Aromatization catalyst and preparation process and use thereof
An aromatization catalyst and preparation process and use thereof is set forth. The catalyst comprises an inorganic oxide and a modified Ga-ZSM-5 zeolite, which comprises a modified ZSM-5 zeolite with a hierarchical macro-meso-microporosity and gallium deposited in channels of and/or on surfaces of the modified ZSM-5 zeolite. The hierarchical porosity of the modified ZSM-5 zeolite in the catalyst can reduce diffusion resistance of products during the aromatization reaction, thereby retarding carbon depositing rate and substantially improving catalytic activity, aromatic hydrocarbon selectivity, stability and lifetime of the catalyst. When being used in aromatization of propane, the catalyst exhibits a high stability, a lifetime of more than 320 hours, and a selectivity to aromatic hydrocarbons of up to 73.3 wt. %.
1. An aromatization process for producing aromatic hydrocarbons from a lower alkane, comprising: contacting the lower alkane with an aromatization catalyst consisting of an inorganic oxide and a modified Ga-ZSM-5 zeolite consisting of a modified ZSM-5 zeolite with a hierarchical macro-meso-microporosity and gallium deposited in channels of or on surfaces of the modified ZSM-5 zeolite, or both;
wherein the aromatization is carried out at a temperature of 500° C. to 550° C. under normal pressure at a weight hourly space velocity of 0.3 h −1 to 2 h −1 ,
wherein a process for preparing the aromatization catalyst comprises:
(a) adding a silicon source into a mixed aqueous solution containing an aluminum source and a first structure directing agent to perform a hydrothermal reaction so as to obtain a first solid product, which is then subjected to calcination to obtain a ZSM-5 zeolite precursor;
(b) mixing the ZSM-5 zeolite precursor with water and a second structure directing agent together to perform a hydrothermal treatment so as to obtain a second solid product, which is then subjected to calcination;
(c) subjecting a product resulting from the calcination in step (b) to an alkali treatment so as to obtain a hierarchical ZSM-5 zeolite;
(d) subjecting the obtained zeolite to be modified with ammonium ions and then calcined to obtain the modified ZSM-5 zeolite;
(e) subjecting the modified ZSM-5 zeolite to be ion-exchanged with a solution of gallium salt and then to be calcined to obtain the modified Ga-ZSM-5 zeolite; and
(f) mixing the modified Ga-ZSM-5 zeolite with an inorganic oxide precursor, followed by shaping, drying, and then calcination, to yield the catalyst.
2. The process according to claim 1 , wherein the lower alkane comprises one or more of C 2 -C 4 alkanes.
3. The process according to claim 2 , wherein the lower alkane is propane and/or butane.
4. The process according to claim 3 , wherein the lower alkane is propane.