Preparation Of Noble Metal Catalysts And Its Application In Aromatic Hydrogenation

Recently, aromatic saturation in distillate fractions has received considerable attention. A high aromatic content is associated with poor fuel quality, giving a low cetane number in diesel fuel and a high smoke point in jet fuel, and other environmental problems. New legislation has been introduced in many countries to limit aromatic content in diesel fuel. And this has led to new catalyst and process developments for aromatic saturation. Now, there are two major kind of catalyst in researching: supported metal sulfide catalyst and supported noble metal catalyst, and the process in correspondence are single- and two-stage, respectively. The latter one is superior to the former in the depth of aromatic saturation, but it is sensitive to S- and N-containing compounds in feedstock, thus, it is important to improve the sulfur tolerance of this catalyst.Others papers had been studied carefully. In others work, lots of kinds of solid acid used as the carriers of noble metal aromatic hydrogenation catalysts had been campared. And a common conclusion had been made that, for zeolite carriers, Y-type zeolite, especially the ultra-stable Y-type zeolites, and for nonzeolite carriers, the amorphous silica alumina, showed better activity and sulfur tolerance. In this work, two kinds of commercial ultrastable Y type zeolites (USY, SSY), and a kind of amorphous silica alumina (ASA) had been introduced as the carriers of noble metal catalysts. By comparison, Pd/SSY catalyst is much better than the other two in hydrogenation activity and sulfur tolerance. And the preparation condition has been optimized, that is: pore volume impregnation, Pd content 2wt.%, calcined at 500°C, reduced at 450°C.Under the analysis of the hydrogenation products by GC-MS, the toluene hydrogenation network has been put forward. There are three kinds of reaction of toluene have occurred on the surface of noble metal catalysts, that is, hydrogenation, disproportionation and isomerization.On the fixed-bed reactor, the technological conditions of model feedstock dydrotreating have been optimized, that is, reaction tempreture is 220°C, reaction pressure is 4.2MPa, LHSV is 2.7h-1, and the H₂/feedstock volume ratio is 500L/L. Under this condition, when sulfur content is 500ppm in model feedstock, the toluene conversion maintains 80.3%. This indicates that Pd/SSY catalyst has good...