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通过对丙烷在负载型金属催化剂 上临氢脱氢反应性能的考察,发现除 负载 型Pt、Pd等具有脱氢活性外;负载型Cu 也同样具 有脱氢活性,并且随Cu载量增加而升高。对催化剂稳定性研究结果表明,载体与金属组分间相互作用是不容忽视的因素之一。催化剂选择性影响 因素主要是加氢裂化或氢解反应。因此,对催化剂脱氢选择性的改善既可通过调变金属组分的脱氢加氢性能,也可通过改变载体酸性进行。 相似文献
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噻吩在不同负载磷化钨催化剂上的加氢脱硫 总被引:3,自引:0,他引:3
采用程序升温和高纯氢气还原无定型磷钨酸盐与载体γ-Al2O3机械混合物的方法,制备了活性组分为磷化钨、负载量分别为20%、25%、30%和35%的新型磷化钨催化剂,并对其噻吩加氢脱硫反应活性进行考察。实验结果表明,负载磷化钨催化剂的噻吩加氢脱硫率明显高于非负载磷化钨催化剂;不同负载磷化钨催化剂还原反应均为放热反应,且发生还原反应生成活性组分磷化钨的最低温度大于610℃,对于噻吩加氢脱硫反应,WP1活性较高,WP4活性较低,在340℃时分别为85.23%和67.93%,催化剂WP1具有较好的稳定性。 相似文献
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采用浸渍法制备负载型磷钼杂多酸催化剂,分析了催化剂的比表面积、分散性、结构特征、稳定性以及再生温度等性质.通过固定床微反应器考察杂多酸催化剂催化氧化糠醛生成顺丁烯二酸酐的催化性能.研究了焙烧温度、负载量对催化剂性能的影响,以及反应温度对顺丁烯二酸酐收率的影响.结果表明:通过浸渍制备的杂多酸催化剂具有杂多酸催化剂的Keggin结构,具有较好的稳定性和酸性;活性组分能较好的分布于载体SiO2上;催化剂的再生温度和活化温度均为400℃;在钼磷原子比为0.85,负载量为48.6%时催化性能较好,催化剂的表面酸量为0.646 mmol/g;反应温度控制在365℃附近时,顺丁烯二酸酐收率可达到57.2%,选择性为62.7%. 相似文献
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采用2种方法制备了原位负载稀土三元催化剂,即先将均相的Y(CCl3OO)3-Glycerin体系负载在载体上,后逐滴加入ZnEt2(标记为Y(CCl3OO)3-Glycerin/γ-Al2O3/ZnEt2);或先将ZnEt2与载体反应,再与均相的Y(CCl3OO)3-Glycerin体系反应(标记为ZnEt2/γ-Al2O3/Y(CCl3OO)3-Glycerin).研究发现原位负载催化剂催化环氧丙烷和二氧化碳共聚合反应的活性比未负载前低24%~36%,通过分析催化剂制备过程中所生成的乙烷量的变化,证明原位负载时催化剂组分如Y(CCl3OO)3、Glycerin或ZnEt2发生了向载体孔隙内的扩散渗透,使得催化剂各组分配比与未负载催化剂相比发生了偏差,从而降低了催化活性;另一方面,表面羟基与ZnEt2反应形成了低效率的活性种,也是原位负载催化剂活性不高的原因之一.提出了影响原位负载稀土三元催化剂活性的2个主要因素,即活性种的反应活性和活性种的数量.通过调节催化剂组分配比、负载化阶段的振荡研磨时间、原位负载时的活性种状态、载体的表面状态等,可使负载催化剂的活性比未负载的稀土三元催化剂提高3.5%. 相似文献
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二氧化硅负载杂多酸对异丁烷与丁烯烷基化的催化作用Ⅰ.催化剂的制备、表征和失活 总被引:12,自引:0,他引:12
采用浸渍法制备了二氧化硅负载的磷钨酸催化剂,系统考察了催化剂的比表面积、结晶水、结构特征和酸性等物化性质. 将在不同条件下制备的不同结构的杂多酸催化剂用于异丁烷与丁烯烷基化反应,考察了催化剂活性组分、制备方法和反应条件对催化剂性能的影响,分析了催化剂的失活过程和失活机理. 结果表明,当负载量不大于50%时,磷钨酸以单分子层形式均匀分散于载体表面,催化剂表面存在大量的强B酸中心,不存在L酸中心; 经160 ℃活化后的催化剂具有最大的酸量和最强的酸性; 催化剂对烷基化反应具有较高的初活性,但随着反应的进行催化剂迅速失活; 反应产物的组成与催化剂失活程度密切相关,反应初期产物以烷烃为主,之后产物则以烯烃为主; 催化剂的失活原因为积碳. 相似文献
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The spectral-polarization characteristics of absorption and phosphorescence of molecules of the initial form of nitro-substituted
indolinospirobenzothiopyran were studied in oriented polyethylene films and in solutions with different polarity. An oscillator
model of the electron transitions responsible for the formation of absorption and luminescence spectra was suggested. It was
established that the principal differences in the spectral and photophysical properties of the compound studied and its oxygen-containing
analog are associated with the fact that the electronegativity of the S atom is lower than that of the O atom.
Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1143–1146, June, 1997. 相似文献
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Cotton cellulose was swollen in a sodium hydroxide solution and carboxymethylated by a two-bath method for different periods of time for each process. The kinetics of acid hydrolysis and the crystallinity of the swollen and carboxymethylated samples were measured. The proportion of broken bonds, rate constants for hydrolysis, and permeability of cellulose to hydrolyzing agents were calculated. The susceptibility of glycosidic linkages to acid hydrolysis was improved by carboxymethylation more than by swelling in alkali. The increased accessibility of carboxymethylcellulose to acid was regarded as a consequence of increased intra-and intercrystalline swelling and of the glycosidic bonds' weakness caused by the electron-attracting carboxymethyl group on the C-6 position. 相似文献
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面对日益枯竭的能源危机,氢能是一种洁净、最有前景的替代能源。目前在各种制氢的方法中光催化分解水制氢的研究最多,光解水过程中催化剂最关键,本文对利用太阳能光解水的途径、提高光催化反应效率以及光催化剂的开发研究进行了综述。 相似文献
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The aim of the presented work was the investigation of thermal oxidation of ilmenite in static air atmosphere. The investigations
were carried out by use of a derivatograph (MOM, Hungary). The changes of crystallographic structure of investigated samples
were identified by X-ray diffractometry on Philips PW-1710 diffractometer. In temperature above 500°C appears structure of
hematite Fe2O3. On the basis of the thermogravimetric measurements, the contracting area and contracting volume models were found as the
best fitting experimental data.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
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Cyclopropyl derivative of 2,6-di-tert-butylphenol is synthesized as a probe to investigate the mechanism of base-catalyzed autooxidation of phenol derivatives. Our study indicates that one electron reduction of molecular oxygen from phenolate gives phenoxyl radical 3, a key intermediate of autooxidation. The coupling of phenoxyl radical and superoxide radical gives peroxylate anion 4 and produces the final epoxy alcohol adduct 6. 相似文献
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NiY分子筛表面酸性影响其选择性吸附脱硫性能的机理研究 《燃料化学学报》2016,44(9):1082-1088
采用原位红外光谱技术,以噻吩、环己烯和苯为模型探针分子,分别考察单一烃分子在NiY分子筛上的吸附与反应行为以及噻吩与烯烃、芳烃间的竞争吸附和催化反应行为。单一探针分子吸附研究发现,NiY分子筛中与Ni物种相关的Lewis(L)酸位是噻吩的选择性吸附活性位;噻吩和环己烯在NiY分子筛中Brnsted(B)酸位上发生的质子化和低聚反应明显弱于HY分子筛。双探针分子竞争吸附研究发现,环己烯二聚体在NiY中强B酸位上的强化学吸附与噻吩存在显著的竞争吸附行为。另外,苯和噻吩在NiY上的竞争吸附现象在373K时明显减弱。由此,在选择性吸附脱硫过程中,减少吸附剂表面B酸中心可降低烯烃对噻吩的竞争吸附,另外适当提高吸附体系的温度可以有效避免芳烃对噻吩的竞争吸附。 相似文献