Total Oxidation of Chlorinated Hydrocarbons on A1–xSrxMnO3 Perovskite‐Type Oxide Catalysts – Part II: Catalytic Activity

The influence of the kind of A‐site cation in A_1–xSr_xMnO₃ perovskites (A = La, Pr, Nd, Di [didymium]) on the catalytic activity in the total oxidation of methane, chloromethane, dichloromethane, and trichloroethylene has been studied. In contrast to methane, the total oxidation of chlorinated hydrocarbons (CHC) is connected with a reversible catalyst deactivation and the formation of byproducts at low reaction temperatures. For the catalysts calcined at 600 and 800 °C, resp., the catalytic activity is determined mainly by specific surface area, amount of oxide admixtures and crystallinity of the perovskite. DiMnO₃ showed the highest and PrMnO₃ catalysts the lowest catalytic activity in the total oxidation of methane and CHC. Partial substitution of A by Sr leads to an enhancement of the catalytic activity in the total oxidation of methane, but not in the total oxidation of CHC.     

Total Oxidation of Chlorinated Hydrocarbons on A1–xSrxMnO3 Perovskite‐Type Oxide Catalysts – Part I: Catalyst Characterization

Thermoanalytical measurements (DTG‐DTA‐MS), X‐ray diffraction (XRD), temperature‐programmed reduction (TPR), redox titration and X‐ray photoelectron spectroscopy (XPS) were used to characterize A_1–xSr_xMnO₃ perovskite catalysts (A = La, Nd, Pr, Di [didymium]). The catalyst samples were investigated before and after interaction with chloromethane in the temperature range between 300 and 650 °C. XRD and TPR measurements revealed the presence of oxide admixtures in samples calcined at 600 and 800 °C, resp., in air. Crystallinity of the samples and the amount of oxide admixtures depend on the kind of A‐site cations. Interaction of the perovskite samples with chlorinated hydrocarbons at reaction temperatures leads to a decrease of the specific surface areas; the perovskite structure is preserved. Redox titration and TPR measurements showed that the Mn(IV) content in the perovskites increases by partial substitution of La by Sr and decreases after interaction with chloromethane.     

Continuous Gas‐Phase Hydroformylation of 1‐Butene using Supported Ionic Liquid Phase (SILP) Catalysts

The concept of supported ionic liquid phase (SILP) catalysis has been extended to 1‐butene hydroformylation. A rhodium‐sulfoxantphos complex was dissolved in [BMIM][n‐C₈H₁₇OSO₃] and this solution was highly dispersed on silica. Continuous gas‐phase experiments in a fixed‐bed reactor revealed these SILP catalysts to be highly active, selective and long‐term stable. Kinetic data have been acquired by variation of temperature, pressure, syngas composition, substrate and catalyst concentration. A linear dependency in rhodium concentration could be established over a large concentration range giving another excellent hint for truly homogeneous catalysis in the SILP system. Compared to former studies using propene, the SILP system showed significantly higher activity and selectivity with 1‐butene as feedstock. These findings could be elucidated by solubility measurements using a magnetic microbalance.     

丁烯烷基化固体酸催化剂的研究进展

阐述了异丁烷 丁烯烷基化催化剂的发展状况,主要涉及了几种新型固体酸催化剂,包括固体超强酸催化剂、分子筛催化剂和负载型杂多酸催化剂。文章着重对SO2-4 MxOy、MCM-41和负载型杂多酸催化剂的制备,活性和选择性作了探讨。同时指出了这些固体酸催化剂存在的问题,预测了烷基化催化剂研究的发展方向。     

Selective Catalytic Reduction of NOx with Ammonia over Fe‐Mo/ZSM‐5 Catalysts

The Fe‐Mo/ZSM‐5 catalysts were prepared by an impregnation method. A comparison of the catalytic activity for the reduction of NO_x with ammonia over Fe‐Mo/ZSM‐5, Fe‐ZSM‐5 and Mo/ZSM‐5 catalysts was carried out. Also, the effects of the conditions used for calcination as well as of the Fe/Mo ratio on the catalytic performance of Fe‐Mo/ZSM‐5 catalysts were studied. It was found that Fe‐Mo/ZSM‐5 is more active than Fe‐ZSM‐5 and Mo/ZSM‐5 separately. Fe‐Mo/ZSM‐5 exhibited the best performance for SCR reaction with a Fe/Mo ratio of 1.5 and yielded the highest NO_x conversion of 96 % at a temperature of 430 °C. The results also showed that the performance of Fe‐Mo/ZSM‐5 is sensitive to the conditions used during calcination. The bulk phase and surface composition of the Fe‐Mo/ZSM‐5 catalysts were determined by XRD, BET, and XPS techniques, respectively. The results revealed that the surface Mo percentage is the largest when the Fe/Mo ratio is 1.5, which may be related to its higher activity for catalytic reduction of NO_x. XRD results indicate that the best catalytic performance of the Fe/Mo = 1.5 sample results from a strong interaction among Fe, Mo and HZSM‐5. In addition, it can be tentatively presumed that the surface nitrous species from the calcinations play an important role in SCR of NO_x over Fe‐Mo/ZSM‐5 catalysts.     

Palladium/Copper‐Catalyzed Di‐α‐arylation of Acetic Acid Esters

A bimetallic palladium/copper catalyst system was found to effectively promote the diarylation of alkyl acetates with aryl halides under unprecedentedly mild conditions. The phenanthroline‐copper‐phosphine catalyst stabilizes the enolate intermediate to the extent that the deprotonation of esters can be achieved even with the mild base potassium phosphate. The palladium tri‐tert‐butylphosphine co‐catalyst mediates the coupling of the resulting copper enolate with a wide variety of aryl halides with selective formation of the corresponding diarylacetic acid esters.     

Delignification of Bagasse with Acetic Acid and Ozone. Part 1. Acetic Acid Pulping

Two-stage delignification of sugarcane bagasse with acetic acid and ozone was investigated. The better pulp was obtained pulping bagasse in aqueous solution of acetic acid (80% volume) at 145°C during 60 min. The liquor/bagasse ratio (L/B) was 10:1 and the kappa number was 44; it fell to 10 in the ozone stage due to selectivity of acetic acid medium. Pulp reaches a brightness of almost 70% Elrepho and the strength properties are similar to those of soda pulps without refining and better than acetosolv pulps.     

Hydrogenation of Cinnamaldehyde over Pt‐Modified Molecular Sieve Catalysts

The catalytic properties of various Pt‐modified molecular sieves were tested in liquid‐phase hydrogenation of cinnamaldehyde and compared to Pt/MgO and commercial Pt/C catalysts. The type of support considerably influenced the catalytic properties. The superior selectivity performance of microporous catalysts was confirmed; the highest selectivity to allyl alcohol of about 40 % was obtained over the beta support whereas the mesoporous MCM‐41‐supported catalyst was unselective. The highest activity was obtained over the Pt/mordenite catalyst. In order to clarify the performance of catalysts, several characterization methods (XRD, XRF, FTIR, surface measurements) were employed.     

固体酸催化剂在异丁烷／丁烯烷基化反应中的应用

概述了沸石催化剂、固体超强酸催化剂等在异丁烷／丁烯烷基化反应中地研究进展及其应用效益。     

Total Oxidation of Methane and Chlorinated Hydrocarbons on Zirconia Supported A1–xSrxMnO3 Catalysts

The catalytic behavior of ZrO₂ and ZrO₂ containing 8 mol‐% Y₂O₃ supported A_1–xSr_xMnO₃ (A = La, didymium) perovskites was studied in the total oxidation of methane, chloromethane and dichloromethane considering catalyst deactivation and byproduct formation. The perovskites are dispersed on the support surface; clusters with a perovskite‐like structure were formed. The supported catalysts are characterized by higher specific surface areas compared with the unsupported ones. Partial substitution of A‐site cations by Sr leads to an enhancement of the catalytic activity in the total oxidation of methane, but not in the total oxidation of chlorinated hydrocarbons (CHC). The catalytic activity of supported and unsupported catalysts is comparable in the total oxidation of methane in spite of the significantly lower perovskite content of the supported catalysts. In the CHC conversion the catalytic activity of the supported catalysts is higher than that of the unsupported ones.     

Development of a Continuous Segmented Flow Tubular Reactor and the “Scale‐out” Concept – In Search of Perfect Powders

The synthesis of powders with controlled shape and narrow particle size distributions is still a major challenge for many industries. A continuous Segmented Flow Tubular Reactor (SFTR) has been developed to overcome homogeneity and scale‐up problems encountered when using batch reactors. Supersaturation is created by mixing the co‐reactants in a micromixer inducing precipitation; the suspension is then segmented into identical micro‐volumes by a non‐miscible fluid and sent through a tube. These micro‐volumes are more homogeneous when compared to large batch reactors leading to narrower size distributions, better particle morphology, polymorph selectivity and stoichiometry. All these features have been demonstrated on single tube SFTR for different chemical systems. To increase productivity for commercial application the SFTR is being “scaled‐out” by multiplying the number of tubes running in parallel instead of scaling‐up by increasing their size. The versatility of the multi‐tube unit will allow changes in type of precipitate with a minimum of new investment as new chemistry can be researched, developed and optimised in a single tube SFTR and then transferred to the multi‐tube unit for powder production.     

Liquid Pool Copolymerization of Propylene/1‐Butene with a MgCl2‐Supported Ziegler‐Natta Catalyst

Summary: Liquid pool propylene/1‐butene copolymerizations were carried out in a batch reactor with a high activity Ziegler‐Natta catalyst system. Experimental runs were performed to evaluate the effect of the 1‐butene content on the crystallinity and melt temperature of the polymer resins. According to the results, 1‐butene can be significantly incorporated into the polymer chain at high polymerization rates over the whole range of copolymer compositions, leading to a decrease in the melting temperature (T_m) of the polymer, when compared to the poly(propylene) homopolymer, allowing for reduction of the sealing initiation temperature. It was observed by GPC and MFI measurements that the average molecular weights and the polydispersity index of the copolymer significantly decreased when compared to the ones obtained from poly(propylene). Despite high polymerization rates, polymer particles with good morphological features were produced in all cases. It was also observed that the absence of an external electron donor led to low crystallinity values for both the poly(propylene) homopolymer and for copolymers with different fractions of 1‐butene, when compared to literature values frequently reported for polymer resins based on 1‐butene and propylene. The obtained results indicate that a family of bulk propylene/1‐butene copolymer grades can be successfully developed for packaging and film applications.

Surface morphology and molecular weight distribution (deconvoluted into Schulz‐Flory distributions) of the propylene/1‐butene copolymer.     

特戊酸合成中固体酸催化剂的筛选及优化

通过对磺酸树脂、五硅型硼硅酸盐沸石及SO4^2-／MxOy型催化剂在特戊酸合成中活性的研究。筛选出了对本反应体系具有较高活性的固体酸催化剂SO4^2-／ZrO2。实验中发现：温度对反应性能有很大影响，在异丁烯达到超临界状态后，反应性能大大改善。在一定范围内，提高反应的压力亦能够改善反应性能。对固体酸催化剂SO4^2-／ZrO2的制备条件进行了优化。     

Synthesis of Titania Pillared Mica in Aqueous Solution of Acetic Acid

The preparation of TiO₂-pillared mica was carried out in a CH₃COOH aqueous solution. Titanium ion species were obtained by an addition of Ti(C₃H₇O₄ to an aqueous solution of CH₃COOH and by subsequent aging of the solution for a prescribed time followed by intercalation of these ionic species into the interlayers of mica. Ti⁴⁺-intercalated mica was thus obtained by ion exchange. After the sample was calcined at 773 K in air, TiO₂-pillared mica was produced. The pillaring of TiO₂ in the interlayer of mica was confirmed by XPS. The surface area TiO₂-pillared mica was about 100 times larger than that of mica alone. The basal spacings of the products heated above 523 K were in the range from 2.01 nm to 2.68 nm in the samples obtained under various conditions.     

Medium‐Temperature Shift Catalysts for Hydrogen Purification in a Single‐Stage Reactor

Interest regarding the WGS process has grown significantly, because of the recent progression in fuel cells as a clean technology for power generation. Due to the large volume and cost of WGS conventional two‐stage reactors, and also problems related to pyrophoricity and lengthy reduction of customary catalysts, the current challenge is to develop more active and stable catalysts that convert CO in a single‐stage medium temperature shift (MTS, 280–360 °C) reactor, which is applicable in small‐scale fuel cells. Advanced and newly developed catalytic systems for hydrogen purification via MTS reactions are reviewed and discussed in this study. Pt‐based catalysts on reducible oxide supports, e.g., CeO₂ and TiO₂, have mainly been used for this reaction. It is known that ceria is the most applicable active and stable support and highly promising for MTS reactions, considering its high oxygen storage capacity and mobility of surface oxygen/hydroxyl groups. New studies investigate modified ceria, e.g., CeZr, to improve its catalytic properties.