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Unsaturated C4 hydrocarbons are abundant in various petrochemical streams. They can be considered as a potential feedstock for the steam-cracking process, where they must be co-processed with C6 and higher (C6+) hydrocarbons of primary naphtha fractions. Co-pyrolysis experiments aiming at the comparison of different C4 hydrocarbon performances were carried out in a laboratory micro-pyrolysis reactor under standardized conditions: 820 °C, 400 kPa, and 0.2 s residence time in the reaction zone. C4 hydrocarbons were co-pyrolyzed with different co-pyrolysis partners containing longer hydrocarbon chain to study the influence of the co-pyrolysis partner structure on the behavior of C4 hydrocarbons. The yields of the pyrolysis products and the conversion of C4 hydrocarbons were used as the performance factors. A regression model was developed and used as a valuable tool for quantifying the inhibition or acceleration effect of co-pyrolysis on the conversion of co-pyrolyzed hydrocarbons. It was found that the performance of different C4 hydrocarbons in co-pyrolysis is substantially different from the separate pyrolysis of the individual components. [ABSTRACT FROM AUTHOR]

[Display omitted] • Hydrophobic surface of TiO 2 (T805) enhances activity of heteropolyacid/TiO 2 catalysts. • Type of TiO 2 polymorphs as support of heteropolyacid influence on catalyst's activity. • UV light increases the reaction rate of alcohol conversion over HPA/TiO 2 catalysts. • Photothermocatalysis versus thermocatalysis. A series of catalysts based on TiO 2 polymorphs were designed with tungstophosphoric acid H 3 PW 12 O 40 (HPW), either alone or with addition of Fe 2 O 3. These HPW@Fe 2 O 3 @TiO 2 nanocomposites showed satisfactory performance in the dehydration of n -butanol at 120 – 200 °C in gas-phase under both the thermocatalytic and the photothermocatalytic conditions. The highest catalytic activity in this reaction was achieved over HPW supported on the home-designed TiO 2 (HPW/hp), on hp with the addition of Fe 2 O 3 (HPW/Fe/hp) and on the hydrophobic titanium oxide T805 (HPW/T805). The main product turned out to be cis -butene, apart from trans -butene, di- n -butyl ether (DNBE) and butyraldehyde that have also been detected. The influence of the light on the course of the catalytic alcohol conversion was discussed. Basing on proposed energy diagram with electron and hole transfer paths for the HPW@Fe 2 O 3 @TiO 2 catalysts the probable mechanism of charge transfer upon UV irradiation was proposed. [ABSTRACT FROM AUTHOR]

Unsaturated C4 hydrocarbons are abundant in various petrochemical streams. They can be considered as a potential feedstock for the steam-cracking process, where they must be co-processed with C6 and higher (C6+) hydrocarbons of primary naphtha fractions. Co-pyrolysis experiments aiming at the comparison of different C4 hydrocarbon performances were carried out in a laboratory micro-pyrolysis reactor under standardized conditions: 820 °C, 400 kPa, and 0.2 s residence time in the reaction zone. C4 hydrocarbons were co-pyrolyzed with different co-pyrolysis partners containing longer hydrocarbon chain to study the influence of the co-pyrolysis partner structure on the behavior of C4 hydrocarbons. The yields of the pyrolysis products and the conversion of C4 hydrocarbons were used as the performance factors. A regression model was developed and used as a valuable tool for quantifying the inhibition or acceleration effect of co-pyrolysis on the conversion of co-pyrolyzed hydrocarbons. It was found that the performance of different C4 hydrocarbons in co-pyrolysis is substantially different from the separate pyrolysis of the individual components.

• Synergy of Lewis acids and silanols in Sn- and Ti-Beta was investigated by DRIFTS. • Double bond migration of n -butene to cis -2-butene followed AB–AD mechanism. • The isomerization between cis -2-butene and trans -2-butene followed AD–AB mechanism. • Reaction mechanisms of butenes depended on methyl or methylene groups. The synergistic effect of Lewis acidic Sn/Ti sites and silanols in Sn- and Ti-Beta zeolites on the reaction pathways and mechanisms of the conversion of butenes was investigated by in situ diffuse reflectance infrared Fourier transform spectroscopy. The double bond migration reaction of n -butene to cis -2-butene followed an AB–AD mechanism, in which hydrogen abstraction (AB) from the methylene group at Lewis acidic Sn/Ti sites afforded an allyl intermediate, followed by synergistic hydrogen addition (AD) on silanols. In contrast, the following cis – trans isomerization reaction between cis -2-butene and trans -2-butene, and the activation of isobutene, followed an AD–AB mechanism via hydrogen addition to the double bond of butenes on silanols, forming an alkoxyl group rather than allyl group as the intermediate owing to the absence of a methylene group in 2-butene and isobutene. [Display omitted] [ABSTRACT FROM AUTHOR]

Light olefins are the main building blocks used in the petrochemical and chemical industries for the production of different components such as polymers, synthetic fibers, rubbers, and plastic materials. Currently, steam cracking of hydrocarbons is the main technology for the production of light olefins. In steam cracking, the pyrolysis of feedstocks occurs in the cracking furnace, where hydrocarbon feed and steam are first mixed and preheated in the convection section and then enter the furnace radiation section to crack to the desired products. This paper summarizes olefin production via the steam cracking process; and the reaction mechanism and cracking furnace are also discussed. The effect of different operating parameters, including temperature, residence time, feedstock composition, and the steam-to-hydrocarbon ratio, are also reviewed.

Graphical abstract Highlights • Ferrierite zeolite was shown to be efficient in the conversion of isobutanol to butenes. • Selectivity to linear butenes higher than 80% was obtained. • Water addition to the feed leads to selectivation at low conversion. • Selectivation could be favoured by coke and water generated at high conversion. Abstract Ferrierite was shown to be highly efficient in the conversion of isobutanol to butenes with selectivity values higher than 98%. Furthermore, its isomerisation activity is remarkable since proportion of linear butenes higher than 80% was obtained in the present study confirming patents claims. This selectivity was shown to increase with temperature and contact time as well as with time on stream. Neither water added to the feed nor water generated by dehydration has an impact on the structure of ferrierite as shown by XRD and 27Al NMR. A slight enhancement of catalytic activity was observed below 250 °C and could be due to an increase in the number of BAS as suggested by in situ acidity measurements achieved at the reaction temperatures in presence of water vapor while competition of adsorption would inhibit the catalytic activity above 250 °C. Furthermore, water was shown to improve dramatically selectivity to linear butenes at low conversion. We propose that water inhibits the proton shift of isobutylcarbenium ions or deprotonation sites leading to isobutene but not acid sites able to isomerize isobutylcarbenium ions into linear carbocations leading to linear butenes. At high conversions, both coke formation and water generated by dehydration could improve selectivity to linear butenes by neutralization of unselective sites responsible for proton-shift reaction. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Novel Pt and PtSn catalysts are developed from structured supports of α-Al 2 O 3 spheres coated with MgAl 2 O 4 by two methods. • Structured supports show a thin, porous and uniform layer of MgAl 2 O 4 , with a good interaction with the metals. • The bimetallic catalysts show both high values of n-butane conversion (25 – 30%) and selectivity to butenes (89 – 95%). • The excellent performance of PtSn/E-Mg-CN2 is in agreement with the higher PtSn interaction and the lowest particle sizes. Abstract Novel Pt and PtSn catalysts were developed from structured supports of α-Al 2 O 3 spheres coated with MgAl 2 O 4 by two methods: advanced Bohemite-nitrate with purification (BNAP) and citrate-nitrate with two layers (CN2). Both structured supports showed a thin porous layer of MgAl 2 O 4 with a high specific surface area of around 130 m2 g−1. A stable and uniform MgAl 2 O 4 layer on the spherical nuclei was achieved by both synthesized coating methods. Therefore, a good interaction with the metals which leads to high metallic dispersions was obtained. These catalysts were used in the production of butenes by n-butane dehydrogenation reaction. The bimetallic catalysts showed both high values of n-butane conversion (25–30 %) and selectivity to butenes (89–95 %). The PtSn catalyst supported on spheres coated by CN2 method displayed high values of yield to butenes (about 30%), which are higher than those of a catalyst used in the industry. [ABSTRACT FROM AUTHOR]

[Display omitted] • H 4 SiW 12 O 40 , WO 3 , TiO 2 and SnO 2 /SiO 2 catalysts were tested in the dehydration of isobutanol. • The catalytic activity was related to the Brønsted acidity and not the Lewis one. • Selectivity to butenes close to 100% was obtained for weak and moderate Brønsted type catalysts. • Linear butenes were mostly obtained through the equilibrium between carbocations. H 4 SiW 12 O 40 heteropolyanions, WO 3 , TiO 2 and SnO 2 were supported over SiO 2 at high loading by wet impregnation or grafting methods and evaluated in the dehydration of isobutanol to butenes. Their structural and textural properties were determined by different techniques such as XRD, TEM, IR, XPS and N 2 liquid physisorption respectively. Most of the prepared compounds contained amorphous oxide clusters of few nanometers lying over SiO 2 and were mesoporous. Their acidic properties (nature, density and strength) were investigated by pyridine and CO adsorption followed by FTIR. H 4 SiW 12 O 40 /SiO 2 contained strong Brønsted acid sites while mostly moderate Lewis acid sites were present on TiO 2 /SiO 2 and SnO 2 /SiO 2. WO 3 /SiO 2 had a mixed character with both moderate Brønsted and Lewis acid sites. The catalytic activity was related to the Brønsted acidity and the best selectivity to butenes close to 100% were obtained for the catalysts containing moderate and weak sites (WO 3 /SiO 2 and TiO 2 /SiO 2). Except for SnO 2 /SiO 2 catalysts, which were unstable and unselective to dehydration products, a significant selectivity to linear butenes (ca 30%) was obtained with all the catalysts. It is proposed that this isomerisation activity is mainly related to the equilibrium between carbocations formed after E 1 elimination of water. Its slight increase for H 4 SiW 12 O 40 /SiO 2 (and to a lesser extent WO 3 /SiO 2) was attributed to strong Brønsted acid sites able to catalyse the isomerization of isobutene to linear butenes. [ABSTRACT FROM AUTHOR]

Microalgae are increasingly viewed as a sustainable potential resource of chemicals and biologicals. The production of light alkenes (C2-C4 olefins), a major precursor to plastics and other value-added chemicals currently produced from fossil fuels, was studied by catalytically cracking marine microalgae Picochlorum oculatum . The process was studied in the temperature range of 400–650 °C using two aluminosilicate catalysts; (1) commercial Si/Al at catalyst-to-algae mass ratios of zero, 1:1, 5:1, 10:1, and 20:1; and (2) H-β zeolite at a catalyst-to-algae mass ratio of 10:1. Ethene was obtained as the most significant light olefin product followed by propene and butenes as a result of the selectivity of the Si/Al catalyst towards ethene formation. The total olefin yield rose with increasing temperature, as cracking of cellular macromolecules intensified. However, olefin formation started to level off above 550 °C. The total olefin yield also rose with increasing catalyst-to-algae mass ratio, as a result of the presence of more catalytic reaction sites, but the impact lessened at high ratios. A maximum ethene yield (7.3%) was achieved using Si/Al at a catalyst-to-algae mass ratio of 20:1, whereas a maximum propene yield (5.1%) was obtained using H-β zeolite at a catalyst-to-algae ratio of 10:1. The study provided a more effective catalyst for producing light olefins, compared to previous reports, as the maximum total olefin yields of 10.3% and 12.3% with Si/Al (20:1 ratio) and H-β zeolite (10:1 ratio), respectively, exceeded the literature reported yield by 34% and 60%, respectively. [ABSTRACT FROM AUTHOR]

The transformation of 1-butanol into either butenes or maleic anhydride was carried out both with and without oxygen, using V/P/O catalysts. With vanadyl pyrophosphate prepared by coprecipitation, at temperature lower than 240 °C and without oxygen, selectivity to butenes was higher than 90%, but a slow deactivation took place. At temperature higher than 300 °C and in the presence of air, maleic and phthalic anhydrides were the prevailing products, with selectivity of 60% and 14%, respectively. Catalytic performance was affected by crystallinity and acidity. α I -VOPO 4 showed a poor performance in the absence of air, with a quick deactivation due to coke accumulation; but it displayed an excellent selectivity to butenes (close to 98%) at temperatures lower than 320 °C in the presence of air, with stable performance. At temperature higher than 360 °C, α I -VOPO 4 was reduced to vanadyl pyrophosphate and catalyzed the direct oxidation of 1-butanol into maleic anhydride, but with 35% selectivity. [Display omitted] • (VO)2P2O7 catalyses 1-butanol oxidation to maleic anhydride with 60% yield. • The maximum yield to maleic anhydride decreases on increasing 1-butanol inlet concentration. • Both (VO)2P2O7 and αI-VOPO4 catalyse 1-butanol dehydration to butenes but deactivate. • In the presence of O 2 , αI-VOPO4 catalyses 1-butanol dehydration with 98% yield to butenes. • The catalytic performance of αI-VOPO4 in the presence of O 2 is also very stable, with no deactivation. [ABSTRACT FROM AUTHOR]

A brief analysis is performed for the current state of processes for the production of motor fuels based on the consecutive oligomerization and hydrogenation reactions of unsaturated hydrocarbons. Some new butene hydrooligomerization catalysts based on the bifunctional NiO/ВO-AlO, PdO/ВO-AlO, and MoO/ВO-AlO systems are considered. It is shown that the best process performance parameters (a 67 wt % yield of liquid С products at a butene conversion of more than 90%) are achieved with PdO/ВO-AlO catalyst prereduced in a hydrogen medium. The possibility of acetylene hydrooligomerization on NiO/BO-AlO catalyst is demonstrated in principle. It is established that the presence of nickel(II) cations chemically bonded to the surface of a support is of fundamental importance for both acetylene hydrooligomerization and ethylene oligomerization. [ABSTRACT FROM AUTHOR]

The understanding of water effects on solid acid catalysts is a key issue in developing efficient processes to produce olefins by bio-alcohols dehydration. In this work, the effects of water on TiO 2 /SiO 2 catalysts for the gas phase conversion of isobutanol into linear olefins have been unraveled, using for the first time in situ acidity measurements achieved with a flowing NH 3 probe and water vapor containing gas mixtures at adsorption equilibrium in the temperature range of the reaction. Such compounds, prepared by grafting titania onto mesoporous silica, contain well-dispersed TiO 2 amorphous clusters anchored by Ti O Si linkages, leading to much higher catalytic activity than TiO 2 and SiO 2 . They yielded only dehydration products, among which 30% were linear butenes. Furthermore, their activity was significantly improved by addition of water into the feed, whatever the contact time. Acidity measurements indicated that TiO 2 /SiO 2 mixed oxides were mostly of Lewis type after activation at 450 °C. However, in situ FTIR acidity measurements showed that addition of H 2 O to NH 3 /He gas mixture has no influence on the number of Lewis sites, while weak Brønsted sites were formed on other sites. This formation, due to a shift of equilibrium depending on both the temperature and the H 2 O partial pressure, corresponds to the hydrolysis of Ti O Si bonds, generating OH acidic groups and enhancing catalytic activity under water vapor. The novel type of acidity measurements used in this work appear powerful and can be applied to other acidic heterogeneous catalysts. [ABSTRACT FROM AUTHOR]

The oxidative dehydrogenation of a 1-butene/trans-butene (1:1) mixture to 1,3-butadiene was carried out in a two-zone fluidized bed reactor using a Mo-V-MgO and a γ-Bi2MoO6 catalyst. The significant operating conditions temperature, oxygen/butene molar ratio, butene inlet height, and flow velocity were varied to gain high 1,3-butadiene selectivity and yield. Furthermore, axial concentration profiles were measured inside the fluidized bed to gain insight into the reaction network in the two zones. For optimized conditions and with a suitable catalyst, the two-zone fluidized bed reactor makes catalyst regeneration and catalytic reaction possible in a single vessel. In the lower part of the fluidized bed, the oxidation of coke deposits on the catalyst as well as the filling of oxygen vacancies in the lattice can occur. The oxidative dehydrogenation reaction takes place in the upper zone. Thorough particle mixing inside fluidized beds causes permanent particle exchange between both zones. © 2016 American Institute of Chemical Engineers AIChE J, 63: 43-50, 2017 [ABSTRACT FROM AUTHOR]

Existing industrial technologies for the production of motor fuel compounds by the heterogeneous oligomerization of light С-С alkenes are considered, along with ones promising for the practical use. Such basic types of systems used as heterogeneous catalysts in these processes as solid phosphoric acid, amorphous alumosilicates, zeolites, ion-exchange resins, anion-modified metal oxides, and nickel-containing catalysts, are described. Special attention is given to the dimerization of iso-butylene with the formation of iso-octene and its subsequent hydrogenation to iso-octane. [ABSTRACT FROM AUTHOR]

The conversion of isobutane-butenes mixtures on the H-form of ultrastable zeolite Y and sulfated zirconia under supercritical conditions at 150-160°C and 80 atm was studied. The isobutane/C-olefins molar ratios (I/O) were 1.5, 14, and 28. In isobutane alkylation (I/O = 14 and 28), sulfated zirconia was more stable: at 150°C and 80 atm, the olefin conversion above 90% was retained for 5 h. Under the same conditions, the deactivation of the zeolite catalyst started after 1-2.5 h (depending on the initial I/O ratio). Selectivity for the formation of C hydrocarbons was 30-40%. An increase in the butene content of the initial mixture led to the domination of the dimerization of butenes over the alkylation of isobutane. [ABSTRACT FROM AUTHOR]

The possibility of using a fiber-optic densitometer to monitor the density of the reaction medium during heterogeneous catalytic reactions has been shown using the example of the alkylation of isobutane with butenes conducted under supercritical conditions at 150°C and 80 atm. The density has been measured at two points-before and after a fixed bed of an H-USY catalyst. The dependences of the density and refraction of the isobutane-butene mixture on temperature and pressure have been plotted. [ABSTRACT FROM AUTHOR]