Butadiene Selectivity Research Articles

Ethanol Conversion into 1,3-Butadiene by the Lebedev Method over MTaSiBEA Zeolites (M = Ag, Cu, Zn)

Tantalum-containing SiBEA zeolite with isolated framework mononuclear Ta(V) doped with Ag, Cu, and Zn was prepared and characterized by XRD, XPS, DR UV–vis, and FTIR (with pyridine, 2,6-di-tert-butylpyridine, pyrrole, and deuterated chloroform). The conversion of ethanol as a renewable raw material into 1,3-butadiene by the Lebedev method over these zeolite catalysts was investigated. The doping of TaSiBEA with Ag, Cu, and Zn changes its catalytic properties in ethanol conversion into 1,3-butadiene as a result of modification of the acid–base properties with formation of additional dehydrogenation sites. Such modification allows accelerating ethanol dehydrogenation to acetaldehyde and subsequent steps of the ethanol-to-butadiene process. Ethanol conversion and butadiene selectivity over the catalysts are increased in the order: TaSiBEA < ZnTaSiBEA < AgTaSiBEA < CuTaSiBEA. Higher selectivity to butadiene (73%) was achieved over CuTaSiBEA (at 88% ethanol conversion, T = 598 K, WHSV = 0.5 h–1).

Conversion of Ethanol and Acetaldehyde to Butadiene over MgO–SiO2 Catalysts: Effect of Reaction Parameters and Interaction between MgO and SiO2 on Catalytic Performance

For the effect of structural features on the catalytic performance of the conversion of ethanol and acetaldehyde to butadiene to be investigated, a series of MgO–SiO2 catalysts with different structural properties were synthesized by tuning the calcination temperature, investigated, and characterized. The best butadiene selectivity of 80.7% appears for the MgO–SiO2 catalyst calcined at 500 °C using a mixture of acetaldehyde/ethanol/water (22.5:67.5:10 wt %) as feed. Addition of the appropriate amount of water (10 wt %) improved butadiene selectivity by inhibiting the formation of 1-butanol and C6 compounds. Results from XRD, FT-IR, and 29Si MAS NMR indicate the generation of a significant amount of amorphous magnesium silicates along with few crystalline magnesium silicates for the catalyst calcined at 500 °C. XPS results indicate that it contains the lowest binding energies of both Si–O and Mg–O from Si–O–Mg bonds. For the catalysts calcined at low temperature (350 and 400 °C), more 1-butanol and C6 comp...

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.

Oxidative dehydrogenation of n-butane to butadiene over Bi–Ni–O/γ-alumina catalyst

Oxidative dehydrogenation of n-butane to 1,3-butadiene over Bi–Ni oxide/γ-Al2O3 catalyst was studied with fixed bed/flow-type reactor at 400–500°C. The γ-Al2O3 support itself showed activity for oxidative dehydrogenation from n-butane to n-butenes as well as partial oxidation to CO. The role of Ni oxide on γ-Al2O3 was confirmed that sole Ni oxide loading until 30wt% Ni on γ-Al2O3 resulted higher activity and selectivity to butadiene by diminishing partial oxidation related to γ-Al2O3 and enhancing conversion to butadiene. The concerted effect of Bi and Ni in Bi–Ni oxide/γ-Al2O3 catalyst was confirmed with two methods: (1) partial or full substitution of Bi for 1/3, 2/3 and 3/3 Ni of 30wt% Ni on γ-Al2O3, and (2) various amounts of Bi addition to 20wt% Ni on γ-Al2O3. As for (1) Bi substitution, 10wt% Bi-20wt% Ni showed higher activity and selectivity than the others. As for (2) Bi addition, it until Bi/Ni=0.82 (60wt% Bi-20wt% Ni) lead to suppressed CO/H2 production and improved conversion to butadiene. 30wt% Bi-20wt% Ni oxide/γ-Al2O3 catalyst showing the highest butadiene selectivity of about 47% at 450°C was used to confirm the relation between the state of oxygen and the reaction pathways by changing reaction condition factors, oxygen-to-butane ratio and temperature. It was revealed by catalyst characterization that the catalyst of Bi modified and Ni oxide highly loaded on γ-Al2O3 has high activity and selectivity for oxidative dehydrogenation of n-butane to butadiene due to either an improved Ni dispersion and redox property or a couple of weak acidity and moderate basicity.

Oxidative dehydrogenation of butane over nanocrystalline MgO, Al 2O 3, and VO x/MgO catalysts in the presence of small amounts of iodine

High surface area nanocrystalline MgO, Al 2O 3, MgO·Al 2O 3, commercial MgO, and a series of 10% V/MgO samples were used as catalysts in one-step selective oxidative dehydrogenation of butane to butadiene in the presence of oxygen and iodine. Molecular iodine shifts the equilibrium of the dehydrogenation reactions to the right and makes it possible to achieve high butane conversion with high selectivity to butadiene. When excess oxygen is present in the feed, iodine is successfully regenerated and can be recycled. Butadiene selectivity as high as 64% has been achieved in the presence of small amounts of iodine (0.25 vol%) over a vanadia–magnesia catalyst at 82% butane conversion. The best performance was observed over a catalyst containing the magnesium orthovanadate phase.

Modeling of n-Butane Oxidative Dehydrogenation in a Dual-Reactor System

Mathematical modeling of the oxidative dehydrogenation of n-butane into butadiene in a dual-reactor system with separate reactants feeding has been performed. The factors affecting the butadiene selectivity enhancement have been studied. It has been shown that it is possible to regulate the state of a catalyst in the reaction zone by varying the rate of catalyst circulation between the reactors.

The Effects of Coke Deposition on NiMoO4Used in the Oxidative Dehydrogenation of Butane

The effects of coke deposition on the NiMoO4catalyst used for oxidative dehydrogenation ofn-butane have been investigated. The coke deposition rate and the catalyst changes during this process were studied by TG, FTIR, and XRD. Coke deposition induces segregation of the NiMoO4into MoO3and NiO. It was observed that the coke elimination in He/air flow for 30 min is not complete and the catalyst recovers only partially its structure. On the other hand, it was observed that coke deposition pretreatments lead to stabilization of the NiMoO4β-phase at room temperature. If the coke is totally eliminated, the β-phase is again unstable. The expected catalyst deactivation with coke deposition was not observed. To the contrary, the conversion increases about 40% after such treatments, and the selectivity to dehydrogenation products also increases. Especially, the butadiene selectivity is more than twice higher. The increase of conversion and selectivity is ascribed to coke catalytic activity and β-phase stabilization.

Iron-Based Dehydrogenation Catalysts Supported on Zirconia. II. The Behavior in the Dehydrogenation of 1-Butene

The behavior of iron oxide-based catalysts supported on zirconia in the dehydrogenation of 1-butene was investigated. Iron oxide-on-zirconia catalysts deactivate during operation due to carbon deposition. It was shown with XRD that solid state reactions between the active phase and the support do not take place in the zirconia-supported catalysts: the iron-containing phase after reaction is Fe3O4. The total amount of carbon deposited onto zirconia-supported catalysts containing only iron oxide as determined with temperature-programmed oxidation is about 2 wt% C after 20 h. It was also shown that a carbon species deposited in narrow pores was present in iron oxide-on-zirconia catalysts. The KFe/ZrO2catalysts proved to be more stable than KFe/MgO catalysts: for catalysts containing highly dispersed iron oxide only a slight deactivation was observed after about 100 h on stream. This deactivation is attributed to migration of potassium from the catalyst to the quartz reactor. Catalysts of low loadings (1 wt% Fe, 1 wt% K) or with less well-dispersed iron oxide deactivate in a shorter period of time: an incomplete coverage of the zirconia support leads to deactivation by carbon deposition. The selectivity to butadiene of the KFe/ZrO2catalysts is about 60%, which is related to a high production of CO2. This is attributed to carbon deposition taking place in the small pores of the zirconia-supported catalysts. The coke is subsequently gasified, probably by the supported potassium carbonate. Eliminating the small pores substantially improved the butadiene selectivity.

Oxidative dehydrogenation of 1 -butene to butadiene on ?-Fe2O3/ZnAl2O4 and ZnFexAl2-xO4 catalysts

The oxidative dehydrogenation of 1-butene to butadiene was studied over a series of catalysts of iron impregnated on ZnAl2O4 used as a support and also Fe coprecipitated with zinc and aluminum in order to obtain ZnFexAl2-xO4 type catalysts. Results were compared with bulk α-Fe2O3, ZnAl2O4 and ZnFe2O4. X-ray diffraction (XRD) and Mossbauer spectroscopy suggest that in the impregnated catalysts, Fe ions are in strong interaction with the support. These samples have higher butadiene selectivity than coprecipitated ZnFexAl2-xO4 catalysts, in which iron is incorporated into the ZnAl2O4 spinel network. Results suggest also that iron content has a greater effect on butadiene selectivity than the zinc aluminate-iron oxide interaction.

Oxidative dehydrogenation of n-butane on zinc-chromium ferrite catalysts

The role of chromium as a promoter of butadiene selectivity in n-butane oxidative dehydrogenation on ZnCr x Fe 2- x O 4 (0< x<1.09) catalysts was studied. Catalysts have a spinel structure with Cr 3+ replacing Fe 3+ in octahedral sites. Mössbauer spectroscopy studies showed that the substitution of iron by chromium modifies the electron density of the iron nuclei in the ZnFe 2O 4 structure. Iron nuclei showed the lowest electron density for x=0.5–0.6, hence the electron density of oxygen in FeO bond has to be enhanced. n-Butane oxidative dehydrogenation also showed a maximum in butadiene selectivity at x=0.5–0.6. These results suggest that chromium increases butadiene and CO 2 selectivities, with simultaneous decrease of butenes and cracking products explained by an enhancement of the lattice oxygen basicity, which promotes the acid-base type dissociation of the CH bond during butene activation.

Steady state and transient behavior in 1‐butene reactions over bismuth molybdate

AbstractPulse and continuous flow techniques were used to study 1‐butene reactions in the presence of oxygen over bismuth molybdate.At 280°C and low 1‐butene partial pressures (2.1‐5.6 kPa), the activity increases with the pulse number and tends towards a constant level. At high 1‐butene partial pressures (40‐68 kPa), the activity decreases at the same conditions but tends also to stabilize. The butadiene selectivity increases and 2‐butene selectivities decrease in both cases and tend towards the selectivities observed with a continuous flow technique in steady state conditions.At 350°C, the activity has a similar behavior for low pressures of 1‐butene, but for high pressures increasing activity occurs. For such a temperature the oxidative dehydrogenation selectivity decreases and the isomerization selectivities increase with respect to the pulse number, but tend also towards the values found in steady state flow operation.Experiments at intermediate temperatures (300 and 320°C) show a coherent evolution. On other side, experimental results obtained using only 1‐butene as reactant in the absence of oxygen contributed greatly to clarification of the observed situation.The results are discussed and interpreted in the context of the reaction mechanism.

Catalytic Oxidative Dehydrogenation of Hydrocarbons (Part 1)

The oxidative dehydrogenation reaction of n-butene to butadiene over Bi-Mo, Bi oxide and Mo oxide catalysts in a flow system at atmospheric pressure has been investigated.High butadiene yield were obtained over Bi-Mo coprecipitation catalyst at 400∼500°C in excess of oxygen, but higher oxygen content lowered the butadiene selectivity with increase in CO and CO2 formation.The order of oxidative dehydrogenation over the investigated catalysts can be shown as follows, Bi-Mo(coprecipitation)>Bi2O3+MoO3(dry mixing)>MoO2.76>MoO3>Bi2O3_??_Silica chip.When oxidation reaction of hydrogen compared with oxidative dehydrogenation of n-butene at the same conditions, it was assumed that oxidative dehydrogenation over Bi-Mo and MoO3 catalysts was not dehydrogenation followed by oxidation of hydrogen.Oxidation reaction of n-butene over Bi2O3 catalyst may undergo in different mechanism from oxidative dehydrogenation over Bi-Mo catalyst.