Jagannath Das

Novel catalytic aspects of beta zeolite for alkyl aromatics transformation

Abstract A highly siliceous, large pore, crystalline aluminosilicate has been employed as a catalyst for several industrially important reactions. These reactions include benzene isopropylation to cumene, isopropylation of toluene to cymene, cumene alkylation to diisopropyl benzene, transalkylation and disproportionation of C7 and C9 aromatic streams to produce xylenes and meta-xylene isomerisation in the presence of ethylbenzene. Beta zeolite selectively catalyses benzene alkylation to cumene and formation of n-propyl benzene has been almost eliminated. Beta zeolite was found to be selective for cymenes and diisopropyl benzene formation. The alkylation activity of zeolite beta for cumene isopropylation can be stabilised by steaming and treatment with (NH4)2SiF6. In disproportionation and transalkylation over large pore beta zeolite the xylene yields were found to be better as compared to that of medium pore zeolites. Beta zeolite appears to be quite promising a candidate for several commercial applications.

Transalkylation and disproportionation of toluene and C9 aromatics over zeolite beta

Transalkylation and disproportionation (TADP) of toluene and C9 aromatics from a commercial stream have been studied over a zeolite possessing a three-dimensional, 12-membered ring pore system. The study encompassed the effect of C9 aromatics content in feed on TADP. Formation of xylenes was maximum with a feed containing 50 ∶ 50 toluene and C9 aromatics. In order to understand the role of different C9 aromatics in TADP, experiments using individual C9 aromatics with and without toluene mixture as feed were carried out. An interesting observation of these experiments was that ethyltoluenes produced xylenes through disproportionation of toluene generated from their deethylation. The total yield of xylenes was much less than that obtained from trimethyl benzenes. A reaction scheme accounting all the reactions taking place during TADP is proposed.

Effect of extrusion and silylation of ZSM-5 onpara selectivity of diethylbenzenes

Abstract Zeolite extrusion using an alumina binder in different proportions and its effect on the selectivity for the para isomer in diethylbenzenes during ethylbenzene ethylation with ethanol is reported. The study also includes the silylation of extrudates of zeolites with different Si/Al ratios to enhance the para selectivity. It was observed that in the presence of binder the diethylbenzenes fraction contained less para isomer due to increased isomerization of primary product of alkylation. As compared to pure zeolite, the extrudates required a higher amount of silica deposition to enhance the para selectivity.

Zeolite beta catalyzed C7 and C9 aromatics transformation

Abstract Transformation of commercial C 7 and C 9 aromatic streams to xylenes over zeolite beta have been studied. These results have been compared with those obtained on other zeolites like ZSM-5 and mordenite. The effect of variations in reaction parameters like temperature, weight hourly space velocity (WHSV) and feed composition on xylene formation was considered. The trimethylbenzenes became disproportionated, while ethyltoluenes underwent de-ethylation followed by disproportionation of product toluene. The highest yield of xylenes was obtained with a feed consisting of nearly equal proportions of toluene and 1,3,5-trimethylbenzene. Lower WHSV and higher temperature enhanced the formation of xylenes.

Selective ethylation of ethylbenzene in the presence of other aromatics

Abstract The alkylation of ethylbenzene in the presence of other aromatic compounds has been studied over a pore size regulated MFI zeolite. The aromatic compounds chosen were of various kinetic diameter, hence they were expected to hinder the movement of reactant molecules both on the external surface and within zeolite channels. It was observed that some of the aromatic compounds got alkylated along with ethylbenzene. The effects of varying the concentration of aromatic compounds in the feed on ethylbenzene conversion and product distribution have been discussed.

Reactions of ethylbenzene in the presence of toluene over external surface passivated MFI zeolite

The reactions of ethylbenzene in the presence of toluene were studied over external surface passivated MFI zeolite. With increase in extent of external surface passivation the para selectivity of both transalkylation and disproportionation reactions enhanced. The effects of mole ratio of ethylbenzene to toluene, reaction temperature and WHSV on the performance of the modified zeolite are discussed. It was observed that the high para selectivity feature of the modified zeolite is not influenced by changes in reaction conditions.

Selective synthesis of para-ethylphenol over pore size tailored zeolite

Abstract Selective ethylation of phenol with ethanol to para -ethylphenol, over pore size tailored ZSM-5 zeolite, has been studied. Fine control of pore openings of ZSM-5 was achieved by chemical vapour deposition of silica employing tetra-ethyl orthosilicate. Selectivity for para -ethylphenol increased with the extent of silica deposition and under a comparable phenol conversion level, pore size controlled ZSM-5 exhibited about 88% selectivity for para -ethylphenol, as compared to only 37% with unmodified ZSM-5. The influences of various reaction parameters, e.g., temperature, WHSV and phenol to ethanol mole ratio were also studied. Addition of water to reactants improved the selectivity for ethylation, as well as selectivity for para -ethylphenol, and also stability of the catalyst. A comprehensive scheme for selective phenol ethylation to para -ethylphenol has been proposed.

Design and Development of Zeolite-Based Catalytic Processes for Aromatics Production

Processes for the production of xylenes, which occur in an integrated aromatic complex, are discussed. A brief overview of the work carried out at Indian Petrochemicals Corporation Limited for the development of zeolite-based catalytic processes for the production of aromatics is presented. This includes xylene isomerization, transalkylation and disproportionation of C7 and C9 aromatics for maximization of xylenes, selective disproportionation of toluene and selective alkylation of mono-alkylaromatics to p-dialkylbenzene. Achievements in the commercialization of zeolite-based catalysts and processes for isomerization of m-xylene to p- and o-xylene along with dealkylation of ethylbenzene, and for selective ethylation of ethylbenzene to produce p-diethylbenzene are highlighted.

n-Pentane aromatization over pore size regulated MFI zeolite: Enrichment of para-xylene content in xylenes

Abstract n-Pentane aromatization over chemical vapour deposited MFI zeolite enhanced para-xylene content in xylenes as high as 99%. With increase in reaction temperature from 500 to 540°C para-xylene selectivity changed only from 99 to 93%. The aromatization over silylated MFI zeolite shows very good potential for developing a new process for converting low value C2–C5 hydrocarbon streams to industrially important benzene, toluene and para-xylene.

Transformation of ethanolamine to diazabicyclo [2. 2. 2] octane over MFI zeolite

Abstract The conversion of ethanolamine to industrially important diazabicyclo [2. 2. 2] octane (DABCO) has been studied over the ZSM-5 zeolite. This transformation takes place via the piperazine route. With the increase in reaction temperature from 325 to 400°C, ethanolamine conversion increased from 4.5 to 82%, while the DABCO selectivity decreased from 71 to 47%. The catalyst stability is lower at higher ethanolamine conversion, while it improves at lower ethanolamine conversion.