Synthesis of Carbon Nanotubes using Cu-Cr-O as Catalyst by Chemical Vapor Deposition

A novel powder catalyst Cu-Cr-O applied to the synthesis of carbon nanotubes （CNTs） was developed, which was prepared via ammonia precipitation method. Techniques of thermo-gravimetric/ differential scanning calorimeter （TG-DSC）, X-ray diffraction （XRD） as well as scanning electron microscopy （SEM） and transmission electron microscopy （TEM） have been employed to characterize the thermal decomposition procedure, crystal phase and micro structural morphologies of the as-synthesized materials, respectively. The results show that carbon nanotubes are successfully synthesized using Cu-Cr-O as catalyst when the precursors are calcined at 400, 500, 600, and 700 ℃. The results indicate that the calcination of the Cu-Cr-O catalyst at 600 ℃ is an effective method to get MWCNT with few nano-tube defects or amorphous carbons.

Study on Co-Effect of K₂SO₄Deposition and Low Concentration SO₂on Performances of V₂O₅/AC Catalysts for Low Temperature SCR

Simulated compounds were prepared by loading K2SO4 onto V2O5/AC catalysts. Study the effect of K2SO4 on V1/AC catalysts in the presence of low concentration SO2. Transient response techniques, TPD was carried out. The results indicated that the DeNO activity of V1/AC catalysts was decreased seriously in the early period of operation, but the deactivation was gradually diminished with SO2 adsorption and then, it was completely eliminated. For the sulphated catalysts (saturated catalysts by sulphate), their SCR activity were free from existence of gaseous SO2. the loss of activity about 10% caused by K2SO4 was found on them. The deactivation of K2SO4 deposited catalysts was due to the decrease of adsorbed and activated NH3, or some acid sites.

Catalyst Enhanced Chemical Vapor Depositionof Nickel on Polymer Surface

Catalyst enhanced chemical vapor deposition of nickel film on high Tg polymers such as teflon(PTFE), polyimide(PI), and polysulfone(PS) was investigated by hot wall and cold wall CVD, in which Ni(dmg)_2, Ni(acac)_2, Ni(hfac)_2, Ni(TMHD)_2, and Ni(cp)_2 are used as precursors, and palladium complexes are used as catalysts. The films obtained were shiny with silvery color. The Ni was metallic and the purity of Ni was about 92%-95% from XPS analysis. SEM micrographs show that the film had good morphology. The conductivity of the film was about 0.5-4 W·cm^(-1). Ni films had good adhesion with polyimide and polysulfone.

Formation and Characterization of Pd,Pt and Pd-Pt Alloy Films on Polyimide by Catalyst-Enhanced Chemical Vapor Deposition

Platinum, palladium and their alloy films on polyimide were formed by catalyst-enhanced chemical vapor deposition （CVD） in the carrier gas （N2, O2） at 220-300℃ under reduced pressure and normal pressure. The deposition of palladium complexes [ Pd（（η3-allyl）（hfac） and Pd（hfac）2 ] gives pure palladium film, while the deposition of platinum needs the enhancement of palladium complex by mixing precursor platinum complex Pt（COD）Me2 and palladium complex in the same chamber. The co-deposition of Pd and Pt metals was used for the deposition of alloy films. During the CVD of palladium-platinum alloy, the Pd/Pt atomic ratios vary under different co-deposition conditions. These metal films were characterized by XPS and SEM, and show a good adhesive property.

Synthesis of multi-walled carbon nanotubes using CoMnMgO catalysts through catalytic chemical vapor deposition

The Co Mg O and Co Mn Mg O catalysts are prepared by a co-precipitation method and used as the catalysts for the synthesis of carbon nanotubes（CNTs） through the catalytic chemical vapor deposition（CCVD）. The effects of Mn addition on the carbon yield and structure are investigated. The catalysts are characterized by temperature programmed reduction（TPR） and X-ray diffraction（XRD） techniques, and the synthesized carbon materials are characterized by transmission electron microscopy（TEM） and thermo gravimetric analysis（TG）. TEM measurement indicates that the catalyst Co Mg O enclosed completely in the produced graphite layer results in the deactivation of the catalyst. TG results suggest that the Co Mn Mg O catalyst has a higher selectivity for CNTs than Co Mg O. Meanwhile, different diameters of CNTs are synthesized by Co Mn Mg O catalysts with various amounts of Co content, and the results show that the addition of Mn avoids forming the enclosed catalyst, prevents the formation of amorphous carbon, subsequently promotes the growth of CNTs, and the catalyst with decreased Co content is favorable for the synthesis of CNTs with a narrow diameter distribution.The Co Mn Mg O catalyst with 40% Co content has superior catalytic activity for the growth of carbon nanotubes.

碳酸氧铋基光催化材料的改性研究进展

碳酸氧铋是一种典型的铋基半导体光催化材料,其具有[BiO]_(2)^(+2)和CO_(3)^(2-)层交替组成的独特层状晶体结构。通过改性可促进(BiO)_(2)CO_(3)的可见光响应能力以及光生电荷分离效率,从而提升其光催化性能。本文主要从贵金属沉积、元素掺杂、异质结构建以及氧空位缺陷等方面综述了碳酸氧铋基光催化材料的改性研究进展。同时指出碳酸氧铋的改性研究需致力于进一步简化制备工艺,并使得改性工艺控制更加精准,以使其在有机污染物降解、光解水制氢等方面得到更好的应用前景。

原子层沉积法制备限域型Pt基催化剂及其苯酚催化性能

选择合适的载体负载贵金属Pt纳米粒子,对于制备高效的苯酚加氢催化剂具有重要意义。使用原子层沉积技术,以碳纳米纤维作为模板,在其表面依次沉积Pt纳米粒子,厚的氧化钛壳层,通过高温烧结除去模板,得到限域在氧化钛纳米管内壁的Pt纳米粒子。在500℃烧结温度下Pt纳米粒子的粒径在2.0~3.2 nm之间,平均粒径为2.6 nm,尺寸高度一致,均匀地分散并且嵌入到氧化钛纳米管的中空管道内壁。与常规负载在氧化钛纳米管外壁的Pt纳米粒子相比,该限域催化剂的催化转化率更高,在500℃烧结温度下转化频率(TOF)值为482.1 h^(−1),表现出更好的催化活性,而且由于氧化钛纳米管的保护作用,可有效防止Pt纳米粒子在反应过程中的聚集和脱落,在反应后Pt的质量分数仅降低了4.52%,其形貌也没有发生明显改变,从而表现出优异的催化稳定性。

原子层沉积技术调控分子筛基催化剂研究进展

分子筛基催化剂在多相催化研究领域具有重要的应用,但调控活性中心粒子的结构及其在分子筛上的空间位置仍比较困难,是科研界和工业界共同面临的巨大挑战。原子层沉积(ALD)是一种先进的薄膜沉积技术,利用其自限制生长优势,可在原子级别实现对金属粒子生长过程的精准调控。本工作综述了ALD技术在制备分子筛基催化剂方面的应用,主要包括利用ALD技术控制活性位点在分子筛上的生长落位、修饰分子筛骨架结构以及选择性沉积膜调变分子筛表面结构。利用ALD技术设计和调控活性组分结构促进了分子筛基催化剂的发展,但由于分子筛孔道结构复杂且存在缺陷位,因此,ALD技术在分子筛基催化剂的设计调控及大规模应用方面仍具有挑战性,也是今后研究工作的重点。

燃速催化剂对小喉径长工作时间燃气发生器喷管沉积的影响

小喉径长时间工作燃气发生器易在喷管产生沉积。针对低燃温燃气发生剂配方中的燃速催化剂种类、含量对喷管沉积的影响,采用配方理论计算、药柱内弹道性能试验、喷管沉积物组成分析以及喷管温度场仿真模拟等手段进行了机理研究。结果表明:低燃温燃气发生剂中的燃速催化剂种类对喷管沉积存在较大影响,铁系燃速催化剂比含锌催化剂更易沉积;燃速催化剂含量越高,越容易出现沉积;喷管沉积主要成分为碳、铁元素,在燃气中的组成为FeCl_(2),其沉积机理是,在低燃温燃气发生器喷管的温度场下FeCl_(2)存在固液转化过程,其含量超过0.13%时,易在喷管处沉积。据此提出了降低含铁燃速催化剂的含量或采用无铁燃速催化剂的改善措施。

Preparation of Au/CeO_2 catalyst and its catalytic performance for HCHO oxidation

Aqueous precipitation and deposition-precipitation method were used to prepare CeO2 supports and Au/CeO2 catalysts, respectively. The effect of preparation condition of support on the catalyst activity was investigated. The catalytic combustion of HCHO was considered as the probe reaction for comparing the catalyst activity. The BET, X-ray diffraction, X-ray photoelectron spectroscopy （XPS）, and reduction （TPR） were carried out to analyze the influence factor on the catalysts activity. The results showed that the addition of dispersant and use of microwave in the support preparation procedure could be beneficial for enhancing the interaction of supports and gold species and thus improved the catalytic activity. The total conversion temperature for HCHO was 146 ℃ over AC400. With the modification during supports preparation process, the catalytic activity increased with total conversion temperature decreasing to 98 ℃. The results of XPS indicated that Au^0 and Au^＋1 species coexisted in these catalysts and the activity of catalyst correlated with Au^＋1/Au^0 ratio. Temperature-programmed reduction results demonstrated that the reduction peak appeared between 100-170 ℃ with the inducing of gold. The dependence of activity on the reduction peak temperature implied that ionic gold was catalytic activity component for HCHO oxidation.

Effects of CO_2 content on the activity and stability of nickel catalyst supported on mesoporous nanocrystalline zirconia

The effects of carbon dioxide content on the catalytic performance and coke formation of nickel catalyst supported on mesoporous nanocrystalline zirconia with high surface area and pure tetragonal crystalline phase were investigated in methane reforming with carbon dioxide. The samples were characterized by XRD, BET, TPR, TPO, TPH, TEM, and SEM techniques. The catalyst prepared showed high surface area and a mesoporous structure with a narrow pore size distribution. The obtained results revealed that the increase in CO2 content increased the methane conversion and stability of the catalyst and significantly reduced the coke deposition. The TPH analysis showed that several species of carbon with different reactivities toward hydrogenation were deposited on the spent catalysts employed under different CO2 contents.

Growth of carbon nanotubes on the novel FeCo-Al_2O_3 catalyst prepared by ultrasonic coprecipitation

FeCo-Al2O3 catalyst was prepared by an ultrasonic coprecipitation （UC） method for the growth of carbon nanotubes （CNTs） from catalytic decomposition of methane.Its catalytic performance was compared with that of the FeCo-Al2O3 catalyst counterparts prepared by stepwise impregnation （I） and conventional coprecipitation （C） methods,respectively.The structure and properties of the catalysts and the CNTs as produced thereon were investigated by means of XRD,XPS,TEM and N2 adsorption techniques.It was found that the catalyst prepared by the ultrasonic coprecipitation method was more active,and the yield and purity of the synthesized CNTs were promoted evidently.The XPS results revealed that there were more active components on the surface of the catalyst prepared by the ultrasonic coprecipitation method.On the other hand,N2 adsorption demonstrated that the catalyst prepared by the ultrasonic coprecipitation method conferred larger specific surface area,which was beneficial to dispersion of active components.TEM images further confirmed its higher dispersion.These factors could be responsible for its higher activity for the growth of CNTs from catalytic decomposition of methane.

生物质热解催化剂积炭问题的研究进展

生物质催化热解获得生物油等高质产品是最有前途替代传统化石能源的方法之一,但在热解过程中存在着严重的催化剂失活问题,其中积炭是导致催化剂失活的最主要因素。本文对近年来生物质催化热解领域的催化剂积炭问题进行综述,重点介绍催化剂积炭失活原因及表征方法、积炭的影响因素分析(催化剂结构、催化剂酸性与反应温度)、抑制催化剂积炭的方法(催化剂改性、高压反应条件等)以及积炭催化剂再生方法(氧化灼烧再生、臭氧低温再生、非热等离子体再生等),并介绍了近年来新兴的微波催化热解技术对催化剂积炭的抑制和消除作用,然后针对该领域目前所面临的困难和发展方向进行展望,以期为生物质催化热解过程中催化剂积炭问题研究提供理论基础。

Controlling the Diameter of Single-Walled Carbon Nanotubes by Improving the Dispersion of the Uniform Catalyst Nanoparticles on Substrate

To have uniform nanoparticles individually dispersed on substrate before single-walled carbon nanotubes(SWNTs)growth at high temperature is the key for controlling the diameter of the SWNTs.In this letter,a facile approach to control the diameter and distribution of the SWNTs by improving the dispersion of the uniform Fe/Mo nanoparticles on silicon wafers with silica layer chemically modified by 1,1,1,3,3,3-hexamethyldisilazane under different conditions is reported.It is found that the dispersion of the catalyst nanoparticles on Si wafer surface can be improved greatly from hydrophilic to hydrophobic,and the diameter and distribution of the SWNTs depend strongly on the dispersion of the catalyst on the substrate surface.Well dispersion of the catalyst results in relatively smaller diameter and narrower distribution of the SWNTs due to the decrease of aggregation and enhancement of dispersion of the catalyst nanoparticles before growth.It is also found that the diameter of the superlong aligned SWNTs is smaller with more narrow distribution than that of random nanotubes.

Study on Diameter Controlled Growth of Carbon Nanotubes by LaAl_(1-x)Fe_xO_3 Catalysts

A series of LaAl 1-xFe xO 3 catalysts prepared with lanthanum nitrate, aluminium nitrate and iron nitrate was investigated in catalytical syntheses of carbon nanotubes with high yields and purity. The properties of carbon nanotubes prepared by the method of CVD(chemical vapor deposition) with n-hexane as the carbon resource were studied and it was shown that the diameter of carbon nanotubes can be controlled by the molar ratio of iron to aluminum in the catalysts and that the diameter of carbon nanotubes changes a little with the decrease of the iron content in the catalysts. From the TEM pictures of carbon nanotubes, it can be found that the LaAl 1-xFe xO 3 catalysts have a significant influence on the wall thickness of the carbon nanotubes, whereas they have little influence on the inner diameter of the carbon nanotubes.

Effects of Vanadium Oxidation Number on Light Olefins Selectivity of FCC Catalyst

Effects of vanadium on light olefins selectivity of FCC catalysts were investigated with vanadium having different oxidation numbers(hereinafter abbreviated as Oxnum).Molecular modeling studies showed that vanadium with low Oxnum could affect the chemical conversion of large-size hydrocarbon molecules.However,the vanadium deposited on equilibrium catalyst had high Oxnum because of the oxidation reaction taking place in the regenerator,so an activation method to reduce vanadium Oxnum named "selective activation" was introduced.It was proved by means of Electron Paramagnetic Resonance(EPR) and Temperature-Programmed Reduction(TPR) methods that the vanadium Oxnum was decreased,when the catalyst was activated.The molecular modeling studies are consistent well with the lab evaluation results.The light olefins selectivity of activated equilibrium catalysts was better than that achieved by the inactivated catalysts.Similar results were observed with the lab vanadium-contaminated catalyst.The light olefins selectivity of the catalyst was optimized when the vanadium Oxnum was close to 2(VO).

Ni/Al_2O_3 catalysts for CO methanation: Effect of Al_2O_3 supports calcined at different temperatures

The correlation between phase structures and surface acidity of Al2O3 supports calcined at different temperatures and the catalytic performance of Ni/Al2O3 catalysts in the production of synthetic natural gas(SNG) via CO methanation was systematically investigated. A series of 10 wt% NiO/Al2O3 catalysts were prepared by the conventional impregnation method, and the phase structures and surface acidity of Al2O3 supports were adjusted by calcining the commercial γ-Al2O3 at different temperatures(600–1200 C). CO methanation reaction was carried out in the temperature range of 300–600 C at different weight hourly space velocities(WHSV = 30000 and 120000 mL·g-1h-1) and pressures(0.1 and 3.0 MPa). It was found that high calcination temperature not only led to the growth in Ni particle size, but also weakened the interaction between Ni nanoparticles and Al2O3 supports due to the rapid decrease of the specific surface area and acidity of Al2O3 supports. Interestingly, Ni catalysts supported on Al2O3 calcined at 1200 C(Ni/Al2O3-1200) exhibited the best catalytic activity for CO methanation under different reaction conditions. Lifetime reaction tests also indicated that Ni/Al2O3-1200 was the most active and stable catalyst compared with the other three catalysts, whose supports were calcined at lower temperatures(600, 800 and 1000 C). These findings would therefore be helpful to develop Ni/Al2O3 methanation catalyst for SNG production.

Growth of straight carbon nanotubes by simple thermal chemical vapor deposition

Straight carbon nanotubes (CNTs) were achieved by simple thermal chemical vapor deposition(STCVD) catalyzed by Mo-Fe alloy catalyst on silica supporting substrate at 700℃. High-resolution transmission electron microscopy images show that the straight CNTs are well graphitized with no attached amorphous carbon. Mo-Fe alloy catalyst particles play a very crucial role in the growth of straight CNTs. The straight carbon nanotubes contain much less defects than the curved nanotubes and might have potential applications for nanoelectrical devices in the future. The simple synthesis of straight CNTs may have benefit for large-scale productions.

Hydrogen as Carbon Gasifying Agent During Glycerol Steam Reforming over Bimetallic Co-Ni Catalyst

Alumina-supported bimetallic cobalt-nickel catalyst has been prepared and employed in a fixed-bed reactor for the direct production of synthesis gas from glycerol steam reforming. Physicochemical properties of the 5Co-10Ni/85Al2O3 catalyst were determined from N2-physisorption, H2-chemisorption, CO2 and NH3-temperature-programmed desorption measurements as well as X-ray diffraction analysis. Both weak and strong acid sites are present on the catalyst surface. The acidic:basic ratio is about 7. Carbon deposition was evident at 923 K;addition of H2 however has managed to reduce the carbon deposition. Significantly, this has resulted in the increment of CH4 formation rate, consistent with the increased carbon gasification and methanation. Carbon deposition was almost non-existent, particularly at 1023 K. In addition, the inclusion of hydrogen also has contributed to the decrease of CO2 and increase of CO formation rates. This was attributed to the reverse water-gas-shift reaction. Overall, both the CO2:CO and CO2:CH4 ratios decrease with the hydrogen partial pressure.