浅析氨汽提法尿素装置如何实现排塔零污染

根据生产状况分析在排塔过程中NH3对环境造成的危害的探讨并对操作方案进行分析总结。     

DMC与苯胺合成苯氨基甲酸甲酯的热力学分析

苯氨基甲酸甲酯是非光气法生产MD I的重要原料,碳酸二甲酯(DMC)与苯胺甲氧羰基化法是合成苯氨基甲酸甲酯最有前途的方法之一。文中用基团贡献法计算了该反应体系的反应热、吉布斯自由能变化、化学反应平衡常数,所得结果可指导实验室研究及工业放大。     

Influence of the distillation processes from Rio de Janeiro in the ethyl carbamate formation in Brazilian sugar cane spirits

Ethyl carbamate (EC) or urethane, a potentially carcinogenic substance found in significant amounts in distilled fermented beverages, has become the main technical obstacle to the exportation of Brazilian sugar cane spirits (cachaças). In this evaluation, the EC levels were measured in samples of recently distilled beverages and of finished products, collected at 28 production plants using different distillation systems, from various regions of the state of Rio de Janeiro. The results obtained through GC–MS, using selective monitoring of ions with m/z 62 and 74, showed that approximately 45% of the products and raw materials are above the maximum allowed value of 150 μg/l, with an EC average value of 160 μg/l. The lower values were those for samples from alembics using low temperature and high reflux rate distillation, which emphasized the role of these two variables on the EC levels.     

Safe apples for baby-food production: Survey of pesticide treatment regimes leaving minimum residues

A total of 19 pesticide preparations were used according to agricultural practice in six trials in apple orchards. Using gas chromatography-mass spectrometry (GC-MS) and liquid chromatography-tandem mass spectrometry (LC-MS/MS), premature Golden Delicious apples collected 64, 50, 36 days before harvest and mature fruit were examined for residues of active ingredients. No residues of triflumuron, triazamate, chlorpyrifos, etofenprox, fenoxycarb, kresoxim-methyl, cyprodinyl, difenoconazole or thiram were detected in the first sampling. Also, the levels of chlorpyrifos-methyl, penconazole, tebuconazole and tolylfluanid dropped during the pre-harvest interval. Detectable residues of pyridaben, thiacloprid, trifloxystrobin and tetraconazole in harvested fruits were below 0.01 mg kg^-1, which is the maximum concentration of residues acceptable by baby-food producers in any raw material. The only residues exceeding this concentration were captan and teflubenzuron. Based on the data, farmers can choose pesticides for optimal treatment of plants, while enabling growth of a safe crop suitable for baby-food production.     

Levels of chlorinated pesticides and polychlorinated biphenyls in Norwegian breast milk (2002-2006), and factors that may predict the level of contamination

In the present study, polychlorinated biphenyls (PCBs) and organochlorine pesticides (OCPs) were determined in 423 breast milk samples from women living in Norway. Various predictors for the contaminant levels were also investigated. The samples were collected in six counties, representing South, Central and North Norway in 2002-2006. Initial results showed significantly lower levels of OCPs in breast milk from ethnic Norwegians (N = 377) compared to ethnic non-Norwegians (N = 46). Median concentrations (range) of PCBs, p,p′-DDE, HCB, β-HCH and oxychlordane in breast milk of the Norwegian women, all parities included, were 103 (34-450), 41 (5.4-492), 11 (3.6-24), 4.7 (0.9-37) and 2.8 (0.5-16) ng/g lipid weight, respectively. Results indicated that sum of 18 PCBs, p,p′-DDE and β-HCH are good predictors for monitoring of PCB, DDT and HCH levels in Norwegian breast milk. Multivariable linear regression analyses showed that age was strongly associated with increasing OC levels (P < 0.001), whereas parity was associated with decreasing OC levels (P < 0.001). Smoking was associated with higher levels of PCBs, p,p′-DDE and β-HCH. The models explained from 17 to 35% of the variance. Median levels of OCs in the present Norwegian primparaes seemed to be 29-62% lower than corresponding results found in a Norwegian study from 2000-2002.     

Application of ultrasound-assisted emulsification-micro-extraction for the analysis of organochlorine pesticides in waters

Ultrasound-assisted emulsification-micro-extraction (USAEME) procedure was developed for the determination of different organochlorine pesticides (OCPs) in water samples by gas chromatography with μ-electron capture detection (GC-μECD). After the determination of the most suitable extraction solvent and its volume, parameters such as extraction time, centrifugation time and ionic strength of the sample were optimized by using a 2³ factorial experimental design. For 10 mL of water sample, the optimized USAEME procedure used 200 μL of chloroform as extraction solvent, 15 min of extraction without ionic strength adjustment at 25 °C and 5 min of centrifugation at 4000 rpm. Limits of detection ranged from 0.002 to 0.016 μg L⁻¹. Mean recoveries of OCPs from fortified water samples are over 96% for three different fortification levels between 0.5 and 5 μg L⁻¹ and relative standard deviations of the recoveries are below 9%. The developed procedure was successfully applied for real water samples (i.e., tap water, well water, surface (lake) water, domestic and industrial wastewater). Performance of the procedure was compared with those involving traditional liquid-liquid extraction and solid-phase extraction. The result demonstrates that the USAEME procedure is viable, rapid and easy to use for analysis of OCPs in water samples.     

Potential formation of ethyl carbamate in simulated wine inoculated with Oenococcus oeni and Lactobacillus plantarum

The production of ethyl carbamate (EC) and its precursor citrulline by two strains of Oenococcus oeni and one of Lactobacillus plantarum during malolactic fermentation (MLF) was studied in different conditions of pH, temperature, and ethanol and l -malic acid concentrations. The potential EC, defined as the concentration of EC after wine is heated at 80 °C for 48 h, was also investigated. The O. oeni strains were able to degrade arginine in the conditions studied and to excrete some citrulline. In these strains, the conditions that led to a slight increase in EC were a high ethanol concentration, low pH and a high l -malic acid concentration. However, the potential EC increased with higher pH. In the case of L. plantarum , arginine was not degraded and citrulline was not produced, although the potential EC was comparable with that of the O. oeni strains studied.     

The Quality of Drinking Water at Source of West Amman,Jordan

Abstract

In the summer of 2002, a detailed survey of water samples collected from King Abdullah Canal (KAC), which is the major source of drinking water in Amman, Jordan, was analyzed for its major ionic composition, five heavy metals, 16 polycyclic aromatic hydrocarbons (PAH), and chlorinated pesticides residues in order to evaluate its suitability for drinking purposes. The results showed that the major source of chemical constituents and micropollutants such as heavy metals, PAH, and organochlorinated pesticides in the canal water samples originated from Syria and Israel since the canal water supply initially originate from these countries. The pH values of all analyzed water samples obtained were relatively high due to the buffering effect of carbonate rocks at the source. The major chemical composition indicated that the canal water was weak to moderate salinity dominated by Ca, Mg, and HCO₃ ions, which is due to the dolomite lithology at source. Despite the fact that the canal water runs in an intensive agricultural area, the analysis of this study concludes that the water of the canal is acceptable in terms of its organic and inorganic constituents. All samples showed low concentrations and were within their guidelines. Nitrate values ranged from 2.2 ppm to 13.2 ppm, organochlorinated pesticides ranged from 0.11 ppm to 0.82 ppm for individual pesticides, and the sum did not exceed the European guideline of 0.5 ppm. Ten PAHs were detected in the analyzed samples ranging from 24.45 ng/l to 35.4 ng/l and in all samples; no concentration reached the maximum level permitted by the EPA for drinking water. All samples showed a slight increase in concentration along the canal flow.     

尿素醇解法合成碳酸二甲酯催化精馏工艺的模拟

采用非平衡级模型对尿素醇解法合成碳酸二甲酯(DMC)催化精馏工艺的塔内组分、流量及温度分布进行模拟,以Max-well-Stefan方程计算汽液组分的传质速率和各组分的Murphree级效率。计算结果表明,不同组分的Murphree级效率差别较大。催化精馏塔的反应段、精馏段和提馏段温度分别为180.2,136.1,150.0℃,模型预测结果与实测值吻合较好。模拟与实验结果均表明,在1.0MPa压力下,升高反应温度,DMC收率增加,而反应段汽液流量减小。对于不同的反应温度,精馏段温度受组分沸点限制,保持为136.0℃。在1.0MPa压力下,最佳反应段温度应控制在180.0～185.0℃之间,DMC收率为49.29%～57.91%。     

Artificially phase-separated binary self-assembled monolayers composed of 11-amino-1-undecanethiolate and 10-carboxy-1-decanethiolate on Au(1 1 1): A comparative study of two preparing methods

Two methods have been compared for preparing artificially phase-separated two-component SAMs on Au(1 1 1) composed of 11-amino-1-undecanethiolates (AUTe) and 10-carboxyl-1-decanethiolates (CDTe), which would form, thermodynamically, a homogeneously mixed binary SAMs. The first method starts with the formation of a phase-separated binary SAM of AUTe and 2-hydroxy-1-ethanethiolate (HETe) as a template of the artificially phase-separated SAM, followed by the selective desorption of HETe domains and succeeding filling of the vacancy with CDTe. The second method utilizes fluoren-9-ylmethyl N-(11-mercaptoundecyl) carbamate (FMUCe) instead of 11-amino-1-undecanethiol in preparing the template. After the filling with CDTe, the 9-fluorenylmethyloxycarbonyl (Fmoc) group is removed to obtain AUTe domains. Both methods yield artificially phase-separated binary SAMs having AUTe domains of tens nanometer across. The molecularly flat SAM surface with nanometer-scale domains of different acid-base and electrostatic properties are thus created. For preparing binary SAMs with a higher degree of phase separation, the second method is a better choice; a more clear-cut phase separation is achieved.