Synthesis of a crystalline silicoaluminophosphate

Abstract

The present invention is a method for synthesizing non-zeolitic molecular sieves which have a three dimensional microporous framework comprising [AlO 2 ] and [PO 2 ] units. In preparing the reaction mixture, a surfactant is used, coupled with non-aqueous impregnation to prevent acid sites from being destroyed by water during Pt impregnation. The superior SAPO exhibits higher activity and selectivity especially in catalytic hydroisomerization of waxy feeds, due to the presence of medium-sized silica islands distributed throughout the SAPO.

That which is claimed is: 
     
         1 . A crystalline silicoaluminophosphate intermediate pore molecular sieve having a three dimensional microporous framework structure of [AlO 2 ] and [PO 2 ] units wherein the ratio of Si atoms coordinated as Si (3 Al1Si) to that coordinated as Si(4Si) is at least 0.5, and the presence of Si atoms coordinated as Si(4Al) less than 40 mol. %. 
     
     
         2 . The molecular sieve of  claim 1  wherein the ratio of Si atoms coordinated as Si(3Al1Si) to that coordinated as Si(4Si) is at least 0.8, and the presence of Si atoms coordinated as Si(4Al) is less than 30 mol. %. 
     
     
         3 . The molecular sieve of  claim 1  wherein the ratio of Si atoms coordinated as Si(3Al1Si) to that coordinated as Si(4Si) is at least 1, and the presence of Si atoms coordinated as Si(4Al) is less than 25 mol. %. 
     
     
         4 . The molecular sieve of  claim 1  wherein the molecular sieve comprises a mean mesopore diameter of less than 200 angstroms. 
     
     
         5 . The molecular sieve of  claim 1  wherein the molecular sieve comprises a mean mesopore diameter of less than 195 angstroms. 
     
     
         6 . The molecular sieve of  claim 1  wherein the molecular sieve comprises a mean mesopore diameter of less than 190 angstroms. 
     
     
         7 . The molecular sieve of  claim 1 , wherein the sieve is selected from the group consisting of AEL, ATO and AFO. 
     
     
         8 . The molecular sieve of  claim 7 , wherein the sieve is AEL. 
     
     
         9 . The molecular sieve of  claim 1 , which was loaded with a Group VIII metal by means of non-aqueous impregnation. 
     
     
         10 . The molecular sieve of  claim 1 , wherein the ratio of Si atoms coordinated as Si(3Al1Si) to that coordinated as Si(4Si) is in the range from about 0.5 to about 3.5. 
     
     
         11 . The molecular sieve of  claim 2 , wherein the ratio of Si:atoms coordinated as Si(3Al1Si) to that coordinated as Si(4Si) is in the range from about 1.0 to about 3.0. 
     
     
         12 . The molecular sieve of  claim 3 , wherein the ratio of Si atoms coordinated as Si(3Al1Si) to that coordinated as Si(4Si) is in the range from about 1.0 to about 2.0. 
     
     
         13 . The molecular sieve of  claim 7 , wherein the % Si dispersed is in the range from about 5 to about 40, preferably in the range from about 5 to about 30, and most preferably in the range from about 10 to about 25. 
     
     
         14 . A process for preparing a crystalline silicoaluminophosphate molecular sieve according to  claim 1  which comprises
 (a) preparing an aqueous reaction mixture containing a reactive source of silicon, a reactive source of aluminum, a reactive source of phosphorus, a surfactant and an organic templating agent, said reaction mixture having a composition expressed in terms of mole ratios of oxides of:
     a R:Al 2 O 3   :n P 2 O 5   :q SiO 2   :b H 2 O 
 
 wherein R is an organic templating agent; “a” has a value large enough to constitute an effective amount of R; “b” has a value such that there are 10 to 40 moles of H 2 O per mole of aluminum oxide; said reaction mixture having been formed by controlling the molar ratio of the templating agent to phosphorus source in the reaction mixture to be greater than about 0.05 before the molar ratio of aluminum source to phosphorus source in the reaction mixture becomes greater than about 0.5; 
 (b) heating the reaction mixture at a temperature and a time sufficient until crystals of silicoaluminophosphate are formed; combining the crystals of silicoaluminophosphate with an active source of a hydrogenation component dissolved in a non-aqueous solvent and removing substantially all of the non-aqueous solvent at a temperature and for a time sufficient to produce non-zeolitic silicoaluminophosphate molecular sieve particles; and 
 (c) recovering the non-zeolitic silicoaluminophosphate molecular sieve particles. 
 
     
     
         15 . The process of  claim 14 , wherein the molar ratio of templating agent to phosphorus is greater than about 0.1 before the aluminum to phosphorus molar ratio reaches about 0.5. 
     
     
         16 . The process of  claim 14 , wherein the molar ratio of templating agent to phosphorus source is greater than about 0.2 before the aluminum source to phosphorus source molar ratio reaches about 0.5. 
     
     
         17 . The process of  claim 14 , wherein the surfactant is added in the substantial absence of a silicon source. 
     
     
         18 . The process of  claim 14 , wherein the source of silicon is SiO 2 . 
     
     
         19 . The process of  claim 14 , wherein the source of aluminum is aluminum isopropoxide. 
     
     
         20 . The process of  claim 14 , wherein the source of phosphorus is phosphoric acid. 
     
     
         21 . The process of  claim 14 , wherein, in step (a), the surfactant is dissolved in alcohol in the substantial absence of the silicon source. 
     
     
         22 . The process of  claim 14 , wherein the aqueous reaction mixture additionally comprises an alcohol. 
     
     
         23 . The process of  claim 14  wherein “b” has a value such that there are 20 to 50 moles of H 2 O per mole of Al 2 O 3 . 
     
     
         24 . The process of  claim 14  wherein “a” has a value such that there are from 0.2 to 2.0 moles of R per mole of alumina. 
     
     
         25 . The process of  claim 14  wherein “a” has a value such that there are from 0.8 to 1.2 moles of R per mole of Al 2 O 3 . 
     
     
         26 . The process of  claim 14  where in the organic templating agent is selected from the group consisting of di-n-propylamine and diisopropylamine or a mixture thereof. 
     
     
         27 . The process of  claim 14  wherein the organic template is di-n-propylamine. 
     
     
         28 . The process of  claim 14  wherein the surfactant is selected from C8+ alkylamines. 
     
     
         29 . The process of  claim 28  wherein the surfactant is hexadecylamine. 
     
     
         30 . The process of  claim 14  wherein the alcohol is selected from the group consisting of C1-C8 alcohols. 
     
     
         31 . The process of  claim 14  wherein the alcohol is 1-pentanol. 
     
     
         32 . The process of  claim 14  wherein the crystallite size of the recovered crystals are less than 1 micron. 
     
     
         33 . The process of  claim 14  wherein the temperature of the heating ranges from 150° C. to 200° C. 
     
     
         34 . A process for converting hydrocarbons comprising contacting a hydrocarbonaceous feed at hydrocarbon converting conditions with a crystalline intermediate pore silicoaluminophosphate molecular sieve having a three dimensional microporous framework structure of [AlO 2 ] and [PO 2 ] units wherein the ratio of Si atoms coordinated as Si(3Al1Si) to that coordinated as Si(4Si), as determined by  29 Si MAS NMR, is at least 0.5, the presence of Si atoms coordinated as Si(4Al) is less than 40 mol. %, and the molecular sieve comprises a mean mesopore diameter of less than 200 angstroms.