Oxidative Dehydrogenation Of N-butane Research Articles

A Fluidizable Catalyst for N-Butane Oxidative Dehydrogenation under Oxygen-Free Reaction Conditions

This study evaluates the effectiveness of fluidizable VOx/MgO-γAl2O3 catalysts for C4-olefin production via n-butane oxidative dehydrogenation (BODH). Catalysts were prepared via vacuum incipient wetness impregnation and then characterized by employing several techniques such as BET (Brunauer–Emmett–Teller) method, XRD (X-ray diffraction), LRS (laser Raman spectroscopy), XPS (X-ray photoelectron spectroscopy), TPR/TPO (temperature-programmed reduction/temperature-programmed oxidation), NH3-TPD (temperature-programmed desorption), NH3 -desorption kinetics and pyridine-FTIR. The BET analysis showed the prepared catalysts’ mesoporous structure and high surface areas. The XRD, LRS and XPS established the desirable presence of amorphous VOx phases. The TPR/TPO analyses corroborated catalyst stability over repeated reduction and oxidation cycles. The NH3-TPD and NH3 desorption kinetics showed that the catalysts had dominant moderate acidities and weak metal-support interactions. In addition, Pyridine-FTIR showed the critical influence of Lewis acidity. The VOx/MgO-γAl2O3 catalysts were evaluated for BODH using a fluidized CREC Riser Simulator, operated under gas-phase oxygen-free conditions, at 5 to 20 s reaction times, and at 450 °C to 600 °C temperatures. The developed VOx/MgO-γAl2O3 catalysts demonstrated performance stability throughout multiple injections of butane feed. Catalyst regeneration was also conducted after six consecutive BODH runs, and the coke formed was measured using TOC (Total Organic Carbon). Regarding the various BODH catalyst prepared, the 5 wt% V-doped MgO-γAl2O3 yielded in a fluidized CREC Riser Simulator the highest selectivity for C4-olefins, ranging from 82% to 86%, alongside a butane conversion rate of 24% to 27%, at 500 °C and at a 10 s reaction time.

Influence of Zn and Fe Promoters on Ni-Bi/Γ-Al2o3 Catalyst for Oxidative Dehydrogenation of N-Butane to Butadiene

Influence of Zn and Fe Promoters on Ni-Bi/Γ-Al2o3 Catalyst for Oxidative Dehydrogenation of N-Butane to Butadiene

Structure, Acidity, and Redox Aspects of VOx/ZrO2/SiO2 Catalysts for the n-Butane Oxidative Dehydrogenation

ZrOx/SiO2 and VOx/ZrOx/SiO2 catalysts (5 wt %–25 wt % Zr, 4 wt % V) were prepared by grafting zirconium and vanadium alkoxides on Aerosil 380. All samples were characterized by temperature programmed reduction, N2 physisorption, X-ray diffraction, Raman spectroscopy, and ammonia adsorption microcalorimetry. Tetragonal ZrO2 and zircon (ZrSiO4) were present at 25 wt % Zr, but only amorphous zirconia overlayer existed for lower loadings. At lower Zr loadings (5 wt %–10 wt % Zr), exposed silica surface leads to V2O5 crystallites and isolated VO4 species, although V reducibility behavior changes, from being similar to VOx/SiO2 (5 wt % Zr) to showing VOx/ZrO2 behavior at 10 wt % Zr, and a diminished total amount of reducible V. Highly acidic ZrO2 sites are covered by the vanadium grafting, forming weaker sites (60–100 kJ/mol NH3 adsorption strength). Catalytic conversion and selectivity for the oxidative dehydrogenation of n-butane (673 K, n-C4/O2 = 2.2) over VOx/ZrOx/SiO2 show that 1,3-butadiene is favored over cis-2-butene and trans-2-butene, although there is some selectivity to the 2-butenes when VOx/ZrO2 behavior is evident. At low Zr loadings, butadiene formed during reaction acts as the diene species in a Diels–Alder reaction and gives rise to a cyclic compound that undergoes further dehydrogenation to produce benzaldehyde.

Kinetic Study on n-Butane Oxidative Dehydrogenation over the (Ni, Fe, Co)–Bi–O/γ-Al2O3 Catalyst

The oxidative dehydrogenation of n-butane was investigated over a highly selective (Ni, Fe, Co)–Bi–O/γ-Al2O3 catalyst with kinetic studies. The transient response method with O2 concentration was a...

Grignard reagent reduced nanocarbon material in oxidative dehydrogenation of n-butane

A modification route of nanocarbon catalyst based on Grignard reagent reduction of oxidized carbon nanotubes (o-CNTs) has been developed for oxidative dehydrogenation (ODH) of n-butane. The o-CNTs contain considerable amount of electrophilic oxygen species which are responsible for deep oxidation side-reactions and the alkene selectivity in ODH is low. After Grignard reduction, the corresponding electrophilic oxygen groups on the surface of the catalyst were eliminated and the basicity increased. As a result, the side-reactions in ODH were prohibited and the alkene selectivity was significantly improved compared with o-CNTs. The chlorine containing Mg/Cl species were found to have positive effect on the improvement of C4H8 alkene yield. This study provides a method of the preparation of nanocarbon catalyst to achieve higher alkene selectivity for the dehydrogenation reaction.

Improving the Alkene Selectivity of Nanocarbon-Catalyzed Oxidative Dehydrogenation of n-Butane by Refinement of Oxygen Species

Nanocarbon materials are promising catalysts of oxidative dehydrogenation (ODH) of alkanes, but improving the alkene selectivity remains a challenge. A deep understanding and thorough identification of oxygen species on nanocarbons are strongly required for approaches to nanocarbon modification. Successful application of iodometric titration in quantitative determination of the amount of electrophilic oxygen on the surface of carbon nanotubes has been performed in this work. Electrophilic oxygen species have been identified as the main culprits for deep oxidation of ODH of n-butane via a clear correlation between the amount of electrophilic oxygen and combustion reaction rate. By chemical reduction and annealing in nitrogen, the alkene selectivity is significantly improved. Phenol groups are found to play an essential role in improving alkene selectivity. The study reveals that higher alkene selectivity can be achieved by both eliminating deep oxidation active sites and facilitating the formation of pheno...

Comprehensive Understanding of the Effects of Carbon Nanostructures on Redox Catalytic Properties and Stability in Oxidative Dehydrogenation

The intrinsic redox catalytic properties of metal-free carbons have been widely investigated due to their fundamental interest as well as potential practical applications. Although a large variety of nanostructured carbons are now available, the effects of carbon nanostructures on redox properties have not been comprehensively understood. In this work, the redox catalytic properties and thermochemical stabilities of 16 different types of carbons, including activated carbon, carbon nanotubes, onion-like carbons, and microporous/mesoporous templated carbons were systematically investigated using n-butane oxidative dehydrogenation as a model reaction. The results demonstrate that the overall catalytic activity increases with increasing content of C═O active sites. However, with increasing C═O content, the activity per site (i.e., turnover frequency) gradually decreases, while the alkene selectivity increases due to the decreased reducibility of each C═O site. Since more C═O sites are present in a thermochemi...

Kinetic modeling of the anaerobic oxidative dehydrogenation of n-butane

Kinetic modeling of the anaerobic oxidative dehydrogenation of n-butane

A Facile and Efficient Method to Fabricate Highly Selective Nanocarbon Catalysts for Oxidative Dehydrogenation.

Carbon nanotubes (CNTs) were used in oxidative dehydrogenation (ODH) reactions. Quinone groups on the CNT surface were identified as active sites for the dehydrogenation pathway. Liquid-phase oxidation with HNO3 is one way to generate various oxygen functionalities on the CNT surface but it produces a large amount of acid waste, limiting its industrial application. Here, a facile and efficient oxidative method to prepare highly selective CNT catalysts for ODH of n-butane is reported. Magnesium nitrate salts as precursors were used to produce defect-rich CNTs through solid-phase oxidation. Skeleton defects induced on the CNT surface resulted in the selective formation of quinone groups active for the selective dehydrogenation. The as-prepared catalyst exhibited a considerable selectivity (58 %) to C4 olefins, which is superior to that of CNTs oxidized with liquid HNO3 . Through the introduction of MgO nanoparticles on the CNT surface, the desorption of alkenes can be accelerated dramatically, thus enhancing the selectivity. This study provides an attractive way to develop new nanocarbon catalysts.

Composition effect of metal species in (Ni, Fe, Co)-Bi-O/gamma-Al2O3 catalyst on oxidative dehydrogenation of n-butane to butadiene

Abstract The effect of metal oxide species in (Ni, Fe and/or Co) oxide-Bi 2 O 3 over gamma-alumina support was investigated for n-butane oxidative dehydrogenation. Partial substitution of Ni up to 50% by Fe improved butadiene selectivity while same substitution with Co increased n-butane conversion. The ternary Ni-Fe-Co system (10 wt% Ni–5 wt% Fe–5 wt% Co–30 wt% Bi-O/gamma-Al 2 O 3 ) showed the highest butadiene selectivity of 46.3% at n-butane conversion of 30%. The acid-base sites preferably adjusted by ternary main metal combination in hierarchical cohabitation of metal (Ni, Fe and Co) oxide, Bi 2 O 3 and gamma-Al 2 O 3 cooperate to accelerate butadiene selectivity at both 1st and 2nd step dehydrogenations due to an increased H 2 abstraction and 1-butene intermediate adsorption.

Nature of active sites and deactivation mechanism for n-butane isomerization over alumina-promoted sulfated zirconia

The deactivation of n-butane isomerization on alumina-promoted sulfated zirconia (SZA) was studied at 473K under atmospheric pressure. Under N2, the regeneration temperature influences the isomerization activity greatly. The change of the sulfate species during the deactivation process was determined quantitatively by a temperature-programmed evolution mass spectrometer. Two active sites, reducible sites and acid sites, exist on the catalyst surface and show a synergistic effect on the n-butane isomerization reaction. The reducible sulfate species play an important role in butene formation via oxidative dehydrogenation of n-butane, while the acid sites are responsible for the isomerization steps. The reduction of sulfate species and the accumulation of sulfite species on the surface, which cause the decrease of butene concentration in the catalyst bed, are the main reasons for catalyst deactivation. Based on these findings, a new reaction model and two possible ways to improve the catalytic stability of SZA catalyst are proposed.

Phosphate modified carbon nanotubes for oxidative dehydrogenation of n-butane

Catalytic performance of phosphate-modified carbon nanotube (PoCNT) catalysts for oxidative dehydrogenation (ODH) of n-butane has been systematically investigated. The PoCNT catalysts are characterized by SEM, TEM, XPS and TG techniques. We set the products selectivity as a function of butane conversion over various phosphate loading, and it is found that the PoCNT catalyst with the 0.8% phosphate weight loading (0.8PoCNT) exhibits the best catalytic performance. When the phosphate loading is higher than 0.8wt%, the difference of catalytic activity among the PoCNT catalysts is neglectable. Consequently, the ODH of n-butane over the 0.8PoCNT catalyst is particularly discussed via changing the reaction conditions including reaction temperatures, residence time and n-butane/O2 ratios. The interacting mechanism of phosphate with the oxygen functional groups on the CNT surface is also proposed.

Activity of Molybdenum Oxide Catalyst Supported on Al2O3, TiO2, and SiO2 Matrix in the Oxidative Dehydrogenation of n-Butane

The catalytic oxidative dehydrogenation (ODH) of light alkanes has great potential to be used for production of alkenes instead of classically used steam cracking of naphtha. We report for the first time a comparison of molybdenum oxide species supported on three different industrially relevant mesoporous supports—Al2O3, SiO2 and TiO2 in ODH of n-butane. All samples were prepared by wet impregnation and characterized by ICP-EOS for determination of molybdenum content, XRD and N2-adsorption for study of morphology and texture, H2-TPR and DR UV–vis spectroscopy for determination of molybdenum complex speciation and by NH3-TPD for study of acidity. All prepared materials were tested in n-butane ODH reaction at 540 °C and iso-conversion conditions. The molybdenum oxide supported on alumina exhibited the extraordinary high productivity (1.16 kgprod kg cat −1 h−1) in ODH of n-butane which is one of the five highest C4-deh productivity values which were published for ODH of n-butane in open literature. Moreover, this catalyst exhibit high selectivity to 1,3-butadine in comparison with other catalysts tested in n-butane ODH.

Vanadium Oxide Supported on Titanosilicates for the Oxidative Dehydrogenation of n-Butane

Vanadium-containing titanosilicates and V-containing SBA-15 catalysts for oxidative dehydrogenation (ODH) of n-butane at lower temperatures and with lower vanadia contents were contrastively studied. The catalysts were investigated by various techniques, namely, N2 adsorption–desorption, SAXS, TEM, FT-IR, XRD, XRF, H2-TPR, O2-TPD, and XPS, in relation to their performance for the ODH of n-butane. Results reveal that titanosilicate materials synthesized exhibit mesoporous structure, high BET specific surface area, and high total pore volume. H2-TPR, O2-TPD, and XPS results show that lattice oxygen exists in the surface of the V-containing titanosilicate catalysts and enhances the reducibility of vanadia-based catalysts with increasing TiO2 loadings. The V-containing titanosilicate catalysts exhibit much higher catalytic activity for the ODH of n-butane than that of V-containing SBA-15 at a significantly lower temperature of 460 °C, which indicates that lattice oxygen in the catalyst plays an important role...

Influence of calcination on performance of Bi–Ni–O/gamma-alumina catalyst for n-butane oxidative dehydrogenation to butadiene

Influence of calcination on the binary-metal oxide 30 wt% Bi-20 wt% Ni–O/gamma-Al2O3 catalyst was studied for n-butane oxidative dehydrogenation to 1,3-butadiene.

Mg3(VO4)2-MgO-ZrO2 nano-catalysts for oxidative dehydrogenation of n-butane.

A series of X-Mg3(VO4)2-MgO-ZrO2 nano-catalysts with different vanadium content (X = 3.3, 5.3, 7.0, 10.2, and 13.4) were prepared by a single-step citric acid-derived sol-gel method for use in the oxidative dehydrogenation of n-butane to n-butene and 1,3-butadiene. The effect of vanadium content of X-Mg3(VO4)2-MgO-ZrO2 nano-catalysts on their physicochemical properties and catalytic activities in the oxidative dehydrogenation of n-butane was investigated. Successful formation of X-Mg3(VO4)2-MgO-ZrO2 nano-catalysts was confirmed by XRD, Raman spectroscopy, and ICP-AES analyses. The catalytic performance of X-Mg3(VO4)2-MgO-ZrO2 nano-catalysts strongly depended on vanadium content. All the X-Mg3(VO4)2-MgO-ZrO2 nano-catalysts showed a stable catalytic performance without catalyst deactivation during the reaction. Among the catalysts tested, 7.0-Mg3(VO4)2-MgO-ZrO2 nano-catalyst showed the best catalytic performance in terms of yield for total dehydrogenation products (TDP, n-butene and 1,3-butadiene). TPRO (temperature-programmed reoxidation) experiments were carried out to measure the oxygen capacity of the catalyst. Experimental results revealed that oxygen capacity of the catalyst was closely related to the catalytic performance. Yield for TDP increased with increasing oxygen capacity of the catalyst.

CO2 promoted oxidative dehydrogenation of n-butane over VOx/MO2–ZrO2 (M = Ce or Ti) catalysts

The CO2 promoted oxidative dehydrogenation (ODH) of n-butane was investigated over mixed metal oxide supported vanadium catalysts. The investigated mixed metal oxide supports namely, CeO2–ZrO2 (CZ) and TiO2–ZrO2 (TZ) were synthesized by coprecipitation method, and the vanadium oxide was deposited on the supports by wet impregnation method. The synthesized samples were characterized by BET surface area, X-ray diffraction (XRD), temperature programmed reduction (TPR), and X-ray photoelectron spectroscopy (XPS) techniques. The XRD analysis of CZ and CZ supported V2O5 samples revealed the formation of CexZr1−xO2 solid solution and a highly dispersed vanadium oxide over the CZ support, respectively. On the other hand, different mixed oxide phases (ZrV2O7 and TiZrO4) were observed in the case of TZ supported vanadia catalyst. The TPR reduction temperature of supported samples is lower than the bulk V2O5. XPS results revealed that vanadium and cerium are in V5+ and Ce4+/Ce3+ oxidation states, respectively. Among the investigated catalysts, the CZ supported vanadium oxide catalyst exhibited a high activity and good time-on-stream stability. The redox property of the catalyst significantly influenced the catalytic activity in the ODH of n-butane with CO2.

Oxidative Dehydrogenation of n-Butane Over Magnesium Vanadate Nano-Catalysts Supported on Magnesia–Zirconia: Effect of Vanadium Content

Magnesia-zirconia (MgO-ZrO2) support was prepared by a sol-gel method, and magnesium vanadate nano-catalysts supported on magnesia-zirconia (X-Mg3(VO4)2/MgO-ZrO2) were then prepared by a wet impregnation method with a variation of vanadium content (X = 6.6, 9.9, 12.8, 15.2, and 19.1 wt%). X-Mg3(VO4)2/MgO-ZrO2 nano-catalysts were applied to the oxidative dehydrogenation of n-butane to n-butene and 1,3-butadiene. The formation of X-Mg3(VO4)2/MgO-ZrO2 nano-catalysts was well confirmed by XRD, XPS, and ICP-AES analyses. 15.2-Mg3(VO4)2/MgO-ZrO2 and 19.1-Mg3(VO4)2/MgO-ZrO2 catalysts experienced a catalyst deactivation, while the other Mg3(VO4)2/MgO-ZrO2 catalysts showed a stable catalytic performance during the whole reaction time. The effect of oxygen property of X-Mg3(VO4)2/MgO-ZrO2 nano-catalysts on the catalytic performance in the oxidative dehydrogenation of n-butane was investigated. Experimental results revealed that oxygen capacity of the catalyst was closely related to the catalytic performance, while oxygen mobility of the catalyst played an important role in the catalyst stability. Among the catalysts tested, 12.8-Mg3(VO4)2/MgO-ZrO2 catalyst showed the best catalytic performance in terms of yield for TDP (total dehydrogenation products).

Vanadium Mesoporous Silica Catalyst Prepared by Direct Synthesis as High Performing Catalyst in Oxidative Dehydrogenation of n-Butane

The catalytic oxidative dehydrogenation (ODH) of light alkanes has great potential to be used for production of alkenes instead classically used dehydrogenation. We report successful direct synthesis of vanadium mesoporous silica material—nSi/nV = 10 which could be convenient catalyst for ODH of alkane. The extraordinary high productivity (1.92 kgprod kg cat −1 h−1) in n-butane ODH is 3–4 times higher in comparison to supported vanadium catalysts usually prepared by wet impregnation method. It ranks this catalyst among the best materials investigated so far in this reaction. Moreover, reported catalytic system exhibits catalytic activity stable for more than 8 h in the stream.

Oxidative dehydrogenation of n-butane over bimetallic mesoporous and microporous zeolites with CO2 as mild oxidant

Oxidative dehydrogenation of n-butane was tested using carbon dioxide as a mild oxidant over bimetallic Cr–V supported catalysts (MCM-41, ZSM-5, MCM-22 and mesoZSM-5). The textural properties of the catalysts were measured by means of XRD, N2 adsorption, SEM-EDX, Raman, H2-TPR, pyridine FT-IR, NH3 and CO2-TPD techniques. The metal content of Cr and V was maintained around 1.2 and 2.8 wt% for the catalytic test in packed bed reactor at different temperatures (525–600 °C) for 180 min. 1.2Cr2.8 V/MCM-41 and 1.2Cr2.8 V/ZSM-5 exhibited maximum conversion of 14 and 13.1 %, respectively at 10 min and 600 °C. Significantly, high butenes selectivity was observed over MCM-41 (86.27 %) than ZSM-5 support (58.1 %). The mesoporosity in ZSM-5 had a negative impact on conversion level (7.1 %) but improved the butenes selectivity slightly. 1.2Cr2.8 V/M-22 showed the highest cracking ability leading to overall reduced butenes selectivity (57.9 %). The study shows that over all catalysts, n-butane conversion is independent of CO2 conversion. 1.2Cr2.8 V/M-22 showed highest CO2 conversion in the range 2.35–2.2 % between 525 and 550 °C. The apparent activation energies of dehydrogenation and cracking reaction over the four catalysts were evaluated. The ratio of conversion to coke weight per cent over the four catalysts are observed in the following order: 1.2Cr2.8 V/M-41 > 1.2Cr2.8 V/Z-5 > 1.2Cr2.8 V/mesoZ-5 > 1.2Cr2.8 V/M-22.