Direct hydrogenation of carbons by isothermal microthermogravimetry at atmospheric pressure

The effect of hydrogen partial pressure on the hydrogenation rate of lignite char has been studied at pressures between 0.3 and 1 atm and temperatures between 820 and 940°C by thermogravimetry. The apparent order as a function of hydrogen pressure and the activation energy of this reaction have been determined. Under the experimental conditions investigated in this work, after gasification of about 70% of the lignite char, the hydrogenation rate decreases rapidly.     

RDX flame structure at atmospheric pressure

The chemical structure of an RDX flame at a pressure of 1 atm was studied using probing molecular beam mass spectrometry. The flame was found to contain RDX vapor, and its concentration profile was measured in a narrow zone adjacent to the burning surface. In addition to RDX vapor, ten more species were identified (H₂, H₂O, HCN, N₂, CO, CH₂O, NO, N₂O, CO₂ and NO₂), and their concentration profiles were measured. Two main chemical-reaction zones were found in the RDX flame. In the first, narrow, zone 0.15 mm wide adjacent to the burning surface, decomposition of RDX vapor and the reaction of NO₂, N₂O, and CH₂O with the formation of HCN and NO occur. In the second, wide, zone 0.85 mm wide, HCN is oxidized by NO to form the final combustion products. The composition of the final combustion products was analyzed from an energetic point of view. The measured composition of the products near the burning surface was used to determine the global reaction of RDX gasification at a pressure of 1 atm. Values of heat release in the condensed-phase calculated by the global gasification reaction and by the equation of heat balance on the burning surface (using data of microthermocouple measurements) were analyzed and compared. __________ Translated from Fizika Goreniya i Vzryva, Vol. 44, No. 1, pp. 49–62, January–February, 2008.     

常压脱高硫浅议

就用常压塔脱高硫从流程设置、设备选择、工艺条件控制以及硫回收几方面进行讨论,并着重阐述了脱硫塔、再生槽的设计要求以及吸收、再生、熔硫的工艺条件。     

Transition of graphite into diamond in a solid phase under the atmospheric pressure

Transition of small-size graphite particles into diamond has been experimentally detected under atmospheric pressure. The transformation in a solid phase occurs when graphite heated up to 2500 K is rapidly cooled. Electron and X-ray diffraction methods were applied to investigate the solid-phase transition products. The transition of graphite into diamond may be explained whether by the setting up of high pressures or by retention in quenching the structures that are characteristic for elevated temperatures.     

Carbonation of epoxy methyl soyate at atmospheric pressure

Vegetable oils are important substrates for the development of biobased products that may replace products derived from petroleum. Carbonated methyl soyates were prepared at atmospheric pressures from epoxy methyl soyate by the introduction of carbon dioxide at the oxirane position. Carbonation was performed by sparging carbon dioxide gas through the neat epoxy esters at atmospheric pressure in the presence of tetrabutylammonium bromide catalyst. Analysis of reaction mixtures showed that 42% of the epoxide groups were carbonated after 18 h at 80 degrees C with 1 wt% catalyst compared to 63% using liquid carbon dioxide at 54 atm pressure.     

The catalytic dealkylation of alkylphenols at atmospheric pressure

A comparative survey has been made of alkaline, fluorine-containing, and charcoal-based materials as potential catalysts for the vapour phase dealkylation of alkylphenols. o-Cresol was used as the feed in an initial screening, and those catalysts showing most activity were then subjected to a more detailed study using higher-boiling feedstocks. The most interesting results were obtained using aluminium borofluoride or zinc fluoride, each on a γ-alumina support. In addition to extensive dealkylation, these catalysts also gave rise to isomerising effects. Their activity, however, rapidly declined because of carbon deposition, but could be fully restored by heating in an oxygen/nitrogen stream. The use of metal-impregnated charcoals gave more selective dealkylation than active charcoal alone, but the improvement did not warrant the additional cost; moreover these materials could not be revivified by conventional means. The alkaline catalysts displayed a lower level of activity and could not be completely regenerated after deactivation because of carbonation in addition to carbon deposition.     

减压渣油低压催化加氢轻质化研究

以克拉玛依某炼厂减压渣油为研究对象,在高温高压反应釜(1L)中,以廉价可弃的Fe2O3为催化剂,采用单因素实验方法,考察了反应温度t、氢初压p(H2)和反应时间θ等对其加氢轻质化的影响。结果表明:该油样具备良好的加工性能;降低反应温度、升高氢初压和缩短反应时间,均可降低生焦率;氢初压5 MPa为折点。当氢初压超过5 MPa后,若通过增大氢初压的方式来降低生焦率,是不经济的;反应时间超过75 min,生焦率迅速增大,初步判定反应时间超过75 min,即为超过其生焦诱导期。以Fe2O3为催化剂,该油样加氢轻质化的适宜条件为反应温度θ=445℃,氢初压p(H2)=5 MPa,反应时间t=55 min,此时,η(≤330℃)=64.40%,生焦率6.03%。文章为该减压渣油加氢轻质化实现工业化提供理论依据。     

Special features of nitramine combustion at atmospheric pressure

Results of a study dealing withRDX andHMX combustion using a recoil-force transducer have been presented. Self-sustaining and radiation.-driven combustion regimes have been examined. A high-frequency (over600 Hz) component in the signal of recoil force duringRDX combustion has been detected. The self-sustaining combustion ofHMX has been shown to be of an auto-oscillating character at atmospheric pressure. Special features of the resonant response duringHMX combustion under the action of simulated laser radiation have been examined. Institute of Chemical Kinetics and Combustion, Siberian, Division, Russian Academy of Sciences, Novosibirsk 630090. Translated from Fizika Goreniya i Vzryva, Vol. 33, No. 6, pp. 68–71, November–December, 1997.     

Acetone decomposition by water plasmas at atmospheric pressure

Decomposition of aqueous acetone was performed using a direct current (DC) plasma torch at atmospheric pressure. The torch can generate the plasma with water as the plasma-supporting gas in the absence of any additional gas supply system and cooling devices. The results indicated that 5 mol% acetone was drastically decomposed by water plasmas with energy efficiencies of 1.7×10^?7 mol J^?1. The major products in the effluent gas were H₂ (60–70%), CO₂ (5–16%), CO (6–16%), and CH₄ (0.2–0.9%). However, trace levels of formic acid (HCOOH) and formaldehyde (HCHO) were observed in the liquid effluent. Based on the experimental results and information from the literature, the following decomposition mechanism was proposed for acetone in water plasmas: first, electron dissociation in arc region generates acetyl (CH₃CO) and methyl (CH₃) radicals; then, chemical oxidation or reduction in plasma flow region forms CO and CH_x(x:1–3) radicals there. Finally, the generated intermediate species undergo complex reactions to form stable compounds such as CO in downstream region. However, if little oxygen is present, those intermediate species easily recombine with each other or are oxidized by OH to form unwanted by-products, such as HCOOH and HCHO.     

3,4-二甲基苯甲醛的常压法合成及表征

以邻二甲苯、CO和HCl为原料,以AlCl3为催化剂,经过Gattermann-Koch反应,在常压下合成3,4-二甲基苯甲醛,反应的较佳条件是:n(邻二甲苯)∶n(AlCl3)=1∶1.1,反应温度0⁵℃,反应时间12 h。在此条件下,3,4-二甲基苯甲醛收率约为61%,纯度为98.9%。     

常压下环己烷密度与温度的相关性

以空气和去离子水为标准样,利用振动管密度计测定了常压下环己烷在20~60℃时,几乎每相间1℃密度数据。其中系统温度的控制精度在0.01℃,密度的测量精度为0.000 1 g/cm3。利用3种不同的函数关系,将测量密度与对应温度的数据进行非线性最小二乘法拟合,给出了密度函数的对应参数。对比得出密度与温度间的最优函数关系,用最优函数计算密度的标准误差为0.000 1 g/cm3,符合密度测量精度要求。     

Catalytic wet air oxidation of carboxylic acids at atmospheric pressure

Catalytic wet air oxidation of carboxylic acids (maleic acid, oxalic acid and formic acid) was carried out in a batch reactor operated at 160 psi or atmospheric pressure. Pt/Al₂O₃ and the sulfonated poly(styrene-co-divinylbenzene) resin were used as catalysts. Maleic acid was proved to be a refractory substance which could not be oxidized on the Pt/Al₂O₃ catalyst at all atmoshperic pressure, and needed high pressure and high temperature operation for its oxidation. On the contrary, oxalic acid and formic acid were readily oxidized into carbon dioxide and water at 353 K and atmospheric pressure. The pathways of maleic acid oxidation were proposed, and the conversion of maleic acid into oxalic acid was the rate-determining step. When the sulfonated resin catalyst was present together with the Pt/Al₂O₃ catalyst, maleic acid could be oxidized at 353 K and atmospheric pressure. The sulfonated resin catalyst was suggested to hydrolyze maleic acid into readily oxidizable compounds.     

Continuous slurry hydrogenation of soybean oil with copper-chromite catalyst at high pressure

Selective hydrogenation of soybean oil to reduce linolenic acid is accomplished better with copper than with nickel catalysts. However, the low activity of copper catalysts at low pressure and the high cost of batch equipment for high-pressure hydrogenation has precluded their commercial use so far. To evaluate continuous systems as an alternative, soybean oil was hydrogenated in a 120 ft × 1/8 in. tubular reactor with copper catalyst. A series of hydrogenations were performed according to a statistical design by varying processing conditions: oil flow (0.5 L/hr, 1.0 L/hr and 2.0 L/hr), reaction temperature (180 C and 200 C), hydrogen pressure (1,100 psig and 4,500 psig) and catalyst concentration (0.5% and 1.0%). An iodine value (IV) drop of 8–43 units was observed in the products whereas selectivity varied between 7 and 9. Isomerization was comparable to that observed with a batch reactor. Analysis of variance for isomerization indicated interaction between catalyst concentration and hydrogen pressure and between catalyst concentration and temperature. The influence of pressure on linolenate selectivity was different for different temperatures and pressure. Hydrogenation rate was significantly affected by pressure, temperature and catalyst concentration.     

Formation of diamond and graphite at high pressure using glassy carbon source

Experimental study on diamond and graphite formation with presence of metal catalysts under 6 GPa and 1300–1600 °C was carried out using pyrolyzed furfuryl alcohol resin (glassy carbon) or graphite and Mg(OH)₂ mixture. Diamond was formed from glassy carbon pyrolyzed higher than 1500 °C in vacuum. Graphite crystals were dominantly formed when glassy carbons pyrolyzed below 900 °C or graphite containing Mg(OH)₂ higher than 3 wt.% were used as starting carbons even by long reaction time (28 h) or diamond seeding experiments. Degree of graphitization of glassy carbon with catalyst metal was increased markedly under diamond-forming pressure and temperature condition. It was apparent that the lower degree of graphitization of starting carbon is not an essential factor to prevent diamond formation. The results revealed that graphite crystals were grown when starting carbons contained approximately higher than 1000 ppm of hydrogen. It was suggested that if the metal carbon system contains a higher amount of C–O–H fluid than that of threshold, diamond nucleation was prevented and graphite was dominantly precipitated.