GB1009943A - Selective catalytic conversion - Google Patents

Abstract

In the selective conversion of an organic compound at catalytic sites within the pores of a zeolitic alumino-silicate molecular sieve in the presence of a compound, present in feed or product, which might be converted at catalytic sites on the exterior of the molecular sieve, such latter conversion is inhibited by poisoning the exterior catalyst sites with a poison therefor of such size that it cannot enter the pores of the sieve. The dehydrohalogenation of terminal halohydrocarbons to olefins, the selective hydrogenation, dehydrogenation or combustion of normal aliphatic compounds in the presence of iso-aliphatic and aromatic hydrocarbons, the selective hydrogenation of smaller aromatic hydrocarbon molecules in the presence of larger, and the isomerization of olefins are referred to. Isobutylene and isoprene may be freed of straight chain impurities by selective hydrogenation or oxidation, n-butene may be obtained by selective dehydrogenation of n-butane in admixture with isobutane and olefins may be cracked to smaller molecule olefins with minimum side reactions. The molecular sieve of pore size less than 25 <\>rA and preferably about 5 <\>rA may be used as such or contain a suitable catalytic element within the pores introduced by deposition, by ion exchange or during the formation of the sieve, e.g. Ag, Cu, Al, H, Zn, Sr, Co, Au, K, Pt, Ni, NH4, Cd, Hg, Li, Mg, La and Ce. The sieve may be composited with a clay binder or dispersed in a matrix of an inorganic oxide gel. The catalyst poison used depends on the reaction to be inhibited; specified poisons are pyridine, quinoline, thiophene, benzothiophene, 3-methylthiophene, tricresylphosphate, acetophenone, pyrene, benzanthrone, purpurin, alizarin blue, 1,3,5-triaminoethyl benzene. They are used to treat the catalyst before the reaction and/or intermittently or continuously during the reaction in amounts of 1-10% by weight of catalyst or 0.01-10% by weight of feed. Specification 978,261 is referred to.ALSO:In the selective conversion of an organic compound at catalytic sites within the pores of a zeolitic alumino-silicate molecular sieve in the presence of a compound, present in feed or product, which might be converted at catalytic sites on the exterior of the molecular sieve, such latter conversion is inhibited by poisoning the exterior catalyst sites with a poison therefor of such size that it cannot enter the pores of the sieve. The selective dehydration of normal alcohols to ethers in the presence of branched chain alcohols, the hydrolysis of terminal halohydrocarbons to n-alcohols, and ester interchange and aldol condensations are referred to. Normal ethers may also be formed without isomerization of the product by dehydration of normal alcohols. The molecular sieve of pore size less than 25 <\>rA and preferably about 5 <\>rA may be used as such or contain a suitabe catalytic element within the pores introduced by deposition, by ion exchange or during the formation of the sieve, e.g. Ag, Cu, Al, H, Zn, Sr, Co, Au, K, Pt, Ni, NH4, Cd, Hg, Li, Mg, La and Ce. The sieve may be composited with a clay binder or dispersed in a matrix of an inorganic oxide gel. The catalyst poison used depends on the reaction to be inhibited; specified poisons are pyridine, quinoline, thiophene, benzothiophene, 3-methylthiophene, tricresylphosphate, acetophenone, pyrene, benzanthrone, purpurin, alizarin blue, 1,3,5-triaminoethyl benzene. They are used to treat the catalyst before the reaction and/or intermittently or continuously during the reaction in amounts of 1-10% by wt. of catalyst or 0.01-10% by wt. of feed. Specification 978,261 is referred to.ALSO:In the selective conversion of an organic compound at catalytic sites within the pores of a zeolitic alumino-silicate molecular sieve in the presence of a compound, feed or product, which might be converted at catalytic sites on the exterior of the molecular sieve, such latter conversion is inhibited by poisoning the exterior catalyst sites with a poison therefor of such size that it cannot enter the pores of the sieve. The selective dehydration of normal alcohols to ethers in the presence of branched chain alcohols, the hydrolysis or dehydrohalogenation of terminal halohydrocarbons to n-alcohols or olefins, the selective hydrogenation, dehydrogenation or combustion or normal aliphatic compounds in the presence of isoaliphatic and aromatic hydrocarbons, the selective hydrogenation of smaller aromatic hydrocarbon molecules in the presence of larger, the isomerization of olefins, and ester interchange and aldol condensations are referred to. Isobutylene and isoprene may be freed of straight chain impurities by selective hydrogenation or oxidation, n-butene may be obtained by selective dehydrogenation of n-butane in admixture with isobutane, olefins may be cracked to smaller molecule olefins with minimum side reactions and normal ethers may be formed without isomerization of the product by dehydration of normal alcohols. The molecular sieve of pore size less than 25 and preferably about 5 may be used as such or contain a suitable catalytic element within the pores introduced by deposition, by ion exchange or during the formation of the sieve, e.g. Ag, Cu, Al, H, Zn, Sr, Co, Au, K, Pt, Ni, NH4, Cd, Hg, Li, Mg, La and Ce. The sieve may be composited with a clay binder or dispersed in a matrix of an inorganic oxide gel. The catalyst poison used depends on the reaction to be inhibited; specified poisons are pyridine, quinoline, thiophene, benzothiophene, 3-methylthiophene, tricresylphosphate, acetophenone, pyrene, benzanthrone, purpurin, alizarin blue, 1,3,5-triaminoethyl benzene. They are used to treat the catalyst before the reaction and/or intermittently or continuously during the reaction in amounts of 1-10% by weight of catalyst or 0,01-10% by weight of feed. Specification 978,261 is referred to.