Heterogeneous cobalt materials were important catalyst for the development of a more efficient cyclohexane oxidation process, however the catalytic performance of which should further be improved. Herein, hierarchical Silicalite-1 confined with cobalt as the active centers was hydrothermally synthesized, the chemical environment of Co and intracrystalline porosity were tuned, and the influences of which on cyclohexane oxidation was detailed studied. The cobalt in conventional Silicalite-1 was mainly four-coordinated. In the hierarchical catalyst prepared by silanization, intracrystalline mesopores in the 4.52–5.92 nm range were created, and the mesopore volume ranged from 0.127 to 0.193 cm3/g. More importantly, although the cobalt cations were usually in the tetra- and octahedral state, Si–O-Co bonds characterized with cobalt coordination number of 2.1–2.3 have been generated. The Si–O-Co bonds can further be recrystallized to Co3O4 nanoclusters under extended crystallization condition, and the coordination number of cobalt increased to 3.7. In cyclohexane oxidation, the activation energy (Ea) over cobalt decreased with the coordination number, the intracrystalline diffusion limitation was released by mesopores, and notably enhanced cyclohexane conversion (8.8

The crystalline defects are vitally important for the catalytic activity and stability of zeotype materials; however, the influences of which on the catalytic performance of TS-1 should further be studied. Herein, a modified hydrothermal synthesis process was developed to in situ tailor the framework defects of TS-1, and the physicochemical properties and catalytic performance were studied in detail. Generally, the nH2O/nSiO2 (5-20) of the precursor mixture was in situ tuned via distillation through the crystallization under 90-110 degrees C, and TS-1 with decreased framework defects can be directly synthesized during the following crystallization under 170 degrees C. When the nH2O/nSiO2 declined, the crystal size decreased; however, more intracrystalline mesopores (3.0-5.3 nm) can be introduced, the mesopore volume increased from 0.051 to 0.083 cm3/g. More importantly, the ratio of silicon species in Q4 (Si(OSi)4) to Q3 [Si(OSi)3(OH)] units increased from 29.9 to 55.0, and the hydroxyl groups in the nest or neighboring environments decreased more significantly than the surface silanol. Nevertheless, the titanium coordination states remained unchanged. Owing to the decreased framework defects, the weak acid sites declined from 191.5 to 160.5 mu mol NH3/g, the epoxide selectivity in butene epoxidation reaction increased from 97.4 to 98.1%, while the H2O2 efficiency was enhanced from 96.7 to 98.6%. More importantly, the catalytic stability of TS-1 was also improved.

FCC is an important process for light olefins production, but it's a challenge to enhance the ethylene selectivity. In view of the high selectivity of ethylene and propylene (SEP) of MTO and the similar process of FCC and MTO, methanol may be co-fed from the stripper units to improve the selectivity of light olefins (SLO), especially ethylene, of a conventional FCC process. Herein, the MTO performance of SAPO-34 under the stripper conditions was studied, and the influences of the coke from heavy oil cracking were analyzed. When MTO was performed following the conditions (500 degrees C, 7.5-35 h-1) in the FCC stripper, the SEP and SLO achieved 83-86% and 91-96%, respectively, the weight ratio of ethylene to propylene (mEe:mPe) was about 1.2-1.6, and dimethyl ether was not detected. Although more complicated coke was introduced by heavy oil, the active polymethylbenzenes can help retaining the SEP (82.2%) and SLO (89.3%), and the methanol utilization efficiency and mEe:mPe were enhanced from 92.5% to 1.21 to 95.3-95.9% and 1.34, respectively. More importantly, the SEP, SLO and mEe:mPe can further be enhanced to 85.6%, 91.6%, and 1.52, respectively when SAPO-34 with less strong acid sites was applied. Consequently, SAPO-34 may be used as an FCC catalysts promoter for the development of a modified FCC process with significantly enhanced SLO.

It's significance in enhancing the ethylene selectivity of MTO, however the partial regeneration and metal modification methods would reduce the lifetime of SAPO-34, and it's necessary to develop a method to simul-taneously improve the ethylene selectivity and catalytic stability. Herein, an industrial aluminum sol gelation strategy was reported, the influences of the pH value (2.8-4.0), gelation temperature (40-80 ?), and Al species were detailed studied. The SAPO-34 crystals can partially be eroded by the Al gel, and intra-crystalline mesopores (5.2-6.4 nm) can be created. However, aluminum species in the sol can be adsorbed, and the n(Al):(n(P) + n(Si)) of the catalyst increased from 0.86 to 0.96-1.32. Comparatively, the erosion and adsorption of Al species were more notable under higher pH value and gelation temperature conditions. Furthermore, the gelation can prevent the hydration of the crystals, but the isolated silicon species can be reassembled to silicon islands, and the strong acid centers increased from 0.45 mmol NH3/g to 0.54-0.69 mmol NH3/g. Although more coke can be brought about by the increased strong acids, the intra-crystalline diffusion limitation can be released by the mesopores, and the catalytic stability of SAPO-34 can be better retained. More importantly, the geometric effect has been intensified by the increased coke, and a significant increase (1.6-4.7%) in the initial ethylene selectivity and a slightly decrease (0.1-1.4%) in the selectivity of propylene and butenes was achieved, leading to enhanced selectivity of ethylene and propylene (S-EP, 86.6%), light olefins selectivity (S-LO, 94.6%), and ratio of ethylene to propylene (C-2(=):C-3(=), 1.44), especially under higher gelation temperature. The gelation strategy is efficient in enhancing the ethylene selectivity and improving the catalytic stability of SAPO-34, and it can be applied in the preparation of industrial MTO catalyst.

The silanization is an important approach for hierarchical zeolite preparation. Although the influences of the silanization conditions have been detailed studied, the differences in the reactivity of the zeolite precursor should further be analyzed. In this paper, hierarchical titanium silicalite-1 (HTS) was prepared with trimethoxy[3(phenylamino)propyl]silane (TMPAPS) under the nTMPAPS:nSi = 0.04-0.20 and nTi:nSi = 0.005-0.04 conditions, the changes of the corresponding physicochemical properties were analyzed, and the influences of the condensation activities between silicon/titanium to the organosialne were deduced and verified by density functional theory (DFT) calculations. Generally, more supermicropores and mesopores can be created in the metastable sponge-like HTS crystals with higher TMPAPS and titanium contents. In comparison, the free energy barrier in the condensation reaction with titanium (1.31 eV) is lower than silicon (1.55 eV), it's preferential to prepare HTS with more intracrystalline secondary porosity by increasing the nTi:nSi. More importantly, the titanium can be isolated by the organosilane, and HTS with more framework titanium can be synthesized by silanization.

A two-step hydrothermal approach for the synthesis of hierarchical SAPO-34 in the absence of any mesoporogen.

CHHP is the main product of the cyclohexane oxidation process, the rational design and preparation of solid catalysts are vital important for the development of an environmental benign CHHP conversion process. Herein, cobalt oxide encapsulated hydrophilic hierarchical Silicalite-1 was developed for CHHP conversion. In the presence of an organosilane, the encapsulation of cobalt oxide, creation of intracrystalline secondary porosity, and introduction of surface silanols were simultaneously achieved via hydrothermal synthesis. The particle size of the encapsulated cobalt oxide was about 4.7-6.3 nm, while the S-BET, V-T and V-ME are 527 m(2)/g, 0.417 cm(3)/g and 0.3 cm(3)/g, respectively. Moreover, the S BET further increases to 692 m(2)/g when the silanization process was intensified by surfactants, and the hydrophilic substrates could more easily be adsorbed by the catalyst for the abundant terminal silanols. Then, the dilute CHHP could selectively be adsorbed and activated by the catalyst, and a CHHP conversion of more than 99% could be achieved in 20min. More importantly, the catalyst exhibits outstanding activity in both the CHHP decomposition reactions and cyclohexane oxidation reaction with CHHP as the oxidant, the oxygen utilization efficiency (60%) and KA oil selectivity (120%) were notably improved. The stability of the catalyst is excellent, the activity retained after recycling for 20 times. This strategy is general, which could further be applied for the development of heterogeneous catalysts for more environmental benign chemical processes.

Titanium silicalite-1 (TS-1) is an important catalyst epoxidation, but the crystalline micropore is too small for alkene for some alkenes. Although the diffusion limitation would be relieved by intracrystalline mesopores, the catalytic performance should further be improved, considering the alkene conversion. Herein, molybdenum encapsulation was achieved during a silanization process for hierarchical TS-1 synthesis. Although the relative crystallinity decreased, more supermicropores of about 1.2-1.8 nm and mesopores in the 2-4 nm range have been created, leading to increased specific area, mesopore volume (V-ME), and total pore volume (V-T). Comparatively, the V-ME and V-T increased with the Mo content, and most of the Mo and Ti have been confined inside the crystals. Owing to the excellent activity of Mo and the improved accessibility, the catalytic performance was notably enhanced, especially when organic hydroperoxide was the oxidant. More importantly, the stability of the encapsulated molybdenum species in the catalysts is excellent.

Aluminum-free hierarchical Ti-beta was hydrothermally synthesized from a basic precursor using tetraethyl ammonium hydroxide and sodium fluorine as the structure directing agent and mineralization agent, respectively. The physicochemical properties are analyzed by XRD, TEM, UV-Vis, Si-29 NMR et al. The catalytic activity was evaluated via the epoxidation of cyclohexene and 1-oectene. The Ti-beta achieved are plate-like nano-crystals with crystal size of about 100 x 300 x 300 nm. More importantly, intracrystalline mesopores in the 10-40 nm range were simultaneously created, and most of the titanium could be isomorphously substituted into the zeolite matrix. The Ti-beta is defects-free, the thermal stability is excellent. Due to the improved accessibility of the active sites inside the crystals, the activity increased by more than 30% compared with the conventional Ti-beta formed from the HF-procedure.

Silanization is an effective approach for the hydrothermal synthesis of hierarchical zeolite. However, the secondary porosity created is subject to the organosilane size. Herein, inert silanes and surfactant were introduced to intensify the interactions between the hydrophobic group of an active organosilane, and hierarchical TS-1 (HTS) with more supermicropores (1-2 nm) and mesopores (2-4 nm) were prepared. More importantly, the modified silanization process is beneficial for titanium incorporation. Consequently, although there is more silicon on the surface of the HTS materials, the accessibility of the active sites located in the inner part of the crystals was improved. In the cyclohexene oxidation and 1-octene epoxidation reactions, enhanced catalytic activity of the HTS catalysts could be achieved, and the increase in the activity was more than 24% when tert-butyl hydroperoxide was the oxidant.

Zeolite beta is an important material in catalysis, however the material with molar ration of silicon and aluminum more than 200 is difficult to synthesize. Typically, the pure silica beta and heteroatom zeolite beta are prepared at near neutral pH using HF as the mineralization agent. However, the HF is highly toxic and corrosive, and the zeolites formed are usually more than 10 mu m. In this paper, alkaline and fluorine-containing salts was applied, and pure silica beta was hydrothermally synthesized from a basic precursor. The silica resource and alkali metal cations in the precursor would influence the crystallization process, tetraethyl orthosilicate and sodium cations are preferred. The pure silica beta is plate-like, the crystals formed on the third day are about 50 x 300 x 300 nm, which keep growing with the time, and pure silica zeolite beta with uniform size of about 200 x 700 x 700 nm are synthesized in a week. More importantly, the pure silica beta is defects-free, and it's highly hydrophobic.

Hierarchical Fe-MFI were synthesized by post-treatment with TPAOH and applied as catalysts in liquid phase dehydration of 1-phenylethanol. The catalysts were characterized by XRD, TEM and N2 physisorption et al. After treatment, more ferric ions occupied zeolite framework sites, leading to increase in Brønsted acid sites content. Moreover, secondary pores with pore size range in 8–100 nm were introduced into inside zeolite. The secondary pores improved the accessibility of active centers and diffusion properties of reactants. The conversion of 1-phenylethanol reached 90% with 99% styrene selectivity in 1.5 h at 80 °C, while the reaction time of hierarchical Fe-MFI is only a half of microporous Fe-MFI zeolite. Moreover, the hierarchical Fe-MFI could be reused for at least five times.

Chlorine based olefin chlorohydrination reaction is one of the most hazard and polluted processes for manufacturing epoxy compounds. To solve these drawbacks, we have exploited a totally novel allyl chloride chlorohydrination route, using HCl and H2O2 as raw materials, catalyzed by hollow titanium silicate (HTS) zeolite. Under optimal parameters, almost 100% allyl chloride conversion and over 98.0% dichloropropanol (DCP) selectivity have been achieved, and HTS zeolite displays pretty high stability in strong acidic solution for over 25 days. UV-Raman spectroscopy directly reveals the formation of Cl-2 and its derivates, but this chlorohydrination is also competitively dominated by an epoxidation-ring opening mechanism, especially in high catalyst dosage. That is because allyl chloride is much easier to be epoxidized to epichlorohydrin (ECH) under HTS catalyst, rather than reacts with Cl-containing species generated via the HCl oxidation with H2O2. Meanwhile, ECH is highly active to react with HCl to form 1,3-DCP catalyzed by H+ ions, thus the epoxidation process can be significantly promoted by ring-opening reaction, due to the pushing of chemical balance. Importantly, this study provides a novel viewpoint on developing green chemical processes, on the basis of their fundamental reaction mechanisms. (C) 2017 Elsevier B.V. All rights reserved.

Since it was claimed by EniChem in 1983 for the first time, titanium silicate‐1 (TS‐1) zeolite presented the most delightful catalytic performance in the area of selective organic oxidation reactions. To enhance the mass diffusion property, hierarchical titanium silicate with hollow cavities within crystal was prepared by using a post‐synthesis treatment in the presence of organic template, and then, it was commercially produced and employed in many industrial catalytic oxidation processes, such as propylene epoxidation, phenol hydroxylation, and cyclohexanone ammoximation. Moreover, we also developed several totally novel oxidation reactions on hollow titanium silicate (HTS) zeolite, i.e., Baeyer‐Villiger oxidation of cyclohexanone and chlorohydrination of allyl chloride with HCl and H2O2. In all cases, HTS shows much better catalytic performance than TS‐1, attributing to the mass diffusion intensification by introducing hollow cavities. On the other hand, enormous works on synthesizing hierarchical TS‐1 zeolites with open intracrystalline mesopores have been done via silanization treatment and recrystallization. Based on them, several bulk molecule oxidation processes with tert‐butyl hydroperoxide, such as epoxidation of fatty acid methyl ester (FAME) and large olefins, have been carried out. As a consequence, hierarchical TS‐1 zeolites supply a platform for developing environmental‐friendly catalytic oxidation processes to remarkably overcome the drawbacks of traditional routes.

Industrial production of dichloropropanols through chlorohydrination of allyl chloride suffers from a series of disadvantages such as use of hazardous Cl-2, low atom economy, low dichloropropanol concentration and serious pollution. In this work, a safer and greener route for chlorohydrination of allyl chloride with H2O2 and HCI over hollow titanium silicate (HTS) at mild condition is developed. Unlike the traditional Cl-2-based chlorohydrination, this novel method is initiated via synergistic effect of Lewis acidity (HTS) and Bronsted acidity (HCl) to promote occurrence of oxidation, protonation and nucleophilic reaction of allyl chloride simultaneously and hence dichloropropanols are generated. Owing to a completely different reaction route, the formation of 1,2,3-trichloropropane by-product is depressed and the content of dichloropropanol exceeded 22 wt%, which increase by about 4 times compared with traditional Cl-2-based chlorohydrination (the content of dichloropropanol is below 4 wt%). At the optimized conditions, both of the allyl chloride conversion and dichloropropanol selectivity could approach 99% simultaneously and the waste is minimized. What's more, the HTS was reusable. Concentrated HCl solution treatment was adopted to test HTS's stability. The characterization and catalytic evaluation results reveal that, although parts of the framework Ti species have transformed into non-framework Ti and then leached into the solution, HTS remains structural stable, and the allyl chloride conversion and dichloropropanol selectivity didn't decrease obviously during the treatment.

Epoxidation of fatty acid methyl ester (FAME) is commercially adopting peracids process, which possesses low selectivity and serious pollution problems. Herein, spongy titanosilicate zeolite with high catalytic performance in epoxidation of fatty acid methyl ester (FAME) has been demonstrated. The zeolite is constructed by combining pore-extending and post-treatment processes, which features mesopores with a diameter of 3–5.5nm. Thus, in the epoxidation of FAME with tert-butyl hydroperoxide under 90°C, the spongy TS-1 zeolite exhibits >99% conversion within 3h, far higher than that of TS-1 (39%), with a high selectivity (>90%) of epoxy product as well.

TS-1 was post-modified by ammonium salts or tetrapropylammonium hydroxide (TPAOH). During the ammonium salts modification, the crystals were eroded and extra-framework titanium species were formed. After the combined-modification, hierarchical TS-1 with secondary pore volume in the 0.22–0.28cm3/g range was obtained via the intensified dissolution-recrystallization process, although more extra-framework titanium species were generated as five-/six-coordinated species. In cyclohexene oxidation with tert-butyl hydroperoxide (TBHP) as the oxidant, the activity of modified TS-1 decreased when anatase was formed only. However, it increased in the presence of five-/six-coordinated titanium. The secondary porosity further improved the catalytic performance and the activity of the combined-modified TS-1 samples increased remarkably by >100%.

Hierarchical TS-1 with intracrystalline voids could be synthesized by post-modification with tetrapropyl ammonium hydroxide (TPAOH), however the process was supposed to be restrained by the charge balance effect.

A novel chlorohydrination process of allyl chloride with HCl and H2O2 catalyzed by hollow titanium silicate zeolite has been developed, overcoming the significant drawbacks of traditional Cl2-based route.