Synthesis and characterization of MCM-41-supported nano zirconia catalysts

Series of MCM-41 supported sulfated Zirconia (SZ) catalysts with different loadings (2.5–7.5% wt.) were prepared using direct impregnation method. The acquired solid catalysts were characterized structurally and chemically using X-RD, HRTEM, BET, FT-IR, Raman spectroscopy and TPD analysis. The acidity of the solid catalysts was investigated through cumene cracking and isopropanol dehydration at different temperatures. As the SZ loading increases, the surface acidity of the mesoporous catalysts was enhanced, this was reflected by the higher catalytic activity toward cumene cracking and isopropanol dehydration.     

Synthesis and characterization of acidic properties of Al-SBA-15 materials with varying Si/Al ratios

Al-SBA-15 of varying Si/Al ratios in the range 11.4–78.4 was synthesized using tri-block copolymer P123. The calcined materials were examined by XRD, pore size distribution, surface area, ²⁷Al NMR spectroscopy. The acidity and acid strength distribution were studied using microcalorimetric adsorption of NH₃. The acidic properties were also examined by cumene cracking reaction as a function of Si/Al ratios. Systematic variation of acidity and activity was observed as a function of Si/Al ratio. The initial heats of NH₃ adsorption correlated well with activity indicate that acid sites with ΔH > 100 kJ/mole is responsible for cumene cracking activity. Linear correlations were obtained with total acidity and cumene cracking activities. The tetrahedral aluminum was found to be responsible for the observed acidities and catalytic activities.     

Comparing Al-SBA-15 Support and Pt/Al-SBA-15 Catalyst: Changes in Al Speciation and Acidic Properties Induced by the Introduction of Pt via Aqueous Medium

Differences between the acidic properties of silicoaluminic Pt-containing catalysts and those assessed on their parent supports have been reported in the literature and attributed to the presence of the metal nanoparticles and to their influence on the acid sites. It is shown here that for mesoporous materials containing various types of Al species, an alternative explanation can be proposed. ²⁷Al NMR spectroscopy, FTIR of adsorbed CO and probe catalytic tests suggest the redistribution of aluminium atoms upon contact of the parent support with the aqueous solution containing the Pt precursor. Upon contact with water and thermal treatment, strong and mild Brønsted sites (Si–O(H)–Al) transform into strong Lewis sites (isolated tetracoordinated Al atoms). As a consequence, it may not be straightforward to deduce the acidic properties of metal-containing catalysts supported on Al-containing mesoporous materials from those of the bare support, because the surface species may differ significantly.     

高分子负载金属卟啉化合物催化氧化异丙苯的动力学研究

高分子负载的金属卟啉化合物．对异丙苯催化氧化效果显著。产物有过氧化氢异丙苯、二甲基苄醇、甲基苯乙烯、苯乙酮等。在80℃、101．3kPa的氧压下，催化剂还可催化分解过氧化氢异丙苯。在异丙苯转化率小于40%时，过氧化氢异丙苯和二甲基苄醇的总收率大于95%。研究了高分子负载铜卟啉化合物在异丙苯氧化中的动力学，发现催化氧化的初速率对异丙苯和氧气均为一级，即T0=kC cumene Po2；活化能为51．69kJ／mol；提出了包括氧活化的可能机理。     

甲苯-苯甲酸法与异丙苯法制苯酚方案比较

工业生产苯酚主要采用异丙苯法和甲苯氧化法。从生产工艺、流程、能耗物耗、投资几方面对生产苯酚的甲苯-苯甲酸法和异丙苯法两种方案进行比较。     

Cumene Hydroperoxide Hydrogenation on a Pd/Al2O3 Catalyst in a Trickle Bed Reactor – Kinetics of Hydrogenation and Deactivation

Liquid‐phase hydrogenation using a Pd/Al₂O₃ catalyst provides a potential technique for the reduction of cumene hydroperoxide (CHP) to α‐cumyl alcohol (CA). In this paper, CHP hydrogenation was carried out in a cocurrent downflow trickle‐bed reactor over a wide range of reaction conditions to study the reaction and deactivation kinetics. The proposed intrinsic rate expression for CHP hydrogenation is based on an Eley‐Rideal mechanism that accounts for an irreversible surface reaction between the absorbed CHP with nonabsorbed hydrogen molecules. During CHP hydrogenation, an exponential decay in activity of the Pd/Al₂O₃ catalyst and the presence of residual activity were observed. A kinetic deactivation model with residual activity was developed. Based on reaction and deactivation kinetics, catalyst deactivation was attributed to oxidation of the catalyst surface by CHP. The presence of residual activity was due to the partial reduction of oxidized catalyst surface by hydrogen.     

Synthesis of a Ceramic Acid of Tungstated Alumina more Active than Silica-alumina for Decompositions of Cumene, Ethylbenzene, and Toluene

A ceramics acid, calcined at temperatures above 1000 °C, was obtained by impregnating aluminum hydroxide with aqueous ammonium metatungstate followed by calcining in air at 1000–1200 °C (1–5 wt% W); its acidity and catalytic activity for decompositions of toluene, ethylbenzene, and cumene are higher than those of silica-alumina.     

Characterization of Supported NiSO4 and Effect of TiO2–ZrO2 Composition on Catalytic Activity for Acid Catalysis

A series of catalysts, NiSO₄/TiO₂–ZrO₂ having different TiO₂–ZrO₂ composition, for acid catalysis was prepared by the impregnation method using an aqueous solution of nickel sulfate. The addition of TiO₂ to ZrO₂ improved the surface area of the catalyst and enhanced its acidity remarkably because of the formation of new acid sites through the charge imbalance of Ti–O–Zr bonding. The binary oxide, TiO₂–ZrO₂ calcined above 600 °C resulted in the formation of crystalline orthorhombic phase of ZrTiO₄. Therefore, NiSO₄/TiO₂–ZrO₂ calcined at 500 °C exhibited a maximum catalytic activity for acid catalysis, and then the catalytic activity decreased with the calcination temperature. The correlation between catalytic activity and acidity held for both reaction, 2-propanol dehydration and cumene dealkylation. NiSO₄ supported on 50TiO₂–50ZrO₂ (TiO₂/ZrO₂ ratio = 1) among TiO₂–ZrO₂ binary oxides exhibited the highest catalytic activity for acid catalysis.     

Characterization of zirconium sulfate supported on TiO2 and activity for acid catalysis

A series of Zr(SO₄)₂/TiO₂ catalysts were prepared by impregnation of powder TiO₂ with an aqueous solution of zirconium sulfate. No diffraction line of zirconium sulfate was observed up to 30 wt%, indicating good dispersion of Zr(SO₄)₂ on the surface of TiO₂. The high catalytic activities of Zr(SO₄)2/TiO₂ for both 2-propanol dehydration and cumene dealkylation were related to the increase of acidity and acid strength due to the addition of Zr(SO₄)₂. Zr(SO₄)₂/TiO₂ containing 25% zirconium sulfate and calcined at 400 °C exhibited maximum catalytic activities for 2-propanol dehydration and cumene dealkylation. The catalytic activities for these reactions were correlated with the acidity of catalysts measured by the ammonia chemisorption method. This paper is dedicated to Professor Hyun Ku Rhee on the occasion of his retirement from Seoul National University.     

Acidic Montmorillonite/Cordierite Monolithic Catalysts for Cleavage of Cumene Hydroperoxide

In this work, a series of acidic montmorillonite/cordierite monolithic catalysts were prepared by a coating method using silica sol as the binder. The morphology and structure of the acidic montmoril o...