Method for removing organic residue from as-synthesized ZSM-18
AssigneeMobil Oil Corporation
InventorYing-Yen P. Tsao
Life of this patent
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Abstract
An improved method for removing organic residue from ZSM-18 which can be used during zeolite synthesis or with an as-synthesized ZSM-18. When used during synthesis, a minute amount of noble metal is incorporated into the ZSM-18. Alternatively, a noble metal-containing precursor is impregnated onto as-synthesized ZSM-18. Thereafter, ZSM-18 united with the noble metal is reduced in hydrogen at 200.degree. C. for about 1 hour. Next, ZSM-18 united with the noble metal is calcined at 300.degree. C. for 10-24 hours, and subsequently at 500.degree. C. for 1-3 hours thereby producing a ZSM-18 material that is free of organic residue.
Claims19
A method for removing a residue from an as-synthesized form of ZSM-18, resultant from an organic directing agent being 1,3,4,6,7,9-hexahydro-2,2,5,5,8,8-hexamethyl-2H-benzo [1,2C:3,4-C':5,6C"] tripyrolium trihydroxide, said method comprising the steps of:
- a) impregnating a noble metal-containing precursor onto as-synthesized ZSM-18 in an amount sufficient to deposit a noble metal onto said ZSM-18 when reduced with hydrogen;
- b) reducing the as-synthesized ZSM-18 in hydrogen at a temperature of about 175.degree. to 225.degree. C. for about 0.5 to 2 hours thereby reducing said precursor to a free metal;
- c) calcining the ZSM-18 from step b) in air at about 275.degree. to 325.degree. for about 10 to 24 hours;
- and
- d) calcining said ZSM-18 from step c) at about 450.degree. to about 550.degree. C. in air for about 1 to 7 hours thereby removing said residue from said catalyst without suffering crystallinity loss.
A method for preparing ZSM-18 which is essentially free of residual organic directing agent, said method comprising the steps of:
- (i) forming an aqueous reaction mixture capable of forming ZSM-18, said reaction mixture comprising a directing agent which is 1,3,4,6,7,9-hexahydro 2,2,5,5,8,8-hexamethyl-2H-benzo (1,2-C:-3,4-C':5,6-C") tripyrolium trihydroxide, a source of sodium cations, a source of silica and a source of alumina, said reaction mixture having a composition, expressed in terms of mole ratios of T and oxides, as follows:
- ______________________________________ SiO.sub.2 /Al.sub.2 O.sub.3 = 5-30 Na.sub.2 O/Al.sub.2 O.sub.3 = 0.2-5 H.sub.2 O/Al.sub.2 O.sub.3 = 200-1500 T/Al.sub.2 O.sub.3 = 1-10 ______________________________________
- where T is said directing agent;
- (ii) placing within said reaction mixture a noble metal-containing precursor in an amount sufficient to occlude the noble metal on said ZSM-18 when reduced with hydrogen;
- (iii) maintaining said reaction mixture of step (i) under conditions sufficient to form crystals of ZSM-18;
- (iv) separating said ZSM-18 crystals from step (iii) from mother liquor of said reaction mixture by filtering and washing said crystals with water, whereby an as-synthesized form of ZSM-18 is obtained, said as-synthesized ZSM-18 having a residue of said organic directing agent in pores of said ZSM-18 and a noble metal-containing precursor occluded thereon;
- (v) contacting said ZSM-18 from step (iv) with hydrogen under conditions sufficient to reduce noble metal contained in said precursor to a free metal;
- (vi) calcining in air the ZSM-18 from step (v) with the noble metal thereon under conditions sufficient to substantially remove said residue;
- and
- (vii) calcining in air said ZSM-18 from step (vi) under conditions sufficient to remove any remaining residue from said ZSM-18 without suffering crystallinity loss.
A method for removing an organic residue from an as-synthesized form of ZSM-18, said method comprising the steps of:
- a) impregnating a noble metal-containing precursor onto as-synthesized ZSM-18 in an amount sufficient to deposit a noble metal onto said ZSM-18 when reduced with hydrogen;
- b) reducing the as-synthesized ZSM-18 in hydrogen at a temperature of about 175.degree. to 225.degree. C. for about 0.5 to 2 hours thereby reducing said precursor to a free metal;
- c) calcining the ZSM-18 from step b) in air at about 275.degree. to 325.degree. for about 10 to 24 hours;
- and
- d) calcining said ZSM-18 from step c) at about 450.degree. to about 550.degree. C. in air for about 1 to 7 hours thereby removing said residue from said catalyst without suffering crystallinity loss.
Dependencies are inferred from the claim text.