Simultaneous operation of dibenzothiophene hydrodesulfurization and methanol reforming reactions over Pd promoted alumina based catalysts

In the current study simultaneous reactions of hydrodesulfurization(HDS) of dibenzothiophene(DBT) and reforming of methanol in a micro-autoclave reactor were studied over bi-metallic(Co-Mo/Al2O3 and Ni-Mo/Al2O3) and tri-metallic(Pd-Co-Mo/Al2O3 and Pd-Ni-Mo/Al2O3) catalyst systems which were prepared by incipient impregnation method.In situ hydrogen utilization and low Pd loadings were the major targets of this study.For comparison purpose,catalytic activity was separately determined for both the methanol reforming and HDS of DBT reactions as well.Ni based catalysts were confirmed with better activity than Co ones for both the reactions with Pd promoted ones ranking at the top i.e.Pd-Ni-Mo/Al2O3 > Ni-Mo/Al2O3 > Pd-Co-Mo/Al2O3 > Co-Mo/Al2O3 where Pd-Ni-Mo/Al2O3 showed 91% DBT conversion at 380 ℃ and 12 h reaction time.Some of the selected organic additives on catalytic activity were tested for their effect toward HDS reaction which was unique with close relation to their chemical nature.Reaction products were quantitatively and qualitatively analyzed via HPLC and GC-MS techniques respectively which helped in elucidating reaction mechanism.     

Gas-Liquid Chromatographic Separation of Partially and Fully Methylated Methyl Glucopyranosides

Abstract

Carbowax 20M treated with 2-nitroterephthalic acid used as the liquid phase for gas-liquid chromatography gives sharply resolved peaks for several partially and fully methylated methyl glucopyranosides. The detector response of the standard compounds shows that the absence of a C₆ methoxyl group lowers the response of a flame ionization detector.     

Methylation of arsenic trioxide in hamsters with liver damage induced by long-term administration of carbon tetrachloride

One-time oral administration of arsenic trioxide to hamsters with toxic liver cirrhosis induced by longterm exposure to carbon tetrachloride resulted in significant elevations of the concentrations of dimethylarsenic species in the liver and in blood, and in high urinary excretions of dimethylarsenic species. These concentration changes in the liver, blood and urine indicated that the methylation of inorganic arsenic was not inhibited but promoted in hamsters suffering from experimentally induced toxic liver cirrhosis. Cirrhotic hamsters also had increased urinary excretion of inorganic arsenic. Results of the determinations of S-adenosylmethionine in the livers suggested that this compound may accelerate the methylation of inorganic arsenic in the cirrhotic liver.     

Effect of Acidic and Basic Species on the Hydrodesulfurization of Methyl-Substituted Dibenzothiophenes

Acidic components when added to Mo-based catalysts enhance the activity of the catalysts for the hydrodesulfurization (HDS) of methyl-substituted dibenzothiophenes (DBTs), the major refractory compounds included in gas oil. However, the enhancing effect of the acidic species is frequently retarded by impurities present in the gas oil, particularly by basic nitrogen compounds. Accordingly, evaluations of the performance of such acid-modified catalysts in HDS should take into account the combined effects of acidic and basic components. The performance is strongly dependent on the types of DBT compounds, acidic and basic species involved in the reaction, and promoters of the Mo-based catalysts.     

Identification and Differentiation of Isomeric Methylated Derivatives of Oxygenation Products of Polycyclic Aromatic Hydrocarbons by Gas Chromatography - Mass Spectrometry

Abstract

An isomeric pair of compounds is obtained from 4-car-boxyaldehydephenanthrene-5-carboxylic acid (1) by various methods routinely applied for the methylation of acidic oxygenation products of K-region polycyclic aromatic hydrocarbons (PAH's) prior to GC and GC/MS analysis. Differentiation of the individual cyclic and acyclic isomers, a classical general problem, proves possible by careful analysis of the mass spectral fragmentation patterns in the representative case studied here.     

离子液体耦合有机过氧化物脱除二苯并噻吩的研究

以12-磷钨酸为催化剂,研究了离子液体耦合有机过氧化物脱除二苯并噻吩(DBT)。研究结果表明,单独使用离子[bmim]BF4、[bmim]PF6液体为萃取剂,脱硫率为27.78%~38.76%。以由等体积的H2O2与甲酸制成有机过氧化物为氧化剂,不使用催化剂和离子液体,温度70℃,反应时间6 h,DBT氧化为二苯并噻吩砜的比例为76.6%。在催化剂作用下,将离子液体与氧化剂耦合使用时,脱硫率明显提高。当催化剂与DBT的摩尔比为0.20∶1,氧化剂与DBT的体积比为10∶1,[bmim]PF6离子液体与DBT的体积比为1∶1,在70℃反应6 h后,脱硫率可达98.60%。耦合体系重复使用五次后,氧化脱硫活性没有明显降低。     

Assessing the Brønsted Basicity of Diaminoboryl Anions: Reactivity toward Methylated Benzenes and Dihydrogen

Treatment of toluene or p‐xylene with diaminoboryllithium results in consecutive reactions, involving boryl‐anion‐mediated deprotonation at the benzylic position followed by nucleophilic substitution at the boron center, producing benzylborane species and LiH. Diaminoboryllithium also cleaves H₂ heterolytically affording diaminohydroborane and LiH, while the reaction of lithium diaminoboryl(bromo)cuprate with H₂ takes place accompanied by reduction of Cu^I to give diaminohydroborane, LiH, and Cu⁰.     

Contamination of outdoor settled dust by butyltins in Malta

The presence of compounds of tributyltin (TBT), dibutyltin (DBT) and monobutyltin (MBT) was determined in outdoor settled dust collected from several sites on the island of Malta, mainly from flat rooftops of school buildings. The dust was separated into three size fractions with diameters (µm) > 250, 125–250 and < 125, and the two finer fractions were analysed for butyltins using extraction with glacial acetic acid followed by derivatization/solvent extraction with sodium tetraethylborate in the presence of iso‐octane and quantitation by gas chromatography with flame photometric detection. The presence of TBT, DBT and MBT was established in most of the samples and TBT concentrations varied from non‐detectable (<5 ng Sn g^?1) to highs of 15.5 and 18.7 µg Sn g^?1 in Senglea and Marsaxlokk. TBT was generally found at concentrations significantly higher than reported hitherto in house dust collected from European homes. The geographical distribution of total organotins in both dust fractions suggests that TBT originates mainly from antifouling marine paint residues which contaminate the urban environment when ships' hulls are sand‐ or hydro‐blasted during maintenance and repair at the drydocks facility in Grand Harbour. Other significant sources of TBT are located at Marsaxlokk fishing port and Wied i?‐?urrieq creek, both hosting sizeable communities of fishermen and leisure boating. The data also suggest that the municipal solid waste landfill at Maghtab is an inland source of butyltins. We suggest that dust containing harmful butyltins could possibly be ingested to expose humans to a risk which is probably of concern especially for young children living close to the hotspots of contamination. Copyright © 2007 John Wiley & Sons, Ltd.     

Risperidone/Randomly Methylated β-Cyclodextrin Inclusion Complex—Compatibility Study with Pharmaceutical Excipients

Risperidone (RSP) is an atypical antipsychotic drug used in treating schizophrenia, behavioral, and psychological symptoms of dementia and irritability associated with autism. The drug substance is practically insoluble in water and exhibits high lipophilicity. It also presents incompatibilities with pharmaceutical excipients such as magnesium stearate, lactose, and cellulose microcrystalline. RSP encapsulation by randomly methylated β-cyclodextrin (RM-β-CD) was performed in order to enhance drug solubility and stability and improve its biopharmaceutical profile. The inclusion complex formation was evaluated using thermal methods, powder X-ray diffractometry (PXRD), universal-attenuated total reflectance Fourier transform infrared (UATR-FTIR), UV spectroscopy, and saturation solubility studies. The 1:1 stoichiometry ratio and the apparent stability constant of the inclusion complex were determined by means of the phase solubility method. The compatibility between the supramolecular adduct and pharmaceutical excipients starch, anhydrous lactose, magnesium stearate, and cellulose microcrystalline was studied employing thermoanalytical tools (TG-thermogravimetry/DTG-derivative thermogravimetry/HF-heat flow) and spectroscopic techniques (UATR-FTIR, PXRD). The compatibility study reveals that there are no interactions between the supramolecular adduct with starch, magnesium stearate, and cellulose microcrystalline, while incompatibility with anhydrous lactose is observed even under ambient conditions. The supramolecular adduct of RSP with RM-β-CD represents a valuable candidate for further research in developing new formulations with enhanced bioavailability and stability, and the results of this study allow a pertinent selection of three excipients that can be incorporated in solid dosage forms.     

负载型磷化镍催化剂的溶剂热法制备及其加氢脱硫性能

以廉价的三苯基膦(PPh₃)为磷源,以三正辛胺(TOA)为液相反应体系,溶剂热法制备了负载型Ni₂P/MCM-41催化剂,并采用XRD、BET、CO吸附、XPS和TEM等手段对制备得到的催化剂进行了表征。该方法的合成温度为330 ℃,反应在常压下进行,比程序升温还原法(H₂-TPR)所需的还原温度至少低300 ℃,比传统的溶剂热法合成原料更廉价。以二苯并噻吩(DBT)为模型化合物,比较了所制备的Ni₂P/MCM-41催化剂与H₂-TPR法制备的催化剂结构以及加氢脱硫(HDS)性能。结果表明,溶剂热法能够降低催化剂表面上P物种的集聚,从而得到较大比表面积的Ni₂P催化剂(690 m²/g);促进小尺寸、高度分散的Ni₂P活性相的生成;制得的催化剂的HDS活性明显高于H₂-TPR法催化剂,在反应温度340 ℃,质量空速2.0 h^-1,H₂/油=500(体积比),3.0 MPa的条件下,Ni₂P/M41-R催化剂DBT转化率达到96.8%,较H₂-TPR法高10.6%。