CA2244368C - Hydroisomerization with reduced hydrocracking - Google Patents

Abstract

Hydroisomerization of hydrocarbon feeds is effected over a Group VIII metal containing catalyst, the catalyst also containing a hydrocracking suppressant such as a Group IB metal or sulfur.

Description

WO 97/2g106 PCT/US97fO1S85 HYDROISOMERIZATION
WITH RE)UCED HYDROCRACKING

FIELD OF THE INVENTION

This invention relates to the hydroisomerizatiion of feeds contain-ing heteroatoms, e.g., sutfisr or oxygest. More particularly, this invention relates to the hydromissumerization of feeds over a catalyst containing a Group. VIII
non-noble metal od a hydrocracking suppressant.

BACKGROUND OF THE INVENTION

Isomerization processes generally require the removal, e.g., by hydrotreating, of sulfiu and nitrogen oompounds that can rapidly deactivate or poison the rejatively expensive isomerization process catalyst. Consequently, feeds to be isomerized are first contacted with a sulfur tolerant catalyst in the presence of hydrogen for minimiziag the atnount of sulfur in the feed.

Additionally, isornerization processes, particularly those carried out in the presence of hydrogen, are effected with unsulfided catalysts. As a consequence, hydrogenolysis, e.g., hythocracicing, occurs early in the processing and produces significant amounts of qeseous products, e.g., methane or C 1-C4 hydrocarbons. A process, therefore, diat can eliminate or substantially reduce the hydrogenolysis aspect of the process can be more efficient and more economic because of increased yields of desired products and decreased yields of gaseous products.

SjjMMARY OF THE INVENTION

In accordance with this invention a hydroisomerization process is conducted in the presence of hydrogen and a catalyst comprising a Group VIA
non-noble metal and a hydrocracking suppressant. The hydrocracking snppressant may be either a Group 1B metal or a source of sulfur, usually in the fonn of a sulfided catalytically active metal, or a Group I B metal and a source of snlfur. Hydrocracking suppression can be effectively measured by suppressing methane, since hydrocracking most essily occurs through te=miaai cracking. The process is conducted with hydrocarbon containing feeds at usual hydroisomerization conditions. Generally, the process of this invention will lead to methane yields of less than about 5 wt% based on total 700 F+ conversion, preferably less than about 2 wt%, more preferably less than about 1 wt%, and still more preferably less than about 0.5 wt%. In a preferred embodunent, the catalyst also contains effective amounts of a Group VI metal.

According to an aspect of the present invention there is provided a hydroisomerization process comprising contacting a 176.7 C+ hydrocarbon-containing feed having a final boiling point of less than 566 C in the presence of hydrogen and a catalyst having an acidic functionality in the form of a silica-alumina support containing from 15 to 30 wt% of silica and comprising a cobalt component, a molybdenum component and a hydrocracking suppressant selected from copper component(s), sulfur component(s), or copper and sulfur components.

Typical hydroisomerization conditions are well known in the literature and can vary widely. For example, broad and preferred ranges for these conditions are shown in the following table:

CONDITION BROAD PREFERRED
Temperature, F 300-900(149-482 C) 550-750(288-399 C) Total pressure, psig 0-2500 300-1200 Hydrogen Treat Rate, SCFB 500-5000 2000-4000 Hydrogen Consumption Rate, SCF/B 50-500 100-300 The catalysts useful in this invention preferably contain an acid function as well as the hydrocracking suppressant. The hydrocracking suppressant may be either a Group 1B metal, e.g., preferably copper, in amounts of about 0.1-lOwt%, or a source of sulfur, or both. The source of sulfur can be provided by pre-sulfiding the catalyst by known methods, for example, by treatment with hydrogen sulfide until breakthrough occurs. The use of pre-sulfided non-noble metal catalysts for hydroisomerization is believed to be unprecedented.

2a -When feeds that are essentially free of sulfur are processed in accordance with this invention, sulfur may be stripped from a sulfided catalyst.
As a consequence, it will be preferred to add small amounts of sulfur with the feed, either continuously or periodically to maintain a desired level of sulfur in the catalyst. Catalysts containing sulfur typically have at least about 0.01 wt%
sulfur, preferably about 0.01 to 20% sulfur, preferably 0.1 to 10 wt%.

The Group VIII non-noble metals may include nickel, cobalt, hngsticn, preferably nickel or cobait, more preferably cobalt. The Group VIII
metal is usually present in catalytieally effective amounts, that is, ranging from 0.3 to 20 wt%. Preferably, a Group VI metal is incorporatied into the catalyst, e.g., molybdeeum, in amounts of abouk 1-20 wtO/6.

The acid functionality can be fiunished by a support with which the catalytic metal or metsis can be cotnposited in well known methods. The support can be any refractory oxide or mixhure of refractory oxides or zeolites or mixtures thereof. Prefwed supports aclude silica, alumina, siyica-alumina, silica-alumina-phosphates, titania, zirwnia, vanadia and other Group III, IV, V
or VI oxides, as well as Y sieves, such as ultra stable Y sieves. Preferred supports include alumina and silica-allunina, more preferably silica-alumina where the s'iliica conceatmtion of the bulk support is less than about 50 wt%, preferably less than about 35 wt%, more preferably 15-30 wt%. When alumina is used as the support, small amounts of chlorine or fluorine may be incorporated into the support to provide the acid fwictionality.

A preferred supported catalyst has surface areas in the range of about 180-400 m2/gm, prefernbly 230-350 m2/gm, and a pore volume of 0.3 to 1.0 ml/gm, pnferably 0.35 to 0.75 m1igm, a bulk density of about 0.5-1.0 g/ml, and a side crnshing strength of about 0.8 to 3.5 kg/mm.

The preparation of preferred amorphous silica-alumina microspheres for use as supports is dascribed in Ryland, Lloyd B., Tamele, M.W., and Wilson, J.N., Cracking Catalysts, Catalysis; Volume VII, Ed. Paul H.
F.snmett, Reinhold Pubtishing Corpor'ation, New York, 1960.

During hydroisomerization, the 700 F+ conversion to 700 F-ramges from about 20-80 Ya, preferably 30-70%, more preferably about 40-60'/o;
nd essentially all olefms and oxygenoted products are hydrogenated.

The feed can be any hytlrocsrbon containing matorial having a final boiling point of less than about 1050 F, (566 C). A pasticularly preferred feed is a C5+ mterial derived from a non-shifting Fischer-Tropsch process.

The feed iaatierials that aae hydroisomerized are typically waxy feeds, CS+, preferably boiling above about 350 F (177 C), more preferably above about 550 F (288 C), and are preferably obtained from a Fischer-Tropach process which produces substantially =xuW paraffins, or may be obtained from slaek waxes. Slack waxes are the by-products of dewalcing opetations where a diluent such as propane or a ketone (e.l., me:thylathyl ketone, methylisobutyl ketooe) or othw diluent is employed to promote wax crystal growth, the wax being removed from the lubricating oil by tfltntion or other suitable means.
The slack waxes are generally pwatFinic in oatutt, boil above about 604 F (315 C), preferably in the range of 600 F to 105I0 F (315-566 C) and may contain from about 1 to about 35 wt~/o oil. Waxes with lower oil contents, e.g., 5-20 wt%
are preferred; however, waxy distillstes or raflutes containing 5-45% wax mzy also be used n feeds. Slack waxes are usudUy freed of polynuclear aromatics and hetero-atom compouads by teclmiques known in the art; e.g., mild hydrotreating as described in U.S. Pateht 4,900,707, which also reduces sulfur and nitrogen levels. Feeds which contain high levels of sulfur, e.g., >30 ppm sulfur, may also be used as the catalysk described here is sulf;v tolerant. In addition, feeds such as gas field conde8sates may be used as feeds or other petroleum derived feeds with high sulfilsr levels that require hydroisomerization to ianprove its properties. A distillatiotl showing the fractional make up ( wt% for each fraction) for a typical Fischer-Tropsch process feed stock follows:

Boiling Temperature Wt% of Fraction IBP-3 0 F 160 'C 13 10506F+ 566 C+ 11 Total 100 The feed may be tnated or untreated as regarding the removal of hetitro-atoms containing compounds, e~g., sulfur and oxygen containing =
compounds. (Nitivg+en does not szem to be a problem, either its presence or absence.) However, whcn the feed is treatod, essentially all of te sulfur and oxygen should be removed, that is, to sulfur ltvels of less than about 10 wppm, -S-and oxygen levels of less ahan about 10 wppm. Such feeds are characterized by the subsdmtW absence of sulfur and oxygen. Hydrotreating is effected by any of the weU knovrm hydrotreating, e.g., hydrodesulfurization, processes known in the literature.

The catalyst can be prepared by any well known method, e.g., in>~eguation with an aqueous salt, iWpient wetne:ss technique, followed by drying at about 125-150 C for 1-24 hlMm, calcination at about 300-500 C for about 1-6 hours, reduction by treatmeht with a hydrogen or a hydrogen containing gac, and, if desired, sulfiditig by treatment with a sulfur containing gas, e.g., H2S at elevated temperatureds. The catalyst will then have about 0.01 to 10 wt'/o sulfur. The metals can be composited or added to the catalyst either seacially, in any order, or by co-impregnation of two or more metals.

The following examples will serve to illustrate, but not limit this invention.

Exwnple 1 A conunercial Co-Mo catalyst on a Si02-A1203 support containing 20-30 wt% bulk silica was reduced at 370 C for 3 hours in hydrogen. The catalyst was used to hydroisomerize n-heptane as a model compound relmesenting the more refractory para#~'ins present in condensate. The results of the isomerization test are found in the following table.

EnMpk?

The Co-Mo catalyst of Example 1 was impregnated with an aqueous solution of copper nitrate to introduce 0.3 wr'/o Cu. The catalyst was caicined in air at 370 C and reduced in hydrogen at 370 C for 3 hours. The Co-Mo-Cu catalyst was used to hydroisoinerize n-heptane. The results are pnsented in 1he table below.

Ecam le 3 The Co-Mo catalyst of Example 1 was reduced in hydrogen at 370 C for 3 hours and brealcthrough sulfided with dilute H2S in H2 at 370 C.
The catalyst was H2 stripped at the same temperature for 2 hours to remove any ohaanisorbed H2S. The Co-Mo-S cat*st was used to hydroisomerize n-heptane. The results are included in the following table.

The catalyst of Example 1, while active for hydroisomenization, has extreanely high hydrocracking activity as evidenced by vety high methane and o-batsne yields and the destruction of nora-al and isoheptanes. Liquid yield is ddeeresud to a value < 70 wt'/o.

The catalysts of this invention, Co-Mo-Cu and Co-Mo-S, the csialysts of Examples 2 and 3, are pre*rred hydroisosnerization catalysts on the basis of higher sekctivity to isomerizea product and subbatm-tially decreaaed hymcracking activity. In both cases the yields of liquid product exceed 92 wt /a, and the formation of isotaptanes is ro"hly 40% geater than that of Example 1.
Wbile not shown in the table, the combination of sulfur with Cu would offer additional yield and selectivity credits relative to those of Examples 2 and 3.

ISOMERIZATION OF HEPTANE WITH
SULFIDED CO-MO AND CO-MO-CU CATALYSTS
n-Heptane, 425 C, 100 psig. 5 W/H/W, H2/Oil=6 ~~LE 1 2 3 Catalyst Co-Mo Co-Mo-Cu Co-Mo-S
C 1 6.4 1.4 0.2 i-C4 0.5 0.3 0.1 n-C4 4.0 0.8 1.0 n-C7 56.3 77.5 77.7 2,4-DMP 0.4 0.6 0.4 2-Me-Hex 4.6 6.2 6.5 3-Me-Hex 6.4 8.6 9.6 i-C?'s 11.4 15.4 16.6

Claims (10)

CLAIMS:

1. A hydroisomerization process comprising contacting a 176.7°C+
hydrocarbon-containing feed having a final boiling point of less than 566°C in the presence of hydrogen and a catalyst having an acidic functionality in the form of a silica-alumina support containing from 15 to 30 wt% of silica and comprising a cobalt component, a molybdenum component and a hydrocracking suppressant, the hydrocarbon suppressant being copper component(s), one or more sulfur component(s), or copper and sulfur components.

2. The process of claim 1, wherein the sulfur hydrocracking suppressant is provided in the form of a pre-sulfided catalyst.

3. The process of claim 1 or 2, wherein the catalyst contains in a range of 0.01 to 20 wt% sulfur.

4. The process of any one of claims 1 to 3, wherein sulfur is present on the catalyst in an amount in a range of about 0.1 to 10 wt%.

5. The process of any one of claims 1 to 4, wherein the cobalt content of the catalyst is in the range of from 0.5 to 20 wt%.

6. The process of any one of claims 1 to 5, wherein the molybdenum content of the catalyst is in the range of from 1.0 to 20 wt%.

7. The process of any one of claims 1 to 6, wherein the feed is, or comprises, a C5+ material derived from a non shifting Fischer-Tropsch process.

8. The process of any one of claims I to 5, wherein the feed is a slack wax having a boiling point in the range of 315-566°C.

9. The process of claim 8, wherein the feed is one which has >30ppm of sulfur.

10. The process of any one of claims 1 to 5, wherein the feed is a gas field condensate.