THIS INVENTION relates to the dehydrogenation of hydrocarbon feedstocks. It relates in particular to a process for dehydrogenating a hydrocarbon feedstock.

According to the invention, there is provided a process for dehydrogenating a hydrocarbon feedstock, which process includes contacting the hydrocarbon feedstock with a catalyst obtained by calcining a mixed metal oxide system of Formula (1) Fe (II) SMg (II) tZn (II) wCu (II) xMn (II) y Co (II) z] [Cr (III) aFe (III) bGa (III) cAl (III) d Au (III) e] [OH] p [X] qXYH2O (1) where (i) s, t, w, x, y and z each denotes an integer or a decimal number from 0 to 20, 0 ; (ii) the sum of r, s, t, w, x, y and z is from 3, 0 to 20, 0 ; (iii) a, b, c, d and e each denotes an integer or a decimal number from 0 to 2, 0 ; (iv) the sum of a, b, c, d, e and f is from 1, 0 to 5, 0 ; (v) p denotes an integer from 4 to 44 ; (vi) X denotes any anion with a charge of either 1 or 2 ; (vii) q denotes an integer or a decimal number from 0, 5 to 2, 0 ; and (viii) Y denotes an integer from 3 to 7,

thereby to dehydrogenate at least one hydrocarbon in the hydrocarbon feedstock.

While the hydrocarbon feedstock will normally be a linear alkane or a mixture of linear alkanes, it may instead, or additionally, be or include at least one cyclic alkane, at least one olefin, at least one alkylated benzene, or at least one saturated hetero- atom hydrocarbon compound such as a nitrogen containing hydrocarbon compound, a sulphur containing hydrocarbon compound and/or a chlorine containing hydrocarbon compound. The feedstock may also comprise a mixture of two or more of such components or compounds. In other words, the hydrocarbon that is dehydrogenated may be a linear alkane, a cyclic alkane, an olefin, an alkylated benzene, and/or a saturated hetero-atom hydrocarbon compound.

The hydrocarbon feedstock may be derived from crude oil.

Instead, however, it may be Fischer-Tropsch derived. By 'Fischer-Tropsch derived'is meant a feedstock obtained by reacting a synthesis gas comprising mainly carbon monoxide and hydrogen in the presence of a suitable Fischer-Tropsch catalyst, normally a cobalt, iron, or cobalt/iron Fischer-Tropsch catalyst, at elevated temperature in a suitable reactor, which is normally a fixed or slurry bed reactor, thereby to obtain a range of products, including products or components suitable for use as the hydrocarbon feedstock in this invention. The products from the Fischer-Tropsch reaction must then usually be worked up to obtain individual products such as a feedstock suitable for use in the present invention.

The feedstock may comprise hydrocarbons having six carbon atoms, ie C6 hydrocarbons, and/or hydrocarbons having less than six carbon atoms, eg C2-C5, and/or hydrocarbons having more than six

carbon atoms, eg C7-C40. The feedstock may, for example, be naphtha.

The hydrocarbon will normally be dehydrogenated to form either an olefinic compound or an aromatic compound, depending on the carbon chain length of the hydrocarbon. Thus, if the hydrocarbon has 5 or fewer carbon atoms in its carbon chain, an olefin compound will usually be formed ; however, if it has more than 5 carbon atoms in its carbon chain, an aromatic compound will usually be formed. Thus, when an aromatic compound or hydrocarbon is formed, it may be benzene or a substituted benzene such as ethylbenzene, xylene, styrene, linear alkyl benzene, or the like, depending on the feedstock, the catalyst composition, and the reaction conditions. A mixture or range of aromatic or olefinic hydrocarbons can also be formed.

The contacting of the hydrocarbon feedstock with the catalyst may be effected at a pressure of from 100 to 600 kPa (a), eg at about 200 kPa (a), and at a temperature of from 350°C to 700°C, preferably from 450°C to 650°C. The contacting may be effected in a non-oxidizing atmosphere, ie in an inert or reducing atmosphere. Preferably, the contacting is effected in a reducing atmosphere provided by synthesis gas comprising mainly carbon monoxide and hydrogen.

The mixed metal oxide system of the catalyst may be that obtained by dissolving water-soluble salts of the desired metals in water in proportions corresponding to the desired composition of the mixed oxide system, to obtain a mixed metal salt solution ; combining the mixed metal salt solution with an aqueous solution containing X anions ; aging the resultant alkaline mixture, to allow a precipitate to form ; and filtering, washing and drying

the precipitate, with the precipitate thus constituting the mixed metal oxide system of Formula (1).

X can, at least in principle, be any organic or inorganic anion having a charge of 1 or 2. For example, X can be carbonate, sulphate, nitrate, chromate or oxalate. The X anion may be used, in the aqueous solution of the X anion, in combination with an alkali metal such as lithium, sodium, potassium, rubidium, cesium, or mixtures thereof. For example, an alkaline aqueous solution containing ammonium-and/or alkali metal- carbonate/hydroxide can be used for combining with the mixed metal salt solution to obtain the precipitate.

Prior to the aging and/or during the aging, the alkaline mixture is usually stirred. The aging may be effected under hydrothermal conditions, and can thus be effected at a temperature from 15°C to 200°C. The aging is typically effected for a period from 30 minutes to 96 hours, to allow the precipitate to form.

The drying of the precipitate can be effected at a temperature from 80°C to 150°C.

The calcination of the precipitate or mixed metal oxide system to obtain said catalyst can be effected at a temperature from 250°C to 700°C, preferably from 250°C to 550°C. The catalyst has a hydrotalcite structure in which metals are incorporated in the hydrotalcite structure, ie the metals are not merely supported on a catalyst support.

The calcined mixed metal oxide system of Formula (1) will, prior to contacting it with the hydrocarbon feedstock, be activated through reduction thereof by exposing it to a reducing atmosphere at elevated temperature. The reducing atmosphere may, in

particular, be provided by synthesis gas comprising mainly carbon monoxide and hydrogen. The elevated temperature at which the reduction takes place is typically the same as the temperature at which the contacting of the hydrocarbon feedstock with the catalyst takes place, ie 350°C to 700°C, as hereinbefore described. The reduction may be continued for a desired period of time until a desired degree of reduction or activation has occurred, typically for from 5 to 12 hours.

The catalyst may be of solid particulate form, and is in the form of a fixed bed located in a reaction zone, with the hydrocarbon feedstock being fed continuously into the reaction zone and the dehydrogenated hydrocarbon being withdrawn continuously from the reaction zone.

The catalyst, when spent, may be regenerated by contacting it with a mixture of oxygen and inert gas at a temperature from 400°C to 600°C.

The invention will now be described in more detail with reference to the following non-limiting examples and to Figure 1 which shows a plot of conversion and aromatic selectivity against feedstock sulphur concentration : EXAMPLE 1 A MgCr material, or a mixed metal oxide system in accordance with the invention, and having an atomic ratio of Mg to Cr of between 2 : 1 and 3 : 1, was prepared using the following procedure : An aqueous solution of 1, 2 mole of an alkali hydroxide and 0, 06 mole of alkali carbonate was combined with an aqueous solution containing 0, 3 mole of Mg (NO3) 2. H20, 0, 1 mole Cr (NO3) 3. H20 and 0, 5M NaOH/Na2CO3 mixture dissolved in water, at ambient temperature. The resultant alkaline mixture had a pH of 10. The

mixture was thoroughly stirred and thereafter aged, under quiescent conditions, for 24 hours at room temperature. A precipitate formed. The precipitate was filtered out, washed and dried. The precipitate, ie the MgCr material or mixed metal oxide system material, had the formula Mg6Cr2 (OH) 16CO3. 4H2O, ie a mixed metal oxide system in accordance with Formula (1) and in which r, s, w, x, y and z = 0 while t = 6, 0, so that the sum of r, s, t, w, x, y, and z = 6, 0 ; b, c, d, e, and f = 0 while a = 2, 0, so that the sum of a, b, c, d, e and f = 2, 0 ; p = 16 ; X = CO3 ; q = 1, 0 ; and Y = 4 or 5. The material was calcined at 550°C. The resultant solid calcined material, ie the catalyst, was analyzed by x-ray diffraction, and the surface area determined to be 156m2/g. It had a hydrotalcite structure. The catalyst was tested for the dehydrogenation of hexane in a fixed bed microreactor, under the dehydrogenation or reaction conditions specified in Table 1. Prior to testing, the catalyst was activated through reduction thereof by exposing it to synthesis gas comprising mainly carbon monoxide and hydrogen.

TABLE 1 Dehydrogenation temperature 540°C Dehydrogenation pressure 1 bar (a) Weight Hourly Space Velocity (WHSV) lg/gcat. h-1 The results obtained are given in Table 2.

TABLE 2 Dehydrogenation of Hexane Conv of hexane/% Selectivity to benzene/% 49 90

EXAMPLES 2 TO 7 A number of catalysts (Examples 2 to 7) in accordance with the invention, were prepared and activated using the identical procedure as in Example 1, apart from using different soluble metal salts and/or different proportions thereof, as given in Table 3. All these catalysts had hydrotalcite structures.

TABLE 3 Example Mole of Soluble Metal Salt 2 0, 6 mol/dm3MgN03. 6H20/0, 2 mol/dm3Cr (NO3) 3. 9H20/1, 6 mo l/dm3KOH/0, 1 mol/dm3K2CO 3 0, 6 mol/dm3MgNO3.6H2O/0, 2 mol/dm3Cr (N03) 3. 9H20/1, 6 mo I/dm3KOHIO, 1 mol/dm3K2C03 4 0, 6 mol/dm3MgNO3.6H2O/0, 2 mol/dm3Cr(N)3)3.9HwO/1, 6 mo I/dm3KOH/0, 1 mol/dm3K2C03 5 0, 6 mol/dm3MgN03. 6H20/0, 2 mol/dm3Cr (NO3) 3. 9H20/1, 6 mo l/dm3KOH/0, 1 mol/dm3K2CO 6 0, 3 mol/dm3MgNO3.6H2O/0,05 mol/dm3Cr(NO3)3.9H2O/0,05 mol/dm Fe(NO3)3.9H21, 6/8 mol/dm KOH/0, 1 mol/dm K2CO 7 0, 6 mol/dm3MgN03. 6H20/0, 2 mol/dm3Cr (NO3)3.9H2O/1, 6 mo I/dm3KOH/0, 1 mol/dm3K2CO The catalysts of Examples 2 to 7 were tested with different feedstocks using the reaction conditions given in Example 1. The results are given in Table 4.

TABLE 4

Metal Example components Feedstock Conversion/% Selectivity/% 2 Mg6Cr2 (OH) 6CO3. 4H20 Hexane 54 Benzene-85 3 Mg6Cr2 (OH)16CO3.4H2O Octane 54 Ethylbenzene-30 Xylenes-47 4 M96Cr2 (OH) 16CO3 4H2O Dodecane 17 C6-benzenes-30 Dodecene-19 5 Mg6Cr2(OH)16CO3.4H2O Hexadecane 23 21 0-benzenes-5 Hexadecene-21 6 Mg6CrFe (OH) 1 6 CO3. 4H2O Hexane 24 Benzene-65 7 Mg, Cr Hexane + 51 Benzene 70 30ppm DMDS* * DMDS dimethyl-disulphide EXAMPLES 8 TO 18 AND 26 A catalyst (Example 18) in accordance with the invention was prepared, using the following components and procedure : A solution of 76, 92g Mg (NO3) 2. 6H2O (0, 3 mole) and 40, 02g Cr (NO3) 3. 9H2O (0, 1 mole) in 500mE distilled water was added to a solution of 67g NaOH (1, 2 mole) and 7, 0g Na2CO3 (0, 07 mole) in 500mE distilled water. This addition was carried out in a 2# flask equipped with a mechanical stirrer and a dropping funnel.

The addition took about 2 hours and was carried out under vigorous stirring at room temperature. Following the addition, which resulted in the formation of a heavy slurry, the mixture or slurry was aged by heating the flask contents at 70°C for about 18 hours. This latter step induces the precipitate to crystallize. Following the heating period, the slurry was filtered and washed until the potassium content of the resulting solid was below 0, 05%. The solid was then dried (80°C/18 hours) followed by a calcination step (80°C-250°C at 1°C/min, leave at 250°C for 2 hours, from 250°C-550°C at 1°C/min, leave at 550°C for 5 hours).

The catalyst had the formula Mg6Cr2 (OH) 16CO3. 4H2O so that it was in accordance with Formula (1).

A number of catalysts (Examples 8 to 17 and 26) in accordance with the invention were prepared using the identical procedure as for the catalyst of Example 18, apart from using different soluble metal salts and different proportions thereof, as given in Table 5.

All these catalysts had hydrotalcite structures.

TABLE 5

Example Concentration of soluble Metal Surface Formula of the mixed metal oxide Salt Area m2/g prior to calcining 8 0, 3 mol/dm3 Mg(NO3)2.6H2O 115, 6 Mg3Zn3cr2 (OH) CO2. 4H 0,3 mol/dm3 Zn(NO3)2.6H2O 2, 2 mol/dm3 Cr (NO3)3.9H2O 2, 4 mol/dm3 NaOH 0, 12 mol/dm3 Na2CO 0,6 mol/dm3 MG(N)3)2.6H2O 11,8 Mg6Cr1,8Au0,2(OH)16CO3.4H2O 0,16 mol/dm3 Cr(NO3)3.9H2O 0, 04 mol/dm3 AuCl3 2, 4 mol/dm NaOH 0, 12 mol/dm Na CO 10 0, 6 mol/dm3 Mg(NO3)2.6H2O 180 Mg6Co2 (OH) CO. 4H20 2, 2 mol/dm3 Co(NO3)2.6H2O (Reference Mat Res Soc Symp Proc Vol 549, 1999) 2, 4 mol/dm3 NaOH 0,12 mol/dm3 Na2CO3 11 0,3 mol/dm3 Mg(NO3)2.6H2O 95,5 Mg6CrFe(OH)16CO3.4H2O 0,05 mol/dm3 Cr(NO3)3.9H2O 0, 05 mol/dm3 Fe(NO3)3.9H2O 1, 6 mol/dm KOH 0, 1 mol/dm3 K CO 12 0, 6 mol/dm3 Mg(NO3)2.6H2O 86, 2 Mg6Fe3 (OH) 6CO3.4H2O 0, 2 mol/dm3 Fe(NO3)3.9H2O 2, 4 mol/dm3 NaOH 0, 12 mol/dm Na CO 13 0, mol/dm3 Mg(NO3)2.6H2O 120, 1 Mg6AI2 (OH) 16CO3 4H20 0, 1 mol/dm3 AI (NO3)3.9H2O 2, 4 mol/dm33NaOH 0, 12 mol/dm Na CO 14 0, 6 mol/dm3 Mg(NO3)2.6H2O 112, 3 Mg6CrAl (OH) 1 6CO3. 4H 2O 0, 1 mol/dm3 Cr(NO3)3.9H2O 0, 1 mol/dm3 Al(NO3)3.9H2O 2, 4 mol/dm3 KOH 0, 12 mol/dm K CO 15 0, 6 mol/dm3 Zn(NO3)2.6H2O 80, 6 Zn6Fe2 (OH) 6CO3.4H2O 0, 6 mol/dm3 Fe (N03) 3. 9H20 2, 4 mol/dm3 NaOH 0,12 mol/dm3 Na2CO3 16 0,6 mol/dm3 Mg(NO3)2.6H2O 17,4 Mg6V2(OH)16CO3.4H2O 0, 2 mol/dm3 VCl3 2, 4 mol/dm3 NaOH 0, 12 mol/dm NaCOo 17 0, 6 mol/dm3 Mn(NO3)2.6H2O 100, 2 Mn6Cr2(OH)16CO3.4H2O 0, 2 mol/dm3 Cr(NO3)3.9H2O 2, 4 mol/dm3 KOH 0, 12 mol/dm K CO 18 0, 6 mol/dm3 Mg(NO3)2.6H2O 153,18 Mg6Cr2 (OH)16CO3.4H2O 0, 2 mol/dm3 Cr(NO3)3.9H2O 2, 4 mol/dm3 KOH 0, 12 mol/dm K CO 26 0, 6 mol/dm3 Mg (N 6H 0 141, 6 Mg6(Cr2(OH)16CO3.4H2O Recalcined 0,2 mol/dm3 Cr(NO3)3.9H2O catalyst 2, 4 mol/dm3 KOH 0, 12 mol/dm K CO

The x-ray powered diffraction pattern of the uncalcined material (Mg6Cr2 (OH) 16C03. 4H2O) shows distinctive lines associated with the natural occurring hydrotalcite stichtite (Mg6Cr2 (OH) 16CO3. 4H2O).

It can therefore be positively identified as a MgCr-hydrotalcite structure : d/Al/lo 7, 76 100 3, 90 29 2, 607 9 2, 6 1 2, 323 7 1, 976 6 1, 764 1 1, 667 1 1, 545 3 1, 516 3 1, 496 1 1, 437 1 1, 330 1 1,303 1 1,283 1 X-ray powder diffraction of the calcined material (calcined at 550°C) (forming the mixed oxide MgCr204) in the process shows distinctive lines of Periclase (MgO)

d/Al/lo 2, 4316 4 2, 1056 100 1, 4890 39 1, 2698 5 1, 2157 10 1, 0528 8 0, 9962 2 0, 9417 19 0, 8597 14 0, 8105 4 The catalysts of Examples 8 to 18 and 26 were then tested with different feedstocks as given in Table 7, as follows : A fixed bed micro reactor in a down-flow mode was used for all reactions or tests. The prepared catalyst samples (150-300ym) were loaded into the reactor and the dead volume was filled with either 3mm glass balls or carborundum (for >550°C reaction temperatures). The catalyst was heated to 550°C under a flow of N2 and left at 550°C overnight.

Thereafter, a synthesis gas ('syngas') reduction procedure was used to activate the catalyst and to eliminate undesirable metal oxidation states, such as Cr6+ (with Cr3+ being preferred and being achieved with the syngas reduction procedure), from the catalyst surface. An oxidation state such as Cr6+ is undesired in view of its carcinogenic properties and since it is not desired for aromatization. This procedure was applied during the

start-up of the reaction or test run. After the catalyst was loaded, it was taken up to reaction temperature (typically 550°C) in a syngas stream (10f. h-1) at a rate of 1°C/min. All reactions were performed at atmospheric pressure. It was left at the reaction temperature for 5 to 12 hours in the flowing syngas stream, whereafter the syngas was removed and the reaction started. The syngas had a composition as given in Table 6.

Syngas is preferred as the reduction agent in view of, for example, its ready availability and low cost.

TABLE 6 Syngas Composition (mole %) l H2 69, CO 30, 36 CH4 0, 01 N2 0, 37 C2H6 0, 03 Argon 0, 03 CO2 0, 02 To improve the lifetime of the catalyst, additional syngas was added during the run to maintain a reducing atmosphere in the reactor. A constant flow of syngas was thus added for the period of the run. Typical flow was 7f. h-1.

The reaction or test run conditions, as well as the results obtained, are given in Table 7. All catalysts tested were freshly prepared except for Example 26 where a regenerated catalyst was used.

TABLE 7 Example No 8 9 10 11 12 13 Composition Mg3Zn3Cr2* Mg6Cr1,8Au0,2* Mg6Co2* Mg6Co2* Mg6CrFe* Mg6Fe2* Mg6Al2* time on Stream-h 1 1 1 2 2 2 Feed Hexane Hexane Hexane Hexane Hexane Hexane WHSV 1 1 1 1 1 1 Temp-°C 550 550 550 550 550 550 Conversion-% 27,5 32 15,0 41,7 27,3 6,75 Selectivity 66,2 41,0 3,1 57,2 20,2 7,4 Aromatics-wt% Example No 14 15 16 17 18 26 Composition Mg6CrAl* Zn6Fe2* Mg6V2* Mn6Cr2* Mn6Cr2* Mg6Cr2* Mg6Cr2* (Regenerated) time on Stream-h 1 1 2 1 1 1 Feed Octane Octane Octane Octane Octane Octane WHSV 1 1 1 1 1 1 Temp-°C 550 550 550 550 550 550 Conversion-%47,7 40,42 23,6 10 56,7 54,4 Selectivity 49,5 10,2 44,7 21,9 87,6 Aromatics-wt% *=(OH)16CO3.4H2O. This is structure of the prepared catalyst before calcination.

After calcination, the structure of the catalyst is no longer a hydrotalcite, but a mixed oxide with the general formula of M2+M3+O4.

EXAMPLES 19 TO 24 A catalyst (Examples 19 to 24) in accordance with the invention, was prepared and activated using the identical components and procedures as described for Example 18. The catalyst thus had the formula Mg6Cr2 (OH) 16CO3. 4H2O so that it was also in accordance with Formula (1). It thus also had a hydrotalcite structure.

This catalyst was tested using different feedstocks as given in Table 8. In each case, a fresh or new batch of activated catalyst was used. The reaction or test procedures were as given in Example 1, and the reaction or test conditions were as given in Table 8. The results are also given in Table 8.

TABLE 8 Example No 19 20 21 22 23 24 Composition Mg6Cr2 Mg6Cr2 Mg6Cr2 Mg6Cr2 Mg6Cr2 Mg6Cr2 Time on stream-h 1 1 1 1 1 1 Feed Ethylbenzene Cyclohexane Hexanol FT-Naphtha CDU-Naphtha SB-Naphtha WHSV 1 1 1 1 1 1 Temp-°C 550 550 550 550 550 550 Conversion-% 40 60,4 81,7 54,8 48,2 20,4 Selectivity 94 68,3 Phenolic 57,84 28,6 25,5 Aromatics-wt% compounds 3,5 The F-T (Fischer-Tropsch derived) naphtha used in Example 22 had a composition as given in Table 9. This naphtha is sulphur free.

TABLE 9

Component wt.% C4/CX paraffins 0, 3 C6 linear paraffins 2, 7 C6 iso-paraffins 2, 4 C6 olefins 1, 5 Benzene 0, 3 C7 linear paraffins 37, 8 C7 iso-paraffins 42, 7 C7 olefins 5, 2 Dienes and cyclics 3, 3 Toluene 1, 1 C8 paraffins 2,7 Total 100 The CDU (Crude Distillation Unit derived) naphtha used in Example 23 had a composition as given in Table 10. This naphtha is obtained directly from crude oil distillation, and contains 150-400mg/kg sulphur and lmg/kg nitrogen.

TABLE 10

Component wt. % C4/C5 paraffins 0, 2 C6 linear paraffins 7, 7 C6 iso-paraffins 4, 2 C6 olefins 0, 0 C-linear paraffins 13, 4 C, iso-paraffins 14, 6 C7 olefins 0, 0 C8 linear paraffins 11, 2 C8 iso-paraffins 10, 7 C8 olefins 2, 9 Benzene 0, 8 Ethylbenzene 2, 0 Xylenes 8, 8 Styrene 0, 1 Toluene 5, 2 Dienes and cyclics 18, 2 Total 100 The SB (Stripper Bottoms derived) naphtha used in Example 24 had a composition as given in Table 11. This naphtha is obtained as the stripper bottoms of a naphtha unifiner, and comprises an approximately 80 : 20 (vol basis) CDU/DHC naphtha mixture that has been hydroprocessed. It is sulphur and nitrogen free.

TABLE 11 Component wt. % C4/CX paraffins 1, 1 C6 linear paraffins 6, 1 C6 iso-paraffins 4, 1 C6 olefins 0, 0 C7 linear paraffins 12, 5 C7 iso-paraffins 14, 9 C7 olefins 0, 0 C8 linear paraffins 10, 1 C8 iso-paraffins 11, 4 C8 olefins 3, 8 Benzene 0, 8 Ethylbenzene 1, 7 Xylenes 7, 5 Styrene 0, 1 Toluene 5, 3 Dienes and cyclic20, 6 Total 100 EXAMPLE 25 The catalyst of Example 18 was tested for feed sulphur tolerance by testing it with different feedstocks having different sulphur concentrations. The catalyst was found to be extremely sulphur tolerant, as shown in Figure 1. From Figure 1, it can be seen that the catalyst of Example 18 can handle feedstock sulphur concentrations of up to 30ppm (and even higher) without affecting its activity or selectivity. In contrast, known dehydration catalyst show decreased conversions and/or selectivities at feedstock sulphur concentrations as low as lOppb.

The Applicant is aware that alkanes can be dehydrogenated to aromatics by means of platforming. This process is widely practiced in petroleum refining, originally for the purpose of increasing the octane rating of gasoline and for producing aromatics such as benzene, toluene, ethylbenzene, etc by using promoted catalyst systems. The aromatization of C6+ alkanes is highly endothermic, and high reaction temperatures are required

to achieve practical conversion levels. Hitherto, catalysts comprising highly dispersed platinum or palladium particles in large pore zeolites have been used for such reforming.

The Applicant is also aware that light alkanes (C2-C4) can also undergo aromatization in the presence of an acid catalyst to form aromatics. Such aromatization processes are distinguished from reforming by the fact that the catalysts used are able to convert alkanes with fewer than six carbon atoms, to aromatic compounds, ie compounds containing six carbon atoms. The catalysts used in these processes also comprise platinum or palladium particles on zeolytic supports.

These known processes suffer from the disadvantage that catalysts containing platinum group metals, such as platinum and palladium based catalysts, are very expensive. Platinum and palladium are also very sensitive to sulphur poisoning. In contrast, the catalysts of the present invention are generally cheaper and not sensitive to sulphur, as is evident from the Examples and Figure 1.

The Applicant has thus now found that alkanes and other hydrocarbon feedstocks can be dehydrogenated to aromatics, depending on the chain lengths of alkanes, by using non-platinum and non-palladium promoted catalysts. It is thus a feature of the present invention that it is not necessary to use supported platinum or palladium catalysts to dehydrogenate alkanes and other hydrocarbon feedstocks to aromatics. In particular, the Inventors surprisingly found, after substantial research, that dehydrogenation reactions to aromatics can be obtained, at conversion levels of alkanes to aromatics of at least 48%, by using a catalyst comprising only a mixture of less expensive metal oxides. The metal oxide catalysts of the present invention

can thus be derived from oxides of molybdenum, magnesium, chromium, iron, gallium, aluminium, cobalt, manganese, copper, zinc, gold and mixtures thereof. Catalysts of the present invention have been found to have activities as high as palladium and platinum promoted catalyst systems hitherto used. It was also surprisingly found that with the catalysts of the present invention, long catalyst lifetimes of in excess of 12 hours can be obtained, even though the catalysts do not contain platinum or palladium, before regeneration of the catalyst is required.

The Applicant is also aware that, with the known processes employing palladium and platinum based catalysts, and when the feedstock comprises a long chain hydrocarbon, the hydrocarbon chain is cut during the dehydrogenation or aromatization process.

In the process of the present invention, it was, however, surprisingly found that when long chain hydrocarbons are dehydrogenated, aromatic hydrocarbons with side chains are typically formed with little or no cutting of the hydrocarbon chain. In other words, better selectivity towards preferred aromatic hydrocarbons, such as xylenes (rather than benzene), is obtained.

The catalysts of the present invention are also characterized thereby that they do not contain any zeolite.

In the present invention, the Inventors have thus surprisingly found that a mixed metal oxide catalyst can be used to form aromatics from feedstocks such as alkanes, typically C2-C4o linear and/or branched alkanes, under typical conditions used in dehydrogenation processes.