Process for producing low aromatic diesel fuel with high cetane index

A process for converting at least one olefin and at least one isoparaffin to a diesel fuel blending component comprising the steps of contacting the olefin and the isoparaffin with a catalyst comprising an acidic solid comprising a Group IVB metal oxide modified with an oxyanion of a Group VIB metal to provide a diesel fuel. Process conditions can be varied to favor the formation of gasoline, distillate, lube range products or mixtures thereof.

FIELD OF THE INVENTION 
The present invention relates to a process for producing low aromatic 
diesel fuel with a high cetane index. Particularly, the invention relates 
to a process for selectively upgrading lower boiling range feedstocks into 
higher boiling range fuels having a desired composition. 
BACKGROUND OF THE INVENTION 
Recent regulatory developments have led refiners to seek methods for 
reformulating motor fuels, including gasoline and diesel fuel, to meet 
increasingly stringent air quality requirements. These techniques include 
reducing the olefin and aromatic content of the motor fuels while 
maintaining the desired operational characteristics as predicted by the 
octane or cetane rating of the fuel. 
Alkylation is a reaction in which an alkyl group is added to an organic 
molecule. Thus an isoparaffin can be reacted with an olefin to provide an 
isoparaffin of higher molecular weight. Industrially, the concept depends 
on the reaction of a C.sub.2 to C.sub.5 olefin with isobutane in the 
presence of an acidic catalyst producing a so-called alkylate. 
Industrial alkylation processes have historically used large volumes of 
liquid Bronsted acid catalysts such as hydrofluoric or sulfuric acid under 
relatively low temperature conditions. Acid strength is preferably 
maintained at 88 to 94 weight percent by the continuous addition of fresh 
acid and the continuous withdrawal of spent acid. Liquid acid catalyzed 
isoparaffin:olefin alkylation processes share inherent drawbacks including 
environmental and safety concerns, acid consumption, and sludge disposal. 
For a general discussion of sulfuric acid alkylation, see the series of 
three articles by L.F. Albright et al., "Alkylation of Isobutane with 
C.sub.4 Olefins", 27 Ind. Eng. Chem. Res., 381-397, (1988). For a survey 
of hydrofluoric acid catalyzed alkylation, see 1 Handbook of Petroleum 
Refining Processes 23-28 (R. A. Meyers, ed., 1986). 
The typical petroleum refinery generates numerous olefinic streams, which, 
upon hydrogenation and optional fractionation, would be useful gasoline 
blending components. Examples of such streams include the olefinic 
gasoline and naphtha by-products of catalytic hydrodewaxing processes such 
as the MLDW (Mobil Lubricant Dewaxing) and MDDW (Mobil Distillate 
Dewaxing). Additional examples include olefinic gasoline cuts from delayed 
coking units (thermally cracked gasoline), as well as from catalytic 
cracking process units such as a Fluidized Catalytic Cracking (FCC) 
process. Lighter olefins may be easily dimerized or oligomerized to 
provide suitable feedstocks, for example in a process such as MOGD/MOGDL 
(Mobil Olefins to Gasoline and Distillate/Mobil Olefins to Gasoline, 
Distillate and Lube Stock), or MOCI (Mobil Olefins to Chemical 
Intermediates). Examples of processes which produce olefinic stocks 
include the processes taught in U.S. Pat. Nos. 4,922,048 to Harandi and 
4,922,051 to Nemet-Mavrodin et al. Additional examples of light olefin 
dimerization/oligomerization processes include Dimersol (light olefin 
dimerization), Isopol (selective isobutene isomerization) and Selectopol 
(selective butadiene polymerization). See Hydrocarbon Processing, Vol. 61, 
No. 5, May 1982, pp. 110-112, and Hydrocarbon Processing, Vol. 60, No. 9, 
September 1981, pp. 134-138. 
Recent regulatory changes have created an incentive for refiners to reduce 
the olefins and aromatics content of motor fuels. The final version of the 
complex model issued by the United States Environmental Protection Agency 
(US EPA) to predict the consequence of various fuel components on 
combustion emissions creates a significant penalty for high RVP components 
in gasoline. At the same time, both the US EPA and state regulatory boards 
such as the California Air Resources Board (CARB) have instituted 
regulations on diesel fuel which set an upper limit on aromatics and 
sulfur contents, and a lower limit for cetane index. In general, sulfur 
must remain below 500 ppm. U.S. EPA requires either less than 35 wt % 
aromatics or a minimum of 40 cetane index. CARB limits aromatics to 10 wt 
% unless a waiver fuel is approved. Both regulatory agencies require a 
maximum T.sub.90 of 640.degree. F. By alkylating light olefins, such as 
C.sub.3 -C.sub.5 olefins, with light isoparaffins, such as isobutane and 
isopentane, high RVP gasoline components are converted into diesel range 
fuel which meets most of the regulatory restrictions. 
SUMMARY OF THE INVENTION 
A mixed stream of isoparaffin, such as isobutane or isopentane, and 
olefins, such as propylene, butenes, pentenes, or hexenes, are passed over 
a catalyst which comprises an acidic solid comprising a Group IVB metal 
oxide modified with an oxyanion of a Group VIB metal in a fixed-bed under 
pressure at sufficiently high temperature to produce diesel range fuel. 
Process conditions can be varied to favor the formation of either 
gasoline, distillate, lube range products or mixtures thereof. The feed 
olefins can come from among many sources including FCC olefins, MTBE 
raffinate, TAME raffinate, etc. A detailed description of possible olefins 
sources is outlined in U.S. Pat. No. 5,227,552, to Chang, Hellring and 
Striebel, which is incorporated by reference as if set forth at length 
herein. The isoparaffin can come from FCC, hydrocracking, etc. process or 
by isolation of field production off-gases. Generally, C.sub.4 -C.sub.8 
isoparaffins and preferably C.sub.4 -C.sub.5 isoparaffins are used in the 
present invention. 
DETAILED DESCRIPTION 
Olefinic feedstocks suitable for use in the present invention include 
numerous olefinic streams produced by petroleum refining operations, for 
example, a cracked olefinic stream such as an olefinic gasoline boiling 
range fraction from a delayed coker process unit. The olefinic feedstocks 
generally comprises C.sub.2 -C.sub.10 olefins and preferably C.sub.3 
-C.sub.8 olefins. Delayed coking processes are taught in U.S. Pat. No. 
3,917,564 to Meyers and U.S. Pat. No. 4,874,505 to Bartilucci et al., both 
of which patents are incorporated herein by reference. 
Suitable olefinic feedstocks are also produced as byproducts in catalytic 
dewaxing processes, as described in U.S. Pat. No. 4,922,048, which patent 
is incorporated herein by reference. 
Catalytic dewaxing of hydrocarbon oils to reduce the temperature at which 
precipitation of waxy hydrocarbons occurs is a known process and is 
described, for example, in the Oil and Gas Journal, Jan. 6, 1975, pages 
69-73. A number of patents have also described catalytic dewaxing 
processes. For example, U.S. Pat. RE. No. 28,398 describes a process for 
catalytic dewaxing with a catalyst comprising a medium-pore zeolite and a 
hydrogenation/dehydrogenation component. U.S. Pat. No. 3,956,102 describes 
a process for hydrodewaxing a gas oil with a medium-pore zeolite catalyst. 
U.S. Pat.No. 4,100,056 describes a Mordenite catalyst containing a Group 
VI or a Group VIII metal which may be used to dewax a distillate derived 
from a waxy crude. U.S. Pat. No. 3,755,138 describes a process for mild 
solvent dewaxing to remove high quality wax from a lube stock, which is 
then catalytically dewaxed to specification pour point. Such developments 
in catalytic dewaxing have led to the MLDW (Mobil Lube Dewaxing) and MDDW 
(Mobil Distillate Dewaxing) process. 
Catalytic dewaxing processes may be followed by other processing steps such 
as hydrodesulfurization and denitrogenation in order to improve the 
qualities of the product. For example, U.S. Pat. No. 3,668,113 describes a 
catalytic dewaxing process employing a Mordenite dewaxing catalyst which 
is followed by a catalytic hydrodesulfurization step over an alumina-based 
catalyst. U.S. Pat. No. 4,400,265 describes a catalytic 
dewaxing/hydrodewaxing process using a zeolite catalyst having the 
structure of ZSM-5 wherein gas oil is catalytically dewaxed followed by 
hydrodesulfurization in a cascade system. The foregoing dewaxing processes 
exemplify low-severity medium-pore catalyzed dewaxing processes which 
produce a low octane naphtha by-product. Another example of a low severity 
medium-pore catalyzed conversion reaction is olefin oligomerization. 
Recent developments in zeolite catalysts and hydrocarbon conversion methods 
and apparatuses have created interest in utilizing olefinic feedstocks for 
producing heavier hydrocarbons, such as C.sub.5 + gasoline, distillate or 
lubes. These developments form the basis of the Mobil olefins to 
gasoline/distillate (MOGD) method and apparatus, and the Mobil olefins to 
gasoline/distillate/lubes (MOGDL) method and apparatus. 
In MOGD and MOGDL, olefins are catalytically converted to heavier 
hydrocarbons by catalytic oligomerization using an acid crystalline 
zeolite, such as a zeolite catalyst having the structure of ZSM-5. Process 
conditions can be varied to favor the formation of either gasoline, 
distillate or lube range products. U.S. Pat. Nos. 3,960,978 and 4,021,502 
to Plank et al. disclose the conversion of C.sub.2 -C.sub.5 olefins alone 
or in combination with paraffinic components, into higher hydrocarbons 
over a crystalline zeolite catalyst. U.S. Pat. Nos. 4,150,062; 4,211,640 
and 4,227,992 to Garwood et al. have contributed improved processing 
techniques to the MOGD system. U.S. Pat. No. 4,456,781 to Marsh et al. has 
also disclosed improved processing techniques for the MOGD system. 
U.S. Pat. Nos. 4,422,185 and 4,483,760 to Tabak disclose two-stage 
catalytic processes for upgrading hydrocarbon feedstocks, the texts of 
which are incorporated by reference as if set forth at length herein. 
The '185 patent to Tabak teaches a process for converting an olefinic 
feedstock containing ethene and heavier alkenes to a product rich in 
distillate and olefinic gasoline. Effluent from a first stage distillate 
mode reactor is flashed to separate an ethylene-rich product stream which 
is then charged to a second stage gasoline mode reactor. A disadvantage of 
the process taught by '185 is that the highly olefinic gasoline product 
stream is of a relatively low octane and reduces the gasoline pool octane. 
The '760 patent to Tabak teaches a process for catalytically dewaxing a 
middle distillate separating an olefinic by-product from the dewaxed 
distillate product stream, and upgrading a gasoline fraction at 
temperatures above 900.degree. F. In addition, the second catalytic 
reactor is operated to convert at least 10 wt. % of the olefinic 
by-product fraction to fuel oil (material boiling above 3800.degree. F.). 
Olefinic feedstocks may be obtained from various sources, including from 
fossil fuel processing streams such as gas separation units, from the 
cracking of C.sub.2 -hydrocarbons, such as LPG (liquified petroleum gas) 
from coal by-products, from various synthetic fuel processing streams, and 
as by-products from fluid catalytic cracking (FCC) and thermal catalytic 
cracking (TCC) process units. U.S. Pat. No. 4,100,218 to Chen et al. 
teaches thermal cracking of ethane to ethylene, with subsequent conversion 
of ethylene to LPG and gasoline over a zeolite catalyst having the 
structure of ZSM-5. 
Distillate products produced over a broad range of conversion conditions 
useful in the present process have a cetane index of at least about 35 and 
preferably have at least about a 45 cetane index. 
Conversion is inversely proportional with WHSV.sub.oiein on catalyst for a 
given temperature. Between 0.1 and 1.0 WHSV, reactor temperature must be 
above about 350.degree. F. in order to achieve C.sub.5 -olefin conversions 
above 90%. If temperature is restricted to 375.degree. F. to limit 
aromatics to 10 wt %, WHSV.sub.olefin on catalyst must be held below about 
0.3 to maintain 90% or greater pentenes conversion. 
The term "yield" as used herein is defined as the weight of product per 
weight of converted olefin. Total product yields above unity indicate that 
isoparaffin has been incorporated into the products. Maximum gasoline 
yield in isobutane/butene alkylation results from combination of one mole 
of each reactant to provide a yield slightly above 2.0. Ideally, a diesel 
range fuel is produced by reacting more than one mole of olefin per 
isoparaffin. For instance, a mole of isobutane must combine with two or 
three moles of butene to reach sufficient molecular weight to enter the 
boiling range of diesel fuel. Likewise, a mole of isopentane would require 
two moles of pentene to reach diesel range and would give a yield of about 
1.5. Therefore, diesel production in the present invention uses a lower 
isoparaffin/olefin molar ratio than typically is used for producing 
gasoline from a similar reactor feed stream. 
______________________________________ 
Process Conditions 
Broad Range 
Preferred Range 
______________________________________ 
Temperature 100-500.degree. F. 
200-400.degree. F 
Pressure 0-1500 psig 
50-1000 psig 
Olefin WHSV 0.01-10 0.1-5.0 
(Zeolite Basis) 
Isoparaffin:Olefin 
0.1-100 0.25-50 
Molar Ratio in 
Feedstock 
______________________________________ 
The product slates can be adjusted by varying the operating conditions. In 
general higher cetane index of the diesel range product is favored by 
higher olefin WHSV and lower temperatures in the above ranges. Gasoline 
yields are maximized at higher temperatures and higher isoparaffin:olefin 
molar ratios in the above ranges. Distillate production is favored by 
higher isoparaffin:olefin molar ratios and lower temperatures in the above 
ranges. 
The reaction temperature can be limited to obtain a range of aromatics 
content in the diesel fuel product. In cases where isopentane is reacted 
with pentenes, lower temperatures in the above ranges result in low wt. % 
aromatics in the gasoline and distillate product. To produce a diesel 
range blending stock containing less than about 10 wt % aromatics, the 
reactor temperature is preferably kept below about 375.degree. F. To meet 
the 35 wt % aromatics limit set by the US EPA, reactor temperature is 
preferably controlled below about 440.degree. F. 
In cases where an increased amount of the distillate fraction is desired 
the product boiling at a cut point up to about 450.degree. F. may be 
recycled to the contacting step. The product boiling at a cut point up to 
about 390.degree. F. may also be recycled to the contacting step. 
Optionally, the product of the present invention can be further 
hydrotreated by conventional methods to reduce product olefins by 
saturation. 
The acidic solid material useful as a catalyst in the present process may 
be prepared in accordance with U.S. patent application Ser. Nos. 
08/332,169, filed Oct. 31, 1994; 08/236,073, filed May 2, 1994; 
08/143,716, filed Nov. 1, 1993; and 08/136,838, filed Oct. 18, 1993, the 
entire disclosures incorporated herein by reference. 
The solid material described herein comprises an oxide of a Group IVB 
metal, preferably zirconia or titania. This Group IVB metal oxide is 
modified with an oxyanion of a Group VIB metal, such as an oxyanion of 
tungsten, such as tungstate. The modification of the Group IVB metal oxide 
with the oxyanion of the Group VIB metal imparts acid functionality to the 
material. The modification of a Group IVB metal oxide, particularly, 
zirconia, with a Group VIB metal oxyanion, particularly tungstate, is 
described in U.S. Pat. No. 5,113,034; in Japanese Kokai Patent Application 
No. Hei 1 1989!-288339; and in an article by K. Arata and M. Hino in 
Proceedings 9th International Congress on Catalysis, Volume 4, pages 
1727-1735 (1988), the entire disclosures of these publications are 
expressly incorporated herein by reference. According to these 
publications, tungstate is impregnated onto a preformed solid zirconia 
material to yield a solid superacid catalyst with an acid strength of Ho 
less than or equal to -14.52. 
For the purposes of the present disclosure, the expression, Group IVB metal 
oxide modified with an oxyanion of a Group VIB metal, is intended to 
connote a material comprising, by elemental analysis, a Group IVB metal, a 
Group VIB metal and oxygen, with more acidity than a simple mixture of 
separately formed Group IVB metal oxide mixed with a separately formed 
Group VIB metal oxide or oxyanion. The present Group IVB metal, e.g., 
zirconium, oxide modified with an oxyanion of a Group VIB metal, e.g., 
tungsten, is believed to result from an actual chemical interaction 
between a source of a Group IVB metal oxide and a source of a Group VIB 
metal oxide or oxyanion. 
This chemical interaction is discussed in the aforementioned article by K. 
Arata and M. Hino in Proceedings 9th International Congress on Catalysis, 
Volume 4, pages 1727-1735 (1988). In this article, it is suggested that 
solid superacids are formed when sulfates are reacted with hydroxides or 
oxides of certain metals, e.g., Zr. These superacids are said to have the 
structure of a bidentate sulfate ion coordinated to the metal, e.g., Zr. 
In this article, it is further suggested that a superacid can also be 
formed when tungstates are reacted with hydroxides or oxides of Zr. The 
resulting tungstate modified zirconia materials are theorized to have an 
analogous structure to the aforementioned superacids comprising sulfate 
and zirconium, wherein tungsten atoms replace sulfur atoms in the 
bidentate structure. It is further suggested that tungsten oxide combines 
with zirconium oxide compounds to create superacid sites at the time the 
tetragonal phase is formed. 
Although it is believed that the present catalysts may comprise the 
bidentate structure suggested in the aforementioned article by Arata and 
Hino, the particular structure of the catalytically active site in the 
present Group IVB metal oxide modified with an oxyanion of a Group VIB 
metal has not yet been confirmed, and it is not intended that this 
catalyst component should be limited to any particular structure. 
Suitable sources of the Group IVB metal oxide, used for preparing the 
catalyst, include compounds capable of generating such oxides, such as 
oxychlorides, chlorides, nitrates, oxynitrates, etc., particularly of 
zirconium or titanium. Alkoxides of such metals may also be used as 
precursors or sources of the Group IVB metal oxide. Examples of such 
alkoxides include zirconium n-propoxide and titanium i-propoxide. These 
sources of a Group IVB metal oxide, particularly zirconia, may form 
zirconium hydroxide, i.e., Zr(OH).sub.4, or hydrated zirconia as 
intermediate species upon precipitation from an aqueous medium in the 
absence of a reactive source of tungstate. The expression, hydrated 
zirconia, is intended to connote materials comprising zirconium atoms 
covalently linked to other zirconium atoms via bridging oxygen atoms, 
i.e., Zr--O--Zr, further comprising available surface hydroxy groups. When 
hydrated zirconia is impregnated with a suitable source of tungstate under 
sufficient conditions, these available surface hydroxyl groups are 
believed to react with the source of tungstate to form an acidic catalyst. 
As suggested in the aforementioned article by K. Arata and M. Hino in 
Proceedings 9th International Congress on Catalysis, Volume 4, pages 
1727-1735 (1988), precalcination of Zr(OH).sub.4 at a temperature of from 
about 100.degree. C. to about 400.degree. C. results in a species which 
interacts more favorably with tungstate upon impregnation therewith. This 
precalcination is believed to result in the condensation of ZrOH groups to 
form a polymeric zirconia species with surface hydroxyl groups. This 
polymeric species is referred to herein as a form of a hydrated zirconia. 
Suitable sources for the oxyanion of the Group VIB metal, preferably 
molybdenum or tungsten, include, but are not limited to, ammonium 
metatungstate or metamolybdate, tungsten or molybdenum chloride, tungsten 
or molybdenum carbonyl, tungstic or molybdic acid and sodium tungstate or 
molybdate. 
The present catalyst may be prepared, for example, by impregnating the 
hydroxide or oxide, particularly the hydrated oxide, of the Group IVB 
metal with an aqueous solution containing an anion of the Group VIB metal, 
preferably tungstate or molybdate, followed by drying. 
The present modified oxide material may also be prepared by treatment of a 
hydrated Group IVB metal oxide, such as hydrated zirconia, under 
sufficient hydrothermal conditions prior to contact with a source of a 
Group VIB metal oxyanion, such as tungstate. More particularly, refluxing 
hydrated zirconia in an aqueous solution having a pH of 7 or greater was 
beneficial. Without wishing to be bound by any theory, it is theorized 
that the hydrothermally treated, hydrated zirconia is better because it 
has higher surface area. It is also theoretically possible that the 
hydrothermal treatment alters surface hydroxyl groups on the hydrated 
zirconia, possibly in a manner which promotes a more desirable interaction 
with the source of tungstate later used. 
The hydrothermal conditions may include a temperature of at least 
50.degree. C., e.g., at least 80.degree. C., e.g., at least 100.degree. C. 
The hydrothermal treatment may take place in a sealed vessel at greater 
than atmospheric pressure. However, a preferred mode of treatment involves 
the use of an open vessel under reflux conditions. Agitation of hydrated 
Group IVB metal oxide in the liquid medium, e.g., by the action of 
refluxing liquid and/or stirring, promotes the effective interaction of 
the hydrated oxide with the liquid medium. The duration of the contact of 
the hydrated oxide with the liquid medium may be at least 1 hour, e.g., at 
least 8 hours. The liquid medium for this treatment may have a pH of 7 or 
greater, e.g., 9 or greater. Suitable liquid mediums include water, 
hydroxide solutions (including hydroxides of NH.sub.4.sup.+, Na.sup.+, 
K.sup.+, Mg.sup.2+, and Ca.sup.2+), carbonate and bicarbonate solutions 
(including carbonates and bicarbonates of NH.sub.4.sup.+, Na.sup.+, 
K.sup.+, Mg.sup.2+, and Ca.sup.2+), pyridine and its derivatives, and 
alkyl/hydroxyl amines. 
The present modified oxide material may also be prepared by combining a 
first liquid solution comprising a source of a Group IVB metal oxide with 
a second liquid solution comprising a source of an oxyanion of a Group VIB 
metal. This combination of two solutions takes place under conditions 
sufficient to cause co-precipitation of the modified oxide material as a 
solid from the liquid medium. Alternatively, the source of the Group IVB 
metal oxide and the source of the oxyanion of the Group VIB metal may be 
combined in a single liquid solution. This solution may then be subjected 
to conditions sufficient to cause co-precipitation of the solid modified 
oxide material, such as by the addition of a precipitating reagent to the 
solution. Water is a preferred solvent for these solutions. 
The temperature at which the liquid medium is maintained during the 
co-precipitation may be less than about 200.degree. C., e.g., from about 
0.degree. C. to about 200.degree. C. This liquid medium may be maintained 
at an ambient temperature (i.e., room temperature) or the liquid may be 
cooled or heated. A particular range of such temperatures is from about 
30.degree. C. to about 150.degree. C. 
The liquid medium from which the present catalyst components are 
co-precipitated may optionally comprise a solid support material, in which 
case the present catalyst may be co-precipitated directly onto the solid 
support material. Examples of such support materials include the material 
designated M41S, which is described in U.S. Pat. No. 5,102,643. A 
particular example of such an M41S material is a material designated 
MCM-41, which is described in U.S. Pat. No. 5,098,684. 
Support materials and/or co-catalyst materials may also, optionally, be 
co-precipitated from the liquid medium along with the Group IVB metal 
oxide and the oxyanion of the Group VIB metal. An example of a co-catalyst 
material is a hydrogenation/dehydrogenation component. 
According to an optional modification of the solid material described 
herein, a hydrogenation/dehydrogenation component is combined with the 
material. This hydrogenation/dehydrogenation component imparts the ability 
of the material to catalyze the addition of hydrogen to or the removal of 
hydrogen from organic compounds, such as hydrocarbons, optionally 
substituted with one or more heteroatoms, such as oxygen, nitrogen, metals 
or sulfur, when the organic compounds are contacted with the modified 
material under sufficient hydrogenation or dehydrogenation conditions. 
Examples of hydrogenation/dehydrogenation components include the oxide, 
hydroxide or free metal (i.e., zero valent) forms of Group VIII metals 
(i.e., Pt, Pd, Ir, Rh, Os, Ru, Ni, Co and Fe), Group IVA metals (i.e., Sn 
and Pb), Group VB metals (i.e., Sb and Bi) and Group VIIB metals (i.e., 
Mn, Tc and Re). The present catalyst may comprise one or more catalytic 
forms of one or more noble metals (i.e., Pt, Pd, Ir, Rh, Os or Ru). 
Combinations of catalytic forms of such noble or non-noble metals, such as 
combinations of Pt with Sn, may be used. The valence state of the metal of 
the hydrogenation/dehydrogenation component is preferably in a reduced 
valance state, e.g., when this component is in the form of an oxide or 
hydroxide. The reduced valence state of this metal may be attained, in 
situ, during the course of a reaction, when a reducing agent, such as 
hydrogen, is included in the feed to the reaction. 
Other elements, such as alkali (Group IA) or alkaline earth (Group IIA) 
compounds may optionally be added to or co-precipitated with the present 
catalyst to alter catalytic properties. 
The Group IVB metal (i.e., Ti, Zr or Hf) and the Group VIB metal (i.e., Cr, 
Mo or W) species of the present catalyst are not limited to any particular 
valence state for these species. These species may be present in this 
catalyst in any possible positive oxidation value for these species. 
Subjecting the catalyst, e.g., when the catalyst comprises tungsten, to 
reducing conditions, e.g., believed to be sufficient to reduce the valence 
state of the tungsten, may enhance the overall catalytic ability of the 
catalyst to catalyze certain reactions, e.g., the isomerization of 
n-hexane. 
The modified acidic oxide may be contacted with hydrogen at elevated 
temperatures. These elevated temperatures may be 100.degree. C. or 
greater, e.g., 250.degree. C. or greater, e.g., about 300.degree. C. The 
duration of this contact may be as short as one hour or even 0.1 hour. 
However, extended contact may also be used. This extended contact may take 
place for a period of 6 hours or greater, e.g., about 18 hours. When 
zirconia is modified with tungstate and then contacted with hydrogen at 
elevated temperatures, an increase in catalytic activity, e.g, for 
paraffin isomerization, has been observed. The modified acidic oxide may 
be contacted with hydrogen in the presence or absence of a hydrocarbon 
cofeed. For example, the activity of the catalyst may be increased, in 
situ, during the course of a reaction, such as hydrocracking, when a 
hydrocarbon and hydrogen are passed over the catalyst at elevated 
temperatures. 
The optional hydrogenation/dehydrogenation component of the present 
catalyst may be derived from Group VIII metals, such as platinum, iridium, 
osmium, palladium, rhodium, ruthenium, nickel, cobalt, iron and mixtures 
of two or more thereof. Optional components of the present catalyst, which 
may be used alone or mixed with the above-mentioned 
hydrogenation/dehydrogenation components, may be derived from Group IVA 
metals, preferably Sn, and/or components derived from Group VIIB metals, 
preferably rhenium and manganese. These components may be added to the 
catalyst by methods known in the art, such as ion exchange, impregnation 
or physical admixture. For example, salt solutions of these metals may be 
contacted with the remaining catalyst components under conditions 
sufficient to combine the respective components. The metal containing salt 
is preferably water soluble. Examples of such salts include chloroplatinic 
acid, tetraammineplatinum complexes, platinum chloride, tin sulfate and 
tin chloride. The optional components may also be co-precipitated along 
with the other components of the modified oxide material. 
The present modified oxide material may be recovered by filtration from the 
liquid medium, followed by drying. Calcination of the resulting material 
may be carried out, preferably in an oxidizing atmosphere, at temperatures 
from about 500.degree. C. to about 900.degree. C., preferably from about 
700.degree. C. to about 850.degree. C., and more preferably from about 
750.degree. C. to about 825.degree. C. The calcination time may be up to 
48 hours, preferably for about 0.1-24 hours, and more preferably for about 
1.0-10 hours. In a most preferred embodiment, calcination is carried out 
at about 800.degree. C. for about 1 to about 3 hours. The optional 
components of the catalyst (e.g., Group VIII metal, Group VIIB metal, 
etc.) may be added after or before the calcination step by techniques 
known in the art, such as impregnation, co-impregnation, co-precipitation, 
physical admixture, etc. The optional components, e.g., the 
hydrogenation/dehydrogenation component, may also be combined with the 
remaining catalyst components before or after these remaining components 
are combined with a binder or matrix material as described hereinafter. 
In the present catalyst, of the Group IVB oxides, zirconium oxide is 
preferred; of the Group VIB anions, tungstate is preferred. 
Qualitatively speaking, elemental analysis of the present acidic solid will 
reveal the presence of Group IVB metal, Group VIB metal and oxygen. The 
amount of oxygen measured in such an analysis will depend on a number of 
factors, such as the valence state of the Group IVB and Group VIB metals, 
the form of the optional hydrogenation/dehydrogenation component, moisture 
content, etc. Accordingly, in characterizing the composition of the 
present catalyst, it is best not to be restricted by any particular 
quantities of oxygen. In functional terms, the amount of Group VIB 
oxyanion in the present catalyst may be expressed as that amount which 
increases the acidity of the Group IVB oxide. This amount is referred to 
herein as an acidity increasing amount. Elemental analysis of the present 
catalyst may be used to determine the relative amounts of Group IVB metal 
and Group VIB metal in the catalyst. From these amounts, mole ratios in 
the form of XO.sub.2 /YO.sub.3 may be calculated, where X is said Group 
IVB metal, assumed to be in the form XO.sub.2, and Y is said Group VIB 
metal, assumed to be in the form of YO.sub.3. It will be appreciated, 
however, that these forms of oxides, i.e., XO.sub.2 and YO.sub.31 may not 
actually exist, and are referred to herein simply for the purposes of 
calculating relative quantities of X and Y in the present catalyst. The 
present catalysts may have calculated mole ratios, expressed in the form 
of XO.sub.2 /YO.sub.3, where X is at least one Group IVB metal (i.e., Ti, 
Zr, and Hf) and Y is at least one Group VIB metal (i.e., Cr, Mo, or W), of 
up to 1000, e.g., up to 300, e.g., from 2 to 100, e.g., from 4 to 30. 
The amount of iron and/or manganese which is incorporated into the present 
acidic solid may also be expressed in terms of calculated mole ratios of 
oxides, based upon the elemental analysis of the solid for the Group IVB 
metal, X, along with Mn and Fe. More particularly, this acidic solid may 
have a calculated mole ratio, expressed in terms of XO.sub.2 /(MnO.sub.2 
+Fe.sub.2 O.sub.3), of, for example, from 10 to 500. It will be 
appreciated, however, that Mn need not necessarily be in the form of 
MnO.sub.2, and Fe need not be in the form of Fe.sub.2 O.sub.3. More 
particularly, at least a portion of these components may be in the form of 
free metals or other combined forms than MnO.sub.2 or Fe.sub.2 O.sub.3 
e.g., as salts with elements other than oxygen, in any possible valence 
state for X, Mn, or Fe. Accordingly, it will be understood that the 
expression, XO.sub.2 /(MnO.sub.2 +Fe.sub.2 O.sub.3), is given merely for 
the purposes of expressing calculated quantities of X, Mn, and Fe, and is 
not to be construed as being limited of the actual form of these elements 
in the present acidic solid material. 
The amount of optional hydrogenation/dehydrogenation component may be that 
amount which imparts or increases the catalytic ability of the overall 
material to catalytically hydrogenate or dehydrogenate a hydrogenatable or 
dehydrogenatable organic compound under sufficient hydrogenation or 
dehydrogenation conditions. This amount is referred to herein as a 
catalytic amount. Quantitatively speaking, the present catalyst may 
comprise, for example, from about 0.001 to about 5 wt %, e.g., from about 
0.1 to about 2 wt %, of the optional hydrogenation/dehydrogenation 
component, especially when this component is a noble metal. 
Especially when the present catalyst includes a platinum 
hydrogenation/dehydrogenation component, this catalyst may also comprise 
up to about five weight percent of Fe and/or Mn, as measured by elemental 
analysis of the catalyst. 
The present catalyst is acidic and may be observed as being highly acidic, 
even to the extent of being a superacid. Superacids are a known class of 
acidic materials which have an acidity greater than that of 100% H.sub.2 
SO.sub.4. This level of acidity may be determined by any appropriate 
means, including the use of suitable indicators, the determination of the 
ability to protonate certain chemicals, and/or the determination of the 
ability to stabilize certain cations, especially certain carbonium or 
carbenium ions. For example, this catalyst, whether analyzed in the 
presence or absence of optional components (e.g., 
hydrogenation/dehydrogenation components) and/or binder materials, may 
have an acid strength of a superacid as measured by the color change of an 
appropriate indicator, such as the Hammett indicator. More particularly, 
the Ho acid strength of the present catalyst may have a value of less than 
-13, i.e., an "acid strength" of greater than -13. The use of Hammett 
indicators to measure the acidity of solid superacids is discussed in the 
Soled et al. U.S. Pat. No. 5,157,199. This Soled et al. patent also 
describes the Ho acid strength for certain sulfated transition metal 
superacids.

The following examples illustrate the process of the present invention. 
EXAMPLE 1 
This Example describes the preparation of Fe/WO.sub.x /ZrO.sub.2. Five 
hundred grams of ZrOCl.sub.2 .multidot.8H.sub.2 O were dissolved with 
stirring in 6.5 liters of distilled H.sub.2 O. A solution containing 7.5 
grams of FeSO.sub.4 .multidot.7H.sub.2 O dissolved in 500 ml of distilled 
H.sub.2 O was then added to the zirconyl-containing solution. A third 
solution containing 263 mL of conc. NH.sub.4 OH, 500 mL of distilled 
H.sub.2 O, and 54 grams of (NH.sub.4).sub.6 H.sub.2 W.sub.12 O.sub.40 
.multidot.x H.sub.2 O was added dropwise over a 30-45 minute period to the 
iron/zirconium mixture. The pH of the solution was adjusted to 
approximately 9 (if needed) by adding additional conc. NH.sub.4 OH 
dropwise. This slurry was then placed in the steambox for 72 hours. The 
product formed was recovered by filtration, washed with excess H.sub.2 O, 
and dried overnight at 85.degree. C. The material was then calcined in dry 
air to 825.degree. C. for 3 hours. 
EXAMPLE 2 
The catalyst used in this example was prepared in accordance with Example 1 
(8.53 g) was loaded into a stainless steel tubular reactor and bracketed 
by vycor chips which served as heat exchangers. After placing the reactor 
in a tube furnace, the catalyst was dried by heating for at least two 
hours to at least 300.degree. F. in a stream of flowing nitrogen. The 
reactor temperature was adjusted to 375.degree. F. at 600 psig, and filled 
with isopentane. A pre-mixed isopentane/pentene-l feed stream (molar 
ratio=5.0) then was introduced at a flow rate of 0.08 gm pentenes/gm 
catalyst/hr. After passing pre-mixed feed through the reactor zone for 48 
hrs, product was collected over the following 49 hrs. Product 
distributions were calculated from gc analyses of the gaseous and liquid 
products, and an additional simulated distillation ASTM 2887 of the liquid 
products. The total reactor effluent weight gave a 99.6% mass balance and 
showed the following distribution: 
______________________________________ 
Component weight % 
______________________________________ 
C.sub.3 -minus 0.02 
Isobutane 0.10 
n-Butane 0.00 
Isopentane 83.46 
n-Pentane 0.40 
Cyclopentane 0.00 
C.sub.6 -paraffin 0.02 
Methylcyclopentane 0.00 
C.sub.4 -olefin 0.02 
Butadiene 0.00 
C.sub.5 -olefin 5.60 
Cyclopentene 0.00 
C.sub.6 -olefin 0.11 
Methylcyclopentane and Benzene 
0.00 
C.sub.7 -plus 10.27 
Total 100.00 
______________________________________ 
Conversion of total pentenes was 65.8%. Calculated yields of isobutane and 
C.sub.6 -plus components per C.sub.5 -olefins converted (wt/wt) were: 
______________________________________ 
Fraction Yields 
______________________________________ 
iC.sub.4 0.01 
C.sub.6 -300.degree. F. 
0.07 
300-400.degree. F. 
0.61 
400-650.degree. F. 
0.28 
above 650.degree. F. 
0.01 
Total 0.98 
______________________________________ 
About 25 g of squalane was added to a portion of the liquid product (20.4 
g) to serve as a high boiling "chaser" during fractional 
microdistillation. After distilling the sample to a 300.degree. F. 
endpoint at ambient atmospheric pressure, the residua were fractionated 
under vacuum (about 55 torr) to obtain a cut (10.4 g) with the intended 
kerojet boiling range from 300.degree. F. to 400.degree. F. The actual 
boiling range for this cut was estimated by simulated distillation 
analysis ASTM 2887. The boiling range and product properties for this 
sample were: 
______________________________________ 
Intended cut 
300-400.degree. F. 
Boiling Range (.degree.F.) 
______________________________________ 
IBP 208 
T10 311 
T50 335 
T90 351 
EP 4030 
API gravity 55.7 
Cetane Index 51 
Cetane Number (H.sup.1 nmr) 
15 
______________________________________ 
After cooling, the residua were again distilled under vacuum (about 1-2 
torr) to obtain a cut (4.94 g) with the intended diesel fuel boiling range 
from 400.degree. F. to 650.degree. F. The actual boiling range for this 
cut was estimated by simulated distillation analysis ASTM 2887. The 
boiling range and product properties for this sample were: 
______________________________________ 
Intended cut 
400-650.degree. F. 
Boiling Range (.degree.F.) 
______________________________________ 
IBP 309 
T10 434 
T50 478 
T90 564 
EP 634 
API gravity 44.5 
Cetane Index 60 
Cetane Number (H.sup.1 nmr) 
23 
wt. % Aromatics 2.9 
______________________________________ 
Changes and modifications in the specifically described embodiments can be 
carried out without departing from the scope of the invention which is 
intended to be limited only by the scope of the appended claims.