Catalytic properties and phase composition of multicomponent catalysts for oxidative ammonolysis of propane

Studies of the phase composition and catalytic properties of several complex oxide catalysts for oxidative ammonolysis of propane indicate that the active phases of these catalysts are antimonates of the respective metals. Phosphorus and tungsten additives to the catalysts promote the formation of such phase compositions, i.e. the formation of antimonates and the binding of excess antimony oxide.

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铯添加对VOx/SBA-15催化剂丙烷氧化脱氢性能影响

我们考察了碱金属铯的添加对具有单一活性中心（分立的VOx四面体）的VOx／SBA-15催化剂上丙烷氧化脱氢反应性能的影响,发现铯的加入可以显著改善丙烯的选择性．在相同的丙烷转化率时,丙烯选择性提高了约10％．对催化剂的X射线衍射,拉曼光谱,程序升温还原,吡啶吸附IR光谱和程序升温脱附表征结果表明,少量碱金属的加入,并未改变活性中心的结构及其可还原性能,但明显降低了催化剂表面酸量,尤其是B酸量,从而有利于产物丙烯的脱附,抑制了深度氧化产物COx的产生,提高了丙烯的选择性．     

Effect of aluminum modification on catalytic properties of PtSn-based catalysts supported on SBA-15 for propane dehydrogenation

The catalytic properties of PtSn-based catalysts supported on siliceous SBA-15 and Al-modified SBA-15, such as Al-incorporated SBA-15 (AlSBA-15) and alumina-modified SBA-15 (Al2O3/SBA-15), for propane dehydrogenation were investigated. Al2O3/SBA-15 was prepared either by an impregnation method using aluminum nitrate aqueous solution, or by the treatment of SBA-15 with a Al(OC3H7)3 solution in anhydrous toluene. N2-physisorption, FT-IR spectroscopy, solid-state 27Al MAS NMR spectroscopy, hydrogen chemisorption, XRF, NH3 temperature-programmed desorption, X-ray photoelectron spectroscopy and TPO were used to characterize these samples. Among these catalysts, the PtSn-based catalyst supported on Al2O3/SBA-15, which was grafted with Al(OC3H7)3, exhibited the best catalytic performance in terms of activity and stability The possible reason was due to the high Pt metal dispersion and/or the strong interactions among Pt, Sn, and the support.     

nV-MCM-41 催化剂的制备及其催化 CO2氧化丙烷脱氢反应性能

丙烯是一种重要的化工原料, 其下游产品丰富, 用途广泛, 主要用于生产聚丙烯、丙烯腈、丙烯酸和丁醇等化工产品.丙烯的需求正在不断增长, 而传统的丙烯生产方法如蒸汽裂解和石油催化裂化, 存在反应温度高、积碳严重且丙烯收率较低等问题. 因此研制丙烷脱氢制取丙烯的高效催化剂尤为重要. 研究发现, 以 CO2作为温和氧化剂进行逆水气变换反应可有效促进丙烷脱氢. 催化剂主要由活性组分与载体构成, 本文选择可用于活化丙烷的钒作为主要活性组分. 钒氧化物在载体上的高度分散是提高丙烷脱氢反应活性的关键. MCM-41 拥有较大的比表面积和高度有序的介孔结构, 可更有效地分散活性位点. 本文采用一步法合成了不同钒含量的 nV-MCM-41 催化剂 (1.9-10.6 wt%), 并研究了其在以下条件下催化丙烷氧化脱氢制丙烯反应性能: 600 °C, 催化剂质量 0.2 g, 进料气体组成 C3H8/CO2/Ar (摩尔比) = 1/4/4, 进料气体总流量 15 mL/min. 其中 6.8V-MCM-41 催化剂具有最高的活性, 其初始丙烷转化率达 58%, 丙烯选择性达 92%, 远高于相似反应条件下早期研究的 nV-SBA-15 催化剂. 并在四次反应-再生循环中始终保持其原来的高反应活性. 本文借助于 N2吸附-脱附、拉曼光谱 (Raman)、X 射线光电子能谱 (XPS)和热重 (TG) 等手段探究了不同钒含量的 nV-MCM-41 催化剂在丙烷脱氢反应中催化性能差异的原因.氮气吸附-脱附结果表明, 所有催化剂都存在典型的高度有序的介孔结构, 并没有因为钒组分的掺杂而破坏. nV-MCM-41催化剂拥有较大比表面积,并随钒掺杂量的增加而减小. 其中,10.8V-MCM-41催化剂的比表面积急剧下降,可能是由于产生了结晶的 V2O5阻塞了孔道. Raman 结果表明, 当钒负载量超过 6.8 wt% 时, 出现了 V2O5的结晶峰. 另外根据单分散的四面体钒氧化物的特征峰面积发现, 6.8V-MCM-41 催化剂中钒物种分散度最高, 与其具有最高催化活性结果一致. XPS 结果也进一步证明 6.8V-MCM-41 钒物种的分散度最高. 在连续反应过程中 6.8V-MCM-41 催化剂失活较快,可归结于活性钒位点的还原与催化剂表面的积碳. 通过氧化再生, 可恢复催化剂活性, 并且在 4 次再生循环中始终保持其良好稳定的活性.     

Effect of additives on properties of vanadia-based catalysts for oxidative dehydrogenation of propane: Experimental and quantum chemical studies

Effect of additives (A) comprising main group elements (K, P) and transition metals (Ni, Cr, Mo) to VO_x/SiO₂ catalysts on their catalytic behavior in oxidative dehydrogenation (ODH) of propane are studied. The experimental findings are compared with results of quantum chemical calculations performed for a model O=V---O---V^* cluster in which V^* atom is replaced by an atom of A. The selectivities to propene found in experiments change on introducing the additives, decreasing in the sequence VK(64)>VCr(38)>VMo=VNi(32)>VP(28)V0(27). Quantum chemical calculations indicate the change in the electron density on the atoms of the active O=V---O groups for the clusters with the additives’ atoms. The extent of the electron transfer from A towards the active group (the increase in the centre basicity) follows the sequence of the decreasing selectivity to propene, confirming the role of acid–base properties in controlling the selectivity in ODH of propane. Results of calculations show also an exceptional behavior of the potassium (the most effective additive for the increase in the selectivity in experiments); in contrast to all other additivies, K transfers electrons towards both V and O atoms in the active group, and does not form a definite O---K bond, but is rather “adsorbed” on the cluster.     

Basicity of alumina-magnesia catalysts

In the series of Al₂O₃, MgO and Al₂O₃–MgO catalysts, those containing about 75% Al₂O₃ and 25% MgO show the highest activity in the decomposition of diacetone alcohol in non-polar solvents. The fastest rates of reaction, which follows the zero-order kinetics over the whole range of conversion, coincide with the occurrence of strong basic sites on the catalyst surface.

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Al₂O₃, MgO Al₂O₃–MgO , 75% Al₂O₃ 25% MgO, . , .

     

Highly efficient VOx/SBA-15 mesoporous catalysts for oxidative dehydrogenation of propane

Highly dispersed vanadia species on SBA-15 mesoporous silica have been found to exhibit a highly efficient catalytic performance for the oxidative dehydrogenation (ODH) of propane to light olefins (propene + ethylene).     

Interaction between the components of the reaction mixture and the surface of catalysts for the oxidative ammonolysis of propylene

A study was made of the change in the properties of tin-antimony and bismuthmolybdenum oxide catalysts during the partial reduction of their surfaces with propylene and a propylene-ammonia mixture. Different characteristics of the interaction of ammonia with the surface of the catalysts studied were established.

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Pulse studies of cyclohexane oxidative ammonolysis to adiponitrile over Ti?Sb?O catalysts

The catalytic activities in ammoxidation of cyclohexane to adiponitrile (ADN) was compared with the phase compositions of Ti–Sb–O catalysts. It was shown that the reaction is limited by the step of ADN desorption from the catalyst.

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Carbonization of alumina-based catalysts in propionitrile ammonolysis

Summary The asymmetric hydrogenation of ethyl 2-acetoxyacrylate (EtA) by cinchonidine modified Pd/Al2O3 and Pt/Al2O3 catalyst is described (ee up to 60 %). This is the first example of asymmetric hydrogenation of an enol esters in heterogenized conditions.     

Studies on the oxidative dehydrogenation of propane to propene over Co-V-O catalysts

A series of Co-V-O catalysts were prepared and their catalytic performances for the oxidative dehydrogenation of propane to propene were investigated. It was found that the p-type catalysts showed higher catalytic behavior than the n-type catalyst.     

Acid-base and catalytic properties of iron-antimony oxide catalysts

Iron antimonate, whose strongest acidic sites (Fe³⁺) are blocked by weak acidic aprotic centers Sb³⁺, is an active and selective catalyst for the ammoxidation of propylene.

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, (Fe⁺³) Sb⁺³, .

     

In situ UV-vis-NIR diffuse reflectance and Raman spectroscopy and catalytic activity studies of propane oxidative dehydrogenation over supported CrO3/ZrO2 catalysts

The molecular structures, oxidation states, and reactivity of 3 and 6% CrO3/ZrO2 catalysts prepared by incipient wetness impregnation were examined under different conditions. The in situ Raman spectroscopic studies under dehydrated conditions reveal that the 3 and 6% CrO3/ZrO2 catalysts possess equal amounts of monochromate and polychromate species. Consequently, monolayer coverage on this ZrO2 support is about 3% CrO3. The 6% CrO3/ZrO2 possesses an additional Raman band due to Cr2O3 crystals corresponding to the remaining 3% CrO3. Furthermore, during reaction conditions the polychromate species is preferentially reduced, the monochromate species are slightly affected, and the Cr2O3 crystals are not affected. The in situ UV-vis-NIR diffuse reflectance spectroscopy results reveal that under steady-state reaction conditions the extent of reduction and edge energy position of surface Cr6+ cations increase with an increase in reduction environment for the 3 and 6% CrO3/ZrO2 samples. Propane oxidative dehydrogenation (ODH) studies reveal that the catalytic activity expressed in moles of propane converted per gram catalyst per second is similar for the two catalysts, which is consistent with equal amounts of molecularly dispersed chromia present. The turnover frequency for the 6% CrO3/ZrO2 catalyst is, however, smaller than that for the 3% CrO3/ZrO2 sample due to the presence of Cr2O3 crystals, which are relatively inactive for propane ODH. For this catalytic system and for the experimental conditions used, propene, CO, and CO2 are primary products. Furthermore, the 33-39% propene selectivity is not affected by the C3H8/O2 ratio for both catalysts. Structure-reactivity studies suggest that the molecularly dispersed species are present in equal amounts in the 3 and 6% CrO3/ZrO2 samples as Cr6+ monochromate and polychromate species are the most effective catalytic active sites taking part in the propane ODH reaction.     

A study of the oxidative ammonolysis of quinoline

The oxidative ammonolysis of quinoline has been studied. The main products are pyridine, benzene, benzonitrile, and nicotinonitrile. Free nicotinic and benzoic acids and their amides are formed in small amounts. The gaseous products of the reaction are hydrogen cyanide and oxides of carbon. The most significant factors determining the direction of the process are the content of tin oxides in the catalysts, the concentration of ammonia in the feed gases, and the temperature of the reaction.Translated from Khimiya Geterotsiklicheskikh Soedinii, Vol. 6, No. 6, pp. 794–797, June, 1970.     

Steam-activated FeMFI zeolites as highly efficient catalysts for propane and N2O valorisation via oxidative conversions

The reaction between C3H8 and N2O over steam-activated FeMFI zeolites leads to high yields towards propene (24%) and propionaldehyde (6%) at 773-798 K.     

木素分子氧化性氨化反应过程中的结构变化

在一定压力和温度条件下，木素大分子和氨发生反应，生成一些氮修饰木素。为了解反应过程中木素分子结构的变化，用^1^3C和^1H-^1^3C2D-NMRHMQC技术检测了反应前后的分子谱图，结果显示反应过程中木素分子的碎裂化现象十分明显，很可能在氧化性氨化反应过程中，木素大分子表面基团发生了氧化性修饰，如一些侧链CH~3被氧化形成CHO和COOH等，然后这些基团与氨结合等；此外，芳香环结构可能通过粘康酸单体断裂形成一些酰胺类产物，但木素分子内部的高度缩合性结构没有明显的变化。     

BiMo基复合氧化物催化剂晶格氧性质与丙烷选择氧化性能

研究了不同组成、结构的BiMo基复合氧化物催化剂的丙烷选择氧化至丙烯醛的性能.X射线衍射(XRD)、X光电子能谱(XPS)、原位傅里叶变换激光拉曼光谱(FT-LRS)、电子顺磁共振(ESR)等多种表征结果表明,BiMo基复合氧化物催化剂上丙烷经由中间物丙烯选择氧化至丙烯醛,催化剂的晶格氧为选择性活性氧物种.丙烷直接氧化下丙烷至丙烯醛的选择性和收率与催化剂的Mo=O物种的氧化-还原性质密切关联,而Mo=O物种的性质又取决于Mo离子的配位环境,Mo=O物种的选择性转化丙烷经由丙烯至丙烯醛活性随畸变MoO6八面体、共顶点八面体、共边八面体、MoO4四面体配位环境递增.组成、结构优化调变的催化剂上丙烷选择氧化至丙烯醛选择性和收率可达45%和13.5%,催化剂中具有选择氧化活性的晶格氧物种数可达258 μmol/g.     

Oxidative ammonolysis of 3-picoline on mixed oxide catalysts

The oxidative ammonolysis of 3-picoline has been studied on the following catalysts: V₂O₅ on corundum, V₂O₅ with the addition of 1% of H₂WO₄ on corundum, V₂O₅ + MoO₃ + P₂O₅ (10.350.35) on silica gel, V₂O₅ + Al₂O₃, and a melt of V₂O₅ + TiO₂ (10.22). Mixed catalysts of vanadium and titanium oxides exhibited the highest activity and selectivity. With the passage of 25–45 moles of oxygen (in the form of air), 5–10 moles of ammonia, and 50–70 moles of water per mole of 3-picoline at a temperature of 390–410° C, the amount of nicotinonitrile formed on these catalysts amounted to 85–90% of the theoretically possible amount.Part LXIII of the series Oxidation of organic compounds; for part LXII, see [1].