重量吸附-红外光谱法测定催化剂固体表面酸性

以吡啶为吸附剂,采用石英弹簧重量吸附-红外光谱法测定催化剂及载体的表面酸性,研究了SiO2-Al2O3表面酸性、HY沸石的酸量与脱附温度的关系、加氢处理催化剂担体的红外酸,结果表明,石英弹簧重量吸附法适用于氧化铝、硅铝及分子筛等催化材料酸性的定量测量。     

膨润土催化剂表面酸度与催化活性的研究

本文探索了膨润土的主要成份和酸处理浓度与催化剂表面酸度的关系,以及表面酸度对催化活性的影响。成功地采用低浓度酸处理高铝膨润土催化剂,使妥尔油脂酸聚合,获取高转化率和高选择性的二聚酸。     

催化剂载体孔容积的快速测定法

通常测定颗粒状催化剂载体样品的孔容，是使用压汞仪法、氮气吸附法、四氯化碳与十六烷的混合溶液吸附法来测定。借鉴了测定涂料样品吸收值的方法，并稍加改动，通过简单的计算，得出样品孔容积，该法测试时间短、费用低、具有较高的分析准确度，并且适用于具有一定粒度和孔结构催化剂载体的孔容分析。     

热重法分析HZSM－5分子筛催化剂的表面酸性

本文利用岛津ＤＴ－４０热分析仪和自制的气体净化系统，采用吡啶为吸附质，对工业用的ＨＺＳＭ－５分子筛催化剂、ＨＺＳＭ－５原粉及γ－Ａｌ２Ｏ３进行了酸性测定、以脱附吡啶的量来表征样品的酸性强度，定义低温下脱附的为弱酸中心，高温下脱附的为强酸中心，根据总的脱附碱量计算出催化剂的总酸量．     

活性炭吸附法脱除双酚A反应液中残留催化剂

采用活性炭吸附法脱除双酚A反应液中的残留催化剂,用丙酮对活性炭进行再生。考察了活性炭的粒径、吸附温度、空速等对双酚A反应液中残留催化剂脱除效果的影响。结果表明,最佳操作条件为:10～20目活性炭,床层体积5 cm3,吸附温度65℃,空速1.0 h-1。在此条件下,对酸度为0.014 mmol/L的双酚A反应液进行了连续脱除残留催化剂处理,双酚A反应液的酸度能符合要求(≤0.001 mmol/L)。该方法具有不引入碱性杂质、不影响产品质量、操作简单的优点。     

热重法分折HZSM-5分子筛催化剂的表面酸性

本文利用岛津DT-40热分析仪和自制的气体净化系统,采用吡啶为吸附质,对工业用的HZSM-5分子筛催化剂、HZSM-5原粉及γ-Al₂O₃进行了酸性测定,以脱附吡啶的量来表征样品的酸性强度,定义低温下脱附的为弱酸中心,高温下脱附的为强酸中心,根据总的脱附碱量计算出催化剂的总酸量。     

固体催化剂表面酸度测定方法的改进

前言据有关文献介绍,在石油催化裂化以及其他一些反应中,例如异构化,歧化,氢转移,芳构化等,催化剂的活性与表面酸性有着密切的关系。分子筛、丝光沸石、Al_2O_3、SiO_2-A1_2O_3等是石油化学工业中重要的催化剂和催化剂载体,由于这些催化剂表面存在布郎斯台(Bronsted)酸和路易斯(Lewis)酸,     

褐煤添加催化剂快速热解制取颗粒活性炭的研究

以某种褐煤为原料,添加钾、铁催化剂,在高温水蒸气介质下,采用落下床辐射炉快速热解工艺,可以高效率地制造浸提活性炭。详细地考察了催化剂种类,催化剂添加量以及热解温度对活性炭吸附性能的影响。研究结果表明,在水蒸气介质存在下,褐煤添加催化剂快速热解是制取性能优良颗粒活性炭的一条途径,制得的活性炭不需要再活化,其表面积及吸附性能接近或超过某些商品活性炭。     

三聚氯氰催化剂中硫含量的测定

探讨了用重量法准确测定三聚氯氰催化剂中的硫 ,该法的最大标准偏差为 0 .0 14 ,最大相对标准偏差为 3 .5 4% ,回收率 99.9% ,可满足三聚氯氰催化剂中硫 (w <1% )测定精度要求。     

加氢裂化催化剂的基本组成和性质

随着世界燃油规范Ⅳ类标准的实施,以及对化工原料需求的增长,加氢裂化催化剂引起了更广泛的重视。介绍加氢裂化催化剂的基本组成和性质,深入剖析各组分对加氢裂化催化剂反应性能的影响。     

Comparison of the Methods for the Determination of Surface Acidity of Solid Catalysts

The concept of surface acidity was originally introduced with the aim of justifying the presence of some substances formed in catalytic chemical reactions, not as a consequence of suppositions about the nature of surface-active sites of solid catalysts. The formation of such substances in some reactions (e.g., cracking, isomerization, or polymerization) can be better explained by admitting the formation of reaction intermediates having the structure of a carbonium ion, which can be formed by interaction between the reacting substance (hydrocarbon) and an acid center. As an example, in the cracking of alkylaromatics catalyzed by decationated zeolites, the following reaction mechanism is generally accepted:     

Characterization of Acidity and Porosity of Zeolite Catalysts by the Equilibrated Thermodesorption of n-Hexane and n-Nonane

Thermodesorption of n-hexane and n-nonane from the acidic and non-acidic zeolites ZSM-5 and Y was studied by means of the thermogravimetric temperature programmed equilibrated desorption (TPED) and quasi-equilibrated temperature programmed desorption and adsorption (QE-TPDA). Micropore volumes determined from the adsorption capacity of n-hexane were close to those determined by N₂ adsorption. Content and strength of acid sites in the acidic zeolites estimated by fitting the Arrhenius equation to the high temperature parts of QE-TPDA profiles of n-hexane attributed to its cracking were in agreement with their acidity characteristics obtained by IR spectroscopy of chemisorbed pyridine. The mesopore volume was determined from the QE-TPDA profiles of n-nonane. Coking observed only for QE-TPDA of n-nonane on H-USY zeolite resulted in blocking the micropores without affecting the mesopores.     

Development of the Acidity of Zirconia-Supported Niobia Catalysts

A series of NbO _x /ZrO₂ catalysts containing up to 2.67wt Nb (ca. 80 nominal surface coverage) was prepared by incipient wetness impregnation from niobium oxalate and oxalic acid solution. The structure of the catalysts was monitored by X-ray diffraction and Raman spectroscopy. The results indicated the presence of a surface Nb phase. No evidence for the formation of crystalline Nb₂O₅ species was found. The development of the acidity as a function of Nb loading was monitored by adsorption of a basic probe molecule followed by infrared spectroscopy. The results indicated the appearance of Brnsted acid sites for a threshold of Nb loading. The abundance of Brnsted acid sites correlated well with the isopropanol dehydration activity. The overall behavior was very similar to that reported earlier for the WO _x /ZrO₂ system.     

The Acidity of Zeolites: Concepts,Measurements and Relation to Catalysis: A Review on Experimental and Theoretical Methods for the Study of Zeolite Acidity

In this article, we considered all aspects of acidity (nature of acid sites, strength, density, etc.) in solid catalysts and in zeolites in particular. After reminding the definition of acidity in liquid and solid acids, we emphasized acidity characterization by the most used physical techniques, such as Hammett's indicator titration, microcalorimetry of adsorbed probe molecules (ammonia, pyridine or other amines for acidity characterization and CO₂ or SO₂ for basicity characterization), ammonia or any amine thermodesorption, IR spectroscopy of hydroxyl groups and of several probe molecules adsorbed (ammonia, pyridine, piperidine, amines, CO, H₂, etc.), MAS-NMR of ²⁷Al, ²⁹Si, ¹H elements and of ¹H, ¹³C, ³¹P, etc. of adsorbed probe molecules, and model catalytic reactions.

Modeling the way the acid features of zeolites influence the catalytic activity of these catalysts toward acid-catalyzed reactions (relation between ammonia desorption activation energy values and catalytic activities, reaction mechanism, and kinetics) completes the general analysis of acidity and zeolite chemistry.     

Acidity of heteropoly compounds from XPS measurements

The changes in the partial charges on oxygens in the various heteropoly salts as a result of the acidity differences have been exploited for probing the oxygen 1s and W 4f lines. The gradation of the acidity thus obtained is compared to that of the conventional method.     

用氮气吸附法研究二甲醚催化剂表面分形维数

在77K下对四种二甲醚催化剂进行N2吸附—脱附等温线测定,得到了催化剂的孔结构参数,研究了其孔径分布、比表面积、等温线形态变化,并利用等温吸附数据计算其分形维数。结果表明,四种催化剂分形维数在2～3之间,将催化剂颗粒机械成型得到的片剂都具有分形特性,但其分形维数与比表面积和孔容积没有直接联系。     

催化剂酸性对正辛烷异构化反应行为研究

以正辛烷作为反应模型化合物,在连续微型反应器上考察了经稀土元素改性的LKZ-1分子筛的临氢异构化性能,并探讨了不同稀土含量对其表面酸性的影响,试验结果表明：稀土元素的引入使分子筛表面的B酸减少,L酸增加,异构化选择性提高,并且当稀土元素含量在2％时,中强酸分布最高,并且单甲基支链异构体含量也最高。     

催化裂化、催化裂解催化剂中金属元素含量的测定

用电感耦合等离子(ICP)发射光谱法,快速同时测定催化裂化、催化裂解催化剂中的微量铁、镍、铜、钒、钠、锑等金属元素含量,通过谱线选择、分析条件优化等措施有效避免了各种干扰。各元素的相对标准偏差(RSD)分别为铁0.41%、镍0.94%、铜6.36%、钒0.98%、钠0.31%、锑1.21%,加标回收率均大于91%,方法准确可靠。     

非晶态合金催化剂的研究进展

介绍了非晶态合金用作催化材料的研究成果,比较了几个研究阶段的特点。负载型非晶态合金有可能成为一种新型的工业用催化剂。