Abstract

To improve the oxidative stability of biodiesel fuel (BDF), the polyunsaturated fatty acid methyl esters (poly-FAME) presented in commercial palm oil-derived biodiesel fuel (palm-BDF) were selectively hydrogenated to monounsaturated fatty acid methyl esters (mono-FAME) under a mild condition (80 °C, 0.5 MPa) using activated carbon (AC)-supported Pd catalysts with a Pd loading of 1 wt.%. The partially hydrotreated palm-BDF (denoted as H-FAME) which has low poly-FAME components is a new type of BDF with enhanced quality for use in high blends. In this study, we reported that the chemical states and particle sizes of Pd in the prepared Pd/AC catalysts were significantly influenced by the Pd precursors, Pd(NO3)2 and Pd(NH3)4Cl2, and thus varied their hydrogenation activity and product selectivity. The 1%Pd/AC (nit) catalyst, prepared using Pd(NO3)2, presented high performance for selective hydrogenation of poly-FAME into mono-FAME with high oxidation stability, owning to its large Pd particles (8.4 nm). Conversely, the 1%Pd/AC (amc) catalyst, prepared using Pd(NH3)4Cl2, contained small Pd particles (2.7 nm) with a little Cl residues, which could be completely removed by washing with an aqueous solution of 0.1 M NH4OH. The small Pd particles gave increased selectivity toward unwanted-FAME components, particularly the saturated fatty acid methyl esters during the hydrogenation of poly-FAME. This selectivity is unprofitable for improving the biodiesel quality.

Highlights

  • IntroductionHigh contents of saturated fatty acid methyl esters (sat-FAME) worsen the cold flow properties of biodiesel fuel (BDF), and that limits the uses of BDF at low temperatures [4,5,6]

  • We evaluated the oxidative stability and cold flow properties of the H-FAME samples obtained over the two types of catalysts to compare the effects of the Pd precursor on the catalytic performance of the catalysts

  • The structural properties of activated carbon (AC) and the Pd/AC catalysts are presented in Table 1, in comparison to a commercial Pd/AC catalyst with a Pd loading of 5 wt.%

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Summary

Introduction

High contents of saturated fatty acid methyl esters (sat-FAME) worsen the cold flow properties of BDF, and that limits the uses of BDF at low temperatures [4,5,6]. In ASEAN, commercial palm oil-derived biodiesel fuel (palm-BDF) is a major source for blending with petroleum diesel. It generally contains approximately 10% of poly-FAME, mostly methyl linoleate with low oxidation stability (denoted as C18:2 ), approximately 40% of monounsaturated fatty acid methyl esters (mono-FAME), mostly methyl oleate with high oxidation stability and suitable cold flow properties (denoted as C18:1 ), and approximately 50% of sat-FAME, mostly methyl palmitate with low cold flow properties (denoted as C16:0 ) [6]. The high blends of B10-30 fuels formulated by HFAME (10–30 vol%) with petro-diesel are suitable for diesel-engine vehicles with high safety and security

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