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K-doped MoVTeNbOx were prepared rapidly and simply by spray drying method and applied to catalyze the selective oxidation of propane to acrylic acid. Results show that doping of K could affect the relative content of M1 and M2 phases in MoVTeNbOx. The as-prepared K-doped MoVTeNbOx exhibited a unique spherical structure agglomerated by needle particles. These needles shaped particles interlaced and stacked with each other to form a mesoporous structure with an average pore size range of 27.26 to 50.78 nm. Moreover, compared with undoped catalysts, doping of K increased the surface V5+ active sites content of the MoVTeNbOx from 60 to 75%. For the conversion of propane to acrylic acid, an appropriate amount of M2 increased the conversion of propane. The selectivity of K-doped MoVTeNbOx catalyst for acrylic acid was significantly improved, possibly due to the distinct reduction in the number of medium acid sites caused by the introduction of K. Furthermore, the special mesoporous structure formed boosted the adsorption and activation of the catalyst for propane and the diffusion of product, which is important to improve the catalytic performance of MoVTeNbOx. Under the optimal reaction condition, the maximum selectivity and yield of K-doped catalyst (K/Mo = 0.005) for acrylic acid reached 72.06% and 49.57%, respectively. Mesoporous K-doped MoVTeNbOx catalyze the direct oxidation of propane to acrylic acid [ABSTRACT FROM AUTHOR]

PtSn/Al2O3 and PtSnSr/Al2O3 were prepared by the incipient wetness impregnation method. The added Sn and Sr are uniformly distributed on the surface without damaging the original crystal structure and surface texture properties. The addition of Sn not only changes the dispersion of Pt, reduces the reduction temperature of Pt, but also provides electrons to Pt, increases the electron cloud density on the surface of Pt, and reduces the deep propylene adsorption. The addition of Sr reduces the number of total acid sites and strong acid sites, reduces the generation of adverse effects and carbon deposition, slows down the deactivation of the catalyst, and improves the selectivity of propylene. Pt1.5Sn1.5Sr/Al2O3 showed the best catalytic reaction performance and remained stable after five cycles of regeneration. [ABSTRACT FROM AUTHOR]

Non-oxidative propane dehydrogenation is an endothermic reaction requiring thermally stable and regenerable catalysts to produce propylene. In this work, we investigate bimetallic CoXNi2-XP as an alternative, non-noble metal propane dehydrogenation catalyst. Co1Ni1P displayed higher propylene selectivity than Co2P and higher site-normalized propylene production rates than Ni2P. Different compositions of CoXNi2-XP catalysts were evaluated for propane dehydrogenation with oxidative regeneration in between each cycle. Ni-rich Co0.5Ni1.5P showed increased propylene production upon regeneration due to the formation of the Ni12P5 phase during reaction. In contrast, Co1Ni1P and Co1.25Ni0.75P showed the ability to recover > 50% of the initial activity for at least 3 oxidative regenerations, while maintaining high propylene selectivity without any phase change. This study showcases the enhancement in stability and propane dehydrogenation performance of Ni2P through Co incorporation and Ni:Co ratio control. [ABSTRACT FROM AUTHOR]

The dehydrogenation of propane over Pt supported on Ga-doped silica was investigated, using various meso- and microporous silica supports. The addition of a small amount of Ga (0.5 wt%) to SBA-15 was enough to boost the resultant 1 wt% Pt catalyst's conversion from < 5 up to 38%. Propene selectivity also increased from around 60 to 98%. Optimisation of the Pt and Ga content revealed that low loadings of both active components are necessary to increase the efficiency of the reaction and beyond this only modest improvements in performance were obtained. A range of pore structures were investigated, but the Ga content was found to be more important than the support morphology; without sufficient Ga incorporation into the support the catalyst could not achieve high conversion and selectivity. Post-reaction analysis suggested that coke formation blocking sites was the most likely explanation for catalyst deactivation. These results show that doping Ga into SiO2 as a support for Pt nanoparticles is a viable strategy for producing highly efficient catalysts for propane dehydrogenation. [ABSTRACT FROM AUTHOR]

The present work shows experimental results on the catalytic oxidation of C3H8 and CO by Pd nanoparticles supported on MnOx/TiO2 synthesized by the sol–gel method. The results show a strong interaction between Pd and MnOx/TiO2; likewise, the annealing temperature of the TiO2 support modified the catalytic properties of the Pd–MnOx/TiO2 catalyst. In this line, the catalysts with 1 and 2 wt% of Pd loading supported on MnOx/TiO2 showed outstanding catalytic activity oxidizing C3H8 and CO within two temperature intervals: 200–400 °C and 25–200 °C, respectively. The Pd–MnOx/TiO2 catalyst also displayed very high stability during long-term tests and the addition of Pd nanoparticles reduced greatly the oxidation temperature of MnOx/TiO2. The outcomes revealed that the Pd–Mn interaction promoted the formation of new Pd0/Pd2+ active sites as well as the formation of oxygen vacancies and reduced Ti4+ to Ti3+ species, which led to the improvement of the Mn3+ and Mn4+ redox features, thus boosting the catalytic oxidation capacity of the Pd–MnOx/TiO2 catalyst. [ABSTRACT FROM AUTHOR]

In this work, we improved the conventional sequential impregnation synthetic method for preparing Pt–Sn/SiO2 catalysts for propane dehydrogenation. Three different synthesis procedures (Pt calcination (PC), co-calcination (CC) and direct reduction (DR)) were performed and examined for catalytic dehydrogenation of propane. The results shows that the synthesis procedures had a notable influence on the activities of the supported Pt–Sn bimetallic catalysts. Co-calcination method mainly produces Pt1Sn1 alloy nanoparticles over Pt–Sn/SiO2_CC, which was totally inactive in propane dehydrogenation. Pt calcination resulted in the coexistence of Pt0.84Sn0.16, Pt3Sn1, Pt1Sn1 on SiO2. Pt–Sn/SiO2_PC exhibited the medium activity. Direct reduction caused the formation of Pt3Sn alloy nanoparticle. Pt–Sn/SiO2_DR displayed the best catalytic performances among the studied catalysts, with 27% of propane conversion and 99% of selectivity towards propylene. These results in the present work indicated that the beneficial role of Sn requires the suitable catalyst preparation procedures. Direct reduction of Pt–Sn/SiO2 as prepared can afford more homogenous active Pt3Sn1 alloy on Pt–Sn/SiO2_DR. The procedure is simple in operation and much suitable for industrially catalyst preparation. PtxSny (x/y ≥ 3) with face-centered cubic structure are much active than Pt1Sn1 alloy with hexagonal structure. [ABSTRACT FROM AUTHOR]

In this paper, promoter effect of strontium over V catalysts supported on physically mixed Nb2O5–Al2O3 was evaluated for the propane oxidative dehydrogenation to propene. The relationship among acid–base properties, surface species dispersion and catalytic activity was preliminarily established for catalysts prepared by co-impregnation and consecutive impregnation of V and Sr. [ABSTRACT FROM AUTHOR]

Supported platinum catalysts exhibit versatile applications in heterogeneous catalysis while their active sites are identified difficultly due to the structural complexity of solid catalysts. Herein, via a comprehensive microscopic and spectroscopic study using several PtOx/CeO2 catalysts with well-controlled CeO2 morphology, we found that, besides the CeO2 morphology, the structure of supported platinum species over PtOx/CeO2 catalysts is determined by the reaction atmosphere, dominantly forming components of the platinum-ceria solid solution and fine Pt nanoparticles during propane oxidation and preferential oxidation of CO in hydrogen (CO-PROX) reactions, respectively. Catalytic performance of the platinum-ceria catalysts in propane oxidation is tightly associated with the content of metallic Pt sites which is affected by reducibility of platinum-ceria solid solution, whereas the Pt(II) species arising from the Pt-CeO2 interaction coupling with the surface oxygen vacancy concentration of ceria contribute to the CO reactivity in CO-PROX reaction. There results provide insights into the active sites of platinum-ceria catalysts in both reactions and broadens the concept of morphology-dependent catalysis of oxide-based nanocrystal catalysts that varies with the reactions catalyzed. [ABSTRACT FROM AUTHOR]

In this paper, promoter effect of strontium over V catalysts supported on physically mixed Nb2O5–Al2O3 was evaluated for the propane oxidative dehydrogenation to propene. The relationship among acid–base properties, surface species dispersion and catalytic activity was preliminarily established for catalysts prepared by co-impregnation and consecutive impregnation of V and Sr. [ABSTRACT FROM AUTHOR]

Propane dehydrogenation (PDH) has attracted the attention of numerous researchers because of its great potential industrial value. But the existing industrial catalytic systems used metals are environmental unfriendly or expensive such as Cr- and Pt- based catalysts. Herein, a series of catalysts with different contents Zn loading on zeolite composite composed of Beta and Mordenite (named as BMZ) were prepared, and XRD, UV–vis, SEM, TEM, NH3-TPD, N2 adsorption–desorption measurement, 29Si NMR, XPS and FT-IR were employed to characterize the physicochemical properties of the as-prepared catalysts. The results display that as compared with the BMZ, dBMZ (obtained from BMZ by acid treatment) serving as a carrier contributes to giving well-dispersed Zn species with framework Zn and ultrasmall Zn nanoclusters. The interaction between the silanol nest formed by dealuminization resulted from the acid treatment and the metal zinc species, not only realizes the active metal high dispersion and anchoring, but also endows the active metal sites with excellent properties for sintering resistance and renewability. As a typical representative, dBMZ-15 catalyst (loading 15% Zn on dBMZ) shows excellent catalytic performances in PDH with a propane initial conversion of 38.6% and an average propylene selectivity more than 80%. The results also exhibit dBMZ-x has a good renewability for three successive PDH cycles at 530 ℃, and further suggest an excellent PDH catalyst for potential industrial application. Dealumination by acid treatment results in the formation of a large number of silanol nests, which reacts with Zn precursors and promotes the formation of framework Zn species. The introduced mesopores by acid treatment also contributes to the formation of ultra-small Zn nanoclusters. The Zn species anchored in framework or confined in hierarchical pores not only help to improve the catalytic performances for high catalytic activity along with high propylene selectivity, but also to offer the catalyst with a high resistance sintering and renewability during PDH. [ABSTRACT FROM AUTHOR]

In this work, porous sisal fibre carbon (SFC) with high-surface areas was prepared from the sisal fibre calcination process using KOH as chemical activation. The ratio of KOH/C to calcination temperature of the SFC catalyst was optimised, and it was found that 1SFC-900, with the KOH/C ratio of 1 and calcination temperature of 900 °C, was the most suitable propane oxidative dehydrogenation (PODH) catalyst. Under optimal reaction conditions, the propane conversion rate was 53.7%, and the propylene selectivity was 66.4%. The specific activity normalised by the surface areas and other physical properties and the propylene SFC selectivity, including the surface oxygen content, ID/IG and sp3/sp2 ratio of carbon, were investigated. The presence of the surface oxygen groups was beneficial for the specific activity but adverse for the selectivity. That is, the higher sp3/sp2 ratio in the defects will increase the PODH selectivity. The prepared SFC was green and low in cost, with biomass as a raw material. In short, the SFC was a potential effective catalyst for the PODH. [ABSTRACT FROM AUTHOR]

Propane dehydrogenation catalysts, containing Ni and Zn were synthesised with the following wt% (13:0, 11:2, 9:4, 6.5:6.5, 4:9, 2:11 and 0:13) ratios. Structural and textural properties showed that when Zn increased to > 4wt%, a NiZn alloy was formed. The improved catalytic activity for 6.5Ni–6.5Zn/SiO2, 4Ni–9Zn/SiO2 and 2Ni–11Zn/SiO2 was attributed to the formation of the NiZn alloy, with smaller particle size and blocked hydrogenolysis sites due to strong Ni–Zn interactions. Propene selectivity equalled 49%, 54% and 64% for the 6.5Ni–6.5Zn/SiO2, 4Ni–9Zn/SiO2 and 2Ni–11Zn/SiO2 catalysts compared to 0% for the monometallic 13Ni/SiO2 catalyst. In the Ni–Zn bimetallic system, zinc had a higher affinity for sulfur and inhibited the formation of a Ni–S phase. Propene selectivity increased from 8% for 9Ni–4Zn/SiO2 to 64% for 9Ni–4Zn/SiO2–S in three minutes of reaction time. Zinc and sulfur exhibited beneficial geometric and electronic effects, which affect particle size and olefin desorption for improved dehydrogenation activity. [ABSTRACT FROM AUTHOR]

Propane dehydrogenation to propylene, one of the most significant compounds in the chemical industry, has attracted tremendous attention worldwide. A series of V doped graphitic carbon nitride composites (V-g-C3N4) were synthesized via a combination of thermal polymerization of urea and thermal decomposition of NH4VO3. After doping VOx species, the V doped g-C3N4 catalysts achieved an optimal propylene yield of 16.16% with a propylene selectivity of 68.6% at 600 °C, compared with undoped g-C3N4 (a propylene yield of 5.42% with a propylene selectivity of 53.9%) at the same condition. Subsequently, various characterization techniques, including XRD, TEM, FTIR, Raman, XPS, N2 adsorption–desorption, etc., were unitized to investigate the chemical properties and crystalline structures of the prepared catalysts. The essence of catalytic enhancement, such as crystallinity, the main active VOx species, and the newly emerging V–N bonds in V-g-C3N4 catalysts, has been discussed, providing a tentative reaction pathway for CH3(*CH)CH3 and CH3CHCH2* species on V active sites. In general, this work offers a research basis for the bran-new materials design for propane dehydrogenation. [ABSTRACT FROM AUTHOR]

By impregnating 3 wt% Cr into the hydrothermally synthesized silicalite-1 with an average crystal size of 0.06–0.35 μm, the effects of the silanol-group density on the dispersion, structural and electronic characteristics of Cr(VI) oxides are studied for the oxidative dehydrogenation of propane with carbon dioxide (CO2-ODP). Characterization results reveal that the CrOx species are highly dispersed over silicalite-1 irrespective of the crystal sizes, and the highest CrOx dispersion is achieved over silicalite-1 with an average crystal size of 0.15 μm due to its highest density of the silanol nests. Moreover, the textural properties and the relative quantity of the Cr(VI) oxides with different structures are strongly affected by the crystal size of the zeolite. The catalyst by using 0.15 μm silicalite-1 as the support shows the most stable performance for CO2-ODP indexed by the C3H6 yield, which is much superior to the remaining catalysts. The correlation of the characterization data of the fresh and representative spent catalysts with the reaction results rigorously reveals that the catalytic stability of CrOx/silicalite-1 for CO2-ODP is mainly determined by the dual functions of the deposited coke, which is basically originated from the interactions between Cr(VI) oxides and the support. These understandings on the stability of CrOx/silicalite-1 raised essentially from the density of silanol nests over silicalite-1 are beneficial for developing more efficient Cr-based catalysts for the non-oxidative & oxidative dehydrogenation of short alkanes including CO2-ODP. [ABSTRACT FROM AUTHOR]

By impregnating 3 wt% Cr into the hydrothermally synthesized silicalite-1 with an average crystal size of 0.06–0.35 μm, the effects of the silanol-group density on the dispersion, structural and electronic characteristics of Cr(VI) oxides are studied for the oxidative dehydrogenation of propane with carbon dioxide (CO2-ODP). Characterization results reveal that the CrOx species are highly dispersed over silicalite-1 irrespective of the crystal sizes, and the highest CrOx dispersion is achieved over silicalite-1 with an average crystal size of 0.15 μm due to its highest density of the silanol nests. Moreover, the textural properties and the relative quantity of the Cr(VI) oxides with different structures are strongly affected by the crystal size of the zeolite. The catalyst by using 0.15 μm silicalite-1 as the support shows the most stable performance for CO2-ODP indexed by the C3H6 yield, which is much superior to the remaining catalysts. The correlation of the characterization data of the fresh and representative spent catalysts with the reaction results rigorously reveals that the catalytic stability of CrOx/silicalite-1 for CO2-ODP is mainly determined by the dual functions of the deposited coke, which is basically originated from the interactions between Cr(VI) oxides and the support. These understandings on the stability of CrOx/silicalite-1 raised essentially from the density of silanol nests over silicalite-1 are beneficial for developing more efficient Cr-based catalysts for the non-oxidative & oxidative dehydrogenation of short alkanes including CO2-ODP. [ABSTRACT FROM AUTHOR]

Several ratios of highly active Zr modified ZSM-5 catalysts with good stability were prepared via the sol–gel method for oxidative dehydrogenation of propane (ODHP) to olefins (C2H4 + C3H6). The influence of ZSM-5 modification with Zr was studied, and the catalysts were thoroughly characterized with respect to structural morphology, crystallinity, specific surface area, ionic state, and surface acidity. The results showed that Zr modification of ZSM-5 leads to increased pore volume and crystallite size. The morphological and elemental analysis indicated irregularly nano-sized Zr/ZSM-5 catalysts, with a homogeneous dispersion of Zr particles and increased lattice oxygen. The incorporation of Zr to ZSM-5 moderated the surface acidity, caused an increase in the distribution of surface acid strength, and decreased the weak acid sites ratio, making it suitable for olefin selectivity. Zr/ZSM-5 (1:4) exhibited the best catalytic yield and long-time stability towards continuous propane conversion (59.48%), which was accompanied by 87.44% olefins selectivity and olefin yield of 52.23% due to the moderated acidic sites coupled with an increment in the lattice oxygen. Hence, this work offers insight into tuning the surface acidity of zeolites material that enhances superior mass transfer of reactants and products and has better stability and potential to be employed in ODHP applications. [ABSTRACT FROM AUTHOR]

A series of mesoporous cobalt–manganese catalysts were successfully synthesized by sol–gel method as efficient catalysts for the propane oxidation. A significant increase in activity was observed over Co1Mn1Ox catalysts with a T50 value of 203 °C compared to pure oxides of manganese and cobalt. Co3+ species which is formed by diffusion of Co2+ ions into spinel octahedral sites are thought to be a key factor influencing catalyst activity. The large amount of Co3+ species provides the sites for the reaction and enhances the redox capacity of the catalyst. In addition, the high specific surface area and the better oxygen migration promote the low-temperature oxidation of propane. The large specific surface area and mesoporous structure accelerate the diffusion and adsorption of gases, and the increased oxygen migration capacity accelerates the rate of oxidation reactions, all of which have a positive effect on propane oxidation. [ABSTRACT FROM AUTHOR]

A series of Pt catalysts supported on SO42− group modified Al2O3 were synthesized and tested for methane and propane combustion. The introduction of SO42− group promoted the surface acidity but reduced the quantity of exposed surface Pt atoms due to strong coordination effect. The presence of SO42− group significantly promoted the propane combustion reaction but inhibited the methane combustion reaction. It can be inferred that the promotion on propane combustion is ascribed to the enhanced activation of C–C bond (370.3 kJ mol−1) by sulfates. Whereas the sulfates are not favorable for the activation and cracking of C-H bond (439.3 kJ mol−1), and the reduced number of exposed Pt sites results in the activity decrease of methane combustion. [ABSTRACT FROM AUTHOR]

In this work, density functional theory is used to study the mechanism of propane dehydrogenation over non-metallic C3N catalyst. The structure, electrostatic potential and density of state of C3N are introduced, as well as the adsorption of reactants on catalyst is studied. The propane dehydrogenation reaction is divided into the first dehydrogenation and the second dehydrogenation (deep dehydrogenation). We explore the possible dehydrogenation pathways in two-step dehydrogenation. The rate control step of the first dehydrogenation is the removal of methylene hydrogen atom from propane, and its energy barrier is 47.79 kcal/mol, which reflected the catalytic activity of the catalyst. The rate control step of deep dehydrogenation is the process of removing the first hydrogen atom of the product propylene to produce the by-product. The energy barrier is 72.80 kcal/mol, which is much larger than that of the first step of dehydrogenation, reflecting the excellent selectivity of the catalyst. [ABSTRACT FROM AUTHOR]

CeO2, V2O5 and CeVO4 were synthesised as bulk oxides, or deposited over activated carbon, characterized by XRD, HRTEM, CO2-TPO, C3H8-TPR, DRIFTS and Raman techniques and tested in propane oxidative dehydrogenation using CO2. Complete oxidation of propane to CO and CO2 is favoured by lattice oxygen of CeO2. The temperature programmed experiments show the ~ 4 nm AC supported CeO2 crystallites become more susceptible to reduction by propane, but less prone to re-oxidation with CO2 compared to bulk CeO2. Catalytic activity of CeVO4/AC catalysts requires a 1–2 nm amorphous CeVO4 layer. During reaction, the amorphous CeVO4 layer crystallises and several atomic layers of carbon cover the CeVO4 surface, resulting in deactivation. During reaction, V2O5 is irreversibly reduced to V2O3. The lattice oxygen in bulk V2O5 favours catalytic activity and propene selectivity. Bulk V2O3 promotes only propane cracking with no propene selectivity. In VOx/AC materials, vanadium carbide is the catalytically active phase. Propane dehydrogenation over VC proceeds via chemisorbed oxygen species originating from the dissociated CO2. [ABSTRACT FROM AUTHOR]

Highly active Ga2O3 nanoparticles catalysts were prepared by one-step oxidative decomposition of gallium nitrate with sucrose-derived carbon foams (SCF) template. The catalysts were investigated by XRD, Ar physisorption, SEM–EDS, HRTEM, TGA, NH3-TPD and 71 Ga MAS NMR. The addition of sucrose facilitated the higher surface area of Ga2O3 nanoparticles and morphological transformation from bulk to flake due to the structure-directing role of the sucrose solution. Moreover, the weak-medium surface acid sites increased by adding sucrose properly, which was related to the larger number of tetrahedral Ga3+ cations. The optimum catalytic activity was achieved over SXCF-Ga2O3 catalysts at the sucrose/Ga2O3 molar ratio of 6 with the propane conversion of 46.63% and propene selectivity of 88.18%. [ABSTRACT FROM AUTHOR]

A series of La doped Co3O4 catalysts were synthesized through hydrothermal routes and employed in C3H8 combustion to investigate the effect of La doping on the structural and catalytic properties of Co3O4 catalysts. The results showed that the presence of La could induce lattice distortion in Co3O4, which facilitated the formation of oxygen vacancies, thus improving the activation and adsorption of gas phase oxygen. Moreover, the DRIFT experiments indicated that the dopant of La was not only beneficial to the adsorption of C3H8 but also helpful in the inhibition of surface carbonates accumulation. As a result, the Co3O4 doped with 1.8% molar ratio of La (CoLa-1.8) exhibited the best catalytic performance towards C3H8 combustion with T50 and T90 as low as 230 °C and 264 °C. [ABSTRACT FROM AUTHOR]

4Ni–Al layered double hydroxide (LDH) precursors were prepared by the following three methods: constant pH coprecipitation, variable pH coprecipitation and urea hydrolysis. The 4Ni–Al mixed metal oxide (MMO) catalysts were obtained by the calcination of LDH precursors at 600 °C, and their catalytic performances in ODHP from 350 to 550 °C were tested. The 4Ni–Al MMO from the urea hydrolysis method showed a higher and more stable propylene selectivity of ca. 40% with propylene yield of ca.11% at 500 °C, and that from the constant pH coprecipitation method was followed, while oxidative cracking of propane occurred on the 4Ni–Al MMO from the variable pH coprecipitation method. It is considered to be closely related to the dispersion and stability of the surface Ni(II) species through comprehensive analysis of XRD, N2-adsorption-desorption, TEM, XPS, H2-TPR and In-situ electrical conductivity. The urea hydrolysis method with a low salt concentration, leading to an excellent stability of the surface Ni(II) species at high reaction temperature, should be selected to prepare Ni–Al MMO catalysts for ODHP instead of the traditional variable pH coprecipitation method with a high salt concentration. [ABSTRACT FROM AUTHOR]

The behaviors of C3H8 catalytic combustion were investigated over spinel AB2O4 (AB2O4 prepared by co-precipitation method) with two transition metal (A and B are both transition metal elements) and single transition metal (A is transition metal element). Results showed that the spinel AFe2O4 (A = Ni, Cu) owned superior catalytic activities than the spinel AAl2O4 (A = Ni, Cu). In combination with XRD, SEM, Raman, XPS and H2-TPR, it could be deduced that higher activity was dependent on abundant surface oxygen vacancy and adsorbed oxygen species. The oxygen activation was enhanced by the doping of another transition metal in B sites of AB2O4. As a result, the catalytic performance was promoted. Among as-prepared catalysts, NiFe2O4 owned more superior activity and hydrothermal stability for C3H8 combustion than noble metal catalyst. It is expected to be applicable in the removal of VOCs. Due to the B-site transition metal doping, the surface oxygen activation behavior of the spinel catalyst can be modulated, which makes AFe2O4 have a higher propane catalytic activity than AAl2O4. [ABSTRACT FROM AUTHOR]

Vanadium oxide supported on TiO2(P25) catalysts were synthesized via atomic layer deposition (ALD) of vanadyl acetylacetonate (VO(acac)2). Comprehensive investigations were performed to evaluate the ALD temperature window and the saturation deposition period of VO(acac)2, which were found to be 140–210 °C and 120 min, respectively. The synthesized catalysts were compared to their corresponding impregnation ones for the oxidative dehydrogenation of propane reaction (ODH-P). The ODH-P results indicated the superior performance of the ALD catalysts for the low temperature ODH-P (< 350 °C) given its better dispersion of vanadium oxide(vanadia) in the ALD catalysts. Several characterization techniques including HR-TEM, FE-SEM, XRD, BET, XPS, O2-chemisorption, ICP-OES, and H2-TPR were utilized to evaluate the influence of the ALD and impregnation methods of synthesis on different features of the catalysts. It was observed that the ALD method could offer far better dispersion of the active phase on the support of the catalyst, which is beneficial for the catalytic performance. Variations of Hacac, acetone, and CO2 FTIR absorbance peaks' areas versus the support temperature [ABSTRACT FROM AUTHOR]

Catalytic dehydrogenation of propane to propylene is one of the vital processes in the petrochemical industry, primarily because of the extensive use of propylene as one of the most crucial building blocks for the production of a wide range of essential chemicals and polymers. In this study, the nano-structural PtSnK was supported on an alumina carrier prepared by an environmentally friendly modified oil-drop method. By adjusting the aging temperature of the alumina carrier, the physical and chemical structural properties of the catalyst can be modulated, and then affect the propane dehydrogenation performance of the catalyst. The effects of aging temperature on the structure and chemical properties of the support and catalyst were studied by N2 sorption, XRD, TEM, TG, NH3-TPD, H2-TPR, CO pulse adsorption, and XPS techniques. As the aging temperature increases, the spherical particles gradually changed from a worm-like structure to a needle or rod-like structure. At the same time, the pore size and volume increase, the pore size distribution becomes wider. Besides, the aging temperature also affects the interaction between the supported metal and the alumina support. The higher aging temperature can inhibit the reduction of SnOx species and enhance the interaction between Sn species and the alumina support. All these features together ensure excellent propane dehydrogenation performance and high stability of the catalyst. When the aging temperature is 140 °C, the PtSnK/Al2O3 catalyst exhibits excellent catalytic propane dehydrogenation performance, with an average propane conversion of 36.5%, average propylene selectivity of 96.5% during 50 h reaction. We reported the modulation of the aging temperature on the physical and chemical properties of the PtSnK/Al2O3 propane dehydrogenation catalyst when the alumina carrier is prepared by the oil-drop method. In order to obtain an optimal propane dehydrogenation catalyst, an optimum aging temperature is preferred to provide a catalyst with high propane conversion, propylene selectivity and catalyst stability. [ABSTRACT FROM AUTHOR]

Composite oxide catalysts with Co/Mn/Ce molar ratio of 3:x:2(x = 1, 3, 5 and 7) have been successfully prepared by co-precipitation method. The crystal phase structure, elemental valence, oxygen vacancy and reductivity of the catalysts were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), electron paramagnetic resonance (EPR), H2 temperature program reduction(H2-TPR) and in situ DRIFTs. The results demonstrated that when x = 1, the Co–Mn–Ce catalyst had the smallest grain size and oxygen vacancy. A flow reactor experimental system was used to analyze the effect of Mn content on light-off temperature (T10) and complete oxidation temperature (T90) of propane oxidation over Co–Mn–Ce catalysts under anhydrous condition and 5% vol of water vapor. The results showed that when x = 1, the catalyst exhibits the highest activity (T10 = 200 °C, T90 = 307 °C) and water tolerance among the four catalysts. It indicated that when x = 1, the incorporation of Mn content can improve the ability of Co–Mn–Ce catalysts for propane oxidation. Based on the Langmuir–Hinshelwood theory, the surface chemical reaction pathway of propane oxidation was constructed and it revealed that the major active sites of Co–Mn–Ce catalysts mainly depend on surface oxygen vacancy and the surface active species (Mn4+,Oads). [ABSTRACT FROM AUTHOR]

Hydrodeoxygenation (HDO) of m-cresol using H2 produced by dehydrogenation of n-hexane to hexenes is demonstrated at 673 K over a Pt-WOx/C catalyst at 36 bar. The reaction is possible because deactivation of Pt/C during n-hexane dehydrogenation is greatly suppressed at higher pressures. Flow-reactor measurements of pure n-hexane over Pt/C showed rapid deactivation at 1 bar and 773 K but the catalyst was stable for at least 5 h at 36 bar. While the Pt/C catalyst showed poor activity for HDO of m-cresol, the Pt-WOx/C catalyst was able to utilize the H2 to selectively catalyze m-cresol to toluene, simultaneously pushing the conversion of n-hexane above the equilibrium value that would be achieved in the absence of H2 consumption. To explain the increased stability for alkane dehydrogenation at higher pressures, a microkinetic model of propane dehydrogenation, a surrogate of hexane, was analyzed. The model demonstrates that the coverage of vacancies increases with increasing pressure at the expense of species believed to be coke precursors. [ABSTRACT FROM AUTHOR]

La2O3 nanorods were prepared by simple hydrothermal synthesis method. Yttrium oxide (1, 3, 5 and 7 wt%) supported La2O3 and SO42− incorporated La2O3 nanorods were prepared impregnation method and used as catalysts in oxidative cracking of n-propane. The pure La2O3 nanorods exhibited 15% n-propane conversion with 22% olefins (ethane and propene) selectivity. Considerable improvement in n-propane conversion was observed in case of 3 wt% yttrium oxide supported on La2O3 nanorods (25% conversion of n-propane and 36% selectivity to olefins) at reaction temperature of 550 °C. Interestingly, 5 wt% yttrium oxide supported 10 wt% SO42−/La2O3 nanorod sample exhibited superior performance in n-propane conversion (42%) and olefins selectivity (54%). The yttrium oxide loading and sulfation of La2O3 nanorods influenced the catalytic activity. The characterization of synthesized nanomaterials was performed using elemental analysis, XRD, FT-IR, N2-physisorption, SEM, XPS and H2-TPR techniques. The obtained results indicated that yttrium oxide was highly dispersed over the La2O3 nanorods because of strong interaction between the two rare earth metal oxides. Additionally, deposition of yttrium oxide to sulfated La2O3 nanorods increased the surface area and the amount of Lewis acid sites (for the activation of n-propane) on La2O3 nanorods. Yttrium oxide supported sulfated La2O3 catalyst showed no deactivation during the 24 h of reaction and without coke formation. [ABSTRACT FROM AUTHOR]

Platinum-based catalysts are promising materials for the propane dehydrogenation (PDH). The Pt sintering and carbon deposition are still the urgent problems to be solved in this system. This paper investigates an investigation of effect of perovskite-type oxide (PTO) lattice confinement on the catalytic performance of Zn(Ni)TiO3/SiO2 supported Pt–Ni bimetallic catalysts for PDH. The supported PTO precursors and derived catalysts were analyzed by XRD, H2-TPR, TEM, XPS and TG techniques. The results show that the Pt–Ni alloy nanoparticles (NPs) are formed and highly dispersed on Zn(Ni)TiO3/SiO2. The optimized Pt loading amount is 0.4 wt%, which enhances the propane conversion to 38.6% and propene selectivity of 96.6%. The superior catalytic performance and anti-sintering and carbon deposition ability of Pt–Ni/Zn(Ni)TiO3/SiO2 catalyst are ascribed to the addition of appropriate Pt amount, which is beneficial to being confined in PTO lattice and building the abundant Pt–Ni alloy sites and moderate Pt–Ni interaction. The unconfined Pt coming from excessive Pt addition and impregnated Pt can result in Pt sintering and carbon formation. [ABSTRACT FROM AUTHOR]

In this study, an attempt was made to modify Zn/HZSM-5 aromatization catalyst by successively impregnating Sn and Pt. Among prepared catalysts, the Zn6.0Sn0.2Pt0.1/HZSM-5 catalyst exhibited excellent catalytic performances in both activation and aromatics selectivity. Multi-techniques including XRD, nitrogen physisorption, NH3-IR, TEM, HAADF-STEM/EDX and operando dual beam Fourier transform infrared (DB-FT-IR) spectroscopy were applied to study Zn6.0Sn0.2Pt0.1/HZSM-5 catalyst to gain insight into its active sites and collaboration of them. It is concluded that, in the Zn6.0Sn0.2Pt0.1/HZSM-5 catalyst, the aromatization of propane was catalyzed by the cooperation between Brønsted acid sites (bridging hydroxyls)–Lewis acid sites [zinc species and metallic alloy (SnPt nano clusters)]. Sn had crucial mediation effect which remarkably improved metal dispersion and finely tuned metal–metal interactions. Furthermore, the 3000-h fixed-bed propane aromatization stability test indicated that the Zn6.0Sn0.2Pt0.1/HZSM-5 catalyst also had very prominent anti-coking deactivation ability. [ABSTRACT FROM AUTHOR]

Abstract: The potassium-modified vanadium-incorporated mesoporous silica catalysts (K/V-KIT-6) were synthesized by an incipient wetness impregnation method assisted by ultrasonic and vacuumed treatments. The effect of potassium on the structure and physic-chemical properties of V-KIT-6 mesoporous silica catalysts has been studied by a variety of techniques including N2 adsorption-desorption, XRD, TEM, UV-Vis DRS, H2-TPR and Raman spectroscopy. The catalytic behaviors over K/V-KIT-6 catalysts with low and high V contents for the oxidative dehydrogenation of propane (ODHP) were also comparatively evaluated. For the V0.5-KIT-6 catalyst with low V content, the K-modification can promote the formation of isolated VOx species with strongly distorted structures. It shows a positive effect on the conversion of propane and selectivity of propylene. In contrast, for the V1.8-KIT-6 catalyst with relatively high V content, potassium reacts with vanadium oxide species and alters the structural and physic-chemical properties, because there is a strong interaction between K+ and vanadia species, which results in changing the structure of vanadia species and forming new species. The catalytic performance demonstrates that these transformations of active species are unfavorable for the oxidative dehydrogenation of propane to propylene.Graphical Abstract: [ABSTRACT FROM AUTHOR]

Abstract: A series of Cr-TUD-1 catalysts with various loadings of chromium (3, 5, 7, and 9 wt%) were prepared by microwave irradiation and explored for oxidative dehydrogenation of propane to propylene utilizing CO2 as soft oxidant. The microwave irradiation reduced the synthesis time and the resulting Cr-TUD-1 catalysts exhibited a high specific surface area of more than 600 m2 g−1. The synthesized catalysts were characterized by various techniques including XRD, XPS, TEM, UV–vis DRS, BET surface area, and pore size distribution to understand the physicochemical properties, and to correlate with the catalytic activity. Among various compositions, the 7% Cr-TUD-1 catalyst exhibited a high propane conversion (~ 45%) with better propylene product selectivity (~ 75%). The Cr-TUD-1 catalyst was also found to be quite stable up to 8 h of time-on-stream investigated. As revealed by the characterization techniques, the inter-convertible Cr6+ to Cr3+/2+ species are very crucial for the observed better catalytic activity of these materials. The TUD-1 enables to encapsulate the chromium nanoparticles in the porous silica structure with high dispersion which help in maintaining the better catalytic performance.Graphical Abstract: [ABSTRACT FROM AUTHOR]

Nickel-cobalt bimetallic nanoparticles coated with several layers of graphene were developed through direct heating treatment of bimetallic oxide precursor prepared by the modified Pechini-type sol-gel method. These nanomaterials were demonstrated to be versatile catalysts for lignin depolymerization. The catalysts showed unexpectedly tunable selectivity that directly depends on the composition of bimetallic nanoparticles. Dimeric lignin model compounds can be converted totally and the hydrogenolysis selectivities above 85% over Ni-Co@C (Ni:Co = 1:3). During the recycling test, the nanocatalyst showed excellent recyclability in the ten-batch investigation. The deposition of graphene layers over bimetal nanoparticles fosters a subtle balance between protecting effects and surface accessibility to catalytic reactions and significantly improves their stability to air and moisture. Ni-Co@C catalysts were readily separated from the liquid mixtures with high recycling ratio due to their magnetic properties. Graphical Abstract: Ni-Co bimetallic nanoparticles are coated with graphene layers. Graphene layers over the nanoparticles protect them from deactivation. Ni-Co@C shows tunable selectivity in the hydrogenolysis of dimeric lignin linkage. The non-precious metal catalyst showed excellent recyclability and can be reused ten times without significant loss of activity. [ABSTRACT FROM AUTHOR]

Single-site Ga/SiO catalysts exhibit up to 99% CH selectivity at 4% propane conversion with an initial rate of 5.4 × 10 (mole CH) (mole Ga) s during propane dehydrogenation (PDH) at 550 °C. Following pre-treatment in H at 550 °C, only four-coordinate, Ga-O Lewis acid sites are observed under reaction conditions. At 650 °C in H, an additional isolated Ga site with lower Ga-O coordination ( N < 4) is formed and leads to a 30% decrease in the initial PDH rate per total moles of Ga. The PDH rates are equivalent when normalized by the amount of surface, four-coordinate Ga-O, regardless of catalyst pre-treatment conditions, which indicates that these isolated Ga centers are the catalytically relevant sites. Graphical Abstract: Isolated, Lewis acidic Ga cations present as four-coordinate Ga-O centers exhibit up to 99% CH selectivity during propane dehydrogenation (PDH) at 550 °C. An additional isolated Ga site with lower Ga-O coordination is formed during H treatment at elevated temperatures, but is inactive for PDH and reversibly decomposes under reaction conditions. [ABSTRACT FROM AUTHOR]

Dehydrogenation of propane to propene is one of the important reactions for the production of higher-value chemical intermediates. In the commercial processes, platinum- or chromium oxide-based catalysts have been used for catalytic propane dehydrogenation. Herein, we first report that bulk tungsten oxide can serve as the catalyst for propane dehydrogenation. Tungsten oxide is activated by hydrogen pretreatment and/or co-feeding of hydrogen. Its catalytic activity strongly depends on hydrogen pretreatment time and partial pressure of hydrogen in the feed gas. The activation of tungsten oxide by hydrogen is attributed to reduction of the metal oxide and presence of multivalent oxidation states. Comparison of the catalytic performance of partially reduced WO to other highly active metal oxides shows that WO exhibits superior catalytic activity and selectivity than CrO and GaO. The findings of this work provide the possibility for activation of metal oxides for catalytic reactions and the opportunity for the development of new type of catalytic systems utilizing partially reduced metal oxides. Graphical Abstract: [ABSTRACT FROM AUTHOR]

We disclose synthesis of a novel dicationic 1,3-bis(1-methyl-1 H-imidazol-3-ium) propane copper(I) dibromate [Bis-(MIM)](CuBr)] and explored its potential as a heterogeneous catalyst in 1,3-dipolar cycloaddition for regioselective synthesis of 1, 4-disubstituted-1,2,3- triazoles in excellent yields in ethanol: water (60:40%) system at 80°C. The noteworthy feature of the protocol includes in situ generation of aryl azides by azotisation of aryl as well as alkyl halides with sodium azide thereby enduring facile 1,3-dipolar cycloaddition with terminal alkynes. Graphical Abstract: [ABSTRACT FROM AUTHOR]

The aim of this study was to clarify the effect of the non-stoichiometry in the ACrO (A: La, Pr, Nd, 0.90 ≤ x ≤ 1.05) perovskite-type oxide on the dehydrogenation performance of propane using steam (DHP-S). The slight change in the molar ratio of the A-site (=La, Pr, Nd) to the B-site cation (=Cr) from the stoichiometric composition (A/B = 1) significantly affected the dehydrogenation performance. For the La-based catalyst, the LaCrO catalyst with 0.90 ≤ x ≤ 0.97 displayed a relatively high activity, while the catalyst with 0.97 < x ≤ 1.05 did not show any activity for the DHP-S. The perovskite catalyst having the A-site defect presented a high performance for the DHP-S regardless of the types of A-site cation. The NdCrO catalyst displayed the highest performance among the A-site defective perovskite catalysts. The NdCrO catalyst also showed a superior stability compared to the CrO/γ-AlO catalyst. Based on an XPS measurement, the reduction-oxidation (redox) property was improved by changing the Nd/Cr molar ratio from the stoichiometric composition (Nd/Cr = 1) to a non-stoichiometric composition. Such a good redox property would produce a high performance for the DHP-S. Graphical Abstract: [ABSTRACT FROM AUTHOR]

Catalysts from three different catalytic systems, Ni-Nb-O, Mo-V-Nb-Te-O and Sb-V-O, have been prepared, characterized, and tested during both ethane and propane ammoxidation reactions, in order to obtain acetonitrile and acrylonitrile, respectively. The catalytic results show that Mo-V-Nb-Te-O and Sb-V-O catalyze propane ammoxidation but are inactive for ethane ammoxidation whereas Ni-Nb-O catalysts catalyze both, ethane and propane ammoxidation. The activity results, and the characterization of fresh and used catalysts along with some data from previous studies, indicate that the ammoxidation reaction mechanism that occurs in these catalytic systems is different. In the case of Mo-V-Nb-Te-O and Sb-V-O, two active sites appear to be involved. In the case of Ni-Nb-O catalysts, only one site seems to be involved, which underlines that the mechanism is different and take place via a different intermediate. These catalysts activate the methyl groups in ethane, on the contrary, neither ethane nor ethylene appear to adsorb on the Mo-V-Nb-Te-O and Sb-V-O active sites. Graphical Abstract: [ABSTRACT FROM AUTHOR]