Chunlei Zhang

Side-chain alkylation of toluene with methanol over boron phosphate modified cesium ion-exchanged zeolite X catalysts

A series of boron phosphate (BPO4) modified ion-exchanged CsX zeolites, prepared by impregnation method, were characterized by a variety of means and utilized as catalysts for the side-chain alkylation of toluene with methanol. Both BPO4 and Cs species are highly dispersed on the surface/channel of the BPO4/CsX zeolites. The addition of a small amount of BPO4 has no obvious effect on the basic strength of catalysts, but decreases the number of basic sites slightly. Meanwhile, more weak Lewis acidic sites appear with the increasing BPO4 loading. Compared with CsX, the BPO4 modified CsX catalysts exhibit lower ability for the adsorption/activation of methanol to produce surface intermediates like formaldehyde, unidentate formate and bidentate formate. Catalytic reaction results showed that modification of CsX with boron phosphate can improve both the conversion of toluene and the selectivity of styrene. The inhibition role in producing the unfavorable bidentate formate might be a key factor for finally resulting in the improvement of the catalytic properties of BPO4/CsX catalysts for the side-chain alkylation of toluene with methanol.

Efficient and selective hydrogenation of benzonitrile to benzylamine: improvement on catalytic performance and stability in a trickle-bed reactor

An efficient and selective hydrogenation of benzonitrile to benzylamine has been accomplished over a Pd/γ-Al2O3 catalyst, without any additives, in a trickle-bed reactor. Some unique features involving both a gas–liquid phase reaction and a gas phase reaction were found for the hydrogenation of benzonitrile, due to the application of the trickle-bed reactor. A comparison of the catalytic performances clearly showed that there was more excellent mass transmission and more substantial back-mixing restriction in the trickle-bed reactor than in the batch reactor. As a result, Pd/γ-Al2O3 exhibited a higher activity and benzylamine selectivity for the hydrogenation of benzonitrile, generating benzylamine in a yield of ∼86%. Furthermore, a long-term stability test of up to 120 h was conducted on Pd/γ-Al2O3 for the hydrogenation of benzonitrile, with no significant loss of activity, exhibiting its potential in industrial application.

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.

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.

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.