Isomerization of paraffins

Details Isomerization of paraffins Isomerization of paraffins

1999-11-01

2001-10-30

Yildirim, Bekir L. (Department: 1764)

Chemistry of hydrocarbon compounds

Saturated compound synthesis

By isomerization

C585S750000, C585S751000

Reexamination Certificate

active

06310265

ABSTRACT:

FIELD OF THE INVENTION
This invention relates to the isomerization of paraffins and particularly the hydroisomerization of n-paraffins.
BACKGROUND OF THE INVENTION
The isomerization of paraffins is an important reaction in both fuels and lubes refining in providing a mechanism for removing waxy components in the feed while minimizing cracking of these components to materials boiling outside the fuel and lube range. In fuels refining, paraffin isomerization is also used to produce high octane, branched paraffins to compensate for the octane deficit resulting from the removal or reduction of lead and aromatic components from the gasoline pool. Certain zeolites have been found to be good isomerization catalysts, particularly when impregnated with noble metals. For example, U.S. Pat. Nos. 4,419,220 and 4,919,788 disclose the use of zeolite beta as a paraffin isomerization catalyst. It has now been found that the recently discovered zeolite designated MCM-68 has activity for the isomerization of paraffins, particularly when steamed to a low acid activity (alpha) and impregnated with a hydrogenation metal, such as platinum.
SUMMARY OF THE INVENTION
According to the invention, there is provided a process for isomerizing paraffins comprising the step of contacting a feed containing paraffins with a catalyst comprising a porous crystalline material, MCM-68, which contains at least one channel system, in which each channel is defined by a 12-membered ring of tetrahedrally coordinated atoms, and at least two further, independent channel systems, in each of which each channel is defined by a 10-membered ring of tetrahedrally coordinated atoms, wherein the number of unique lomembered ring channels is twice the number of 12-membered ring channels.
Preferably, the contacting step is conducted in the presence of hydrogen and the catalyst contains a hydrogenation metal, most preferably a noble metal.
DETAILED DESCRIPTION OF THE INVENTION
The paraffin isomerization process of the invention employs the synthetic porous crystalline material MCM68, which is a single crystalline phase which has a unique 3-dimensional channel system comprising at least one channel system, in which each channel is defined by a 12-membered ring of tetrahedrally coordinated atoms, and at least two further independent channel systems, in which each channel is defined by a 10-membered ring of tetrahedrally coordinated atoms, wherein the number of unique 10-membered ring channels is twice the number of 12-membered ring channels. The normal crystalline form of MCM-68 contains one 12-membered ring channel system and two 10-membered ring channel systems, in which the channels of each system extend perpendicular to the channels of the other systems and in which the 12-ring channels are generally straight and the 10-ring channels are tortuous (sinusoidal).
MCM-68 can be prepared in essentially pure form with little or no detectable impurity crystal phases and, in its calcined form, has an X-ray diffraction pattern which is distinguished from the patterns of other known as-synthesized or thermally treated crystalline materials by the lines listed in Table 1 below. In its as-synthesized form, the crystalline MCM-68 material of the invention has an X-ray diffraction pattern which is distinguished from the patterns of other known as-synthesized or thermally treated crystalline materials by the lines listed in Table 2 below.
TABLE 1
d(Å)
Relative Intensity [100 × I/I(o)]
13.60 +/− 0.39 
S
13.00 +/− 0.37 
VS
10.92 +/− 0.31 
M
10.10 +/− 0.29 
M
9.18 +/− 0.26
VS
8.21 +/− 0.23
W
4.58 +/− 0.13
W
4.54 +/− 0.13
W
4.45 +/− 0.13
VW-W
4.32 +/− 0.12
VW
4.22 +/− 0.12
VW
4.10 +/− 0.12
VS
4.05 +/− 0.11
M
3.94 +/− 0.11
M
3.85 +/− 0.11
M
3.80 +/− 0.11
VW
3.40 +/− 0.10
W
3.24 +/− 0.09
W
2.90 +/− 0.08
VW
TABLE 2
d(Å)
Relative Intensity [100 × I/I(o)]
13.56 +/− 0.39 
VW
12.93 +/− 0.37 
M-S
10.92 +/− 0.31 
W
10.16 +/− 0.29 
VW-W
9.15 +/− 0.26
VW-W
8.19 +/− 0.23
VW
4.58 +/− 0.13
W
4.54 +/− 0.13
W
4.44 +/− 0.12
W
4.32 +/− 0.12
VW
4.23 +/− 0.12
VW
4.10 +/− 0.12
VS
4.06 +/− 0.12
M
3.98 +/− 0.11
W
3.88 +/− 0.11
M
3.80 +/− 0.11
VW
3.40 +/− 0.10
VW
3.24 +/− 0.09
W
2.90 +/− 0.08
VW
These X-ray diffraction data were collected with a Scintag diffraction system, equipped with a germanium solid state detector, using copper K-alpha radiation. The diffraction data were recorded by step-scanning at 0.02 degrees of two-theta, where theta is the Bragg angle, and a counting time of 10 seconds for each step. The interplanar spacings, d's, were calculated in Angstrom units, and the relative intensities of the lines, I/I
o
is one-hundredth of the intensity of the strongest line, above background, were derived with the use of a profile fitting routine (or second derivative algorithm). The intensities are uncorrected for Lorentz and polarization effects. The relative intensities are given in terms of the symbols vs=very strong (80-100), s=strong (60-80), m=medium (40-60), w=weak (20-40), and vw=very weak (0-20). It should be understood that diffraction data listed for this sample as single lines may consist of multiple overlapping lines which under certain conditions, such as differences in crystallographic changes, may appear as resolved or partially resolved lines. Typically, crystallographic changes can include minor changes in unit cell parameters and/or a change in crystal symmetry, without a change in the structure. These minor effects, including changes in relative intensities, can also occur as a result of differences in cation content, framework composition, nature and degree of pore filling, crystal size and shape, preferred orientation and thermal and/or hydrothermal history.
MCM-68 has a composition involving the molar relationship:
X
2
O
3
:(n)YO
2
,
wherein X is a trivalent element, such as aluminum, boron, iron, indium, and/or gallium, preferably aluminum; Y is a tetravalent element such as silicon, tin, titanium and/or germanium, preferably silicon; and n is at least about 5, such as 5 to 100,000, and usually from about 8 to about 50. In the as-synthesized form, the material has a formula, on an anhydrous basis and in terms of moles of oxides per n moles of YO
2
, as follows:
(0.1-2)M
2
O:(0.2-2)Q:X
2
O
3
:(n)YO
2
wherein M is an alkali or alkaline earth metal, and Q is an organic moiety. The M and Q components are associated with the material as a result of their presence during crystallization, and are easily removed by post-crystallization methods hereinafter more particularly described.
MCM-68 can be prepared from a reaction mixture containing sources of alkali or alkaline earth metal (M), e.g., sodium and/or potassium, cation, an oxide of trivalent element X, e.g., aluminum and/or boron, an oxide of tetravalent element Y, e.g., silicon, directing agent (Q), and water, said reaction mixture having a composition, in terms of mole ratios of oxides, within the following ranges:
Reactants
Useful
Preferred
YO
2
/X
2
O
3
at least 5
 8-50
H
2
O/YO
2
  10-1000
 15-100
OH
−
/YO
2
0.05-2
0.1-0.5
M/YO
2
0.05-2
0.1-0.5
Q/YO
2
0.01-1
0.05-0.2 
The organic directing agent Q used herein is selected from the novel dications N,N,N′,N′-tetraalkylbicyclo[2.2.2]oct-7-ene-2,3:5,6-dipyrrolidinium dication and N,N,N′,N′-tetraalkylbicyclo[2.2.2]octane-2,3:5,6-dipyrrolidinium dication which can be represented by the following formulae:
where R
1
, R
2
may be the same or different substituents selected from alkyl groups having 1 to 6 carbon atoms, phenyl and benzyl gro

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