Decomposition of NaBH4 with self-regeneration of carbon-supported CoCl2 catalyst

In this study, economically favorable CoCl₂ catalysts at four different amounts were supported on activated carbon (AC) for NaBH₄ dehydrogenation. Supported catalyst could achieve hydrogen release for 2,060 cycles, which is equivalent to 103 days of uninterrupted operation. Slow and continuous hydrogen release was observed in all experiments. Even 1 g of NaBH₄ can carry 1.2 L of hydrogen, and in hydrolysis process, it liberates 2.5 L of hydrogen that indicates the decomposition of water. EDX analysis and reverse burette measurements show that CoCl₂ could be homogeneously distributed on and permanently joined to the support surface. Kinetic investigation of the dehydrogenation reaction fits zero order kinetics, and activation energy was calculated to be 48 kJ/mol.     

Reductive dechlorination for remediation of polychlorinated biphenyls

Technologies such as thermal, oxidative, reductive, and microbial methods for the remediation of polychlorinated biphenyls (PCBs) have previously been reviewed. Based on energy consumption, formation of PCDD/F, and remediation efficiency, reductive methods have emerged as being advantageous for remediation of PCBs. However, many new developments in this field have not been systematically reviewed. Therefore, reductive technologies published in the last decade related to remediation of PCBs will be reviewed here. Three categories, including catalytic hydrodechlorination with H₂, Fe-based reductive dechlorination, and other reductive dechlorination methods (e.g., hydrogen-transfer dechlorination, base-catalyzed dechlorination, and sodium dispersion) are specifically reviewed. In addition, the advantages of each remediation technology are discussed. In this review, 108 articles are referenced.     

Catalytic reduction of water pollutants: knowledge gaps,lessons learned,and new opportunities

● Advances, challenges, and opportunities for catalytic water pollutant reduction. ● Cases of Pd-based catalysts for nitrate, chlorate, and perchlorate reduction. ● New functionalities developed by screening and design of catalytic metal sites. ● Facile catalyst preparation approaches for convenient catalyst optimization. ● Rational design and non-decorative effort are essential for future work. In this paper, we discuss the previous advances, current challenges, and future opportunities for the research of catalytic reduction of water pollutants. We present five case studies on the development of palladium-based catalysts for nitrate, chlorate, and perchlorate reduction with hydrogen gas under ambient conditions. We emphasize the realization of new functionalities through the screening and design of catalytic metal sites, including (i) platinum group metal (PGM) nanoparticles, (ii) the secondary metals for improving the reaction rate and product selectivity of nitrate reduction, (iii) oxygen-atom-transfer metal oxides for chlorate and perchlorate reduction, and (iv) ligand-enhanced coordination complexes for substantial activity enhancement. We also highlight the facile catalyst preparation approach that brought significant convenience to catalyst optimization. Based on our own studies, we then discuss directions of the catalyst research effort that are not immediately necessary or desirable, including (1) systematic study on the downstream aspects of under-developed catalysts, (2) random integration with hot concepts without a clear rationale, and (3) excessive and decorative experiments. We further address some general concerns regarding using H₂ and PGMs in the catalytic system. Finally, we recommend future catalyst development in both “fundamental” and “applied” aspects. The purpose of this perspective is to remove major misconceptions about reductive catalysis research and bring back significant innovations for both scientific advancements and engineering applications to benefit environmental protection.     

Efficient and recyclable palladium enriched magnetic nanocatalyst for reduction of toxic environmental pollutants

In this paper, highly stable, powerful, and recyclable magnetic nanoparticles tethered N-heterocyclic carbene-palladium(II) ((CH₃)₃[email protected]₃O₄) as magnetic nanocatalyst was successfully synthesized from a simplistic multistep synthesis under aerobic conditions through easily available low-cost chemicals. Newly synthesized (CH₃)₃[email protected]₃O₄ magnetic nanocatalyst was characterized from various analytical tools and catalytic potential of the (CH₃)₃[email protected]₃O₄ magnetic nanocatalyst was studied for the catalytic reduction of toxic 4-nitrophenol (4-NP), hexavalent chromium (Cr(VI)), Methylene Blue (MB) and Methyl Orange (MO) at room temperature in aqueous media. UV-Visible spectroscopy was employed to monitor the reduction reactions. New (CH₃)₃[email protected]₃O₄ magnetic nanocatalyst exhibited excellent catalytic activity for the reduction of toxic environmental pollutants. Moreover, (CH₃)₃[email protected]₃O₄ magnetic nanocatalyst could be easily and rapidly separated from the reaction mixture with the help of an external magnet and recycled minimum five times in reduction of 4-NP, MB, MO and four times in Cr(VI) without significant loss of catalytic potential and remains stable even after reuse.     

Removal of carbon disulfide via coupled reactions on a bi-functional catalyst: experimental and modeling results

A mathematical model describing the rate of carbon disulfide (CS₂) removal due to coupled reactions has been developed. Kinetic studies were carried out in a fixed bed reactor under atmospheric pressure and a range of temperatures (85–125 °C). The effects of flow rate, CS₂ inlet concentration, temperature and relative humidity were analyzed. A kinetic model based on axial dispersion, external and internal mass-transfer resistances, as well as effects of S deposition on the inner-face of the catalyst was in agreement with the CS₂ experimental breakthrough curves. The mathematical model can be used for process design and scale up of similar systems.     

应用生物制剂修复黑臭河涌试验研究

应用固定化生物催化剂(IBC)对江门市某河涌进行生物修复。结果表明:向底泥投加IBC能增加底泥中有益微生物量,优化底泥微生物群落,使河涌底泥中有机质逐渐降解;同时能抑制硫酸盐还原菌(SRB)繁殖,降低底泥中硫化物含量。试验进行4个月后,底泥有机质去除率达到54.7%⁶3.7%,底泥中SRB数量减少了92.8%63.7%,底泥中SRB数量减少了92.8%⁹4.5%,底泥硫化物含量降低了81.9%94.5%,底泥硫化物含量降低了81.9%⁸7.5%,河涌黑臭现象基本消除;向上覆水体投加IBC,在IBC中微生物和多种酶的协同作用下,水中有机污染物被快速降解,上覆水体的COD和氨氮浓度逐渐下降,试验进行4个月时,去除率分别达到20.0%87.5%,河涌黑臭现象基本消除;向上覆水体投加IBC,在IBC中微生物和多种酶的协同作用下,水中有机污染物被快速降解,上覆水体的COD和氨氮浓度逐渐下降,试验进行4个月时,去除率分别达到20.0%³5.2%和32.9%35.2%和32.9%⁴4.1%,提高了河涌的生物自净能力。     

Gasification of waste plastics by steam reforming in a fluidized bed

The process of producing synthetic gas from waste plastics by steam reforming was investigated. To evaluate this process, the steam reforming of the oils derived from low-density polyethylene and polystyrene were carried out using a laboratory-scale fluidized bed of Ni-Al₂O₃ catalysts. The performance of gasification in terms of carbon conversion, gas yield, and gas compositions was examined. Although oils derived from plastics contain many kinds of heavy hydrocarbons and aromatics, they were well gasified at temperatures above 1023 K with a steam/carbon ratio of 3.5 and a weight hourly space velocity of 1 h⁻¹. The hydrogen content of the product gas was very high at approximately 72 vol% for polyethylene-derived oil and 68 vol% for polystyrene-derived oil. These compositions agreed well with the values calculated from chemical equilibrium.     

“催化剂污水”处理工艺的改进

对“催化剂污水”处理工艺进行了分析，同时提出了改进意见。     

贫燃条件下汽车尾气氮氧化物净化催化剂的研究进展

由于汽车工业的迅速发展和能源的日益紧张,既经济又环保的汽车必将得到青睐.贫燃发动机可能成为一种选择,但是如何去除贫燃条件下产生的大量氮氧化物,就成为汽车尾气催化剂研究的新热点.在此主要分析了目前的一些最新研究成果,并对其发展趋势进行了展望.     

聚酯废气在Cu-Mn催化剂上的催化燃烧

在30Nm^3／h中试装置上研究了聚酯生产废气在Cu—Mn催化剂上的催化燃烧。研究表明，应用催化燃烧工艺能够连续平稳处理聚酯生产废气。其适宜操作条件是：催化燃烧反应器进口温度250℃，空速20000h^-1。经此条件处理后。总烃去除率达97．1％-99．6％，净化排气中总烃和乙醛浓度均小于100μL／L，符合国家排放标准。