载钴分子筛的XPS研究

借助XPS技术研究了浸渍法得到的3种载钴分子筛Co/HY、Co/ZSM-5和Co/HA的表面状态和组成.结果表明,这些分子筛的表面深处都有难被还原的类CoAl₂O₄物种存在,而易被还原的钴羟基化合物覆盖于分子筛的表面.空气焙烧加快了类CoAl₂O₄物种的生成.用H₂还原实验考察了3种载钴分子筛上钴物种与分子筛之间相互作用的程度.     

Enhancement of Bio-based para-Xylene Selectivity in Catalytic Fast Pyrolysis of Cellulose Using a Surface-modified Mg/P/HZSM-5 Catalyst

With the growing consumption of oil, the production of /?-xylene(PX) from renewable biomass has gained significant attention recently. This work demonstrated that cellulose, a main component in lignocellulosic biomass, was directly converted into PX over the Mg/P surface-modified zeolites. The catalysts modified by the incorporation of P2O5 and MgO into HZSM-5(HZ) promoted the isomerization of zw-/o-xylenes to p-xylene. The PX selectivity was greatly enhanced using the modified zeolites due to the deactivation of external surface and the adjustment of pore entrance. In addition, the addition of methanol to cellulose was beneficial to increase the selectivity of xylenes due to the alkylation reactions and the Diels-Alder reactions between cellulose-derived furans and methanol-derived olefins. The highest PX yield of 10.7%(molar fraction) with a high PX selectivity in xylenes(97.1%) was obtained over the 10%Mg/5%P/HZ catalyst. The reaction pathway for the formation ofp-xylene was addressed according to the study of the key reactions and the characterization of catalysts.     

具有微孔/大孔双孔道体系沸石材料的合成

近年来 ,随着精细化工反应中大分子及液相反应的增多 ,沸石催化材料由于其孔道狭窄 ,存在较大扩散阻力 ,越来越不能满足反应的需要 .而多级孔道体系材料由于能同时提供不同大小的孔道 ,因此对解决传质问题将会有很大帮助[14].但目前绝大部分研究集中在中孔 /大孔体系[4 6 ],对于微孔 /大孔体系的研究则较少 .最近 ,Ｈｏｌｌａｎｄ等[7]利用硬球模板技术首次制得微孔 /大孔沸石 ,这类材料中由于存在丰富的大孔 ,对解决扩散阻力较大反应中的传质问题可能会有显著功效 ;同时 ,大孔孔壁是由晶化的微孔沸石构成 ,因此将期望具有较好的水热稳定性…     

Co2+/ Co(0) redox couple revealed by EPR spectroscopy triggers preferential coordination of reactants during SCR of NOx with propene over cobalt-exchanged zeolites

Catalytic reduction of NOx with propene over Co2+ -exchanged beta and ZSM-5 zeolites occurs with formation of zero-valent cobalt; NOx preferentially adsorbed on Co2+ plays the role of a metal reducing agent while ligation of propene is favored for Co(0) centers.     

Cation control of pore and channel size in cage-based metal-organic porous materials

Porous materials resembling zeolites that are composed of organic and inorganic building units were synthesized and characterized. Control of pore and channel size was achieved by using different-sized cations. The metal-assembled, anionic cage molecule, Co(4)1(2)(8-), with a hydrophobic cavity and four carboxylate rich arms, was used as a structural unit for the formation of materials with pores and channels. When assembled into a solid material with dications (Mg(2+), Ca(2+), Sr(2+), and Ba(2+)), Co(4)1(2)(8-) arranges into sheets of cages linked together by cations. The series of materials based on Co(4)1(2)(8-) and containing alkaline earth cations was characterized using X-ray crystallography. The magnesium material packs with cages close together, has small channels, and has cation-carboxylate linkages in three dimensions. The calcium material has cages packed with voids between them and has 5 x 10 A channels and 10 x 21 A pores. The strontium and barium materials also pack with voids between the cages and similarly to each other. They have 11 x 13 A and 11 x 11 A channels and 10 x 27 A and 9 x 27 A pores, respectively. Each of these materials has many (20-50) solvent water molecules associated with each cage. The associated water can be removed from and adsorbed by the materials. The heat of water binding has been measured to be -52 kJ/mol (Mg(4)Co(4)1(2)); -47 kJ/mol (Ca(4)Co(4)1(2)); -48 kJ/mol (Sr(4)Co(4)1(2)); -49 kJ/mol (Ba(4)Co(4)1(2)).     

弱酸性多级孔MFI沸石上甲醇转化制丙烯（英文）

使用葡萄糖辅助模板合成了H-[B,Al]-ZSM-5沸石并用于催化甲醇转化制丙烯。优越的丙烯选择性和活性持久性关联于有利于丙烯生成的高的弱酸/强酸比例以及有利于改善反应物扩散的防止快速积炭的高的介孔率。较多的位于MFI沸石直/正弦孔道的骨架铝增加了产物丙烯/乙烯比归因于促进的丙烯生成。低的酸密度有助于高的丙烯/乙烯比。B/Al比为2且（Al₂+B₂）/Si比为0.01的HZ5-G-2B样品用于甲醇制丙烯反应,在原料CH₃OH/H₂O（1∶1.2）重时空速为1.8 h^-1、480°C反应条件下,丙烯选择性为51.6%, C_2-4⁼烯烃选择性为83.7%,甲醇完全转化。丙烯/乙烯比为2。催化活性保持580 h稳定。     

高硅沸石合成中四氢呋喃模板作用的初步研究

在四氢呋喃(THF)-Na~2O-SiO~2-Al~2O~3-H~2O体系中,水热条件下合成出的沸石相,随配料硅铝比提高,依次为MOR(丝光沸石),ZSM-35,ZSM-5和ZSM-39,1^3^CCP/MASNMR谱,TG/DTG/DTA和EDX成分分析方法对沸石中的THF进行表征,1^3^C谱化学位移的显著变化,以及THF高的脱除温度,证明作为模板剂的THF分子进入所合成的沸石结构,并与骨架发生强的相互作用。     

钛酸盐(钴、镓)沸石分子筛的合成与表征

钛酸钴;钛酸镓;水热合成;钛酸盐(钴、镓)沸石分子筛的合成与表征     

金属改性P/HZSM-5分子筛催化乙醇芳构化

以P/HZSM-5分子筛为基础, 通过浸渍法制备了Cr、Co、Cu、Zn等金属改性的M-P/HZSM-5分子筛. 采用X射线衍射(XRD), 比表面积(BET)和氨气程序升温(NH₃-TPD)等方法对其进行了表征, 并考察了其催化乙醇芳构化的活性. 结果表明, 改性后的ZSM-5分子筛保持原有的骨架结构, 但比表面积降低, 酸性分布发生变化; Cu-P/HZSM-5分子筛有较高催化活性. P和Cu的负载量分别为3%和5%, 先浸渍P再浸渍Cu, 反应温度400 °C, 质量空速(WHSV)为1.0 h^-1时轻质芳烃(BTX)收率可达到57.6%.     

A new synthetic route to produce metal zeolites with subnanometric magnetic clusters

By using a Co layered silicate as a source of Co and SiO(2), Co-Beta and Co-ZSM-5 zeolites with tetrahedrically coordinated cobalt were synthesized. Subnanometric clusters of Co can be produced and a magnetic material with superparamagnetic-paramagnetic phase transition is obtained.     

Co-ETS-10 and Co-AM-6 as active catalysts for the oxidation of styrene to styrene oxide and benzaldehyde using molecular oxygen

Pristine ETS-10 and AM-6 and their Co2+-exchanged forms were prepared, and their catalytic activi-ties toward the oxidation of styrene in oxygen atmosphere were studied in dimethylformamide. The catalysts were denoted as Co-E10-n (n=0, 9, 26, 68, 81) and Co-A6-m (m=0, 8, 23, 63, 79), where n and m denote the degree of Co2+exchange. The products of the oxidation process were identified as styrene epoxide (E) and benzaldehyde (B). Both the pristine forms, ETS-10 (Co-E10-0) and AM-6 (Co-A6-0), and Co2+-exchanged forms displayed catalytic activities. With increasing n or m, the con-version, and hence the rate, increased. Specifically, the rates varied from 6.1 to 12.5 mmol·g?1·h?1 with increasing n (Co-E10-n catalysts) and from 5.4 to 12.4 mmol·g?1·h?1 with increasing m (Co-A6-m catalysts). In contrast, the E/B ratio decreased with increasing n or m. More specifically, the E/B ratio decreased from 2.1 to 0.1 with increasing n from 0 to 81 (Co-E10-n catalysts) and from 1.3 to 0.1 with increasing m from 0 to 79 (Co-A6-m catalysts). Co-E10-9 displayed the highest E yield and Co-A6-79 generated the highest B yield. The highest turnover frequency obtained was 36.3 Co?1·h?1, which was the highest one obtained among those obtained for the Co2+-exchanged zeolites and mesoporous silica reference materials studied in this work.     

Electro-oxidation of hydrazine at gold nanoparticle functionalised single walled carbon nanotube network ultramicroelectrodes

Networks of pristine single walled carbon nanotubes (SWNTs) grown by catalysed chemical vapour deposition (cCVD) on an insulating surface and arranged in an ultramicroelectrode (UME) format are insensitive to the electro-oxidation of hydrazine (HZ) in aqueous solution, indicating a negligible metallic nanoparticle content. Sensitisation of the network towards HZ oxidation is promoted by the deliberate and controlled electrodeposition of "naked" gold (Au) nanoparticles (NPs). By controlling the deposition conditions (potential, time) it is possible to control the size and spacing of the Au NPs on the underlying SWNT network. Two different cases are considered: Au NPs at a number density of 250 ± 13 NPs μm(-2) and height 24 nm ± 5 (effective surface coverage, θ = 92%) and (ii) Au NPs of number density ~ 22 ± 3 NPs μm(-2) and height 43 nm ± 8 nm (θ = 35%). For both morphologies the HZ oxidation half-wave potential (E(1/2)) is shifted significantly negative by ca. 200 mV, compared to a gold disc UME of the same geometric area, indicating significantly more facile electron transfer kinetics. E(1/2) for HZ oxidation for the higher density Au NP-SWNT structure is shifted slightly more negative (by ~25 mV) than E(1/2) for the lower density Au NP electrode. This is attributed to the lower flux of HZ at NPs in the higher number density arrangement (smaller kinetic demand). Importantly, using this approach, the calculated HZ oxidation current density sensitivities for the Au NP-SWNT electrodes reported here are higher than for many other metal NP functionalised carbon nanotube electrodes.     

碱酸改性ZSM-5分子筛催化剂的噻吩烷基化反应性能研究

以SiO_2/Al_2O_3物质的量比为50的HZSM-5分子筛为原粉,经过一定浓度的NaOH溶液处理后再使用柠檬酸溶液进行酸洗以制备微孔-介孔多级孔HZSM-5催化剂,并研究其在模拟油中的噻吩烷基化反应性能。结果表明,使用柠檬酸溶液进行酸洗可以清除碱处理后孔道内残余的杂质。当柠檬酸溶液浓度为0.5 mol/L时,此时得到的HZ(AC-0.5)催化剂具有适宜的孔径和酸性,因而噻吩烷基化转化率最高,达到95.6%。在HZ(AC-0.5)催化剂上以苯并噻吩作为噻吩衍生物模型化合物,异戊二烯作为烯烃模型化合物,苯作为芳烃模型化合物,分别考察噻吩烷基化反应性能,并分析不同组分的模拟油对噻吩烷基化反应转化率和选择性的影响。结果表明,噻吩烷基化的最佳反应温度是120℃,在该温度下苯并噻吩烷基化的转化率高于噻吩烷基化的转化率,当异戊二烯作为烯烃模型化合物后噻吩的转化率会升高,当苯作为芳烃模型化合物后噻吩的转化率会降低。     

Co2+-exchanged faujasite zeolites as efficient heterogeneous catalysts for epoxidation of styrene with molecular oxygen

Co2+-exchanged faujasite zeolites can efficiently catalyze the epoxidation of styrene with molecular oxygen, and the Co2+ ions located in supercages are suggested to account for the activation of O2 for the epoxidation of styrene.     

Ti－Si沸石表面吸附物种的TPSR－TPD研究

氯丙烯在不同催化剂表面上吸附的ＴＰＤ结果表明：在ＴＳ－１上有三重脱附峰，而在ＴｉＯ２／Ｓｉｌｉｃａｌｉｔｅ上仅有单峰。Ｈ_２Ｏ_２或分子Ｏ_２在催化剂表面吸附后，在脱附物种中可用质谱检测到原子Ｏ（１６）物种；说明Ｈ_Ｏ_２或分子Ｏ_２在样品表面存在解离吸附；并发现解离分子Ｏ_２的活性很低。ＴＳ－１能同时吸附氯丙烯和Ｈ_２Ｏ_２，而在ＳｉＯ_２／Ｓｉｌｉｃａｌｉｔｅ表面的吸附却与吸附顺序有关。环氧化活性顺序如下：ＴＳ－１（ＴＰＡＯＨ）＞ＴＳ－１（ＴＰＡＢｒ＋ＮａＯＨ）＞ＴｉＯ_２／Ｓｉｌｉｃａｌｉｔｅ。ＴＳ－１沸石的高氧化活性可能与Ｈ_２Ｏ_２吸附后表面原子Ｏ（１６）的形成有关。     

用FTIR方法表征一氧化氮在Co／ZSM-5和[Co+Mg(Sr)]／ZSM-5上的吸附

用傅里叶红外光谱（FTIR）方法表征了一氧化氮在Co/ZSM-5上的吸附,在 Co/ZSM-5上主要的吸附物种为Co^2+-(NO)2,它们的红外吸附峰位在1813和 1896cm^-1,Co^2+-NO吸附峰在1939-1941cm^-1区域。并且由这些吸附锋的强度得 NO的吸附量经验关系式：CNO=INO/（εNO·m/3.14）。由此式计算出NO在Co/ZSM- 5和[Co+Mg(Sr)]/ZSM-5上的吸附NO的吸附浓度,另用FTIR方法表征了Co/ZSM-5和 [Co+Mg(Sr)]／ZSM-5的差劲基峰。这些表征为氮氧化物选择性催化还原（SCR）反 应催化剂的研制提供了有用的信息。     

Remarkable effect of the preparation technique on the state of cobalt ions in BEA zeolites evidenced by FTIR spectroscopy of adsorbed CO and NO, TPR and XRD

The state of cobalt in two BEA zeolites was studied by XRD, TPR, and FTIR spectroscopy using CO and NO as probe molecules. One of the samples, CoAlBEA (0.4 wt % of Co), was prepared by conventional ion exchange and the other, CoSiBEA (0.7 wt % Co), by a two-step postsynthesis method involving dealuminated SiBEA zeolite. The introduction of Co into SiBEA leads to an increase of unit cell parameters of the BEA structure and to the consumption of silanol groups in vacant T-sites of the dealuminated zeolite. In contrast, no structural changes are observed after incorporation of cobalt into AlBEA by ion-exchange. The reduction temperature of cobalt in CoSiBEA zeolite (1130 K), is much higher than for CoAlBEA and indicates a strong interaction of cobalt ions with SiBEA. Low-temperature CO adsorption on CoAlBEA results in (i) H-bonded CO, (ii) Co(3+)-CO adducts (2,208 cm(-1)) and (iii) a small amount of Co(2+)-CO complexes (2,188 cm(-1)). In agreement with these results, NO adsorption leads to the appearance of (i) NO(+) (2,133 cm(-1), formed with the participation of the zeolite acidic hydroxyls), (ii) Co(3+)-NO (1932 cm(-1)), and (iii) a small amount of Co(2+)(NO)(2) dinitrosyls (nu(s) = 1,898 and nu(as) = 1,814 cm(-1)). Low-temperature CO adsorption on CoSiBEA leads to formation of two kinds of Co(2+)-CO adducts (2,185 and 2,178 cm(-1)). No Co(3+) cations are detected. In line with these results, adsorption of NO reveals the existence of two kinds of Co(2+)(NO)(2) dinitrosyls (nu(s) = 1,888 and nu(as) = 1,808 cm(-1) and nu(s) = 1,878 and nu(as) = 1,799 cm(-1), respectively).     

C2-C2直链烯烃在HY 和H-ZSM-5分子筛上的吸附

采用ONIOM(B3LYP/6-311++G(d,p):UFF)分层计算方法, 研究了C₂-C₅直链烯烃在HY 和H-ZSM-5 分 子筛上的吸附性质. 理论计算结果表明: 烯烃与分子筛的Br?nsted 酸性位相互作用形成π配位超分子复合物; 随着碳链的增长, 烯烃的吸附能增加, 增加量近似为一个常数(HY 分子筛: 约12 kJ·mol^-1; H-ZSM-5 分子筛: 约 25 kJ·mol^-1), 与烷烃在分子筛上的吸附具有相同的规律. 双键位置对烯烃的吸附能影响很大, 2位烯烃的吸附能 要远大于1 位烯烃的吸附能. 不同类型分子筛对烯烃的吸附性能也有很大差别, 由于局域效应的影响, 小孔径 H-ZSM-5分子筛上的吸附能大于大孔径的HY分子筛,而且碳链越长,这种差别越大.从微观结构上看,吸附的烯 烃与H-ZSM-5分子筛酸性位的距离要远大于它们与HY分子筛酸性位的距离, 这是由于不同类型分子筛的微孔 结构产生的范德华作用是不同的,这种作用随着孔径的减小而增强.前线轨道分析表明, 对于小分子烯烃,大孔径 HY分子筛对其催化活性相近,而小孔径H-ZSM-5分子筛随着烯烃碳原子数的增加催化活性有减弱的趋势.     

Zeolites for nuclear waste treatment: Co,Ni, Zn uptake into synthetic faujasites X & Y

Synthetic zeolites X & Y have been examined for their abilities to take in Co, Ni and Zn radioisotopes. Distribution coefficients (K _d ) have been determined, with and without competing cations, and at various pH values. Elution studies on zeolites containing Co, Ni and Zn radioisotopes considered the effect of acid and alkaline conditions, calcination and cement encapsulation. Leach rates arising from these experiments have been calculated. The general conclusions can be drawn are that zeolites X & Y are suitable for decontamination of aqueous wastes containing Co, Ni and Zn. Cement encapsulation is appropriate but no advantage accrues from pre-calcination. Some comments on the likely mechanism of leaching losses have been made.     

沸石的孔口改性与气体吸附分离

沸石由干具有独特的微孔结构和表面性质，对物质的吸附表现出高度的选择性，已被广泛用于许多工业吸附分离过程．在气体分离方面，最常见的是利用沸石制造纯净的稀有气体和富氧空气．Niwa等［‘－‘］和本实验室［‘’］已成功地采用出（OCH小化学气相沉积方法对HM和Hi8M七沸石进行孔径精细调变，改善了沸石的择形吸附分离和催化性能．本文试图进一步研究沸石孔口改性在气体吸附分离方面的应用潜力．我们选择的H元气体混合物体系是NZ／OZ和CH。川。，因为O。，NZ和CH。三种分子的动力学直径分别为0．346O．364和0．380urn，相差甚…