Catalyst – solid sorbent – or support therefor: product or process – Catalyst or precursor therefor – Metal – metal oxide or metal hydroxide
Reexamination Certificate
2000-03-03
2003-03-18
Silverman, Stanley S. (Department: 1754)
Catalyst, solid sorbent, or support therefor: product or process
Catalyst or precursor therefor
Metal, metal oxide or metal hydroxide
C502S241000, C502S259000, C502S263000, C502S335000, C502S355000, C502S407000, C502S415000, C502S439000
Reexamination Certificate
active
06534441
ABSTRACT:
The present invention relates to a catalyst for the reductive amination of lower aliphatic alkane derivatives. The catalyst comprises rhenium, nickel and, optionally, boron, supported on an alumina-silica support, wherein the alumina-silica support contains from about 5 to about 65 weight percent silica and has a BET surface area of from about 30 to about 450 m
2
/g. The catalyst provided by the invention has increased activity as well as selectivity to a specified mix of polyamine products.
BACKGROUND OF THE INVENTION
The reductive amination of lower aliphatic alkane derivatives, i.e., diols such as ethylene glycol and alkanolamines such as monoethanolamine, is a commercially important family of processes. A variety of catalyst compositions for this purpose are found in the literature and are used commercially. Many are based on nickel/rhenium mixtures deposited on a support material. For example, U.S. Pat. No. 4,795,733 to DeThomas relates to nickel/rhenium catalyst compositions also containing a Group VIII metal having an atomic number greater than 43. The catalyst composition is supported on a material such as carbon, magnesium silicate, bentonite, zeolite, metal alloys, silica-alumina, and magnesium oxide-silicon oxide mixtures. Preferred as a support material is gamma-alumina.
PCT Application No. WO 96/38226 discloses catalyst compositions comprising rhenium, nickel, cobalt, boron and copper and/or ruthenium deposited on a support material. Disclosed support materials are silica, aluminum, and/or titanium, preferably silica or alumina, particularly alpha-alumina, silica, silica-alumina, kieselguhrs, diatomaceous earths, or silica-titania, most preferably silica. Surface areas of 10 to 500 m
2
/g, more preferably from 40 to 200, m
2
/g are disclosed.
U.S. Pat. No. 5,202,491 to Burgess et al. discloses a continuously generated alkyleneamines composition that may be produced using a variety of nickel-containing catalyst compositions. The patent also discloses that the catalysts may be supported using a number of support materials, including silica-alumina.
Finally, U.S. Pat. Nos. 4,111,840 and 4,123,462 to Best disclose catalyst compositions comprising nickel and rhenium impregnated on a support material selected from alpha-aluminas, silica, silica-alumina, kieselguhrs, diatomaceous earths, and silica-titania, wherein the mole ratio of nickel to rhenium ranges from about 2:1 to about 30:1 and the catalyst is activated by reduction in the presence of hydrogen at elevated temperature.
The Best patents teach that not all support materials are equivalent and that higher surface area supports lead to more active Ni/Re catalyst compositions. However, the data provided in these patents do not support this conclusion. In particular, the data provided in Example 4 of the Best patents show that neither support surface area nor metal loading provides a statistically significant effect on catalyst activity, while the data provided in Example 5 in both references show that increasing the surface area of the support reduces the activity of the catalyst.
It is not clear why a rate effect is seen with respect to Example 5 and no such effect is shown in Example 4, particularly since the catalyst compositions and the reaction conditions are so similar. These inconsistent teachings lead to the conclusion that, at best, increasing the surface area of the support reduces the activity of the catalyst only under some circumstances.
Table 1 of the '840 patent discloses several examples of commercially available, useful support materials, including the following containing both silica and alumina:
Support
Surface Area (m
2
/g)
Percent Silica
Girdler T869
~60
95.1
Girdler T1571
~150
93
Girdler T372
~40
0.2
Girdler T373
2-3
0.2
Girdler K306
~250
88
Girdler T2085
~113
97.4
Girdler K10
~268
81
Grace 980-13
~375
87
Grace 980-25
~375
75
Reductive amination produces a variety of products, some of which have greater economic value than others, depending on current market requirements. For example, the reductive amination of monoethanolamine (MEA) produces lower molecular weight linear polyamine products, such as ethylenediamine (EDA), aminoethylethanolamine (AEEA), and diethylenetriamine (DETA). EDA is a highly commercially valuable product at present, and market demand also exists for AEEA and DETA. Higher molecular weight linear polyamines, such as diamine and triamine, and/or cyclic polyamine products, such as piperazine (PIP), hydroxyethylpiperazine (HEP), aminoethylpyrazine (AEP) and heavy polyamine oligomers, are also formed. Although these products tend to be less valuable than the lower molecular weight polyamine products, there is often an economic incentive for their production. Accordingly, for maximum economic benefit the catalyst compositions used in commercial reductive amination processes must be selective to the desired mixture of polyamine products, in addition to being highly active.
The prior art has not appreciated how to control catalyst composition and preparation variables in a manner that provides a catalyst which has a specified activity and which is selective for a particular mix of products. For example, a statistical analysis of the data presented in Example 4 of the Best '840 patent leads to the conclusion that support surface area has no statistically significant effect on the EDAIPIP ratio. This is also the case with the data presented in Example 5 of the Best '462 patent. In fact, if any effect is shown in this data, it is that increasing the surface area of the support decreases the EDA/PIP ratio. Examples I and F of U.S. Pat. No. 5,600,000 suggest that under some circumstances and in the presence of certain promoters, metal loading can have an effect on catalyst activity; however, the effects of surface area and other important catalyst preparation variables were not considered.
It has now been discovered that nickel/rhenium catalyst compositions supported on alumina-silica containing from about 5 to about 65 weight percent silica and having a BET surface area of from about 30 to about 450 m
2
/g (as measured by the method of Brunauer, Emmitt and Teller) are especially advantageous for the production of polyamine products. By appropriately selecting the composition of these catalysts and controlling certain catalyst preparation variables, it is possible to provide catalysts which have a desired activity and which are capable of providing a specified mix of polyamine products.
Accordingly, the catalysts taught by the invention can be used to provide a mix of polyamine products characterized by very favorable ratios of lower molecular weight polyamines, such as EDA, AEEA and DETA, to less favorable higher molecular weight linear and cyclic products such as diamine, triamine, PIP, and HEP. However, should market demands change, the catalyst composition can be appropriately adjusted and the conditions for preparing the catalyst controlled in a manner such that the catalyst is relatively more selective for the higher molecular weight linear and cyclic polyamine products.
SUMMARY OF THE INVENTION
The present invention provides a catalyst composition for the reductive amination of a lower aliphatic alkane derivative. The catalyst composition comprises nickel and rhenium as active metals. More particularly, the catalyst comprises from about 2 to about 75 weight percent nickel and has a nickel to rhenium weight percent ratio of from about 1:1 to about 200:1. The catalyst is supported on an alumina-silica support which contains from about 5 to about 65 weight percent silica and has a BET surface area of from about 30 to about 450m
2
/g. The catalyst optionally comprises boron and has a boron to nickel weight percent ratio less than or equal to about 1. The nickel content of the catalyst, the nickel to rhenium and boron to nickel weight percent ratios, the support surface area, and the silica content of the support are selected to provide the catalyst composition with a specified activity, and to provide a particular mix of polyamine products when the lower aliphatic
Bartley William J
Cook Ronald Gary
Curry Kendrick Edward
Mierau Stefan Kent
Nguyen Cam N.
Silverman Stanley S.
Union Carbide Chemicals & Plastics Technology Corporation
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