SYNTHESIS, CHARACTERIZATION AND APPLICATION OF NANO-CATALYST SYSTEMS IN SOME PETROLEUM REFINING REACTIONS

Abstract

In this study nano catalytic systems composed of Pt (0.3, 0.6 and 0.9 wt %) or Ni (1, 3, 5 wt %) NPS supported on alumina or silica (commercially supplied) were synthesized via microwave assisted solution (MAS) or rotary chemical evaporation (RCE) reduction step. The catalyst samples synthesized by MAS method exhibited higher surface areas, lower pore dimensions and improved dispersion profile, than those samples prepared by RCE method, reflecting positively on their catalytic performances in n-hexane, cyclohexane and ethanol conversions. Electrical measurements ( and ’ ) confirmed that electromagnetic waves in MAS method have enhanced the even distribution of Pt NPS with increased concentration of grain boundaries, generating highly mobile electrons and phonons, compared with NPS produced by RCE method.

Alumina and silica nanopowders used as supports were also synthesized and characterized. γ-alumina had highly crystalline structure with cubic spinel lattice (space group Fd3m), while silica nanopowder exhibited amorphous nature. Both alumina (A) and silica (S1) nanopowders were modified by using 2.5 g CTAB (AC2.5 and S1C) and used as supports for Pt NPS (0.9 wt%) and Ni NPs (5wt%) reduced through MAS or (ultrasonic, US) methods. While modified alumina (AC2.5) maintained the same highly crystalline structure (with space group Fd 3m), modified silica (S1C) displayed the low angle – XRD characteristic of MCM-41 (hexagonal symmetry P6 mm) of high surface area, proper pore size distribution, well homogeneity and high thermal stability.

Catalytic performances in n-hexane, cyclohexane and ethanol conversion were variably dependent on the reduction method applied and the operating conditions of the catalytic process.

The Mil-101, as a member of Cr-MOFs, exhibited high surface area (2100 m2g-1), decreased pore radius (< 2 nm) and lower thermal stability. It displayed cubo-octahedral crystalline shape of uniform sizes (~212 nm). 0.9 wt% of Pt and 5 wt% Ni were supported on Mil-101 and reduced via RCE method. In catalytic conversion of ethanol, the 5 Ni/ Mil-101 showed higher yield of ethylene (59% at 300°C) while 0.9 Pt/ Mil-101 produced only 46% with 11% acetaldehyde at the same temperature.