Membranes for separation of higher hydrocarbons from methane

In the search for a membrane material capable of separating higher hydrocarbons from methane about 40 different polymers were tested. The most promising two, polyoctylmethylsiloxane (POMS) and polytrimethylsilylpropyne (PTMSP), are compared in this article to the standard material polydimethylsiloxane (PDMS).     

Direct catalytic synthesis of ethylene from methane

Ethylene synthesis from methane has been studied over multifunctional catalysts. It is proposed that the formation of an active precursor, produced by carbon deposition, is necessary for ethylene production to occur.

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Non-oxidative dehydro-oligomerization of methane to higher molecular weight hydrocarbons at low temperatures

The non-oxidative dehydro-oligomerization of methane to higher molecular weight hydrocarbons such as aroma tics and C2 hydrocarbons in a low temperature range of 773-973 K with Mo/HZSM-5,Mo-Zr/HZSM-5 and Mo-W/HZSM-5 catalysts is studied.The means for enhancing the activity and stability of the Mo-containing catalysts under the reaction conditions is reported.Quite a stable methane conversion rate of over 10% with a high selectivity to the higher hydrocarbons has been obtained at a temperature of 973 K.Pure methane conversions of about 5.2% and 2.0% have been obtained at 923 and 873 K,respectively.In addition,accompanied by the C2-C3 mixture,tht- methane reaction can be initiated even at a lower temperature and the conversion rate of methane is enhanced by the presence of tne initiator of C2-C3 hydrocarbons.Compared with methane oxidative coupling to ethylene,the novel way for methane transformation is significant and reasonable for its lower reaction temperatures and high selectivity to the desired prod     

Influence of the composition of Co-containing perovskites on their catalytic properties in the conversion of methane into higher hydrocarbons in non-stationary conditions

The oxidative coupling of methane in a periodic regime was studied using Co-containing perovskites as solid oxidants. Partial substitution of strontium with alkali metals in the perovskite SrCoO₃ increased the activity and selectivity of the catalyst with respect to higher hydrocarbons. The substituted catalysts continued to work after many oxidation-reduction cycles. L. V. Pisarzhevskii Institute of Physical Chemistry, National Academy of Sciences of Ukraine, 31 Prospekt Nauki, Kiev 252039, Ukraine. Translated from Teoreticheskaya i éksperimental'naya Khimiya, Vol. 36, No. 1, pp. 47–52, January–February, 2000.     

Direct conversion of methane to higher hydrocarbons using AlBr3-HBr superacid catalyst

The direct gas phase catalytic oligomerization of methane at temperatures ≤673 K has been demonstrated using AlBr(3)-HBr superacid. The reaction produces C(2)+ hydrocarbons and hydrogen in a single step at 1 atm in a continuous flow reactor at a nominal residence time of 60 s. The essentially complete conversion of methane appears to be due to protolytic activation of methane in the presence of H(+)AlBr(4)(-).     

High separation capacity and selectivity of C2 hydrocarbons over methane within a microporous metal-organic framework at room temperature

A separation story! A microporous metal-organic framework (UTSA-34) of non-interpenetrated binodal (4,6)-connected ybh network with interconnected cages of about 12.8?? has been realised to exhibit highly selective separation of C(2) hydrocarbons from methane with a separation capacity of 3.0?mol kg(-1) and selectivity of 35 at room temperature (see figure).     

Effect of doping fulllerene soots with metals on the conversion of methane into higher hydrocarbons

We have previously demonstrated that fullerene soots catalyze hydrogen-transfer reactions that are useful for hydrocarbon processing, including conversion of methane into higher hydrocarbons. In this paper we describe the effect of doping fullerene soot with alkali and transition metals for converting methane and other light hydrocarbons. The fullerene soot was found to lower the temperature threshold for methane activation compared to other carbons; however, the selectivity to C₂ hydrocarbons was quite low (20%). In contrast, when the soot was doped with metals such as Mn or K, the overall yield of hydrocarbons increased and selectivities as high as 80% were achieved. When potassium was used as a dopant, the selectivity to C₃ and C₄ hydrocarbons also increased.     

Investigation of catalytic purification of gases from aromatic hydrocarbons

1,1- (AH) ([AH]=6,9 /, 50°C). AH W_i/W_{O 3}=0,40±0,16.

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The kinetics and oxidation products of 1,1-diethoxyethane (AH) ozonolysis have been investigated at [AH]=6.9 mol/l and 50 °C. The initiation efficiency of radical oxidation by ozone is W_i/W_{O 3}=0.40±0.16.

     

Characteristics of the catalytic action of Co systems in the synthesis of hydrocarbons from Co and H2

Conclusions On the basis of experimental data, assumptions have been made concerning the possibility of prediction of the properties of Co catalysts for the synthesis of hydrocarbons from carbon monoxide and hydrogen with due regard for the properties of the supports, the nature of the thermodesorption of CO from the surface of the catalyst, and the method of its preparation.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 1, pp. 60–66, January, 1984.     

反应器型式对甲烷低温等离子体转化制C2烃的影响

就不同反应器对甲烷常压低温等离子体转化制C2烃的影响进行了研究。结果表明,相同的甲烷停留时间和相同甲烷流率下,反应器A和B中反应的主要产物是乙炔,乙烯和乙烷的含量较少,积炭量较多;而反应器C和D中反应的主要产物为乙烷和丙烷,乙烯和乙炔含量较少,积炭量很少。反应积炭对反应器A中甲烷转化率影响很大,对于产物选择性影响不大,而对反应器C中的反应影响较小。根据产物分布可知,在反应器A和B中,由于电子具有很高的能量和密度,甲烷主要解离为碳原子;而在反应器C及D中,由于电子能量和密度较低,甲烷主要解离为CH3自由基。     

Direct laser-chemical sensitized synthesis of formaldehyde from methane

An original method is proposed for the direct oxidation of methane to formaldehyde at room temperature and atmospheric pressure by atmospheric oxygen, under the action of a continuous tunable CO₂ laser. The synthesis is accompalished by a sensitized laser-chemical reaction due to intermodal vibrational activation of methane by V-V exchange with the sensitizer.Institute of General and Inorganic Chemistry, Ukrainian Academy of Sciences, Kiev. Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 27, No. 6, pp. 730–733, November–December, 1991. Original submitted March 27, 1991.     

Kinetics of catalytic oxidation of methane

A kinetic model for methane oxidation in sulfur dioxidecontaining gaseous mixtures at 640–830 °C with Al₂O₃ as catalyst is suggested.     

异龙脑气相催化法合成樟脑

本文研究了异龙脑气相催化脱氢生成樟脑过程，筛选出催化剂金属氧化物CDH。反应温度在240℃时，催化剂CDH有良好的选择性和较高的反应活性、稳定性。本实验结果：樟脑产率达96％，樟脑纯度为98％（熔点176℃）。     

High temperature normal phase liquid chromatography of aromatic hydrocarbons on bare zirconia

The normal phase HPLC behavior of a bare zirconia column was studied at temperatures up to 200 °C using a hexane mobile phase. The use of elevated column temperatures significantly decreased the retention of twenty five aromatic model compounds according to the van't Hoff equation (>30-fold decrease for some compounds). Large improvements in peak shape, efficiency (>2.2-fold), aromatic group-type selectivity, and column re-equilibration times (>5-fold) were obtained at elevated temperatures. The thermal decomposition of two polar nitrogen compounds (indole and carbazole) was observed in a hexane/dichloromethane mobile phase at temperatures greater than 100 °C. The first order decomposition of carbazole was studied in further detail.     

Monolithic reactors for experimental studies of the catalytic partial oxidation of methane to synthesis gas

Monoliths containing 0.1 wt.% Pt and Rh have been used for the partial oxidation of methane to synthesis gas. Two different impregnation methods for making Pt and Rh (and Ni) monoliths are described and discussed. The studies were carried out at conditions with incomplete conversion of O₂ and with product distributions far from equilibrium. The two metals show different activities.     

Dehydrocondensation of methane to higher hydrocarbons on bifunctional catalysts in the absence of oxidizing agents in the gas phase

A study was carried out on the effect of the chemical nature of M_xL_y on the activity and selectivity of bifunctional M_xL_y/zeolite catalysts, where M_xL_y are metal-like transition metal compounds, M is a metal atom (Co, Mo, or W), and L is a nonmetal atom (B or Si), in the dehydrocondensation of methane to give higher hydrocarbons in the absence of gas-phase oxidizing agents. L. V. Pisarzhevskii Institute of Physical Chemistry, National Academy of Sciences of Ukraine, 31 Prospekt Nauki, 252039 Kiev, Ukraine. Translated from éksperimental’naya i Teoreticheskaya Khimiya, Vol. 33, pp. 243–247, July–August, 1997.     

Reaction of nitrous oxide with methane to synthesis gas: A thermodynamic and catalytic study

The aim of the present study is to explore the coherence of thermodynamic equilibrium predictions with the actual catalytic reaction of CH4 with N_2O,particularly at higher CH4 conversions.For this purpose,key process variables,such as temperature(300℃-550℃) and a molar feed ratio(N_2O/CH4 = 1,3,and 5),were altered to establish the conditions for maximized H_2 yield.The experimental study was conducted over the Co-ZSM-5 catalyst in a fixed bed tubular reactor and then compared with the thermodynamic equilibrium compositions,where the equilibrium composition was calculated via total Gibbs free energy minimization method.The results suggest that molar feed ratio plays an important role in the overall reaction products distribution.Generally for N_2O conversions,and irrespective of N_2O/CH_4 feed ratio,the thermodynamic predictions coincide with experimental data obtained at approximately 475℃-550℃,indicating that the reactions are kinetically limited at lower range of temperatures.For example,theoretical calculations show that the H2 yield is zero in presence of excess N2O(N_2O/CH_4 = 5).However over a Co-ZSM-5 catalyst,and with a same molar feed ratio(N_2O/CH_4) of 5,the H_2 yield is initially 10%at 425℃,while above450℃ it drops to zero.Furthermore,H_2 yield steadily increases with temperature and with the level of CH4 conversion for reactions limited by N_2O concentration in a reactant feed.The maximum attainable(from thermodynamic calculations and at a feed ratio of N_2O/CH4=3) H_2 yield at 550℃ is 38%,whereas at same temperature and over Co-ZSM-5,the experimentally observed yield is about 19%.Carbon deposition on Co-ZSM-5 at lower temperatures and CH4 conversion(less than 50%) was also observed.At higher temperatures and levels of CH_4 conversion(above 90%),the deposited carbon is suggested to react with N_2O to form CO_2.