含硼杂原子Na-B-ZSM-5分子筛对甲醇脱氢制甲醛反应的催化性能

以白炭黑为硅源、硼酸为硼源、NaOH为碱源、四丙基溴化铵(TPABr)和1,6-己二胺(HMDA)混合模板剂,采用水热合成法制备含硼杂原子Na-B-ZSM-5分子筛,用XRD、SEM、FT-IR、UV-vis、11B MAS NMR、NH3-TPD等方法对其进行表征。在连续流动常压固定床反应器上评价Na-B-ZSM-5分子筛对甲醇脱氢制甲醛反应的催化性能,考察n(Si)/n(B)、n(Na2O)/n(SiO2)、晶化温度和晶化时间等制备参数以及反应温度和质量空速等工艺参数对催化性能的影响。结果表明,硼进入了分子筛的骨架结构中,存在与B酸中心有关的骨架四配位硼和与L酸中心有关的骨架三配位硼,Na-B-ZSM-5分子筛含有较多的弱酸位和少量的中强酸位。催化剂的最佳制备参数为n(Si)/n(B)比值为7.5、n(Na2O)/n(SiO2)比值为0.14、晶化温度170℃、晶化时间48 h。Na-B-ZSM-5(7.5)分子筛在反应温度550℃、质量空速1.85 h-1的反应条件下对甲醇的转化率为62.97%,甲醛的选择性为68.86%。     

碱对AlMCM-41合成和催化性能的影响

用无机碱NaOH和有机碱TEAOH合成了不同硅铝比的AlMCM-41介孔分子筛,通过XRD、SEM、TEM、TPDA、吡啶吸附IR和N2等温吸附进行了表征.研究表明,使用TEAOH适合于合成低硅铝比AlMCM-41,而使用NaOH合成高硅铝比的AlMCM-41,所得产物的有序程度较高.由TEAOH合成AlMCM-41的比表面、孔径、总酸量和Brnsted酸量均略大于由NaOH合成的样品,而且对异丙苯裂解和苯与1-十二烯烷基化反应的活性前者也高于后者.     

Compression Behaviour of Ni77P23 Amorphous Alloy up to 30.5 GPa

The compression behaviour of Ni77P23 amorphous alloy is investigated at room temperature in a diamond-anvil cell instrument using in-situ high pressure energy dispersive x-ray diffraction with a synchrotron radiation source. The equation of state is determined by fitting the experimental data according to the Birch-Murnaghan equation. It is found that the structure of Ni77P23 amorphous alloy is stable under pressures up to 30.5 GPa. Within the pressure range from zero to the experimental one, the pressure-induced structural relaxation is reversible.     

Undercooling and Unidirectional Solidification of CuNi Alloy Melts

Cylinder-shaped CusoNi20 alloy melt is undercooled and solidified by the combination of the electromagnetic levitation technique and the flux treatment method. Nearly constant temperature gradient of 8-10 K/cm is realized for the cylindrical melts with differen~ undercooling levels at the bottom ends. The experimental results reveal that with the increase of the undercoo]ing of the melts from 35 to 220 K, the microstructures undergo transition from coarse dendrites to granular grains, unidirectional dendrites, and finally to equiaxed grains.     

Influence of Pressure on the Annealing Process of β-Ca_2SiO_4(C_2S) in Portland Cement

Portland cement is the most common type of cement in general use around the world as a basic ingredient of concrete, mortar, stucco, and non-speciality grout. Dicalcium silicate(Ca_2SiO_4) is the primary constituent of a number of different types of cement. The β-Ca_2SiO_4 phase is metastable at room temperature and will transform into γ-Ca_2SiO_4 at 663 K. In this work, Portland cement is annealed at a temperature of 950 K under pressures in the range of 0–5.5 GPa. The high pressure experiments are carried out in an apparatus with six anvil tops. The effect of high pressure on the obtaining nano-size β-Ca_2SiO_4(C_2 S) process is investigated by x-ray diffraction and transmission electron microscopy. Experimental results show that the grain size of the C_2 S decreases with the increase of pressure. The volume fraction of the C_2 S phase increases with the pressure as the pressure is below3 GPa, and then decreases(P 3 GPa). The nano-effect is very important to the stabilization of β-Ca_2SiO_4. The mechanism for the effects of the high pressure on the annealing process of the Portland cement is also discussed.     

Kinetics of the glass Transition of the Zr41Ti14Cu12.5Ni10Be22.5 Alloy Solidified in a Drop Tube

Droplets of Zr41Ti14Cu12.5Ni10Be22.5 glass-forming alloy with different sizes are solidified in a drop tube containerless process.The glass transition temperature Tg of Zr41Ti14Cu12.5Ni10Be22.5 glassy spheres solidified with different cooling rates is investigated by using a differential scanning calorimeter.It was found that all the amor phous spheres show an increase of Tg with the heating rate.The glassy spheres have a unique value for the glass transition activation energy Eg=435.50kJ/mol,which is independent of cooling rate q.The insensitivity of Tg to q is interpreted by an extension of the free volume model for flow.     

高压Ni77P23非晶合金自由体积变化的同步辐射研究

利用同步辐射高能X光散射的方法，研究了室温下非晶合金Ni₇₇P₂₃的自由体积的变化所引起的压缩行为的变化规律，通过傅里叶变换得到不同压力下的径向分布函数，并由此获得了不同压力下，该非晶合金的配位数、近邻原子间距等原子构型的结构信息. 研究表明，至直30.5GPa压力，Ni₇₇P₂₃合金仍保持稳定的非晶结构,根据Bridgman方程通过拟合数据，得到状态方程为-ΔV/V₀=0.08606P-3.2×10^-4P²+5.7×10^-6P³. 关键词： 非晶合金 自由体积 同步辐射     

Structural relaxation of Zr_(41)Ti_(14)Cu_(12.5)Ni_(10)Be_(22.5) bulk metallic glass under high pressure

Zr41Ti14Cu12.5Ni10Be22.5bulk metallic glass (BMG) is annealed at 573 K under 3 GPaand its structural relaxation is investigated by X-ray diffraction, ultrasonic study, compression as well as sliding wear measurements. It is found that after the ZrTiCuNiBe BMG sample was annealed under high pressure, the mechanical properties were improved. Moreover, the BMG with relaxed structure exhibits markedly different acoustic properties. These results are attributed to the fact that relaxation under high-pressure results in a microstructural transformation in the BMG.     

In situ X-ray diffraction investigation of compression behavior in Gd40Y16Al24Co20 bulk metallic glass under high pressure with synchrotron radiation

The compression behavior of the heavy RE-based BMC Gd40Y16Al24Co20 under high pressure has been investigated by in situ high pressure angle dispersive X-ray diffraction measurements using synchrotron radiation in the pressure range of 0-33.42 GPa at room temperature. By fitting the static equation of state at room temperature, we find the value of bulk modulus B is 61.27±4 GPa which is in good agreement with the experimental study by pulse-echo techniques of 58 GPa. The results show that the amorphous structure in the heavy RE-based BMG Gd40Y16Al24Co20 keeps quite stable up to 33.42 GPa although its compressibility is as large as about 33%. The coexistence of normal local structure similar to that of other BMGs and covalent bond structure similar to those of oxide glasses may be the reason for the anomalous property under high pressure of the Gd4oY16Al24Co2o BMG.     

利用ＳＢＡ-１５介孔内纳米碳合成含介孔的ＺＳＭ-５分子筛

SBA-15介孔分子筛内填充蔗糖并炭化后, 分别在碱性和弱酸性条件下, 用含铝源及TPABr的溶液浸渍,将SBA-15分子筛孔壁的无定形结构转化成ZSM-5分子筛的晶体结构, 除碳后得到含介孔的ZSM-5分子筛. 用X射线衍射、 N_2吸附-脱附、 ~(27)Al MAS NMR、 NH_3-TPD、 TEM、 SEM等对样品进行了表征, 考察了晶化时间等参数对样品的影响. 结果表明, 碱性条件下合成的ZSM-5分子筛晶体中含有少量孔径约3.2～4.2 nm的介孔孔道, 其酸强度接近与常规ZSM-5分子筛的酸强度;弱酸性条件下合成的ZSM-5分子筛晶体中含有大量孔径约1.4～1.6 nm的孔道, 其酸强度明显低于常规ZSM-5分子筛的酸强度.