No abstract

The work presents a study by temperature programmed desorption, in situ infra red spectroscopy and catalytic steam reforming of ethanol (SRE) over CeO 2 and the bimetallic Pd-Rh/CeO 2 ; comparison with the monometallic catalysts (Rh/CeO 2 and Pd/CeO 2 ) was also made for the steam reforming study. Comparing TPD of ethanol over CeO 2 and the bimetallic catalysts indicated two main differences: the direct oxidation route to acetate over CeO 2 is suppressed by the presence of the metal and the lowering of the dehydrogenation reaction temperature by about 100 K. In situ IR study indicated that the bimetallic catalyst breaks the carbon-carbon bond of ethanol at low temperature \400 K, as evidenced by the presence of adsorbed CO species. SRE over wt.% Rh-wt.% Pd/ CeO 2 , at 770 K at realistic conditions showed that maximum conversion and selectivity could be achieved. This high activity considering the very small amounts of transition metals on CeO 2 is discussed in light of their electronic and geometric effects.

In this study, ultrasound was used to accelerate two-stage (esterification–transesterification) catalytic synthesis of biodiesel from used cooking oil, which originally had a high acid value (4.35 mg KOH/g). In the first stage, acid-catalyzed esterification reaction conditions were developed with a 9:1 methanol/oil molar ratio, sulfuric acid dosage at 2 wt %, and a reaction temperature of 60 °C. Under ultrasound irradiation for 40 min, the acid value was effectively decreased from 4.35 to 1.67 mg KOH/g, which was decreased to a sufficient level (<2 mg KOH/g) to avoid the saponification problem for the subsequent transesterification reaction. In the following stage, base-catalyzed transesterification reactions were carried out with a 12:1 methanol/oil molar ratio, a sodium hydroxide dosage of 1 wt %, and a reaction temperature of 65 °C. Under ultrasound-assisted transesterification for 40 min, the conversion rate of biodiesel reached 97.05%, which met the requirement of EN 14214 standard, i.e., 96.5% minimum. In order to evaluate and explore the improvement of the ultrasound-assisted two-stage (esterification–transesterification) process in shortening the reaction time, additional two-stage biodiesel synthesis experiments using the traditional mechanical stirring method under the optimal conditions were further carried out in this study. It was found that, under the same optimal conditions, using the ultrasound-assisted two-stage process, the total reaction time was significantly reduced to only 80 min, which was much shorter than the total time required by the conventional method of 140 min. It is worth noting that compared with the traditional method without ultrasound, the intensification of the ultrasound-assisted two-stage process significantly shortened the total time from 140 min to 80 min, which is a reduction of 42.9%. It was concluded that the ultrasound-assisted two-stage (esterification–transesterification) catalytic process is an effective and time-saving method for synthesizing biodiesel from used cooking oil with a high acid value.

Without assistant working instrument, laparoscopy-assisted extracorporeal ligation of the hernia defect may be safely performed in most infants and children. The use of preperitoneal hydrodissection and extraperitoneal knot-tying could tautly enclose the hernia defect without peritoneal gaps and approach an accepted recurrence rate.