碳化活化一体化纳米碳酸钙生产新工艺

碳化活化一体化装置具有碳化和活化温度可调、二氧化碳浓度可控、二氧化碳分布均匀、碳化无死角、搅拌速度可调、产品粒径大小和晶体形状可控等特点。该装置明显简化了纳米碳酸钙的生产流程,减少了设备数量,省略了浆液的静置、陈化、冷却、增浓等环节,提高了工艺的连续性,有利于节能降耗和提高产品质量的稳定性。在碳化起始浆液浓度、起始温度、制冷机功率、碳化气流量或压力等因素都相同的前提下,探讨了碳化气分别采用体积分数为38%、95%以及从95%渐降到20%模式时,碳化过程中氢氧化钙质量分数与碳化时间和碳化温度的关系,其中碳化气体积分数以渐降方式最为理想。

碳化活化温度对生物质基多孔碳/硫复合正极材料电化学性能的影响

以胖大海作为生物质碳源、KOH为活化剂,采用一步碳化活化法制备了生物质基多孔碳,将多孔碳作为三维导电骨架和硫宿主材料,与硫熔融复合后用作锂硫电池正极材料。采用扫描电镜、透射电镜、X射线衍射、拉曼光谱、热重分析、电化学工作站和电池测试仪等对碳/硫复合正极材料的综合性能和电化学性能进行分析测试,研究了不同碳化活化温度对多孔碳微观结构和碳/硫复合正极材料电化学性能的影响。结果表明:随着碳化活化温度的升高(700-900℃)多孔碳石墨化程度和比表面积、孔容均先增大后减小,当优选碳化活化温度为800r时,所制备的多孔碳的结构为以微孔为主的微介孔结构,其比表面积和孔容最大,碳/硫复合正极材料表现出较高的比容量、良好的倍率性能和循环稳定性,主要是由于经过800℃碳化活化后的多孔碳不仅具有良好的导电性,而且其高的比表面积、孔容为活性硫提供了充足的反应位点,丰富的微介孔结构能够物理限制可溶性多硫化物的扩散,从而有效抑制了“穿梭效应”。

活性碳纤维的碳化—活化机理

通过用ＮａＯＨ预处理剑麻纤维，再浸泡ＺｎＣｌ＿２溶液，然后在Ｎ＿２保护下热处理，制备出较高纤维得率和Ａｇ￣＋还原吸附能力的活性碳纤维（ＺＣＳＡＣＦ）。借助于ＩＲ，ＴＧ，ＷＡＸＤ，元素分析和比表面积测定，研究了纤维的碳化—活化机理。实验结果表明：纤维在低温区脱水的同时形成醛、酮基团和Ｃ＝Ｃ结构。当温度升到２５０℃以上时，纤维表面开始形成大量的微孔。提高ＺｎＣｌ＿２溶液的浸泡浓度可显著增加ＺＣＳＡＣＦ的表面积。当温度升至５５０℃时，纤维开始芳构化。

反应性硬模板制备多孔氮掺杂碳的电化学性能

以葡萄糖(G)、尿素(U)、碱式碳酸盐和碳酸钾(PC)分别为碳前驱体、氮掺杂剂、反应性硬模板和活化剂,采用模板碳化-化学活化法合成了层级多孔氮掺杂碳材料。研究了各前驱体质量比、硬模板类型对其结构进而对其用作超级电容器电极性能的影响。结果表明:在800℃裂解温度下,G、U、碱式碳酸锌(BZC)和PC的质量比为2∶1∶2∶2时,制备的多孔氮掺杂碳(G/U-BZC-PC)呈现出珊瑚状、多级孔(微-介),具有大的比表面积(3000 m^(2)/g)、较高的石墨化程度以及低的电荷转移电阻;在1 A/g电流密度下,其扣式电池(6 mol/L KOH)的比电容为301.9 F/g,且具有较好的倍率性能,增大至10 A/g时,其电容保持率为89.4%;另外,在10000次充放电循环后,其电容保持率为98.1%。

碳化气浓度渐降模式对纳米碳酸钙碳化过程的影响研究

设计了碳化活化一体化装置,具有碳化和活化温度可调、CO_2浓度可控、CO_2分布均匀、碳化无死角、搅拌速度可调、晶体形状可控、可简化生产流程,减少设备数量等特点,可避免浆液的静置、陈化、冷却、增浓等工艺环节,提高了工艺的连续性,有利于节能降耗和提高产品质量稳定性。在碳化起始浆液质量分数、起始温度、制冷机功率、碳化气流量或压力等因素都相同的前提下,当碳化气体积分数分别采用35%、99%,以及从99%渐降到20%等3种模式时,探讨了碳化过程中氢氧化钙浆液浓度变化规律与碳化气体积分数、碳化时间和碳化温度的关系,其中碳化气浓度渐降模式最为理想。

再生混凝土粉和再生砖粉活化技术研究进展

介绍了再生混凝土粉(RCP)和再生砖粉(RBP)的基本特性,分析了机械活化、热活化、碳化活化、碱激发等活化方式对RCP和RBP活性的影响,并探讨了相关活化机理,总结了各活化方式的优点与不足,可为再生微粉活化方式的优选提供参考。

hcp-Co基费托合成催化剂的研究进展

由于Co基费托(F-T)合成催化剂具有优异的催化性能,一直受到学术界和工业界的广泛关注。近年来人们发现Co基催化剂对F-T合成反应的催化活性与催化剂晶体结构有紧密关系,六方密堆积(hcp)相Co基催化剂的催化活性大于面心立方(fcc)相Co基催化剂的催化活性。综述了hcp-Co基F-T合成催化剂的最新研究进展,介绍了hcp-Co的晶体结构、B5活性位点的分布、hcp-Co不同晶面对C—C链增长机理的理论计算结果及制备hcp-Co基催化剂的实验方法,展望了Co基催化剂的未来发展方向。

石油焦制备的活性碳质吸附材料性能及机理研究

利用石油焦为前驱体,加入化学活化剂及辅助助剂,以酚醛树脂为黏合剂挤出成型,通过优化碳化、活化工艺参数制备了活性碳质吸附材料。当活化温度为900℃,活化时间为120 min时,制品的转鼓强度为95%,比表面积为1208 m^(2)/g。通过研究活性吸附材料的孔隙结构、微观形貌并利用红外光谱分析探讨了活化机理。

氨水改性对污泥基活性焦脱硫性能的影响

以废弃污泥和杨树皮为原料通过碳化活化可制得孔隙结构和比表面积等物理性质相对较好的污泥基活性焦,但其化学性质较差。实验采用不同浓度氨水对活性焦改性处理以改善活性焦的化学性质。对活性焦比表面积、孔隙结构、表面官能团进行了分析,探讨了不同浓度氨水改性对活性焦物理化学性质的影响。并以SO_(2)为目标物,考察氨水改性后活性焦的脱硫性能。实验结果表明,氨水改性后,活性焦表面引入了含氮官能团,大幅度提高了吸附能力。随着氨水浓度提高,活性焦的比表面积和孔隙结构变差,但脱硫能力提高。

利用秸秆原材料制备活性炭吸附材料的工艺研究与应用

本文研究探讨了农作物秸秆原材料制备活性炭吸附材料的反应条件,并在生产设备碳化活化炉中进行了中试生产,探讨了生产工艺条件对活性炭吸附材料质量指标的影响。当碳化温度为450-600℃,碳化时间为90min,活化温度为900℃,活化时间为30min,蒸汽通入量为0.4kg/h,得到的活性炭材料碘值为650mg/L,亚甲蓝值120mg/g。将该秸秆活性炭材料应用到企业污水吸附过滤罐中,可以显著降低废水的COD、色度、气味、有机物类污染指标。故对秸秆原材料通过预干燥、碳化、活化、冷却、筛分来制备活性炭吸附材料,为废弃农作物的资源化再利用起到了积极作用,具有较强的应用前景。

SnO_2 nano-sheet as an efficient catalyst for CO oxidation

Polycrystalline SnO2 fine powder consisting of nano-particles （SnO2-NP）, SnO2 nano-sheets （SnO2-NS）, and SnO2 containing both nano-rods and nano-particles （SnO2-NR＋NP） were prepared and used for CO oxidation. SnO2-NS possesses a mesoporous structure and has a higher surface area, larger pore volume, and more active species than SnO2-NP, and shows improved activity. In contrast, although SnO2-NR＋NP has only a slightly higher surface area and pore volume, and slightly more active surface oxygen species than SnO2-NP, it has more exposed active （110） facets, which is the reason for its improved oxidation activity. Water vapor has only a reversible and weak influence on SnO2-NS, therefore it is a potential catalyst for emission control processes.

Synthesis of bionic-macro/microporous MgO-modified TiO_2 for enhanced CO_2 photoreduction into hydrocarbon fuels

The stems of water convolvulus were employed as biotemplates for the replication of their optimized 3D hierarchical architecture to synthesize porous MgO-modified TiO2 . The photocatalytic reduction of CO2 with H2O vapor into hydrocarbon fuel was studied with these MgO-TiO2 nanostructures as the photocatalysts with the benefits of improved CO2 adsorption and activation through incorporated MgO. Various factors involving CO2 adsorption capacity, migration of charge carriers to the surface, and the number of activity sites, which depend on the amount of added MgO, determine the photocatalytic conversion efficiency.

Synergistic degradation of phenols by bimetallic CuO-Co_3O_4@γ-Al_2O_3 catalyst in H_2O_2/HCO_3^- system

The development of new catalytic techniques for wastewater treatment has long attracted much attention from industrial and academic communities.However,because of catalyst leaching during degradation,catalysts can be short lived,and therefore expensive,and unsuitable for use in wastewater treatment.In this work,we developed a bimetallic CuO-Co3O4@γ-Al2O3 catalyst for phenol degradation with bicarbonate-activated H2O2.The weakly basic environment provided by the bicarbonate buffer greatly suppresses leaching of active Cu and Co metal ions from the catalyst.X-ray diffraction and X-ray photoelectron spectroscopy results showed interactions between Cu and Co ions in the CuO-Co3O4@γ-Al2O3 catalyst,and these improve the catalytic activity in phenol degradation.Mechanistic studies using different radical scavengers showed that superoxide and hydroxyl radicals both played significant roles in phenol degradation,whereas singlet oxygen was less important.

Effects of Co_3O_4 nanocatalyst morphology on CO oxidation:Synthesis process map and catalytic activity

This study focuses on drawing a hydrothermal synthesis process map for Co3O4 nanoparticles with various morphologies and investigating the effects of Co3O4 nanocatalyst morphology on CO oxidation.A series of cobalt-hydroxide-carbonate nanoparticles with various morphologies（i.e.,nanorods,nanosheets,and nanocubes） were successfully synthesized,and Co3O4 nanoparticles were obtained by thermal decomposition of the cobalt-hydroxide-carbonate precursors.The results suggest that the cobalt source is a key factor for controlling the morphology of cobalt-hydroxide-carbonate at relatively low hydrothermal temperatures（≤ 140℃）.Nanorods can be synthesized in CoCl2 solution,while Co（NO3）2 solution promotes the formation of nanosheets.Further increasing the synthesis temperature（higher than 140 ℃） results in the formation of nanocubes in either Co（NO3）2 or CoCl2 solution.The reaction time only affects the size of the obtained nanoparticles.The presence of CTAB could improve the uniformity and dispersion of particles.Co3O4 nanosheets showed much higher catalytic activity for CO oxidation than nanorods and nanocubes because it has more abundant Co^（3＋） on the surface,much higher reducibility,and better oxygen desorption capacity.

Cobalt-catalyzed redox-neutral synthesis of isoquinolines: C–H activation assisted by an oxidizing N–S bond

A redox‐neutral avenue to access isoquinolines has been realized by a Co（III）‐catalyzed C–H activa‐tion process. Starting from readily available N‐sulfinyl imine substrates and alkynes, the reaction occurred via N–S cleavage with broad substrate scope and functional group compatibility in the presence of cost‐effective cobalt catalysts.

Ni-catalyzed direct carboxylation of unactivated alkyl electrophiles with carbon dioxide

Carbon dioxide is a cheap, abundant and renewable C1 building block. Over the last two decades, considerable re- search efforts have been devoted to developing new reactions for the efficient incorporation of carbon dioxide into a broad range of compounds for the production of value-added materi- als [1]. Notably, these efforts have culminated in the develop- ment of several transition-metal-catalyzed methods capable of providing access to numerous synthetically important carbox- ylic acids and derivatives using carbon dioxide as a carboxyla- tive reagent [2].

Bicarbonate activation of hydrogen peroxide: A new emerging technology for wastewater treatment

The serious limitations of available technologies for decontamination of wastewater have compelled researchers to search for alternative solutions. Catalytic treatment with hydrogen peroxide, which appears to be one of the most efficient treatment systems, is able to degrade various organics with the help of powerful ·OH radicals. This review focuses on recent progress in the use of bicarbonate activated hydrogen peroxide for wastewater treatment. The introduction of bicarbonate to pollutant treatment has led to appreciable improvements, not only in process efficiency, but also in process stability. This review describes in detail the applications of this process in homogeneous and heterogeneous systems. The enhanced degradation, limited or lack of leaching during heterogeneous degradation, and prolonged catalysts stability during degradation are salient features of this system. This review provides readers with new knowledge regarding bicarbonate, including the fact that it does not always harm pollutant degradation, and can significantly benefit degradation under some conditions.

Regeneration of catalysts deactivated by coke deposition:A review

In industrial catalytic processes,coke deposition can cause catalyst deactivation by covering acid sites and/or blocking pores.The regeneration of deactivated catalysts,thereby removing the coke and simultaneously restoring the catalytic activity,is highly desired.Despite various chemical reactions and methods are available to remove coke,developing reliable,efficient,and economic regeneration methods for catalytic processes still remains a challenge in industrial practice.In this paper,the current progress of regeneration methods such as oxidation(air,ozone and oxynitride),gasification(carbon dioxide and water steam),and hydrogenation(hydrogen)is reviewed,which hopefully can shed some light on the design and optimization of catalysts and the related processes.

Insight into MgO promoter with low concentration for the carbon-deposition resistance of Ni-based catalysts in the CO_2 reforming of CH_4

The CO2reforming of CH4is studied over MgO‐promoted Ni catalysts,which were supported on alumina prepared from hydrotalcite.This presents an improved stability compared with non‐promoted catalysts.The introduction of the MgO promoter was achieved through the‘‘memory effect’’of the Ni‐Al hydrotalcite structure,and ICP‐MS confirmed that only0.42wt.%of Mg2+ions were added into the Ni‐Mg/Al catalyst.Although no differences in the Ni particle size and basicity strength were observed,the Ni‐Mg/Al catalyst showed a higher catalytic stability than the Ni/Al catalyst.A series of surface reaction experiments were used and showed that the addition of a MgO promoter with low concentration can promote CO2dissociation to form active surface oxygen arising from the formation of the Ni‐MgO interface sites.Therefore,the carbon‐resistance promotion by nature was suggested to contribute to an oxidative environment around Ni particles,which would increase the conversion of carbon residues from CH4cracking to yield CO on the Ni metal surface.?2018,Dalian Institute of Chemical Physics,Chinese Academy of Sciences.Published by Elsevier B.V.All rights reserved.

Promotion effects of nickel-doped Al2O3-nanosheet-supported Au catalysts for CO oxidation

Supported gold catalysts show high activity toward CO oxidation, and the nature of the support significantly affects the catalytic activity. Herein, serial Ni doping of thin porous Al2 O3 nanosheets was performed via a precipitation-hydrothermal method by varying the amount of Ni during the precipitation step. The prepared nanosheets were subsequently used as supports for the deposition of Au nanoparticles(NPs). The obtained Au/Nix Al catalysts were studied in the context of CO oxidation to determine the effect of Ni doping on the supports. Enhanced catalytic performances were obtained for the Au/Nix Al catalysts compared with those of the Au supported on bare Al2 O3. The Ni content and pretreatment atmosphere were both shown to influence the catalytic activity. Pretreatment under a reducing atmosphere was beneficial for improving catalytic activity. The highest activity was observed for the catalysts with a Ni/Al molar ratio of 0.05, achieving complete CO conversion at 20 °C with a gold loading of 1 wt%. The in-situ FTIR results showed that the introduction of Ni strengthened CO adsorption on the Au NPs. The H2-TPR and O2-TPD results indicated that the introduction of Ni produced new oxygen vacancies and allowed the oxygen molecules to be adsorbed and activated more easily. The improved catalytic performance after doping Ni was attributed to the smaller size of the Au NPs and more active oxygen species.