La-Ba系氧化物催化剂用于甲烷氧化偶联

以La_2O_3为基础,碱土金属作为第二组分的二元氧化物催化剂均具有较高的生成C_2活性,特别是La-Ba-O系催化剂具有优良的甲烷氧化偶联活性和稳定性,当La/Ba原子比为2.5时,C_2收率可达20.3％。第三组分的添加有助于提高C_2选择性,特别是添加碱金属,可以抑制完全氧化反应,并提高乙烯/乙烷比。在La:Ba:Na=2.5:1:0.1的催化剂上进行了500/小时的寿命实验,在整个反应期间,催化剂的活性和选择性相当稳定。X-射线物相分析表明,新鲜催化剂除有少量的碳酸钡外,主要是氧化镧和氧化钡的混合物。500小时后的物相基本上是氧化镧和碳酸钡。使用前后催化剂的比表面积及表面La和Ba的分布均无改变。较高的CH_4/O_3比对提高C_2选择性有利,当CH_4:O_2=4:1时,C_2选择性和收率分别为65.1％和19.1％。     

Influence of Pretreatment Conditions on Methane Aromatization Performance of Mo／HZSM—5 and Mo—Cu／HZSM—5 Catalysts

Mo/HZSM-5 is a good catalyst for methane aromatization, and the reaction performance of Mo/HZSM-5 and Cu modified Mo/HZSM-5 catalysts under various pretreatment conditions has been studied. The results indicate that the catalyst presented a distinguished catalytic activity, benzene selectivity and a high stability when the bed temperature was raised in N2 atmosphere.     

Grid‐like Cobalt(II) Layered Complex with an Unprecedented Double 1,2‐Bis(1,2,4‐triazole‐1‐yl)methane Bridges

A novel two‐dimensional cobalt complex, [Co(btrm)₂(dca)]ClO₄ ( 1 , btrm = 1,2‐bis(1,2,4‐triazole‐1‐yl)methane, dca = dicyanamide), was synthesized and characterized. X‐ray diffraction analyses reveal that the title complex crystallizes in the monoclinic space group C2/m with a = 29.507(13)Å, b = 17.804(8) Å, c = 14.709(7) Å, β = 119.916(7)°, Z = 12, and R₁ = 0.0784, wR₂ = 0.2041. The cobalt atom involves a six‐coordinated CoN₆ environment, with a distorted octahedral coordination. Two btrm ligands connect the Co^II atoms with the exodentate nitrogen atoms on the 4‐position of triazole rings to form a sixteen‐membered rhombic grid. The unprecedented double btrm bridges and μ_1,5‐dca bridge connect the cobalt atoms to form a two‐dimensional grid‐like layered structure. The spectroscopic and magnetic properties have also been investigated.     

Methane esterification in oleum

The reactions taking place during methane esterification in oleum were investigated. It was found that the primary products were methyl bisulphate and formaldehyde, which was subsequently oxidized to carbon dioxide. The catalyst, Pd or PtCl₄, was needed to activate methane and for its oxidation to the primary products. The formation of CO₂ was not a catalytic process. It was found that the addition of either carbon dioxide or ester into the reaction mixture did not slow down the reactions. Methane oxidation in oleum is an irreversible process, during which water is produced and subsequently consumed to give sulphuric acid by the reaction with sulphur trioxide. Presented at the 33rd International Conference of the Slovak Society of Chemical Engineering, Tatranské Matliare, 22–26 May 2006.     

Quadrupole mass spectrometric study of positive ions from RF plasmas of pure CH4, CH4/H2, and CH4/Ar systems

Quadrupole mass spectrometry has been employed to characterize the ionic species in the discharges of pure CH₄, CH₄/H₂, and CH₄/Ar systems. For pure methane, the major positive ions in the discharge at low pressure (e.g., 0.15 torr) are CH ₃ ⁺ , C₂H ₃ ⁺ , CH ₂ ⁺ , C₂H ₂ ⁺ , CH ₄ ⁺ , C₂H ₄ ⁺ , and C₂H ₅ ⁺ at high pressure (e.g., 0.5 torr) the major ions are CH ₃ ⁺ , C₂H ₃ ⁺ , C₂H ₅ ⁺ , C₃H ₃ ⁺ , C H₃H ₇ ⁺ , C₄H ₇ ⁺ , C₅H ₇ ⁺ , C₆H ₅ ⁺ , and C₇H ₇ ⁺ . The relative abundances of C₁ ions decrease with increasing pressure, whereas those of higher-order ions increase with pressure. For 5% CH₄ + 95% H₂ mixture, in addition to those sampling from the pure methane plasma at the lower pressure, H _n ⁺ ions have also been detected. For 5% CH₄ +95% Ar mixture, the principal ions are CH ₃ ⁺ , CH ₂ ⁺ , CH⁺, CH ₅ ⁺ , Ar⁺, and ArH⁺; the ions containing more than two carbon atoms are negligible. In these discharges, the CH ₃ ⁺ and C₂H ₃ ⁺ are the most important positive ions in C₁ and C₂ ions, respectively. The ions detected are believed to come from the sheath between the electrode and the luminous plasma, and have high kinetic energy. An ion-molecule reaction mechanism is proposed which can well explain the observed main features of ionic products.Died June 1, 1991.     

Plasma-chemical decomposition of methane during diamond synthesis

Using a mass spectrometric sampling method, we have observed the decomposition of CH₄ in an rf plasma usedfor diamond deposition. The gas samples were extracted through an orifice located downstream of the plasma zone and analyzed online. For the experiments a dilute mixture of H₂ and CH₄ containing 0.1–3% CH₄ has been used. CH₄ is converted to C₂H₂ and C₂H₄ quantitatively. Small amounts of heavier hydrocarbons are formed. A comparison of the experimental results with a recent kinetic model treating a purely thermal environment is made and the differences between our experiment and the model are explained. The role of acetylene as a species formed in an atmosphere rich in atomic hydrogen is proposed. The electron impact dissociation process is suggested as the rare-determining step in the plasma-chemical decomposition of methane.     

CONVERSION OF METHANE AND CARBON DIOXIDE TO AROMATICS OVER CHROMIUM-BASED CATALYSTS:SELECTIVITY AND YIELD OF MAIN PRODUCTS

在８４０℃，０．５ＭＰａ，ＣＨ４／ＣＯ２摩尔比为１．４，接触时间（Ｗ／Ｆ）为０．７９ｈ·ｇ·Ｌ－ｌ的条件下，甲烷和二氧化碳在７．５ｗｔ％Ｃｒ／５．０ｗｔ％Ｎａ／ＳｉＯ２催化剂上共活化得到了４．８％的Ｃ２选择性，４８．７％的芳烃选择性及１．９％的芳烃收率。在钠修饰的铬基催化剂上，成功地一步实现了ＣＨ４和ＣＯ２转化为乙烯及中间物乙烯聚合为芳烃的过程     

Study on methane fermentation and production of vitamin B12 from alcohol waste slurry

We studied biogas fermentation from alcohol waste fluid to evaluate the anaerobic digestion process and the production of vitamin B₁₂ as a byproduct. Anaerobic digestion using acclimated methanogens was performed using the continuously stirred tank reactor (CSTR) and fixed-bed reactor packed with rock wool as carrier material at 55°C. We also studied the effects of metal ions added to the culture broth on methane and vitamin B₁₂ formation. Vitamin B₁₂ production was 2.92 mg/L in the broth of the fixed-bed reactor, twice that of the CSTR. The optimum concentrations of trace metal ions added to the culture liquid for methane and vitamin B₁₂ production were 1.0 and 8 mL/L for the CSTR and fixed-bed reactor, respectively. Furthermore, an effective method for extracting and purifying vitamin B₁₂ from digested fluid was developed.     

Fluorierung von Cyanurchlorid und Tieftemperatur-Kristallstruktur von [(ClCN)3F]+ [AsF6]−

Fluorination of Cyanuric Chloride and Low-Temperature Crystal Structure of [(ClCN)₃F]⁺[AsF₆]^? The low-temperature fluorination of cyanuric chloride, (ClCN)₃, with F₂/AsF₅ in SO₂F₂ solution yielded the salt [(ClCN)₃F]⁺ [AsF₆]^? ( 1 ) essentially in quantitative yield. Compound 1 was identified by a low-temperature single crystal X-ray structure determination: R 3 c, trigonal, a = b = 10.4246(23) Å, c = 15.1850(24) Å, V = 1429.1(4) Å 3, Z = 6, R_F = 0.056, R_w = 0.076 (for significant reflections), R_F = 0.088, R_w = 0.079 (for all reflections). Fluorination of neat (ClCN)₃ with [NF₄]⁺ [Sb₂F₁₁]^? yielded NF₃, CClF₃, SbF₃, N₂ and traces of CF₄. A qualitative scale for the oxidizing strength of the oxidative fluorinators NF₄⁺ and (XCN)₃F⁺ (X = H, F, Cl) has been computed ab initio.