The Behaviour of the Minerals, 3 MgO, V₂O₅, 3(Ca, Mg)O, 2V₂O₅ Produced in MgO-CaO-Al₂O₃-NiO System Catalyst in Reducing Atmosphere

Abstract

The behaviour of 3 MgO.VxO6 and 3(Ca, Mg)O.2V20if produced in MgO-CaO-A1203-NiO system catalyst used for cracking of petroleum in reducing atmospherewere examined by X-ray analysis.
In order to clarify the relations betweenthebehaviour of the produced metals and the activity decrease of the catalyst, the activities and the melting points of these vanadium compounds replaced with NiO were determind. As the results, the following reduction process were found.
3MgO.V20g --2 MgO.VO2 + O.5(MgO.V203) + O.5MgO
or 2.5MgO.V20g.s + O, 5MgO
3(Ca, Mg)O, 2 V20s -- 3(Ca, Mg)Ot2 V20g
Lattis constantsof the decomposed minerals were, 2 MgO.VO2; cubic a=8.4001, MgO eV20s; cubic a=8.4172, 3(Ca, Mg)O.2 V203; cubic a=15.0987.
It was found that all minerals had high activities while 3(Ca, Mg)O.2V20s had low melting point of 10800C, as compared with other minerals of which melting points were above 1250eC.
These facts lead to a following conclusion on the cause of decreasing of the catalytic activity.
During the oil gas craeking furnace is in air atmosphere at high temperature for short time, 3(Ca, Mg)O.2V20s in the catalyst becomes sintered or molten state and makes reduction of NiO contained in the catalyst minerals diflficult and the activity is gradually decreased.
But a direct poisoning action of vanadium to nickel catalyst is not considered.