Dehydrogenation Of Butane Research Articles

Selective Synthesis of 1,3-Butadiene through <i>n</i>-Butane Dehydrogenation over Metal-containing Zeolite Catalyst

Selective Synthesis of 1,3-Butadiene through <i>n</i>-Butane Dehydrogenation over Metal-containing Zeolite Catalyst

N-Butane dehydrogenation over Ni-Sn/SiO2: Adsorption modes and reaction paths of n-butane and 1-butene

Compared with i-butane dehydrogenation over Ni-Sn/SiO2 catalyst, the conversion is higher for n-butane dehydrogenation, the selectivity to butenes is obviously lower, and the catalyst deactivates more rapidly. In order to clarify the difference, adsorption modes of n-butane and 1-butene along with desorption activation energy of 1-butene were determined by in-situ FTIR and TPD. n-Butane is adsorbed on Ni-Sn surface with a H atom in methyl, and the formed intermediates are prone to the rupture of CC bonds, leading to the lower selectivity to butenes. In addition, secondary reactions of butenes also play an important role in decreased selectivity, but to a less extent due to the medium desorption activation of butenes (58 kJ mol−1 for 1-butene, for example). The generation of coke is the third reason for lower selectivity. The rapid deactivation of Ni-Sn/SiO2 catalyst mainly results from the formation of 1,3-butadiene, coke precursor, by further dehydrogenation of butenes.

Continuous-Flow Alkane Dehydrogenation by Supported Pincer-Ligated Iridium Catalysts at Elevated Temperatures

Pincer-ligated iridium complexes of the form [Ir(R4PCP)L] (R4PCP = κ3-C6H3-2,6-(XPR2)2; X = CH2, O; R = tBu, iPr) are efficient homogeneous alkane dehydrogenation catalysts that have been reported to be highly active at temperatures of 240 °C or below. In this work, silica-supported [Ir(C2H4)(p-tBu2PO-tBu4POCOP)] (1/SiO2) was used to study a model continuous-flow gas-phase acceptorless alkane dehydrogenation system. This particular supported framework is thermally stable at temperatures up to 340 °C, 100 °C above the highest temperature at which analogous homogeneous complexes have been reported to show stable activity, with observed butane dehydrogenation rates of ca. 80 molbutenes molcat.–1 h–1. Solid-state 31P MAS NMR and ATR IR are used to demonstrate that the backbone pincer ligand remains intact and coordinated at 340 °C. The complex is fully converted to [Ir(CO)(p-tBu2PO-tBu4POCOP)] (3/SiO2) above 300 °C. 3/SiO2 is observed to be catalytically active at the higher temperatures tested, and reaction ...

Effect of Excess Iron on Oxidative Dehydrogenation of 1-Butene over a Series of Zinc Ferrite Catalysts

The influence of excess Fe3+ in ZnFe2O4 for the catalytic oxidative dehydrogenation of 1-butene to 1, 3-butadiene was investigated to try to clarify inconsistencies in the existing literature. A series of nanoscale zinc ferrite powders were produced with increasing Fe: Zn ratios. The materials were characterized by a range of techniques, which showed the presence of α-Fe2O3 as a distinct phase with an increasing excess of Fe3+ and SEM highlighted the increased presence of surface structures on the ferrites at higher Fe: Zn ratios. Reaction testing showed α-Fe2O3to be virtually inactive for the oxidative dehydrogenation of 1-butene. Results for the ferrite catalysts showed a significant decrease in both conversion and yield with an increasing excess of Fe3+. Therefore an excess of Fe3+ has a negative effect on catalytic activity and selectivity of zinc ferrite for the oxidative dehydrogenation of 1-butene, but acts as a promoter for competing hydrogenation and combustion side reactions.

Catalytic Transformations of 1-Butene over Palladium. A Combined Experimental and Theoretical Study

Applying a density functional approach to slab models of planar, (111), and rough, (110), Pd surfaces, we determined the isomerization free energy barriers of 1-butene to be significantly lower than the hydrogenation barriers. Microkinetic modeling allows one to mirror the kinetic experiments on conversions of 1-butene at the corresponding single-crystal surfaces in a qualitative fashion. Despite the inherent limitations of such kinetic modeling, theoretical predictions are fully supported by experimental data using Pd model catalysts: i.e., Pd(111) and Pd(110) surfaces. The isomerization mechanism was calculated to proceed via an initial dehydrogenation of 1-butene to 1-buten-3-yl as an intermediate—in contrast to the commonly proposed 2-butyl intermediate, associated with the Horiuti–Polanyi mechanism. Our modeling results rule out the original assumption that isomerization has to start with a hydrogenation step to rationalize the dependence of isomerization on hydrogen. However, this hydrogen dependenc...

Oxidative Dehydrogenation of 1-Butene to 1,3-Butadiene Using CO2 over Cr-SiO2 Catalysts Prepared by Sol-gel Method

series of Cr-SiO2 catalysts with a Cr content(mass fraction) ranging from 0.5% to 9% was prepared by a sol-gel method. The catalysts were characterized by XRD, N2 adsorption, EDX elemental mapping, Raman spectroscopy, UV-Vis spectroscopy, XPS and H2-TPR, and their catalytic behavior in the dehydrogenation of 1-butene to 1,3-butadiene(BD) using CO2 as a soft oxidant was studied. The initial BD yield is well correlated with the amount of Cr6+ in the fresh catalysts. The highest BD yield of ca. 34% is achieved on the catalysts with 5%―9% Cr at 600 °C and weight hourly space velocity(WHSV) of 4.5 g·g cat -1 ·h-1. The promoting effect of CO2 on the BD yield was observed, which can be attributed to the reaction coupling between a simple dehydrogenation of 1-butene and the reverse water-gas shift reaction as well as regaining the oxidation state(lattice oxygen) of reduced Cr3+ species due to the mild oxidation ability of CO2. The Cr-SiO2 catalyst exhibits higher BD yield than the Cr catalyst supported on SBA-15, which is attributed to the higher amount of Cr6+present on the former catalyst.

Preparation of Foam Structured Catalyst ZnFe2O4-α-Fe2O3/SiC and its Performance in Oxidative Dehydrogenation of Butene

Preparation of Foam Structured Catalyst ZnFe2O4-α-Fe2O3/SiC and its Performance in Oxidative Dehydrogenation of Butene

Gas-solid catalytic dehydrogenation of propane and butanes to olefins

Catalytic dehydrogenation is an effective route to convert light alkanes to monoolefins with the same carbon number and H2. In this paper the research progress in the reaction mechanism, catalyst and reactor for propane/butane dehydrogenation in recent years has been introduced. Catalytic dehydrogenation of alkanes is a strong endothermic reaction and its conversion for single pass is limited by the thermodynamic equilibrium. Both the reaction and the product separation consume a large amount of energy. Improving the conversion of alkanes for single pass by optimizing the operating conditions, on the basis of guaranteeing the high selectivity to olefins and the long-term safety and stability of the unit operation, is the key to reduce energy consumption for the whole process. During the dehydrogenation of alkanes, two H atoms bonded with two adjacent C atoms adsorb on the same active site, and the active site draws the two H atoms closer to attract each other, leading to the scission of C–H bonds to form H2 and olefins. The olefins enter to the gas phase directly without adsorption. The widely used supported Pt and CrO x catalysts have been introduced systematically, including the preparation methods, existing state of active components, carriers, additives, deactivation and regeneration, as well as problems encountered in application. At the same time, the newly reported catalysts, such as supported metal catalysts (Ni, NiSn and Sn), metal oxide catalysts (Ga2O3/ZnO and ZnO/Nb2O5), other mixed metal oxides and/or composite metal oxides catalysts, as well as metal sulfide catalysts have also been discussed briefly. Furthermore, the performances of packed-bed, moving-bed and circulating fluidized-bed reactors have been analyzed comparatively. The circulating fluidized-bed reactor is optimal due to its continuous reaction and catalyst regeneration and the efficient heat supplying for the endothermic dehydrogenation by high-temperature regenerated catalyst. The ADHO process, based on environment-friendly metal oxide catalyst coupled with cocurrent circulating fluidized-bed reactor, offers a novel high-efficiency and low-consumption dehydrogenation technology for the chemical industry.

Lanthanum-mediated dehydrogenation of butenes: Spectroscopy and formation of La(C4H6) isomers.

La atom reactions with 1-butene, 2-butene, and isobutene are carried out in a laser-vaporization molecular beam source. The three reactions yield the same La-hydrocarbon products from the dehydrogenation and carbon-carbon bond cleavage and coupling of the butenes. The dehydrogenated species La(C4H6) is the major product, which is characterized with mass-analyzed threshold ionization (MATI) spectroscopy and quantum chemical computations. The MATI spectrum of La(C4H6) produced from the La+1-butene reaction exhibits two band systems, whereas the MATI spectra produced from the La+2-butene and isobutene reactions display only a single band system. Each of these spectra shows a strong origin band and several vibrational progressions. The two band systems from the spectrum of the 1-butene reaction are assigned to the ionization of two isomers: La[C(CH2)3] (Iso A) and La(CH2CHCHCH2) (Iso B), and the single band system from the spectra of the 2-butene and isobutene reactions is attributed to Iso B and Iso A, respectively. The ground electronic states are 2A1 (C3v) for Iso A and 2A' (Cs) for Iso B. The ionization of the doublet state of each isomer removes a La 6s-based electron and leads to the 1A1 ion of Iso A and the 1A' ion of Iso B. The formation of both isomers consists of La addition to the C=C double bond, La insertion into two C(sp3)-H bonds, and H2 elimination. In addition to these steps, the formation of Iso A from the La+1-butene reaction may involve the isomerization of 1-butene to isobutene prior to the C-H bond activation, whereas the formation of Iso B from the La+trans-2-butene reaction may include the trans- to cis-butene isomerization after the C-H bond activation.

Dehydrogenation of n-Butane to Butenes and 1,3-Butadiene over PtAg/Al<sub>2</sub>O<sub>3</sub> Catalysts in the Presence of H<sub>2</sub>

The Al2O3-supported PtAg catalysts were prepared and evaluated for the dehydrogenation of n-butane at 550°C in the presence of H2. The PtAg/Al2O3 catalyst prepared by an impregnation method using the Cl- removing Pt/Al2O3 and AgNO3 showed a higher activity and selectivity to butenes and 1,3-butadiene compared to the Pt/Al2O3 catalyst, but a large amount of coke (about 30 wt% versus the catalyst weight) was formed during the dehydrogenation. The free Ag metal on the prepared catalyst dramatically promoted the coke formation, because the dehydrogenation of 1-butene over the Ag/Al2O3 catalyst produced a large amount of coke. The Cl- addition to the Cl- free Pt/Al2O3 catalyst decreased the coke formation by the reaction of the free Ag particles and Cl to form AgCl which was inactive for the coke formation. The highest initial conversion (50.3%) was obtained with the selectivity to butenes and 1,3-butadiene (butenes = 80.2% and 1,3-butadiene = 5.9%) when the PtAg/Al2O3 catalyst modified with Cl- was used.

Synthesis of spherical structured catalysts by dip‐coating: Application to n‐butane dehydrogenation

AbstractThis work analyzes the deposition conditions of thin layers of γ‐Al2O3 by dip‐coating on a spherical substrate of α‐Al2O3 spheres. Results showed that under controlled deposition conditions, a structured support of α‐Al2O3 spheres coated by a uniform γ‐Al2O3 layer (thickness ≈ 15 µm) of good adherence can be attained. Optimal preparation conditions for the coating, that involved pretreatment of the substrate, gel formation, deposition conditions, and thermal treatments, were obtained. Pt catalysts supported on this structured material can be used as promising dehydrogenation systems. In this sense, a monometallic structured catalyst showed both good metallic dispersion and catalytic performance in n‐butane dehydrogenation reaction compared to another conventional catalytic system.

Business Roundup

BUSINESS Business Roundup ShareShare onFacebookTwitterWechatLinked InRedditEmail C&EN, 2017, 95 (36), p 13September 11, 2017Cite this:C&EN 95, 36, 13AbstractAir Liquide has licensed a Mitsubishi Chemical process for producing butadiene by butene dehydrogenation. Air Liquide, which supplies butadiene technologies to other firms, notes that the Mitsubishi process allows butadiene to be made at chemical complexes that use feedstocks other than naphtha. Yuhuang Chemical has awarded Amec Foster Wheeler a $604 million contract to help build its planned methanol plant in St. James Parish, La. The $1.85 billion plant will be the largest grassroots Chinese chemical investment on the U.S. Gulf Coast. Reliance Industries will acquire Kemrock Industries, an Indian producer of carbon fiber composites. Reliance, also of India, says the purchase will mark its entry into the composites business. Clariant will make a low single-digit million-dollar investment in its oil services sites in Midland, Texas, and Clinton, Okla., The investment will be completed by the end of the year and includes new or expanded technical labs at both locations.View: PDF | Full Text HTML

Integrating Visualization Methods with Chemical Kinetics Model Solution and Editing Tools

We developed a set of tools for visualizing, analyzing, and editing reaction networks. Three conceptual elements were covered. In the first, the reaction network was rendered in terms of species–species and species–reaction tree plots. This provided for a visual inspection of the connectivity of components in a reaction network and the paths from reactants to products. More quantitative information was provided by the second element, which represented the quantitative concentration of the composition as it evolved from reactants to products. This allowed the modeler to examine the quantitative flows of mass though the reaction network and expose flaws for editing. The third element involved a coupling of the tree visualization and model solution tools that allowed for the elimination of reactions and rebuilding of the reaction network from the visualization interface. These tools are illustrated using the production of butadiene through catalytic oxidative dehydrogenation of butane as an example.

Catalytic oxidative dehydrogenation of 1-butene to 1,3-butadiene with CO2 over Fe2O3/γ-Al2O3 catalysts: the effect of acid or alkali modification

Fe2O3/γ-Al2O3 catalysts were modified by acid and alkali (H2SO4, LiOH, NaOH and KOH) and were investigated for 1,3-butadiene (BD) synthesis through the oxidative dehydrogenation of 1-butene with CO2. Nitrogen sorption and XRD results revealed that physical and original crystalline structure of Fe2O3/γ-Al2O3 catalysts remained intact after the modification. The acidity and alkalinity of the catalysts were determined quantitatively and qualitatively by NH3-TPD and CO2-TPD, respectively. The sequence of catalyst activity for these five catalysts was: Li–Fe2O3/γ-Al2O3 > S–Fe2O3/γ-Al2O3 > Fe2O3/γ-Al2O3 > K–Fe2O3/γ-Al2O3 > Na–Fe2O3/γ-Al2O3. The catalytic activity (BD rate) of Fe2O3/γ-Al2O3 catalysts was improved ~41% after the modification of LiOH. Results indicated that too little amount of acid sites as well as the strong basic sites over catalyst surface were not facilitate to the formation of BD. TG characterization results illustrated that the coke resistant ability of the catalysts was enhanced with the catalyst alkalinity.

Effect of oxygen adsorption on the electrical conductivity of semiconducting nickel–iron oxide catalyst with spinel structure

Nickel–iron oxide catalyst semiconductor with spinel structure is synthesized from oxalates. Oxygen adsorption and its effect on the catalyst’s electrical conductivity in the temperature range of 353–693 K and the ferromagnetic state are studied. The presence of durable and reversible form of adsorbed oxygen is detected. It is established that the resistivity of samples and their activation energy depend on the type of adsorption and the temperature. Strongly adsorbed atomic oxygen is charged negatively and can participate in the reaction of oxidative dehydrogenation of butene-1.

Adsorption and dehydrogenation of ethane, propane and butane on Rh13 clusters supported on unzipped graphene oxide and TiO2(110) - a DFT study.

The catalytic activity for the adsorption and dehydrogenation of alkanes (CnH2n+2, n = 2, 3, 4) on a low-symmetry Rh13 cluster (Rh13-Ls) is compared with a system consisting of the same cluster (Rh13-Ls) supported on either an unzipped graphene-oxide (UGO) sheet (Rh13-Ls/UGO) or a TiO2(110) surface (Rh13-Ls/TiO2). The adsorption energies of these alkanes, calculated using density-functional theory, follow the order Rh13-Ls/TiO2 ≈ Rh13-Ls/UGO > Rh13-Ls. Our proposed reaction path for the dehydrogenation of ethane, propane and butane on Rh13-Ls/UGO has first barrier heights of 0.21, 0.22 and 0.16 eV for the dissociation of a terminal C-H bond to form -C2H5, -C3H7 and -C4H9, respectively. Compared with the barriers on Rh13-Ls and Rh13-Ls/TiO2, the barrier on Rh13-Ls/UGO is the lowest for all alkanes. The calculated data, including the electronic distribution and the density of states of alkanes adsorbed on Rh13-Ls/UGO, Rh13-Ls and Rh13-Ls/TiO2, to support our results are presented.

Solid-state molecular organometallic chemistry. Single-crystal to single-crystal reactivity and catalysis with light hydrocarbon substrates.

Single-crystal to single-crystal solid/gas reactivity and catalysis starting from the precursor sigma-alkane complex [Rh(Cy2PCH2CH2PCy2)(η2η2-NBA)][BArF 4] (NBA = norbornane; ArF = 3,5-(CF3)2C6H3) is reported. By adding ethene, propene and 1-butene to this precursor in solid/gas reactions the resulting alkene complexes [Rh(Cy2PCH2CH2PCy2)(alkene) x ][BArF 4] are formed. The ethene (x = 2) complex, [Rh(Cy2PCH2CH2PCy2)(ethene)2][BArF 4]-Oct, has been characterized in the solid-state (single-crystal X-ray diffraction) and by solution and solid-state NMR spectroscopy. Rapid, low temperature recrystallization using solution methods results in a different crystalline modification, [Rh(Cy2PCH2CH2PCy2)(ethene)2][BArF 4]-Hex, that has a hexagonal microporous structure (P6322). The propene complex (x = 1) [Rh(Cy2PCH2CH2PCy2)(propene)][BArF 4] is characterized as having a π-bound alkene with a supporting γ-agostic Rh···H3C interaction at low temperature by single-crystal X-ray diffraction, variable temperature solution and solid-state NMR spectroscopy, as well as periodic density functional theory (DFT) calculations. A fluxional process occurs in both the solid-state and solution that is proposed to proceed via a tautomeric allyl-hydride. Gas/solid catalytic isomerization of d3-propene, H2C[double bond, length as m-dash]CHCD3, using [Rh(Cy2PCH2CH2PCy2)(η2η2-NBA)][BArF 4] scrambles the D-label into all possible positions of the propene, as shown by isotopic perturbation of equilibrium measurements for the agostic interaction. Periodic DFT calculations show a low barrier to H/D exchange (10.9 kcal mol-1, PBE-D3 level), and GIPAW chemical shift calculations guide the assignment of the experimental data. When synthesized using solution routes a bis-propene complex, [Rh(Cy2PCH2CH2PCy2)(propene)2][BArF 4], is formed. [Rh(Cy2PCH2CH2PCy2)(butene)][BArF 4] (x = 1) is characterized as having 2-butene bound as the cis-isomer and a single Rh···H3C agostic interaction. In the solid-state two low-energy fluxional processes are proposed. The first is a simple libration of the 2-butene that exchanges the agostic interaction, and the second is a butene isomerization process that proceeds via an allyl-hydride intermediate with a low computed barrier of 14.5 kcal mol-1. [Rh(Cy2PCH2CH2PCy2)(η2η2-NBA)][BArF 4] and the polymorphs of [Rh(Cy2PCH2CH2PCy2)(ethene)2][BArF 4] are shown to be effective in solid-state molecular organometallic catalysis (SMOM-Cat) for the isomerization of 1-butene to a mixture of cis- and trans-2-butene at 298 K and 1 atm, and studies suggest that catalysis is likely dominated by surface-active species. [Rh(Cy2PCH2CH2PCy2)(η2η2-NBA)][BArF 4] is also shown to catalyze the transfer dehydrogenation of butane to 2-butene at 298 K using ethene as the sacrificial acceptor.

Temperature-induced deactivation mechanism of ZnFe2O4 for oxidative dehydrogenation of 1-butene

This paper describes the observation of an irregular decrease in 1-butene conversion during oxidative dehydrogenation over ZnFe2O4 in the production of 1,3-butadiene upon increasing the reaction temperature above 400 °C.

Catalyst Deactivation of a Silica-Supported Bismuth–Molybdenum Complex Oxide and the Related Complex Oxides for the Oxidative Dehydrogenation of 1-Butene to 1,3-Butadiene

This study was an examination of the catalyst deactivation of a silica-supported bismuth-molybdenum complex oxide, and that of catalysts used in the absence of bismuth, for the oxidative dehydrogenation of 1-butene. Due to the detection of deactivation, the molar ratio of 1-butene against oxygen in the reactant gas was adjusted to a ratio similar to that used in industrial processes where reaction temperatures average 100 K higher. Regardless of the presence or absence of bismuth in the catalysts, the conversion of 1-butene was decreased by 6 h on-stream. Both the progress of the coking from the inlet to the outlet of the catalyst and the reduction of molybdenum in the catalysts directly contributed to the deactivation. X-ray photoelectron spectrometry revealed that a greater reduction of molybdenum in the near-surface region and a smaller partial pressure of oxygen (P(O2)) in the reactant gas, although the molybdenum on the surface was not reduced at all. This indicated that the lattice oxygen was pumped from the near-surface region to the surface during the reaction and the oxygen-poor conditions of the near-surface region both in the gas and catalyst phases were formed at a smaller P(O2), which resulted in the enhancements of both the reduction of molybdenum and that of coking. Based on the thermogravimetric analysis, the silica-supported bismuth-molybdenum complex oxide used at P(O2) = 4.1 kPa (color of the catalyst = black) was increased in weight while that used at P(O2) = 16.4 kPa (color of the catalyst = gray) showed a weight decrease, which indicated that the weight decrease caused by the reduction in molybdenum in the near-surface region used at 4.1 kPa was greater than the weight increase from the coking. It was concluded that the reduction in molybdenum followed by the coking on the catalyst surface were the main factors in the catalyst deactivation.

Oxidative Dehydrogenation of 1-Butene to 1,3-Butadiene over a Multicomponent Bismuth Molybdate Catalyst: Influence of C3–C4 Hydrocarbons

The influence of light hydrocarbons, such as n-butane, isobutane, propylene, cis- and trans-2-butenes, and isobutene on the oxidative dehydrogenation of 1-butene to 1,3-butadiene over BiMoKNiCoFePOx/SiO2 catalyst has been studied using a gas flow reactor. The inhibition effect of the listed hydrocarbons on the target reaction increased in the order of n-butane ~ isobutane < propylene < 2-butenes < isobutene. In addition, in contrast to 1-butene, isobutene has shown significant contribution to coke formation. It was suggested, that the coke formation and therefore the rate of the catalyst regeneration exercise a significant influence on the efficiency of 1-butene transformation into 1,3-butadiene in the concurrent presence of other hydrocarbons.