Conversion of Dimethyl Ether to a Mixture of Liquid Hydrocarbons with Increased Triptane Content

The influence of the structural type and of the textural and acid properties of the zeolite on the catalyst selectivity in synthesis of a mixture of liquid hydrocarbons with increased content of isoalkanes from dimethyl ether was examined. The synthesis of liquid hydrocarbons enriched in triptane in the course of gasoline production from CO and H₂ via dimethyl ether in the presence of La-H-Y zeolite was performed for the first time. Excess hydrogen in the system and relatively short contact time of the catalyst with the feed favor an increase in the triptane yield. Additional modification with palladium leads to optimization of the acid properties of the La-H-Y zeolite and, as a consequence, to an increase in the triptane content of the gasoline from 2.0 to 9.4 wt %.

     

Synthesis of liquid hydrocarbons enriched with triptane via dimethyl ether conversion over combined catalyst

A combined catalytic system composed of catalysts with different functions was prepared. The catalyst for the synthesis of lower olefins based on is H-ZSM-5 zeolite modified with Mg, was mixed with the catalyst for alkylation of isobutane by olefins based on H-Y zeolite modified with La and Pd. In the presence of the combined system, liquid branched hydrocarbons were synthesized from dimethyl ether in a hydrogen medium at 340 °C and a pressure of 10 MPa. The effect of the composition of the combined catalyst on its selectivity to liquid hydrocarbons and, specifically, triptane was shown.

     

Synthesis of gasoline from syngas via dimethyl ether

Zeolite H-TsVM has been loaded with palladium by different methods. The properties of the resulting catalysts in gasoline synthesis from syngas via dimethyl ether depend on the way in which palladium was introduced. The catalysts have been characterized by ammonia temperature-programmed desorption (TPD), temperature-programmed reaction with hydrogen, and X-ray photoelectron spectroscopy. According to ammonia TPD data, use of a palladium ammine complex instead of palladium chloride reduces the concentration of strong acid sites and raises the concentration of medium-strength acid sites, thereby reducing the yield of C1–C4 hydrocarbons and increasing the yield of gasoline hydrocarbons. At T = 340°C, P = 100 atm, and GHSV = 2000 h^?1, the dimethyl ether conversion is 98–99%, the gasoline selectivity is >60%, the isoparaffin content of the product is ～61%, and the arene content is not higher than 29%.     

The mechanism of phenol methylation on acid and basic zeolite catalysts

The alkylation of phenol with methanol on HY and CsY/CsOH catalysts was studied in situ under static conditions by ¹³C NMR spectroscopy. Attention was largely given to the identification of intermediate compounds and mechanisms of anisole, cresol, and xylenol formation. The mechanisms of phenol methylation were found to be different on acid and basic catalysts. The primary process on acid catalysts was the dehydration of methanol to dimethyl ether and methoxy groups. This resulted in the formation of anisole and dimethyl ether, the ratio between which depended on the reagent ratio, which was evidence of similar mechanisms of their formation. Subsequent reactions with phenol gave cresols and anisoles. Cresols formed at higher temperatures both in the direct alkylation of phenol and in the rearrangement of anisole. The main alkylation product on basic catalysts was anisole formed in the interaction of phenolate anions with methanol; no cresol formation was observed. The deactivation of acid catalysts was caused by the formation of condensed aromatic hydrocarbons that blocked zeolite pores. The deactivation of basic catalysts resulted from the condensation of phenol and formaldehyde with the formation of phenol-formaldehyde resins.     

Computational Study on Thermodynamic Properties of Fischer-Tropsch Synthesis Process

Using the highly accurate G4 method, we computed the thermodynamic data of 1287 possible reaction products under a wide range of reaction conditions in the Fischer-Tropcsh synthesis (FTS) process. These accurate thermodynamic data provide basic thermodynamic quantities for the actual chemical engineering process and are useful in analyzing product distribution because FTS demonstrates many features of an equilibrium-controlled system. Our results show that the number of thermodynamically allowed products to increase when lowering temperature, raising pressure, and raising H₂/CO ratio. At low temperature, high pressure and high H₂/CO ratio, many products are thermodynamically allowed and the selectivity of product has to be controlled by kinetic factors. On the other hand, high selectivity of lighter products can be realized in thermodynamics by raising temperature and lowering pressure. We found that the equilibrium product yield will reach a maximum and remain unchanged when lowering temperature, raising pressure, and raising H₂/CO ratio to some limits, implying that optimizing reaction conditions has no effect on equilibrium product yields beyond these limits. The thermodynamic analysis is also useful in designing and evaluating FTS reaction mechanisms. We found that reaction pathways through formaldehyde should be discarded because of its extremely low equilibrium yield. Recently, in the FTS process using metal-oxide-zeolite catalysts for the highly selective production of C₂-C₄ olefins and aromatic hydrocarbons, there are several guesses on the possible reaction intermediates entering the zeolite channel. Our results show that ketene, methanol, and dimethyl ether are three possible reaction intermediates.     

GC of Catalytic Reactions Products Involved in the Promising Fuel Synthesis

Catalytic reactions involved in the synthesis of the promising kinds of novel fuel and products formed in these reactions were systematized according to the resulting fuel type. Generalization of the retention of the substances comprising these products is presented. Chromatograms exhibiting their separation on chromatographic materials with the surface of different chemical properties are summarized. We propose procedures for gas-chromatographic analysis of the catalytic reactions products formed in the synthesis of hydrogen, methanol, dimethyl ether and hydrocarbons as a new generation of fuel alternative to petroleum and coal. For partial oxidation of methane into synthesis gas, on-line determination of the components obtained in the reaction was carried out by gas chromatography and gas analyzer based on different physicochemical methods (IR spectroscopy and electrochemical methods). Similarity of the results obtained using these methods is demonstrated.

     

Physicochemical and catalytic characteristics of La-H-ZSM-5 zeolite in converting dimethyl ether to the mixtures of gasoline hydrocarbons: Effect of ion exchange conditions

The effect of the manner and conditions of introducing lanthanum cations into NH₄-ZSM-5 zeolite on the properties of catalysts for the conversion of dimethyl ether into the mixtures of gasoline hydrocarbons is studied. The physicochemical properties of synthesized catalysts are studied by means of temperature-programmed ammonia desorption, the adsorption of benzene, atomic absorption spectroscopy, differential scanning calorimetry, and thermogravimetry. It is shown that the degree to which lanthanum cations are replaced by ammonium cations both depends on the conditions of ion exchange in the zeolite and affects its acidity spectrum and the selectivity of the formation of paraffin hydrocarbons with isostructure. It is concluded that an increase in the amount of introduced lanthanum leads to an increase in the content of iso-paraffins from 69 to 76 wt % and a decrease in the content of aromatic hydrocarbons from 10.5 to 5.5 wt % and that of durene from 1.5 to 0.2 wt % in the products.     

One pot synthesis of <Emphasis Type="Italic">N</Emphasis>-ethylaniline from nitrobenzene and ethanol

A novel method for the one pot synthesis of N-alkyl arylamines from nitro aromatic compounds and alcohols is proposed through the combination of the aqueous-phase reforming of alcohol for hydrogen production, the reduction of nitro aromatic compounds for the synthesis of aromatic amine and the N-alkylation of aromatic amine for the production of N-alkyl arylamine over an identical catalyst under the same conditions of temperature and pressure in a single reactor. In this process, hydrogen generated from the aqueous-phase reforming of alcohols was used in-situ for the hydrogenation of nitro aromatic compounds for aromatic amine synthesis, followed by N-alkylation of aromatic amine with alcohols to form the corresponding N-alkyl arylamines at a low partial pressure of hydrogen. For the system composed of nitrobenzene and ethanol, under the conditions of 413 K and P _N2 = 1 MPa, the conversion degrees of nitrobenzene and aniline were 100%, the selectivity to N-ethylaniline and N, N-diethylaniline were 85.9% and 0%–4%, respectivity, after reaction for 8 h at the volumetric ratio of nitrobenzene:ethanol:water = 10:60:0. The selectivity for N, N-diethylaniline production is much lower than that through the traditional method. In this process, hydrogen and aromatic amines generated from the aqueous-phase reforming of alcohols and hydrogenation of nitro aromatic compounds, respectively, could be promptly removed from the surface of the catalyst due to the occurrence of in-situ hydrogenation and N-alkylation reactions. Thus, this may be a potential approach to increase the selectivity to N-alkyl arylamine. Supported by the Program for New Century Excellent Talents in University (Grant No. NCET-04-0557), and the Specialized Research Fund for the Doctoral Program of High Education (Grant No. SRFDP-20060337001)     

The Photochemistry of Diazomethane the Reactions of Methylene with Methanol and Ethanol

In the photolysis of diazomethane-methanol. mixture, the reaction of methylene with methanol gives dimethyl ether and ethanol as products. The ratio of dimethyl ether to ethanol is found to be independent to pressure and to. the composition of diazomethane-methanol mixture. Methylene insertion into O—H bond is about 11 times faster than that into C—H bonds of methanol. The ratio decreases with increase of temperature. In the diazomethane-ethanol system, ethylmethyl ether, propanol-1 and propanol-2 are found as the products of insertion reaction of methylene into ethanol. The ratios of ethylmethyl ether to propanol-1 and to propanol-2 are both found to be almost constant and independent to pressure and to the composition of diazomethane-ethanol mixture. A small temperature effect on the ratios are observed. The rate of insertion of methylene into O—H bond is about 7.3 and 14.2 times faster than those into primary and secondary C—H bonds of ethanol, respectively.     

Study of the Synthesis of Dextran Derivatives

Abstract

The synthesis of biologically active high-molecular compounds offers an interesting subject for study in polymer chemistry. Dextran, one of the best blood plasma expanders, is a good product for use in synthesizing biologically active water-soluble polymers. This paper discusses the synthesis of water-soluble derivatives of dextran which can be used as drug carriers or as independent physiologically active compounds. The synthesis of these derivatives involved oxidation of dextran, O-alkylation of dextran, subsequent transformation of ethers of dextran containing reactive functional groups, and graft polymerization. Periodate oxidation of dextran resulted in the production of a derivative of dextran containing aldehyde groups: dialdehydedextran. Subsequent oxidation of dialdehyde-dextran with sodium chlorite permitted the introduction of carboxyl groups into the macromolecule of dextran. In order to introduce sulfonic acid, phosphonic, mercapto, chlorhydrinic, cyano, and aromatic amino groups into the macromolecule of dextran, dextran was alkylated with various alkylating reagents. The synthesized products were sulfopropyl, phosphonomethyl, mercaptoethyl, 3-chloro-2-hydroxypropyl, cyanoethyl, and 2-(3′-amino-4′-methoxyphenyl)-sulfonylethyl ethers of dextran. Treatment of the 3-chloro-2-hydroxypropyl ether of dextran with ammonia, amines, and aliphatic and aromatic amino acids produced ethers of dextran containing primary, secondary, and tertiary amino groups and quaternary ammonium groups, as well as residual aliphatic and aromatic amino acids.

Cyanethyl ether of dextran was used to synthesize derivatives of dextran containing thioamide and hydrazidine groups.

Graft copolymers of dextran and polyacrylic acid and of dextran and poly-2-methyl-5-vinylpyridine were synthesized. Redox systems were utilized to initiate graft copolymerizatLon with tetravalent cerium compounds used as oxidants and pentavalent vanadium with dextran or 2-(3′-amino-4′-methoxyphenyl)-sulfonylethyl ether of dextran used as reductant. This method produced graft copolymers with short graft chains.

The availability of the above derivatives of dextran has permitted the linking of drugs to dextran by different types of chemical bonds.     

One pot synthesis of N-ethylaniline from nitrobenzene and ethanol

A novel method for the one pot synthesis of N-alkyl arylamines from nitro aromatic compounds and alcohols is proposed through the combination of the aqueous-phase reforming of alcohol for hydrogen production, the reduction of nitro aromatic compounds for the synthesis of aromatic amine and the N-alkylation of aromatic amine for the production of N-alkyl arylamine over an identical catalyst under the same conditions of temperature and pressure in a single reactor. In this process, hydrogen generated from the aqueous-phase reforming of alcohols was used in-situ for the hydrogenation of nitro aromatic compounds for aromatic amine synthesis, followed by N-alkylation of aromatic amine with alcohols to form the corresponding N-alkyl arylamines at a low partial pressure of hydrogen. For the system composed of nitrobenzene and ethanol, under the conditions of 413 K and PN2 = 1 MPa, the conversion degrees of nitrobenzene and aniline were 100%, the selectivity to N-ethylaniline and N, N-diethylaniline were 85.9% and 0%-4%, respectivity, after reaction for 8 h at the volumetric ratio of nitrobenzene:ethanol:water = 10:60:0. The selectivity for N, N-diethylaniline production is much lower than that through the traditional method. In this process, hydrogen and aromatic amines generated from the aqueous-phase reforming of alcohols and hydrogenation of nitro aromatic compounds, respectively, could be promptly removed from the surface of the catalyst due to the occurrence of in-situ hydrogenation and N-alkylation reactions. Thus, this may be a potential approach to increase the selectivity to N-alkyl arylamine.     

Ab initio study of substituent effects in the interactions of dimethyl ether with aromatic rings

Ab initio calculations have been used to investigate the interaction energies of dimers of dimethyl ether with benzene, hexafluorobenzene, and several monosubstituted benzenes. The potential energy curves were explored at the MP2/aug-cc-pVDZ level for two basic configurations of the dimers, one in which the oxygen atom of the dimethyl ether was pointed towards the aromatic ring and the other in which the oxygen atom was pointed away from the aromatic ring. Once the optimum intermolecular distances between the dimethyl and the aromatic ring had been determined for each of the dimers in both configurations at the MP2/aug-cc-pVDZ level, single point energy calculations were performed at the MP2/aug-cc-pVTZ level. A CCSD(T) correction term to the energy was determined and this was combined with the MP2/aug-cc-pVTZ energies to estimate the CCSD(T)/aug-cc-pVTZ interaction energies of the dimers. The estimated CCSD(T)/aug-cc-pVTZ interaction energies are predicted to be attractive for all of the dimers in both configurations and dispersion interactions are found to be a large component of the stabilization of the dimers. For the dimers with the dimethyl ether oxygen pointing towards the aromatic ring, the strengths of interaction energies are found to increase as the aromatic ring becomes more electron deficient, while for the dimers with the dimethyl ether oxygen pointing away from the aromatic ring, they increase as the aromatic ring becomes more electron rich. In both cases, the trends can be explained in terms of the electrostatic potentials of the dimethyl ether and the aromatic rings.     

便携式气相色谱-质谱联用仪现场测定畜禽粪便堆肥中挥发性有机物

采用便携式气相色谱-质谱联用仪进行了畜禽粪便堆肥排放气体中挥发性有机物质的现场分析.结果表明,在堆肥排放气体中可检测到含硫物质、脂肪烃、芳香烃及含氯有机物共20种物质.在已定量的8种物质中,CS2浓度最高,达到204 mg/m3;CS2和二甲二硫超过《恶臭污染物排放标准》(GB1455-93)的限值;SO2和苯超过《室内空气质量标准》(GB/T 18883-2002)的限值.本方法避免了常规检测中易出现的组分分解等问题,SO2测定值较常规方法提高59.3％.本方法操作方便,结果准确,适于对挥发性有机化合物的在线监测.     

Synthesis of dimethyl carbonate from methanol and supercritical carbon dioxide

The synthesis of dimethyl carbonate (DMC) from methanol and supercritical carbon dioxide over various base catalysts has been studied. Compounds of group-I elements (Li, Na and K) were used as base catalysts. The promoter and the dehydrating agent were also used to enhance the yield of DMC. The effects of the catalysts, promoter and dehydrating agent on the yield of DMC were investigated. By-products such as dimethyl ether (DME) and C₁–C₂ hydrocarbons were formed with the DMC as a main product. The yield of DMC with different alkali metal catalysts ranked in the following order: K > Na > Li. The catalysts of the metal-CO₃ compounds were more effective than the metal-OH compounds in DMC synthesis. The maximum DMC yield reached up to about 12 mol% in the presence of K₂CO₃ (catalyst), CH₃I (promoter) and 2,2-dimethoxypropane (dehydrating agent) at 130–140°C and 200 bar. The reaction mechanism of DMC synthesis from methanol and supercritical carbon dioxide was proposed.     

Determination of Trace Amounts of Organic Pollutants in the Yellow River by Capillary Column Gas Chromatography-Mass Spectrometry

Abstract

The trace organic pollutants in the Yellow River enriched by a solvent extraction method were pre-separated into four different fractions of fatty hydrocarbons, polycyclic aromatic hydrocarbons, polar compounds and organic acids and were analyzed by the use of combined capillary column gas chromatography-mass spectrometry. Using the combined techniques of relative retention value, mass spectra and mass chromatogram, more than 60 organic pollutants were identified, among which 16 fatty hydrocarbons and 6 polycyclic aromatic hydrocarbons which were quantitatively analyzed. The concentration range of fatty hydrocarbon was 5–800 ng/l, and that of polycyclic aromatic hydrocarbon was 0-90ng/l.     

About Intermolecular Interaction,Submolecular Structure,and Paramagnetism of Polyconjugated Systems

It is shown that macromolecules with polyconjugated systems are capable of forming strong 7r-complex associates. The paramagnetic centers cause intercombinative transitions in auto- or α-complexes with other molecules and increase their reactivity (“effect of local activation”).

At the present time it has been determined that an increase of polyconjugated chains leads to a decrease of the energy slits and the energy of excited states.

At the same time ionization potentials (I) are decreased, but electron affinity (A) and electron polarizability are increased. One can show that the change of the difference I - A correlates with the change in the physicochemical properties of polyconjugated homologs [1,2]. Some data concerning aromatic hydrocarbons, wherein the polarization and space influence of groups and heteroatoms are excluded, may be illustrative.

As we can see from Figs. 1 and 2, in the cases of polyacene and poly-p-phenylene the melting points and the heat of sublimations increase with a decrease in I - A. At the same time the solubility and activation energy of conductivity of these compounds decrease.     

Insights into the Reaction Mechanism of Ethanol Conversion into Hydrocarbons on H‐ZSM‐5

Ethanol dehydration to ethene is mechanistically decoupled from the production of higher hydrocarbons due to complete surface coverage by adsorbed ethanol and diethyl ether (DEE). The production of C₃₊ hydrocarbons was found to be unaffected by water present in the reaction mixture. Three routes for the production of C₃₊ hydrocarbons are identified: the dimerization of ethene to butene and two routes involving two different types of surface species categorized as aliphatic and aromatic. Evidence for the different types of species involved in the production of higher hydrocarbons is obtained via isotopic labeling, continuous flow and transient experiments complemented by UV/Vis characterization of the catalyst and ab initio microkinetic modeling.     

A liquid chromatography tandem mass spectrometry method for simultaneous analysis of 46 atmospheric particulate-phase persistent organic pollutants and comparison with gas chromatography/mass spectrometry

A novel multi-analyte method for the simultaneous determination of 46 compounds of environmental concern, most of them belonging to the category of persistent organic pollutants, was developed using high-performance liquid chromatography and the results were compared to those obtained by gas chromatography. This study was performed in perspective of a cumulative exposure assessment of substances of health concern in environments where high levels, relatively to airborne particulate matter, can be found. The target compounds included polychlorinated biphenyls, brominated flame–retardants and derivatives of polycyclic aromatic hydrocarbons.

The multi-analyte method was evaluated in air particulate matter in terms of reproducibility, linearity, recovery, limits of detection and quantification and matrix effect. The recovery was above 70% for all the analytes, whereas limits of quantification ranged between 23 and 390 pg?m^?3 in liquid chromatography and less than ten times in gas chromatography–mass spectrometry.

Matrix effect was generally negligible for both the techniques, except the case of the detection of oxygenated derivatives of polycyclic aromatic hydrocarbons by gas chromatography.

In order to demonstrate the efficacy and to assess the method performances (accuracy and precision), both the techniques were applied to standard reference materials, and the results were compared, discussing their advantages and disadvantages.

The method was finally applied to a real sample of indoor airborne particulate matter with aerodynamic diameter ≤4 μm (PM₄).

We demonstrated that liquid chromatography was the only technique able to analyse the 46 compounds, including thermally degradable ones, with a single chromatographic run without derivatisation steps. On the other hand, gas chromatography still presents higher sensitivity for the detection of some of the investigated compounds. This study can be considered only explorative and further improvements can be expected with new-generation LC-MS instruments (10–100 times more sensitive).     

Monocyclic Aromatic Hydrocarbons in Bile of Flounder Exposed to a Petroleum Oil

Abstract

The bioaccumulation of contaminants in tissues of fish exposed to petroleum hydrocarbons is of concern because of the toxicity associated with polycyclic aromatic compounds (PAC). Exposure of Winter flounder (Pseudopleuronectes americanus) to several concentrations of Hibernia crude oil in sediments, for four months during the winter, resulted in a dose-response in the accumulation of hydrocarbons in muscle tissue and the elimination of metabolites (glucuronides and sulphates) through the gall bladder bile. Results of a multispectroscopic analysis using ultraviolet/fluorescence (uv/f) and gas chromatography-mass spectromemry (GC-MS) are presented. In muscle tissue, the monocyclic aromatic hydrocarbons were previously shown to predominate over alkylated PAC, while parental PAC were least detectable. Naphthalene and phenanthrene derivatives were more easily characterised as bile metabolites (GC-MS) than benzenoid derivames which, according to uv/f analysis also represent a large fraction of the metabolites. The higher sensitivity of bile metabolites in determining exposure compared to free hydrocarbons in muscle tissue was confirmed in terms of the concentration of hydrocarbons in sediments.