Improved structural stability and catalytic performance for CH4 reforming reaction of mesoporous MCM-41 analogs prepared by zeolitic subunits of MOR desilication

Smart Designs of Zeolite-Based Catalysts for Dry Reforming of Methane: A Review

“…139 In addition to the calcination temperature, a high desilication temperature enhanced the hydrolysis of SiO 3 2− and increased the OH − concentration, accelerating the MOR zeolite desilication rate. 140 In another work, the same phenomena were observed for the desilication of ZSM-5. 141 4.2.2. pH Values.…”

“…142 For example, mesoporous molecular sieves (TMM) with a highly stable structure were developed from the MOR zeolite desilication and zeolite subunits self-assembling in the aqueous solution containing Na 2 O•(3.3−3.4) SiO 2 , acting as both a supplementing silica source and a moderate basic medium with a buffering effect. 140 The similar effect of Na 2 O•(3.3−3.4) SiO 2 was exerted on the desilication of ZSM-5 zeolite. A high pH value facilitated the desilication; on the other hand, the minimum concentration of OH − was required for desilication, as seen from the disappearance of ZSM-5 crystal peaks.…”

“…Moreover, a weakened basicity is observed at a higher calcination temperature due to the dihydroxylation . In addition to the calcination temperature, a high desilication temperature enhanced the hydrolysis of SiO 3 2– and increased the OH – concentration, accelerating the MOR zeolite desilication rate . In another work, the same phenomena were observed for the desilication of ZSM-5 …”

“…Alkali treatment with a controlled pH value benefits the zeolite desilication in a solution with a relatively homogeneous distribution of OH – , which intensifies the hydrolysis of zeolite subunits . For example, mesoporous molecular sieves (TMM) with a highly stable structure were developed from the MOR zeolite desilication and zeolite subunits self-assembling in the aqueous solution containing Na 2 O·(3.3–3.4) SiO 2 , acting as both a supplementing silica source and a moderate basic medium with a buffering effect . The similar effect of Na 2 O·(3.3–3.4) SiO 2 was exerted on the desilication of ZSM-5 zeolite.…”

“…Consequently, the H 2 /CO ratio remained constant for Ni/TMM but dropped by more than 25% of the initial value for Ni/MCM-41 after hydrothermal treatment (Table ). As for the TZM support (decilication of ZSM-5 zeolite) in another work, the improved hydrothermal stability was partly due to the reduced silanol groups. Besides, the incorporation of AlO 4 of 5-rings and 6-rings generated negative charges in the TZM structure, which repelled the OH – ions responsible for the Si–O–Si hydrolysis …”