Role of Active Chromium Species on Different Support for Dehydrogenation of Propane

Abstract

Dehydrogenation of propane (DHP) was studied over a series of Cr 2 O 3 -Al 2 O 3 and Cr 2 O 3 -SiO 2 catalysts, prepared by incipient wetness impregnation and sol gel (SG) method, respectively, to gain a better understanding of the nature and distribution of chromium (Cr) species and their catalytic function. To this end, the catalysts were characterized by N 2 -physisorption and X-ray diffraction (XRD). N 2 -physisorption analysis of Cr 2 O 3 -SiO 2 showed the relatively higher surface area of 391.1 m 2 /g, compared with Cr 2 O 3 -Al 2 O 3 of 224.3 m 2 /g. The combination method of sol gel and sonothermal also produced smaller particles size of catalyst with higher microporosity of 23.5% and smaller pores size of 6 nm. The good surface properties of Cr 2 O 3 -SiO 2 enabled the high conversion of propane of 55% at 550 °C. At higher temperature of 600 °C, the Cr species might be reduced into lower oxidation state and inhibit the catalytic behavior to produce hydrogen.Keywords: chromium (II) oxide, thermodynamic consideration, sonothermal, catalytic behavior, hydrogen energy Abstrak Tindak balas penyah-hidrogenan gas propana (DPP) telah dikaji menggunakan beberapa siri mangkin Cr 2 O 3 -Al 2 O 3 dan Cr 2 O 3 -SiO 2 yang dihasilkan melalui kaedah impregnasi basah dan sol gel (SG) method, untuk memahami sifat dan serakan spesies logam Cr dan fungsi pemangkinannya. Dalam kajian ini, mangkin diciri menggunakan kaedah jerapan gas N 2 dan pembelauan sinar X (XRD). Analisis jerapan N 2 bagi mangkin Cr 2 O 3 -SiO 2 menunjukkan ia mempunyai luas permukaan yang paling tinggi sebanyak 391.1 m 2 /g, berbanding mangkin Cr 2 O 3 -Al 2 O 3 sebanyak 224.3 m 2 /g. Kombinasi kaedah sol gel (SG) dan sonotermal menghasilkan mangkin yang bersaiz lebih kecil dengan keporosan mikro sebanyak 23.5% dan saiz liang sebanyak 6 nm. Ciri-ciri permukaan yang baik ditunjukkan oleh mangkin Cr 2 O 3 -SiO 2 menyumbang kepada aktiviti tindak balas yang baik dengan peratus penukaran propana yang tinggi sebanyak 55% pada suhu 550 °C. Pada suhu tindak balas 600 °C pula, spesies logam Cr boleh terturun kepada keadaan pengoksidaan yang lebih rendah dan merencat tindak balas pemangkin bagi menghasilkan gas hidrogen sebagai produk utama.Kata kunci: kromium (II) oksida, pendekatan termodinamik, sonotermal, sifat pemangkinan, tenaga hidrogen ISSN -2506 Wan Nor Roslam et al: ROLE OF ACTIVE CHROMIUM SPECIES ON DIFFERENT SUPPORT FOR DEHYDROGENATION OF PROPANE 120Introduction Propane is produced as a by-product of two other processes, natural gas processing and petroleum refining. The processing of natural gas involves removal of butane, propane, and large amounts of ethane from the raw gas, in order to prevent condensation of these volatiles in natural gas pipelines. Commonly, the dehydrogenation of propane can produce propene and hydrogen as a greener and future fuel sources and carried higher energy [1]. The reaction conditions play a major role to direct the reaction route and selected products. It is possible to produce hydrogen by catalytic dehydro...