Zhenlu Wang

Prins condensation for the synthesis of isoprene from isobutylene and formaldehyde over sillica-supported H3SiW12O40 catalysts

The Prins condensation of isobutylene with formaldehyde over scillica-supported silicotungstic acid catalysts has been investigated. The catalysts were characterized via XRD, FTIR, Py-IR, NH3-TPD and TG–DSC techniques. It was found that the catalyst with 5xa0wt% silicotungstic acids loading exhibited the best isobutene conversion and isoprene selectivity, and excessive silicotungstic acid was not conducive to improve the catalytic performance. It was proposed that the concentration and strength of acid sites could affect the catalytic properties. An appropriate amount of weak Lewis acid sites were the active site for the condensation of isobutene with formaldehyde, and the medium-strong acid sites could cause the side reactions and coke deposits.

Selective hydrogenation of maleic anhydride over Pd/Al2O3 catalysts prepared via colloid deposition

AbstractPd/Al2O3 catalysts were prepared via colloid deposition and the performance of the catalysts was examined in the selective hydrogenation of maleic anhydride to succinic anhydride. When the reaction was carried on in a batch system with 1,4-dioxane as the solvent (353xa0K and 1.0xa0MPa), high conversion of maleic anhydride (>98%) and high selectivity (>99%) for succinic anhydride were observed after 5xa0h. The as-prepared Pd/Al2O3 catalyst also showed excellent performance in solvent-free system and fixed-bed systems. The maleic anhydride (MA) conversion was greater than 98%, and high selectivity (>99%) for succinic anhydride was obtained after 1600xa0h in a fixed bed reacter. The results showed that the activity of the Pd/Al2O3 catalysts was excellent due to its high active surface area.n Graphical AbstractPd/Al2O3 catalysts were prepared via colloid deposition and the performance of the catalysts was examined in the selective hydrogenation of maleic anhydride (MA) to succinic anhydride (SA). The MA conversion was >98%, and selectivity for SA was >99%.

The direct transformation of ethanol to ethyl acetate over Cu/SiO 2 catalysts that contain copper phyllosilicate

AbstractCu/SiO2 catalysts that contain copper phyllosilicate, were successfully prepared using the ammonia-evaporation method. The catalysts were characterized via XRD, ICP, BET, FTIR, TPR, XPS, NH3-TPD and FTIR of Pyridine Adsorption techniques. The results demonstrated that the formation of the copper phyllosilicate species significantly affected the structural properties and caused the CuO nanoparticles to become highly dispersed, and the copper phyllosilicate would provide access to the Lewis acidic Cu+ species. It was found that the catalyst with a 23.7 wt% copper loading exhibited the best ethanol conversion and ethyl acetate selectivity. When compared to a catalyst with the same copper loading which was prepared with the impregnation method, the higher activity and selectivity of catalysts might be ascribed to the homogenous distribution of copper nanoparticles, which was the active site for the dehydrogenation, and the amount of Lewis acidic Cu+ sites active for esterification. The synergetic effect between the Cu0 and Lewis acidic sites was the key factor to achieve direct transformation of ethanol to ethyl acetate.n Graphical AbstractCu/SiO2 catalysts, which contain copper phyllosilicate, were successfully prepared using the ammonia-evaporation method. Copper phyllosilicate species caused the CuO nanoparticles to become highly dispersed, and they would provide access to the Lewis acidic Cu+ species. Synergetic effect between Cu0 and Lewis acidic sites was the key factor for the reaction.

Synthesis of Methyl Acrylate by Aldol Condensation of Methyl Acetate with Formaldehyde Over Al 2 O 3 -Supported Barium Catalyst

AbstractVapor phase aldol condensation of methyl acetate with formaldehyde was first studied over Al2O3 with different calcination temperatures and Al2O3-supported barium with different amounts of barium catalysts. The catalysts were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, N2 adsorption–desorption, the pyridine absorption performed via Fourier transform infrared spectroscope, NH3 and CO2 temperature-programmed desorption. The results indicated that the calcination temperature affected the strength and the number of surface acid and base sites over the alumina catalysts. In addition, the moderate Lewis acid and weak base sites were critical to promote this aldol condensation reaction. Adding barium species, which could effectively modified the acid–base properties of Al2O3, clearly improved the catalytic activity and selectivity. The stability and regeneration of the optimum catalyst were also investigated and did not exhibit an obvious decrease in efficiency.Graphical AbstractAl2O3-supported barium catalyst was found to be an effective catalyst for vapor phase aldol condensation of methyl acetate with formaldehyde as a result of the appropriate intensity of acid and base.n

Vapor phase aldol condensation of methyl acetate with formaldehyde over a Ba–La/Al2O3 catalyst: the stabilizing role of La and effect of acid–base properties

Vapor phase aldol condensation of methyl acetate with formaldehyde was studied over Ba–La/Al2O3 with different amounts of lanthanum catalysts. The catalysts were characterized by X-ray diffraction (XRD), N2 adsorption–desorption, pyridine absorption performed via Fourier transform infrared spectroscope (Py-IR), NH3 and CO2 temperature-programmed desorption (NH3 and CO2-TPD), thermal analysis (TG-DTA) and scanning electron microscopy (SEM). The catalytic performance was evaluated using a fixed-bed microreactor. The results showed that bare Al2O3 was intrinsically active but poorly selective to methyl acrylate. The addition of barium species significantly improved the catalytic activity and selectivity. However, the Ba/Al2O3 catalyst was not stable in the continuous reaction due to a large amount of carbon deposition on the catalyst surface. Compared with adding individual components (BaO), the combination of the two promoters (BaO and La2O3) showed higher catalytic stability. Although the activity of the Ba–La/Al2O3 catalyst was not obviously increased compared with the Ba/Al2O3 catalyst, the carbon deposition was obviously suppressed in the target reaction due to the alkaline function of La2O3. Combined with the characterization results, we found that the addition of lanthanum species could significantly reduce the number of strong acid sites on the catalyst surface, inhibit the generation of carbon species in the reaction process, and stabilize the catalytic activity of the catalyst. In addition, the lifetime of the optimum 5Ba–0.5La/Al2O3 catalyst was evaluated over a continuous period of 300 h, and the initial catalytical activity did not exhibit an obvious decrease.

Synthesis and characterization of Ce-SBA-15 supported cesium catalysts and their catalytic performance for synthesizing methyl acrylate

A series of Ce-SBA-15 mesoporous materials were synthesized through a direct hydrothermal method and further impregnated with different amounts of Cs. The catalysts were characterized by XRD, XPS, SEM, NH3-TPD, CO2-TPD, FT-IR and N2 adsorption–desorption isotherm analyses. The XRD and N2 adsorption–desorption isotherm results showed that the Ce successfully incorporated into the framework of SBA-15, which was favorable for the generation of mesoporous materials with high specific surface areas, large pore volumes and narrow pore size distribution. The incorporation of Ce changed the acid–base properties of the support and promoted the dispersion of Cs species. NH3–CO2 TPD results indicated that a number of medium-strong acid and base sites existed in the 10Cs/Ce-SBA-15(10) catalyst, which made it suitable as a catalyst for the aldol condensation of methyl acetate with formaldehyde to prepare methyl acrylate.

Effect of Phosphoric Acid on HZSM-5 Catalysts for Prins Condensation to Isoprene from Isobutylene and Formaldehyde

A series of HZSM-5 zeolites modified with different amounts of phosphoric acid(P/HZSM-5) was pre-pared. The physicochemical features of the P/HZSM-5 catalysts were characterized via X-ray diffraction(XRD), N2 adsorption-desorption, NH3-temperature programmed desorption(NH3-TPD) and Fourier tranform infrared(FTIR) spectra of the adsorbed pyridine, and the performances of the catalysts for Prins condensation to isoprene from iso-butylene and formaldehyde were investigated. The maximum isobutene conversion and isoprene selectivity were 10.3% and 94.6% on the HZSM-5 catalyst with a Si/Al molar ratio of 600 using 5%(mass fraction) phosphoric acid. The phosphoric acid modification not only modulated the amount of acidic sites but also regulated the acid type. An appropriate amount of weak Lewis and Brönsted acid sites served as the active sites for the condensation of isobutene with formaldehyde, and the strong acid sites could cause side reactions and coke deposition.

Highly Catalytic Activity of Ba/γ-Ti–Al2O3 Catalyst for Aldol Condensation of Methyl Acetate with Formaldehyde

AbstractIn this work, titanium-doped mesoporous Al2O3 (γ-Ti–Al2O3) was prepared by an evaporation-induced self-assembly method and used as a carrier of Ba/γ-Ti–Al2O3 catalyst to catalyze the aldol condensation of methyl acetate with formaldehyde to methyl acrylate in a fixed-bed reactor. The catalysts were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, N2 adsorption–desorption, pyridine absorption performed via Fourier transform infrared spectroscope (Py-IR), and NH3 and CO2 temperature-programmed desorption (NH3 and CO2-TPD). Experimental results indicated that the doping of the titanium species into the frame work of mesoporous Al2O3 (γ-Ti–Al2O3) had a significant influence on the catalytic activity via modifying the acid–base surface properties of the catalyst. Furthermore, the Ba/γ-Ti–Al2O3 catalyst demonstrated excellent catalytic performance, with a methyl acetate conversion rate of 50% and methyl acrylate selectivity up to 90.2%. Compared with the Ba/Al2O3 catalyst, the Ba/γ-Ti–Al2O3 catalyst had better catalytic activity, stability and potential for practical application, which was likely due to an increased number of Lewis acid sites, especially the medium acid sites.Graphical AbstractBarium supported mesoporous γ-Ti–Al2O3 catalyst was found to be an effective catalyst for vapor phase aldol condensation of methyl acetate with formaldehyde.n

Catalytic amination of diethylene glycol with tertiarybutylamine over Ni–Al2O3 catalysts with different Ni/Al ratios

The catalytic amination of diethylene glycol (DEG) with tertiarybutylamine (TBA) to tertiarybutylaminoethoxyethanol (TBEE) was investigated on Ni–Al2O3 heterogeneous catalysts that were prepared using the co-precipitation method. The catalytic performances of these Ni–Al2O3 catalysts were considerably influenced by the Ni/Al ratios as well as the calcination temperature and reduction temperature of the catalysts. The catalyst with a Ni/Al ratio of 1u2006:u20061 that was calcined at 450 °C (NiAl-1.0-450), and reduced at 550 °C, exhibited a high activity and selectivity to TBEE. Based on the characterization, the activities were due to the action of the NiAl2O4 spinel in combination with NiO, which improved the stability of Ni(0), and the presence of both acidic and basic sites in the catalysts was also indispensable for this catalytic system.