ISOMERIZATION CATALYST

Abstract

Paraffin isomerization catalyst comprising of from 0.01 to 5 wt. % of a Group VIII noble metal on a carrier containing alumina and zeolite beta having a silica to alumina molar ratio (SAR) of from 5 to 15 and process employing such catalyst for isomerization of a hydrocarbon feed containing paraffins having of from 4 to 8 carbon atoms.

Claims

1. A paraffin isomerization catalyst comprising of from 0.01 to 5 wt. % of a Group VIII noble metal on a carrier containing alumina and zeolite beta having a silica to alumina molar ratio (SAR) of from 5 to 15.

2. The paraffin isomerization catalyst according to claim 1, wherein the Group VIII noble metal is platinum which is present in an amount of from 0.1 to 3 wt. %.

3. The paraffin isomerization catalyst according to claim 1, wherein the carrier comprises of from 60 to 95 wt. % of the zeolite beta.

4. The paraffin isomerization catalyst according to claim 1, wherein the volume average crystal size of the zeolite beta as determined by scanning electron microscopy is of from 50 to 500 nanometers.

5. The paraffin isomerization catalyst according to claim 1, wherein the zeolite beta does not contain organic structure directing agent.

6. The paraffin isomerization catalyst according to claim 1, wherein the zeolite beta is prepared by a process which comprises (a) mixing and stirring an alkali oxide source, an aluminum oxide source, a silicon dioxide source and water to synthesize an initial aluminosilicate gel having the following mole ratio of raw materials: SiO.sub.2/Al.sub.2O.sub.3=15-45, Na.sub.2O/SiO.sub.2=0.20-0.50, H.sub.2O/SiO.sub.2=4-50, (b) adding zeolite crystal seed and allowing the mixture to crystallize at elevated temperature to obtain zeolite beta crystals having a silica to alumina molar ratio (SAR) of from 5 to 15.

7. The paraffin isomerization catalyst according to claim 6 wherein the process comprises allowing the mixture to crystallize in step (b) at a temperature of from 100 to 180 C. during from 12 to 24 hours.

8. The paraffin isomerization catalyst according to claim 1, wherein the zeolite beta has a SAR of from 5 to 11.

9. A process for preparing an isomerization catalyst according to claim 1, which process comprises (a) mixing alumina and zeolite beta having a SAR of from 5 to 15, extruding the mixture obtained in step (a) and optionally drying and calcining the extrudates obtained and (b) impregnating the extrudates obtained in step (a) with a platinum containing solution followed by drying and optionally calcining the impregnated extrudates.

10. The process according to claim 9, in which the impregnating solution of process step (c) is an aqueous solution comprising hexachloroplatinic acid.

11. The process for isomerizing a hydrocarbon feed containing paraffins having of from 4 to 8 carbon atoms by contacting the feed with a catalyst according to claim 1 at a temperature of from 150 to 300 C. and a pressure of from 0.1 to 30 bara.

Description

EXAMPLE 1SYNTHESIS OF BETA ZEOLITE CONTAINING CATALYST

[0031] Water, NaOH (50%) and sodium aluminate (23.5% Al.sub.2O.sub.3, 19.6% Na.sub.2O) were mixed together. Silica gel (available from PQ Corporation) was added to the solution and mixed vigorously for 1 hour. Finally, commercially available zeolite beta (available from Zeolyst International) in the amount of 10 wt. % with respect to the silica content of the slurry was added to the mixture and stirred for 24 hours. The gel had the following molar composition:

[0032] 20.0 SiO.sub.2:1.0 Al.sub.2O.sub.3:6.0 Na.sub.2O:400 H.sub.2O

[0033] The gel was loaded into a 2-liter Parr autoclave and heated to 125 C. and maintained at that temperature for 48 hours while stirring at 175 rpm. After cooling, the product was recovered by filtration and washing. To remove residual sodium, the solid was slurried in a 3.6 M NH.sub.4NO.sub.3 solution and stirred at 90 C. for 2 hours. This NH.sub.4NO.sub.3 exchange process was repeated twice. After filtering, washing, and drying, the final product had silica-to-alumina ratio (SAR) of 9.8. The BET surface area of the product was 668 m.sup.2/g and micropore volume was 0.23 cc/g.

[0034] The zeolite beta obtained was mixed with alumina binder (Sasol Pural SB1) in a weight ratio of 80:20 and 1.5 wt. % of nitric acid and 0.3 wt. % Superfloc N. The mixture had a loss on ignition of 53%. This mixture was extruded to obtain 1.4 mm diameter extrudates, dried for 2 hours at 140 C. and calcined for 2 hours at 500 C. The calcined extrudates were impregnated by pore volume impregnation with hexachloroplatinic acid solution and subsequently dried at 140 C. and calcined at 450 C. The final catalyst contained 0.3 wt. % of platinum, calculated as metal and had a compacted bulk density of 0.3 kg/l.

EXAMPLE 2ISOMERIZATION PROCESS

[0035] This example illustrates the use of a catalyst prepared as described in Example 1 (Catalyst 1) in the isomerization of a mixture of n-pentane, n-heptane and cyclohexane.

[0036] For comparison, we also tested a catalyst containing 0.3 wt. % of platinum, calculated as metal, on extrudates comprising 20 wt. % alumina binder and 80 wt. % zeolite beta having a SAR of 25 and having a compacted bulk density of 0.48 kg/1 (Catalyst A).

[0037] We further tested a comparative catalyst containing 0.3 wt. % of platinum, calculated as metal, on extrudates comprising 20 wt. % alumina binder and 80 wt. % zeolite beta having a SAR of 18 and a surface area of 675 m.sup.2/g (Catalyst B).

[0038] Each of the catalysts were dried at 200 C. and reduced with hydrogen at 10 bara and 300 C. and tested on a feedstock of 60 wt % n-O.sub.5, 35 wt % n-C.sub.6 and 5 wt % cyclo-C.sub.6.

[0039] The testing was carried out at liquid hourly space velocity of 1.90 cc feed/cc catalyst/hour, while the flow of the hydrogen gas stream was maintained to provide a ratio of hydrogen to feed of 1.2:1 (volume hydrogen on volume feed). The isomerization product was analyzed by means of a gas chromatograph.

[0040] The octanetonneyield is the calculated product yield times the calculated octane number. The octanetonneyield for the above catalysts at various temperatures are shown in Table 1 below.

TABLE-US-00001 TABLE 1 Octane per tonne yield Catalyst A Catalyst B Catalyst 1 235 C. 6500 6750 7000 250 C. 7400 7500 7600