Purified oxygenand nitrogen-modified multi-walled carbon nanotubes as metal-free catalysts for selective olefin hydrogenation

Oxygen and nitrogen-functionalized carbon nanotubes （OCNTs and NCNTs） were applied as metal-free catalysts in selective olefin hydro- genation. A series of NCNTs was synthesized by NH3 post-treatment of OCNTs. Temperature-programmed desorption, N2 physisorption, Raman spectroscopy, high-resolution transmission electron microscopy and X-ray photoelectron spectroscopy were employed to characterize the surface properties of OCNTs and NCNTs, aiming at a detailed analysis of the type and amount of oxygen- and nitrogen-containing groups as well as surface defects. The gas-phase treatments applied for oxygen and nitrogen functionalization at elevated temperatures up to 600 ℃ led to the increase of surface defects, but did not cause structural damages in the bulk. NCNTs showed a clearly higher activity than the pristine CNTs and OCNTs in the hydrogenation of 1,5-cyclooctadiene, and also the selectivity to cyclooctene was higher. The favorable catalytic properties are ascribed to the nitrogen-containing surface functional groups as well as surface defects related to nitrogen species. In contrast, oxygen-containing surface groups and the surface defects caused by oxygen species did not show clear contribution to the hydrogenation catalysis.

铂族金属的回收及溶液中铂的富集

我国铂资源短缺问题严峻,铂在化工、石油精炼、汽车尾气处理等行业不可或缺。原生铂矿储量有限、开采难,开采冶炼耗能多、成本高,还易导致矿区地表塌陷、植被破坏、废渣废水污染等环境问题。而废铂催化剂含大量铂金属,回收后可重复再利用。经济上,回收铂族金属能减少原生铂矿依赖,且成本低,企业效益高;环境方面,避免资源过度索取与环境破坏,降低废弃物排放,契合资源循环与环保理念,有利于我国可持续发展。介绍了从铂族二次资源中回收铂的方法,重点介绍浸出及溶液中铂富集的工艺和相应的优势和不足,以及目前主流的回收方法和对未来回收铂的展望。

Separation of Pd and Pt from highly acidic leach liquor of spent automobile catalysts with monothio-Cyanex 272 and trioctylamine

Platinum group metals(PGMs),especially Pd,Pt,and Rh,have drawn great attention due to their unique features.Direct separation of Pd and Pt from highly acidic automobile catalyst leach liquors is disturbed by various factors.This work investigates the effect of various parameters including the acidity,extractant concentration,phase ratio A/O,and diluents on the Pd and Pt extraction and their stripping behaviors.The results show that the Pd and Pt are successfully separated from simulated leach liquor of spent automobile catalysts with monothioCyanex 272 and trioctylamine(TOA).Monothio-Cyanex 272 shows strong extractability and specific selectivity for Pd,and only one single stage is needed to recover more than 99.9% of Pd,leaving behind all the Pt,Rh,and base metals of Fe,Mg,Ce,Ni,Cu,and Co in the raffinate.The loaded Pd is efficiently stripped by acidic thiourea solutions.TOA shows strong extractability for Pt and Fe at acidity of 6 mol·L^(–1) HCl.More than 99.9% of Pt and all of the Fe are extracted into the organic phase after two stages of countercurrent extraction.Diluted HCl easily scrubs the loaded base metals(Fe,Cu,and Co).The loaded Pt is efficiently stripped by 1.0 mol·L^(–1) thiourea and 0.05–0.1 mol·L^(–1) Na OH solutions.Monothio-Cyanex 272 and TOA can realize the separation of Pd and Pt from highly acidic leach liquor of spent automobile catalysts.

Study on the Leaching of Pt, Pd and Rh from Spent Auto-catalysts in Various Acidities

Auto-catalysts were the largest consumers of platinum group metals and the most important secondary resources, recovery of PGMs from spent auto-catalysts by leaching with various acidities were investigated. The leaching thermodynamics of PGMs at 363 K was first discussed. At 363 K the higher the acidities of HCl, the higher the leaching recoveries of PGMs, and the sequence of leaching recovery was Pd>Pt>Rh. When H2SO4 used alone, the leaching recoveries of PGMs was low, when the acidity of H2SO4 increasing, the leaching recovery of Rh kept stable.

Pd(111)与Pt(111)上NO氧化的第一性原理研究

随着排放法规的日益严格,发动机的氮氧化物(NO_(x))后处理已成为当今研究的重点问题.针对目前可有效降低稀燃汽油机NO_(x)的稀燃氮氧化物捕集器中铂(Pt)和钯(Pd)两种贵金属之间的替换问题,进行了密度泛函理论(density functional theory,DFT)计算研究.首先,对一氧化氮(NO)、氧气(O_(2))、二氧化氮(NO_(2))在两种催化剂(111)表面的吸附进行了研究,之后,在两催化剂表面对比研究了氧化过程中涉及的O_(2)解离与NO氧化两反应过程,揭示了NO在Pd与Pt催化剂上的氧化机理.结果显示:3种物质在催化剂表面的吸附强度为NO>O_(2)>NO_(2).氧覆盖度将会改变氮氧化物的最佳吸附构型,随着表面氧原子的增加NO会由三重空位式吸附转变为顶点吸附,NO_(2)会由μ-N,O-亚硝基吸附转变为硝基吸附.在O_(2)解离过程中Pt的催化能力优于Pd,但是两者对NO氧化的催化能力接近.在Pd和Pt表面反应限速步骤都是O_(2)的解离,Pd对O_(2)较弱的解离能力导致了其NO的转化效率低于Pt.氧覆盖度对氧化过程存在影响,通过电子结构分析发现,氧覆盖度的提升使催化剂与吸附物质之间的吸附能下降,这导致了反应由吸热变为放热,使催化可以自发进行.反应生成的NO_(2)需要1.00 eV以上的能量完成脱附,这在原子层面解释了NO_(2)对NO氧化反应的抑制作用.

Solar-assisted selective separation and recovery of precious group metals from deactivated air purification catalysts

The mitigation of environmental and energy crises could be advanced by reclaiming platinum group precious metals(PGMs) from decommissioned air purification catalysts. However, the complexity of catalyst composition and the high chemical inertness of PGMs significantly impede this process. Consequently,recovering PGMs from used industrial catalysts is crucial and challenging. This study delves into an environmentally friendly approach to selectively recover PGMs from commercial air purifiers using photocatalytic redox technology. Our investigation focuses on devising a comprehensive strategy for treating three-way catalysts employed in automotive exhaust treatment. By meticulously pretreating and modifying reaction conditions, we achieved noteworthy results, completely dissolving and separating rhodium(Rh), palladium(Pd), and platinum(Pt) within a 12-h time frame. Importantly, the solubility selectivity persists despite the remarkably similar physicochemical properties of Rh, Pd, and Pt. To bolster the environmental sustainability of our method, we harness sunlight as the energy source to activate the photocatalysts, facilitating the complete dissolution of precious metals under natural light irradiation. This ecofriendly recovery approach demonstrated on commercial air purifiers, exhibits promise for broader application to a diverse range of deactivated air purification catalysts, potentially enabling implementation on a large scale.

从含钌废料中回收钌的研究进展

从铂族金属废料中回收再利用钌对于实现行业可持续发展、节约资源和环境保护都有着重大影响。钌废料一般包括含钌废催化剂、含钌合金材料、含钌核废料和其他含钌废料等。综述了不同钌废料的综合回收处理方法,分别介绍了氧化蒸馏法转化可溶性盐、熔融—还原—氧化法、熔融—氧化—蒸馏法、微波浸出—浊点萃取法、蒸馏—熔融—还原法、熔融—还原—氧化法、离子交换法、氧化挥发法、电解法、生物吸附法和物理吸附法等工艺,总结了现有钌废料回收技术的优缺点,并对未来钌废料回收工艺的发展方向进行了展望。

失效三元催化剂回收铂族金属研究进展

我国铂族金属(Platinum Group Metals,PGMs)储量少,消费量大,其安全供应是我国战略性新兴产业可持续发展的关键环节。失效汽车三元催化剂作为回收PGMs(铂、钯、铑)的重要来源,如何全面构建高效、绿色的PGMs回收体系,实现“变废为宝”,近年来受到广泛关注。首先对汽车三元催化剂的工作原理、催化剂失效机理和失效催化剂难以浸出PGMs的原因进行了介绍。然后概述了当前失效三元催化剂中贵金属富集技术的研究进展,总结了各种技术的原理、流程及优缺点。针对火法回收技术(铅捕集、铜捕集、铁捕集、锍捕集和氯化挥发法)、湿法浸出技术(氯化浸出、氰化浸出和载体溶解法浸出)、有机溶剂浸出技术、微波辅助浸出技术、碘浸出和生物浸出等传统方法存在的反应条件苛刻、易产生高污染有毒有害废液废气、规模化生产困难、反应缓慢等不足,详细介绍了新报道的光催化浸出PGMs技术,其具有操作简单、环境友好、适用于各种PGMs浸出的优点,因此可以在无强酸、强碱的条件下,通过光催化反应实现汽车三元催化剂中的PGMs浸出。最后总结并提出了PGMs浸出技术未来的研究与发展方向,为PGMs资源回收领域研究提供了重要参考。

Slag design and optimization for iron capturing platinum group metals from alumina-based spent catalysts

Production of petrochemical catalysts accounts for one of the largest shares of platinum group metals(PGMs) consumption;thus,recycling of spent petrochemical catalysts holds great economic value.Conventionally,PGMs are recovered through hydrometallurgical processes which have a low recovery efficiency and produce a large amount of waste.In this regard,this paper proposed a method to use iron-capturing PGMs based on CaO-Al_(2)O_(3)-Na_(2)O slag.This method avoided the formation of Fe-Si alloy and achieved efficient enrichment of PGMs.The droplet force model showed that the recovery efficiency of PGMs could be improved if the slag had low density and low viscosity.Based on this result,FactSage software optimized the composition of slag.Furthermore,the effect of B_(2)O_(3) on the 1400 ℃ liquidus of CaO-Al_(2)O_(3)-Na_(2)O_(3)-B_(2)O_(3) phase diagram was revealed.Moreover,it was found that the recovery efficiency of PGMs exceeded 99% under the following optimized conditions:basicity of 1.0,20 wt%Na_(2)O,15 wt% B_(2)O_(3),15 wt% Fe,3 wt% C and a temperature range of 1400-1500℃.The thermodynamic model revealed the mechanism of iron capture.Different chemical bonds prevented the formation of bonds between the alloy and slag,resulting in the separation of the slag from the alloy.PGMs particles and iron microspheres had significant surface Gibbs free energy.Only when iron microspheres and PGMs particles collided and fused with each other to reduce their surface area could the Gibbs free energy of the system be reduced.

非金属掺杂提升铂族金属电催化剂性能

铂族金属(PGM)催化剂被认为是用于能量转换和存储设备(如燃料电池和水电解器)的最佳催化剂之一,但活性和稳定性不足极大地限制了其商业化应用.近年来,非金属原子(氢、硼、碳、氮、磷和硫等)掺杂策略引起了广泛关注,该方法可以对铂族金属的精细电子和配位结构进行调控,从而优化铂族金属的电催化活性和稳定性.非金属掺杂具有独特的优势:首先,非金属的原子半径较小,可以进入铂族金属的间隙位点,为调节铂族金属的电子结构提供了更多的可能性;其次,掺杂的非金属会诱导强电荷转移,并与主体金属产生s,p-d杂化,这与金属-金属合金中的d-d轨道耦合不同;第三,非金属掺杂的铂族金属基催化剂由于具有较强的非金属-金属键,从而表现出较好的耐久性.本文详细探讨了非金属掺杂铂族金属催化剂的合成和应用,并揭示了非金属掺杂的催化机理和构效关系.本文总结了非金属掺杂铂族金属基催化剂在电催化领域的一些代表性进展,讨论了影响催化剂活性和稳定性的关键因素,并介绍了非金属掺杂改善铂族金属基催化剂性能的基本原理.探讨了非金属掺杂铂族金属基催化剂的表征技术和理论方法,其中包括可直接观测到非金属原子的先进成像技术以及原位表征方法,辅助以密度泛函理论以及分子动力学模拟等理论计算方法,以进一步揭示催化剂性能增强机制.详细列举了非金属掺杂铂族电催化剂的合成方法,从气相沉积、高温热解、湿化学合成到电化学原位合成,提供了详尽的合成方案,并提出了针对贵金属活性中心的非金属修饰策略,旨在为未来材料设计提供启示.概述了非金属掺杂铂族金属基催化剂在电催化中的应用,重点揭示了非金属掺杂带来的结构-性能构效关系.在活性方面,非金属掺杂可以从配体效应、应力效应、微应变等方面影响铂族金属的d带重心,从而影响活性位点与反应中间体的吸附,而这种影响作用也因每种非金属的电负性、原子半径、掺杂方式等不同而不同,可通过调控掺杂种类/方式实现精细调控;同时,非贵金属的协同效应可以增强对OH的吸附,抑制活性位点的毒化.在稳定性方面,非金属可以通过与金属形成稳定的金属-非金属键抑制金属的溶解,或者减弱金属与氧的相互作用,防止其被氧化;同时,非金属的掺入可以提高金属的功函数,提高其溶解电位,从而提升催化剂稳定性.最后,本文提出了该类电催化材料面临的机遇和挑战,其中包括:(1)开发更加可控的非金属掺杂策略;(2)更加深入地研究非金属掺杂带来的构效关系;(3)探索新的非金属掺杂催化剂,并进一步拓展到其他催化领域;(4)发展抑制非金属组分溶解的通用策略;(5)重视催化剂在器件层面的性能评估.综上,本文不仅为非金属掺杂贵金属基催化剂进一步的研究提供启示,还为深入理解催化、纳米材料的合成提供参考.

失效汽车催化剂中铂族金属火法富集概述

铂族金属作为重要的战略资源,在军事、航天、半导体、汽车等行业中有着广泛的应用,对于我国的发展起着不可或缺的作用。本文综述了目前失效汽车催化剂中铂族金属的火法回收现状,总结了各种方法的工艺流程和目前主要应用方向,包括金属捕集法中使用不同捕集剂造成的机理差异。对主要工艺路线存在的优缺点进行分析评述并提出改进方向。当下应大力发展协同捕集新技术,在保证回收率的同时还要控制富集后的合金成分以便于精炼,达成不同捕集剂之间的优势互补,为实现未来更加高效、绿色的铂族金属二次资源回收。

失效汽车尾气催化剂中铂族金属回收的研究进展

失效汽车尾气催化剂是回收铂族金属(铂、钯、铑)的重要二次资源。本文介绍了失效汽车尾气催化剂中铂族金属的回收工艺流程,包括失效催化剂预处理、铂族金属富集、分离与精炼三部分;详细介绍了两种高效预处理技术、两种富集方法以及四种分离与精炼工艺,总结了各种方法的原理、工艺流程、优缺点及改进方向。回收企业应根据回收规模和环保政策采用合适的回收工艺,以实现不同回收工艺之间的优势互补,未来需重点研发回收率高且环境友好的清洁回收工艺。

电加热催化器降低混合动力车辆排放的应用研究

为了应对全球越来越严苛的汽车排放法规,例如欧7、北美Tier3Bin30以及未来的国7,降低整车排放势在必行,而缩短发动机冷起动阶段的催化器起燃时间将是关键点。将着重研究电加热催化器在混合动力车辆上的应用开发,以达到更好的排放结果。

磁铁矿金属化焙烧高温捕集催化剂浸出渣回收铂族金属研究

针对汽车催化剂氧化浸出渣,开展磁铁矿金属化焙烧高温捕集回收铂族金属研究。重点研究捕集剂、还原剂、助熔剂、反应温度、反应时间对铂族金属捕集率的影响。试验结果表明,捕集剂配比20%,还原剂配比12%、助熔剂配比25%、焙烧温度1400℃、恒温反应时间4 h条件下,铂族金属铂、钯、铑的捕集率分别可达97.19%、92.88%、97.08%。

基于金属-氮-碳结构催化剂的质子交换膜燃料电池研究进展

质子交换膜燃料电池(PEMFC)可以直接将储存在氢中的化学能无污染地转化为电能,是实现碳减排和碳中和的关键新能源技术。目前的PEMFC技术,尤其是在发生氧还原反应的阴极,还严重依赖铂基贵金属催化剂,导致了燃料电池高昂的成本,限制了其大规模应用。因此,人们对于研究基于低成本非贵金属催化剂的PEMFC展现出了极大的兴趣。自从采用金属-氮-碳结构催化剂作为贵金属催化剂的替代品以来,非铂基PEMFC取得了很多突破,但是当前其在活性和稳定性的表现仍不能令人满意。本文总结了基于金属-氮-碳催化剂的PEMFC性能与活性位点、催化剂结构和催化层结构之间的关系,揭示了催化剂结构对于PEMFC中物质传输的重要作用。另外,为了满足实际需求,本文也总结并讨论了PEMFC可能的失活机理,包括脱金属作用,氮物种的质子化,碳载体腐蚀和孔道水淹等,以及目前发展的可能的解决方案。基于这些认识,本文最后介绍了在提升金属-氮-碳基PEMFC的活性和稳定性方面的最新进展与策略。

铂族金属均相催化剂的研究和应用

铂族金属均相催化剂是一类特殊结构的金属配合物,具有均相催化氢化反应、羰基加成反应、酰氢化反应、烯烃氧化反应、C-C合成反应等的作用,在现代化学和制药工业中得到重要的应用。涉及的催化机理主要包括氧化加成、分子内配体重排、配体迁移和插入、还原消除。论文介绍和讨论了铂族金属均相催化剂的历史、应用、催化机制和最新的进展。

加压碱浸处理-氰化浸出法回收汽车废催化剂中的贵金属

为提高铂族金属的浸出回收率,针对前期研究提出的汽车废催化剂先经加压碱浸处理而后再加压氰化浸出铂族金属的新工艺,变动预处理反应过程各种工艺参数,考察了对后续铂族金属氰化浸出指标的影响。结果表明:预处理可打开汽车废催化剂载体对铂族金属的包裹,有利于其氰化浸出;但物料粒度过细或反应碱用量过大、温度过高、时间过长均容易形成新相重新包裹,不利于氰化试剂与铂族金属有效接触;预处理渣进一步湿磨,可消除包裹,提高氰化浸出率;在实验最佳条件下,铂族金属氰化浸出率分别可达到:Pt 96%、Pd 98%、Rh92%。

从废催化剂中回收铂族金属的湿法工艺研究

铂族金属已被广泛地应用于各种催化剂中,废催化剂是再生回收铂族金属的重要原料。本文介绍了近年来采用预处理、溶浸、分离和提取等湿法冶金过程,从废催化剂中回收铂族金属的方法和技术,并对这些方法的优缺点进行了比较。

熔炼法从失效汽车尾气催化剂中富集回收铂钯铑

采用火法熔炼技术对失效汽车尾气催化剂中铂族金属的熔炼富集进行了研究。主要考察捕集剂、还原剂、造渣剂等用量对铂钯铑综合回收率的影响。最佳熔炼工艺条件:反应时间4h、捕集剂Fe3O4用量为物料量的20%、还原剂用量9%、CaO用量40%、熔炼温度1 450℃,金属铂钯铑的综合回收率可达到97%以上。熔炼产物PGM-Fe合金的主要成分是单质铁,含量为91%~93%,铂族金属含量在4%~5%。

铜捕集法从失效汽车催化剂中回收铂、钯和铑的研究

采用铜捕集法从失效汽车催化剂中回收铂族金属,重点研究了Ca O/Si O2质量比、捕集剂、熔炼温度和时间、以及还原剂对Pt、Pd和Rh回收率的影响。结果表明,在Ca O/Si O2=1.05,Cu O配比35%~40%,还原剂配比6%,熔炼温度1400℃,熔炼时间5 h的条件下,Pt、Pd和Rh回收率分别为98.2%、99.2%和97.6%。