Title : Conversion Of Propane In The Presence Of Benzene On Zeolite Systems
Abstract:
The involvement of C1-C3 alkanes in the processes of obtaining valuable products is of great theoretical and practical importance. One of the ways to solve this problem is the possibility of catalytic involvement of these alkanes in the alkylation of aromatic compounds.( Y, M, ZSM-5) for the conversion of C6H6:C3H8 mixtures. The study was carried out on a mechanical mixture of an aluminum-platinum-rhenium catalyst (APRC) prepared according to a well-known method and H-forms of zeolites (Y, M, ZSM-5). The conversion of propane-benzene mixtures was studied in a flow reactor at 453-723 K, atmospheric pressure and volumetric feed rate of the reaction mixture 125-1000 h-1. Before the experiments, the catalyst was treated with air at 673 K. The results of studying the conversion of C6H6:C3H8 mixtures on a mechanical mixture of catalysts (SC) showed that only the presence of SC benzene is active in propane conversion. The hydrocarbon products of the conversion of C6H6:C3H8 mixtures are propylene, isopropylbenzene (IPB), and other aromatic hydrocarbons (ArH). The introduction of even small amounts of benzene into the reaction (for example, 10 mol.%) leads to the dehydrogenation of propane and the formation of hydrogen, the molar value of which corresponds to the total molar conversion of propane. The formation of IPB and propylene during the conversion of a mixture of C6H6:C3H8 =1:9 to SC indicates low-temperature dehydroalkylation of benzene with propane and its dehydrogenation. The release of hydrogen during the conversion of C6H6:C3H8 mixtures is a total reflection of the noted reactions.The conversion of C6H6:C3H8 mixtures depends on the pretreatment of the catalysts. The presence of an activation period is typical for the release of hydrogen on the SC treated with air. This SC activation period does not depend on the zeolite component, but is associated exclusively with the interaction of propane with APRC and is a consequence of the partial reduction of the SC metal component.The yield of conversion products of C6H6:C3H8 mixtures depends on their ratio. A change in the C6H6 / C3H8 molar ratio from 1 : 9 to 1 : 1 leads to an increase in the conversion of benzene and an increase in the Agr of the C9 composition. Varying the OS from 125 to 1000 h-1 changes both the conversion of the components of the C6H6:C3H8 mixture and the distribution of the reaction products. At OS below 500 h-1, an increase in the formation of IPB occurs in the almost complete absence of propylene. An increase in space velocity leads to a monotonic decrease in the conversion of benzene, while the conversion of propane in the range of OS 125 - 500 h-1 decreases, and then increases again with an increase in OS from 500 to 1000 h-1.Temperature has a significant effect on the conversion of C6H6:C3H8 mixtures to SA. For example, the formation of IPB occurs even at 453 K. With an increase in temperature, propylene (523 K) is sequentially fixed in the reaction products, and at 573 K and above, n-propylbenzene (NPB) and ArU, respectively. An increase in temperature from 453 to 593 K promotes an increase in the conversion of benzene to IPB and ArU. In the range 593 - 648 K, the conversion of benzene decreases, while the conversion of propane continues to increase. At 673–723 K, the formation of IPB and propylene practically ceases, and the formation of ArH, as well as the conversion of benzene, after passing through the minimum values, increases again in the form of C7–C8 alkylaromatic hydrocarbons. These changes are accompanied by the formation of low molecular weight alkanes.The data obtained show that the type of zeolite affects the conversion of individual components of the reaction mixture and the yield (selectivity) of the reaction products. So, at a temperature of 593 K, corresponding to the maximum yield of IPB, the conversion of benzene decreases depending on the nature of the zeolite component of SC in the sequence Y>M>ZSM-5, and at 648 K, corresponding to the maximum yield of propylene, this series is converted to ZSM 5>M>Y.
