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首页> 外文学位 >Catalyst deactivation in the synthesis of methyl acetate from methyl ether using group VIII metal salts of phosphotungstic acid.
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Catalyst deactivation in the synthesis of methyl acetate from methyl ether using group VIII metal salts of phosphotungstic acid.

机译：使用磷钨酸的group族金属盐从甲醚合成乙酸甲酯时催化剂失活。

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Heteropoly acids have received much attention in the literature. Of particular importance is phosphotungstic acid which has undergone ion-exchange with several group VIII metals identified as active carbonylation catalysts in the past, namely, rhodium, iridium, palladium, and ruthenium. The resulting metal substituted phosphotungstic acid salt was then found to be active as a methanol carbonylation catalyst producing methyl acetate. Dimethyl ether can be produced much more efficiently than methanol in a liquid phase process. The potential, therefore, for production of methyl acetate from a dimethyl ether based process is of industrial importance. Specifically, conversion of dimethyl ether to methyl acetate was investigated over a variety of group VIII metal substituted phosphotungstic acid salts. The effect of active metal, support type, multiple metal loading and feed conditions were also examined. Finally, the differences in the reaction pathway for methyl acetate production from dimethyl ether versus methanol were compared, especially as it relates to catalyst deactivation.; The investigation of dimethyl ether conversion to methyl acetate is important from several aspects. First, methyl acetate has importance as a specialty chemical. It is used in the production of ethylidene diacetate, a precursor to vinyl acetate which is a monomer for polyvinyl acetate used in paints. Methyl acetate may also be converted to acetic acid via hydrocarbonylation (reductive carbonylation) or hydrolysis(49) -acetic acid is of wide-scale industrial importance as a keystone to other industrially important petrochemicals. The work presented here is unique in its examination of the causes of catalyst deactivation involved in the conversion of methyl ether to methyl acetate. In addition, very little work has been found in the literature which utilizes trivalent salts of heteropoly acids. The use of this relatively new catalyst should add to the growing knowledge base of this class of oxoaxids as well as the field of catalysis in general.; The experimental investigation was carried out in a fixed-bed mode of operation utilizing a mini-pilot plant designed and constructed for general research on gas phase reactions. Approximately 8 grams of supported catalyst was placed at the center of a tubular reactor. Catalyst batches consisted of different group VIII metals supported on a variety of silicon based supports. All reactions were carried out between 200{dollar}spcirc{dollar}C and 300{dollar}spcirc{dollar}C utilizing a methyl ether and CO gas mixture at atmospheric pressure with a dimethyl ether weight hourly space velocitie (WHSV) of 0.15 hr{dollar}sp{lcub}-1{rcub}.{dollar}; The results have shown that of the group VIII metals investigated, iridium shows the highest carbonylation activity of all the metals. No significant synergistic effects could be found among multiple metal loadings. In addition, the 150 A average pore size SiO{dollar}sb2{dollar} showed the best compatibility with the iridium-based catalyst in terms of activity with time on stream. In comparison to methanol carbonylation using the same catalyst, a dimethyl ether feedstock was found to have higher initial CO conversion levels, but rapid deactivation. Subsequent catalyst characterization showed that this deactivation is due to coke formation in conjunction with the loss of acidity of the catalyst over time. Using dimethyl ether as a feedstock will always eventually deplete the proton concentration of the catalyst. Using methanol does not result in rapid deactivation and has a great advantage over methyl ether in this case, despite the lower methyl acetate selectivity. (Abstract shortened by UMI.)
机译：杂多酸已在文献中引起很多关注。特别重要的是磷钨酸，其过去已与几种被鉴定为活性羰基化催化剂的VIII族金属进行了离子交换，即铑，铱，钯和钌。然后发现所得的金属取代的磷钨酸盐具有作为甲醇羰基化催化剂的活性，产生乙酸甲酯。在液相工艺中，二甲醚的生产效率要比甲醇高得多。因此，由基于二甲醚的方法生产乙酸甲酯的潜力具有工业重要性。具体地，在各种VIII族金属取代的磷钨酸盐上研究了二甲醚向乙酸甲酯的转化。还检查了活性金属，载体类型，多种金属负载和进料条件的影响。最后，比较了由二甲醚与甲醇生产乙酸甲酯的反应途径的差异，特别是与催化剂失活有关的差异。从多个方面研究二甲醚转化为乙酸甲酯是重要的。首先，乙酸甲酯作为特殊化学品非常重要。它用于生产亚乙基二乙酸酯，这是乙酸乙烯酯的前体，乙酸乙烯酯是油漆中使用的聚乙酸乙烯酯的单体。乙酸甲酯也可通过烃基化（还原羰基化）或水解转化为乙酸（49）-乙酸在工业上具有重要意义，是其他工业上重要的石化产品的基石。此处介绍的工作在检查与甲基醚转化为乙酸甲酯有关的催化剂失活的原因方面是独特的。另外，在文献中发现很少有利用杂多酸的三价盐的工作。这种相对较新的催化剂的使用应增加这类恶臭化合物的知识基础，以及一般的催化领域。实验研究是在固定床操作模式下进行的，使用的小型中试设备是为气相反应的一般研究而设计和建造的。将约8克负载的催化剂置于管式反应器的中心。催化剂批次由负载在各种基于硅的载体上的不同的VIII族金属组成。使用甲基醚和一氧化碳气体混合物，在大气压力下，以0.15小时的二甲醚重量小时空速（WHSV），在200℃至300℃之间进行所有反应。 {dollar} sp {lcub} -1 {rcub}。{dollar};结果表明，在所研究的族金属中，铱显示出所有金属中最高的羰基化活性。在多种金属负载之间没有发现明显的协同作用。另外，就随时间变化的活性而言，平均孔径为150 A的SiO {dollar} sb2 {dollar}与铱基催化剂表现出最佳的相容性。与使用相同催化剂进行甲醇羰基化相比，发现二甲醚原料具有较高的初始CO转化率，但会迅速失活。随后的催化剂表征表明，这种失活是由于焦炭的形成以及随着时间的流逝催化剂酸度的损失。使用二甲醚作为原料将最终最终耗尽催化剂的质子浓度。尽管乙酸甲酯的选择性较低，但使用甲醇不会导致快速失活，并且在这种情况下比甲醚具有很大的优势。 （摘要由UMI缩短。）

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