Hydrotreating catalysts, properties

The Exxon Donor Solvent (EDS) Process, developed by the Exxon Research and Engineering Co., differed from the typical process in that, before being recycled, the solvent was hydrogenated in a fixed-bed reactor using a hydrotreating catalyst, such as cobalt or nickel molybdate. Exxon found that use of this hydrogen donor solvent with carefully controlled properties improved process performance. Exxon developed a solvent index, based on solvent properties, which correlated with solvent effectiveness. 

To this end initial adsorption experiments were performed in order to study coke in the very first period of the catalyst life, Also aged hydrotreating catalysts were characterized. These studies combined with model compound coking and activity studies were used to obtain more insight into the properties of the deposits on the working catalyst. 

Five types of commercially available petroleum hydrotreating catalysts were evaluated. The properties of catalysts are listed in Table V. All catalysts were presulfided before being coked. 

Influence of Phosphorus on the Properties of Alumina-Based Hydrotreating Catalysts... 

Association of molybdates (tungstates) with phosphate-like structures leads to a class of compounds called heteropoly compounds or heteropoly acids of Mo or W, hereafter schematically written as Mo —P or W—P heteropoly compounds. The heteropoly anions, which may contain Mo, W, P, and other elements, are paired, both in the solid state and in solution, with cations such as H+, NH4, and Na+. Here, only some Mo —P heteropoly compounds playing an important role in hydrotreating catalysts during the catalyst preparation (impregnation) or as supported oxidic phases are discussed. The Mo — P heteropoly compounds have the following properties 18,19) ... 

The catalyst phosphorus content, the nature of the phosphorus precursor used in the preparation, and the method of phosphorus introduction all significantly affect the textural and structural properties of the final catalysts. Therefore, it is important to determine the optimum preparation and activation conditions of hydrotreating catalysts. In particular, pH of the preparative solution and the P/Mo ratio are important factors, but many other factors arc also important. 

Zeolites containing transition metai offer interesting possibilities to combine acid properties and a hydrogenation function in bifunctional catalysts. For hydrotreating, e.g. for hydrodesulfurization (HDS) and hydrodenitrogenation (HDN) reactions, both functions are essential the acid properties are provided by the zeolite, the hydrogenation activity by the sulfided transition metal cations [1,2]. It can be expected that these catalysts will be attractive alternatives to alumina supported Co-Mo and Ni-Mo hydrotreating catalysts because of their superior catalytic properties. 

Properties and catalytic activates of a hydrotreating catalyst coked to different levels with a vacuum gas oil (VGO) resulted in losses in surface area, pore volume, and catalytic activities. Comparison with previous data on anthracene-coked catalysts showed that the coke in the VGO-coked catalysts resulted in lower pore volumes and appreciable pore plugging. Deactivation of catalytic activities was generally similar, except hydrode nitrogenation was substantially lower for the-VGO coked catalysts, which was partly attributed to nitrogen on the catalyst. 

Two commercial residue hydrotreating catalysts, NiMo/Al203 and a C0M0/AI2O3, were used in this study. The properties of the catalysts are summarized in Table 1. Gas oil and Kuwait vacuum residue were used as feedstock for performance evaluation. Detailed analyses of these petroleum fractions are presented in Table 2. 

The usefulness of the of artificial neural networks as a modelling tool is apparent. A more general H-Oil product slate model can be developed by including the feed and catalyst properties. It can also easily be adapted to model the other aspects of the H-Oil process such the hydrotreating and hydrocracking reaction kinetics or coke lay down tendency in the separation units with the appropriate input and output patterns. 

Table 2 Composition and properties of typical hydrotreating catalysts...

Effects of the impregnating and drying process factors on the mechanieal properties of a PC0M0/AI2O3 hydrotreating catalyst... 

The necessity to develop hydrotreating catalysts with enhanced activity stimulates the search for alternative catalyst supports. It was shown that clay-supported transition metal sulfides can efficiently catalyze hydrodesulfurization (HDS) of thiophene [1-3]. However, the large scale application of the catalysts based on natural clays is still hampered, mainly due to the difficulties in controlling the chemical composition and textural properties. Synthetic clays do not suffer from these drawbacks. Recently, a novel non-hydrothermal approach was proposed for the synthesis of some trioctahedral smectites, namely saponite... 

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