Dependence of the catalytic properties of cobalt molybdate in propylene oxidation on the surface reduction and oxygen bond energy

The dependences of the tate of partial propylene oxidation and of oxygen bond energy on the degree of cobalt molybdate reduction has been investigated by pulse and caloremetric methods. It has been found that upon reduction, the selectivity to acrolein and the oxygen bond energy increase. The steady state under the conditions examined is characterized by 22% surface reduction and the presence of uniform oxygen with a bond energy of about 85 kcal/mol.

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Selective oxidation of propylene to acrolein by silica-supported bismuth molybdate catalysts

Silica-supported bismuth molybdate catalysts have been prepared by impregnation, structurally characterized and examined as improved catalysts for the selective oxidation of propylene to acrolein. Catalysts with a wide range of loadings (from 10 to 90 wt%) of beta bismuth molybdate (??-Bi₂Mo₂O₉) were studied to provide a better understanding about the distribution of active sites, and to elucidate the role of lattice oxygen in the reaction. The catalyst containing 50 wt% of beta bismuth molybdate on SiO₂ was found to possess good distribution of active sites and sufficiently high lattice oxygen, which resulted in an extraordinary increase of the catalytic activity.     

Molecular orbital study of the catalytic oxidation of propylene on silver

Analysis of the MINDO/2 reaction coordinates concerning the decomposition of the propylene perepoxide radical anion to propylene oxide and propylene peroxide makes it possible to explain the fundamental differences of ethylene and propylene oxidation on silver catalyst.

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铋、铈钼酸盐催化剂的丙烯选择氧化动力学研究

本文目的在于研究稀土对钼酸铋的丙烯选择氧化影响,不同比例的催化剂呈现了比较复杂的动力学行为,随着催化剂组成变化,氧反应级数可由零级经过0.5级直至无一定反应级数,对丙烯的反应级数也随组成改变有很大变化,为解释这一现象,本文提出了统一反应机理,即随着催化剂组成变化,催化剂表面活性中心由晶格氧经历吸附原子态氧至吸附分子态氧变化,通过X光、红外及其它实验结果表明,预期这样的活性中心变化是由于铈的存在形成了钼酸铈晶相,破坏了钼酸铋晶体形成而促使钼酸铋更加分散缘故。     

Prediction of the catalytic action of oxide catalysts in allyl oxidation of propylene

Concepts are described according to which an efficient catalyst of propylene oxidation to acrolein should contain oxygen of two types — nucleophilic and electrophilic. This can be ensured by a combination of an amphoteric oxide and an oxide of a high-valent element. The distribution of the products of allyl oxidation also depends on the collective properties of a catalyst.

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Thermal decomposition of the 1:1 bismuth molybdate and its implications for catalytic oxidation

To study the stability of the 1:1 bismuth molybdate, thin films (300–500 Å) have been prepared by thermal evaporation of the powder samples followed by heating in air or oxygen. Electron diffraction revealed that in an oxidizing atmosphere and at temperatures higher than 400°C or in vacuum and at temperatures higher than about 350°C the 1:1 compound decomposes into the 2:1 bismuth molybdate and MoO₂. These results suggest that during catalytic oxidation and (at least) for temperatures greater than 400°C the 2:1 compound forms near the surface of the 1:1 phase, being responsible for the selective catalytic oxidation.     

Bi-Mo-Nb复合氧化物的结构与对丙烯氧化的催化活性

本文用XRD, IR, Raman, SEM和ESR等方法研究了系列氧化物Bi~2Mo~3-3XNb~2xO~12-4X(X=0.00, 0.02, 0.05, 0.10, 0.15, 0.20, 0.25) 的结构和对丙烯氧化的催化活性。结果表明, 在X<0.25范围内, 催化剂基本保持典型的α-Bi~2Mo~3O~12结构, 少量Nb^5+的掺杂, 可取代晶格中的Mo^6+, 产生氧空位,无序分布的氧空位的浓度先随X值的增加而增加, 当X=0.15时达到最大值, 催化剂对丙烯氧化的催化活性与这种氧空位的浓度成正比, 反应遵循Redox机理。     

Studies on the formation of manganese molybdate

The reaction of MoO₃ with various oxides of manganese (MnO, Mn₂O₃, Mn₃O₄ and MnO₂) and with MnCO₃ has been studied in air and nitrogen atmospheres employing DTA, TG and X-ray diffraction methods, with a view to elucidating the conditions for the formation of MnMoO₄. Thermal decomposition of MnCO₃ has also been studied in air and nitrogen atmospheres to help understand the mechanism of the reaction between MnCO₃ and MoO₃. The studies reveal that, whereas MnO, Mn₂O₃ and MnO₂ react smoothly with MoO₃ to form MnMoO₄, Mn₃O₄ does not react with MoO₃ in the temperature range investigated (48O–6OO°C). An equimolar mixture of MnCO₃ and MoO₃ reacts in air to yield MnMoO₄, while only a mixture of Mn₃O₄ and MoO₃ remains as final product when the same reaction is carried out in nitrogen. Marker studies reveal that manganese ions are the main diffusing species in the reaction between MoO₃ and manganese oxides that result in MnMoO₄.     

FCC轻汽油催化裂化生产丙烯反应规律的研究

在提升管实验装置和脉冲色谱装置上,采用ZSM-5催化剂,考察了不同条件下FCC轻汽油和2M1C5＝的裂化。结果表明,催化裂化过程添加ZSM 5催化剂可提高汽油中C5＝、C6＝的质量分数。轻汽油裂化生产丙烯的性能优于重汽油和全馏分汽油,在相对低的温度下瞬时反应能得到较高的丙烯收率。在脉冲色谱装置上,反应温度和载气流量对轻汽油和2M1C5＝裂化生产丙烯的影响一致,即反应温度升高,载气流量降低,丙烯收率增加。提高反应温度,延长停留时间可以提高丙烯对丁烯的比例。轻汽油在ZSM-5催化剂上反应,催化剂结焦失活速度开始较快,后来减缓。ZSM-5催化剂结焦失活对丙烯生成的抑制作用大于对丁烯的抑制作用,ZSM-5的强酸中心多则更有利于生成丙烯。     

Gas-chromatographic study of the retention of components of the reaction of the catalytic oxidation of propylene on porous polymers

The gas-chromatographic retention of oxygen, carbon dioxide, propane, propylene, water, propylene oxide, acrolein, acetone, and acetaldehyde on polar and nonpolar adsorbents was studied. A procedure was proposed for the gas-chromatographic determination of gaseous and liquid components of the reaction of the catalytic oxidation of propylene using one column.     

The heterogeneous catalytic oxidation of propylene in the presence of singlet oxygen in the reaction mixture

Three methods for the introduction of singlet oxygen into the reaction mixture were tested, including thermal generation of singlet oxygen on the catalyst itself, the introduction of singlet oxygen from an external source, and photogeneration of singlet oxygen on the catalyst. Zeolites with admixtures of Mo, Bi, V, and Ni and SiO₂ with deposited Mo, V, and Bi were used. Common to all reactions was an increase in the yield of deep oxidation products in the presence of singlet oxygen. A sharp increase in the yield of mild oxidation products was observed in the oxidation of propylene on a Bi/SiO₂ catalyst. The generation of singlet oxygen under irradiation at 240–260 nm was found to cause deep oxidation only. Mild oxidation products could only form under the action of total mercury lamp light.     

Fe2O3/Al2O3催化氧化苯偶姻制备苯偶酰

考察了几种常用载体负载金属氧化物催化分子氧氧化苯偶姻制备苯偶酰的性能 ，发现氧化铁、三氧化二铝催化活性较高，稳定性较好。以吡啶为溶剂，用483K下 活化的含铁14．8％的氧化铁／三氧化二铝作催化剂，当其用量为苯偶姻用量20％ （质量分数），253K下反应1h,苯偶酰平均产率98．1％。用IR，MS，和^1H NMR光 谱对其结构进行了表征。     

Nonsteady-state oxidation of propylene on supported silver catalysts

Nonsteady-state epoxidation of propylene on silver has been studied to establish the reason for the low catalyst activity and selectivity that appear to be due to side reactions of the formation of hydrogen-deficient deposits.

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Theoretical considerations on the oxidation of propylene on transition metal molybdates

Molecular orbital calculations of charge distributions for the -allyl complex with transition metal ions in molybdates show that the activated -allyl species is formed by transfer of charge density to the metal ion. The relative charge distributions on the three carbon atoms of the adsorbed allyl species govern the course of oxidation reaction.

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十二水合硫酸铁铵催化合成己二酸二乙酯的研究

以十二水合硫酸铁胺为催化剂合成了己二酸二乙酯,确定了酯化优化条件。实验结果表明,催化剂的催化活性高,反应条件温和,方法简便,酯化率优良。     

过氧化氢水溶液催化氧化环戊烯制备戊二醛机理研究

在钨酸-叔丁醇体系中,用H~2O~2水溶液氧化环戊烯制备戊而2醛的机理是:环戊烯首先氧化成环戊烯氧化物,然后生成过氧化物中间物,经分离检定,确证为β-羟基过氧化氢,中间物再进行重排,形成戊醛产物,在H~2O~2等量的情况下,重排只能部分进行,加大H~2O~2用量,可以使中间物埃常温下重排接近完全.