Preparation hydrotreating catalysts

As mentioned in Section III, phosphomolybdate heteropoly compounds have recently been used as precursors for preparing hydrotreating catalysts. 

Volume 50 Hydrotreating Catalysts. Preparation, Characterization and Performance. 

A fairly large number of patents has been issued describing the application of aluminum-deficient Y zeolites in different areas of catalysis. Ultrastable Y zeolites have been used in the preparation of catalysts applied in hydrocarbon cracking, e.g. (94,95) hydrocracking, e.g. (96,97) hydrotreating, e.g. (98) and disproportionation, e.g. (99). 

Hydrotreating Catalysts. Preparation, Characterization and Performance. Proceedings of the Annual International AlChE Meeting, Washington, OC, November 27-December 2, 1988 edited by M. L. Occalli and R. G. Anthony... 

Anthony. R. and M.L. Occelli Hydrotreating Catalysts—Preparation, Chatucteri-ration and Performance. Elsevier Science, New York. NY, 1989. 

SELECTIVE PREPARATION OF CHLOROANILINES FROM CHLORONITROBENZENES OVER SULFIDED HYDROTREATING CATALYSTS... 

Alumina-supported Co- and Ni-promoted molybdenum sulphide hydrotreating catalysts are the main workhorses in many refineries and have, therefore, attracted a lot of attention from catalytic chemists. They are usually prepared via co-impregnation, i.e. pore-volume impregnation with both Mo and the promoter atom present in solution. After drying and calcining, the catalyst manufacture is complete, but it has to be sulphided before use. Traditionally, this is done in situ... 

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) ... 

Ml. Preparation of Alumina-Based Hydrotreating Catalysts Containing Phosphorus, Molybdenum, and Cobalt or Nickel... 

Fig. 13. Procedures for the preparation of alumina-based hydrotreating catalysts containing phosphorus, molybdenum, and cobalt or nickel, a. Impregnation or equilibrium adsorption method (coimpregnation) b, impregnation or equilibrium adsorption method (sequential impregnation) c, precipitation or hydrogel method d, sol-gel method [adapted from Iwamoto and Grimblot 40). ...

Some research groups have used heteropoly compounds as Mo-P precursors for preparation of hydrotreating catalysts (22, 25, 42). As de-... 

Thus, questions remain the large differences in acidity reported here might be attributed both to the nature of the catalysts (affected by the method of preparation, the loadings of the different elements, and whether the catalysts are in the oxide or sulfided states) and to the method of acidity measurement (total acidity determination or selective titration of acid sites with a specific strength). Furthermore, the protocols for measurement (e.g., the temperature and duration of outgassing before acidity determination) may also affect the results. Therefore, it can be inferred that some standardization of measurement conditions is required to reach consensus regarding the influence of phosphorus on the acidity of hydrotreating catalysts. 

The advantages of phosphorus addition to catalyst formulations found in patents can be approximately categorized as follows (i) optimization of the catalyst pore structure by addition of phosphorus to be applied with certain types of feedstocks such as residual oil, (ii) optimization of the dispersion of Co(Ni) I Mo-containing phases by the presence of phosphorus, (iii) optimization of synergistic effects resulting from complex chemical combinations of phosphorus and other incorporated elements, (iv) optimization of catalyst preparation by use of specific phosphorus precursors, and (v) the use of phosphorus-containing catalysts under specific reaction conditions or processes as well as their use in combination with other hydrotreating catalysts. 

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. 

N L Occelli and R G Anthony, Hydrotreating Catalysts Preparation, Characterization and Performance, Elsevier, Amsterdam 1989... 

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