| 摘要 |
Solid crystalline alumino silicate zeolites, used as catalysts for the hydration of ethylene oxide to ethylene glycol are characterized by a rigid three-dimensional network and a homogenous pore structure made up of uniform interstitial dimensions of at least 4 Angstrom units in cross-section. These catalysts are essentially dehydrated forms of crystalline siliceous zeolites containing varying quantities of sodium, calcium and aluminium with or without other metals. All or a portion of the sodium and calcium ions may be replaced by other ions. Chemically these zeolites may be represented by the general formula Ma 2/n O Al2O3 XSiO2, YH2O in which M is a metal having a valency n. Such zeolites are available commercially as members of the "A" series or "X" series. In the "A" series X in the above formula has an average value of 1,85/sB0,5 and Y a value from 6 to 0. A synthetic zeolite known as "Molecular Sieve 4A", for example, has interstitial spaces of about 4 Angstroms in diameter and in the hydrated form the formula Na12 (AlO2)12. (SiO2)12.27H2O. "Molecular Sieve 5A" has channels of about 5 Angstroms in diameter and all of the 12 sodium ions of the latter formula are replaced by 6 calcium ions. The "X" series of zeolites have a different molecular structure from that of the "A" series. For example, a suitable catalyst is "Molecular Sieve 13X" having the formula Na86[(AlO2)86(SiO2)106].267H2O with interstitial dimensions of about 13 Angstrom units, or "Molecular Sieve 10X" having interstitial dimensions of about 10 Angstrom units and in which a substantial proportion of the sodium ions of the 13X material is replaced by calcium. In the preparation of the sodium zeolites the sources of silica may be silica gel, silicic acid or sodium silicate. Alumina can be supplied by using activated alumina, gamma alumina, alpha alumina, aluminium trihydrate or sodium aluminate. Sodium hydroxide may suitably be used as the source of sodium ions. The crystals obtained are activated by dehydration. On the formation of zeolites of the "A" series the reaction mixture should have a molar composition, expressed as mixtures of oxides, within the molar ranges SiO2/Al2O3 of 0,5 to 2,5, Na2O/SiO2 of 0,8 to 3,0 and H2/Na2O of 35 to 200. In the case of the X series the corresponding ranges are 3 to 5, 1,2 to 1,5 and 35 to 60. The sodium ions may be replaced partially or completely by other metal cations, e.g. Li, K, Ca, Sr, Mg, Cu, Co, Zn, Ag, Ni and ammonium.ALSO:Ethylene glycol is produced by reacting ethylene oxide with water in the presence of a catalyst consisting of a solid crystalline alumino-silicate zeolite, characterized by a rigid three-dimensional network and a homogenous pore structure made up of uniform interstitial dimensions of at least 4 in cross-section. The alumino-silicate zeolites used as catalysts are essentially dehydrated forms of crystalline siliceous zeolites containing sodium, calcium and aluminium with or without other metals. The preferred temperature for carrying out the process is in the range 30-150 DEG C. The ethylene oxide may be prepared in situ by using a feed containing ethylene water and oxygen and to simultaneously convert the ethylene to ethylene oxide and hydrate the ethylene oxide to ethylene glycol. |
