Catalytic Oxidative Dehydrogenation Of Ethane Research Articles

Photocatalytic ethene synthesis from ethane dehydrogenation with high selectivity by ZnO-supported Pt nanoparticles

A Pt/ZnO photocatalyst is efficient and reusable for ethene production from ethane dehydrogenation with simulated sunlight, affording outstanding C2H4 productivity of 867.8 μmol h−1 g−1 and selectivity of 97.56%.

Avoiding false runaway prediction by properly describing axial conductive heat transfer in a low dt/dp industrial-scale packed bed reactor

The impact of axial conductive heat transfer on the simulation and prediction of hot spots and, more particularly, runaway, within an industrial-scale wall-cooled packed-bed reactor with low tube-to-particle diameter ratio (dt/dp ∼ 3) has been assessed in this work. To this purpose, the effective axial conductivity (keff,z) was first determined from adiabatic experiments in a bench-scale packed bed in the absence of reaction. Next, non-adiabatic and non-isothermal bench-scale and industrial-scale packed bed experimental data were used in the assessment of the impact of axial heat conduction on the prediction of the temperature profile. The so-called Pseudo-local Internal Heat Transfer Approach (PL-IHTA) was used for the adequate description of the radial temperature gradients. Finally, an industrial-scale wall-cooled packed bed reactor for the highly exothermic catalytic oxidative dehydrogenation of ethane was modeled to assess the impact of the axial thermal conductivity on temperature profile simulations. When disregarding axial heat conduction or adopting literature-based values for keff,z, determined from either experiments at low dt/dp ratios (<8) and Rep ≤ 1000 or high dt/dp ratios (>8) and Rep ≤ 700 at a wide panel of operating configurations, runaway is simulated at conditions where it has not been observed experimentally or a negligible hot-spot prediction is obtained. When considering the keff,z determined for the specific reactor configuration in this work, hot spots are predicted at Rep of 700 and 1400, but no runaway. The discrepancies between experimental findings and temperature profiles simulated using literature-based values for keff,z indicate the need for a specific determination of keff,z in packed bed reactors with low dt/dp ratio to more accurately predict hot spots, resulting in more reliable reactor design and operation.

Catalytic oxidative dehydrogenation of ethane using carbon dioxide as a soft oxidant over Co‐HMS catalysts to ethylene

AbstractIn this work, a series of cobalt doped hexagonal mesoporous silica (Co‐HMS) with the different Co content were prepared by direct hydrothermal method and applied to oxidative dehydrogenation (ODH) reaction of ethane with carbon dioxide. Structural and chemical properties of the catalysts were characterized by nitrogen adsorption, X‐ray powder diffraction (XRD), transmission electron microscopy (TEM), electron dispersive spectroscopy (EDS), X‐ray photoelectron spectroscopy (XPS), and Raman and ultraviolet–visible (UV‐vis) spectroscopy. These characterizations showed that cobalt not only entered the framework of Co‐HMS catalysts but also was evenly dispersed in the bulk. The valence state and coordination mode of cobalt played an important role in the whole ODH reaction system of ethane with carbon dioxide. 2% Co‐HMS with dominant Co2+ had the highest conversion of ethane (26.0%). With the different cobalt content in the catalyst, the proportion of Co2+(Td) and Co2+(Oh) is also different. 1% Co‐HMS with more Co2+(Td) performed the highest ethylene selectivity of 86.7%, which was stable during the 10 h reaction time.

SiO2-Modified Pt/Al2O3for Oxidative Dehydrogenation of Ethane: A Preparation Method for Improved Catalytic Stability, Ethylene Selectivity, and Coking Resistance

A SiO2-modified Pt/Al2O3 catalyst (SiO2/Pt/Al2O3) was synthesized with a solution-based method using Pt/Al2O3 as the starting catalytic material and tetraethoxysilane (TEOS) as the Si precursor. The modification process can be conducted with several cycles. Each of the modification cycles included sequentially an evacuation step at an elevated temperature and an impregnation step followed by a solution-treatment step. The introduced SiO2 layer showed an obvious sintering-resisting effect for the Pt nanoparticles at a high temperature of 600 °C. When used for catalytic oxidative dehydrogenation of ethane (ODHE), SiO2/Pt/Al2O3 presented a significantly improved catalytic stability and coking depression compared to the unmodified Pt/Al2O3. Furthermore, the introduced SiO2 layer helped improve the ethane conversion slightly and the selectivity to ethylene mildly. The improved selectivity to ethylene could be associable with the Bronsted acid sites brought by the SiO2 layer as well as site distribution of the ...

Oxidative dehydrogenation of ethane using MoO3/Fe2O3 catalysts in a cyclic redox mode

Oxidative dehydrogenation (ODH) of ethane offers large reductions in energy consumption and associated greenhouse gas emissions when compared to conventional steam cracking for ethylene production; however, catalytic ODH of ethane using co-fed O2 requires expensive air separation. As an alternative, we are investigating novel core-shell catalysts that utilize lattice oxygen (O2−) as the sole oxidant and operate in a cyclic redox mode. In this work, redox catalysts having 1, 3 and 6 monolayer (ML) equivalents of MoO3 on α-Fe2O3 and a stoichiometric ferric molybdate, Fe2(MoO4)3, were prepared, characterized by powder x-ray diffraction (XRD), x-ray photoelectron spectroscopy (XPS), diffuse-reflectance infrared Fourier transform spectroscopy (DRIFTS), and temperature-programmed reduction (TPR) and evaluated for ethane ODH in a cyclic redox mode at 600 °C. The characterization data are consistent with a core-shell structure for the calcined MoO3/Fe2O3 catalysts with a mixed Mo-Fe oxide surface layer. H2 and ethane TPR evidence that the shell inhibits Fe2O3 reduction and decreases the ethane combustion activity of the fully oxidized catalyst. Covering the Fe2O3 core with MoO3 also increases ODH activity and ethylene selectivity. In cyclic redox mode at 600 °C, ethylene selectivity was 57–62% for catalysts with 3 and 6 ML equivalents of MoO3.

Mixed oxide Ti[sbnd]Si[sbnd]O prepared by non-hydrolytic Xerogel method as a diluter of nickel oxide for the oxidative dehydrogenation of ethane

Mixed TiSiO materials prepared by non-hydrolytic xerogel method have been employed as diluters for nickel oxide and used in the catalytic oxidative dehydrogenation of ethane. These catalysts have been characterized by several physicochemical techniques such as N2 adsorption, XRD, TPR, TEM, HR-TEM, and XPS. Supported nickel oxide catalysts have been reported to be efficient but only if the nature and the amount of support are controlled. In the present article it is shown that highly loaded (80wt% NiO) nickel catalysts are more efficient when diluted on mixed TiSiO materials with appropriate Ti/Si ratios than on pure TiO2 and SiO2 diluters. The catalytic results have been explained on the basis of both the crystallite size and the reducibility of NiO crystallites, as a consequence of the interaction between nickel oxide particles and metal oxides diluters. The optimal Ti/Si ratio in the diluter ensures a good dispersion of NiO because Ti4+ sites and/or very small TiO2 crystallites are highly dispersed in the surface of the matrix allowing a close contact with NiO particles. Small NiO crystallites in contact with titania are highly selective to ethylene in the oxidative dehydrogenation of ethane.

Oxidative dehydrogenation of ethane over Dy2O3/MgO supported LiCl containing eutectic chloride catalysts

The catalytic oxidative dehydrogenation of ethane with alkali and alkaline earth metal chloride modified LiCl supported on Dy2O3/MgO (MD) was studied. Eutectic mixtures of alkali and alkaline earth metal chloride with LiCl are formed on the support surface decreasing so the melting point of pure LiCl to temperatures as low as 366°C (Li-K-MD). All samples had weak basicity decreasing in the order: Li-K-MD<Li-Sr-MD Li-Ba-MD<Li-Na-MD<Li-MD. Physisorbed and chemisorbed CO2 species are identified for all materials studied by in situ IR spectroscopy. Bidentate carbonate species are the most abundant on Li-MD, while on modified samples bi- and unidentate carbonate species exist. The catalyst activity increases with decreasing basicity. Catalyst selectivity increases with increasing reaction temperature and is constant above a threshold temperature. The maximum ethene selectivity is directly correlated with the melting point of the eutectic melt on the catalyst support.

Cobalt speciation in cobalt oxide-apatite materials: structure–properties relationship in catalytic oxidative dehydrogenation of ethane and butan-2-ol conversion

Impregnation of calcium hydroxyapatite by a solution of Co(II) nitrate followed by calcination at 823 K gives rise to various species, depending on the cobalt content. At low cobalt content (0.2 wt%), the cobalt species are isolated six-coordinated Co2+ ions. For Co content ≥0.4 wt%, the presence of tetrahedral Co2+ and octahedral Co3+ species is attested by UV–visible–NIR spectroscopy, magnetic measurements and XPS data. Magnetic data at low temperature suggest the formation of clustered CoxOy entities. For Co content ≥1.7 wt%, Co3O4 nanocrystals are generated, as evidenced by XRD and magnetic measurements.In the presence of oxygen, the butan-2-ol conversion produces only butan-2-one. The most active catalysts are the cobalt poorest samples which contain only isolated Co2+ ions. Oxidative dehydrogenation of ethane gives a similar trend. Upon increasing the cobalt loading above 0.9 wt%, the specific dehydrogenation activity of Co2+ ions decreases because the nature of the sites changes and the basic properties are lowered. Relationships between the nature of the sites and the catalytic performances are proposed.

Oxidative dehydrogenation of ethane in a fluidized bed membrane reactor

The performance of a pilot scale fluidized bed membrane reactor (FLBMR) was studied experimentally in comparison to the conventional operation as a fluidized bed reactor (FLBR) for the catalytic oxidative dehydrogenation of ethane using a γ-alumina supported vanadium oxide catalyst. For both reactor configurations, the influence of process parameters such as temperature and contact time was investigated. Further, the experimental data obtained were compared to previous experiments with a fixed-bed reactor (FBR) and a packed-bed membrane reactor (PBMR) operated with a similar catalyst. For identical overall feed rates, the distributed oxidant feeding in the FLBMR improves the selectivity to ethylene significantly. The beneficial effect of oxidant dosing over the membrane is most pronounced at high temperatures and long contact times. Under limiting oxidant supply the FLBMR and the PBMR show a similar performance, but under moderate oxygen excess the FLBMR outperforms the PBMR significantly. The maximum ethylene yield observed in the FLBMR was 37% compared to 35% for the PBMR. Beside a high productivity, for the FLBMR a broader favorable operation range with respect to the oxygen–hydrocarbon ratio was observed, what indicates a lower sensitivity against oscillations and disturbances in the reactant feed, corresponding to a higher safety of operation. Because of an excellent heat transfer characteristics, the fluidized bed membrane reactor concept is very promising for maximizing the yield of the desired intermediates also in large-scale plants, especially for strongly exothermic reactions.

Catalytic composites based on yttria stabilized zirconia for oxidative dehydrogenation of ethane

LiCl/YSZ is found to be a very effective catalyst for the oxidative dehydrogenation of ethane. LiCl supported on YSZ-MgO composite shows increase in catalytic activity and ethylene selectivity. Addition of Mn and Sn as pro- moters to this system leads to 85% ethane conversion, 77% ethylene selectivity and 65% ethylene yield at 662 o C. Use of Li2O in the place of LiCl results in lower ethylene yields. Further modification is needed to improve the catalyst stability. o C. High investment costs, frequent shutdowns of the cracker units for de-coking, requirement of furnace tubes of special metal- lurgy and periodic replacement of the tubes are the other motivat- ing factors behind the global research efforts to develop an econom- ically viable alternative process for production of ethylene. Among the various alternative routes, catalytic oxidative dehydrogenation of ethane (ODE) to ethylene has received considerable attention, and the developments in this area have been covered by a number of exhaustive reviews (Cavani and Trifiro, 1995, 1999; Baerns and Buyevskaya, 1998; Banares, 1999). Numerous catalyst formulations based on oxides of V-Nb-Mo, alkali (Li 2O) and alkaline earth oxides (MgO), rare earth oxides (of La, Nd, Sm & Dy) and their combi- nations with several transition metals oxides (Li-Mn-W/TiO 2 & Mn- Na2WO4/SiO2) have been reported as effective catalysts for ODE (Liu et al., 1998). LiCl supported on sulfated zirconia (SZ) has been found to be highly effective for ODE (Wang et al., 1999). YSZ (yttria stabi- lized zirconia) is another support that is useful for ODE. Its ability to pump reactive oxygen through oxygen anion conduction is respon- sible for its activity in oxidative ethane dehydrogenation. Otsuka et al. (1995) reported that the role of YSZ was to increase the number of O *

A Comparison of Catalytic Oxidative Dehydrogenation of Ethane Over Mixed V-Mg Oxides and Over Those Prepared via a Mesoporous V-Mg-O Pathway

The catalytic oxidative dehydrogenation of ethane was investigated in a fixed-bed tubular microreactor at 500, 550 and 600 °C and a space velocity of 35 027ml g-1h-1. Two kinds of V-Mg oxides catalysts containing various V/Mg atomic ratios were employed. One group of catalysts was prepared by the solid reaction between fine powders of vanadium pentoxide and magnesium nitrate and the other ones were obtained from mesostructured V-Mg-Os. For the former catalysts, it was found that the selectivity to ethene increased and the conversion of ethane passed through a maximum with increasing V/Mg atomic ratio. For the catalysts obtained from the mesoporous materials, an optimum V/Mg atomic ratio was found, for which the conversion of ethane and the selectivity to ethene were maxima. Compared with the mixed-oxide catalysts, those obtained from the mesoporous materials exhibited much higher yields to ethene. Several new phases, such as pyro-Mg2V2O7, ortho-Mg3(VO4)2 and meta-MgV2O6, formed between magnesia and vanadia, were identified by XRD in the mixed V-Mg oxide catalysts; they may be responsible for the catalytic activity. In the catalysts prepared from mesoporous V-Mg-O, a V2O3 phase, which may contain highly dispersed magnesium, was identified and suggested to be responsible for the higher catalytic performance.

A comparative study on non-catalytic and catalytic oxidative dehydrogenation of ethane to ethylene

Studies on the catalytic and non-catalytic oxidative dehydrogenation of ethane (ODE) to ethylene have been carried out between 600 and 800 °C in the presence of 30% of steam in the feed and in its absence at a contact time of 0.2 g s ml −1 and at C 2H 6/O 2 ratio ranging from 2 to 8. For the catalytic experiments Sr 1.0La 1.0Nd 1.0O x was used as a catalyst. For a low dead reactor volume, homogeneous gas-phase reactions were not significant up to 700 °C as compared to the catalytic ones. Above 700 °C the non-catalytic ODE reaction occurred to a large extent resulting in ethylene yields of 46% ( S=66%) and 53% ( S=65%) at 750 and 800 °C, respectively. In the presence of a Sr 1.0La 1.0Nd 1.0O x catalyst the highest ethylene yield amounted to 46% ( S=71%) at an inlet temperature of 700 °C. For the catalytic ODE reaction, ignition of the reaction mixture which resulted in an increased temperature in the catalyst zone as compared to the inlet temperature could not be excluded even at a low space velocity. The addition of steam to the feed gas affected the catalytic as well as the non-catalytic ODE reaction slightly.

Oxidative Dehydrogenation of Ethane over Alkali Metal Chloride Modified Silica Catalysts

The catalytic oxidative dehydrogenation of ethane into ethylene was investigated over a series of alkali metal chloride supported on silica catalysts. It is found that alkali metal chloride modified silica catalysts show much higher activity in the selective oxidation of ethane than silica support itself, and their catalytic activity depends on the nature of alkali metal and its loading. LiCl/SiO2 exhibits the highest ethane conversion and ethylene yield, giving 99% ethane conversion and 80% ethylene selectivity at 600 °C. However, it shows rapid deactivation. NaCl/SiO2 shows high conversion and a longer stability. On the contrary, KCl/SiO2 displays the lowest ethane conversion but a high deactivation rate. Characterization of the catalysts reveals that the activity variation can be related to the redox and acid−base properties of the catalysts. The deactivation of catalytic activity can be attributed to the loss of chlorine and chemical phase transformation.

Acetylene formation during the catalytic oxidative dehydrogenation of ethane over Pt-coated monoliths at short contact times

Short contact time monolithic reactors have been examined for the production of ethylene by oxidative dehydrogenation over a supported Ptcatalyst. The results so far suggest that these reactors may revolutionize the way chemical synthesis is conducted, but many questions remain. This paper addresses the co-production of acetylene. Under some conditions, acetylene is produced as a by-product during the oxidative dehydrogenation of ethane. This acetylene formation appears to be due to homogeneous reactions since the acetylene production increases at higher reaction temperatures and under conditions where there is little available surface area for radical quenching.

ChemInform Abstract: Homogeneous and Heterogeneous Contributions to the Catalytic Oxidative Dehydrogenation of Ethane.

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Homogeneous and heterogeneous contributions to the catalytic oxidative dehydrogenation of ethane

The oxidative dehydrogenation of ethane to ethene has been studied in a quartz reactor in the absence and in the presence of a range of MgO-based catalysts using a variety of gas compositions over a range of temperatures. The results show that under optimum conditions the non-catalysed reaction can be very efficient and selective. At a temperature of 600°C, using an ethane/air ratio of 1:2, a conversion of 45% was achieved at a selectivity of 73.7%, corresponding to a percentage yield of ethene of 33% and a space-time yield of ethene of 15.8 mmol/cm 3 h. It was observed that none of the catalysts tested under comparable conditions gave such high yields. Reasons for this difference are discussed. Comparison with published results on the catalytic oxidative dehydrogenation of ethane suggest that the non-catalysed gas-phase reaction is competitive with the best available catalysts.