Catalyst – solid sorbent – or support therefor: product or process – Zeolite or clay – including gallium analogs – Clay
Reexamination Certificate
2000-01-13
2001-10-16
Yildirim, Bekir L. (Department: 1764)
Catalyst, solid sorbent, or support therefor: product or process
Zeolite or clay, including gallium analogs
Clay
C502S060000, C502S063000
Reexamination Certificate
active
06303531
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to high pore volume aluminum oxide composite particles, methods of their production, agglomerates and supported catalysts derived therefrom; and methods of using said catalysts.
BACKGROUND OF THE INVENTION
The art relating to particulate porous alumina particles, shaped catalyst supports derived therefrom, supports impregnated with various catalytically active metals, metal compounds and/or promoters and various uses of such impregnated supports as catalysts, is extensive and relatively well developed.
While the prior art shows a continuous modification and refinement of such particles, supports, and catalysts to improve their catalytic activity, and while in some cases highly desirable activities have actually been achieved, there is a continuing need in the industry for improved catalyst supports and catalysts derived therefrom, which have enhanced activity and life mediated through a desirable balance of morphological properties.
Alumina is useful for a variety of applications including catalyst supports and catalysts for chemical processes, catalyst linings for automotive mufflers, and the like. In many of these uses it will be desirable to add catalytic materials, such as metallic ions, finely-divided metals, cations, and the like, to the alumina. The level and distribution of these metals on the support, as well as the properties of the support itself are key parameters that influence the complex nature of catalytic activity and life.
Alumina useful in catalytic applications has been produced heretofore by a variety of processes, such as the water hydrolysis of aluminum alkoxides, precipitation of alumina from alum, sodium aluminate processes and the like. High costs arise from the latter two methods because the quantity of by-products, such as sodium sulfate, actually exceed the quantity of desired product obtained, i.e., boehmite. Typically, the cost of boehmite will be 4 times as expensive as active alumina.
Generally speaking, while alumina from these sources can be used for catalyst supports, such use is subject to certain limitations. This stems from the fact that for supported catalysts used in chemical reactions, the morphological properties of the support, such as surface area, pore volume, and pore size distribution of the pores that comprise the total pore volume are very important. Such properties are instrumental in influencing the nature and concentration of active catalytic sites, the diffusion of the reactants to the active catalyst site, the diffusion of products from the active sites, and catalyst life.
In addition, the support and its dimensions also influence the mechanical strength, density and reactor packing characteristics, all of which are important in commercial applications.
Hydroprocessing catalysts in petroleum refining represent a large segment of alumina-supported catalysts in commercial use. Hydroprocessing applications span a wide range of feed types and operating conditions, but have one or more of common objectives, namely, removal of heteroatom impurities (sulfur, nitrogen, oxygen, metals), increasing the H/C ratio in the products (thereby reducing aromatics, density and/or carbon residues), and cracking carbon bonds to reduce boiling range and average molecular weight.
More particularly, the use of a series of ebullated bed reactors containing a catalyst having improved effectiveness and activity maintenance in the desulfurization and demetallation of metal-containing heavy hydrocarbon streams are well known.
As refiners increase the proportion of heavier, poorer quality crude oil in the feedstock to be processed, the need grows for processes to treat the fractions containing increasingly higher levels of metals, asphaltenes, and sulfur.
It is widely known that various organometallic compounds and asphaltenes are present in petroleum crude oils and other heavy petroleum hydrocarbon streams, such as petroleum hydrocarbon residua, hydrocarbon streams derived from tar sands, and hydrocarbon streams derived from coals. The most common metals found in such hydrocarbon streams are nickel, vanadium, and iron. Such metals are very harmful to various petroleum refining operations, such as hydrocracking, hydrodesulfurization, and catalytic cracking. The metals and asphaltenes cause interstitial plugging of the catalyst bed and reduced catalyst life. The various metal deposits on a catalyst tend to poison or deactivate the catalyst. Moreover, the asphaltenes tend to reduce the susceptibility of the hydrocarbons to desulfurization. If a catalyst, such as a desulfurization catalyst or a fluidized cracking catalyst, is exposed to a hydrocarbon fraction that contains metals and asphaltenes the catalyst will become deactivated rapidly and will be subject to premature replacement.
Although processes for the hydrotreating of heavy hydrocarbon streams, including but not limited to heavy crudes, reduced crudes, and petroleum hydrocarbon residua, are known, the use of fixed-bed catalytic processes to convert such feedstocks without appreciable asphaltene precipitation and reactor plugging and with effective removal of metals and other contaminants, such as sulfur compounds and nitrogen compounds, are not common because the catalysts employed have not generally been capable of maintaining activity and performance.
Thus, certain hydroconversion processes are most effectively carried out in an ebullated bed system. In an ebullated bed, preheated hydrogen and resid enter the bottom of a reactor wherein the upward flow of resid plus an internal recycle suspend the catalyst particles in the liquid phase. Recent developments involved the use of a powdered catalyst which can be suspended without the need for a liquid recycle. In this system, part of the catalyst is continuously or intermittently removed in a series of cyclones and fresh catalyst is added to maintain activity. Roughly about 1 wt. % of the catalyst inventory is replaced each day in an ebullated bed system. Thus, the overall system activity is the weighted average activity of catalyst varying from fresh to very old i.e., deactivated.
In general, it is desirable to design the catalyst for the highest surface area possible in order to provide the maximum concentration of catalytic sites and activity However, surface area and pore diameter are inversely related within practical limits. Sufficiently large pores are required for diffusion as the catalyst ages and fouls, but large pores have a lower surface area.
More specifically, the formulator is faced with competing considerations which often dictate the balance of morphological properties sought to be imparted to supports or catalysts derived therefrom.
For example, it is recognized (see for example, U.S. Pat. No. 4,497,909) that while pores having a diameter below 60 Angstroms (within the range of what is referred to herein as the micropore region) have the effect of increasing the number of active sites of certain silica/alumina hydrogenation catalysts, these very same sites are the first ones clogged by coke thereby causing a reduction in activity. Similarly, it is further recognized that when such catalysts have more than 10% of the total pore volume occupied by pores having a pore diameter greater than 600 Angstroms (within the region referred to herein generally as the macropore region), the mechanical crush strength is lowered as is the catalyst activity. Finally, it is recognized, for certain silica/alumina catalysts, that maximization of pores having a pore diameter between 150 and 600 Angstroms (approximately within the region referred to herein as the mesopore region) is desirable for acceptable activity and catalyst life.
Thus, while increasing the surface area of the catalyst will increase the number of the active sites, such surface area increase naturally results in an increase in the proportion of pores in the micropore region. As indicated above, micropores are easily clogged by coke. In short, increases in surface area and maximization of mesopores are antagonistic properties.
Moreover,
Lussier Roger Jean
Plecha Stanislaw
Wear Charles Cross
Maggio Robert A.
W. R. Grace & Co.,-Conn.
Yildirim Bekir L.
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