Dynamic Reductive Kinetic Resolution of Benzyl Ketones using Alcohol Dehydrogenases and Anion Exchange Resins

Dynamic reductive kinetic resolutions of racemic 3‐arylalkanones have been performed by the proper combination of an alcohol dehydrogenase and a basic anionic resin. The best results were found for the bioreduction with the alcohol dehydrogenase type A from Rhodococcus ruber DSM 44541 overexpressed in Escherichia coli (E. coli/ADH‐A) and the commercially available evo‐1.1.200, while the Amberlite IRA‐440 C and the DOWEX‐MWA‐1 resins allowed efficient in situ racemizations. Reaction conditions were optimized in terms of enzyme source and loading, type and amount of resin, pH, temperature and reaction times, obtaining a series of (R,R)‐substituted propan‐2‐ols with good conversions and both diastereoselectivity and stereoselectivity. As a proof of concept, the subsequent intramolecular cyclization of a selected propan‐2‐ol substrate afforded a valuable isochroman heterocycle without any loss of the optical purity.

     

Single Nucleotide‐Catalyzed Biomimetic Reductive Amination

We have successfully developed a single nucleotide (adenosine 5′‐diphosphate)‐catalyzed enantioselective direct reductive amination of aldehydes and ketones using a Hantzsch ester as reducing agent. The process is a simple, efficient and a real mimic of the NADH reduction approach for the synthesis of structurally diverse amines. This reaction is the first report demonstrating the ability of a single nucleotide as catalyst and one of the most genuine biomimetic reactions of organic chemistry.     

Nickel‐Catalyzed Reductive Benzylation of Aldehydes with Benzyl Halides and Pseudohalides

The reductive benzylation of aromatic and aliphatic aldehydes with benzylic halides is reported using a nickel/zinc catalyst system. In addition to benzylic halides, the first report on the addition of benzylic triflates, acetates, tosylates and tritylates to aldehydes is also presented. By this new method a range of alcohols was synthesized efficiently from aldehydes and benzylic substrates at room temperature in moderate to high yields. The mild reaction conditions and good functional group tolerance make this nickel‐catalyzed process synthetically useful for the synthesis of diverse benzylic alcohols.

     

Enhanced PCE dechlorination by biobarrier systems under different redox conditions

The industrial solvent tetrachloroethylene (PCE) is among the most ubiquitous chlorinated compounds found in groundwater contamination. The objective of this study was to evaluate the (1) feasibility of enhancing PCE biodegradation using cane molasses and sludge cakes as the primary substrates under methanogenic and iron reducing conditions, and (2) potential of installation a sludge cake/cane molasses biobarrier to clean up PCE-contaminated aquifers. The biodegradability of sludge cake (from secondary wastewater treatment system) and cane molasses was tested using bioavailability experiments. Results show that biodegradable materials were released from sludge cake/cane molasses and utilized by microbial consortia. Based on the chemical oxygen demand (COD) tests, approximately 28 and 248 mg of biodegradable COD can be released from 1 g of sludge cake and 1 g of cane molasses under anaerobic conditions, which have the potential to convert 70 and 620 mg of PCE to ethylene (ETH), respectively. Reductive dechlorination was evaluated using microcosms containing primary substrates (sludge cake/cane molasses) and inocula (aquifer sediments). Results indicate that sludge cake and cane molasses can serve as the diffusion sources of primary substrates, and enhance the reductive dechlorination of PCE under methanogenic processes. However, results from this study were not sufficient enough to show that reductive dechlorination of PCE would occur under iron-reducing conditions. This indicates that more studies need to be performed to further evaluate the role of iron reduction on the PCE dechlorination. Results reveal that it is feasible and applicable to install a sludge cake or cane molasses biobarrier to clean up PCE contaminated aquifers. From an engineering point of view, the sludge cake/cane molasses biobarrier has the potential to become an environmentally and economically acceptable technology for PCE bioremediation.     

Chlorination and dechlorination of nuclear reactor cooling water

Effects from chlorination and dechlorination of Savannah River water were studied during the development of biofouling countermeasures for a proposed cooling tower system required for thermal mitigation of nuclear reactor cooling water effluent. Testing was conducted to assess chlorine demand and dissipation rates as well as the environmental acceptability of using sodium sulfite as a dechlorinating agent. Chlorine demand varied significantly, but in an unpredictable manner during seven seasonal sampling dates. A chlorine dosage of 3–5 mg/l was generally adequate to provide a free chlorine residual of 1 mg/l. Static 48-h bioassays with bluegill showed no acute toxicity for chlorinated/dechlorinated cooling water containing up to 64 times the calculated stoichiometric concentration of sodium sulfite required for dechlorination. Experiments measuring the depletion of dissolved oxygen and flow-through (96-h) bioassays with bluegill and largemouth bass further substantiated the environmental acceptability of using sodium sulfite as a dechlorinating agent.     

从砷锑烟尘中回收锑的实验研究

采用氯化—水解法从砷锑烟尘制取三氧化二锑,在砷锑烟尘经酸浸脱砷工序后,分别考察了水解时间、水解温度、稀释比对锑水解的影响和稀释比、氨水过量系数、反应时间及反应温度对氯氧锑脱氯的影响。结果表明,在稀释比为6∶1、温度为25℃和水解时间为1.5 h条件下水解,及在液固比为1.5∶1、反应温度为25℃、水解时间为0.5 h和氨水过量系数为1.5条件下脱氯,最后可得到砷锑烟尘中锑的回收率达到80.99%。     

RDX biodegradation column study: influence of ubiquitous electron acceptors on anaerobic biotransformation of RDX

A series of column studies, with aquifer material from the former Nebraska Ordinance Plant (NOP), were performed to explore the phenomenon of electron competition from ubiquitous inorganic electron acceptors (nitrate and sulfate) present in contaminated groundwater. Acetate was used as a source of readily biodegradable carbon in all of the treatment‐column systems. Influent hexahydro‐1, 3, 5‐trinitro‐1, 3, 5‐triazine (RDX) concentrations (1–1.8 mg dm^?3) were completely removed to below detection levels of 20 µg dm^?3 in all treatment‐column systems without any nitroso‐metabolites. In the control‐column system (with no carbon amendment) significant levels (～30% of the inlet molar RDX) of nitroso‐substituted RDX derivates were observed in the effluent stream. The estimated first‐order biodegradation rate coefficient for RDX was highest (0.79 h^?1) in the treatment‐column system where acetate was the only amendment, about 52 times higher than the rate coefficient (0.015 h^?1) obtained in the control‐column system. The presence of sulfate (100 mg dm^?3) in influent groundwater temporarily delayed the onset of RDX biotransformation without any adverse effects on overall RDX biotransformation. Coexistence of low (100 mg dm^?3) nitrate levels in the influent feed water reduced the first‐order biodegradation rate coefficient obtained in the absence of nitrate by about 80% to 0.16 h^?1. These nitrate levels, however, were low to halt the RDX biodegradation probably because the available carbon levels were high enough to exceed the demands for nitrate reduction. High levels of nitrate (500 mg dm^?3) initially halted RDX removal, and significantly reduced the rate of RDX biotransformation by about 98% to 0.02 h^?1, thereby increasing the half‐life from 0.9 h in the absence of nitrate to about 32 h, with noticeable levels of untreated RDX in the effluent stream. Contrary to the expectations, the presence of ammonium in conjunction with acetate resulted in a lower (0.09 h^?1) biodegradation rate coefficient as compared with the one obtained in the absence of ammonium. Copyright © 2003 Society of Chemical Industry     

催化重整装置的氯化铵结盐与腐蚀问题

由于胜利原油加工量的增加 ,致使催化重整装置原料油中氯含量大幅度上升 (设计值为 10 μg/g ,最高达 74 μg/g) ,因而造成氯化铵结盐并多次发生腐蚀泄漏事故。分析认为 :预加氢进料含水从而造成H2 S -HCl-H2 O腐蚀环境和铵盐水解是造成系统腐蚀的主要原因。与此同时 ,提出了增设并列脱氯罐及提高设备材质等建议。     

降低配电线路中线损的方法与措施

本文从技术和管理的两个角度，浅析配电线路中电能损耗的主要原因，简介解决的方法与措施。     

镁合金表面铁氧化物涂层的制备及其耐蚀性能

镁合金的耐蚀性差,严重限制了其在生物材料领域的应用。在镁合金表面采用化学还原法和溶剂热法复合制备了铁氧化涂层,利用扫描电镜(SEM)、X射线衍射(XRD)和能谱(EDS)等对样品的结构与组成进行表征,分别采用Tafel测试和磷灰石诱导试验评价了样品的耐蚀性和生物相容性。结果表明:涂层的主要组分为Fe3O4、Fe2O3和FeO;随着乙醇浓度降低和溶剂热时间延长,涂层粗糙度先降低后升高;Tafel测试表明,随着乙醇浓度的增加,涂层的耐蚀性先增高后降低;在乙醇浓度为90%,溶剂热时间4 h时获得的涂层表面无脱落现象,微裂缝数量最小,具有最高的耐腐蚀性能,极化电阻达51 779.2Ω,并具有良好的生物诱导活性。