Ethylbenzene Conversion Research Articles

Green oxidation of alkylaromatics using molecular oxygen over mesoporous manganese silicate catalysts.

A very green catalytic method has been introduced for the synthesis of alkylaromatic ketones by solvent-free benzylic oxidation of alkylaromatics with molecular oxygen (O2) over hexagonally mesostructured MnSBA-15 catalysts synthesized with a variety of manganese (Mn) contents using a pH-adjusting direct hydrothermal (pH-aDH) method. For example, the solvent-free oxidation of ethylbenzene (EB) over different mesoporous MnSBA-15 catalysts and uniform pore sized MnMCM-41(31) prepared by an alkaline hydrothermal method has been systematically evaluated. Washed MnSBA-15(4) (W-MnSBA-15(4)) or green mesoporous MnSBA-15(4) obtained after the removal of the non-framework octahedral Mn2O3 species deposited on the active surface of MnSBA-15(4) using a promising chemical treatment method is used for this reaction to evaluate its catalytic activity. Meanwhile the recyclability and hot-filtration experiments for this reaction have been also studied. The catalytic activities obtained from the above catalytic results prove that the W-MnSBA-15(4) has higher EB conversion and AP[double bond, length as m-dash]O selectivity than the other mesoporous catalysts used in this reaction. Therefore, in order to find the optimal reaction parameters for this reaction, various reaction parameters with W-MnSBA-15(4) have been thoroughly evaluated. Using W-MnSBA-15(4), the catalytic results obtained with different oxidants used in this reaction have also been discussed clearly. The catalytic results of solvent-free benzylic oxidations with W-MnSBA-15(4) conducted with different alkylaromatic molecules have been obviously discussed. All the mesoporous catalysts used in this reaction have been characterized using several instrumental techniques to confirm them as the standard mesoporous catalysts. The plausible reaction mechanism for the solvent-free oxidation of EB has been successfully reported based on the characterization results of the catalyst and catalytic results. The ESR and UV-vis DRS results of the W-MnSBA-15 catalyst used in these reactions corroborate that the disordered octahedral divalent (Mn2+) and tetrahedral trivalent (Mn3+)-species have been successfully incorporated on the silica surface of the catalysts. Based on the catalytic results, it is noteworthy to observe that mesoporous W-MnSBA-15(4) is a highly active, green and promising heterogeneous catalyst for the selective synthesis of alkylaromatic ketones, since the catalyst produces the best catalytic activity among the other mesoporous Mn silicate catalysts.

Pyrolysis chars and physically activated carbons prepared from buckwheat husks for catalytic purification of syngas

This paper investigates the impact of the oxidizing agent used in the physical activation of pyrolysis chars on activated carbons (AC), and their efficiency in tar cracking. The materials are produced from buckwheat husk, which is a French local biomass. Slow pyrolysis was chosen to favor the production of raw chars. Activated chars were then prepared by physical activation under steam or CO2. The materials produced were physically and chemically characterized before being implemented in a fixed bed. The efficiency of materials in removing tar from syngas was studied, and ethylbenzene (EB) was chosen as the tar surrogate. The purification efficiency of the chars and AC was deduced from the EB conversion profiles in comparison with thermal cracking. The nature of the oxidizing agent impacted the porosity and mineral composition of the AC produced: CO2 activation produced ACs with more carbon and less ash content. This is because the reduction of carbon with carbon dioxide presents a kinetic between 2 and 5 times slower than that conducted in the presence of steam. CO2 activation also resulted in a higher relative microporosity (89%) than steam activation (61%), which itself gives a higher surface area. Pyrolysis char did not generate any interest for EB catalytic cracking, whereas ACs demonstrated higher performances. This is due to their higher level of porosity and higher ash content. BH–H2O, which presents higher porosity, produced a better catalytic effect and was more resistant to deactivation.

Hydrophobic Modification of Microenvironment of Highly Dispersed Co3O4 Nanoparticles for the Catalytic Selective Oxidation of Ethylbenzene

AbstractMicroenvironments in enzymes play crucial roles in controlling the activities of active centers. Here, hexagonal mesoporous silicas (HMS) with hydrophobic microenvironment was used to mimic the enzymes on the hydrocarbon oxidation with cobalt oxides incorporated as active sites. The variation of the structure and surface properties of the materials with phenyl group incorporation and the state of the supported cobalt oxides were carefully studied. It showed that cobalt oxides presented as Co3O4 distributed evenly among the support, and the catalytic microenvironment was modified by the neighboring phenyl groups to be hydrophobic. This novel catalyst showed enhancement in the adsorption of ethylbenzene and in turn promoted the catalytic conversion than the hydrophilic one. 55.1 % conversion of ethylbenzene and 86.1 % selectivity for acetophenone could be obtained at 393 K for 6 h under 1.0 MPa of O2 with free solvent. Hydrophobic microenvironment of pore surface was considered as an important factor for the better catalytic activity.

Alumina-boron catalysts for oxidative dehydrogenation of ethylbenzene to styrene: Influence of alumina-boron composition and method of preparation on catalysts properties

Different mole ratio Al-B catalysts (Al-10B to Al-35B) were synthesized by using sol-gel (SG) method. Ethyl benzene (EB) dehydrogenation in the presence of oxygen and water steam was carried out on these catalysts at 450–500 °C with EB contact time of 0.54 gcat.s.cm–3. Acidity of Al-B catalysts was estimated by using NH3-TPD-mass spectral analysis studies. SEM-mapping images revealed fine distribution of boron up to 15% of its loading in alumina (Al-15B), whereas, boron aggregation was observed in higher boron content (Al-25B and Al-35B) catalysts. Essentially, acid sites of very weak strength (Tmax ≤ 125 °C) were observed for Al and Al-10B catalysts and resulted in low EB conversion and styrene yield. On the other hand, acid sites of weak strength (Tmax ≤ 180 °C) were observed for Al-25B and Al-35B catalysts and resulted in high EB conversion. However, greater styrene yield (43.2%) with reasonable EB conversion (46%) was obtained on acid sites of weak moderate strength in Al-15B catalyst. Further, Al-15B catalyst was synthesized by using co-precipitation (COP) and impregnation (IMP) methods. Acid sites related to NOx formation during the NH3-TPD-mass analysis on IMP and COP catalyst essentially improved the EB conversion to 66% and 63% respectively at 500 °C. However, these acid sites were diminished in Al-B SG catalyst and resulted in 50% of EB conversion at 500 °C. At 50% of EB conversion level, styrene selectivity of 73%, 82.5% and 84% were observed on Al-B IMP, Al-B COP and Al-SG catalysts, respectively. Hence, different method of preparation of Al-B catalyst generated acid sites of different strength and density and thereby influenced the styrene formation.

A Study of Platinum Catalysts Based on Ordered Al–МСМ-41 Aluminosilicate and Natural Halloysite Nanotubes in Xylene Isomerization

Hierarchical composite materials based on ordered aluminosilicates of the Al–MCM-41 type and halloysite nanotubes (HNTs) with different Al–MCM-41/halloysite weight ratios have been synthesized and studied as components of supports of platinum catalysts for the isomerization of the C8 aromatic fraction of reforming. At each synthesis stage, the materials have been characterized by transmission electron microscopy (TEM), low-temperature nitrogen adsorption, X-ray fluorescence analysis, X-ray diffraction (XRD) analysis, and temperature-programmed desorption of ammonia (NH3-TPD). Catalyst systems with an Al–MCM-41/HNT weight ratio of 90 : 10 wt % have shown the highest efficiency in xylene isomerization providing a higher conversion of ethylbenzene and m-xylene than the conversion provided by the HNT-based catalyst. It has been found that the synthesized catalysts exhibit a higher selectivity for the target product of the process—p-xylene—than the selectivity of a commercial counterpart in a temperature range of 360–440°C. The maximum p-xylene selectivity (70%) has been achieved in the presence of a Pt/Al–MCM-41/HNT(90 : 10)/Al2O3 catalyst at 360°C.

On the catalytic role of superficial VOx species and coke deposited on mesoporous MgO replica in oxidative dehydrogenation of ethylbenzene

Mesoporous MgO was synthesized by the nanoreplication method using CMK-3 carbon as a hard template and magnesium nitrate as a metal oxide precursor. The produced support was modified with different amounts of ammonium metavanadate solution. Various distributions of V-containing species on the MgO surface were found by XRD, low-temperature adsorption of N2, TEM, XPS and UV–vis-DR spectroscopy. At low V loadings isolated VO4 dominated. Increasing V content resulted in clustering of VO4 species and the formation of Mg3V2O8 crystallites. As found in temperature-programmed reduction (H2-TPR), the latter phase was clearly harder in reduction by H2 compared to highly dispersed VO4 forms. The developed materials appeared to be very active catalysts of oxidative dehydrogenation of ethylbenzene (ODH). The optimal catalytic performance was observed for the sample containing 10 wt% of vanadium. The initial ethylbenzene conversion of 63.6% at selectivity to styrene of 86.9% was achieved at temperature as low as 500 °C. A notable influence of carbonaceous deposit formed during the ODH reaction on the catalytic activity was discussed, including presentation of both coexisting superficial reaction mechanisms. A reasonable regeneration procedure to recover lost activity was developed.

Aliphatic amines modified CoO nanoparticles for catalytic oxidation of aromatic hydrocarbon with molecular oxygen

The surface modification of metal oxides using organic modifiers is a potential strategy for enhancing their catalytic performances. In this study, a hydrophobic surface amine-modified CoO catalyst with a water contact angle of 143° was fabricated. The catalyst was characterized by XRD, TGA, FT-IR, HR-TEM, and XPS. The results showed that the fabricated catalyst performed better than the hydrophilic commercial CoO nanoparticle in the process of aromatic hydrocarbon oxidation. After the amines modification, commercial CoO also became hydrophobic and improved conversion of ethylbenzene was achieved. The surface modification of CoO with amines induced the hydrophobicity property, which could serve as a reference for the design of other hydrophobic catalysts. The amines-modified CoO nanoparticles exhibited hydrophobic properties with a water contact angle of 143°, which was accompanied by better performance in the hydrocarbon oxidation process compared to that of the hydrophilic commercial CoO nanoparticles.

Advantage of Co Embedded γ-Al2O3 Catalysts Over MgO and SiO2 Solid Oxides in the Selective Production of Styrene Monomer

A series of cobalt oxide (Co3O4) loaded (5–20wt%) γ-Al2O3, MgO and SiO2 supported catalysts were prepared by wetness-impregnation method and tested for oxidative dehydrogenation (ODH) of ethylbenzene (EB) in vapor phase atmospheric pressure conditions. Among Co oxide doped catalysts, Co3O4/γ-Al2O3 (CA) has afforded a superior catalytic activity in view of desirable EB conversion and styrene (ST) yields. Thus unusual catalytic properties of 15CA catalyst were supposed to be due to adequate acidic-basic nature, thermal stability and synergistic effect of Co-Al species along with uniform distribution of active Co oxide ions. Moreover, dramatic catalytic activity of Co3O4 incorporated γ-Al2O3 catalyst can be explained on the basis of beneficial CO2 conversion subsequently production of better CO yields during the online gas analysis. All calcined catalysts have been characterized by different sophisticated techniques to elucidate the surface metal composition and influence of Co3O4 oxide species on catalytic activity presentation during the oxidative dehydrogenation of EB reaction.

Solvent-free oxidation of ethylbenzene over LDH-hosted Co(II) Schiff base of 2-hydroxy-1-naphthaldehyde and 4-amino benzoic acid

Co(II) Schiff base complexes derived by condensation of 4-amino benzoic and 2-hydroxy-1-naphthaldehyde was immobilized into layered double hydroxide, {LDH-[NAPABA-Co(II)]} and characterized by various techniques namely ICP-AES, SEM, TEM, EDX, XRD, FTIR, BET surface area, EPR, TGA, and DRUV–vis. spectroscopy. The structures of the Co(II) Schiff base complex are optimized by DFT calculations. The catalytic activity of the heterogenized Co(II) Schiff base complex for the oxidation of ethylbenzene using tert-butylhydroperoxide is studied under a solvent-free condition. Ethylbenzene upon oxidation gave benzaldehyde, acetophenone, and benzoic acid with 67.4% conversion of ethylbenzene and 99.57% selectivity of acetophenone. The catalyst is recyclable up to six cycles without notable loss of their activity.

Two-step hydrothermally synthesized Ce1-xZrxO2 for oxidative dehydrogenation of ethylbenzene with carbon dioxide

Ceria, zirconia, Ce0.9Zr0.1O2, Ce0.75Zr0.25O2, and Ce0.5Zr0.5O2 samples were synthesized via the two-step hydrothermal method by using Ce(NO3)3·6H2O and Zr(NO3)4·5H2O as the precursors, respectively. The oxides were applied as catalysts for the dehydrogenation of ethylbenzene by using carbon dioxide as a soft oxidant (CO2-ODEB) at 550 °C and 0.1 MPa. Reaction results indicate that ceria was the most active catalyst while the zirconia with a cubic structure was inactive for CO2-ODEB. In the cases of the oxides by inserting Zr into CeO2, the activity indexed by either the initial ethylbenzene (EB) conversion or the calculated turnover frequency (TOF) at a time on stream of 1 h was changed in the sequence of Ce0.9Zr0.1O2 >> Ce0.75Zr0.25O2 > Ce0.5Zr0.5O2 while the decreasing pattern of the stability was observed in the order of Ce0.5Zr0.5O2 ≈ Ce0.75Zr0.25O2 >> Ce0.9Zr0.1O2. As revealed from the characterization results of XRD and Raman, the pure cubic solid solution of Ce1-xZrxO2 without any phase separations was obtained irrespective of the compositions. By correlating the characterization results, the activity of Ce1-xZrxO2 for CO2-ODEB was determined by the amount of the Ce3+ oxidized by CO2 and the rate of Ce3+/Ce4+ redox cycles. Moreover, both the coking rate and the promoting effect of the deposited coke on CO2-ODEB were responsible for the stability of Ce1-xZrxO2.

Microwave Irradiation Synthesized Cobalt-Loaded Nitrogen-Doped Active Carbon as an Efficient Catalyst for Selective Oxidation of Ethylbenzene

Microwave irradiation technology was used to dope nitrogen on the active carbon using dicyanodiamide as nitrogen source. The obtained nitrogen-doped active carbon was then modified by an ion impregnation method to load cobalt ions. The as-prepared cobalt-loaded nitrogen-doped active carbon (Co–N–AC) was characterized by techniques such as XRD, SEM, XPS, EA and AAS and the catalytic performance was evaluated via the selective oxidation of ethylbenzene under solvent-free condition using molecular oxygen as oxygen source. The results showed that 23.2 mol% conversion of ethylbenzene and 95.7% selectivity to acetophenone was obtained over 3%Co–N–AC, in which the excellent catalytic performance of the catalysts may be attributed to the stable doped N, the highly dispersed Co on the surface of AC and the structure of Co-N bond.

Comparison of single-bed oxidative dehydrogenation of ethylbenzene with double-bed using CO2

The present study highlights the catalytic performance of 5 wt% Fe2O3 supported on sodium chromosilicate (5F/NCS) in a single-bed reactor for dehydrogenation of ethylbenzene with CO2 and compares it with the catalytic performance of two subsequent catalysts (5F/NCS + industrial oxidation catalyst) in a double-bed reactor. The support of the target nanocomposite catalyst was obtained by hydrothermal treatment and subsequently was loaded with a medium amount of 5 wt% γ-Fe2O3. Structural and textural characterizations of the catalysts were performed by means of X-ray diffraction, scanning electron microscopy, transmission electron microscopy, N2 physical adsorption analysis, and Fourier-transform infrared spectroscopy. The catalytic tests revealed that 5F/NCS in the single-bed reactor had a high ethylbenzene conversion (> 54%) and a low styrene selectivity (> 70%). In comparison with this observation, in the double-bed reactor with the presence of oxidation catalysts, styrene selectivity increased significantly (> 91%), however; ethylbenzene conversion indicated a minor decrease (> 50%). The high styrene selectivity (> 91%) and styrene yield (> 46%) in the double-bed reactor were ascribed to the coupling reaction of ethylbenzene dehydrogenation and RWGS as well as the synergistic effect of Pt–Sn in the structure of oxidation catalyst.

Evaluation of Major Product Distribution Using Experimental‐Theoretical Comparative Studies on Toluene and Ethylbenzene Ethylation over Catalysts Zeolite MCM‐22 and Modified MCM‐22

AbstractThe activity of zeolite MCM‐22 and modified MCM‐22 catalyst were tested in the vapor phase alkylation of toluene and ethylbenzene by ethanol to investigate the influence of thermodynamic parameters, reaction temperature, and the molar ratio of toluene and ethylbenzene to ethanol. The reactions were evaluated with experimental and theoretical approaches. The catalysts were characterized by XRD, FE‐SEM, TGA, N2‐adsorption, and NH3 & Py‐TPD analyses. The superior catalytic performance of modified MCM‐22 was observed in ethylation of ethylbenzene and ethylation of toluene. The catalytic performance indicates that zeolite MCM‐22 retained shape selectivity resulting into para‐selectivity, while modified MCM‐22 possessed more mesopores and increased accessibility to the acid sites thereby increasing conversion of ethylbenzene.

Nanodiamonds @ N, P co-modified mesoporous carbon supported on macroscopic SiC foam for oxidative dehydrogenation of ethylbenzene

A robust monolith catalyst has been fabricated involving the combination of nanodiamonds (NDs) and mesoporous carbon modified by nitrogen and phosphorus (ND@NMC-xP, x = amount of ammonium biphosphate) on a β-SiC foam. The ND@NMC-0.02 P/SiC monolith catalyst with 0.2 at.% of P elements exhibits an excellent catalytic performance for oxidative dehydrogenation of ethylbenzene (EB), delivering 90.2% selectivity to styrene (ST) up to 32.6% conversion. The specific conversion rate of monolith catalyst based on the unit weight of NDs and mesoporous carbons (25.3 mmol gact. phase−1 h−1) is 3-fold higher than that of unsupported NDs. The role of nitrogen is believed to enhance the density of active sites and thus offering a high EB conversion, whereas the addition of phosphorus inhibits deep oxidation of EB to carbon oxides and therefore for a high selectivity to ST. The monolith catalyst not only contributes a high utilization efficiency of NDs but also mitigates the high pressure drop across the catalytic bed, which is potentially suitable for a real industrial process.

Unique influence of rare earth (Pr, Nd, and Er) oxide surface acidic texture over CeO2/γ-Al2O3 catalysts for selective production of styrene using CO2 flow

Variety of rare earth oxide-doped CeO2/γ-Al2O3 catalysts were prepared by a wet impregnation method and evaluated for oxidative dehydrogenation of ethylbenzene (EB) using CO2 as soft oxidant in vapor-phase atmospheric-pressure conditions. Amongst the bare CeO2/γ-Al2O3 catalysts, 15 wt% CeO2/γ-Al2O3 exhibited excellent catalytic activity with noteworthy EB conversion and styrene selectivity. After incorporation of 3 wt% Er2O3, Pr2O3, or Nd2O3 oxide onto the 15 wt% CeO2/γ-Al2O3 (15CA) catalyst, unusual catalytic properties were observed in terms of formation of active solid-solution species. The greater fraction of CO2 molecule activation and dissociation phenomenon on the surface rare earth-doped CeO2/γ-Al2O3 catalysts compared with the bare CeO2/γ-Al2O3 catalyst were investigated. Among the rare earth-doped catalysts, 3ErCA showed superior mobile oxygen storage capacity and high CO2 utilization ability, along with optimal surface acidic properties compared with the rare earth solid-solution properties of (CexRE1−xO2−δ) Pr2O3 and Nd2O3 species. Moreover, the better catalytic activity of Er2O3 species can be explained on the basis of active metal–support synergistic interactions and noticeable surface acidic nature. All the catalysts were characterized by X-ray diffraction analysis, Brunauer–Emmett–Teller (BET) surface area measurements, H2-temperature programmed reduction, ultraviolet–visible (UV–Vis) diffuse reflectance spectroscopy (DRS), Fourier-transform infrared spectroscopy, temperature-programmed desorption (NH3-TPD), scanning electron microscopy (SEM), and CO2 and O2 pulse chemisorption techniques to elucidate the metal oxide composition and influence of rare earth clusters such as Pr2O3, Nd2O3, and Er2O3 oxides on the catalytic activity.

Reactivity and deactivation mechanisms of pyrolysis chars from bio-waste during catalytic cracking of tar

The catalytic activity of pyrolysis chars from bio-waste was investigated for the cracking of model tar compounds (ethylbenzene and benzene). Two pyrolysis chars were produced at 700 °C from (1) used wood pallets (UWP), and (2) a 50/50 dry% mixture of food waste (FW) and coagulation-flocculation sludge (CFS). Steam activation at 850 °C was used to study the influence of the porous structure. While coke deposition is known to be responsible for the deactivation of carbonaceous chars and metal catalysts during tar cracking reactions, the deactivation of complex materials such as bio-waste chars has scarcely been studied. For this reason, special attention was paid on the relationships between the physicochemical properties of the chars, the operating conditions, and the deactivation mechanisms. To this aim, the cracking tests were performed over a wide temperature range: 400–650 °C for the ethylbenzene cracking, and 850–950 °C for benzene cracking. After the ethylbenzene cracking tests at 650 °C, the characterisations performed with SEM, BET, FTIR and Raman revealed that coke deposition was responsible for the char’s deactivation. The high specific surface area of activated chars explained their higher catalytic activity, and mesoporous catalysts were proved to be more resistant to coke deactivation than microporous catalysts. For these reasons, the higher ethylbenzene conversion (85.8%) was reached with the activated char from food waste and sludge (ac.FW/CFS). For benzene cracking at higher temperature (850 and 950 °C), the chars from food waste and sludge (FW/CFS) were the most active catalysts, despite their deactivation by the melting, diffusion and sintering of the inorganic species. This original deactivation mechanism, reported for the first time, led to the formation of an inorganic layer composed of P and Ca species at the char surface, with some areas rich in KCl and NaCl. Non-activated char from food waste and sludge (c.FW/CFS) was surprisingly proved to be more resistant to deactivation by inorganic species than the activated char (ac.FW/CFS) during the benzene cracking tests at 950 °C. This extended catalytic activity was explained by the activation of the non-activated char (c.FW/CFS) with the CO2 contained in the syngas which simultaneously developed the porosity and created new available active sites. This study marks a step forward in the understanding of the relationships between the deactivation mechanisms, the physicochemical properties of the chars, and the cracking temperature. Finally, a proposal for process integration is presented to consider the possibility to valorise the chars as catalysts to decompose the tar generated in the same pyro-gasification process.

Study of the Conjugation of Ethyl Benzene Dehydrogenation to Styrene with Steam Conversion of Carbon Monoxide on a Magnesium-Zirconium Catalyst

The steam conversion of carbon monoxide, the conjugation of the conversion of ethyl benzene (EB) to styrene (St) with the steam conversion of carbon monoxide (SCCM) and the conversion of ethyl benzene to styrene in the presence of CO2 on a low-temperature magnesium-zirconium catalyst modified with phosphoric acid and copper were studied. It has been established that by the conjugation of conversion of EB to styrene with the steam conversion of carbon monoxide, it is possible to create a highly efficient, environmentally friendly process for the production of styrene and hydrogen with a relatively low expenditure of additional capital and energy.

Oxidative Dehydrogenation of Ethylbenzene to Styrene on a Mixed Mo–V–Te–NbОх Oxide Catalyst under Thermal and Microwave Heating

A comparative study of the activity of a mixed oxide catalyst in the dehydrogenation of ethylbenzene (EB) to styrene at atmospheric pressure using О2 and СО2 as oxidants under conditions of conventional thermal and microwave heating is preformed. The dependences of conversion and selectivity on the composition of reaction mixtures are established. It is shown that replacing oxygen with CO2 leads to a substantial reduction in the conversion of EB with a simultaneous increase in the selectivity of the process. It is established that microwave heating with O2 used as an oxidizer provides increased efficiency of the process in the range of moderate (up to 420°С) temperatures. It is shown that the phase composition of the mixed oxide catalyst changes at higher temperatures. It is suggested this phenomenon is due to the appearance of hot points at the active reaction centers.

Utilization of CO2 and N2 for selective synthesis of styrene from ethylbenzene over high surface area γ-Al2O3 supported molybdenum nitride catalysts

The present work highlights the synthesis of styrene from ethylbenzene dehydrogenation by coupling with reverse water gas shift reaction (RWGSR) and ammonia synthesis reactions over high surface area Al2O3 supported molybdenum nitride (γ-Mo2N) catalyst. γ-Mo2N was prepared by in-situ thermal decomposition of molybdenum hexamethylenetetramine complex and the support high surface area Al2O3 (HSA) was prepared by sol-gel method. Different weight loadings of γ-Mo2N (10, 20 and 30) supported on HSA catalysts were systematically characterized by using powder XRD, N2 physisorption, H2 - TPR, XPS and TEM analysis. XRD, TEM and normalized BET surface area analysis reveal highly dispersed nitride species over HSA surface. The synthesized catalysts have been studied for ethylbenzene dehydrogenation reaction using CO2 and N2 as feed gases with different percentage compositions. It was found that CO2 rich N2 feed gas favors higher ethylbenzene conversion due to RWGSR and N2 rich CO2 favors higher selectivity to styrene due to ammonia synthesis. EB dehydrogenation along with RWGSR and ammonia synthesis reactions come along and privileged the formation of higher styrene yields.

La2O3 promotional effect to Co3O4/γ-Al2O3 catalyst in the oxidative dehydrogenation of ethylbenzene with CO2 as soft oxidant

Co3O4/γ-Al2O3 catalysts with variable Co3O4 loadings (5–20 wt%) and deposition of 15% Co3O4 on La2O3/γ-Al2O3 were prepared by wet impregnation method. La2O3-γ-Al2O3 support with variable composition of La2O3 (2–6 wt%) were prepared by co-precipitation method. All the catalysts were tested for oxidative dehydrogenation of ethylbenzene with CO2 as soft oxidant. Among the Co3O4/γ-Al2O3 catalysts, 15% Co3O4/γ-Al2O3 has shown good performance and hence this catalyst has been chosen to investigate the effect of La2O3 species. CO2 pulse chemisorption data indicate more amount of CO2 uptake over 15% Co3O4/4%La2O3/γ-Al2O3 catalyst which clearly indicates that this catalyst exhibits good performance in ethylbenzene dehydrogenation with CO2 as soft oxidant because of reverse water gas shift reaction. Temperature programmed reduction studies indicate that the Co3O4 catalysts follow two step reduction mechanism from Co3O4 to CoO and then to Co and La2O3 promotional effect is visible through facile reduction of Co3O4 species. La2O3 doping has a vital influence in getting enhanced ethylbenzene conversion, styrene yield and alleviates catalyst deactivation compared to that of unpromoted Co3O4/γ-Al2O3 catalyst. TGA studies indicate the presence low amount coke deposition during time-on-stream over 15% Co3O4/4%La2O3/γ-Al2O3 catalyst compared to 15% Co3O4/γ-Al2O3 catalyst.