Process for the regeneration of zeolite catalysts
A process for the regeneration of a zeolitic catalyst which is at least partially exhausted by use in the synthesis of optionally substituted methylenedianiline (MDA) and derivatives thereof, or of a mixture of optionally substituted MDA and derivatives thereof, with a higher homologous product the process involving washing said catalyst with an aromatic compound having at least one substitutent on the aromatic ring having activating characteristics with respect to the electrophilic substitution, in liquid or at least partially liquid phase.
1. A process for the regeneration of a zeolitic catalyst which is at least partially exhausted by use in the synthesis of optionally sudstituted methylenedianiline (MDA) and derivatives thereof or of a mixture of optionally substituted MDA and derivatives thereof with a higher homologous product, which comprises contacting said catalyst with an aromatic compound, in at least partially liquid phase wherein the aromatic compound comprises at least one substituent having activating characteristics with respect to electrophilic substitution as compared to the aromatic compound without the said substituent wherein the substituent having activating characteristics is selected from NH 2 , —NHR, —NR 2 , —OH, —O − , —OR 1 , or —NHCOR 2 substituents wherein R is hydrogen, a C 1 –C 8 alkyl, C 4 –C 10 cycloalkyl C 6 –C 12 aromatic radical. R 1 and R 2 represent a C 1 –C 4 (iso)alkyl, C 4 –C 10 cycloalkyl, aromatic, alkylaromatic or C 6 –C 10 arylakyl radical.
2. A process according to claim 1 in which the optionally substituted methylenedianiline (MDA) and derivatives thereof or the mixture of optionally substituted MDA and derivatives thereof with a higher homologous product comprise a compound of formula (I):
wherein R represents independently hydrogen, a C 1 –C 8 alkyl, C 4 –C 10 cycloalkyl C 6 –C 12 aromatic radical and n is an integer greater than or equal to one, such as to give a functionality ranging from 2 to 6.
3. A process according to any one of claims 1 and 2 wherein the at least one substituent of the aromatic ring has a strong activating effect and is selected from —NH 2 , —NHR, —NR 2 , —OH or —O − groups.
4. A process according to any one of claims 1 and 2 wherein the at least one substituent of the aromatic ring has an intermediate activating effect and is selected from —OR 1 , or —NHCOR 2 groups wherein R 1 and R 2 represent a C 1 –C 4 (iso) alkyl, C 4 –C 10 cycloalkyl, aromatic, alkylaromatic or C 6 –C 10 arylalkyl radical.
5. A process according to claim 1 wherein the aromatic compound is selected from phenol and aniline.
6. A process according to claim 1 wherein the catalyst is selected from zeolites with a “spaciousness” index ranging from 2.5 to 19, or silico-aluminas amorphous to X-rays, with a molar ratio SiO 2 /AI 2 O 3 from 10/1 to 500/1 and having a surface area from 500 to 1000 m 2 /g, a porosity from 0.3 to 0.6 ml/g and a pore diameter from 2 to 50 nm.
7. A process according to claim 1 in which the optionally substituted MDA and derivatives thereof and, if present, a higher homologous product are produced by a process comprising the re-arrangement reaction of the corresponding aminal intermediate of the condensation reaction between formaldehyde and optionally substituted aniline or a derivative thereof at elevated temperature.
8. A process according to claim 7 in which the catalyst is contacted with the aromatic compound at a temperature higher than that of the condensation and/or re-arrangement reaction in which the optionally substituted MDA and derivatives thereof is produced.
9. A process according to any one of claims 7 and 8 in which the catalyst is contacted, with the aromatic compound in equicurrent or concurrent or countercurrent flow with respect to the flow of the process reactants used to make the product.
10. A process according to claim 1 wherein the contacting of the catalyst with the aromatic compound takes place at a temperature ranging from 100 to 400° C.
11. A process for the regeneration of a zeolitic catalyst which is at least partially exhausted by use in the synthesis of optionally substituted methylenedianiline (MDA) and derivatives thereof or of mixtures of optionally substituted MDA and derivatives thereof with a higher homologous product by a process comprising the re-arrangement reaction of the corresponding aminal intermediate of the condensation reaction between formaldehyde and optionally substituted aniline or a derivative thereof, which regeneration process comprises contacting, said catalyst with an aromatic compound, in at least partially liquid phase and at a temperature higher than that of the condensation and/or re-arrangement reaction in which the optionally substituted MDA and derivatives thereof is produced wherein the aromatic compound comprises a substituent having activating characteristics with respect to electrophilic substitution as compared to the aromatic compound without the said substituent wherein the substituent having activating characteristics is selected from NH 2 , —NHR, —NR 2 , —OH, —O − , —OR 1 , or —NHCOR 2 substituents wherein R is hydrogen, a C 1 –C 8 alkyl, C 4 –C 10 cycloalkyl C 6 –C 12 aromatic radical, R 1 and R 2 represent a C 1 –C 4 (iso)alkyl, C 4 –C 10 cycloalkyl, aromatic, alkylaromatic or C 6 –C 10 arylakyl radical.