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461.
本文采用不同的金属离子(Sn2+,Sn4+,Al3+,Ag+,Ni2+)和SO2-4浸渍ZrO(OH)2的方法制备了一系列金属改性的SO2-4/ZrO2的纳米固体超强酸。并通过指示剂法测定其酸强度,用IR、BET、XRD、TEM及化学分析等多种试验手段对催化剂进行表征,并通过正己烷裂解反应考察了该类固体超强酸催化剂的催化活性。结果发现:不同的金属离子掺杂制得的改性SO2-4/ZrO2催化剂具有不同的性能。Sn2+、Sn4+和Al3+掺杂的超强酸有较强的酸性,但只有Ni2+、Sn2+掺杂的SO2-4/ZrO2样品具有正己烷裂解反应活性,Ag+、Sn4+掺杂改性的SO2-4/ZrO2样品不具有正己烷裂解活性。 相似文献
462.
Adriana De Stefanis Giorgio Perez Anthony A.G. Tomlinson 《Reaction Kinetics and Catalysis Letters》2003,79(2):227-232
Reactions of primary aliphatic C2-C8 alcohols on alumina and iron-aluminium-oxides pillared montmorillonite and beidellite
indicate that dehydration reaction occurs on Lewis sites of pillars, while clays are responsible of cracking.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
463.
关于多个子空间的交空间 总被引:2,自引:2,他引:0
王新民 《数学的实践与认识》2002,32(5):855-859
关于多个子空间的交空间 ,到目前为止还没有一个行之有效的直接求法 .本文首先证明了关于分块矩阵的两个重要结果 ,由此得到了一个求多个子空间的交空间的直接方法——初等变换法 . 相似文献
464.
Attila Pintér Antal Tungler Lajos Nagy László Vida László Sebestyén Tivadar Gál József Kohán János Kerezsi 《Reaction Kinetics and Catalysis Letters》2006,88(1):175-181
Summary Steam cracking of several gasoline and gas oil samples was carried out under different conditions and the results are reported.
Some of sample feedstocks were previously cracked in a commercial plant so the laboratory and commercial results could be
compared. It was found that the laboratory reactor was more sensitive to the changes of the composition of the raw materials. 相似文献
465.
466.
467.
During whip cracking the whip-tip reaches a supersonic velocity for a period of about 1.2 ms, thereby emitting a head wave
with a parabolic-shaped geometry. A detailed study of this mechanism which encompasses the motion analysis of the whip-tip
as well as the determination of the local origin of the shock emission requires a sophisticated recording technique. A pre-trigger
framing high-speed video camera system was used which was triggered by an acoustical sensor and synchronized with a pulsed
copper-vapour laser. The phenomena were visualized by the direct shadowgraph method and recorded cinematographically as digital
images at a frame rate of 9 kHz using a CCD-matrix with pixels. The resulting series of frames allowed, for the first time, (i) a reconstruction of the whip-tip trajectory, (ii)
a determination of the tuft velocity and acceleration, (iii) a correlation of whip-tip kinematics with shock wave emission,
and (iv) a motion analysis of the turning and unfolding mechanism of the tuft. The tuft at the whip-tip was accelerated within
a distance of about 45 cm from a Mach number of to a maximum of , thereby reaching a maximum acceleration of 50,000 g. The shock is emitted at the moment when the cracker, arriving at the
turning point of the lash, is rapidly turned around. After emission of the shock wav within a short distance of only 20 cm.
Received 3 March 1997 / Accepted 21 July 1997 相似文献
468.
异质双材料粘接梁的界面端部应力及端部龟裂破坏的实验应力分析 总被引:1,自引:0,他引:1
本文采用了高灵敏度的云纹干涉法对异质双材料粘接梁在弯曲载荷作用下的位移进行了测量,用局部杂交法对界面端部区域的应变和应力进行了计算。通过对该区域内的实验应力分析发现:拉应力σx是影响结构强度的关键因素。本文还对在基体材料表面近角点区域可能出现的龟裂破坏的原因进行了分析。 相似文献
469.
To explore the possibility of using surface coating to reduce environmental stress cracking (ESC) of transparent polycarbonate (PC) parts, silicone coated and SiO2 coated PC were tested in a self-made three-point bending apparatus in the presence of ethanol. The variation of stress with time was recorded, and the surface cracking was observed to evaluate the ESC resistance of samples. Slower stress relaxation rates and fewer surface cracks indicated that silicone coating improved the ESC resistance of PC, but SiO2 coated PC was found to be no better than that of uncoated PC. Silicone coating reduced the absorption of ethanol in PC, weakening the surface plasticization, thus hindering the formation and development of cracks in PC. Nanoindentation test results showed that the mechanical properties such as hardness and elastic modulus of silicone coating are a better match for PC than SiO2 coating. This allows the silicone coating to have a favorable effect in providing continuous protection for PC under the combined action of ethanol and stress. 相似文献
470.
ZSM分子筛的合成及其在丁烯催化裂解反应中的应用 《燃料化学学报》2017,45(2):182-188
采用水热合成法制备了无模板剂ZSM-5分子筛并用正硅酸甲酯(TMOS)对其进行外表面修饰改性,利用XRD、SEM、~(29)Si MAS NMR、~(27)Al MAS NMR、NH_3-TPD、BET和UV-vis DRS对合成分子筛的物相、形貌和酸性等进行了表征,并将其应用于催化丁烯裂解反应。研究表明,经水热合成的无模板剂ZSM-5结晶度较好,与添加模板剂合成的ZSM-5拥有相似的孔道结构和晶体结构以及相近的酸量,但在酸中心分布上有明显差异:孔道内酸中心数量增加且分布更加均匀,孔道交叉处酸中心数量减少;经过外表面修饰改性后,ZSM-5分子筛外表面部分不具备择形性的酸中心被钝化,使其择形选择能力增强。在催化丁烯裂解反应中,用TMOS进行外表面修饰改性的无模板剂ZSM-5分子筛作为催化剂能够有效抑制副反应的发生,丙烯和乙烯的总收率高达58%。 相似文献