Sustainable transformation of natural silica-rich solid and waste to hierarchical zeolites for sugar conversion to hydroxymethylfurfural (HMF)

Isolated Hf‐Isomorphously Substituted Zeolites for One‐Pot HMF Synthesis from Glucose

“…This suggests the high hydrophilic properties of the synthetic Sn-incorporated beta zeolite. As for the 29 Si CPMAS NMR experiment of the 485Hf-HZSM-5-NS, the most intense peak centered at −102 ppm was clearly observed, reflecting a large amount of Q 3 Si species (SiO) 3 Si(OX) (where X is assigned to Hf or Al or H) in such a sample. Among all possible Q 3 Si species, the 485Hf-HZSM-5-NS was made up of a large number of silanol groups, evidenced by the peak at 3743 cm −1 in Figure S9, Supporting Information.…”

“…The NMR spectra of the 268Hf-HBEA-NC, the 280Sn-HBEA-NC, and the unmodified HBEA-NC are shown in Figure S8, Supporting Information. The 29 Si CPMAS NMR spectra demonstrated the presence of Q 3 and Q 4 silicon (Si) sites, which were assigned to (SiO) 3 Si(OX) (where X is assigned to Hf/Sn or Al or H) and Si(OSi) 4 , respectively. [27] The resonance at about −110 ppm corresponds to Si(OSi) 4 species.…”

“…As expected, the glucose conversion over the 485Hf-HZSM-5-NS (41.4 ± 3.7%) was remarkably lower than that of the 429Hf-HBEA-NC (52.0 ± 4.1%) due to the limited accessibility of bulky substrate to active centers located in the restricted pore of the MFI framework. Although hierarchical features of the hierarchical ZSM-5 enable improving mass diffusion in intercrystalline frameworks due to the presence of unique void spaces derived from the self-assembly of nanosheets, [29] the relatively low average pore diameter of MFI (0.53 × 0.56 nm, 0.51 × 0.55 nm) as illustrated in Figure S3B,C, Supporting Information, compared to the kinetic diameter of www.advsustainsys.com glucose (0.7 nm) has still been a critical obstacle toward HMF production. Apart from the effect of pore cavities on the catalytic behavior, the acid properties of both frameworks are rather different.…”

Understanding the mechanism and kinetics of the formation and breaking of ring structures during silica polymerization: a computational study

“…[31][32][33] The smaller ring structure imparts rigidity to the framework, which helps in retaining the overall morphology of the porous materials. While rings are prominent in crystalline materials such as zeolites, [9][10][11] they are also formed in amorphous glasses, [34][35][36] gels (aerogels, 7,8 alcogels, 37,38 and hydrogels [4][5][6] ), nanoparticles, [1][2][3] and mesoporous materials, [12][13][14] playing a vital role in their applications. Therefore, the formation and retention of appropriate ring sizes in porous materials are quintessential for their successful application.…”

“…Silica polymerization by the sol–gel technique is used to prepare various silica polymorphs such as nanoparticles, 1–3 hydrogels, 4–6 aerogels, 7,8 zeolites, 9–11 mesoporous materials, 12–14 amorphous glass, 15,16 and dense quartz crystals. 17,18 These materials have properties such as porosity, channels and cages, mechanical strength, fractal dimensions, and active catalytic sites based on which they find application in areas ranging from petroleum refining to wastewater treatment.…”