Mineral oils: processes and products – Refining – Sulfur removal
Reexamination Certificate
2001-04-06
2004-06-08
Griffin, Walter D. (Department: 1764)
Mineral oils: processes and products
Refining
Sulfur removal
C208S243000, C208S244000, C208S248000, C208S20800M, C208S213000, C208S217000, C208S21600R, C208S134000, C208S135000, C208S136000, C208S137000
Reexamination Certificate
active
06746598
ABSTRACT:
The present invention relates to the use of a catalytic system comprising a metal of group VIII, a metal of group VI, a metal oxide as carrier and suitable quantities of a component selected from a, zeolite of the FER type, phosphorous, and a mixture thereof, in upgrading of hydrocarbons boiling in the naphtha range containing sulfur impurities, namely in hydrodesulfurization with contemporaneous skeleton isomerization of olefins contained in said hydrocarbons and/or with reduction of olefins hydrogenation, carried out in a single step.
This catalytic system can be used in particular for upgrading of hydrocarbons boiling in the naphtha range deriving from cracking processes, preferably of hydrocarbons boiling in the naphtha range derived from FCC (fluid catalytic cracking).
In fact hydrocarbons boiling in the naphtha range from FCC (i.e. gasoline cut )are used as a component in the blending of reformulated gasolines. For this purpose, it must have a high octane number and also a low sulfur content, in compliance with the limits of the law, which are becoming more and more restrictive, to reduce the emission of contaminants. The sulfur present in the gasoline pool in fact mainly derives (>90%) from the gasoline cut deriving from FCC. This cut is also rich in olefins which have a high octane number. Hydrogenation processes suitable for desulfurizing also result in the hydrogenation of the olefins present and consequently cause a considerable reduction in the octane number (RON and MON). The necessity has therefore been felt for identifying a catalytic system which, combined with suitable hydrodesulfurization conditions, diminishes the sulfur in the hydrocarbons boiling in the naphtha range and at the same time reduces to the minimum the deterioration in the octane qualities (RON), which can be achieved for example by the skeleton isomerization of olefins present and/or by the inhibition of hydrogenation of olefins double bond.
The use of zeolites with medium pores as isomerization catalysts and the consequent octane recovery of loadings previously subjected to desulfurization, are already known (U.S. Pat. No. 5,298,150, U.S. Pat. No. 5,320,742, U.S. Pat. No. 5,326,462, U.S. Pat. No. 5,318,690, U.S. Pat. No. 5,360,532, U.S. Pat. No. 5,500,108, U.S. Pat. No. 5,510,016, U.S. Pat. No. 5,554,274, U.S. Pat. No. 5,599,439). For these processes, to obtain hydrodesulfurization with a reduced octane loss, it is necessary to operate in two steps using specific catalysts and reactors.
U.S. Pat. No. 5,378,352 describes a process in a single step for desulfurizing hydrocarbon fractions which boil within the range of gasolines by means of a catalyst comprising a metal of group VIII, a metal of group VI, a zeolite having a Constraint Index ranging from 1 to 12, and a metal oxide as a binder, at a process temperature which is preferably higher than 340° C. Suitable zeolites which can be used in this invention are the following: ZSM-5, ZSM-11, ZSM-22, ZSM-23, ZSM-35, ZSM-48, ZSM-50, MCM-22 and mordenite. The use of MCM-22 is indicated as being particularly preferred. In the example a catalyst containing MCM-22 in a high percentage with respect to the total weight of the catalyst (54 wt %) is used and the example relates to “heavy naphtha”, a feed cut from FCC gasoline with a high S content, but poor in olefins and consequently not particularly subject to reduction in the octane number as a result of hydrogenation. The suitable process conditions are: temperature higher than; 340° C., pressure about 4 to 100 atm, LHSV 0.5 to 10 h−1, ratio between hydrogen and the hydrocarbon feed comprised between 93 and 940 std 1/1.
Catalytic materials containing metals of groups VI and VIII, a refractory carrier and a zeolite, for example ZSM-35, are described in EP 442159, EP 437877, EP 434123, for the isomerization and disproportionation of olefins; in U.S. Pat. No. 4,343,692 for hydrodewaxing, in U.S. Pat. No. 4,519,900, for hydrodenitrogenation, in EP 072220, for a two-step process comprising dewaxing and hydrodesulfurization; in U.S. Pat. No. 4,959,140 for a two-step hydrocracking process.
In addition a catalyst is known consisting of Co, 3.5% wt, Mo, 12.8% wt, alumina, 69.8% wt, and P, 2.84% wt, used for deep desulfuration of distillates.
Materials consisting of Mo, Co, alumina and zedlites of the MFI type combined with elements of group IIIA and VIB and also containing phosphorous are described in U.S. Pat. No. 5,576,256.
We have now unexpectedly found that it is possible to desulfurize hydrocarbons boiling in the naphtha range such as full range gasolines containing sulfur and olefins, deriving for example from FCC, with high conversion values, also at lower temperatures and pressures than those preferably used in the prior art, with contemporaneous skeleton isomerization of olefins and/or with very low extent of hydrogenation of olefins double bond, by means of a catalyst comprising a metal of group VIII, a metal of group VI, a metal oxide as carrier and suitable quantities of a component selected from a zeolite of the FER type, phosphorous and mixture thereof. The skeleton isomerization of olefins and/or the very low extent of hydrogenation of olefins double bond allow to obtain desulfurization of hydrocarbon boiling in the naphtha range with very low losses of RON (research octane number) and MON (motor octane number).
These results are not only obtained in the desulfurization of hydrocarbon cuts which boil within the range of “heavy naphtha” (130°-250° C.), i.e. cuts poor in olefins, but also in the case of “full range naphtha” feeds which boil within the, range of 35°-250° C., i.e. in the case of cuts rich in olefins.
A first object of the present invention therefore relates to a process for desulfurizing hydrocarbons which boil within the range of 35° to 250° C., containing olefins and more than 150 ppm of sulfur, with possible skeleton isomerization of olefins, using a catalyst which comprises a metal of group VIII, a metal of group VI, a metal oxide as carrier and a component A selected from:
a) zeolite belonging to the FER type, in a quantity ranging from 5 to 30% by weight with respect to the total weight of the catalyst,
b) phosphorous in a quantity ranging from 0.1 to 10% weight, preferably from 1 to 5% wt, with respect to the total weight of the catalyst,
c) mixtures thereof,
where when the component A is only phosphorous either the catalyst is obtained by impregnation of the metal oxide carrier with an aqueous solution of H
3
PO
4
followed by impregnation with an aqueous solution of the metal of group VIII and an aqueous solution of the metal of group VI, or the catalyst is obtained by drying and calcination of a gel obtained mixing an alcohol dispersion containing a soluble salt of the metal of group VIII and an organic source of aluminum with an aqueous solution containing a soluble salt of the metal of group VI and H
3
PO
4
, or the catalyst is obtained by impregnation with an aqueous solution of H
3
PO
4
of a gel, dried and calcined, obtained mixing an alcohol dispersion containing a soluble salt of the metal of group VIII and an organic source of aluminum with an aqueous solution containing a soluble salt of the metal of group VI.
The weight percentage of phosphorous refers to contents expressed as elemental phosphorous; in the final catalyst phosphorous is in form of oxide.
When the catalyst contains a zeolite of the FER type, this zeolite is present in a much lower quantity than that contained in the catalysts used in U.S. Pat. No. 5,378,352. Using this catalytic system characterized by a low content of FER zeolite, excellent desulfurization conversions are obtained, with contemporaneous skeleton isomerization of olefins, even at temperatures which are not high, at which there are lower losses of RON and MON than those caused by the same FER zeolites when used at quantities as high as those used in U.S. Pat. No. 5,378,352 both in the conditions of said patent and in the conditions selected in the present invention.
When the catalyst used in process of the present inventio
Albertos Fernando
Arrigoni Virginio
Atanes Evangelina
Cholley Thierry
Panarello Febronio
Arnold Jr. James
Enitecnologie S.p.A.
Griffin Walter D.
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
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