Congxin Wang

One‐Step Hydrotreatment of Vegetable Oil to Produce High Quality Diesel‐Range Alkanes

A one-step hydrotreatment of vegetable oil combining deoxygenation and isomerization to directly produce low cloud point, high quality diesel is devised. The Pt/zeolite bifunctional catalysts prepared by using SAPO-11 and ZSM-22 zeolites as supports are used in this process. Catalytic reactions are conducted in a fixed-bed reactor under a hydrogen atmosphere. Over the bifunctional catalyst, 100 % conversion of soybean oil is obtained at 357 °C, 4 MPa, and 1 h(-1), and 80 % organic liquid yield is achieved, which is close to the maximum theoretical liquid yield. In the organic products, the alkanes selectivity is 100 % with an i-alkanes selectivity above 63 %. NH(3)-temperature programmed desorption (TPD), pyridine IR spectroscopy, and other characterization techniques are used to study the effect of the support acidity on the reaction pathway. Over the Pt/zeolite bifunctional catalyst with less strong Lewis acid sites, the reaction proceeds via the decarboxylation plus decarbonylation pathway. This one-step method provides a new strategy to produce low cloud point, high quality diesel from biomass feedstock in a more economic and attractive way.

Basicities and transesterification activities of Zn–Al hydrotalcites-derived solid bases

Solid bases were prepared by calcining as-prepared Zn–Al hydrotalcites at different temperatures. The evolutions of their structure and basicity were characterised using X-ray diffraction, thermogravimetric analysis, infrared spectroscopy of CO2 adsorption and temperature programmed desorption of methanol. With an increase in the calcination temperature, the as-prepared Zn–Al hydrotalcites were firstly converted into dehydrated Zn–Al hydrotalcites and next converted into Zn–Al oxides. The basic sites of these solid bases changed from OH groups to Mn+–O2− (M = Zn or Al) pairs and isolated O2− ions. These solid bases were evaluated in transesterification reactions used for biodiesel production. The dehydrated Zn–Al hydrotalcites obtained at 473 K exhibit the highest activity, with a biodiesel yield of approximately 76% at 413 K, 1.7 MPa and 1.0 h−1. This catalyst exhibits no deactivation after about 150 h. The structure–reactivity relationship of the catalyst is also discussed.

Hydrothermal Carbon Enriched with Oxygenated Groups from Biomass Glucose as an Efficient Carbocatalyst

Metal-free carbocatalysts enriched with specific oxygenated groups with different morphology and size were synthesized from glucose by hydrothermal carbonization, in which cheap and widely available biomass could be converted into functionalized carbon using an environmentally benign process. The hydroxy- and carbonyl-enriched hydrothermal carbon (HTC) could be used in nitrobenzene reduction, and higher conversion was obtained on the sphere morphology with smaller size. In the Beckmann rearrangement of cyclohexanone oxime, carboxyl-enriched HTC exhibited superior performance compared with conventional solid acid (such as HY and HZSM-5), on which the strong acid sites and weak Lewis acid sites lead to high selectivity for the side product. Although the intrinsic acidity of carbon is weak, the carboxyl-enriched carbon was used in weak Brønsted acid-catalyzed reactions, such as the Beckmann rearrangement.

Synthesis of zeolite Beta containing ultra-small CoO particles for ethylbenzene oxidation

ABSTRACT Zeolite Beta containing ultra-small CoO particles was synthesized from a one-step hydrothermal process. The synthesis route involves the pre-mixture of hydrofluoric acid with tetraethylammonium hydroxide (in a molar ratio of 1.3–1.5:1) before the addition of a silicon and cobalt source. Investigations by scanning electron microscopy, X-ray diffraction, UV-Vis spectroscopy, X-ray photoelectron spectroscopy, H 2 -temperature-programmed reduction and transmission electron microscopy confirm the presence of ultra-small CoO particles in the zeolite Beta structure. The ultra-small CoO particles in zeolite Beta present high stability against both oxidation and reduction atmospheres at high temperatures. The catalytic performance of the CoO-containing zeolite Beta catalysts was compared with other Co-containing zeolites by evaluating ethylbenzene oxidation reactivity. The CoO-containing zeolite Beta exhibits high ethylbenzene conversion and high selectivity to acetophenone and 1-phenylethanol. The high activity of this catalyst system can be attributed to the high dispersion of the ultra-small CoO particles in the Beta structure.