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In this study, we investigated the application of an acidic titanium dioxide catalyst in fixed bed reactors for the isomerization of α-pinenes.

Summary of the synthesis, structures and catalytic applications of Zr- and Ti-based MOFs.

The service life of HY zeolite is 480 h under industrial conditions, and it can be regenerated by roasting.

Al-Incorporated sulfated zirconia with improved and stabilized surface sulfur species was synthesized via the co-precipitation method and used as an effective catalyst to remove trace olefins from aromatics in a fixed-bed reactor. The textural and chemical properties of various catalysts were characterized by XRD, 27Al MAS NMR, N2 adsorption, EA, XPS, H2-TPR, FT-IR, and pyridine-infrared (IR) spectroscopy techniques to elucidate the Al promoting effect on acid centres and catalytic performance. The results demonstrated that incorporating Al into zirconia could effectively stabilize the tetragonal zirconia with small grain size and improve surface sulfur species, thereby balancing the distribution of Bronsted and Lewis acid sites. Consequently, sulfated zirconia incorporating Al at the level of Al/Zr < 7.5 mol% exhibited more outstanding catalytic activity and stability under a long reaction time compared with conventional sulfated zirconia. Notably, superior reusability with a negligible drop in olefins conversion over five reaction cycles was obtained in the presence of the Al2.50-SZ. The alkylation reaction process of olefins with aromatics was further investigated by the GC-MS technique when Alx-SZ was used as the catalyst.

The hydrogenation catalyst plays an important role in removing trace olefins from aromatics. In this work, a Cu/ZnO/montmorillonite catalyst was developed. The Cu/ZnO/montmorillonite catalyst is not only comparable in performance to the noble metal Pt/montmorillonite catalyst, but also has greater potential because the activity of the catalyst at low hydrogen flow is almost the same as that at high hydrogen flow. Moreover, aromatic cracking will not occur under the action of the Cu/ZnO/montmorillonite catalyst. The activity of the modified catalyst used to remove olefins is stable at about 92% at low weight hourly space velocity (WHSV). The three functions of ZnO are summarized as follows: (i) Zinc oxide is beneficial to restore the BET surface area of the Cu-based catalyst. (ii) Zinc oxide can improve the amount of Cu that can be reduced by hydrogen. (iii) ZnO increases the grain size of Cu2(NO3)(OH)3, resulting in a higher reduction temperature for Cu-based catalysts.

Metallic oxides were introduced into the synthesis of sulfated zirconia. Catalytic activity was tested by an olefin removal reaction. By combining the analysis from the aspect of catalyst morphology, sulfur state and surface acid property, we concluded that the incorporation of metallic oxides has three important positive effects on the environmental friendly solvent-free preparation: (i) it inhibited the phase transition during calcination and promoted the existence of tetragonal ZrO2, which is recognized as the valid phase; (ii) it increased the amount of S, especially S6+, which is the source of active sites; and (iii) it adjusted the surface acid property, extended the single service lifetime and reduced the deactivation rate.

Herein, a core–shell H-IM-5@meso-SiO2 hybrid material was synthesized by reversing the charge of the external surface of IM-5 crystals to a positive charge by PDDA that could induce an oriented self-assembly formation of the meso-SiO2 shell. The as-synthesized H-IM-5@meso-SiO2 composite was thereafter modified with phosphorus species to further enhance the selectivity of the target product. The sample morphology and structure were analyzed by electron microscopy technology, XRD, XPS and N2 adsorption–desorption. The effects of the meso-SiO2 shell and phosphorus species on sample acidity were investigated by NH3-TPD, FTIR spectroscopy and solid-state NMR measurements. The catalytic properties and characterization results revealed that the meso-SiO2 shell could passivate the external surface acids of the H-IM-5 crystals. The phosphorus modification could simultaneously adjust the surface acidity as well as the size of the pores and pore-openings. The TPD analysis of xylene showed that the sample surface acidity and geometric factors played important roles in the diffusion process of the diffusing molecules.

Heterogenization of homogeneous catalyst for acetylene carbonylation was carried out by preparing a series of Ni-modified catalysts (Ni-ZSM-5, Ni-IM-5 and Ni-MCM-41). Several important properties of the heterogeneous catalysts were determined by inductively coupled plasma atomic emission spectroscopy (ICP-AES), XPS, XRD, N2 adsorption, pyridine-FTIR, SEM and TGA. Moreover, we used various activity criteria to dissipate perturbing factors, when we focused on the influence of surface structure and active site distribution. The result that Ni-IM-5 had the greatest TOFNi = 5107 g acrylic acid per g Ni per h showed that the surface structure of samples did not influence the catalyst performance significantly. In addition, the highest ratio of nickel sites/acid sites in Ni-MCM-41 represented the best active site distribution. Thus, Ni-MCM-41 has the highest TOFcat = 70.6 g acrylic acid per g cat. per h. Furthermore, stability testing of the catalysts showed the Ni-MCM-41 could be used four times, while others only twice.

Al–MCM-41(30) was synthesized using Al2(SO4)3 as the aluminum source, Na2SiO3 as the silicon precursor and cetyltrimethylammonium bromide (CTAB) surfactant as the template. Heteropolyacid supported on the mesoporous sieves was prepared using the incipient wetness method. The heteropolyacid-modified Al–MCM-41 adsorbents significantly enhanced the desulfurization ability of LPG through a dynamic adsorption method in a fixed bed. Several factors that affect desulfurization, including PW12 loading, calcination temperature and the type of heteropolyacid, were investigated. The adsorbents were characterized by power X-ray diffraction, nitrogen adsorption, FTIR spectroscopy, thermogravimetric analysis and Py-IR spectroscopy. Al–MCM-41 mesoporous molecular sieves, with a hexagonal phase and a large specific surface area (1265.033 m2 g−1), were obtained. The experimental results showed that the PW12-modified Al–MCM-41 adsorbents with a 25 wt% PW12 loading had an optimum desulfurization ability. Also, a higher calcination temperature better promoted the removal of sulfur compounds by improving the acid amount of adsorbents. In addition, PW12-modified Al–MCM-41 is better than PMo12 modified Al–MCM-41 adsorbents in removing sulfur compounds from LPG. A total acid site number within a certain range on the adsorbent surface facilitated the desulfurization, and these values were obtained via Py-IR analyses.

The removal of sulfur compounds from liquid petroleum gas (LPG) was investigated using a fixed-bed flow sorption system. Copper-modified bentonite adsorbents significantly enhanced the desulfurization of LPG. Several factors that influence desulfurization, including the copper loading, the baking temperature, the valence state and the type of anion used, were investigated. The adsorbents were characterized by nitrogen adsorption, X-ray diffraction, inductively coupled plasma-atomic emission spectrometry, thermogravimetric analysis, Raman spectrometry and FTIR spectrometry. Optimum desulfurization with Cu(II)-modified bentonite adsorbents was obtained at a loading of 15 wt% Cu2+ and a calcination temperature of 150 °C. The Cu(I)-modified bentonite adsorbents were shown to be better than the Cu(II)-modified bentonite adsorbents in removing sulfur compounds from LPG; the anion used had no significant influence on the desulfurization ability of the Cu(II)-modified bentonite adsorbents. FTIR analyses showed that the surface Lewis acid sites contributed to the desulfurization process. The sulfur compounds were adsorbed over Cu(I)- and Cu(II)-modified bentonite by a direct sulfur–adsorbent interaction.