Ni取代六铝酸镧催化剂LaNiAl_(11)O_(19)表面积炭研究

通过 TEM、XPS、TGA、TPR-CO2 技术 ,对在 Ni取代六铝酸镧催化剂 La Ni Al1 1 O1 9表面上的甲烷裂解积炭、甲烷二氧化碳重整积炭及二氧化碳的消炭行为进行了研究 ,以探索该催化剂表面积炭形貌、来源、积炭物种以及积炭活性 .结果表明 ,甲烷具有相当高的裂解积炭活性 ,裂解后生成炭化物 ( carbide炭 )和石墨炭两种不同活性的炭种 ;二氧化碳的解离活性则相对较低 ,但其消除催化剂表面积炭活性却相当高     

Ni基六铝酸镧LaNiAl11O19催化剂表面甲烷CO2的重整积炭速率

甲烷二氧化碳重整制合成气反应过程中,催化剂表面积炭是制约催化反应顺利进行的关键因素。研究催化剂表面积炭物种及积炭速率,找出影响催化剂表面积炭的动力学因素,对建立合理的催化重整反应体系,完善催化剂表面积炭的动力学理论具有重要的理论和实际意义。目前有关催化剂表面积炭速率的研究报道较少[1,2]。Ｎｉ基六铝酸盐催化剂对甲烷二氧化碳重整制合成气具有很好的催化活性和稳定性[3,4]。本文利用Ｘ 射线光电子能谱(ＸＰＳ)和热重分析(ＴＧＡ)技术,在还原态Ｎｉ基六铝酸镧ＬａＮｉＡｌ11Ｏ19催化剂表面研究了甲烷裂解积炭和甲烷二氧…     

Ni-Mg复合催化剂催化裂解CH_4制氢动力学研究

基于定温热重实验,建立了甲烷催化裂解反应动力学模型和催化剂表面积炭失活动力学模型。其中,甲烷催化裂解动力学模型将初始产氢速率视为催化剂未积炭条件下的动力学基础数据;催化剂表面积炭失活动力学则基于甲烷催化裂解速率的降低。实验使用Ni-Mg复合催化剂,分别在535、585、635℃,甲烷分压10~4、2×10~4、3×10~4Pa条件下展开甲烷催化裂解动力学特性研究。结果表明,甲烷催化裂解的反应级数为0.5,活化能为82 k J/mol;Ni-Mg复合催化剂反应失活级数为0.5,催化剂失活活化能为118 k J/mol。实验条件下均制得了多壁碳纳米管。     

CH4、CO2与O2制合成气催化剂研究Ⅵ.催化剂表面积炭种类和积炭动力学研究

利用XPS考察了甲烷、二氧化碳和氧气制合成气反应前后Ni/γ-Al2O3和Ni-Ce-Mn-Li/γ-Al2O3催化剂表面炭物种.发现反应后Ni/γ-Al2O3催化剂表面积炭有四种类型-表面碳酸盐、污染炭、金属炭化物和非活性炭,而高活性和稳定性Ni-Ce-Mn-Li/γ-Al 2O3催化剂表面积炭仅有两种类型--污染炭和金属炭化物.非活性炭是导致催化剂失活的主要原因之一.积炭动力学研究表明: Ni-Ce-Mn-Li/γ-Al 2O 3催化剂上积炭反应的动力学方程为: r0=A·e(-E)/(RT)·PCH41.1·PO2-0.45·PO2-1.80,该催化剂积炭反应的表观活化能较高,从而抑制积炭反应的进行.     

CH_4、CO_2与O_2制合成气催化剂研究 VI.催化剂表面积炭种类和积炭动力学研究

利用XPS考察了甲烷、二氧化碳和氧气制合成气反应前后Ni/γ-Al2O3和Ni-Ce-Mn-Li/γ-Al2O3催化剂表面炭物种.发现反应后Ni/γ-Al2O3催化剂表面积炭有四种类型-表面碳酸盐、污染炭、金属炭化物和非活性炭,而高活性和稳定性Ni-Ce-Mn-Li/γ-Al2O3催化剂表面积炭仅有两种类型——污染炭和金属炭化物.非活性炭是导致催化剂失活的主要原因之一.积炭动力学研究表明:Ni-Ce-Mn-Li/γ-Al2O3催化剂上积炭反应的动力学方程为:-0.45·PO2-1.80,该催化剂积炭反应的表观活化能较高,从而抑制积炭反应的进行.1.1·PO2r0=A·e-ERT·PCH4     

CH4、CO2与O2制合成气催化剂研究VI．催化剂表面积炭种类和积炭动力学研究

利用XPS考察了甲烷、二氧化碳和氧气制合成气反应前后Ni/γ-Al2O3和Ni-Ce-Mn-Li/γ-Al2O3催化剂表面炭物种.发现反应后Ni/γ-Al2O3催化剂表面积炭有四种类型-表面碳酸盐、污染炭、金属炭化物和非活性炭,而高活性和稳定性Ni-Ce-Mn-Li/γ-Al 2O3催化剂表面积炭仅有两种类型--污染炭和金属炭化物.非活性炭是导致催化剂失活的主要原因之一.积炭动力学研究表明 Ni-Ce-Mn-Li/γ-Al 2O 3催化剂上积炭反应的动力学方程为 r0=A·e(-E)/(RT)·PCH41.1·PO2-0.45·PO2-1.80,该催化剂积炭反应的表观活化能较高,从而抑制积炭反应的进行.     

低Ni含量和低比表面积六铝酸盐LaNiAl11O19-δ催化剂上CH4-CO2重整反应的积炭

 利用 X 射线粉末衍射、氢程序升温还原、X 射线光电子能谱和透射电镜技术研究了在低 Ni 含量和低比表面积六铝酸盐催化剂 LaNiAl11O19-δ 上 CH4-CO2 重整反应的积炭行为, 考察了该催化剂表面积炭的形貌、来源、积炭物种及其反应性能. 结果表明, LaNiAl11O19-δ 催化剂表面积炭主要由甲烷裂解产生, 并以 Ni 的碳化物形式存在于活性中心 Ni 的周围. 根据积炭物种活化程度的难易可分为 Cα, Cβ和 Cγ 三种类型, 其中 Cα 为容易被 CO2 消除的化合碳, 而 Cβ 和 Cγ则是不易被 CO2 消除的石墨碳. 透射电镜结果表明, Cα 以碳纳米管形式分布于催化剂颗粒周围, 但金属 Ni 活性中心仍能暴露于气相中, 因而不影响催化剂的活性.     

低Ni含量和低比表面积六铝酸盐LaNiAl_(11)O_(19-δ)催化剂上CH_4-CO_2重整反应的积炭

利用X射线粉末衍射、氢程序升温还原、X射线光电子能谱和透射电镜技术研究了在低Ni含量和低比表面积六铝酸盐催化剂LaNiAl_(11)O_(19-δ)上CH_4-CO_2重整反应的积炭行为,考察了该催化剂表面积炭的形貌、来源、积炭物种及其反应性能.结果表明,LaNiAl_(11)O_(19-δ)催化剂表面积炭主要由甲烷裂解产生,并以Ni的碳化物形式存在于活性中心Ni的周围.根据积炭物种活化程度的难易可分为C_α,C_β和C_γ三种类型,其中C_α为容易被CO_2消除的化合碳,而C_β和C_γ则是不易被CO_2消除的石墨碳.透射电镜结果表明,C_α以碳纳米管形式分布于催化剂颗粒周围,但金属Ni活性中心仍能暴露于气相中,因而不影响催化剂的活性.     

甲烷与二氧化碳重整制取合成气反应的研究：ⅢSr（La）NiAl11O19积炭动力学

用热重（ＴＧＡ）方法，研究了ＬａＮｉＡｌ１１Ｏ１９和ＳｒＮｉ１１Ｏ１９催化剂上甲烷与二氧化碳重整反应的积炭动力学。实验结果表明，甲烷裂解是ＣＨ４＋ＣＯ２反应中主要的积炭反应，甲烷的二氧化碳重整反应的积炭速率随反应温度升高而增大，但春衰减速度也较快；ＣＨ４＋ＣＯ２反应的积炭速率相对甲烷分压的反应级数是１，相对二氧化碳分压的反应级数是一－０５；在ＳｒＮｉＡｌ１１Ｏ１９中掺入Ｌａ＾３＋离子，提高了催化剂     

羟基磷灰石负载Ni催化剂中Ni含量对催化甲烷二氧化碳重整制合成气性能的影响

以低温沉淀方法制备的羟基磷灰石(HAp)为载体,采用浸渍法制备了一系列不同Ni含量的Ni/HAp催化剂,并采用BET、H2-TPR、XRD、SEM、FT-IR、TEM和TG-DTA技术对催化剂进行了表征。结果表明,NiO含量为13%的催化剂表现出最好的催化甲烷二氧化碳重整制合成气活性,在850℃、空速3.6×104mL/(h·gcat)的反应条件下,甲烷和二氧化碳的转化率在10 h内分别稳定在72%和83%。这主要归因于催化剂中金属和载体之间的强相互作用。虽然反应后的催化剂表面有少量的积炭,但这些积炭多以丝状炭存在,并不会影响催化剂的活性和稳定性。     

Phase states in the Bi4Ti3O12-BiFeO3 section in the Bi2O3-TiO2-Fe2O3 system

Specific features of the thermal behavior of Bi _{m + 1}Fe _m−3Ti₃O_{3m + 3} layered perovskite-like compounds (where m takes integer and some fractional values between 3 and 9) were considered, and the temperature limits of stability of these compounds were determined. The phase diagram of the Bi₄Ti₃O₁₂-BiFeO₃ section through the Bi₂O₃-TiO₂-Fe₂O₃ system was constructed.     

Phase relations in the K2W2O7-K2WO4-KPO3-Bi2O3 system and structure of K6.5Bi2.5W4P6O34

The phase relations in the cross-section of the K₂W₂O₇-K₂WO₄-KPO₃ containing 15 mol% Bi₂O₃ were undertaken using flux method. Crystallization fields of K_6.5Bi_2.5W₄P₆O₃₄, K₂Bi(PO₄)(WO₄), Bi₂WO₆, KBi(WO₄)₂ and their cocrystallization areas were identified. Novel phase K_6.5Bi_2.5W₄P₆O₃₄ was characterized by single-crystal X-ray diffraction: sp. gr. P−1, a=9.4170(5), b=9.7166(4), c=17.6050(7) Å, α=90.052(5)°, β=103.880(5)° and γ=90.125(5)°. It has a layered structure, which contains {K₇Bi₅W₈P₁₂O₆₈}_∞ layers stacked parallel to ab plane and sheets composed by potassium atoms separating these layers. Sandwich-like {K₇Bi₅W₈P₁₂O₆₈}_∞ layers are assembled from [W₂P₂O₁₃]_∞ and [BiPO₄]_∞ building units, and are penetrated by tunnels with K/Bi atoms inside. FTIR-spectra of K₂Bi(PO₄)(WO₄) and K_6.5Bi_2.5W₄P₆O₃₄ were discussed on the basis of factor group theory.     

Solubility in the Na2Cr2O7-(NH4)2Cr2O7-K2Cr2O7-H2O system

Solubility in the Na₂Cr₂O₇-(NH₄)₂Cr₂O₇-K₂Cr₂O₇-H₂O four-component water-salt system at 25, 50, and 75°C was studied for the first time. Phase field boundaries for individual salts and potassium and ammonium dichromate solid solutions, monovariant lines, and invariant points were determined. Experimental data were used to optimize the looped isohydric process of potassium dichromate preparation involving additional salts.     

Polymorphism in the Sc2Si2O7-Y2Si2O7 system

This paper examines the structural changes with temperature and composition in the Sc₂Si₂O₇-Y₂Si₂O₇ system; members of this system are expected to form in the intergranular region of Si₃N₄ and SiC structural ceramics when sintered with the aid of Y₂O₃ and Sc₂O₃ mixtures. A set of different compositions have been synthesized using the sol-gel method to obtain a xerogel, which has been calcined at temperatures between 1300 and 1750 °C during different times. The temperature-composition diagram of the system, obtained from powder XRD data, is dominated by the β-RE₂Si₂O₇ polymorph, with γ-RE₂Si₂O₇ and δ-RE₂Si₂O₇ showing very reduced stability fields. Isotherms at 1300 and 1600 °C have been analysed in detail to evaluate the solid solubility of the components. Although, the XRD data show a complete solid solubility of β-Sc₂Si₂O₇ in β-Y₂Si₂O₇ at 1300 °C, the ²⁹Si MAS-NMR spectra indicate a local structural change at x ca. 1.15 (Sc_2−xY_xSi₂O₇) related to the configuration of the Si tetrahedron, which does not affect the long-range order of the β-RE₂Si₂O₇ structure. Finally, it is interesting to note that, although Sc₂Si₂O₇ shows a unique stable polymorph (β), Sc³⁺ is able to replace Y³⁺ in γ-Y₂Si₂O₇ in the compositional range 1.86?x?2 (where x is Sc_2−xY_xSi₂O₇) as well as in δ-Y₂Si₂O₇ for compositions much closer to the pure Y₂Si₂O₇.     

Phase equilibria and glass formation in the As2S3-TlAs2S2Se2 section of the As2S3-As2Se3-TlS system

Alloys in the As₂S₃-TlAs₂S₂Se₂ section of the As₂S₃-As₂Se₃-TlS ternary system were studied and a phase diagram was constructed using physicochemical methods (differential thermal analysis, microstructural analysis, X-ray powder diffraction, also microhardness and density measurements). The diagram in the As₂S₃-TlAs₂S₂Se₂ section is a non-quasi-binary diagonal section of the As₂S₃-As₂Se₃-TlSe quasi-ternary system. It was found that all the alloys in the section under ordinary conditions are obtained in the vitreous state. At low As₂S₃ concentrations in the section, solid solutions form up to 2.5 mol %, and at low TlAs₂S₂Se₂ concentrations, their extent is 3 mol %.     

Structural study of the NaCdVO4-Cd3V2O8 and CdO-V2O5 sections of the ternary system Na2O-CdO-V2O5

The NaCdVO₄-Cd₃V₂O₈ and CdO-V₂O₅ sections of the ternary system Na₂O-CdO-V₂O₅ have been studied and the crystal structures of Cd₃V₂O₈ and Cd₁₈V₈O₃₈ compounds were determined from single-crystal X-ray diffraction data. Cd₃V₂O₈ crystallizes with the maricite-type structure in space group Pnma, a=9.8133(10) Å, b=6.9882(10) Å, c=5.3251(10) Å and Z=4, whereas Cd₁₈V₈O₃₈ crystallizes in space group P1 with a new-type structure, a=8.5761(14), b=8.607(3), c=12.896(2) Å, α=95.64(1), β=102.45(1), γ=108.42(1)° and Z=1. The Cd₃V₂O₈ structure is made up of Cd1O₄ infinite chains of edge-sharing Cd1O₆ octahedra which are parallel to the b direction. The Cd1O₄ chains are linked together by VO₄ tetrahedra and strongly distorted Cd2O₄ tetrahedra. The structure of Cd₁₈V₈O₃₈ is based on an ordered three-dimensional framework of cadmium and vanadium polyhedra that share corners. The distorted CdO₆ octahedra, CdO₅ trigonal bipyramids and CdO₅ square pyramids share corners, edges or faces.     

Phase diagram of the In3As2Se6-In3As2S3Se3 system

The In₃As₂Se₆-In₃As₂S₃Se₃ system has been investigated by methods of physicochemical analysis (DTA, X-ray powder diffraction, MSA) and by microhardness and density measurements. The phase diagram of the system, which is the quasi-binary section of the As-In-S-Se quaternary system, has been constructed. The region of the In₃As₂Se₆-based solid solutions is extended to 7 mol %, and the In ₃As₂S₃Se₃-based region to 15 mol %. A new quaternary compound In₆As₄S₃Se₉ is found in the system. Original Russian Text ? I.I. Aliev, R.S. Magammedragimova, A.A. Farzaliev, Dzh. Veliev, 2009, published in Zhurnal Neorganicheskoi Khimii, 2009, Vol. 54, No. 4, pp. 691–694.     

Some studies on the solid solutions in the systems Sr2Nb2O7Eu2Nb2O7 and Sr2Ta2O7Eu2Ta2O7

Preparation of new solid solutions containing divalent europium have been tried in the systems Eu₂Nb₂O₇Sr₂Nb₂O₇ and Eu₂Ta₂O₇Sr₂Ta₂O₇. These solid solutions described as Eu_2xSr_2(1?x)M₂O₇ (M = Nb and Ta) exist in a pure orthorhombic phase in a limited region of x from 0 to about 0.5. The compounds with compositions close to Eu₂M₂O₇ exist but techniques have not been found to prepare them in pure form.     

SnSbBiS4-SnS and SnSbBiS4-Sn2Sb6S11 sections of the SnS-Sb2S3-Bi2S3 ternary system

SnSbBiS₄-SnS and SnSbBiS₄-Sn₂Sb₆S₁₁ sections were studied by physicochemical methods (DTA, X-ray powder diffraction, microstructure observation, and microhardness measurements). These sections were found to be eutectic quasi-binary sections of the SnS-Sb₂S₃-Bi₂S₃ ternary system. Solid solution regions based on the initial components were found on either side of the sections. Alloys in the solid solution region are p-type semiconductors.     

Phase diagram of the Pb5Sb4S11-Pb2SnSb2S6 system

The Pb₅Sb₄S₁₁-Pb₂SnSb₂S₆ system was studied by a number of physicochemical methods, and its phase diagram was constructed. It was found that the system under investigation is a quasi-binary eutectic type section of the SnS-PbS-Sb₂S₃ ternary system. The coordinates of the eutectic are found to be 33 mol % Pb₅Sb₄S₁₁ and 750 K. Regions of solid solutions based on Pb₅Sb₄S₁₁ (6 mol % Pb₂SnSb₂S₆) and Pb₂SnSb₂S₆ (4 mol % Pb₅Sb₄S₁₁) were determined.