Modified zirconia solid acid catalysts for organic synthesis and transformations

Modifying α-Al2O3 with cerium, zirconium, and sulfate for catalytic removal of C4F8

Modification of α-Al₂O₃ (A) with cerium (C), zirconium (Z), and sulfate (S) for effective C₄F₈ removal is evaluated at temperatures ≤ 650 °C. Catalytic hydrolysis of C₄F₈ is conducted to compare the performance of catalysts prepared (namely, A, AC, AZ, AS, ACS, and AZS). The interplay between rare earth element, acid amount, and surface area is further investigated. An investigation was carried out by characterization of catalysts by using XRD, BET, and NH₃-TPD. XRD pattern of the modified α-Al₂O₃ catalyst shows that the average grain size is 37 nm. BET analysis indicates that the surface area increases with the addition of Ce and Zr, while NH₃-TPD analysis shows the improvement of acid sites after the addition of Ce, Zr, and SO₄^2-. The experimental results indicate that C₄F₈ conversion over A catalyst reaches 14.81% at 550 °C with the addition of 38% H₂O_(g). Under the same operating condition, C₄F₈ conversion efficiencies achieved with AC and AZ catalysts increase to 42.03% and 50.1%, respectively. Furthermore, the efficiencies over AS, ACS, and AZS catalysts increase to 49.85%, 86.94%, and 87.18%, respectively. Stability tests show that the performances of the catalysts for C₄F₈ conversion are with the order of AZS > ACS > AZ > AC > AS > A at 650 °C during 24 h. The activation energy of the AZS catalyst in catalytic hydrolysis of C₄F₈ is 60.49 kJ/mol. The products of C₄F₈ conversion mainly include CO₂, CO, and COF₂ and small amounts of CHF₃ and C₂F₄. This study has confirmed that the AZS catalyst shows the best activity, acidity, and stability on C₄F₈ removal.

Gas phase sulfation of ceria-zirconia solid solutions for generating highly efficient and SO2 resistant NH3-SCR catalysts for NO removal

A series of ceria-zirconia solid solutions (Ce_xZr_1-xO₂) were prepared by co-precipitation method and then sulfated with SO₂ + O₂ at 200 °C. Subsequent testing with the selective catalytic reduction of NO by NH₃ (NH₃-SCR) showed that the activity of the sulfated Ce_xZr_1-xO₂ catalysts oxide catalysts exhibited a volcano-type tendency with increasing Zr content. Furthermore, the sulfated Ce_0.6Zr_0.4O₂ catalyst showed the most desirable NH₃-SCR activity at 250-300 °C, and exhibited much better SO₂ resistance at 250 °C. Detailed characterization results demonstrated that Ce_0.6Zr_0.4O₂ could adsorb more surface sulfate species and then produce more stable acid sites than pure CeO₂ at 200 °C. After sulfation treatment, more Ce³⁺ and oxygen vacancies were formed on the surface of Ce_0.6Zr_0.4O₂. In situ diffuse reflectance infrared Fourier transform spectroscopy (in situ DRIFTS) experiments suggested that the nitrates species deposited on the surface of as-prepared Ce_0.6Zr_0.4O₂, which showed no reactivity, could barely deposit on the same sample after sulfation. While, the sulfated Ce_0.6Zr_0.4O₂ had more reactive acid sites to participate in the NH₃-SCR and the reaction proceeded via Eley-Rideal mechanism. This work proved that sulfation treatment could be used in designing an efficient cerium-zirconium based NH₃-SCR catalyst with great application prospect.

Glacial Acetic Acid Catalyzed Synthesis, Physicochemical and Biological Evaluation of Benzodiazepines as Potent CNS Agents

BACKGROUND

Approach for green chemistry for chemical synthesis is found to be very efficient as it makes the reaction more easily, less tedious, maximize desired products and minimize by-products.

MATERIALS & METHODS

Utilizing this approach 1, 5-benzodiazepines and its derivatives have been synthesized and evaluated for skeletal muscle and antianxiety activity. 1, 5-benzodiazepine derivatives have attracted great attention due to its diversity of pharmacological activities and its application in heterocyclic synthesis and medicines. The target compounds were synthesized by first reacting o-phenylenediamine with acetophenone to yield 1, 5-benzodiazepines. In the next step the NH of 1, 5-benzodiazepines were chloroacetylated and then the chloro group was substituted with different anilines. The structures were confirmed on the basis of their TLC, IR, 1H NMR and CHN elemental studies. The physicochemical parameters were determined for BBB penetration through online software.

RESULTS

The Log P values of the compounds tested showed that compounds have the potential to be CNS active. The compounds were evaluated for the skeletal muscle relaxant activity and antianxiety activity. It was investigated that 1, 5-benzodiazepines derivatives possess significant differences between control group and treated group.

CONCLUSION

Among these derivatives, the compound bearing chloro group possesses the highest skeletal muscle relaxant and antianxiety activity.

Sulfated zirconia: an efficient catalyst for the Friedel–Crafts monoalkylation of resorcinol with methyl tertiary butyl ether to 4-tertiary butylresorcinol

Sulfated zirconia (SZ) is an efficient and recyclable catalyst in the selective monoalkylation of resorcinol with MTBE to 4-tertiary butyl resorcinol at low temperature (60 °C).

Synthesis of 1,5-benzodiazepine and its derivatives by condensation reaction using H-MCM-22 as catalyst

A simple and versatile method for the synthesis of 1,5-benzodiazepines is via condensation of o-phenylenediamines (OPDA) and ketones in the presence of catalytic amount of H-MCM-22 using acetonitrile as solvent at room temperature. In all the cases, the reactions are highly selective and are completed within 1-3 h. The method is applicable to both cyclic and acyclic ketones without significant differences. The reaction proceeds efficiently under ambient conditions with good-to-excellent yields.

Desulfurization from thiophene by SO(4)(2-)/ZrO(2) catalytic oxidation at room temperature and atmospheric pressure

Thiophene, due to its poison, together with its combustion products which causes air pollution and highly toxic characteristic itself, attracted more and more attention to remove from gasoline and some high concentration systems. As the purpose of achieving the novel method of de-thiophene assisted by SO(4)(2-)/ZrO(2) (SZ), three reactions about thiophene in different atmosphere at room temperature and atmospheric pressure were investigated. SO(4)(2-)/ZrO(2) catalyst were synthesized and characterized by X-ray photoelectron spectroscopy (XPS), Fourier transformation infrared spectroscopy (FT-IR), X-ray diffraction (XRD) and scanning electron microscope (SEM). The products were detected by gas chromatography-mass spectrometry (GC-MS). XP spectra show that ozone-catalyst system (SZO) have two forms of sulfur element (S(6+) and S(2-)) on the catalyst surface, which distinguished from that of air-catalyst system (SZA) and blank-catalyst system (SZB) (S(6+)). And the results of GC-MS exhibited that some new compounds has been produced under this extremely mild condition. Especially, many kinds of sulfur compounds containing oxygen, that is easier to be extracted by oxidative desulfurization (ODS), have been detected in the SZA-1.5h and SZB-3h system. In addition, some long chain hydrocarbons have also been detected. While in SZO-0.5h system, only long chain hydrocarbons were found. The results show that total efficiency of desulfurization from thiophene with ozone near to 100% can be obtained with the SO(4)(2-)/ZrO(2) catalytic oxidation reaction.

Simple and effective synthesis of methoxy-dimethylbenzene from electrochemical oxidation of p-xylene in methanol solvent catalyzed by SO(4)(2-)/ZrO(2)-M(x)O(y)

A series of composite solid superacid catalysts SO(4)(2-)/ZrO(2)-M(x)O(y) (M=Ti, Ni, Si) were prepared and investigated by means of Fourier transform infrared (FT-IR) and X-ray photoelectron spectroscopy (XPS). All catalysts exhibit good catalytic activity in the electrochemical reaction of p-xylene with methanol assisted with a pair of porous graphite plane electrodes and the selectivity of main products higher than 90% were observed. In particular, SO(4)(2-)/ZrO(2)-SiO(2) catalyst exhibited excellent catalytic activity. According to the experimental results, a possible free radical reaction mechanism confirmed by XPS and ultraviolet-visible (UV-vis) spectra was proposed. It may be concluded that a simple and feasible electrochemical catalytic oxidation reaction at room temperature and standard atmosphere may be possible.

Preparation of mesoporous titania solid superacid and its catalytic property

Mesoporous titania (TiO(2)) was synthesized by hydrothermal method using cetyltrimethyl ammonium bromide (CTAB) as a template and using anhydrous ethanol and tetra-n-butyl titanate (TBOT) as raw materials. Mesoporous titania solid superacid and nanosized titania solid superacid catalysts were prepared by wet impregnation method. The structure and property of as-prepared samples were characterized by means of XRD, FT-IR and N(2) physical adsorption. The esterification of salicylic acid with isoamyl alcohol and the condensation of cyclohexanone with ethylene were used as model reactions to test the catalytic activities of the catalysts. On the other hand, the comparison of catalytic activities of the prepared solid superacid catalysts and the conventional liquid acid H(2)SO(4) was also carried out under the same experimental conditions. The results show that the catalytic activities of the prepared solid superacid catalysts were higher than that of the conventional liquid acid H(2)SO(4), and that the catalytic activity of mesoporous TiO(2) solid superacid is the highest among the three catalysts. Mesoporous TiO(2) solid superacid is a good catalyst for the synthesis of isoamyl salicylate or cyclohexanone ethylene ketal.

Environmentally friendly efficient one-pot esterification of cyclohexane with CuO-promoted sulfated zirconia

The production of dibutyl phthalate directly from oxidation and esterification of cyclohexane, catalyzed by CuO-modified sulfated zirconia (SZCu) by one-pot under mild condition, was studied. The esterification reaction process was monitored by UV-vis spectra and the distribution of the products was analyzed by gas chromatograph-mass spectrometry (GC-MS). The result revealed that the SZCu catalyst was efficient in the direct oxidation and esterification of cyclohexane to ester. The selectivity for ester (dibutyl phthalate) can reach up to 72.2 wt.%, and the yield of ester was 29.5 wt.%. The esterification reaction, that offers several advantages such as usage of environmental friendly oxidant, simple work-up procedure, no-solvent conditions, short reaction times, easy recovery and reusability of the catalyst, is necessary for chemosynthesis industry from the environment standpoint. The regeneration property of SZCu was also tested in this work.

Cobalt modified solid superacid assisted electrochemical reaction of toluene with methanol

The electrochemical catalytic reaction of toluene with methanol, assisted with a pair of porous graphite plate electrodes, catalyzed by solid superacid of cobalt modification catalyst with chemical conversion higher than 81%, was described and investigated by UV-vis spectrum, scan electron microscopy (SEM), powder X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and gas chromatography-mass spectrometry (GC-MS). A possible free radical reaction mechanism was proposed. It may be concluded that a simply and feasible electrochemical catalytic coupling oxidation reaction at room temperature and air pressure may be possible.