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Designing zeolite catalysts with improved mass transport properties is crucial for restrictive networks of either one‐ or two‐dimensional pore topologies. Here, we demonstrate the synthesis of finned ferrierite (FER), a commercial zeolite with two‐dimensional pores, where protrusions on crystal surfaces behave as pseudo nanoparticles. Catalytic tests of 1‐butene isomerization reveal a 3‐fold enhancement of catalyst lifetime and an increase of 12 % selectivity to isobutene for finned samples compared to corresponding seeds. Electron tomography was used to confirm the identical crystallographic registry of fins and seeds. Time‐resolved titration of Brønsted acid sites confirmed the improved mass transport properties of finned ferrierite compared to conventional analogues. These findings highlight the advantages of introducing fins through facile and tunable post‐synthesis modification to impart material properties that are otherwise unattainable by conventional synthesis methods. [ABSTRACT FROM AUTHOR]

1,3-BD production process from lignin consisting of four unit operations such as gasification, dimethyl ether (DME) synthesis, n -butene synthesis, and isomerization/dehydrogenation, was simulated. This process could be designed as a renewable energy system that can not only produce 1,3-BD but also self-supply almost all the heat and power for the operation. The balance of payment (BP), which is the income incurred from processing a unit weight of lignin, was employed as the economic efficiency of the process. The effect of the reaction conditions in the DME to n -butene synthesis step (the third step) on the BP was investigated. Since few catalysts have been reported for synthesizing n -butene from DME, realistic reaction conditions and catalytic performance were set. An increase in the DME content of the feed gas and a decrease in the reaction pressure led to an increase in the n -butene yield and a decrease in the power, followed by an increase in the 1,3-BD yield and BP. Considering the expected power selling price after the termination of the Feed-in-Tariff scheme, the 1,3-BD production process could have comparable BPs with gasification power generation as a representative competitive process. Image 1 • n -Butene synthesis from dimethyl ether was simulated. • The total 1,3-butadiene production process from lignin was simulated. • The 1,3-butadiene production process was improved based on the balance of payment. • A reduction in the power selling price led to the breakeven point. • A high DME content and atmospheric pressure are desirable for n -butene synthesis. [ABSTRACT FROM AUTHOR]

Conversion of 1-butene was studied over Mo carbides and Ni, Co and Mo phosphides, under continuous gas phase operating conditions at atmospheric pressure and 100 °C, using 1-butene/helium mixture in a molar ratio of 4:1. The conversion was in the range 30–44% and the values were quite stable except for (1:2)CoP, (1:2)NiP, (1:2)MoP-and Mo x C supported catalysts. The main reaction was isomerization of 1-butene, and the selectivity to dimerization was observed in a higher ratio on (1:2)MoP and Mo x C supported on high surface area graphite. In situ XRD, XPS, NH 3 -TPD and thermogravimetry (TG) have been used to assess for the formed species on the surface. [Display omitted] • Conversion of 1-butene over Mo phosphides and carbides on carbon-based catalysts. • Stable catalysts on isomerization reaction. • MoP enhanced the selectivity to dimerization. [ABSTRACT FROM AUTHOR]

A two-step process was demonstrated for the conversion of 1-butene to n-nonanal with an overall reaction selectivity of 70.8%. The process consists of a dimerization step over a heterogeneous carbon-supported cobalt oxide catalyst to a mixture of oligomers, consisting primarily of internal linear octenes. After product distillation, the olefinic mixture was converted to C 9 aldehydes with a normal/isomeric (N/I) ratio of 3.8 over a homogeneous Rh/BIPHEPHOS catalyst. This work demonstrates a new route to produce linear aldehydes from light olefins. [ABSTRACT FROM AUTHOR]

Hydrothermal modification of the alumina catalyst of n-butenes skeletal isomerization was investigated. It is shown that during the hydrothermal treatment of γ-Al 2 O 3 and subsequent calcination its activity in skeletal isomerization of n-butenes first increases, and then it decreases with a rise of the hydrothermal treatment duration. This behavior is due to a similar change in the content of the strong Lewis acid sites of alumina, which are the active centers of reaction and they can be identified by IR-spectroscopy of the adsorbed pyridine and EPR-spectroscopy of the adsorbed anthraquinone. We report the mechanism of new Lewis acid sites formation at the γ-Al 2 O 3 hydrothermal treatment containing X-ray amorphous component. [ABSTRACT FROM AUTHOR]

[Display omitted] • Effect of acid strength on butene isomerization mechanisms was studied. • Relationship among acid strength, type of butene, and alkylate quality was clarified. • Stability of butyl cations follows the order: tert -cation > cis -cation > trans -cation. • 1-butene and 2-butene as reactant have similar alkylation activity on strong acids. • Skeleton isomerization is more difficult to occur than the other two isomerization. Understanding the effect of acid strength on butene isomerization mechanisms is essential in C4 alkylation process. Herein, the double bond, trans-cis, and skeleton isomerization mechanisms of butene over acid sites with different acid strengths were investigated utilizing density functional theory (DFT) calculations. It is demonstrated that the acid strength significantly affects the isomerization mechanisms of butene. The stability of carbonium ions as reaction intermediates follows the order: tert -butyl cation > cis -butyl cation > trans -butyl cation, which is more sensitive to acid strength than that of butoxide species. Therefore, the reaction pathways of double bond and trans-cis isomerizations changed with varying the acid strength. Based on the analysis of activation energy barriers, it is found that 1-butene and 2-butene can be easily converted into each other over strong acid site. Thus, for reactants, C4 alkylation has no selectivity to 1-butene and 2-butene over strong acid site, which is consistent with experimental study. This work provides mechanistic insights into the relationship among acid strength, type of butene, and quality of alkylate in the C4 alkylation process. [ABSTRACT FROM AUTHOR]

Iso-butene is an important material for the production of chemicals and polymers. It can take part in various chemical reactions, such as hydrogenation, oxidation and other additions owing to the presence of a reactive double bond. It is usually obtained as a by-product of a petroleum refinery, by Fluidized Catalytic Cracking (FCC) of naphtha or gas-oil. However, an interesting alternative to iso-butene production is n-butane dehydroisomerization, which allows the direct conversion of n-butane via dehydrogenation and successive isomerization. In this work, a simulation analysis of an integrated membrane system is proposed for the production and recovery of butenes. The dehydroisomerization of n-butane to iso-butene takes place in a membrane reactor where the hydrogen is removed from the reaction side with a Pd/Ag alloys membrane. Afterwards, the retentate and permeate post-processing is performed in membrane separation units for butenes concentration and recovery. Four different process schemes are developed. The performance of each membrane unit is analyzed by appropriately developed performance maps, to identify the operating conditions windows and the membrane permeation properties required to maximize the recovery of the iso-butene produced. An analysis of integrated systems showed a yield of butenes higher than the other reaction products with high butenes recovery in the gas separation section, with values of molar concentration between 75% and 80%. [ABSTRACT FROM AUTHOR]

The traditional reaction temperatures of 1-butene isomerization to 2-butene tend to above 100 °C, while here we report the unique catalytic performance of a Pd loaded silica nanospheres catalyst for 1-butene double-bond-shift isomerization at room temperature and showed 2-butene yield of 37.0%. Furthermore, the introduction of O 2 into the reaction mixture dramatically improved the yield efficiency to 57.2% without the formation of by-product CO 2 . The reaction process is proved that the ratio of trans -2-butene to cis -2-butene in the final product was determined by the trans : cis ratio of the butenylcarbenium ion intermediate, and the ratio of trans -2-butene to cis -2-butene decreased with the increasing reaction temperature. Unlike other palladium catalyst systems, Pd 0 nanoparticles were proved to act as catalytic active sites, and their oxidation and aggregation resulted in a decrease in activity. Most importantly, the catalyst acidity affected the catalytic performance, which provides theoretical basis for the choice of catalysts. [ABSTRACT FROM AUTHOR]

The rapid increase in the demand for propylene and its derivatives requires urgently developing propylene-producing technology. To better understand the complicated reactions on W-based metathesis catalyst for propylene production and further to clarify the involved reaction mechanism, thermodynamic calculation was first performed to analyze the gas mixture under different conditions theoretically. The analyzed reaction system is close to the ideal gas under typical reaction conditions. The detailed investigation of reactions under different conditions was then carried out using WO 3 /SiO 2 and MgO catalysts in a fixed-bed tubular micro reactor. Experimental results together with calculation demonstrate that temperature plays the most important role in regulating metathesis reaction compared with other factors such as pressure, ethylene content and weight hourly space velocity (WHSV). Also, ethylene content in the feedstock affects a lot on metathesis process. With an optimized ratio of ethylene/ n -butene, cross-metathesis of 2-butene and ethylene is more likely to take place than that of 1-butene and 2-butene, and trans -2-butene has a generally better activity to react with ethylene than cis -2-butene due to the steric effect. On the other hand, isomerization is more independent on temperature compared with metathesis reaction. The consumption of 2-butene in metathesis will promote isomerization of 1-butene to 2-butene. Some extreme conditions such as higher pressures, larger ethylene contents and lower temperatures will provide opportunities for polymerization of ethylene. Based on the reaction analysis under different conditions, the reaction routes are summarized and a supposing mechanism for the formation of metallacyclobutane intermediate from trans / cis -2-butene is proposed. [ABSTRACT FROM AUTHOR]

We have investigated the effect of acid site density on the catalytic performance of high-silica (50 ⩽ Si/Al ⩽ 380) H-HPM-1 zeolite in the 1-butene skeletal isomerization. Changes (⩽ 0.5) in the number of framework Al atoms, and thus of Brønsted acid sites, per unit cell (60 tetrahedral atoms) led to striking variations in both 1-butene conversion and isobutene selectivity. Combining isobutene yield with catalyst durability, H-HPM-1 with a framework Si/Al ratio of 350 was found to perform better than any of the catalysts studied for this reaction thus far. [ABSTRACT FROM AUTHOR]

We respond to the two questions posed by Weinhold, Schleyer, and McKee (WSM) in their study of cis-2-butene (Weinhold et al., J Comput Chem 2014, 35, 1499), in which they solicit explanations for the relative conformational energies of this molecule in terms of the Quantum Theory of Atoms in Molecules (QTAIM). WSM requested answers to the questions: (1) why is cis-2-butene less stable than trans-2-butene despite the presence of a hydrogen-hydrogen (H⋯H) bond path in the former but not in the latter if the H⋯H bond path is stabilizing? (2) Why is the potential well of the conformational global minimum of cis-2-butene only 0.8 kcal/mol deep when the H⋯H bonding is stabilizing by 5 kcal/mol? Both questions raised by WSM are answered by considering the changes in the energies of all atoms as a function of the rotation of one of the two methyl groups from the minimum-energy structure, which exhibits the H ⋯H bond path, to the transition state, which is devoid of this bond path. It is found that the stability gained by the H⋯H bonding interaction is cancelled by the destabilization of one of the ethylenic carbon atoms which, alone, destabilizes the system by as much as 5 kcal/mol in the global minimum conformation. Further, it is found that the 1.1 kcal/mol stability of trans-2-butene with respect to the cis-isomer is driven by the considerable destabilization of the ethylenic carbons by 11 kcal/mol, while the changes in the atomic energies of the other corresponding atoms in the two isomers account for the observed different stabilities. The error introduced into QTAIM atomic energies by neglecting the virials of the forces on the nuclei for partially optimized structures is discussed. © 2015 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

The production of cis -2-butene ( cis -2B) on Pd/Ni(1 1 1) bimetallic model was evaluated considering two possible reactions: through the hydrogenation of 1,3-butadiene (13BD) adsorbed on a cis -geometry site and through the isomerization of trans -2-butene ( trans -2B). For that purpose, density functional theory (DFT) calculations were performed following the corresponding Horiuti–Polanyi mechanisms. In the hydrogenation, two competitive pathways produce cis -2B and trans -2B from 13BD species adsorbed on di-π- cis and 1,2,3,4-tetra-σ sites, respectively. The cis -2B is obtained with smaller energy requirements than the trans -2B isomer in spite of the adsorption of 13BD on the di-π- cis site is 0.10 eV less stable than on the 1,2,3,4-tetra-σ site. On the other hand, the trans -2B previously formed could be isomerized to cis -2B, and vice versa, trough the 2-butyl intermediates, but the elevated energetic barriers to hydrogenate/dehydrogenate both 2B isomers would avoid these processes. In fact, the dehydrogenation reaction is the limiting step of the isomerization reaction. From these results, we infer that on the Pd/Ni(1 1 1) surface the cis -2B isomer is easier to be formed via the 13BD hydrogenation on the di-π- cis site than via the trans / cis isomerization of 2B. [ABSTRACT FROM AUTHOR]

Fundamental aspects of 1-butene oligomerization kinetics were investigated under differential conversion at industrially relevant temperatures and pressures on the zeolite H-beta. An apparent activation energy of 28 kJ mol −1 for dimer formation was measured and suggests that dimer formation rates were limited by mass transfer. The result was in apparent contradiction to the rapid, and not mass transfer limited, rate of butene double bond isomerization. The Weisz–Prater criterion for the rate of butene consumption was 0.007, a value smaller than 1, suggests that butene transport in the zeolite micropores was not in control of the rate of either oligomer formation or double bond isomerizatoin. Oligomerization kinetics are rationalized then by a model in which transport of oligomers out of the zeolite crystal is rate controlling. Titration of external acid sites with n -octyltrichlorosilane was used to ensure that rates of formation of either product were not significantly impacted by catalysis on the outside of the zeolite crystallites. [ABSTRACT FROM AUTHOR]

MFI zeolite was granulated into spheres of 3 ± 0.5 mm in diameter using basic hydrotalcite (HT) as a binder, which was prepared by calcination at 670 K for a few seconds, so called flash calcined HT. The flash calcined HT was found to be effective for the formation of high strength MFI zeolite granules without a significant change of acidity, referred from the measurement of temperature programmed desorption of ammonia and mechanical crushing strength. The results of the 1-butene isomerization and MTO reaction using the obtained MFI zeolite granule containing up to 20 wt.% flash calcined powder as a binder suggested that the catalytic activity of the MFI zeolite was not altered significantly due to the incorporation of the flash calcined HT as a binder, because it was considered to have neutral to basic surface nature. This work demonstrates the formation of high mechanical strength MFI zeolite granules, free from deterioration of catalytic activity. [ABSTRACT FROM AUTHOR]

A detailed theoretical investigation on the thermal decomposition and isomerization of 3-Me-1-heptyl radical is performed at the ab initio CBS-QB3 level of theory. The calculation reveals that the detailed reaction mechanisms of 3-Me-1-heptyl radical mainly incorporate reversible intramolecular hydrogen atom transfer and the beta-site C C bond scission. The standard reaction enthalpies ( Δ r H 298 0 ) and enthalpies of formation ( Δ f H 298 0 ) are determined at the CBS-QB3 level of theory. All investigated decomposition reactions are generally endothermic, while most of the isomerization processes are exothermic. Among the hydrogen atom transfer processes, the 1,3- and 1,2-hydrogen atom migration (R 5 and R 6 , respectively) are prohibited due to their high isomerization barriers, while the 1,6-(R 2 ) and 1,5-hydrogen atom transfer (R 3 ) are kinetically accessible (owing to their low ring strains in the cyclic transition states). Compared with the 1,5-hydrogen atom shift for the n -heptyl radical, the methyl-substitution increases the rate coefficient by a factor of about 3.0. The product distributions are predicted at different temperatures on the basis of the steady-state approximation (SSA). The ultimate and dominant products majorly include ethylene (C 2 H 4 ), propylene (C 3 H 6 ), 1-butylene (1-C 4 H 8 ) and 2-hexene (2-C 6 H 12 ) over the temperature range of 500–2500 K. [ABSTRACT FROM AUTHOR]

• Metallosilicate (Al, Fe, Cu, and Ni) catalysts were synthesized. • The +3 oxidation state of metal bonded in the zeolite structure. • Brønsted acid and redox sites of catalyst handled product distribution. • Oligomerization-cracking route occurred on B 1 Brønsted acid site. • Butene isomerization route reacted on B 2 Brønsted acid site. The metallosilicate catalysts (H-M-silicate, when M = Al, Fe, Cu, and Ni and Si/metal = 20) were synthesized and characterized by XRD, SEM-EDX, XRF, N 2 adsorption and desorption, 27Al MAS NMR, XANES, EXAFS, NH 3 -TPD, NH 3 -IR, and TPO methods to investigate the effect of transition metals substitution in zeolite structure for 1-butene reaction. Only Fe3+ of H-Fe-silicate bonded in the MFI structure like H-ZSM-5, whereas transition metals of H-Cu-silicate and H-Ni-silicate embedded in zeolite matrix over catalyst surface; therefore: the reduction reaction occurred over metal of H-M-silicate catalyst during the reaction. There were two different roles of Brønsted acid site, detected by NH 3 -IR (B 1 at ca. 1470 cm−1 and B 2 at ca. 1660 cm−1). The B 1 Brønsted acid site over micropore surface of catalyst (Si-OH-M) favored oligomerization-cracking route of 1-butene reaction, while butene isomerization route reacted on B 2 Brønsted acid site (Si-OH) over external surface of catalyst (Acid strength: B 1 > B 2) [Display omitted] [ABSTRACT FROM AUTHOR]

The kind of surface MoOX structures on Al2O3-SiO2 was found to determine propene selectivity in the metathesis of ethylene and 2-butene. Compared to isolated tetrahedral MoOX species, their polymerized octahedral counterparts show significantly lower activity for isomerisation of 2- to 1-butene thus hindering nonselective metathesis of these butenes. In addition, they reveal higher ability to engage ethylene in propene formation. [ABSTRACT FROM AUTHOR]

Highlights: [•] Pathways for the cis/trans isomerization of 2-butene on Pt(111). [•] Influence of the hydrogen coverage. [•] At hydrogen saturation coverage, the trans to cis isomerization is favored. [•] At low hydrogen coverage, the cis to trans isomerization is favored. [•] At hydrogen saturation coverage, an Eley–Rideal mechanism is expected. [ABSTRACT FROM AUTHOR]

Highlights: [•] Very slow hydrogenation of butadiene by monomolecular layer of hydrogen on Pd black. [•] However, fast hydrogenation of butadiene/hydrogen mixture due to subsurface hydrogen. [•] Hydrogen loading of subsurface region is regarded as rate determining step. [Copyright &y& Elsevier]

The complex triplet potential energy surface for the reaction of the triplet oxygen atom O(P) with cis-2-butene is investigated at the CBS-QB3 level of theory. The different possible isomerization and dissociation pathways, including both O-additions and H-abstractions, are thoroughly studied. Our calculations show that as found for the trans-2-butene reaction, in the high-pressure limit, the major product is CHCHC(O)H + CH (P1), whereas in the low-pressure limit the most thermodynamically stable product forms CHCO + CHCH (P4). The experimental negative activation energy reported for the addition step is very well reproduced at the CBS-QB3 level of theory. Various thermodynamic and kinetic values of interest for these reactions are predicted for the first time. A discussion on the negative activation energy for the addition step of the trans- and cis-2-butene reactions with O(P) focussing on the addition reactant complexes is presented. [ABSTRACT FROM AUTHOR]

New advances in colloidal and other self-assembly synthetic methods have afforded the controlled growth of nanoparticles with well-defined sizes and shapes. Recently, the catalysis community has been trying to capitalize on this knowledge for the design of new catalytic processes. In particular, the use of metal nanoparticles with specific shapes has been explored in several instances as a way to control reaction selectivity. Here we review the results from our efforts to use platinum nanoparticles dispersed on high-surface-area supports to perform selective olefin conversions. Emphasis is given to the surface-science experiments and quantum-mechanics calculations that led us to identify potential variations in selectivity in carbon-carbon double-bond isomerization and hydrogenation reactions with the structure of the metal surface. Temperature programmed desorption (TPD) and reflection-absorption infrared spectroscopy data for 2-butenes adsorbed on Pt(111) single-crystal surfaces highlighted the relative higher stability of adsorbed cis-2-butene compared to trans-2-butene and the preference for the promotion of trans-to- cis conversions on that surface. It was also determined that coadsorbed hydrogen plays a key role in defining the relative stabilities of the adsorbates, favoring pi rather than di-sigma bonding and reversing the higher stability of the trans adsorbates seen on clean Pt(111). DFT calculations suggested that such unique results may be accounted for by the need for extensive surface reconstruction to accommodate the adsorbates on such flat planes, a requirement that appears to be less severe with the cis isomer. TPD experiments on stepped Pt(557) surfaces pointed to the minimal importance of steps in promoting these isomerization reactions, although they do seem to help with the full hydrogenation to the alkanes. More extensive olefin adsorption destabilization with hydrogen coadsorption and faster alkane production was seen on Pt(100), but selectivity towards the cis isomer was still identified. On the more open (2 × 1)-reconstructed Pt(110) surface, on the other hand, trans-2-butene is the most stable of the two isomers. It was finally shown that these surface-science results translate into changes in selectivity in real catalysts with platinum nanoparticle shape. Catalysts were prepared by using colloidal Pt nanoparticles with tetrahedral, cubic, and rounded shapes, and unique selectivity toward cis-2-butene formation was measured on the first of those samples. It appears that the (111) facets exposed by the tetrahedral Pt nanoparticles do show the same trans-to- cis conversion preference in catalysis seen in the surface-science studies carried out with single-crystal surfaces and under ultrahigh vacuum conditions. [ABSTRACT FROM AUTHOR]

The complex potential energy surface for the reaction of triplet oxygen atom, O(P), with trans-2-butene is investigated at the MP2, PMP2, CCSD(T), CBS-4M and CBS-QB3 levels of theory. Both the O-addition and the two H-abstraction channels are thoroughly investigated. As expected, the calculations show that the O-addition is the most favourable process from a kinetic point of view. Various isomerization and dissociation pathways are explored following the addition of O(P) to trans-2-butene. Our calculations show that in the high-pressure limit, the major products are CHCHC(O)H + CH (P1); whereas in the low-pressure limit the most thermodynamically stable products form: CHCO + CHCH (P4). A more realistic prediction of reaction products is an intermediate case, being P1 more abundant followed by P4, in agreement with experimental data. The CBS-QB3 Gibbs free energies for the O-addition are smaller than those obtained at the CBS-4M level of theory, but the same general trends are obtained by these methods. The reaction and activation enthalpies, calculated at the CBS-QB3 level of theory, are in very good agreement with the experimental results available. [ABSTRACT FROM AUTHOR]

Abstract: Layered aluminosilicates of PLS-3 were hydrothermally synthesized and employed as the catalysts for the skeletal isomerization of 1-butene. PLS-3 lamellar precursors were successfully prepared at different Si/Al ratios (40–∞) using layered silicate H-kanemite as silica source and tetramethylammonium hydroxide as structure directing agent. A direct calcination caused an interlayer dehydration condensation, converting the precursors into 3-dimensional FER structure with an intersecting micropore system of 8×10-membered rings. The physicochemical properties of the Al-PLS-3 materials thus prepared were characterized by various techniques. Their catalytic properties in the skeletal isomerization of 1-butene has been investigated and compared with conventional ferrierite. Al-PLS-3 synthesized at Si/Al=50 exhibited the same catalytic reactivity as commercial ferrierite. However, possessing smaller crystal size, Al-PLS-3 possessed a much longer catalytic duration against coke formation. [Copyright &y& Elsevier]

Abstract: It is still not totally clear as to whether the skeletal isomerization of linear butenes to iso-butene in ferrierite occurs via a mono-molecular or bi-molecular process. To try and shed more light on this process, quantum chemical calculations were undertaken on both mechanisms. A large cluster model (H53O52Si35Al) has been employed here to study the bi-molecular process and these results are contrasted to the mono-molecular results previously reported by the author using the same model. The results suggest that a bi-molecular process can indeed result in the formation of iso-butene, as well as longer chained by-products as exemplified by 2,4,4-trimethylpent-2-ene. A rate determining step of 18.6kcal/mol is found for the bi-molecular process, involving Crmation between the two monomers. The barrier is also predicted to be considerably lower than that of the mono-molecular reaction (24.5kcal/mol). Nevertheless, given that 2,4,4-trimethylpent-2-ene has a considerably lower barrier to reaction, and is more energetically favourable, iso-butene product to might not be expected to form in large quantities via this route. [Copyright &y& Elsevier]

Abstract: Dehydration and isomerization of butanol is studied in an autothermal short contact-time reactor containing a 1wt% Pt stage followed by a zeolite or γ-Al2O3 stage downstream to convert butanol into butenes with up to 95% yield at residence times on the order of 100ms. CH4 is fed as a sacrificial fuel to the Pt stage and butanol is fed between the stages to avoid undesired oxidation and reforming reactions of butanol over Pt. The energy released by CH4 catalytic partial oxidation drives downstream butanol dehydration and isomerization. The effect of catalyst is studied by comparing the performance of HZSM-5, HFER, and γ-Al2O3 catalysts. Higher yields (20%) of butenes were obtained with γ-Al2O3 and HFER than with HZSM-5. The absence of Br∅nsted acid sites in γ-Al2O3 and the small pore structure of HFER lead to reduced yields of large side products such as higher hydrocarbons that promote oligomerization reactions. A 95% butene yield is obtained with HFER at temperatures ranging from 280–350°C and a 95% yield with γ-Al2O3 at temperatures between 320 and 350°C. Only a 75% butene yield was obtained with HZSM-5 at 230°C. The effect of hydrocarbon structure on product formation is studied by comparing conversions of each butanol isomer using a heated tube reactor at temperatures between 200 and 400°C. The reactivity of butanol follows as: t-butanol>2-butanol>iso-butanol>1-butanol. trans-2-Butene and cis-2-butene are primarily formed from linear butanol isomers, while isobutene forms from branched butanol isomers. Conversions and product distributions of butanol isomers formed over HZSM-5 in a staged reactor are comparable (<10% difference across all species) with data using a heated tube reactor at similar temperatures. We successfully demonstrate an alternative pathway to dehydrate butanol into butenes with an autothermal staged reactor compared to conventional methods for applications in small-scale biomass utilization. The largest advantage of this reactor is the integration of highly exothermic autothermal stage and endothermic alcohol dehydration stage which provides an alternative processing technique to maintain the bed temperature. [Copyright &y& Elsevier]

Abstract: Skeletal isomerization of 1-butene has been studied over composite micro/mesoporous zeolitic catalysts prepared by the recrystallization of ferrierite (FER) in alkaline solutions in the presence of cethyltrimethylammonium bromide and by the desilication of FER in alkaline solutions. Desilication procedure led to the creation of large mesopores in zeolite crystal with broad distribution of size. Recrystallization procedure resulted in two types of mesoporosity: uniform intracrystalline mesopores homogeneously distributed along the crystal and intercrystalline ordered mesoporous layers covering zeolite crystal. Recrystallized materials showed improved catalytic performance in skeletal isomerization of 1-butene with respect to both parent and desilicated ferrierites. The effect is due to the improved accessibility of the acid sites and the creation of new pore mouths, in which the active carbonaceous species responsible for selective pseudo-monomolecular pathway can be formed. The improved stability of catalytic activity with time on stream is due to coating of ferrierite crystals with mesoporous layes, which prevent the deactivation of the catalysts. The best catalytic performance was achieved over composite micro/mesoporous materials with intermediate degree of recrystallyzation due to proper balance between zeolitic and mesoporous phases and the amount and density of the acid sites. [Copyright &y& Elsevier]

The mechanisms of the gas-phase elimination kinetics of 1-chloro-3-methylbut-2-ene and 3-chloro-3-methylbut-1-ene and their interconversion have been examined at MP2 and DFT levels of theory. These halide substrates yield isoprene and hydrogen chloride. The results MPW1PW91 calculations agree with the experimental kinetic parameters showing the elimination reaction occurs at greater rate for 1-chloro-3-methylbut-2-ene than that for the 3-chloro-3-methylbut-1-ene isomer. The mechanism for the molecular elimination of 1-chloro-3-methylbut-2-ene suggests proceeding through an uncommon six-membered cyclic transition state for alkyl halides in the gas phase, while 3-chloro-3-methylbut-1-ene eliminates through the usual four-membered cyclic transition state. The elongation and subsequent polarization of the C-Cl bond, in the direction of C^{δ+}..Cl^{δ-}, is rate determining step of these reactions. The isomerization of 1-chloro-3-methylbut-2-ene and 3-chloro-3-methylbut-1-ene was additionally studied. The 1-chloro-3-methylbut-2-ene converts to 3-chloro-3-methylbut-1-ene easier than the reverse reaction. This means that 1-chloro-3-methylbut-2-ene was found thermodynamically more stable than 3-chloro-3-methylbut-1-ene. [ABSTRACT FROM AUTHOR]

The formation of linear aldehyde from isomerization-hydroformylation of 2-butene represents an important subject and current task in industry. Both high activity and excellent regioselectivity were achieved in the rhodium-catalyzed 2-butene isomerization-hydroformylation with 2,2′-bis(dipyrrolylphosphinooxy)-1,1′-(±)-binaphthyl ( 1) as ligand. Bulky phosphite with electron-withdrawing pyrrol groups dramatically improved the selectivity of linear product, and a good yield of 90.5% aldehydes was obtained with an excellent linear aldehyde regioselectivity of 95.3% under optimized condition. Graphical Abstract: Bulky phosphite with electron-withdrawing pyrrol groups dramatically improved the selective of linear product, and an excellent yield of 90.5% aldehydes with 95.3% regioselectivity of linear aldehyde was obtained in the Rh-catalyzed isomerization-hydroformylation of 2-butene in the presence of ligand 1.[Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

Abstract: Using periodic density functional theory calculations, the double bond isomerization of 1-butene to 2-butene over MgO surfaces with and without structure defects is investigated. The basicity of these surfaces was characterized by the adsorption of H2O and CO2. The isomerization process involves two steps: (i) the abstract of H atom from 1-butene to form chemisorbed 2-butenide with allyl group and (ii) the attack of H atom on such species to form 2-butene. It is found that the isomerization barrier is lower over the stepped surface than on the flat surface and kinked sites. The modification of the surface structure to increase the content of stepped sites is thus one of the ways to improve the isomerization activity of double bond in butene. [ABSTRACT FROM AUTHOR]

Abstract: A WO3/MTS-9 catalyst for metathesis of butene to propene and pentene was prepared by supporting tungsten oxide on MTS-9. The prepared catalyst was characterized by a number of experimental techniques including XRD, nitrogen adsorption, NH3-TPD, H2-TPR, UV-DRS and UV-Raman, The characterization data showed that three types of tungsten species (tetrahedral, octahedral polytungstate species and WO3 crystallites) are present on the catalyst. In the case of butene metathesis, the performance of WO3/MTS-9 was tested. On the base of experiment results, we speculated that the tetrahedral and the octahedral polytungstate species may be the active sites rather than crystalline WO3. [Copyright &y& Elsevier]