Adaptation of the microscopic properties of redox catalysts to the type of gas-solid reactor

Catalysts of selective oxidation usually work in a simultaneous redox mode in reactant/air cofed reactors. The solid must provide selective lattice oxygen according to a kinetic mechanism depending on operating conditions that differ from one reactor to another. Better catalytic performance can be obtained in a recirculating solids reactor because it allows separate optimization of the reduction and oxidation steps. Among the microscopic properties of the catalyst, the crystal morphology is to be taken into account because it influences its reactivity on stream. These considerations lead to a new approach of the catalyst-reaction-reactor trio.     

Propane oxydehydrogenation reaction on a VPO/TiO2 catalyst. Role of the nature of acid sites determined by dynamic in-situ IR studies

A VPO/TiO₂ catalyst tested in the oxydehydrogenation reaction (ODH) of propane between 300 and 400°C shows satisfactory performances (up to 80% of propene selectivity at 2% of propane conversion at 300°C or 56% of propene selectivity at 9% of propane conversion at 400°C). Addition of water or pyridine in the feed gas tends to decrease the propane conversion and enhances the propene selectivity. It is shown that water increases the number of Brönsted surface acid sites by dissociative adsorption which, in turn, enhances propene selectivity at the expense of the CO_x selectivity. These results are in good agreement with spectroscopic IR observations performed under catalytic conditions showing that the Lewis acid sites are linked to CO_xformation, whereas it seems that Brönsted sites would rather be linked to propene formation.     

Role of the nature of the acid sites in the oxydehydrogenation of propane on a VPO/TiO2 catalyst. An in situ FT-IR spectroscopy investigation

Catalytic activity and surface acidity during the oxydehydrogenation of propane over a VPO/TiO₂ catalyst were determined by a dynamic in situ FT-IR spectroscopy technique at 350°C. Pyridine was used as a probe molecule for the acidity measurements. The obtained results show that propene formation is linked to Brønsted acid sites and that water increases the number of these sites which, in turn, increases propene selectivity.     

蒸气压渗透法(VPO)及其在测定氯化钾水溶液渗透系数中的应用

从VPO仪的工作原理,仪器的标定方法及其在溶液热力学研究中的应用方面,讨论了VPO方法测定溶液 渗透系数的理论基础,进一步探讨了溶液渗透系数与过量热力学函数的关系,并说明VPO方法在研究溶液的热力 学性质及过量热力学性质方面将具有十分重要的意义.     

A Novel Route to One-step Formation of ɛ-caprolactam from Cyclohexane and Nitrosyl Sulfuric Acid Catalyzed by VPO Composites

A series of VPO composites were employed to catalyze the reaction of cyclohexane with nitrosyl sulfuric acid in the presence of fuming sulfuric acid. To our delight, ɛ-caprolactam was for the first time directly obtained through such one-step catalytic process. VPO composite catalysts were proven to be efficient for the reaction, especially, the transition metals introduced to Al–VPO composite catalysts could improve the reactions selectivity to some extent. Among them, the Mn–Al-VPO composite catalyst gave the best results with 11.65% of conversion and 34.70% of selectivity to ɛ-caprolactam. While the conversion and selectivity are too low at this time to be commercially viable, this discovery establishes a potential new single step process for making ɛ-caprolactam from cyclohexane. A reaction mechanism is proposed.     

环型四氢呋喃齐聚物的合成与表征

首次采用丁二酰氯和１,４－二溴甲苯与线型双端羟基四氢呋喃齐聚物进行进行分子内的成环反应,制得了环型四氢呋喃聚醚,综合沉淀分级试样的绝对分了阳的测定,端基测定,红外光谱和核磁共振测定结果证明,合成产物系环型四氢呋喃齐聚物。     

蒸汽压渗透法分析聚异丁烯的数均分子量

概述了蒸汽压渗透法分析聚异丁烯数均分子量的方法,验证了环忆烷是最理想的溶剂,同时考察了在实验室合成聚异丁烯的监控分析中单点法的应用情况。     

Characterization of cobalt-impregnated VPO catalysts

Cobalt-impregnated VPO catalysts containing 1–6% of the metal by weight were prepared. The catalytic tests showed that cobalt impregnation significantly increased the overall activity while slightly decreasing the maleic anhydride selectivity. To investigate the origin of the cobalt effect, the solids were characterized using XRD, Raman spectroscopy, FT-IR, TPR and XPS. No structural effects were detected through XRD. TPR showed that the non-equilibrated catalysts contain cobalt oxides which react with the VPO solids to yield a hard to reduce system. Non-equilibrated umpromoted and promoted (low cobalt loadings) catalysts contain small proportions of V(V) phases. After several 100 h on stream, the only phase detected in all cases was V(IV) vanadyl pyrophosphate. The surface oxidation state of vanadium was V(IV). The maleic anhydride yield correlates with the increased exposure of cobalt on the catalysts surface.     

正丁烷氧化制顺丁烯二酸酐VPO催化剂活性相性质的研究

采用三种典型的还原方法制备VPO催化剂 ,并且进行了XRD、IR、TG和DTA的表征测试及其由正丁烷、丁烯选择性氧化制顺丁烯二酸酐的评价试验。研究了VPO催化剂活性相的生成与其性质 ,探讨了活性相结构对其催化性能的影响。结果表明 ,不同的还原方法可以制备具有不同性质的活性相 (VO) 2 P2 O7,( 0 2 0 )晶面适宜失序变形的(VO) 2 P2 O7,对于促进催化性能的提高具有重要的作用。     

VPO催化剂用于丙烷晶格氧选择氧化制丙烯酸的研究

用脉冲反应色谱研究了丙烷与钒磷氧化物（ＶＰＯ）催化剂晶格氧反应制丙烯酸的可行性以及温度、停留时间等反应条件的影响,结果表明,在没有气相分子氧存在的情况下,丙烷能与ＶＰＯ催化剂的晶格氧反应生成丙烯酸和乙酸;被还原后的催化剂可以用空气－水的混合气进行氧化再生。反应温度和停留时间对脉冲反应的影响与对固定床连续流动反应的影响基本相同,升高反应温度与或增加停留时间,使转化率增加,选择性降低;丙烯酸和乙酸的收