Catalyst With Improved Activity/Selectivity For Light Naphtha Aromatization (SABIC)

CATEGORY: CATALYSTS: LIGHT NAPHTHA
Catalyst With Improved Activity/Selectivity For Light Naphtha Aromatization (SABIC)
United States Patent Application 20160288108
Khanmamedova; Alla ;   et al.   October 6, 2016
Applicant: Saudi Basic Industries Corporation
Abstract
In an embodiment, a method for making a catalyst, comprises: forming a mixture comprising a germanium source, an alkali metal source, an aluminum source, and a silica source, wherein the mixture has a pH; adjusting the pH of the mixture to a value of greater than or equal to 9.5; crystallizing and calcining the mixture to form a zeolite; depositing platinum on the zeolite; and calcining the zeolite to form the final catalyst. The final catalyst is non-acidic and has an aluminum content of less than or equal to 0.75 wt % based on the total weight of the final catalyst excluding any binder and extrusion aide and a Si:Al2 mole ratio of greater than or equal to 125.
BACKGROUND
[0001] Zeolite is a crystalline hydrated aluminosilicate that can contain other metals in the framework of the zeolite crystal or that can be deposited, exchanged, or impregnated on the zeolite (i.e. on the surface or in the pores). A method for preparing a zeolite comprises: preparing an aqueous mixture of silicon oxide and sources of oxides of aluminum; and maintaining said aqueous mixture under crystallization conditions until crystals of zeolite form. In the crystalline structure, there are pores and channels that can be interconnected. The dimensions and configuration of these pores and channels allow access by molecules of certain sizes. Zeolites are used as catalysts for, among other things, isomerization, toluene disproportionation, transalkylation, hydrogenation, alkane oligomerization, and aromatization. Aromatization is a multi-step process that can comprise the steps of dehydrogenation of the hydrocarbon, cyclization of the dehydrogenated hydrocarbon, and aromatization of the cyclized hydrocarbon.
[0002] One such example of hydrocarbon aromatization is aromatization of naphtha. Naphtha is a mixture mainly of straight-chained, branched, and cyclic aliphatic hydrocarbons, light naphtha having from five to nine carbon atoms per molecule, and heavy naphtha having from seven to twelve carbon atoms per molecule. Typically, light naphtha contains naphthenes, such as cyclohexane and methylcyclopentane, and linear and branched paraffins, such as hexane and pentane. Light naphtha typically contains 60 to 99 weight percent (wt %) of paraffins and cycloparaffins. Light naphtha can be characterized as a petroleum distillate having a molecular weight range of 70 to 150 gram per mole (g/mol), a specific gravity range of 0.6 to 0.9 grams per cubic centimeter (g/cm.sup.3), a boiling point range of 50 to 320 degree Fahrenheit (.degree. F.) (10 to 160 degree Celsius (.degree. C.)), and a vapor pressure of 5 to 500 millimeter of mercury (mmHg) at room temperature. Light naphtha can be obtained from crude oil, natural gas condensate, or other hydrocarbons streams by a variety of processes, e.g., distillation.
[0003] A zeolite with one or both of improved selectivity and conversion for naphtha aromatization is desirable.
BRIEF SUMMARY
[0004] Disclosed herein is a catalyst, methods for making and using the same.
[0005] In an embodiment, a method for making a catalyst, comprises: forming a mixture comprising a germanium source, an alkali metal source, an aluminum source, and a silica source, wherein the mixture has a pH; adjusting the pH of the mixture to a value of greater than or equal to 9.5; crystallizing and calcining the mixture to form a zeolite; depositing platinum on the zeolite; and calcining the zeolite to form the final catalyst. The final catalyst is non-acidic and has an aluminum content of less than or equal to 0.75 wt % based on the total weight of the final catalyst excluding any binder and extrusion aide and a Si:Al.sub.2 mole ratio of greater than or equal to 125.
[0006] In another embodiment: a catalyst comprises: a zeolite comprising Si, Al, and Ge in the framework with Pt deposited thereon; wherein the catalyst has an Si:Al.sub.2 mole ratio of greater than or equal to 125, an Si:Ge mole ratio of 40 to 400, and an Na:Al mole ratio of 0.9 to 2.5, wherein the catalyst has an aluminum content of less than or equal to 0.75 wt %, wherein the catalyst is non-acidic.
[0007] In another embodiment: a method for the aromatization of hydrocarbons comprises: contacting an alkane containing 6 to 12 carbon atoms per molecule with a catalyst comprising: a zeolite comprising Si, Al, and Ge in the framework with Pt deposited thereon; wherein the catalyst has an Si:Al.sub.2 mole ratio of greater than or equal to 125, an Si:Ge mole ratio of 40 to 400, and an Na:Al mole ratio of 0.9 to 2.5, wherein the catalyst has an aluminum content of less than or equal to 0.75 wt % excluding any binder and extrusion aide.
[0008] The above described and other features are exemplified by the following detailed description.
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