promoter. Samples with Fe/Be= 3, heated at 500oC, lead to the highest conversion and were the most selective. However, catalysts prepared from beryllium sulfate are the most promising to ethylbenzene dehydrogenation due to their high surface area which could lead to a longer life.

Catalytic dehydrogenation of ethylbenzene and tetrahydrofuran by a dihydrido iridium P–C–P pincer complex

The P–C–P pincer complex, [IrH 2 {C 6 H 3 (CH 2 PBu t 2 )-2,6}] catalyses the transfer dehydrogenation of the donor-bearing substrates, ethylbenzene and tetrahydrofuran at temperatures as low as 150 °C.

Mathematical analysis on catalytic dehydrogenation of ethylbenzene using ceramic membranes

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTMathematical analysis on catalytic dehydrogenation of ethylbenzene using ceramic membranesJeffrey C. S. Wu and Paul K. T. LiuCite this: Ind. Eng. Chem. Res. 1992, 31, 1, 322–327Publication Date (Print):January 1, 1992Publication History Published online1 May 2002Published inissue 1 January 1992https://doi.org/10.1021/ie00001a043RIGHTS & PERMISSIONSArticle Views315Altmetric-Citations52LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (2 MB) Get e-Alerts Get e-Alerts

Modelling the dynamics of regenerative catalytic reactors

Regenerative catalytic reactors (RCRs) are proposed as novel catalytic systems especially for reversible reactions. At least two reactor vessels are required for continuous operation, and each reactor operates intermittently and transiently. When one reactor is operating, the temperature level in the other one is being regenerated. This RCR system is mathematically, modelled by a two-phase heterogeneous representation, and a numerical solution is proposed which is stable and convergent. The transient nature of an RCR system for the catalytic dehydrogenation of ethylbenzene to styrene is used to illustrate the operating characteristics. This system is shown to produce a higher conversion of ethylbenzene to styrene than a steady-state adiabatic configuration using the same amount of catalyst.