表征固体超强酸性的新方法-正丁烷异构化反应的原位~(13)CMASNMR谱

室温下SO_4~(2-)/ZrO_2催化剂（SZ）上~(13)C标记的丁烷异构化反应的原位 ~(13)C MAS NMR谱研究结果表明：其反应动力学符合Langmuir-Hinshelwood一级可 逆表面反应动力学公式，由该动力学公式计算得到的反应速率常数可以用于衡量固 体催化剂的表面超强酸性。这种新的表征方法显示采用一步-醇热-超临界干燥综合 技术合成的SZ催化剂不仅比表面和硫酸根含量高，而且其超强酸性和异构化反应活 性均明显优于常规法合成的催化剂，具有良好的应用前景。     

丝光沸石负载SO~4^2^-/ZrO~2超强酸的研究

制备了一系列丝光沸石(HM)负载SO~4^2^-/ZrO~2(SZ)超强酸催化剂,并研究了它们比表面、孔容、硫含量及超强酸性的变化规律。结果发现,HM在负载SZ后超强酸性显著提高,可以在35℃条件下催化正丁烷异构化反应。吡啶吸附红外结果表明,适量负载SZ可增加HM的Lewis酸量和总酸量,从而使甲苯岐化和邻二甲苯异构化反应等酸催化反应活性显著提高。XRD结果证实,在HM上负载适量SZ不会破坏HM的结构,但负载量过大(>60%,质量分数)则会引起沸石结构的塌毁。     

SO2-4/ZrO2的相结构和超强酸性及其对丁烷异构化反应的催化活性

通过沉淀、回流和掺杂等方法制备了ZrO2呈四方相及单斜相的SO2-4/ZrO2(SZ),并用XRD,TEM,低温N2-BET和吡啶吸附IR等技术定量地测定和探讨了SZ的结构特征和表面超强酸性及其对丁烷异构化反应的催化活性. 结果表明,ZrO2呈单斜相结构的SZ表面Brnsted(B)酸与Lewis(L)酸的浓度比[B]/[L]较ZrO2以四方相为主的SZ高约40%,但其对丁烷异构化反应的比催化活性则较后者低约31%;由掺Mg2+所制备的ZrO2呈四方相的SMZ具有与ZrO2呈纯单斜相的SZ非常接近的[B]/[L]比,且表现出比未掺Mg2+的ZrO2以四方相为主的SZ更高的比催化活性. 从催化剂晶相结构对表面B酸浓度及强度影响的角度进行了讨论.     

用常温正丁烷异构化反应表征固体超强酸性

研究了室温下固体超强酸催化剂上正丁烷反应，发现转化率低于50％时，异构化选择性高于95％，正丁烷异构化反应动力学符合一级可逆反应规律，固体超强酸的酸强度与正丁烷异构化反应转化率和速率常数呈顺变关系，与反应表现活化能呈逆变关系．报出了一种新的表征固体超强酸性的实验方法．     

硫酸化氧化锆固体超强酸

硫酸化氧化锆(SZ)是一种固体超强酸催化剂,它能高效催化异构化、烷化、酰化、环化、裂解、酯化和酯交换等多种类型的催化反应。1979年,日本科学家Hino和Arata发现SZ能在室温催化丁烷异构化反应,首次提出了SZ是一种酸性比100%浓硫酸还强一万倍的固体超强酸,从而引起了科学家们对SZ研究的浓厚兴趣。经过了三十多年发展,研究者们在SZ的合成、改性、表征和应用等方面取得了许多新的研究成果。本文综述了SZ几十年来的研究进展,内容主要包括SZ的合成方法,表面结构和酸性机理,研究者们对SZ性质的不同看法,SZ的改性及应用。     

SO4^2—／ZrO2的相结构和超强酸性及其对丁烷异构化反应的催化活性

通过沉淀、回流和掺杂等方法制备了ZrO2呈四方相及单斜相的SO4^2-／ZrO2（SZ），并用XRD，TEM，低温N2－BET和吡啶吸附IR等技术定量测量地测定和探讨了SZ的结构特征和表面超强酸性及其对丁烷异构化反应的催化活性，结果表明，ZrO2呈单斜相结构的SZ表面Broensted（B）酸与Lewis（L）酸的浓度比[B]/[L]较ZrO2以四方相为主的SZ高约40％，但其对丁烷异构化反应的比催化活性则较后者低约31％，由掺Mg^2 所制备的ZrO2呈四方相的SMZ具有与ZrO2呈纯单斜相的SZ非常接近的[B]/[L]比，且表现出比末掺Mg^2 的ZrO2以四方相为主的SZ更高的比催化活性，从催化剂晶结构对表面B酸浓度及强度影响的角度进行了讨论。     

低碳烷烃催化反应机理的固体核磁共振研究

结合实验研究,介绍了13C原位固体核磁共振技术及其在催化反应机理研究中的应用,主要工作包括温和条件下丙烷在镓改性H-ZSM-5上的活化研究,SO2-4/ZrO2、CsxH3-xPW12O40和H-MOR催化剂上正丁烷的异构化反应机理研究,以及利用原位13C MAS NMR测定催化剂超强酸性.     

正戊烷异构化反应表征固体超强酸性

详细研究了低温下固体酸催化剂上的正戊烷反应，发现在ＳＯ４＾２－／ＭｘＯｙ型固体超强酸，ＨＭ和ＨＺＳＭ－５沸石表面上正戊烷反应以异构化为主，其反应动力学符合一级可逆反应规律，催化剂的酸强度与正戊烷异构化反应速率常数呈顺变关系，由此提出了一种适合于－１６＜Ｈ０＜－１２的固体酸强度测定方法，解决了该区域内有色样品或高温易分解样品在酸性测量上的难题。     

γ-Al_2O_3负载Cr促进SO_4~(-2)/ZrO_2固体超强酸研究

将 Cr促进的 SO2 - 4 /Zr O2 ( SZ)固体超强酸 Cr-SZ负载于 γ-Al2 O3载体上 ,制成 Cr-SZ/Al2 O3系列固体超强酸 ,利用探针反应考察了其超强酸性、中强酸性和弱酸性的变化情况 .详细研究了样品的比表面、硫含量、 Zr O2 晶化情况及正丁烷低温异构化反应活性 .结果发现 ,负载后部分 Cr-SZ的正丁烷低温异构化反应活性显著提高 .含铬样品酸强度和脱氢性能的增强对其正丁烷异构化反应活性的提高均有贡献 .样品酸性和脱氢性之间的合适匹配使 Cr-SZ/Al2 O3显示出很高的正丁烷异构化反应活性 .     

S2O2-8和SO2-4促进ZrO2固体超强酸正戊烷反应性能差异的研究

考察了常温下S2O2-8促进ZrO2(PSZ)固体超强酸催化剂上正戊烷的反应性能,并与SO2-4促进ZrO2(SZ)反应相比较,观察到PSZ和SZ对正戊烷都具有异构化和裂解的双重作用,主要产物分别为异戊烷和异丁烷.正戊烷的异构化转化率和表观反应速率常数主要取决于样品的焙烧温度.但对于正戊烷异构化反应,PSZ的最佳焙烧温度为550℃,比SZ的低50℃.在各自的最佳焙烧温度下反应1h后,前者的异戊烷生成率为后者的1.3倍.通过S含量和比表面积测定以及用XRD和FTIR等手段分析了PSZ的物理化学特性.从原位FTIR谱图发现,PSZ(550℃)表面S-O键的红外吸收明显比SZ(600℃)的强;通过吡啶红外手段发现PSZ(550℃)吡啶离子吸收峰的红移大于SZ(600℃),表明前者的Lewis酸强于后者.     

Butane isomerization over platinum promoted sulfated zirconia catalysts

The isomerization of n-butane to i-butane has been studied at 11 bar in a microflow reactor over sulfated zirconia (SZ) and platinum containing sulfated zirconia (Pt-SZ) catalysts. In the presence of H₂ a significantly higher temperature is required for isomerization over SZ than in its absence. The rate over SZ is higher with n-butane containing 33 ppm butene as an impurity than with a feed that is pre-equilibrated over a Pt/SiO₂ catalyst to a much lower butene content. Over Pt-SZ the reaction rate is higher, because any butene consumed is rapidly regenerated; the conversion is perfectly stable in 83 h runs, selectivity to i-butane is 95%; i-pentane and propane are the main byproducts. The activation energy is 53 kJ mol⁻¹. Upon increasing the pressure of H₂ from 1.1 to 6.6 bar, the reaction rate was found to decrease in a perfectly reversible fashion. Kinetic analysis reveals that the reaction order is negative in H₂ (−1.1 to −1.3 depending on the temperature) and positive in n-butane (+ 1.3 to +1.6), indicating that the mechanism of this isomerization is intermolecular: butene is formed and reacts with adsorbed C₄-carbenium ions to adsorbed C₈ intermediates which isomerize and undergo β-fission to fragments with i-C₄ structure. This mechanism is confirmed over Pt-SZ by isotopic labelling experiments, though at much lower pressure, using double labelled ¹³CH₃---CH₂---CH₂---¹³CH₃. The primary reaction product consists of i-butane molecules, containing zero, one, two, three and four ¹³C atoms in a binomial distribution.     

Supercritical <Emphasis Type="Italic">n</Emphasis>-butane isomerization

Supercritical n-butane isomerization over the solid acid catalysts sulfated zirconia, TiO₂-supported H₄[Si(W₃O₁₀)₄] · xH₂O (Keggin-type heteropoly acid), and H-mordenite is studied in a flow reactor. The critical parameters of n-butane are calculated for a wide range of reaction conditions. Changing from gaseous n-butane to supercritical n-butane markedly extends the lifetime of the catalysts. Under supercritical conditions, the activity and selectivity of the catalysts are invariable, provided that the density of the reaction mixture is in the vicinity of the critical density of n-butane. After the catalysts are deactivated in the gas medium, they can be partially or completely reactivated in the supercritical fluid.Translated from Kinetika i Kataliz, Vol. 45, No. 6, 2004, pp. 942–946.Original Russian Text Copyright © 2004 by Bogdan, Klimenko, Kustov, Kazanskii.     

On the Effect of the Strength of Acid Sites in Heterogeneous Catalysts on the Activity in the Skeletal Isomerization of n-Butane

The catalytic activity of three groups of acid catalysts different in the nature and strength of acid sites in the skeletal isomerization of n-butane was studied. It was found that the strength of the sites did not correlate with the rate of the reaction.     

A Novel Way to Prepare γ-Al2O3 Supported SO42-/ZrO2 Solid Superacid Catalysts for n-Butane Isomerization

Highly active solid superacid catalysts for n-butane isomerization, SZ/Al2O3-P, were prepared by supporting SO42-/ZrO2 (SZ) on γ-Al2O3 carrier using a precipitation method.The activities of some catalysts were enhanced significantly.The activity of the most active sample, 60%SZ/Al2O3-P, was even about 2 times more active than that of the SZ catalyst.     

Superacid polymers from sulfonated poly(styrene-divinylbenzene): Preparation and characterization

Superacid polymers were prepared by bringing metal halides (AlCl₃, SnCl₄, TiCl₄, BF₃, or SbF₅) in contact with macroporous sulfonic acid resins [sulfonated, crosslinked poly(styrene-divinylbenzene)]. The resulting solids were characterized by chemical analysis, temperature-programmed desorption, transmission electron microscopy, and X-ray photoelectron spectroscopy. They were also tested as catalysts for n-butane isomerization at 0.5 bar and 60 to 120°C. The polymers consist of supported metal oxyhalide particles, complexes of metal oxyhalides and sulfonate groups, and the remaining unreacted sulfonic acid groups. In the presence of HCl, these polymers were highly active catalysts for the butane isomerization reaction, the activity being a consequence of a high proton-donor strength inferred to be associated with H₂Cl⁺ groups stabilized on the polymer surface by negative charge delocalization over sulfonate–metal oxyhalide sulfonate groups.