Understanding the Mechanisms of Decalin Hydroprocessing Using Comprehensive Two-Dimensional Chromatography

Abstract

Comprehensive two-dimensional gas chromatography (GC × GC) is a powerful technique for analyzing mixtures of hundreds of hydrocarbons. In the context of fuel upgrading through selective ring opening, we propose a methodology for GC × GC analysis of complex mixtures resulting from the hydroprocessing of a single model gas oil compound, decalin, over two different types of bifunctional catalysts based on a transition-metal sulfide (NiWS on amorphous silica–alumina) or a noble metal (Ir on La,Na–Y zeolite). The reactions lead to several products families, the dominant ones being ring-opening products (ROPs) and skeletal-isomerization products (SkIPs). First, it is shown that the ROP distribution can be characterized in terms of isomerization degree by using the cumulative distribution function of the GC × GC (GC Image) software. Second, in a more quantitative approach, the products families have been subdivided into chemical groups, according to the isomerization degrees of the individual compounds, which were almost all tentatively identified by two-dimensional gas chromatography coupled with mass spectrometry (GC × GC-MS) through the use of literature data. This allows us to thoroughly analyze the influence of the catalyst nature and the presence of H2S in the reactant feed on the products distribution, and thereby gain insight into the mechanism of decalin hydroconversion over bifunctional catalysts. In particular, it is shown that metal sulfidation suppresses the metal-catalyzed C–C hydrogenolysis pathway at the benefit of undesirable acid-catalyzed isomerization steps. The methodologic work presented here for decalin is believed to be applicable to other bicyclic (naphthenic or aromatic) compounds.

Influence of the Ir content and the support on the thiotolerance of the Ir/SiO2‐Al2O3 catalysts for selective ring opening of decalin

“…Blanco et al emphasize that the addition of S on supported noble metals causes changes in the mechanism of reaction because of the poisoning of the metal function. [ 69 ]…”

Transition metal sulfides on zeolite catalysts for selective ring opening

“…Considering C10 compounds, the dominant ones are isomers (SkIPs) and ring-opening products (ROPs) with a small contribution of 2ROPs, those families being well discriminated by comprehensive GC [27]. Considering that the C10 compounds have the same response factor for FID, the ROP selectivity Srop was obtained from the quantification C10 isomers whose identification have been described in detail in Ref [28]. Thus, 24 SKiPs, 29 1ROPs and 11 2ROPs compounds have been identified.…”

Selective ring opening of decalin over bifunctional RuS2/zeolite catalysts

“…Analytical details can be obtained from Ref. [34]. An example of a GC × GC chromatogram is given in Fig.…”

“…The distribution of light products is characteristic of cationing hydrocracking mechanism (M shape) [14]. In fact, the introduction of much lower H 2 S partial pressure is detrimental to the hydrogenolytic properties of the metal as it has been demonstrated in the case of Ir on zeolites [34]. This catalyst was therefore not studied further.…”