Nan Li,Penny Xiao,Weijie Liu,Liying Liu,Zijian Wang,Jian Wang,Peng Gao,Qi Wu,Xinchao Ma,Gang Kevin Li
Compared with traditional commercial adsorbent zeolite pellets, binder-free molecular sieves can provide better adsorption performance. In this paper, we reported a novel method to synthesize binder-free zeolite X pellets (BF-Z), that is, zeolite X powder was intricately combined with halloysite nanotubes (HNTs) using hydroxypropyl methylcellulose (HPMC), and then the sample was calcinated to form crystals, where HPMC was decomposed and HNTs was also completely converted into binder-free X zeolite. The synthesized BF-Z showed the highest CO 2 adsorption capacity of 4.98 mmol/g at 303 K and 1 bar, compared with commercial NaX zeolites produced by Jianlong, Sigma and UOP companies. Calculated by IAST model, the separation coefficient of CO 2 to N 2 (CO 2 /N 2 = 25/75) on BF-Z is 74 at 303 K and 1 bar. The great separation performance of CO 2 from N 2 (CO 2 /N 2 = 25/75) was also exhibited in breakthrough experiments and a designed VSA process. Compared with commercial NaX (UOP), in breakthrough experiment, BF-Z presented high CO 2 adsorption capacity and rapid adsorption rate; and in designed thirty six-step vacuum swing adsorption process (VSA), the six-bed VSA system using BF-Z as adsorbents demonstrated excellent separation performance such as high CO 2 purity and recovery, low energy consumption and enhanced CO 2 production capacity. The notable efficacy of BF-Z in CO 2 adsorption and separation underscores its promising utility in both commercial and industrial settings.
The side-chain alkylation of toluene represents a novel, environmentally friendly, and low cost route for the production of styrene . However, the yield of styrene produced in this way is currently low, and the mechanism responsible for the side-chain alkylation of toluene is poorly understood. Furthermore, the reason for the higher catalytic efficiency of CsX over NaX and KX remains unclear. In this work, the free radical mechanism of the side-chain alkylation of toluene over basic zeolite X has been elucidated using quantum chemical calculations , together with isotope tracing experiments and the reaction between p -nitrotoluene and methanol. The adsorption isotherm of methanol showed that Cs + ions could block methanol from accessing the β-cage, which is where the side-chain alkylation reaction occurred. Furthermore, the H–D exchange results between toluene and deuterated toluene (C 6 D 5 CD 3 ) showed that CsX was more efficient as a catalyst than KX for the conversion of toluene to the corresponding benzyl radical (C 6 H 5 CH 2 • ). These two results therefore explain the higher catalytic activity of CsX towards side-chain alkylation than KX. Based on the free radical mechanism, the selectivity of styrene could be increased from 17.4% to 59.4% using CO 2 as carrier gas instead of N 2 .
危险品化学品经营许可证（带存储）