Modified crystalline aluminosilicate for dehydration of alcohols
The present invention relates to a catalyst composition comprising a modified crystalline aluminosilicate of the Framework Type FER having Si/Al framework molar ratio greater than 20 characterized in that in said modified crystalline aluminosilicate the ratio between the strong acid sites and the weak acid sites, S/W, is lower than 1.0 and having the extra framework aluminum (EFAL) content lowered to less than 10 wt % preferably 5 wt % even more preferably less than 2 wt % measured by 27 Al MAS NMR. The present invention further relates to a process for producing olefins from alcohols in presence of said catalyst composition.
1. A catalyst composition, for the dehydration of alcohols to olefins having the same number of carbons, comprising a modified crystalline aluminosilicate wherein
said modified crystalline aluminosilicate is of the Framework Type FER having Si/Al framework molar ratio greater than 20;
wherein said modified crystalline aluminosilicate comprises an extra framework aluminum, (EFAL) content lower than 15 wt % as measured by 27 Al MAS NMR;
wherein said modified crystalline aluminosilicate comprises a ratio between the strong acid sites and the weak acid sites, S/W which is lower than 1.0; the ratio S/W being measured by temperature-programmed desorption of ammonia and being determined by the ratio of the peak area of ammonia desorbed above 340° C. to that desorbed below 340° C.; and
said modified crystalline aluminosilicate is prepared from a crystalline aluminosilicate which is not steamed and is prepared with either one or both of the following treatments:
said crystalline aluminosilicate is treated with an organic acidic medium, an organic medium, or combinations thereof;
strong acid sites of said crystalline aluminosilicate are selectively poisoned with alkali salts or alkaline earth salts or silver so that the weight percent of alkali or alkaline earth or silver on the catalyst composition is of at least 0.5% weight, as measured by chemical analysis with the method ASTM UOP961-12.
2. A catalyst composition according to claim 1 wherein said modified crystalline aluminosilicate is ferrierite.
3. A catalyst composition according to claim 1 wherein said modified crystalline aluminosilicate is prepared without being calcined or with a calcination in a calcination reactor at a temperature not higher than 600° C. and with a temperature increase of less than 10° C./min, for a period of at least 30 min and under a gas flow containing at most 1000 ppm volume of water measured at the inlet of the calcination reactor.
4. A catalyst composition according to claim 1 wherein said acidic medium or said organic medium is selected from the group consisting of citric acid, tartaric acid, maleic acid, ethylene di-amine tetracetic acid (EDTA), or their corresponding salts.
5. A catalyst composition according to claim 1 wherein said modified crystalline aluminosilicate of the Framework Type FER has Si/Al framework molar ratio ranging from 20 to 150.
6. A catalyst composition according to claim 1 wherein said modified crystalline aluminosilicate of the Framework Type FER has a ratio between the strong acid sites and the weak acid sites, S/W, lower than 0.96.
7. A catalyst composition according to claim 1 wherein said modified crystalline aluminosilicate has a content in metals or cations thereof lower than 1000 wt ppm measured with the method ASTM UOP961-12, said metals belonging to columns 3 to 12 of the Periodic Table excluding silver.
8. A catalyst composition according to claim 1 wherein said modified crystalline aluminosilicate comprises the sequences —[—Al—O(H)—Si—]— and —[—Al—O(X)—Si—]— wherein X is alkali ions, alkaline earth ions or silver ions, the sequence —[—Al—O(X)—Si—]— representing less than 75% wt based on the total amount of sequences —[—Al—O(H)—Si—]— and —[—Al—O(X)—Si—]— in said modified crystalline aluminosilicate as measured via solid-state 29 Si NMR.