The effect of heavy aromatic sulfur compounds on sulfur in cracked naphtha

The scope of the present study was to elucidate the effect of heavy sulfur compounds, commonly found in the gas oils, on the percentage of sulfur in gasoline range during the Fluid Catalytic Cracking (FCC) process. Five model sulfur compounds commonly found in the gas oils were studied: benzothiophene, 2-methyl-benzothiophene, 3-decyl-thiophene, dibenzothiophene and 4,6-dimethyl-dibenzothiophene. In order to maintain a realistic hydrocarbon environment each one of the heavy sulfur model compounds were diluted in conventional gas oil. Their cracking behaviour were studied using a steamed deactivated FCC catalyst, while the run tests were performed in an automated Short Contact Time Microactivity Test Unit (SCT-MAT) operated at 560 °C and 12 s run time. The experimental results indicated that the long chain alkyl-thiophene (3-decyl-thiophene) is mainly responsible for the increase of sulfur amount in the gasoline range during cracking, through dealkylation and side cracking reactions for the production of thiophene and shorter chain alkyl-thiophenes, respectively. That sulfur compound was also the most reactive one with respect to desulfurization, since it was highly cracked to H₂S and decomposed to S in coke. On contrary, the polycyclic sulfur compounds did not affect the sulfur amount in gasoline, while their reactions were strongly related to their chemical structure. Thus, the main reaction pathway of the alkylated 2-methyl-benzothiophene and 4,6-dibenzothiophene during the FCC process was isomerization, while for benzothiophene and dibenzothiophene alkylation reactions were dominated.     

Pyrolysis studies of some simple coal related aromatic methyl ethers

Pyrolysis of the coal related model compounds o-, m-, and p-hydroxy and methoxyanisoles has been studied under inert atmosphere at reaction temperatures from 598 to 673 K, and for reaction times from 1 to 600 min. The thermal decomposition of all these anisoles takes place via two main primary pathways, namely by demethylation of the methoxyl groups, and by an intramolecular ipso substitution of the methoxyl groups via a spiranic oxiran intermediate. The demethoxylation under mild reaction conditions obviously takes place as a secondary reaction via the ipso substitution pathway. The demethylation of o-hydroxyanisole (guaiacol) is partly concerted on the basis of kinetics and of e.p.r. measurements of the residual spin concentration of the pyrolysis products. There is, however, no indication of a concerted mechanism for 0-methoxyanisole (veratrole). The apparent first order activation energy of all the anisoles studied is of the order 240 ± 20 kJ mol⁻¹ corresponding to the average bond energy of the methyl CO bond in the aromatic methoxyl group.     

Purification of hydrocarbons from aromatic sulfur compounds by supercritical carbon dioxide extraction

Supercritical carbon dioxide extraction to purify samples of model hydrocarbons (tetralin, decalin, and tetradecane) containing various aromatic sulfur compounds (benzothiophene, dibenzothiophene, and 4,6-dimethydibenzothiophene) was studied. The influence of extraction temperature and pressure was investigated for the extraction from a tetralin-dibenzothiophene system in the range of 293-353 K and 8-15 MPa, and it was found that the amount of tetralin extracted increased with an increase in carbon dioxide density, while the separation factor decreased with an increase in carbon dioxide density. High recovery and high separation factor values for the tetralin-dibenzothiophene system were obtained under 10 MPa at 313 K. Higher separation factor was obtained for tetralin than decalin and tetradecane, containing 4,6-dimethyldibenzothiophene than that containing dibenzothiophene.     

类煤模型化合物在两种铁基催化剂作用下的热解

选取可以代表真实煤中典型弱键结构的苯乙醚和联苄作为类煤模型化合物,在固定床热解装置上研究了其在黄铁矿(pyrite)和Fe/ZSM-5这两种铁基催化剂作用下的热解行为。结果表明,两种催化剂均可以提高模型化合物的热解转化率,Fe/ZSM-5的催化效果要优于pyrite,在热解过程中明显促进了苯乙醚中C_(aliphatic)—O键和联苄中C_(aryl)—C_(aliphatic)键的断裂;Fe的负载量为7.5%时,Fe/ZSM-5催化效果最好。在苯乙醚热解过程中,Fe/ZSM-5中载体分子筛起主要催化作用;而在联苄的热解过程中,Fe/ZSM-5中负载金属主要起催化作用。     

类煤模型化合物在两种铁基催化剂作用下的热解

选取可以代表真实煤中典型弱键结构的苯乙醚和联苄作为类煤模型化合物,在固定床热解装置上研究了其在黄铁矿(pyrite)和Fe/ZSM-5这两种铁基催化剂作用下的热解行为。结果表明,两种催化剂均可以提高模型化合物的热解转化率,Fe/ZSM-5的催化效果要优于pyrite,在热解过程中明显促进了苯乙醚中C_(aliphatic)—O键和联苄中C_(aryl)—C_(aliphatic)键的断裂;Fe的负载量为7.5%时,Fe/ZSM-5催化效果最好。在苯乙醚热解过程中,Fe/ZSM-5中载体分子筛起主要催化作用;而在联苄的热解过程中,Fe/ZSM-5中负载金属主要起催化作用。     

Pyrolysis of model compounds of the flame retardant poly(N-dimethylphosphonomethyl acrylamide)

An investigation of the thermal decomposition of N-dimethylphosphonomethyl amides has shown that the major volatile products for decomposition above 300°C are methanol, the methyl ester of the carboxylic acid, the nitrile, the carboxylic acid, the N-methyl amide, and the N,N-dimethyl amide. Also, benzoic acid was the only volatile product detected in the decomposition of α-benzamidomethylphosphonic acid. A mass balance for the decomposition of N-dimethylphosphonomethyl benzamide at 420°C showed methanol and methyl benzoate to be the major volatile products. Methanol and benzonitrile formation increased with an increase in temperature at a faster rate than the other volatile products. The reaction of amides and phosphonates was further studied using sealed tubes in a furnace. Reaction of N-methylbenzamide with dimethyl methylphosphonate at 307°C in a sealed tube produced methyl benzoate and N,N-dimethylbenzamide. N,N-dimethylbenzamide and dimethylmethylphosphonate were also shown to produce methyl benzoate at 310°C. After a 5-min period more methyl benzoate was produced in the N,N-dimethylbenzamide reaction than in the N-methylbenzamide reaction. Also, addition of ethanol to the N,N-dimethylbenzamide/dimethyl methylphosphonate reaction resulted in less ethyl benzoate methyl benzoate after heating at 310°C.     

Some thermal studies on polystyrylpyridine resins and related model compounds

Five model compounds representing part of the structure of polystyrylpy-ridines have been studied using differential scanning calorimetry (DSC) and pyrolysis-gas chromatography-mass spectrometry (P-GC-MS). Cured resin samples have also been examined by pyrolysis-gas chromatography-mass spectrometry and thermogravimetry. DSC showed that, with one exception, all the model compounds were crystalline as supplied and recrystallisation occurred readily on melting and cooling. The breakdown products in P-GC-MS, with the exception of 1-methyleneindene (produced from three of the model compounds), could all be explained on the basis of general bond scission followed by H or C₆H₅ transfer. Thermogravimetry indicated the minimum cure cycle necessary to give optimum thermal stability on a weight loss basis.     

生物质模化物催化热解制取烯烃和芳香烃

采用愈创木酚作为生物质模型化合物,以ZSM-5为催化剂,在固定床反应器中研究了反应温度、质量空速以及分压对热解产物产率、选择性的影响,并考察了催化剂的积炭情况。结果表明,愈创木酚催化热解的主要产物为酚类,其次是芳香烃。温度对产物分布有显著影响。催化剂适量的积炭有利于提高烯烃和芳香烃的产率。根据愈创木酚催化热解反应产物分布,推测其主要反应为脱除甲氧基形成酚类,进一步芳构化形成芳香烃。本文研究结果为研究生物质催化热解反应机理提供了理论依据。     

Bi-phasic bio-conversion of sulfur present in model organo-sulfur compounds and hydro-treated diesel

Bacterial strain of Rhodococcus sp. (JUBT1) isolated from petrol/diesel station has been used for the desulfurization of different model organo-sulfur compounds like DBT, substituted DBT, etc. which are difficult to remove in the conventional hydro-desulfurization of diesel fraction. The initial concentration of organo-sulfur compounds has been varied in the range of 100–1000 mg/dm³. Under the present experimental range, the bacterial growth has been observed to follow Haldane-type kinetics characterizing the presence of substrate inhibition. The extent of inhibition by the substrate has been observed to increase with the number of substituents in the same range of initial concentration of different organo-sulfur compounds. The values of intrinsic kinetic parameters, like maximum desulfurization rate, v_max, half saturation constant, K_S, inhibition constant, K_Si and the maximum substrate concentration, C_Smax, corresponding to the maximum uninhibited rate of desulfurization, have been determined using each organo-sulfur compound having different number of substituents as limiting substrate. Relative changes in the values of the kinetic parameters have been correlated to the number of substitutions. Separate studies have also been conducted to determine the kinetics of bio-desulfurization of a hydro-treated diesel fraction. The concentration of sulfur in diesel was selected in the range of 100–500 mg/dm³.

The effect of aqueous to non-aqueous ratio on the rate of specific desulfurization of hydro-treated diesel fraction in the range from 1:9 to 9:1 has also been studied in the present investigation. Mathematical models have been developed to predict the conversion of sulfur during batch-type bio-desulfurization of model compounds as well as diesel having known distribution of organo-sulfur compounds. The predictions of the model satisfactorily compare with the experimental results.     

Sulfur-bridged polycyclic aromatic compounds

When polycyclic aromatic hydrocarbons are heattreated with an excess amount of sulfur in evacuated closed tubing, they react with sulfur, liberating hydrogen sulfide; after removing unreacted sulfur, dark-colored compounds in the form of an amorphous solid are obtained. These compounds possess semiconductive properties; the electrical resistivity is greatly reduced from that of the original hydrocarbons. The ESR absorption of these compounds is characterized by the large g-value, which is due to sulfur-centered unpaired electrons.From these findings, with the results of chemical analysis, we can assume that the polycyclic aromatic nuclei crosslink with each other through the sulfur-bridges, which are good electron transport paths, and yield the aromaticity of the molecule. The sulfur-bridged polycyclic aromatic hydrocarbons can be considered as the structural model of chars and cokes. The ESR studies of a violanthrene-sulfur compound were carried out during its heat-treatment up to 1000°C.     

沥青热解模型

沥青是制备炭材料的重要前驱体之一,深入理解其炭化行为有助于控制炭产品性能。采用峰值分离的方法对沥青的DTG曲线进行分解,得到3个部分交叠的温度区间,用三阶段连续伪组分反应动力学模型拟合发现,3个阶段均是一级反应。并对2.5 K/m in至10 K/m in加热速率下的热质量损失曲线进行计算,结果与实验数据吻合良好。对炭化过程中挥发分形成的气泡的生长动力学进行理论计算,结果表明,气泡的直径随温度升高单调增加,沥青的热解质量损失率是气泡生长的控制因素。相同热解温度下,气泡外围的液体径向速度随加热速率的增加而成倍增加,因此加热速率应该遵循"两头快,中间慢"的原则。     

Reduction of aromatic compounds by potassium-graphite intercalation compounds

The interaction is investigated between aromatic compounds (polynuclear hydrocarbons, aryl substituted ethenes, hydrocarbons with a mobile hydrogen atom, aromatic nitriles and ketones) and the binary potassium-graphite intercalation compound-KC₂₄-in solvating solvents (tetrahydrofuran or dimethoxyethane). The amount of potassium extracted from the graphite intercalation compound as potassium compounds depends on the electron affinity of the aromatic molecule. The reduction products are anion-radicals, anions or dianions depending on the nature of the aromatic compounds. A tentative mechanism of the reduction of the aromatic molecules by KC₂₄ is discussed.     

Pyrolysis of model compounds on spent oil shales, minerals and charcoal: Implications for shale oil composition

Aliphatic compounds (alkanes, alkenes, alkanoic acids, ketones, alcohols and amines) were passed through beds of spent oil shales (Condor brown, Condor carbonaceous, Julia Creek), minerals (quartz, calcite, K-feldspar, pyrite, kaolinite) and charcoal at temperatures of 300–600 °C and the products were analysed by g.c.m.s. All the materials catalysed isomerization, aromatization and cracking to varying degrees: non-clay minerals < kaolinite ≈ spent oil shales < charcoal. Products included branched alkanes, isomeric alkenes, nitriles, ketones and alkyl-substituted benzenes, naphthalenes, pyridines, phenols, thiophenes and pyrroles. These compounds occur in shale oils and may be derived from secondary reactions of aliphatic products arising from kerogen cracking.     

芳香硝基化合物的氟化

从反应原理、催化剂的选择、副反应的发生与控制等方面综述了芳香硝基化合物直接氟化的研究进展，阐述了硝基氟化的意义及应用重要性，介绍了硝基氟化的最新研究与发展方向。     

Electrochemical studies of gold ore processing wastewater containing cyanide, copper, and sulfur compounds

The electrochemistry of real gold ore processing wastewater solutions from copper sulfide containing gold ore has been investigated. Analysis shows that the wastewater contains a range of sulfur compounds in various oxidation states from sulfide to sulfate. The electrochemical characteristics of the gold ore processing wastewater were evaluated using rotating disk, cyclic voltammetric, polarization and preparative electrolysis studies. The solutions show clear differences versus synthetic alkaline copper cyanide solutions. The copper cyanide/copper oxide catalysis normally seen in synthetic alkaline copper cyanide solutions is strongly inhibited. Two components of the wastewater solution identified as inhibiting the copper cyanide/copper oxide catalysis are copper sulfide complexes and thiocyanate. The inhibition of the copper cyanide/copper oxide catalysis appears to have an initiation time possibly related to the accumulation of copper-sulfur compounds at the electrode surface. The passivated surface is still able to oxidize cyanide, though at a maximum rate that corresponds to the limiting current for free cyanide assuming 1 electron per cyanide. The lack of the copper oxide coating that typically forms during oxidation of synthetic alkaline copper cyanide solutions, plus possibly the presence of various sulfur compounds, results in corrosion at higher anodic potentials when stainless steel is used as an electrode. However, stainless steel can be successfully used as an electrode material to treat the solutions if the potential is carefully controlled.     

芳香族硝基化合物定量分析技术的研究

综述了近年来国内外芳香族硝基化合物检测方法的应用实例与研究进展,并对各方法适用条件、检测限、检测范围、优势与不足等方面进行了介绍。旨在为各种芳香族硝基化合物的检测与定量分析提供参考,并对分析方法发展趋势做出展望。     

煤矿中硫铁化合物的氧化动力学研究

硫铁化合物氧化放热是引发煤炭自燃的原因之一,运用XRD、TG-DSC技术分析硫铁化合物的热分解过程和非等温热分解机理。研究表明,硫铁化合物分解包括3个阶段:在179.1~287.75℃内逐步进行物相转化,403.5~493.75℃内开始FeS_2的氧化热解,611.65~792.25℃内发生硫酸盐(或亚硫酸盐)逐步分解,热解失重达到最大值。运用Friedma法、Kissinger法、Starink法对非等温动力学数据进行分析,3个阶段的表观活化能分别是96,174,230 k J/mol。各阶段样品稳定性逐渐提高,为硫铁化合物自燃的综合判据提供依据。