In situ formation of multiple catalysts for enhancing the hydrogen storage of MgH_(2) by adding porous Ni_(3)ZnC_(0.7)/Ni loaded carbon nanotubes microspheres

MgH_(2) is considered one of the most promising hydrogen storage materials because of its safety,high efficiency,high hydrogen storage quantity and low cost characteristics.But some shortcomings are still existed:high operating temperature and poor hydrogen absorption dynamics,which limit its application.Porous Ni_(3)ZnC_(0.7)/Ni loaded carbon nanotubes microspheres(NZC/Ni@CNT)is prepared by facile filtration and calcination method.Then the different amount of NZC/Ni@CNT(2.5,5.0 and 7.5 wt%)is added to the MgH_(2) by ball milling.Among the three samples with different amount of NZC/Ni@CNT(2.5,5.0 and 7.5 wt%),the MgH_(2)-5 wt%NZC/Ni@CNT composite exhibits the best hydrogen storage performances.After testing,the MgH_(2)-5 wt%NZC/Ni@CNT begins to release hydrogen at around 110℃ and hydrogen absorption capacity reaches 2.34 wt%H_(2) at 80℃ within 60 min.Moreover,the composite can release about 5.36 wt%H_(2) at 300℃.In addition,hydrogen absorption and desorption activation energies of the MgH_(2)-5 wt%NZC/Ni@CNT composite are reduced to 37.28 and 84.22 KJ/mol H_(2),respectively.The in situ generated Mg_(2)NiH_(4)/Mg_(2)Ni can serve as a"hydrogen pump"that plays the main role in providing more activation sites and hydrogen diffusion channels which promotes H_(2) dissociation during hydrogen absorption process.In addition,the evenly dispersed Zn and MgZn2 in Mg and MgH_(2) could provide sites for Mg/MgH_(2) nucleation and hydrogen diffusion channel.This attempt clearly proved that the bimetallic carbide Ni_(3)ZnC_(0.7) is a effective additive for the hydrogen storage performances modification of MgH_(2),and the facile synthesis of the Ni_(3)ZnC_(0.7)/Ni@CNT can provide directions of better designing high performance carbide catalysts for improving MgH_(2).

High Fe‑Loading Single‑Atom Catalyst Boosts ROS Production by Density Effect for Efficient Antibacterial Therapy

The current single-atom catalysts(SACs)for medicine still suffer from the limited active site density.Here,we develop a synthetic method capable of increasing both the metal loading and mass-specific activity of SACs by exchanging zinc with iron.The constructed iron SACs(h^(3)-FNC)with a high metal loading of 6.27 wt%and an optimized adjacent Fe distance of~4 A exhibit excellent oxidase-like catalytic performance without significant activity decay after being stored for six months and promising antibacterial effects.Attractively,a“density effect”has been found at a high-enough metal doping amount,at which individual active sites become close enough to interact with each other and alter the electronic structure,resulting in significantly boosted intrinsic activity of single-atomic iron sites in h^(3)-FNCs by 2.3 times compared to low-and medium-loading SACs.Consequently,the overall catalytic activity of h^(3)-FNC is highly improved,with mass activity and metal mass-specific activity that are,respectively,66 and 315 times higher than those of commercial Pt/C.In addition,h^(3)-FNCs demonstrate efficiently enhanced capability in catalyzing oxygen reduction into superoxide anion(O_(2)·^(−))and glutathione(GSH)depletion.Both in vitro and in vivo assays demonstrate the superior antibacterial efficacy of h^(3)-FNCs in promoting wound healing.This work presents an intriguing activity-enhancement effect in catalysts and exhibits impressive therapeutic efficacy in combating bacterial infections.

Defect engineering of high-loading single-atom catalysts for electrochemical carbon dioxide reduction

Electrochemical carbon dioxide reduction reaction(CO_(2)RR)provides an attractive approach to carbon capture and utilization for the production high-value-added products.However,CO_(2)RR still suffers from poor selectivity and low current density due to its sluggish kinetics and multitudinous reaction pathways.Single-atom catalysts(SACs)demonstrate outstanding activity,excellent selectivity,and remarkable atom utilization efficiency,which give impetus to the search for electrocatalytic processes aiming at high selectivity.There appears significant activity in the development of efficient SACs for CO_(2)RR,while the density of the atomic sites remains a considerable barrier to be overcome.To construct high-metal-loading SACs,aggregation must be prevented,and thus novel strategies are required.The key to creating high-density atomically dispersed sites is designing enough anchoring sites,normally defects,to stabilize the highly mobile separated metal atoms.In this review,we summarized the advances in developing high-loading SACs through defect engineering,with a focus on the synthesis strategies to achieve high atomic site loading.Finally,the future opportunities and challenges for CO_(2)RR in the area of high-loading single-atom electrocatalysts are also discussed.

Synthesis of glycerin triacetate over molding zirconia-loaded sulfuric acid catalyst

Zirconia-loaded sulfuric acid （SO2-/ZrO2） catalysts were prepared by impregnation method, molded by punch tablet machine and characterized by X-ray diffraction. SO4^2-/ZrO2 catalyst was used to obtain glycerol triacetate （GTA） directly from glycerin. The effect of some factors, such as different temperatures of calcination and catalysts molded or not, on the reusable times of catalysts and the yield of GTA were investigated. The optimum reaction conditions were shown as follows： the reaction temperature was 403 K; the reaction time continued for 8 h; the amount of molded catalysts was 5 wt% of glycerin and the molar ratio of glycerin to acetic acid was 1 ： 8. The yield of GTA was 97.93% under the optimum condition.

Study on Relationship between Microstructure of Active Phase and HDS Performance of Sulfided Ni-Mo Catalysts: Effect of Metal Loading

Six Ni-Mo catalysts with different metal contents were prepared and characterized by N2 adsorption and X-ray diffi＇actometry. The active phase microstructure of these catalysts was examined by the Raman spectroscopy, temperature- programmed reduction （TPR）, X-ray photoelectron spectroscopy, and high-resolution transmission electron microscopy. Hydrodesulfurization （HDS） activity of catalyst samples were analyzed in a flow fixed-bed microreactor. The sulfidation degree of Mo and the length of the MoS2 slab slightly increased with the amount of metal loaded following sulfidation. This small change is attributed to polymolybdate species observed in all the oxidized catalysts. Weak metal-support interactions, as determined by the TPR technique, increased the NiSx sulfidation phase and MoS2 slab stacking. The HDS activity of the catalyst samples increased with the number of active sites. For high metal loading catalysts, their HDS activity was nearly identical because the sulfur atoms cannot easily approach active sites. This change is caused by the large number of stacked layers in the MoS2 slabs as well as the decrease in the specific surface area and pore volume of the catalyst samples with an increasing metal loading.

Effect of Sr loading on oxydehydrogenation of propane to propylene over Al_2O_3-supported V-Mo catalysts

Incorporation of strontium into V-Mo alumina-supported catalyst enhanced its performance (increased conversion and selectivity,decreased reducibility and improved stability) in propane oxydehydrogenation to propylene.12.5% Sr loading was shown to be the optimum content to the V-Mo catalyst.The results were supported by various characterization techniques,namely,BET,XRD,SEM,FTIR and TPD.

High-performance proton exchange membrane fuel cell with ultra-low loading Pt on vertically aligned carbon nanotubes as integrated catalyst layer

Reducing a Pt loading with improved power output and durability is essential to promote the large-scale application of proton exchange membrane fuel cells(PEMFCs).To achieve this goal,constructing optimized structure of catalyst layers with efficient mass transportation channels plays a vital role.Herein,PEMFCs with order-structured cathodic electrodes were fabricated by depositing Pt nanoparticles by Ebeam onto vertically aligned carbon nanotubes(VACNTs)growth on Al foil via plasma-enhanced chemical vapor deposition.Results demonstrate that the proportion of hydrophilic Pt-deposited region along VACNTs and residual hydrophobic region of VANCTs without Pt strongly influences the cell performance,in particular at high current densities.When Pt nanoparticles deposit on the top depth of around 600 nm on VACNTs with a length of 4.6μm,the cell shows the highest performance,compared with others with various lengths of VACNTs.It delivers a maximum power output of 1.61 W cm^(-2)(H_(2)/O_(2),150 k Pa)and 0.79 W cm^(-2)(H_(2)/Air,150 k Pa)at Pt loading of 50μg cm^(-2),exceeding most of previously reported PEMFCs with Pt loading of<100μg cm^(-2).Even though the Pt loading is down to 30μg cm^(-2)(1.36 W cm^(-2)),the performance is also better than 100μg cm^(-2)(1.24 W cm^(-2))of commercial Pt/C,and presents better stability.This excellent performance is critical attributed to the ordered hydrophobic region providing sufficient mass passages to facilitate the fast water drainage at high current densities.This work gives a new understanding for oxygen reduction reaction occurred in VACNTs-based ordered electrodes,demonstrating the most possibility to achieve a substantial reduction in Pt loading<100μg cm^(-2) without sacrificing in performance.

High-loading Pt-alloy catalysts for boosted oxygen reduction reaction performance

To improve performance of membrane electrode assembly(MEA)at large current density region,efficient mass transfer at the cathode is desired,for which a feasible strategy is to lower catalyst layer thickness by constructing high loading Pt-alloy catalysts on carbon.But the high loading may induce unwanted par-ticle aggregation.In this work,H-PtNi/C with 33%(mass)Pt loading on carbon and monodisperse distri-bution of 3.55 nm PtNi nanoparticles,was prepared by a bimodal-pore route.In electrocatalytic oxygen reduction reaction(ORR),H-PtNi/C displays an activity inferior to the low Pt loading catalyst L-PtNi/C(13.3%(mass))in the half-cell.While in H_(2)-0_(2) MEA,H-PtNi/C delivers the peak power density of 1.51 W·cm^(-2) and the mass transfer limiting current density of 4.4 A·cm^(-2),being 21%and 16%higher than those of L-PtNi/C(1.25 W·cm^(-2),3.8 A·cm^(-2))respectively,which can be ascribed to enhanced mass trans-fer brought by the thinner catalyst layer in the former.In addition,the same method can be used to pre-pare PtFe alloy catalyst with a high-Pt loading of 36%(mass).This work may lead to a range of catalyst materials for the large current density applications,such as fuel cell vehicles.

Electrochemically Grown Ultrathin Platinum Nanosheet Electrodes with Ultralow Loadings for Energy-Saving and Industrial-Level Hydrogen Evolution

Nanostructured catalyst-integrated electrodes with remarkably reduced catalyst loadings,high catalyst utilization and facile fabrication are urgently needed to enable cost-effective,green hydrogen production via proton exchange membrane electrolyzer cells(PEMECs).Herein,benefitting from a thin seeding layer,bottom-up grown ultrathin Pt nanosheets(Pt-NSs)were first deposited on thin Ti substrates for PEMECs via a fast,template-and surfactant-free electrochemical growth process at room temperature,showing highly uniform Pt surface coverage with ultralow loadings and vertically well-aligned nanosheet morphologies.Combined with an anode-only Nafion 117 catalyst-coated membrane(CCM),the Pt-NS electrode with an ultralow loading of 0.015 mgPt cm−2 demonstrates superior cell performance to the commercial CCM(3.0 mgPt cm^(−2)),achieving 99.5%catalyst savings and more than 237-fold higher catalyst utilization.The remarkable performance with high catalyst utilization is mainly due to the vertically well-aligned ultrathin nanosheets with good surface coverage exposing abundant active sites for the electrochemical reaction.Overall,this study not only paves a new way for optimizing the catalyst uniformity and surface coverage with ultralow loadings but also provides new insights into nanostructured electrode design and facile fabrication for highly efficient and low-cost PEMECs and other energy storage/conversion devices.

柴油机SDPF催化剂涂覆策略对NO_(x)排放特性和压降影响的仿真研究

为了满足日益强化的排放法规指标要求,柴油发动机业界开发了选择性催化还原捕集技术(SDPF)。SDPF将SCR催化剂涂覆在壁流式颗粒捕集器(DPF)载体上,通过催化还原过程,可以同时减少柴油机发动机排气中的氮氧化物(NO_(x))和颗粒物(PM),也解决了SCR原理中发动机排气门导致的温度过低排放控制困难的问题,可以显著改善冷启动下的NO_(x)排放。本文建立了一个仿真模型,并基于发动机台架试验数据对模型进行了标定,研究了SDPF催化剂不同的涂覆策略——催化剂涂覆量和催化剂涂覆比例,对柴油机排放性能和压降特性的影响。仿真结果表明:SDPF的压降随着催化剂涂覆量和涂覆比例的增加而增加,但是过量的催化剂涂层导致的压降过高会使NO_(x)转化效率下降;当催化剂涂覆量达到70g/L时, NO_(x)的转化效率最高;发动机处于低负荷工况时,当催化剂涂覆比例高于60%左右时, NO_(x)转化效率更高。

低温加氢催化剂CT6-13在硫磺尾气处理系统的应用

中国石油四川石化有限责任公司硫磺回收装置采用加氢还原吸收工艺及专用加氢催化剂进行尾气处理。将低温加氢催化剂CT6-13与常规加氢催化剂CT6-5B从物性、装填方法及预硫化、技术性能等方面进行了对比。深入对比分析CT6-5B和CT6-13在尾气加氢反应器的应用情况,发现采用CT6-13催化剂,节能降耗效果明显,尾气排放满足总硫不大于50μL/L、SO_(2)排放浓度不大于100 mg/m^(3)的设计要求。配套高效脱硫剂CT8-26及烟气洗涤技术,可实现开工过程尾气达标排放及日常运行过程尾气SO_(2)排放浓度不大于5 mg/m^(3)的超低排放。在节能降耗的同时解决了开停工及异常工况下的绿色生产及制约硫磺回收装置尾气焚烧炉长周期运行瓶颈问题。

贵金属催化剂低温催化氧化一氧化碳研究进展

随着“双碳”政策的不断推行以及人们环保意识的不断提高,一氧化碳(CO)作为典型的大气污染物,已成为工业废气和汽车尾气排放的主要控制对象。贵金属型CO氧化催化剂具有优异的低温活性、抗中毒抗性能,是CO催化氧化处理的最为有效的手段之一。基于贵金属型CO氧化催化剂的研究现状,重点围绕Pt、Pd、Au、Ag、Rh贵金属催化剂的贵金属调控技术和载体可控技术进行综述,总结了贵金属型CO氧化催化剂的性能优化策略和发展方向,为开发高性能的CO氧化催化剂提供指导。

γ-Mo_(2)N/C催化剂的合成及其甲酸脱氢性能研究

甲酸(FA)因其H含量较高(4.4%)、易产H_(2)、可经小平台化合物合成等优势受到广泛关注,而γ-Mo_(2)N/C对FA沿H_(2)和CO_(2)路径分解具有非常高的选择性,产生CO极少,显示出较高的应用价值。基于此,本研究采用对苯二胺和钼酸铵水溶液经前驱体制备γ-Mo_(2)N/C催化剂,并对其FA分解性能进行了原位评价,采用热重分析(TG)、X射线衍射(XRD)、傅里叶变换红外光谱(FT-IR)、扫描电镜(SEM)、透射电镜(TEM)等表征手段对催化剂的结构和表面官能团进行了分析,利用DFT对FA在γ-Mo_(2)N (200)晶面的吸附构型进行了计算,在此基础上,对催化剂性能及FA在其表面的分解机理进行了研究。结果表明,γ-Mo_(2)N/C在较低温度下即可表现出极高的催化活性,提高γ-Mo_(2)N在C载体上的分散性能有效改善FA转化率。对苯二胺与钼酸铵的物质的量比为4∶1时,催化性能最佳,在160℃、100 h的FA分解实验中,催化剂性能稳定、H_(2)选择性高(N_(2)40 mL/min, CO<5.0×10^(-5))。而DFT计算表明,FA中O-H键的H原子与γ-Mo_(2)N/C (200)晶面上N原子结合的可能性更大,而C=O键的O原子更有可能与γ-Mo_(2)N/C (200)晶面上Mo原子结合。上述结果有助于明确FA在γ-Mo_(2)N/C作用下的分解机理,也显示出非贵金属催化剂γ-Mo_(2)N/C在FA分解制H_(2)方面潜在的应用前景。

Effect of catalyst diesel particulate filter aging and catalyst loadings on particulate emission characteristics from a diesel vehicle

In this study,the effect of new and used catalyzed diesel particulate filter(CDPF)with different catalyst loadings on the particulate emissions including the particle mass(PM),particle number(PN),particle size distribution(PSD)and geometric mean diameter(GMD)from a diesel vehicle were investigated based on a heavy chassis dynamometer.Results showed that more than 97.9%of the PN and 95.4%of the PM were reduced by the CDPF,and the reduction efficiency was enhanced by the catalyst loading.After using the CDPF,the PSD transformed from bimodal to trimodal with the peak shifting towards smaller particle size,more nucleation mode particles were reduced compared with accumulation mode ones,but the reduction effect on the accumulation mode particles was more significantly influenced by the catalyst loading.Notably,the CDPF increased the accumulation mode particles proportion,producing a larger GMD.For the used CDPF,its reduction effect on the particulate emissions enhanced,especially for the PM in accumulation mode.The PSD returned to bimodal,but the peak at accumulation mode began to be higher than that at nucleation mode,illustrating that more nucleation mode particles was removed.The aging of the CDPF resulted in greater effect on the PN-based PSD than that of PM-based PSD,but the effect of catalyst loading on the PN and PM emission factors was weakened.The used CDPF further increased the GMD,and the effect of catalyst loading on the GMD was strengthened,a higher catalyst loading led to a reduction in the GMD.

分步负载金属法制备铁钴双金属位点高效氧还原电催化剂

过渡金属和氮掺杂的碳(M-N-C)由于优异的电催化活性以及较低的生产成本,成为铂基催化剂的替代。然而,目前的M-N-C催化剂通常涉及金属盐、含氮物质和碳载体的结合,在经过热处理和酸洗过程后得到的催化剂在活性位点密度和传质能力上性能不足。采用分步负载金属法制备了Fe、Co双金属掺杂的M-N-C催化剂。利用Zn2+和Co2+的竞争效应,成功合成了小尺寸且均匀的Zn-Co-ZIFs双金属沸石咪唑骨架。随后,在不形成金属团簇的前提下将最大量的Fe原子嵌入C-Zn-Co-ZIFs-H+前体结构中,使其在热解后能产生大量的FeCo—Nx活性位点。这种改进显著增加了FeCo-N-C-2催化剂中Fe活性位点的含量(1.9%,质量分数),并深度优化了其微孔和介孔结构(860 m^(2)·g^(-1))。该催化剂在0.1 mol·L^(-1) HClO_(4)和0.1 mol·L^(-1) KOH溶液中,氧还原反应(ORR)活性展现出了0.806 V和0.921 V的半波电位,并分别在50000、45000 s恒定电位测试后保持了91.21%和95.32%的活性。将其组装于质子交换膜燃料电池(PEMFCs)和碱性锌-空气液流电池(ZAFBs)中,峰值功率密度分别达到了746、164 mW·cm^(-2),显示出优越的性能。

Fe@CeO_(2)/CN双空腔核壳磁性载金椭球催化剂及其催化还原对硝基苯酚和染料污染物

载金催化剂可在温和条件下还原性降解环境中某些有毒有害污染物,并转化为低毒性、高附加值的物质,从而促进水体污染物化学资源转化和综合利用.本文设计制备Fe@CeO_(2)/CN双空腔核壳磁性载金椭球催化剂,用于还原降解水体中对硝基苯酚和染料污染物.该催化剂先制备Fe_(2)O_(3)@CeO_(2)梭型微粒内核,采用乙二胺介导的Stober扩展法在其表面合成SiO_(2)@RF复合物,经过碳化-水热蚀刻得到具有介孔碳氮壳层的Fe_(2)O_(3)@CeO_(2)/CN椭球;采用[Au(en)_(2)]^(3+)为金前驱体的沉积沉淀-还原气氛热处理法在上述椭球中构筑较好分散度超细纳米Au颗粒,同时Fe_(2)O_(3)转化为小体积Fe颗粒并形成内空腔,得到Fe@CeO_(2)-Au/CN双空腔核壳磁性椭球催化剂.该催化剂独特的结构特征和复合组分协同增强性效应使其在还原降解对硝基苯酚和染料污染物中均表现优越的催化反应性能和循环使用性能,重复多次使用后仍保存良好的磁分离性和较好的结构完整性.

连续重整装置换剂后催化剂循环量控制优化

针对某连续重整装置更换催化剂(催化剂堆密度由670 kg/m^(3)更换为561 kg/m^(3))后保持催化剂循环输送稳定的问题,提出了催化剂循环优化方法。闭锁料斗仍采用差压模式,仅调整设置闭锁料斗闭锁区上下料位限值(由48.2%~96%更改为41.6%~97%),使闭锁区催化剂单次循环量相同;同时,将快慢装/卸料报警值由12~30 s/12~30 s调整为14~35 s/14~35 s,使之与闭锁料斗上下平衡阀开关时间匹配,保证差压模式下催化剂循环输送稳定。此方法较大程度简化了其他控制参数的调整,可以实现换剂后催化剂循环高效平稳运行。

钯铱催化剂的制备及其在质子交换膜制氢膜电极中的应用

质子交换膜电解水制氢是制取绿氢的主要技术路线之一,也是电解水制氢行业的研究热点。膜电极是质子交换膜电解水制氢技术的核心零部件,目前其核心开发工作主要是通过调控阳极铱基催化剂的内在结构,增加新的活性位点和增强其稳定性,最终实现在膜电极上降低铱使用载量的目的。本文提出一种新型析氧催化剂的制备方案:在传统铱基催化剂中引入钯元素,开发出钯铱合金催化剂,将钯作为新增的活性点,并充分利用钯金属与铱金属的合金效应,激发铱基催化剂的隐藏活性,其析氧过电位仅为344 mV,塔菲尔斜率为75.71 mV/dec,活性较传统铱基催化剂大幅提升。将其应用于膜电极上,当铱载量为0.33 mg/cm^(2)时,在1000 mA/cm^(2)的工作电流密度下,电解水电压仅为1.867 V,且已稳定运行350 h。

基于分子筛的低负载金属催化剂在绿色化学中的应用

为探究有效的绿色催化剂,制备了基于分子筛的低负载金属催化剂,并在催化氢硅烷水解实验和循环实验中验证了其效用。实验结果显示,在600℃条件下制备的基于分子筛的低负载钯金属催化剂最高具有93%的产出率,再生后循环使用仍具有高至75%的产出率,是高产出的氢硅烷水解催化剂,具有良好的催化活性且可循环使用,符合绿色化学的概念。

3.1 Mt/a国产连续重整装置运行分析

某公司3.1 Mt/a连续重整装置采用具有自主知识产权的国产超低压连续重整(SLCR)技术,选用连续重整催化剂PS-Ⅵ,是目前国产化规模最大的连续重整装置。装置大型化后热态考核阶段,反应-再生系统各设备、管线支吊架位移正常,与设计数据吻合。装置投料开工后,反应-再生系统热位移趋势与热态考核结果一致。装置性能考核结果表明:在原料芳烃潜含量比设计值低7.49百分点的情况下,装置C_(5)^(+)液体收率为88.15%,纯氢收率为3.80%,脱戊烷油芳烃的质量分数为82.84%,芳烃转化率为172%。装置运行半年后,催化剂粉尘量稳定在8~12 kg/d,各项经济指标参数良好,PS-Ⅵ催化剂表现出良好的反应活性、选择性及较低的磨损率。