Oxidation of propane over substituted Keggin phosphomolybdate salts

Ammonium salts, (NH₄)₆HPMo₁₁MO₄₀ (M = Ni, Co, Fe), have been investigated for the oxidation of propane, with molecular oxygen, at temperature ranging between 380 °C and 420 °Cafter in-situ pre-treatment performed at two heating rate of 5 or 9 °C/min. They were characterized by BET method, XRD, ³¹P NMR, UV-Vis and IR techniques. The catalysts were found active in the propane oxidation and selective to propene or acrolein, in particular for samples pre-treated with the heating rate of 9 °C/min.     

丙烷在负载型V2O5/Zr3(PO4)4催化剂上的氧化脱氢

制备了无定型的磷酸锆Ｚｒ３（ＰＯ４）４载体,采用浸渍法在载体上负载０６％～６０％的Ｖ２Ｏ５．所制备的催化剂在丙烷氧化脱氢反应中具有较好的催化性能,如３０％Ｖ２Ｏ５／Ｚｒ３（ＰＯ４）４催化剂在丙烷转化率为１７０％时,丙烯选择性可达５３８％,丙烯收率达９１％．考察了不同反应条件下催化剂的性能．ＸＲＤ、ＩＲ和Ｒａｍａｎ光谱表明,Ｖ２Ｏ５在Ｚｒ３（ＰＯ４）４载体上主要是以高度分散的钒氧物种存在;ＥＳＲ分析结果证明催化剂中存在Ｖ４＋物种,表明Ｖ５＋／Ｖ４＋参与了氧化还原反应．     

Comparative study of coke deposition on catalysts in reactions with and without oxygen

Two types of catalysts, i.e. Pt/γ Al₂O₃ and Cu/Na-ZSM-5, were used to investigate the catalyst activity and amount of coke formation on the spent catalysts. The reactions of particular interest were the hydrocarbon oxidation and the SCR of NO with and without O₂. Propane and propene were used as the hydrocarbon sources. The reaction conditions were as follows: reaction temperature =170–500°C, GHSV=4,000 hr⁻¹, TOS=2 hr, feed composition depending on each reaction, but the composition of gases were fixed as HC=3,000 ppm, NO=1,000 ppm and O₂=2.5%, using He balance. It was found that both the case of Pt/γ Al₂O₃ and the case of Cu/Na-ZSM-5, propene provided higher conversion and coke deposition than propane in the presence or the absence of O₂ and/or NO. For Pt/γ Al₂O₃ catalyst, in case of the absence of oxygen reactions, the propene conversion dropped more rapidly than the propane conversion. Finally the reaction of propene gave a lower percent of hydrocarbon conversion than the reaction of propane. Additionally, propene had a higher percent selectivity of coke formation for the reaction with the absence of oxygen, but propane had a higher percent selectivity of coke formation for the reaction with the presence of oxygen. For Cu/Na-ZSM-5, in the system with absence and presence of oxygen, the addition of oxygen caused a significant change in % coke selectivity. With the presence of NO_x, the percent conversion of both propane and propene decreased and that the % coke selectivity of propane decreased, whereas that of in propene increased.     

Enhanced Propene/Propane Separation by Directional Decoration of the 12‐Membered Rings of Mordenite with ZIF Fragments

Propene/propane separation is challenging due to the very small difference in molecular sizes, boiling points and condensabilities between these molecules. Herein, we report a strategy of introducing ZIF fragments into traditional mordenite (MOR) zeolite to decorate the 12‐membered ring of MOR. After decoration, the originally ineffective zeolite MOR exhibited high kinetic propene/propane selectivities (139 at 25 °C) and achieved efficient propene/propane separation. The propene/propane separation potentials of the resulting adsorbents were further confirmed by breakthrough experiments with equimolar propene/propane (50/50) mixtures.     

Enhanced Propene/Propane Separation by Directional Decoration of the 12-Membered Rings of Mordenite with ZIF Fragments

Propene/propane separation is challenging due to the very small difference in molecular sizes, boiling points and condensabilities between these molecules. Herein, we report a strategy of introducing ZIF fragments into traditional mordenite (MOR) zeolite to decorate the 12-membered ring of MOR. After decoration, the originally ineffective zeolite MOR exhibited high kinetic propene/propane selectivities (139 at 25 °C) and achieved efficient propene/propane separation. The propene/propane separation potentials of the resulting adsorbents were further confirmed by breakthrough experiments with equimolar propene/propane (50/50) mixtures.     

TG/DSC/FTIR/QMS studies on the oxidative decomposition of terpene acrylate homopolymers

The oxidative thermal stability along with the identification of the volatile decomposition products under heating of terpene acrylate homopolymers by using TG/DSC/FTIR/QMS-coupled method was presented. It was found that the decomposition of poly(geranyl acrylate) and poly(neryl acrylate) had quite different course as compared to the decomposition process of poly(citronellyl acrylate) under oxidative conditions. FTIR and QMS analyses confirmed mainly the formation of terpene hydrocarbons, propane, propene, acetic acid, CO, CO₂ and H₂O as the volatile decomposition products under heating of the hompolymers. The results obtained indicated the complex decomposition process of terpene acrylate homopolymers including the random ester bond scissors, the random main carbon chain scissors, decarboxylation, dehydration and oxidation processes of formed gaseous decomposition products and a residue which led to the full decomposition of homopolymers at ca. 600 °C under oxidative conditions.     

Deep oxidation in propane oxidative dehydrogenation to propene over V2O5/γ-Al2O3 studied by in-situ DRIFTS

In-situ DRIFTS was used to study the deep oxidation of propane, a side reaction during propane oxidative dehydrogenation to propene. Strong adsorption of propene was supposed to be the main reason for the deep oxidation. It was found that gaseous oxygen in the feed and the reaction temperature had great influence on the reaction. To obtain a relative high selectivity to propene, the reaction temperature should be maintained at 150250 °C with a proper content of gaseous oxygen in the feed for a certain catalyst and some modifiers which could weaken the adsorption of propene on the catalyst surface would be favorable.     

Cr对Pt-Sn /γ-Al2O3催化剂丙烷脱氢性能的影响

通过H2-TPR、O2-脉冲等表征手段，结合丙烷脱氢催化性能考察了助剂Cr对Pt-Sn/γ-Al2O3催化剂反应性能的影响。结果表明，添加少量Cr可显著改善Pt-Sn/γ-Al2O3催化剂的脱氢稳定性，可提高丙烯选择性，降低催化剂表面积炭量。这是由Cr和Pt-Sn之间存在的协同作用引起的，一方面，Pt促进了Cr的还原，生成了可提高丙烯选择性的+3价Cr；另一方面，Cr使Sn变得难于还原，在强还原气氛下保持了活性氧化态价态，进而改善了催化剂的脱氢稳定性。     

Transient and steady state investigation of selective and non-selective reaction pathways in the oxidative dehydrogenation of propane over supported vanadia catalysts

Mechanistic aspects of the formation of C3H6, CO and CO2 in the oxidative dehydrogenation of propane over VOx/gamma-Al2O3 materials have been investigated by means of steady state and transient isotopic tests. The materials possessed highly dispersed and polymerised VOx species as well as bulk-like V2O5. Propene was primarily formed via oxidative dehydrogenation of propane by lattice oxygen of VOx species. It was suggested that non-selective consecutive propene oxidation is initiated by the breaking of the C-C bond in the molecule by the lattice oxygen, forming formaldehyde as a side product, which is further oxidised to CO and CO2. The following order of initial steady state propene selectivity (at a zero degree of propane conversion) as a function of the nature of VOx species was established: a mixture of bulk-like V2O5 and polymerised VOx>polymerised VOx>highly dispersed VOx species. The low propene selectivity over highly dispersed VOx species was explained by the fact that these species do not fully cover the bare acidic surface of gamma-Al2O3 where propene adsorption and further oxidation take place. Thus, two different locations of COx formation were considered: (i) in the vicinity of acidic sites of the support and (ii) on VOx species. The propene selectivity over samples possessing polymerised VOx species and bulk-like V2O5 strongly decreased with an increasing degree of propane conversion. Contrarily, highly dispersed VOx species showed the lowest ability for consecutive propene oxidation.     

Oxidative dehydrogenation of propane by nitrous oxide and/or oxygen over Co beta zeolite

The oxidative dehydrogenation of propane has been studied with nitrous oxide (or mixture of nitrous oxide and oxygen) as oxidant. Nitrous oxide is a more selective but less active oxidant as compared with molecular oxygen. Upon increasing the concentration of N2O in the reaction mixture of propane and oxygen results in a substantial increase of propane conversion, while the selectivity to propene remains constant. The synergistic effect of O₂ and N₂O leads to a threefold higher yield of propene relative to than that of oxygen or nitrous alone. This revised version was published online in June 2006 with corrections to the Cover Date.     

Selected ion flow tube study of ion-molecule reactions of N(+)(3P) and Kr+ with C3 hydrocarbons propane, propene, and propyne

Reactions of (14)N(+)((3)P), (15)N(+)((3)P), and Kr(+) with propane, propene, and propyne were studied using the selected ion flow tube, SIFT, technique. Thermal rate constants in all N(+)/C(3) systems were k = (2 ± 0.4) × 10(-9) cm(3) molecule(-1) s(-1), close to the collisional rate constants. With propane and propene, only hydrocarbon ions were found among the products of reactions with N(+); in propyne about 15% of the products were N-containing ions (C(3)H(2)N(+), C(2)H(4)N(+), C(2)H(3)N(+), C(2)H(2)N(+)), and the rest were hydrocarbon ions. A comparison with product ions from electron transfer between Kr(+) (of recombination energy similar to that for N(+)((3)P)) and the C(3) hydrocarbons and further analysis of the results led to an estimation of an approximate ratio of electron transfer vs hydride-ion transfer reactions leading to the hydrocarbon product ions: in propane the ratio was 2:1, in propene 3:1, and in propyne 5:1. A fraction of product ions resulted from reactions leading to the excited neutral product N*.     

丙烷氧化脱氢M-Fe-O催化剂的研究

采用微波加热草酸盐共沉淀法制备了一系列M-Fe-O(M=V、Cr、Mn、Co、Ni、Cu、Zn)催化剂,考察了其对丙烷氧化脱氢制丙烯反应的催化性能,并对催化剂进行了BET、XRD、H2-TPR、电导测量等表征.实验结果表明V-Fe-O和Cr-Fe-O催化剂表现出较好的丙烷氧化脱氢制丙烯催化性能.反应温度为873 K时,以V-Fe-O为催化剂时丙烷转化率34.46%,丙烯选择性30.91%;在Cr-Fe-O为催化剂上丙烷转化率36.31%,丙烯选择性34.22%.     

Selective Oxidation of Propane by Lattice Oxygen of Vanadium-Phosphorous Oxide in a Pulse Reactor

Selective oxidation of propane by lattice oxygen of vanadium-phosphorus oxide (VPO) catalysts was investigated with a pulse reactor in which the oxidation of propane and the re-oxidation of catalyst were implemented alternately in the presence of water vapor. The principal products are acrylic acid (AA),acetic acid (HAc), and carbon oxides. In addition, small amounts of C1 and C2 hydrocarbons were also found, molar ratio of AA to HAc is 1.4-2.2. The active oxygen species are those adsorbed on catalyst surface firmly and/or bound to catalyst lattice, i.e. lattice oxygen; the selective oxidation of propane on VPO catalysts can be carried out in a circulating fluidized bed (CFB) riser reactor. For propane oxidation over VPO catalysts, the effects of reaction temperature in a pulse reactor were found almost the same as in a steady-state flow reactor. That is, as the reaction temperature increases, propane conversion and the amount of C1 C2 hydrocarbons in the product increase steadily, while selectivity to acrylic acid and to acetic acid increase prior to 350℃ then begin to drop at temperatures higher than 350℃, and yields of acrylic acid and of acetic acid attained maximum at about 400℃. The maximum yields of acrylic acid and of acetic acid for a single-pass are 7.50% and 4.59% respectively, with 38.2% propane conversion. When theamount of propane pulsed decreases or the amount of catalyst loaded increases, the conversion increases but the selectivity decreases. Increasing the flow rate of carrier gases causes the conversion pass through a minimum but selectivity and yields pass through a maximum. In a fixed bed reactor, it is hard to obtainhigh selectivity at a high reaction conversion due to the further degradation of acrylic acid and acetic acid even though propane was oxidized by the lattice oxygen. The catalytic performance can be improved inthe presence of excess propane. Propylene can be oxidized by lattice oxygen of VPO catalyst at 250℃, nevertheless, selectivity to AA and to HAc are even lower, much more acetic acid was produced (molar ratio of AA to HAc is 0.19:1-0.83:1) though the oxidation products are the same as from propane.     

Zn对Pt-Sn/γ-Al2O3催化剂中Sn的活性状态及丙烷脱氢反应的影响

将少量Zn添加到催化剂Pt-Sn/γ-Al2O3中, 可显著提高催化剂的丙烷脱氢稳定性和丙烯的选择性. 程序升温还原(H2-TPR)和程序升温电导(TPEC)测试结果表明, Zn的存在使Sn在强还原气氛中不易被还原, Sn的氧化态的稳定存在是Sn发挥助剂作用和保持催化剂稳定性的重要条件.     

ZrO2‐Based Alternatives to Conventional Propane Dehydrogenation Catalysts: Active Sites,Design, and Performance

Non‐oxidative dehydrogenation of propane to propene is an established large‐scale process that, however, faces challenges, particularly in catalyst development; these are the toxicity of chromium compounds, high cost of platinum, and catalyst durability. Herein, we describe the design of unconventional catalysts based on bulk materials with a certain defect structure, for example, ZrO₂ promoted with other metal oxides. Comprehensive characterization supports the hypothesis that coordinatively unsaturated Zr cations are the active sites for propane dehydrogenation. Their concentration can be adjusted by varying the kind of ZrO₂ promoter and/or supporting tiny amounts of hydrogenation‐active metal. Accordingly designed Cu(0.05 wt %)/ZrO₂‐La₂O₃ showed industrially relevant activity and durability over ca. 240 h on stream in a series of 60 dehydrogenation and oxidative regeneration cycles between 550 and 625 °C.     

负载型钒基催化剂上丙烷的临氧活化转化

用ＴＰＳＲ（程序升湿表面反应）－ＴＲ（ＦＴ）ＩＲ技术,研究临氧条件下丙烷负载型钒基催化剂上的活化和转化,并与催化剂的可不原性和表面酸性相关联,丙烷氧化脱氢生成丙烯与深度氧化生成ＣＯｘ的起始反应温度相同;而裂解产物Ｃ２Ｈ４和ＣＨ４的生成温度比丙烷氧化脱氢生成丙烯的高得多,可能主要源于丙烷的高温气相裂解,催化剂的表面酸性位和强的可还原性,有利于丙烷中Ｃ－Ｈ键的活化和临氧转化,降低起以攻提高丙烷转化率,     

The destruction of atmospheric pressure propane and propene using a surface discharge plasma reactor

Surface discharge plasma reactors (SDRs) have been shown to be effective in removing a wide range of pollutants. In this study, the effectiveness of a SDR for the removal of propane and propene from an atmospheric pressure air stream was investigated. For an input energy of 100 J L-1, the conversions were found to be 16% and 68% for propane and propene, respectively. The total carbon recovery was found to increase with increasing specific input energy (SIE) for both hydrocarbons. FTIR analysis showed that CO and CO2 are the major end-products, and GC-MS identified formic acid as a significant byproduct. The effect of initial propane concentration was also investigated. The reaction chemistry involved in the oxidative plasma conversion of propane and propene is discussed.     

VMgO催化剂上丙烷和异丁烷临氧催化转化机理

用程序升温反应 -红外光谱技术研究 2 0VMgO和 6 0VMgO催化剂上丙烷和异丁烷临氧催化转化的机理 .结果表明 ,临氧条件下的反应性是异丁烷 >丙烷 ,与其分子中最弱C -H键键能从弱到强顺序相同 ,这意味着临氧活化的第一步可能是断裂分子中强度最弱的C -H键、且为速率控制步骤 ;丙烷临氧反应的深度氧化产物COx 与氧化脱氢产物丙烯的生成是平行和 (或 )连续反应关系 ,而裂解产物乙烯和甲烷的生成则是平行反应 ;异丁烷氧化脱氢反应中C -C键的断裂比丙烷的容易 .     

Additive effect of hydrocarbons on OH radical production in H2 oxidation

Mixtures of hydrocarbons (methane, allene, propyne, propene, and propane)–H₂–O₂ highly diluted with argon were heated to a temperature ranging from 1200 to 1900 K behind reflected shock waves, and the additive effects of methane, allene, propyne, propene, and propane on OH radical production in H₂ oxidation were studied by observing time‐resolved UV‐absorption (306.7 nm). It was found that, in H₂ oxidation below 1500 K, the addition of these hydrocarbons prolonged the delay time of the onset of the rapid OH radical production. An analysis using reported kinetic modeling of C₁–C₄ oxidation gave valuable information for reactions between hydrocarbons and H, O atoms and OH radicals. © 2004 Wiley Periodicals, Inc. Int J Chem Kinet 37: 50–55, 2005     

Kinetic studies of the oxidative coupling of methane over the Mn/Na2WO4/SiO2 catalyst

Oxidative coupling of methane is a direct way to obtain C2 hydrocarbon,and Mn-Na-W/SiO2 catalyst is the most promising among all the catalysts.The 2%Mn/5%Na2WO4/SiO2 catalyst was prepared by the incipient wetness impregnation method.A 7-step heterogeneous reaction model of the oxidative coupling of methane to C2 hydrocarbons was conducted by co-feeding methane and oxygen at a total pressure of 1 bar over the catalyst.The kinetic measurements were carried out in a micro-catalytic fixed bed reactor.The kinetic data were obtained at the appropriate range of reaction conditions (4 kPa＜Po2 ＜20 kPa,20 kPa＜PCZH4 ＜80 kPa,800℃＜T＜900℃).The proposed reaction kinetic scheme consists of three primary and four consecutive reaction steps.The conversions of hydrocarbons and carbon oxides were evaluated by applying Langrnuir-Hinshelwood type rate equations.Power-law rate equation was applied only for the water-gas shift reaction.In addition,the effects of operating conditions on the reaction rate were studied.The proposed kinetic model can predict the conversion of methane and oxygen as well as the yield of C2 hydrocarbons and carbon oxides with an average accuracy of ±15%.