Adsorptive separation of 1,1,1,2-tetrafluoroethane/1,1-difluoro-2-chloroethylene over ion-exchanged Y zeolites

doi:10.3969/j.issn.0438-1157.2014.10.027

Abstract

Abstract: Using CaCl₂, La(NO₃)₃ and Ce(NO₃)₃ solutions, NaY was ion-exchanged to prepare CaY, LaY and CeY zeolites. Adsorptive removal of trace amount of 1,1-difluoro-2-chloroethylene (HCFC-1122) from 1,1,1,2-tetrafluoroethane product over NaY, CaY, LaY, and CeY zeolites were investigated. The structure and surface properties of fresh and regenerated adsorbents were characterized by X-ray diffraction, pyridine infrared spectra techniques and temperature programmed desorption of ammonia. Results show that the residual ratio of HCFC-1122 impurity in the eluate can be decreased to 1.0% over CaY，LaY and CeY zeolites via the formation of p-adsorption complexes between HCFC-1122 and Brønsted acid sites. The increase of intensity of Brønsted acid favors the formation of p-adsorption complexes, consequently decreasing adsorption temperature for complete removal of HCFC-1122 (CeY < LaY < CaY). Breakthrough adsorption capacity of HCFC-1122 at 220℃ increases in the order of CaY < LaY < CeY, since lower density of strong Brønsted and weak Lewis acid sites are favorable to lower degree polymerization initiated by p-adsorption complexes. The thermal regeneration of adsorbents is unsatisfactory, attributed to hardly removal of contaminant on the acid sites of saturated adsorbents during the thermal regeneration process.

Key words: ion-exchange, Y-type zeolite, adsorption, desorption, separation

摘要： 用CaCl₂、La（NO₃）₃和Ce（NO₃）₃溶液对NaY分子筛进行离子改性制备出CaY、LaY和CeY分子筛。将其及NaY为吸附剂，利用动态吸附法评价其吸附分离1，1，1，2-四氟乙烷（HFC-134a）产品中微量1，1-二氟-2-氯乙烯（HCFC-1122）的性能。同时采用X射线衍射（XRD）、吡啶红外（FTIR）和氨-程序升温脱附（NH₃-TPD）等手段对新鲜及再生后的吸附剂进行结构和表面性质表征。结果表明：CaY、LaY与CeY分子筛上的Brønsted酸中心可与HCFC-1122形成p-吸附配合物，从而将吸附流出气中HCFC-1122的残余率降低至1.0%以下；Brønsted酸强度越高，p-吸附配合物越容易形成，最低吸附温度越低（CeY

关键词: 离子交换, Y型分子筛, 吸附, 脱附, 分离

CLC Number:

TQ028.15

ZHANG Chuang, ZHANG Bo, WEI Mingquan. Adsorptive separation of 1,1,1,2-tetrafluoroethane/1,1-difluoro-2-chloroethylene over ion-exchanged Y zeolites[J]. CIESC Journal, 2014, 65(10): 3946-3952.

张闯, 张波, 尉明全. 离子改性Y分子筛吸附分离1,1,1,2-四氟乙烷/1,1-二氟-2-氯乙烯[J]. 化工学报, 2014, 65(10): 3946-3952.

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