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《应用化工》2016,(5)
以ZSM-5分子筛为载体,通过等体积浸渍法制备了Co/ZSM-5系列催化剂,用于费托合成反应一步法制汽油馏分烃(C_5~C_(11)烷烃)。考察了不同硅铝比(Si O_2/Al_2O_3=25,38,50,80和200)的ZSM-5分子筛对Co/ZSM-5催化剂费托合成汽油馏分选择性的影响。采用氮气物理吸附-脱附、X射线衍射、氢气程序升温还原(H_2-TPR)和氨气程序升温脱附(NH_3-TPD)等手段对载体和催化剂进行了表征,并在高压固定床反应器上对催化剂的费托合成催化性能进行了测试。结果表明,对比Co/ZSM-5(Si O_2/Al_2O_3=25,38,50和80)催化剂,Co/ZSM-5(Si O_2/Al_2O_3=200)催化剂表现出最高的汽油馏分烃类选择性,高达52.8%,这主要归功于Co/ZSM-5(Si O_2/Al_2O_3=200)催化剂上较小钴颗粒尺寸、较优的还原性能以及适量弱酸位的协同作用。分子筛的酸性为催化剂的加氢裂解转化提供活性位,促进重质烃产物发生裂解和异构等二次反应,较小的钴颗粒尺寸和较优的还原性能有利于提高C_5~+烃选择性。 相似文献
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CO_2加氢直接合成汽油不仅有利于CO_2减排,还可减轻人们对化石能源的依赖。汽油馏分烃产物组成是决定汽油燃料品质的重要因素,其调控是该过程具有挑战性的研究热点。研究NaFe_3O_4/ZSM-5催化剂中分子筛的金属(La,Ga,Zn,Cu,Co)改性对CO_2加氢产物中汽油馏分烃组成的影响,结果表明,与其他金属相比,Cu改性ZSM-5分子筛组分可在保持较高汽油收率前提下,明显提高汽油产物中异构烷烃选择性。优化改性分子筛中Cu质量分数8%时,汽油馏分烃产物中异构烷烃含量最高。当Na-Fe_3O_4和Cu-ZSM-5采用分层填装方式时,汽油馏分烃产物中异构烷烃含量达50.5%,组成调控后富含异构烷烃汽油产品更符合汽油品质升级趋势需求。 相似文献
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《工业催化》2010,(6)
<正> (专业生产各类特种分子筛和催化剂) 南京黄马化工有限公司位于南京市东郊,是国内规模较大的专业生产各类ZSM-5沸石分子筛、丝光沸石、β分子筛、其它介孔沸石分子筛等的特种分子筛和催化剂厂。特种分子筛主要产品有:不同硅铝比ZSM-5分子筛,从低硅(SiO_2/Al_2O_3=25~30)、常规(SiO_2/Al_2O_3=32~40)、中硅(SiO_2/Al_2O_3=50~120)到高硅(SiO_2/Al_2O_3=260~300);不同晶粒度ZSM-5分子筛从大晶粒(1~4μm)、小晶粒(200~500 nm)到纳米级(100~200 nm)ZSM-5分子筛;钠型和氢型丝光沸石; 相似文献
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以不同孔道结构Al_2O_3作载体,甲醇、乙醇和柠檬酸作分散剂,通过等体积浸渍法制备系列Co/Al_2O_3费托合成催化剂。采用XRD、TG-DSC和H2-TPR等考察制备方法对催化剂结构的影响,并在固定床反应器中对催化剂进行性能评价。结果表明,采用具有适宜孔道结构Al_2O_3作载体才能获得综合性能较好的催化剂,3种分散剂的加入,促进了钴物种在载体上的分散,增强了钴与载体间的相互作用,改善了催化剂费托合成反应活性,显著提高了重质烃时空收率。 相似文献
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为了获得催化裂解制备低碳烯烃的高效催化剂,以等体积浸渍法制备了系列单金属(Ce, Y, Zr, Mn, Cu)及双金属(Zr-Ce, Mn-Ce, Y-Ce, Cu-Ce)改性ZSM-5-USY复合分子筛催化剂,通过XRD, NH3-TPD, BET等方法表征了其物理化学性质,并将所制备催化剂用于催化裂解正己烷。结果表明,催化剂的弱酸量越多,正己烷转化率及C2~C4烯烃选择性越高,Zr-Ce共改性分子筛的催化活性较优。水蒸气处理对Zr-Ce/ZSM-5-USY催化剂的酸性及催化裂解产物分布有较大影响,经水蒸气处理的催化剂性能更稳定,可将裂解产物中低碳烯烃的选择性由20.02% (催化剂未经水蒸气处理)提高到57.55% (催化剂经水蒸气处理4 h)。研究了0.25% Zr-0.5% Ce/ZSM-5-USY催化体系的裂解反应动力学,正己烷裂解为一级反应,裂解活化能为88.93 kJ/mol。 相似文献
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采用浸渍法制备了一系列Ce、Zr改性Mn/ZSM-5分子筛催化剂,对其C_3H_6-SCR(选择性催化还原)反应性能进行了评价,研究了Ce、Zr的引入对Mn/ZSM-5分子筛催化剂选择催化还原NO的影响,并采用X射线衍射、比表面积测量、扫描电子显微镜、NH_3-程序升温脱附(TPD)、H_2-程序升温还原(TPR)等表征手段对催化剂的物理化学性质进行了表征。结果表明:Ce、 Zr改性Mn/ZSM-5分子筛催化剂C_3H_6-SCR反应中表现出较为优异的催化活性,最优配比的20%Mn-7%Ce-1%Zr/ZSM-5催化剂在200℃、30000h~(-1)的空速下,催化剂的最大脱硝效率达到87%,且操作温度窗口T50=150~380℃。活性组分Mn以MnO_2和Mn_2O_3形式存在,且与助剂Ce、Zr高度分散在催化剂表面,而且形成协同作用;催化剂表面的弱酸和中强酸和氧化还原性能的增强有利于C_3H_6-SCR低温催化活性的提高。 相似文献
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In glasses with the compositions (100 ? x)(2Na2O·16K2O·8Al2O3·74SiO2)xBaF2 (with x = 0 to 6), the glass transition temperature decreases with increasing BaF2-concentration. Samples with x = 6 were thermally treated at temperatures in the range from 500 to 600 °C for 5–160 h. This leads to the crystallisation of BaF2. The quantity of crystalline BaF2 increases with increasing time of thermal treatment, while the mean crystallite size remains constant within the limits of error. The glass transformation temperature of partially crystallised samples increases with increasing crystallisation time and approaches a value equal to the temperature, at which the samples were treated. This is explained by the formation of a highly viscous layer enriched in SiO2 which is formed during crystallisation. This layer acts as a diffusion barrier and hinders further crystal growth. 相似文献
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In earlier work, a prediction method of the immiscibility boundary of a ternary silicate glass system was developed involving two known binary immiscibility boundaries and a measured immiscibility temperature of one ternary glass composition. In the present work, the method is extended to the case where one of the two binary immiscibility boundaries is not known and is applied as an example to ternary silicate systems containing K2 O. First, the immiscibility boundary of the system K2 O-SiO2 is estimated by measuring the immiscibility temperatures of three glasses in the system K2 O-Li2 O (or Na2 O)-SiO2 . Using this result the immiscibility boundaries of the systems K2 O-Li2 O-SiO2 , K2 O-Na2 O-SiO2 , and K2 O-BaO-SiO2 are estimated. The results agree reasonably well with the experimentally determined immiscibility temperatures at selected compositions. 相似文献
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BURNHAM W. KING 《Journal of the American Ceramic Society》1954,37(5):238-242
It was first shown that the enamel slips which have the best suspnding characteristics contain equal amounts of Na2 O and B2 O3 and at least a moderate amount of NaF. The solubilities of mixtures of Na2 O, NaF, and B2 O3 were then investigated. The pH of these solutions and the primary crystalline phases separating on evaporation also were determined. The solubility data obtained at room temperature were summarized. When the solutions were evaporated, NaF was the first crystalline phase to separate from a large proportion of the mixtures investigated. It was concluded that the desirable handling characteristics of enamels whose mill liquors contain the proper proportion of Na2 O, NaF, and B2 O3 are not due to the formation of complex salts but to the following combination of properties: (1) the presence of salts with a moderate solubility which changes very slightly with temperature, (2) a moderate pH of about 10 in a probably well-buffered solution, (3) a relatively stable crystalline material, NaF, as a primary phase, and (4) a secondary phase which crystallizes slowly with relatively little shrinkage. 相似文献
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Yong Sig Ko 《Powder Technology》2004,145(1):10-19
Zeolite L powder was prepared from the substrate mixture of Na2O-K2O-Al2O3-SiO2-H2O system at temperatures of 373-443 K. In order to investigate the factors which influence the synthesis outcome, a reference system which yields zeolite L in a reproducible manner was chosen and subjected to controlled changes in synthesis parameters. The crystalline zeolite L samples obtained were characterized by elemental chemical analysis, X-ray diffraction (XRD), and scanning electron microscopy (SEM). It was established that phase purity, morphology, and the size of crystals of crystalline product were affected by molar ratios of the substrate, such as SiO2/Al2O3, (K2O+Na2O)/SiO2, Na2O/(K2O+Na2O), and H2O/(K2O+Na2O). Amorphous silica powder (Zeosil) was the preferred silica source, and the crystallization rate was promoted by introducing gel aging, seeding, and rapid heating rate. 相似文献
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M. F. DILMORE D. E. CLARK L. L. HENCH 《Journal of the American Ceramic Society》1978,61(9-10):439-443
The mixed-alkali effect on chemical durability was evaluated for bulk and powdered Na2 O-K2 O-CaO-SiO2 glasses. Two contributions to this effect are discussed, i.e. those of glass structure and corrosion solution. The magnitude of the mixed-alkali effect depends on the pH of the corroding solution. For pH<9, alkali-ion leaching is the major mode of glass corrosion, and the mixed-alkali effect is large. However, for pH≥9 congruent glass dissolution is the rate-controlling corrosion mechanism, and the effect is diminished. When ion exchange is the rate-controlling corrosion mechanism the magnitude of the mixed-alkali effect depends on the extent of reaction. Since the kinetics of corrosion are influenced by the ratio of glass surface area to solution volume ( SA/V ), results obtained when this ratio is large may be misleading if extrapolated to smaller ratios. Physical evidence of the mixed-alkali effect in bulk glasses was obtained using scanning electron microscopy and ir reflection spectroscopy. 相似文献
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Cu2O/TiO2, Bi2O3/TiO2 and ZnMn2O4/TiO2 heterojunctions were studied for potential applications in water decontamination technology and their capacity to induce an oxidation process under VIS light. UV–vis spectroscopy analysis showed that the junctions-based Cu2O, Bi2O3 and ZnMn2O4 are able to absorb a large part of visible light (respectively, up to 650, 460 and 1000 nm). This fact was confirmed in the case of Cu2O/TiO2 and Bi2O3/TiO2 by photocatalytic experiments performed under visible light. A part of the charge recombination that can take place when both semiconductors are excited was observed when a photocatalytic experiment was performed under UV–vis illumination. Orange II, 4-hydroxybenzoic and benzamide were used as pollutants in the experiment. Photoactivity of the junctions was found to be strongly dependent on the substrate. The different phenomena that were observed in each case are discussed. 相似文献
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O_2/N_2、O_2/CO_2和O_2/CO_2/NO气氛下煤粉燃烧NO_x排放特性 总被引:1,自引:0,他引:1
利用滴管炉研究了O2/N2、O2/CO2和O2/CO2/NO气氛下煤燃烧过程中NOx的排放特性。实验结果表明,在O2/N2和O2/CO2气氛下,高温或高O2浓度均使NO排放量增加。O2/CO2气氛下NO排放量比O2/N2气氛下NO排放量低大约30%~40%。在O2/CO2/NO气氛下,温度不同时,O2浓度变化对NO排放量的影响规律不同,对循环NO降解的影响规律也不同。高温不利于循环NO降解。随停留时间的延长NO排放量出现两个峰值。 相似文献
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Paul Wencil Brown 《Journal of the American Ceramic Society》1990,73(11):3457-3461
A portion of the quaternary phase diagram for Na2 O-CaO-SiO2 -H2 O has been constructed. Plotting concentrations as their 10th roots allows compounds having solubilities which differ by several orders of magnitude to be represented on a single diagram. The compositional relationships among sodium-substituted calcium silicate hydrate, calcium-substituted sodium silicate hydrate, calcium bydroxide, a quaternary compound of approximate composition 0.25Na2 O · CaO · SiO2 · 3H2 O, sodium hydroxide monohydrate, and miscellaneous sodium silicate hydrates are presented. The quaternary diagram constructed shows the quaternary compound to exist in equilibrium with sodium-substituted calcium silicate hydrate and calcium hydroxide. Conditions in concrete pore solutions which favor the formation of this quaternary compound may also favor the occurrence of the alkali-silica reaction. 相似文献