Effect of Reduction of Pt–Sn/α-Al2O3 on Catalytic Dehydrogenation of Mixed-Paraffin Feed

Suresh Avithi Kanniappan,Udaya Bhaskar Reddy Ragula

doi:10.3390/catal10010113

Suresh Avithi Kanniappan, Udaya Bhaskar Reddy Ragula

Open Access

https://doi.org/10.3390/catal10010113

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Abstract

The effect of the Pt–Sn/α-Al2O3 catalyst reduction method on dehydrogenation of mixed-light paraffins to olefins has been studied in this work. Pt–Sn/α-Al2O3 catalysts were prepared by two different methods: (a) liquid phase reduction with NaBH4 and (b) gas phase reduction with hydrogen. The catalytic performance of these two catalysts for dehydrogenation of paraffins was compared. Also, the synergy between the catalyst reduction method and mixed-paraffin feed (against individual paraffin feed) was studied. The catalysts were examined using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA), and Brunauer–Emmett–Teller (BET) analysis. The individual and mixed-paraffin feed dehydrogenation experiments were carried out in a packed bed reactor fabricated from Inconel 600, operating at 600 °C and 10 psi pressure. The dehydrogenation products were analyzed using an online gas chromatograph (GC) with flame ionization detector (FID). The total paraffin conversion and olefin selectivity for individual paraffin feed (propane only and butane only) and mixed-paraffin feed were compared. The conversion of propane only feed was found to be 10.7% and 9.9%, with olefin selectivity of 499% and 490% for NaBH4 and hydrogen reduced catalysts, respectively. The conversion of butane only feed was found to be 24.4% and 23.3%, with olefin selectivity of 405% and 418% for NaBH4 and hydrogen reduced catalysts, respectively. The conversion of propane and butane during mixed-feed dehydrogenation was measured to be 21.4% and 30.6% for the NaBH4 reduced catalyst, and 17.2%, 22.4% for the hydrogen reduced catalyst, respectively. The olefin selectivity was 422% and 415% for NaBH4 and hydrogen reduced catalysts, respectively. The conversions of propane and butane for mixed-paraffin feed were found to be higher when compared with individual paraffin dehydrogenation. The thermogravimetric studies of used catalysts under oxygen atmosphere showed that the amount of coke deposited during mixed-paraffin feed is less compared with individual paraffin feed for both catalysts. The study showed NaBH4 as a simple and promising alternative reduction method for the synthesis of Pt–Sn/Al2O3 catalyst for paraffin dehydrogenation. Further, the studies revealed that mixed-paraffin feed dehydrogenation gave higher conversions without significantly affecting olefin selectivity.

Highlights

In daily life, olefins like propylene, butylene, and butadiene are the main building blocks for the production of high demand chemicals and polymers such as propylene oxide, cumene, acrylonitrile, isopropyl alcohol, polypropylene, and polybutadiene [1,2]
The thermogravimetric studies of used catalysts under oxygen atmosphere showed that the amount of coke deposited during mixed-paraffin feed is less compared with individual paraffin feed for both catalysts
The effect of the reducing agent on the synthesis of the Pt–Sn/α-Al2 O3 catalyst and its performance on paraffin conversion and olefin selectivity during individual and mixed-paraffin feed dehydrogenation was investigated in this work

Summary

Introduction

Olefins like propylene, butylene, and butadiene are the main building blocks for the production of high demand chemicals and polymers such as propylene oxide, cumene, acrylonitrile, isopropyl alcohol, polypropylene, and polybutadiene [1,2]. Catalysts 2020, 10, 113 cracking and dehydrogenation of individual paraffins (propane and butane) [2,4,5]. These individual paraffins are obtained from fluid catalytic cracking (FCC) unit, atmospheric, and vacuum distillation. The products of individual paraffin dehydrogenation are to be separated again, owing to their wide range (refer to Figure 1a). The feed separation, dehydrogenation of individual paraffins, and product separation during individual paraffin dehydrogenation result in both high capital and operating costs. The total operating and capital cost can be minimized if the feed to the dehydrogenation reactor is directly taken from fluidized catalytic cracking unit. The mixed-paraffin dehydrogenation process is preferable over individual paraffin dehydrogenation (refer to Figure 1b). A few works were reported on mixed feed dehydrogenation [7,8,9]

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