球形红细菌降解2,4-二硝基甲苯的途径及酶学性质

采用气相色谱-质谱联用仪(GC-MS)分析了球形红细菌降解2,4-二硝基甲苯(2,4-DNT)的中间代谢产物,分析了可能的降解途径,讨论了培养基中2,4-DNT的初始质量浓度、溶液pH值及反应温度对3种酶的酶比活力影响。结果表明,当2,4-DNT的初始质量浓度为40 mg/L时,培养72h后,可以检测到5种物质:2,4-二硝基甲苯、4-氨基-2硝基甲苯、2-氨基-4硝基甲苯、4-硝基-1,2-二(三甲基硅烷)苯、1,2,4-三(三甲基硅烷)苯,其可能的降解途径为2,4-DNT首先还原为4-氨基-2-硝基甲苯和2-氨基4-硝基甲苯,再进一步转化为4-硝基-1,2-羟基苯,然后氧化为1,2,4-三羟基苯,之后开环生成β-酮己二酸,最终降解为小分子物质。硝基还原酶、邻苯二酚2,3-双加氧酶和邻苯二酚1,2-双加氧酶的酶比活力最适宜温度分别为35、30、35℃,最适宜pH值分别为7.0、8.0、7.0,最适宜培养基初始2,4-DNT质量浓度均为40mg/L。     

Solubilization of Nitroaromatic Compounds from Multi-Component Mixtures into Nonionic Surfactant Micellar Solutions

This study investigated the solubilization of 2-component and 3-component mixtures of 4-nitrotoluene (4-NT), 2,6-dinitrotoluene (2,6-DNT), and 2,4,6-trinitrotoluene (TNT) in solutions of Brij-35, Brij-58, and alkyl phenol ethoxylates (Tergitol NP-10 to NP-40). 4-NT had the highest molar solubilization ratio (MSR) and TNT the lowest. For all 2-component systems with 4-NT, the MSR of 2,6-DNT and TNT increased. When either 2,6-DNT or TNT was present, the MSR values increased slightly for Tergitol NP-10 (NP10) and Tergitol NP-13 (NP13). For 3-component systems, TNT's MSR increased for all the surfactants, while significant increases in the MSR of 4-NT and 2,6-DNT were found for NP10 and NP13.     

Sealing and reopening of micropores of mordenite and ZSM-5 by disilylbenzene compounds

Regularly-structured solid matrices are potent materials for regulating molecular permeation and diffusion. Zeolite materials bearing ordered micropores are very advantageous to control the diffusion of molecules. When some disilylbenzene compounds were grafted on mordenite and ZSM-5 zeolites, the penetrations of small molecules such as α-methylstyrene (AMS) and molecular nitrogen were prevented by the direct formation of the crosslinking with two grafting sites on the exterior surfaces of those zeolites. The dimerization reaction of α-methylstyrene effectively promoted by mordenite was not catalyzed by these grafted mordenite samples. No adsorptions of molecular nitrogen were observed in the grafted mordenite and ZSM-5 samples. When these grafted samples were calcined, both the catalytic activity for the dimerization and the permeation of molecular nitrogen were recovered. The reopening of the micropores of zeolites was also achieved by the treatment with HCl acidic solutions. Thus, the diffusion and the permeation of various small molecules can be perfectly and reversely controlled by the sealing and the reopening of the micropores of zeolites by the disilylbenzene compounds.     

Isomerization of α-Pinene Oxide Over Iron-Modified Zeolites

Fe-modified mordenite, ferrierite, Y, ZSM-5, ZSM-12 and beta zeolite catalysts were prepared by solid state ion-exchange and conventional liquid phase ion-exchange methods from aqueous solutions. Sn- modified H-beta-300 zeolite catalyst was prepared by the later method. The characterization of proton form, Fe and Sn modified zeolites was carried out using X-ray powder diffraction, scanning electron microscopy, Mössbauer spectroscopy with magnetic measurements, transmission electron microscopy, nitrogen adsorption, X-ray absorption spectroscopy, X-ray photoelectron spectroscopy, inductively coupled plasma spectroscopy, thermo-gravimetric analysis and FTIR spectroscopy using pyridine as a probe molecule. Isomerization of α-pinene oxide over the Fe and Sn modified zeolite catalysts was carried out in the liquid phase using a batch-wise glass reactor. Formation of campholenic aldehyde and fencholenic aldehyde were observed to be influenced by the structure, acidity of zeolite and contents of Fe and Sn, reaction temperature and the catalysts pretreatment.     

一硝基甲苯生产中残液的回收技术

采用水蒸汽蒸馏回收除焦残液中的一硝基甲苯,用脱色、结晶提纯２,４ 二硝基甲苯的方法,取得了一硝基甲苯总回收率大于９５％、提纯后２,４ 二硝基甲苯纯度在９９５％以上的效果。     

Disproportionation and Methylation of Toluene with Methanol Over Zeolite Catalysts

Zeolites TNU-9, SSZ-33, mordenite (MOR) and ZSM-5 were evaluated for their activities in toluene disproportionation and methylation reaction of toluene with methanol. The medium-pore zeolite TNU-9 was found to possess the highest conversion in toluene disproportionation as compared with SSZ-33, mordenite and ZSM-5 based catalyst. Zeolite mordenite with the highest Si/Al ratio of 135.9 (the lowest concentration of active sites) exhibited the highest toluene conversion and maximum xylene yield in toluene methylation. On mordenite, the presence of channel intersections allows more reaction space for the formation of bulky intermediates and/or products and the 12-ring channels on the other hand, allow diffusion without trapping, since the channel diameter is large enough. In toluene methylation, xylene selectivity at the same conversion level follows the order: ZSM-5 > TNU-9 > MOR > SSZ-33, which implies that xylene selectivity is directly related to the size of channels from medium to large pore zeolites. The medium-pore zeolite ZSM-5, with 10-ring channels, shows the lowest reactivity for further alkylation of xylene, while mordenite with 12-ring channel shows the highest reactivity for further alkylation of xylene.     

Determination of relative acid strength and acid amount of solid acids by Ar adsorption

Relative acid strength and acid amount of solid acids (alumina, silica-alumina, sulfated zirconia, mordenite, ZSM-5, beta, Y, and reduced MoO₃) are determined by argon adsorption technique. To obtain the heat of Ar adsorption and saturated adsorption amount, the adsorption isotherm is analyzed using the theory reported by Cremer and Flügge. The obtained heats of Ar adsorption and saturated adsorption amounts of sulfated zirconia catalysts and proton-type zeolites correspond well with the activities of acid-catalyzed pentane isomerization of these catalysts. The heats of adsorption were −22 kJ mol⁻¹ for sulfated zirconia, and ca. −19 kJ mol⁻¹ for mordenite, ZSM-5, and beta. Molybdenum oxides reduced at 623 and 773 K show large heat of adsorption (−19.3 and −19.7 kJ mol⁻¹, respectively), and these are classified into the superacid.     

复合催化剂光催化降解DNT废水及其降解机理

为探索负载型多金属氧酸盐类复合催化剂光催化降解炸药废水的催化活性及降解机理,采用溶胶-凝胶-溶剂热的路径,制备了3种负载型多金属氧酸盐类复合催化剂H_3PW_(12)O_(40)/TiO_2、H_3PW_(12)O_(40)/TiO_2(P123)和SO_4~(2-)-H_3PW_(12)O_(40)/TiO_2(P123)。以炸药废水中典型有机污染物二硝基甲苯(DNT)为目标化合物,考察了所制备的复合催化剂在光催化降解DNT废水方面的催化活性,并对不同催化剂之间光催化活性的差异进行了合理的解释,分析了催化剂的结构与其光催化性能之间的关系。采用气相色谱-质谱联用仪(GC-MS)对废水中反应物和产物的种类进行了鉴定和分析,对光催化氧化法降解DNT废水的降解机理和矿化程度进行了研究。结果表明,以SO_4~(2-)-H_3PW_(12)O_(40)/TiO_2(P123)为催化剂,光照4h后,DNT废水降解率达98.73%。光催化降解DNT废水过程中,发生了甲基氧化、脱硝基、脱羧基等反应,降解过程中的中间产物主要包括对硝基苯甲酸、间硝基苯甲酸、1,3-二硝基苯、2,4-二叔丁基苯酚、2,4-二硝基苯甲醛。光催化降解4h后,除极少量3,4-DNT外,其余硝基苯类化合物均完全降解。     

Seifenspaltung – kontinuierlich und umweltfreundlich

Soap Splitting – Continuous and Ecologically Harmless In the classical refining of vegetable oils the free fatty acids are saponified and separated from oil by centrifuging. The centrifuged soap solution also contains neutral oil and non hydrationable sliming substances. The resulting emulsion impedes splitting and the separation of the aqueous phase from the oily fatty acid phase. Therefore you often work with high surplus of sulphuric acid and direct vapour for heating and stirring. The direct vapour carries away fatty acid and sulphuric acid as aerosol and must be washed before drawing out into the enviroment. If the mixture from the centrifuges undergoes a saponification reaction, splitting can be continuously carried out by addition of sulphuric acid, regulated by the pH-value, without direct vapour. Thus an important requirement for an ecologically harmless procedure of soap splitting is given.     

Simulation of continuous packed bed reactive distillation column for the esterification process using activity based kinetic model

A mathematical model for the continuous packed bed reactive distillation process of esterification of acetic acid with methanol is developed. The kinetic rate equation, which plays a major role for the performance of reactive distillation and it is the part of model, is required for the liquid phase reversible esterification reaction. The mineral sulphuric acid is used as the catalyst. The kinetic experiments are carried out under different temperatures in the range of 305.15 to 333.15 K and catalyst concentrations in the range of 0.1267 mole H⁺/lit to 0.6537 mole H⁺/lit. From that experimental data the kinetic model is developed and the same is used for the simulation of reactive distillation process. Equilibrium stage model, in which the vapour and the liquid leaving a stage are assumed to be in equilibrium with each other, has been used for the simulation of reactive distillation process by incorporating our kinetic model. Conversion of acetic acid as function of reflux ratio and reboiler ratio has been predicted. The liquid composition and temperature profiles versus stage number have been also predicted. Finally, the optimum operating conditions obtained from the simulation results for high pure methyl acetate by reactive distillation process.     

Polyoxyethylene esters of fatty acids: an alternative synthetic route for high selectivity of monoesters

Esterification reaction of fatty acids with polyoxyethylenes has been studied in the presence of solid acid catalysts and the results are compared with those obtained with a classical homogeneous catalyst, p-toluene sulphonic acid. Solid acid catalysts showed very high selectivities for monoesters even under less favorable reaction conditions of 1:1 molar ratios of oleic acid to PEG. Excess amount of PEG is normally required to ensure high selectivity for monoesters in the presence of homogeneous catalysts. The yields for monoesters given by heterogeneous catalysts such as zeolites, HPA and nafion were comparable to that with p-toluene sulphonic acid after 24 h of reaction. Results suggest that solid acid catalysts are potential catalysts for selective synthesis of monoesters from oleic acids and PEG even under severe reaction conditions. A screening study of different solid acid catalysts showed ZSM-5, zeolite-β, and nafion to be better catalysts than zeolite USY and mordenite, the former giving higher selectivity and yield to monoesters. The results suggest that the most important parameters in optimization catalyst performance for monoesters production is the acid strength and less so on other properties such as shape selectivity and concentration of active sites.     

气相色谱法测定地下水中2,4-/2,6-二硝基甲苯

新建一种测定地下水中2,4-和2.6-二硝基甲苯的液液萃取-气相色谱法。甲苯作溶剂萃取水中的2,4-和2.6-二硝基甲苯,经DB-1701色谱柱分离,电子捕获检测器(ECD)检测。经过优化的色谱方法测定结果显示,2,4-和2.6-二硝基甲苯的检出限都为0.05μg/L,均具有较好的线性关系,相关系数都大于0.999;2,4-和2.6-二硝基甲苯的精密度分别为3.4%～12.6%和4.0%～15.5%;2.4-和2,6-二硝基甲苯的加标回收率分别是75.4%～126.0%和71.5%～122.6%。本方法准确、灵敏、快速,可为地下水样中2,4/2,6-二硝基苯的污染评价提供技术支持。     

Kinetics of dealkylation–transalkylation of C9 alkyl-aromatics over zeolites of different structures

Dealkylation of methylethylbenzenes as well as the conversion of mixtures trimethylbenzenes (TMBs) and methylethylbenzenes (MEBs) over medium- and large-pore zeolites with different topologies and acid-site concentrations were investigated in a fluidized-bed reactor. MEB conversion, its dealkylation selectivity and transalkylation selectivity were profoundly influenced by the topology of the zeolites. Zeolite beta shows a highest MEB conversion (70–80%) while ZSM-5 exhibited very high dealkylation selectivity. The results of kinetic study indicate that MEB conversion is influenced by zeolite type and by SiO₂/Al₂O₃ ratio. The extent of TMB and MEB conversions over different zeolites as well as xylene yields indicate that while ZSM-5 could substantially convert MEBs (mainly by dealkylation), it could not effectively catalyze TMB conversion. On the other hand, the conversions of MEBs as well as TMBs were quite high over mordenite and zeolite beta, resulting in much higher xylene yields. These results indicate that while the dealkylation of MEBs is a necessary condition, it is not a sufficient condition to obtain higher xylene yield. Kinetic modeling results show that the transalkylation reaction was significantly faster than the disproportionation reaction indicating that the transfer of methyl group from TMB to toluene is a preferred route under the reaction conditions studied.     

2,3-丁二醇液相脱水制备甲乙酮反应研究

研究了2,3-丁二醇液相脱水生成甲乙酮(MEK)的反应,对浓硫酸、对甲苯磺酸、ZSM-5分子筛以及自制固体酸的催化活性进行比较,发现对甲苯磺酸对2,3-丁二醇脱水制备甲乙酮的催化性能较好。以对甲苯磺酸做催化剂,优化实验装置,通过对实验结果进行分析得到最佳的反应条件为:采用反应精馏装置,催化剂用量为2,3-丁二醇质量的3%,塔顶温度控制在70～80℃,反应时间为5.5h,产品收率可达到78.9%。此外,还考察了脱水副反应生成的高沸点缩合物的水解反应,硫酸用量为缩合物质量的1%,反应时间为100min,MEK收率为93.3%。     

液相催化氧化法制备对硝基苯甲酸

以硫酸锰作催化剂液相条件下用氧气氧化对硝基甲苯,生成对硝摹苯甲酸,收率75％。反应以吗啉作溶剂。在碱性条件常压下进行。探讨了反应条件对氧化过程的影响,分析了可能的反应机理。     

Recovery of Organic Values from TNT Purification Waste Water

Pure sodium 2,4-dinitrotoluene-3-sulfonate and -5-sulfonate were prepared, and a procedure was developed for their extraction (as a mixture) from TNT purification waste water (‘red water’). Reactions of the sulfonates were studied, with special emphasis on possible direct and indirect methods for desulfonating them to 2,4-DNT. Other reactions studied included reduction of one or both nitro groups, followed by desulfonation, yielding 2-amino-4-nitrotoluene and 2,4-diamino-toluene, respectively, and replacement of the sulfonate group by chlorine, hydroxyl, and various substituted amino groups. Most of these reactions with the pure sulfonates were also applied to the corresponding TNT isomers, and in some cases directly to stabilized red water.     

A study on toluene disproportionation over mordenite

The disproportionation of toluene over a commercial mordenite catalyst was studied in a fixed bed reactor, in the vapour phase and in the presence of hydrogen. The toluene conversion increased steadily as the temperature was raised but decreased with increase in space velocity. The addition of up to 14.5 mol% m-xylene to the feed led to an increase in the yield of the p- and o-isomers and the isomerization of xylenes proceeded to the thermodynamic equilibrium. The catalyst was impregnated with 8.5 wt% of phosphorus, which suppressed most of the catalytic activity. This was attributed to the reduction in the number of Brönsted and Lewis acid sites, revealed by infrared spectroscopy.     

Catalyst activity decay functions in liquid and vapour phase xylenes isomerization over H-Y zeolite

A kinetic comparison of the deactivation of a zeolite catalyst in vapour and liquid phase isomerization of xylenes has been made. Quantitative data confirm the more rapid deactivation in the vapour phase. The liquid phase deactivation was best expressed by an exponential function, while the vapour phase was best expressed by a power law. Both systems correlated best using time on stream as the variable. Changes in isomerization selectivity were shown to result from differing variation of deactivation parameters with temperature. The faster deactivation of mordenite compared with Y zeolite was confirmed, and is consistent with the structural characteristics of the two zeolites.     

Application of zeolite T membrane to vapor-permeation-aided esterification of lactic acid with ethanol

Zeolite T membranes were applied to vapor-permeation-aided esterification of lactic acid with ethanol. The hybrid process provided almost complete conversion within a short reaction time by removing water from the reaction mixture. Zeolite T membrane worked steadily for a long time. The reaction time-courses were described by a model based on the assumptions that the esterification obeyed second-order kinetics and the permeation flux of each component was proportional to its concentration in the reaction mixture. The final reaction liquid mixtures consisted mostly of ethyl lactate and ethanol with little ester of polylactic acids, although concentrated lactic acid solution was used as a source.     

Electrosynthesis of toluidines using thermally coated Ti/TiO2 electrodes

Cyclic voltammetric and preparative scale investigations on the electroreduction of (o-nitrotoluene (ONT), m-nitrotoluene (MNT), p-nitrotoluene (PNT) and 2,4-dinitrotoluene (DNT) to their corresponding toluidines in 1 m H₂SO₄ using thermally coated Ti/TiO₂ electrode are reported. In the cyclic voltammetric time scales inhibitive adsorption which decreased in the order i _p ONT > i _p MNT > i _p PNT > i _p DNT was noticed. The heterogeneous redox catalytic currents were also found to decrease in the same order. In preparative electrolysis, these inhibitive effects became unimportant. Yields around 90% were achieved for all four nitro compounds. The thermally coated Ti/TiO₂ electrode could be reused at least five times without any loss in yield and current efficiency.