US3925503A - Isomerization of normal paraffins with hydrogen mordenite containing platinum and palladium - Google Patents

Abstract

An improved hydroisomerization catalyst which comprises a mixture of platinum and palladium in the ratio range of 2 to 4 on an acid leached mordenite base. This combination provides a highly active catalyst with improved isopentane selectivity and with exceptional stability as is evidenced by essentially no decay in catalytic activity with time.

Description

United States Patent Parthasarathy Dec. 9, 1975 [5 ISOMERIZATION OF NORMAL PARAFFINS 3,542,671 11/1970 P0111115 4. 260/683.65 WITH HYDROGEN MORDENITE 3,632,835 l/l972 Mitsche et al. .v 260/683.68 3.691155 9/1972 Takase et al 260/683.68

CONTAINING PLATINUM AND 3.836597 9/1974 Sie 260/68365 PALLADIUM [75] Inventor: R. Parthasarathy, Silver Spring, Md.

[73] Assignee: W. R. Grace & Co., New York,

[22] Filed: Feb. 6, 1975 [21] Appl. No.: 547,666

[52] US. Cl. 260/683.65 [5]] Int. Cl. C07C 5/30 [58] Field of Search 1. 260/683.65, 683.68

[56] References Cited UNYTED STATES PATENTS 3,507,93l 4/1970 Morris et al. H 260/683.65

Primary Examiner-Delbert E. Gantz Assistant Examiner-G. J Crasanakis Attorney, Agent, or Firm.l0seph P. Nigon [57] ABSTRACT An improved hydroisomerization catalyst which comprises a mixture of platinum and palladium in the ratio range of 2 to 4 on an acid leached mordenite base. This combination provides a highly active catalyst with improved isopentane selectivity and with exceptional stability as is evidenced by essentially no decay in catalytic activity with time.

3 Claims, N0 Drawings ISOMERIZATION OF NORMAL PARAFFINS WITH HYDROGEN MORDENITE CONTAINING PLATINUM AND PALLADIUM BACKGROUND OF THE INVENTION The isomerization of low molecular weight normal hydrocarbons to isomers of these hydrocarbons is well known. This process is of considerable importance to the petroleum industry because of the substantially higher octane numbers of the isoparafi'ms. Not only are these isoparaffins valuable as low boiling blending components in gasoline, but they have become increasingly important as tetraethyl lead is being removed from the gasoline stocks, for use with automobiles having catalytic converters to remove the noxious components of the exhaust gases. High temperature processes employing supported metal catalyst have enjoyed increasing favor. Much of their work for supported systems involves catalysts comprising crystalline aluminosilicates, especially mordenite as disclosed in US. Pat. Nos. 3,140,252, 3,190,939, 3,475,545 and 3,442,714.

These patents teach the use of mordenite as a high activity support in combination with noble metals such as platinum or palladium for isomerization of light bydrocarbons. Although platinum is an active hydrogenation promoter for this reaction, it also enhances other side reactions such as hydrocracking, thereby increasing the deactivation rate of the catalyst. Palladium, on the other hand, is somewhat less active and is more susceptible to poisons, such as sulfur, that are found in some of the light paraffin feed stocks.

BRIEF DESCRIPTION OF THE INVENTION We have found that catalysts comprising a combination of platinum and palladium in a 2 to 4 ratio range distended on an acid mordenite support is surprisingly more active than the platinum or palladium alone, as is evidenced by lower temperature for the same conversion. The palladium addition supresses hydrocracking side reactions that are normally observed with platinum alone and therefore, produces a more selective catalyst with higher isopentane selectivity.

DETAILED DESCRIPTION OF THE INVENTION The feed to the process of this invention is substantially pure normal paraffin having 4 to 6 carbon atoms in the molecule or hydrocarbon fractions that are rich in these constituents. Suitable hydrocarbon fractions are the C to C or C C, straight run distillate fractions and C to C, fractions recovered from the catalytic cracking of gas oils.

An essential feature of the process of our invention is the fact that the reaction can be carried out at temperatures as low as 500. The prior art processes required that the temperature be maintained in the range of 550 to 625? with a temperature of 575 to 675F. being preferred.

The conventional space velocities for hydroisomerization reactions give satisfactory results with our catalysts. These reactions can be carried out over a wide range of space velocities, but in general, a space velocity in the range of 0.5 to 10 and preferably 1 to 5 weight hourly space velocity expressed as weight of feed per hour per unit weight of catalyst is preferred.

Although there is little or no net consumption of hydrogen in the isomerization reaction, the reaction is carried out in the presence of hydrogen. The hydrogen improves the catalyst life by preventing coating of the catalyst particles by polymers that are formed and deposit on the catalysts in the absence of hydrogen. The

hydrogen to oil mole ratio of about I to l to 25 to 1 and preferably about 5 to l to l5 to l are used in normal commercial operation of hydroisomerization of dehydroisomerization. However, it is not necessary to use pure hydrogen to produce the catalyst surfaces. The hydrogen rich gases from the catalystic reforming of naptha give suitable results.

The isomerization reactions normally carried out at pressures ranging from l5 to 1000 pounds per square inch guage with pressures of about 300 to 750,psig being preferred.

As pointed out previously, our catalyst is preferably on a hydrogen form mordenite base. This hydrogen form mordenite is readily available from the Norton Company and provides an excellent base for our catalyst system.

The catalysts can contain from 0.1 to 2 weight percent platinum and 0.1 to 2 weight percent palladium as long as the platinum to palladium weight ratios of 2 to 4 are maintained.

Our invention is further illustrated by the following specific but not limiting examples.

EXAMPLE 1 This example illustrates a typical method of preparing our catalysts.

A quantity of sodium form mordenite supplied by the Norton Company is placed in a suitable vessel and mixed with two normal hydrochloric acid solution at a rate ratio of 1 part zeolite to 5 to [0 parts 2 normal hydrochloric acid. The resulting composite is brought to a boil with stirring for about 1 to 2 hours. The powder is then filtered and washed with deionized water and the whole process is repeated for a second time. Following the second wash, the mordenite powder is mixed with 2 normal ammonium chloride, or ammonium nitrate solution in a proportion of l to 10 and boil for 1 hour with stirring.

A mixed ammoniacal palladium-platinum chloride or nitrate solution is prepared by the addition of excess ammonium hydroxide to a solution of platinum and palladium salts. The washed mordenite powder is slurried in deionized water and the two solutions are added simultaneously into a mixing vessel and brought to a boil and boiling continued for l to 2 hours. The catalyst is filtered washed, dried and fonned into pellets. The pellets are then calcined for two hours at 650F. followed by calcination 6 to 10 hours at l000F.

EXAMPLE 2 A series of catalysts were prepared that contained 0.6 weight percent platinum, 0.4 weight percent platinum and 0.2 weight percent palladium, 0.3 weight platinum and 0.1 weight percent palladium, 0.3 weight percent platinum 0.3 weight percent platinum, 0.5 weight percent palladium.

These catalysts were prepared by the process outlined in Example 1.

EXAMPLE 3 The catalysts prepared in Example 2 were evaluated in a hydroisomerization reactor using a penthane feed that was greater than 99.5% pure, supplied by Phillips Petroleum Corporation. The tests were carried out at a pressure of 450 psig, a hydrogen to normal pentane ratio of 3, a weight hourly space velocity of l and at temperature of 500F. The support was acid leached mordenite having a silica to alumina ratio of 18. The data collected in this series of runs is set out in the table 4 What is claimed is: l. A process for isomerizing normal paraffms having from 4 to 6 carbon atoms per molecule which comprises contacting said normal parafiins in the presence below. of hydrogen at a temperature of 500 to 600F. with hy- Table l Pt/Pd Wt.% MC Selec- %Hydro- Loss in Conv. ratio Conv. tivity cracking after 24 hrs. Catalyst per day 0.6% Pt/Acid-leached 60 97.4 0.9 -l.0 Mordenite 0.4% Pt 0.2% I'd/Acid 2 59 97.6 0.8 leached Mordenite 0.3% Pt 0.l% Pd/Acid 3 57.5 97.5 0.7 leached Mordenite 0.3% Pt 0.3% Pd/Acid l 55 97.8 0.5 leached Mordenitc 0.5% Pd/Acid-leached 55 97.5 0.7 Mordenite It is obvious from review of these data that although platinum alone on mordenite is an active catalyst, it also promotes hydrocracking as is evidenced by the loss in conversion of approximately 1% per day. Palladium alone minimizes the hydrocracking and there is no disemable deactivation. However, it produces a less active catalyst as is obvious from the conversion figures. It is obvious from the data that a combination of the two metals in the ratio range of 2 to 4 is the optimum catalyst with regard to activity and isopentane selectivity. In addition, there is no noticeable catalyst decay with time when the noble metals are present in this ratio.

drogen mordenite having incorporated therewith, a mixture of platinum and palladium in a concentration of 0.3 to 2.0 percent, wherein the ratio of platinum to palladium in said mixture is in the range of 2 to 4.

2. The process according to claim 1 wherein said isomerization is carried out at a pressure of 15 to 1000 psig and a weight hourly space velocity of 0.5 to 10.

3. The process according to claim 1 wherein the hydrogen to oil mole ratio is about 1 to l to 25 to l and a weight hourly space velocity of 0.5 to ID.

Claims (3)

1. A PROCESS FOR ISOMERIZING PARAFFINS HAVING FROM 4 TO 6 CARBBON ATOMS PER MOLECULE WHICH COMPRISES CONTACTING SAID NORMAL PARAFFINS IN THE PPRESENCE OF HYDROGEN AT A TEMPERATURE OF 500* TO 600*F, WITH HYDROGEN MORDENITE HAVING INCORPORATED THEREWITH, A MIXTURE OF PLATINUM AND PALLADIUM IN A CONCENTRATION OF 0.3 TO 2.0 PERCENT, WHEREIN THE RATIO OF PLATINUM TO PALLADIUM IN SAID MIXTURE IS IN THE RANGE OOF 2 TO 4.

2. The process according to claim 1 wherein said isomerization is carried out at a pressure of 15 to 1000 psig and a weight hourly space velocity of 0.5 to 10.

3. The process according to claim 1 wherein the hydrogen to oil mole ratio is about 1 to 1 to 25 to 1 and a weight hourly space velocity of 0.5 to 10.