Deep Oxidation Of Propane Research Articles

Ga2O3/La2O3-γAl2O3 catalysts for CO2-assisted propane oxidative dehydrogenation to propylene

Novel Ga2O3/La2O3-γAl2O3 was investigated for ODH of propane to propylene using CO2 as a mild oxidant in a batch scale fluidized CREC Riser Simulator. La2O3 in the catalysts provided a control of both the reducibility and acidity, as shown by H2-TPR and NH3-TPD, respectively. The propane conversion and products selectivity were strong function of La2O3 content in the Ga2O3/La2O3-γAl2O3 catalysts. With increasing La2O3 content in the catalyst, propane conversion dropped slightly but the propylene selectivity and yields increased. It was proposed that the presence of La2O3 reduced the non-selective sites and the acidity of the catalysts, that contributed towards deep oxidation of propane and propylene. The improved activity and selectivity with CO2 addition implied that the as-synthesized catalyst possesses CO2 activation capability required for ODH reactions. Among the investigated catalysts, Ga2O3/La2O3-γAl2O3(1:1) exhibited the highest propane conversion (92 %) and propylene yield (56 %) at 600 ℃ in the presence of CO2.

Investigation of AFeO3 (A=Ba, Sr) Perovskites for the Oxidative Dehydrogenation of Light Alkanes under Chemical Looping Conditions.

Oxidative dehydrogenation (ODH) of light alkanes to produce C2-C3 olefins is a promising alternative to conventional steam cracking. Perovskite oxides are emerging as efficient catalysts for this process due to their unique properties such as high oxygen storage capacity (OSC), reversible redox behavior, and tunability. Here, we explore AFeO3 (A=Ba, Sr) bulk perovskites for the ODH of ethane and propane under chemical looping conditions (CL-ODH). The higher OSC and oxygen mobility of SrFeO3 perovskite contributed to its higher activity but lower olefin selectivity than its Ba counterpart. However, SrFeO3 perovskite is superior in terms of cyclic stability over multiple redox cycles. Transformations of the perovskite to reduced phases including brownmillerite A2Fe2O5 were identified by X-ray diffraction (XRD) as a cause of performance degradation, which was fully reversible upon air regeneration. A pre-desorption step was utilized to selectively tune the amount of lattice oxygen as a function of temperature and dwell time to enhance olefin selectivity while suppressing CO2 formation from the deep oxidation of propane. Overall, SrFeO3 exhibits promising potential for the CL-ODH of light alkanes, and optimization through surface and structural modifications may further engineer well-regulated lattice oxygen for maximizing olefin yield.

Effect of support on the deep oxidation of propane and propylene on Pt-based catalysts

The complete oxidations of propane and propylene were studied on Pt supported on CeO2, TiO2 and Al2O3. The catalyst activities were evaluated through conversion versus temperature (light-off curves) and conversion versus time tests. Propane oxidation turnover rates (TOF) followed the order: Pt/TiO2>Pt/CeO2>Pt/Al2O3. The higher activity on Pt/CeO2 than on Pt/Al2O3 was interpreted by considering that the combustion of C3H8 on Pt/CeO2 occurs not only on Pt0 sites but also on perimeter Pt0–Ce3+ sites providing an additional oxidation pathway. Propane uptake on Pt/TiO2 was 5.5times higher than on Pt/CeO2. This drastic increase of the density of adsorbed C3H8 molecules around the metallic Pt active sites would explain the high TOF values observed on Pt/TiO2 because the reaction is positive order with respect to propane. The propylene oxidation turnover rate trend was Pt/CeO2>Pt/Al2O3≅Pt/TiO2. Kinetic studies showed that on the three catalysts the apparent activation energy of propylene oxidation was about the same while the reaction orders were positive in oxygen and negative or zero in propylene. The higher activity of Pt/CeO2 catalyst was explained by considering that the Pt-catalyzed reduction of ceria forms oxygen vacancies that would improve the mobility of lattice oxygen of the support and its transfer to the propylene species adsorbed on the metal.

Selective Oxidation Performance of Propane over Supported Vanadium Oxide Catalysts

A series of SBA-15 supported vanadium oxide catalysts with different active components were prepared by the method of incipient-wet impregnation. The structures of the catalysts were characterized by N2 adsorption, X-ray diffraction (XRD), ultraviolet (UV)-Raman, Fourier transform infrared (FTIR), and ultraviolet-visble diffuse reflectance spectroscopy (UV-Vis DRS) techniques, and their catalytic performances for the selective oxidation of propane were investigated. The results showed that SBA-15 was a better support in the catalyst system than SiO2 for the selective oxidation of propane to aldehydes. The SBA-15 supported low loading catalyst is a highly dispersed catalyst system and the SBA-15 supported vanadium oxide samples with low loading (n(V)/n(Si)<2.5%) have ordered hexagonal mesostructures. For the VOx/SBA-15 catalysts, isolated vanadyl species with tetrahedral coordination are the active sites for aldehyde formation at very low loadings of vanadium (n(V)/n(Si)<0.1%). The polymeric vanadyl species with octahedral coordination and microcrystalline vanadium oxide are active sites for the oxidative dehydrogenation or deep oxidation of propane when the loading of vanadium (n(V)/n(Si)) is higher than 2.5%.

Deep oxidation of propane using palladium–titania catalysts modified by niobium

Abstract Pd/TiO 2 catalysts modified by niobium have been prepared and tested for the complete oxidation of propane. The catalysts have been characterised by BET, XRD, laser Raman spectroscopy, XPS, DRS and TPR. The incorporation of niobium into Pd/TiO 2 catalysts resulted in a marked increase in the catalytic activity compared to the Nb-free Pd/TiO 2 catalysts, and the activity increased as the niobium and/or palladium loading increased. The addition of Nb significantly modified the nature of the palladium and niobium species. There was a marked increase in the oxygen mobility after niobium addition. This could not only promote the presence of palladium species in a totally oxidized state but also resulted in the formation of new and very easily reducible species identified by subambient TPR. It was concluded that the niobium synergistic effect is due to the presence of these active oxygen species.

Deep oxidation of propane on Pt-supported catalysts: drastic turnover rate enhancement using zeolite supports

The combustion of propane was studied on Pt supported on MgO, alumina, and zeolites KL, HY, ZSM5 and Beta. Samples contained a similar amount of Pt, between 0.32 and 0.44%, and were characterized by employing a variety of physical and spectroscopic techniques. The catalyst activities were evaluated through both conversion versus temperature (light-off curves) and conversion versus time catalytic tests. Kinetic studies showed that the reaction is first order in propane, and zero (Pt/Al 2O 3, Pt/MgO) or negative (Pt/zeolites) orders in oxygen. Apparent activation energies ( E a) and pre-exponential factors ( A) were determined and it was verified that the experimental data obey a Constable relation ( ln A=mE a +c ). Pt/Al 2O 3 catalysts of different metallic dispersions were prepared for investigating the effect of Pt crystallite size on combustion activity. It was found that propane oxidation is a structure insensitive reaction on Pt/Al 2O 3. Propane oxidation turnover rates (TOF) followed the order: Pt/MgO<Pt/Al 2O 3⪡Pt/KL<Pt/HY≤Pt/ZSM5<Pt/Beta. The TOF values on Pt/acid zeolites were more than two orders of magnitude higher than on Pt/Al 2O 3. Propane oxidation activity was also significantly higher on Pt/KL as compared to Pt/Al 2O 3, despite that Al 2O 3 and zeolite KL supports exhibited similar acid sites density and strength. This result showed that the support acid strength did not have a major influence on propane combustion activity. Areal propane uptake was more than one order of magnitude higher on Pt/zeolites than on Pt/Al 2O 3 and this drastic increase in the density of propane adsorbed species may promote the alkane oxidation rate. It is proposed that the enhanced combustion activity obtained on Pt/zeolites is associated with an additional oxidation pathway from propane adsorbing on the metal-oxide interface region and reacting with oxygen spilled-over from the metal surface.

Tin-containing Systems as Catalysts for Deep Oxidation of Hydrocarbons

MO x -SnO y (M = Zn, Cu, Co, Mn, Ce) systems were studied in the reaction of deep oxidation of propane and butane.

Reaction Network and Kinetics of Propane Oxydehydrogenation over Nickel Cobalt Molybdate

Reaction kinetics and a proposed mechanism for the oxydehydrogenation of propane over Ni0.5Co0.5MoO4/SiO2are described. The reaction pathway proceeds by propane oxydehydrogenation yielding propylene as the exclusive primary product. The propylene thus formed oxidizes further primarily to acrolein, which oxides still further to waste products CO and CO2, and acrylic acid. The relative rate of acrolein formation from propylene is 3.5 times that of propylene formation from propane, the rate of COxformation from acrolein is 13 times that of acrolein formation from propylene, and the rate of COxformation from acrolein is 46 times that of propylene formation from propane. Kinetic isolation of intermediates is therefore imperative for the recovery of practical amounts of useful products, and might be achievable through dioxygen limitation in the feed or utilization of cocatalysts to produce more stable intermediates. The selective oxidation of propane to propylene and propylene to acrolein are both zero order in oxygen and first order in hydrocarbon (propane and propylene, respectively). Deep oxidation of propane (to CO and CO2) is half order in oxygen and first order in propane, while deep oxidation of propylene exhibits Langmuir type dependence on hydrocarbon and is half order in oxygen. Propane/propylene competition experiments reveal that propylene competes for the same metal oxide sites on which propane activation occurs. Their respective effectivenesses are of the same order of magnitude, with propylene being favored by a factor of 2.3 at equimolar concentration. These results are consistent with a direct pathway (i.e., surface mediated reaction) for the formation of useful products from both propane and propylene, and consecutive overoxidation of sorbed intermediates leading to deep oxidation. Kinetic isotope effects for both propane (kH/kD)C°3=1.7) and propylene ((kH/kD)C3==1.9) activation reveal methylene hydrogen abstraction and allylic hydrogen abstraction, respectively to be the rate determining steps.