Selective Production of Carbon Monoxide via Methane Oxychlorination over Vanadyl Pyrophosphate

A catalytic process is demonstrated for the selective conversion of methane into carbon monoxide via oxychlorination chemistry. The process involves addition of HCl to a CH₄–O₂ feed to facilitate C?H bond activation under mild conditions, leading to the formation of chloromethanes, CH₃Cl and CH₂Cl₂. The latter are oxidized in situ over the same catalyst, yielding CO and recycling HCl. A material exhibiting chlorine evolution by HCl oxidation, high activity to oxidize chloromethanes into CO, and no ability to oxidize CO, is therefore essential to accomplish this target. Following these design criteria, vanadyl pyrophosphate (VPO) was identified as an outstanding catalyst, exhibiting a CO yield up to approximately 35 % at 96 % selectivity and stable behavior. These findings constitute a basis for the development of a process enabling the on‐site valorization of stranded natural‐gas reserves using CO as a highly versatile platform molecule.     

F-atom concentration measurement via HCl titration

Titration of F atoms with HCl is shown to be described principally by the reaction, F + HCl → HF + Cl. This conclusion is arrived at by observing the effect of HCl titration on the intensity of an F-atom ESR signal, the signal intensity being proportional to F-atom concentration. The intensity decreases linearly with increasing HCl flow and (1.07 ± 0.12) HCl molecules are required for removal of each F atom. Since the titration volume contains F₂ as well as F, this latter result demonstrates the secondary importance of the competing reaction, Cl + F₂ → ClF + F. Accordingly, F-atom concentration may be determined in the presence of F₂ by addition of an excess amount of HCl, thereby converting the F present to HF, and measurement of the amount of HF present by laser optical absorption methods. This alternative (to ESR) technique is important with regard to evaluating HF/DF chemical laser systems where F and F₂ are present.     

HCl存在下CeO2基催化剂上乙烷氧化脱氢制乙烯

报道了一种HCl存在时温和条件下的乙烷氧化脱氢制乙烯催化转化新途径. 研究发现,在多种金属氧化物催化剂中,CeO₂呈现最佳乙烯生成的催化性能. 与纳米粒子相比,具有棒状和立方体状形貌的CeO₂纳米晶具有较高的乙烷转化率和乙烯选择性. 以MnO_x修饰CeO₂可进一步提高催化性能. 在8 wt% MnO_x-CeO₂催化剂上,723K反应2 h时乙烷转化率和乙烯选择性分别为94%和69%. 该催化剂性能稳定,反应100 h乙烯收率可保持在65%-70%. HCl的存在对乙烯的选择性生成起着至关重要的作用,一部分乙烯来自于氯乙烷的脱HCl反应.     

Mechanism of the catalytic action of the mechanoactivated salt K2PTCL4 in the gas-phase hydrochlorination of acetylene

A heterogeneous catalyst for the hydrochlorination of acetylene by gaseous HCl is formed as a result of mechanical treatment of the solid salt K₂PtCl₄ in an atmosphere of acetylene, ethylene, or propylene by the formation of π complexes of platinum(II) as active centers in the surface layer under these conditions. The controlling stage of the catalytic reaction is chloroplatination of the π-coordinated acetylene by the HCl molecule. The reaction takes place as a concerted process, in which an intermediate β-chlorovinyl derivative of platinum(II), a complex of platinum with a coordination vacancy[PtCl ₃ ^* ]⁻, and a new molecule of HCl are formed simultaneously with cleavage of the H—Cl and Pt—Cl bonds in the metal complex adjacent to the π-acetylene complex. The catalytic cycle closes with rapid dissociation of the organoplatinum intermediate by the action of HCl, giving the final product and the initial complex [PtCl₄]²⁻. __________ Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 42, No. 5, pp. 306–311, September–October, 2006.     

Studies on the influence of vibrational excitation of CF2Cl* radicals on the rate of their reaction with HCl

A method is proposed for studying the influence of vibrational excitation of radicals on their reactivity in bimolecular reactions. Investigations of the reaction CF₂Cl + HCl → CF₂ HCl + Cl by this method show for the first time that this reaction is accelerated by vibrational excitation of CF₂Cl* radicals. Under the experimental conditions, it was found that k^*₁/k₁ ? 6.0.     

Measurement of reaction rate of HCl(υ = 1) with oxygen atoms

Relative rate constants k₂/k₁ for the reaction of vibrationally excited HCl(υ = 1) with oxygen atoms HCl(1)+O → OH+Cl, (k₂) to the reaction HCl(0)+O → OH+Cl, (k₁) was measured in a flow system (1–2 torr) at room temperature. Vacuum UV resonance fluorescence was used for the detection of the product chlorine atoms, combined with infrared fluorescence to follow the HCl (υ = 1) decay. In this way vibrational relaxation by oxygen atoms could be excluded from the pure chemical reaction rate. The measured ratio k₂/k₁ is 300 ± 100.     

Product Determination of Gaseous Radical Reactions Using Matrix Isolation-Ftir Detection

The matrix isolation technique with Fourier transform infrared detection has been applied to determine the products of gaseous radical reactions. The gas phase reactions were carried out in a discharge flow system and about 1% of the gas mixture was deposited onto a low temperature target through a pinhole. A differential pumping scheme was employed to maintain the pressure of the cryosystem below 10^?5 torr while that of the flow system was kept at about 2 torr. Species including HO₂ (from the H+O₂ reaction), ClO₂ (from the Cl+O₂ reaction) and ClO (from the Cl+O₃ reaction) have been produced in the gas phase and were successfully trapped in matrices and detected with an FTIR spectrometer. In addition, both HCl and HOCl have been detected as the reaction products from the gaseous ClO+HO₃ reaction. The production of HCl from the ClO+HO₂ reaction may have a significant impact on catalytic ozone destruction in the atmosphere.     

Stereoselective ring-opening reactions with AcBr and AcCl. A new method for preparation of some haloconduritols

The actions of AcX (X=Br, Cl) on 7-oxa-bicyclo[2.2.1]hept-5-ene-2,3-diol diacetates and a transoid-epoxide prepared from the acetonide of cyclohexa-3,5-diene-cis-1,2-diol were studied. H₂SO₄-catalyzed cleavage of exo-cis-7-oxa-bicyclo[2.2.1]hept-5-ene-2,3-diol diacetate with AcCl gave (1α,2α,3α,6β)-6-chloro-4-cyclohexene-1,2,3-triol triacetate, from which the corresponding chloroconduritol was obtained by trans-esterification (MeOH/HCl). A similar reaction of the exo-diacetate with AcBr in the presence of H₂SO₄ resulted in bromine addition. The formation of bromine from the reaction of AcBr and H₂SO₄ was observed by independent experiments. H₂SO₄-catalyzed reaction of endo-cis-7-oxa-bicyclo[2.2.1]hept-5-ene-2,3-diol diacetate with AcX (X=Br, Cl) gave (1α,2α,3β,6β)-6-halo-4-cyclohexene-1,2,3-triol triacetates. The reaction of the transoid-epoxide with AcX (X=Br, Cl) with no catalyst gave also (1α,2α,3β,6β)-6-halo-4-cyclohexene-1,2,3-triol triacetates.     

Oxidative Dehydrogenation of Ethane to Ethylene over LiCl/MnOx/PC Catalysts

The catalytic stability of LiCl/MnO_x/PC catalyst have been investigated, the deactivation mechanism was discussed. The experimental results show that ethane conversion decreases and ethylene selectivity keeps about 90% as reaction time increases. The main deactivation reasons of LiCl/MnO_x/PC catalyst for oxidative dehydrogenation of ethane (ODHE) to ethylene are the transition of active species Mn₂O₃ to MnO species and the loss of active component Cl in catalyst. Instead of ethane with FCC tailed‐gas, the stability of LiCl/MnO_x/PC catalyst has been largely improved.     

Dichlorosilylene–hydrogen chloride complex: direct IR spectroscopic detection in argon matrix

A 1: 1 donor–acceptor complex between SiCl₂ and HCl was detected by matrix IR spectroscopy. The existence of the complex was previously predicted theoretically in the course of analysis of mechanisms of chemical vapor deposition (CVD) processes involving chlorosilanes. The quantum chemical calculations at the G4(MP₂) level confirmed the possibility of formation of only one stable complex upon the reaction of SiCl₂ with HCl. In addition to the complex of the simplest composition, complexes of SiCl₂ with HCl associates were observed upon matrix annealing. The only product formed upon the photolysis of the complexes of all types was trichlorosilane, a product of silylene insertion into the H–Cl bond.

     

钼多金属氧酸盐催化微晶纤维素水解制备葡萄糖的研究

合成了8种基于Mo₈O₂₆的钼多金属氧酸盐,采用红外(FT-IR)和核磁共振(NMR)对其结构进行表征,并将其应用于催化纤维素水解。以离子液体1-烯丙基-3-甲基咪唑氯盐([Amim]Cl)为溶剂进行微晶纤维素(MCC)水解反应,考察催化剂及其用量、反应温度、反应时间等条件对水解反应的影响。研究结果表明,本文所制备的钼多金属氧酸盐对微晶纤维素水解反应均具有较好的催化活性。在微波辅助加热条件下,当催化剂[(CH₃)₄N]₄Mo₈O₂₆用量为10 wt%,在170 ℃反应20 min时,纤维素可完全转化,微晶纤维素TRS和葡萄糖收率最高分别为84.5% 和41.5 %。     

Study of the Stabilization of Polyvinyl Chloride) by Using Model Molecules. VI. Mechanism of Reactions of Aminocrotonate Esters

The mechanism of reaction of the β-aminocrotonate of butanediol (βACB) with 4-chloro-2-hexene (4C2H), a model compound for the allylic chlorine in polyvinyl chloride), was studied in THF or dichloroethane at 60°C by gas and liquid chromatography. The reaction, which needs ZnCl₂ as a catalyst, leads to substitution products through the primary amine group and the hydrogen atom of the trisubstituted double bond. βACB reacts with HCl to give NH4Cl and a set of complex organic products. NH₄Cl and the substitution products are able to complex ZnCl, inhibiting its catalytic activity. In combination with other stabilizers, βACB strongly induces the substitution reaction versus the dehydro-chlorination. In the polymer at 190°C, it increases very much the time of action of the stabilizers; it acts as an HC1 acceptor but also it may be substituted on the polymer even without catalysts. Synergistic effects are observed with epoxy compounds or indole derivatives.     

Total oxidation of chlorinated hydrocarbons on LaMnO3 perovskite type catalyst

The total oxidation of CH₃Cl, CH₂Cl₂ and ClH₂C-CH₂Cl has been investigated on a LaMnO₃ perovskite type catalyst. Depending on the reaction temperature, a reversible deactivation of the catalyst was observed. Small amounts of by-products were formed at low reaction temperatures.     

Biphasic ethylene polymerisation using ionic liquid over a titanocene catalyst activated by an alkyl aluminium compound

1-n-Butyl-3-methylimidazolium tetrachloroaluminate ([BMIM]⁺[AlCl₄]⁻) was applied to biphasic ionic liquid/hexane ethylene polymerisation as a medium of the Cp₂TiCl₂ titanocene catalyst activated by alkylaluminium compounds (MAO, AlEt₂Cl, AlEt₃). The best results were obtained using AlEt₂Cl. The results show that catalyst recycling, higher ethylene pressure, and greater Al/Ti molar ratio along with a greater volume of the ionic liquid phase enhance catalyst activity. The polyethylene gathered from the hexane phase is characterised primarily by its high purity. Its physical properties remain polyethylene obtained over a heterogeneous metallocene catalyst. Thus, biphasic ionic liquid polymerisation using a metallocene catalyst is possible and offers interesting technological implications.     

Theoretical Investigation of Reverse Water Gas Shift Reaction Catalyzed by Ruthenium Halogen Carbonyl Complexes

In this paper we present theoretical study of the reverse water gas shift (RWGS) reaction catalyzed by ruthenium halogen carbonyl complexes. Three mechanisms, including hydrogen chloride, formic acid and oxidation–reduction mechanism, have been explored by density functional theory. The calculations indicate that the oxidation–reduction mechanism contributes to the TDI and TDTS in the ESM TOF calculations. Bimetallic catalysts would be likely to be more highly active than monometallic catalyst for the RWGS reaction. Among bimetallic catalysts studied, both bimetallic catalysts [Ru(μ-Cl)Cl(CO)₃]₂ and [Ru(μ-CO)Cl(CO)₃]₂ shows higher activity than [Ru(μ-Cl)(CO)₄]₂ catalyst with [Ru(μ-CO)Cl(CO)₃]₂ considering as the most efficient catalyst for RWGS reaction.     

KCl对Cu-K-La/γ-Al2O3催化剂上HCl氧化反应性能的影响

采用等体积浸渍法制备了Cu-K-La/γ-Al₂O₃催化剂,考察了KCl对该催化剂催化HCl氧化制Cl₂反应性能的影响. 当KCl的负载量为5 wt%时,Cu-K-La/γ-Al₂O₃催化剂表现出较好的催化活性和稳定性,可在较大的原料气空速变化范围内使用. 在0.1 MPa,360 ℃,空速450 L/（kg-cat·h）和HCl/O₂摩尔比为2：1的反应条件下,Cu-K-La/γ-Al₂O₃催化剂上HCl转化率在100 h内保持85%以上. 表征结果表明,Cu,K和La物种均高度分散于γ-Al₂O₃载体表面;一定量KCl的加入可降低Cu²⁺ → Cu⁺的还原温度,从而提高Cu²⁺活性中心的催化活性.     

Catalytic combustion of soot

The OCM reaction in the presence of HCl over NaCl−MnO/H−ZSM catalyst at 750°C has been studied. Effect of HCl partial pressure on the CH₄ conversion and selectivities to principal products, also on the time-on-stream of catalyst has been examined. Addition of HCl into initial methane-oxygen mixture can increase selectivity to C₂₊ formation and ethene selectivity, in particular. It seems that the time-on-stream of this catalyst is nearly 35–40 h in the presence of HCl.     

Pyrolysis of methyl chloride,a pathway in the chlorine-catalyzed polymerization of methane

The reaction of CH₄ + Cl₂ produces predominantly CH₃Cl + HCl, which above 1200 K goes to olefins, aromatics, and HCl. Results obtained in laboratory experiments and detailed modeling of the chlorine-catalyzed polymerization of methane at 1260 and 1310 K are presented. The reaction can be separated into two stages, the chlorination of methane and pyrolysis of methylchloride. The pyrolysis of CH₃Cl formed C₂H₄ and C₂H₂ in increasing yields as the degree of conversion decreased and the excess of methane increased. Changes of temperature, pressure, or additions of HCl had little effect. In the absence of CH₄ C₂H₄ and C₂H₂ are formed by the recombination of ?H₃ and ?H₂Cl radicals. With added CH₄ recombination of ?H₃ forms C₂H₆, which dehydrogenates to C₂H₄ + H₂. C₂H₄ in turn dehydrogenates to C₂H₂ + H₂. While HCl, C, CH₄, and H₂ are the ultimate stable products, C₂H₄, C₂H₂, and C₆H₆ are produced as intermediates and appear to approach stationary concentrations in the system. Their secondary reactions can be described by radical reactions, which can lead to soot formation. ?H₃ - initiated polymerization of ethylene is negligible relative to the ?₂H₃ formation through H abstraction by Cl. The fastest reaction of ?₂H₃ is its decomposition to C₂H₂. About 20% of the consumption of C₂H₂ can be accounted for by the addition of ?₂H₃ to it with formation of the butadienyl radical. The addition of the latter to C₂H₂ is slow relative to its decomposition to vinylacetylene. Successive H abstraction by Cl from C₄H₄ leading to diacetylene has rates compatible with the experimental values. About 10% of ?₄H₅ abstracts H from HCl and forms butadiene. Successive additions of ?₂H₃ to butadiene and the products of addition can account for the formation of benzene, styrene, naphthalene, and higher polyaromatics. The following rate parameters have been derived on the basis of the experimentally measured reaction rates, the estimated frequency factors, and the currently available heat of formation of the ?₂H₃ radical (69 kcal/mol):      

单分子水对H_2O_2+Cl气相反应影响的理论研究

在aug-cc-pVTZ基组下采用CCSD(T)和B3LYP方法,研究了H2O2+Cl反应,并考虑在大气中单个水分子对该反应的影响.结果表明,H2O2+Cl反应只存在一条生成产物为HO2+HCl的通道,其表观活化能为10.21kJ·mol-1.加入一分子水后,H2O2+Cl反应的产物并没有发生改变,但是所得势能面却比裸反应复杂得多,经历了RW1、RW2和RW3三条通道.水分子在通道RW1和RW2中对产物生成能垒的降低起显著的负催化作用,而在通道RW3中则起明显的正催化作用.利用经典过渡态理论(TST)并结合Wigner矫正模型计算了216.7-298.2 K温度范围内标题反应的速率常数.结果显示,298.2 K时通道R1的速率常数为1.60×10-13cm3·molecule-1·s-1,与所测实验值非常接近.此外,尽管通道RW3的速率常数kRW3比对应裸反应的速率常数kR1大了46.6-131倍,但该通道的有效速率常数k'RW3却比kR1小了10-14个数量级,表明在实际大气环境中水分子对H2O2+Cl反应几乎没有影响.     

Metal‐Free Dehydrogenation of Amine‐Boranes by Tunable N‐Heterocyclic Iminoboranes

We report the synthesis of structurally tunable boron complexes supported by N‐heterocyclic imine ligands IPr=N?BR₂ (IPr=[(HCNDipp)₂C], Dipp=2,6‐iPr₂C₆H₃, R=Cl and/or Ph) that have the ability to abstract dihydrogen from amine‐boranes, and instigate their dehydrocoupling. In one instance, mild heating of the hydrogen addition product IPr=NH?B(Ph)HCl releases H₂ to regenerate the starting N‐heterocyclic iminoborane; accordingly IPr=N?B(Ph)Cl can be used as a metal‐free catalyst to promote the dehydrocoupling of MeNH₂ ? BH₃ to yield N‐methylaminoborane oligomers [MeNH‐BH₂]_x.