We showed that alumina (Al(2)O(3)) overcoating of supported metal nanoparticles (NPs) effectively reduced deactivation by coking and sintering in high-temperature applications of heterogeneous catalysts. We overcoated palladium NPs with 45 layers of alumina through an atomic layer deposition (ALD) process that alternated exposures of the catalysts to trimethylaluminum and water at 200°C. When these catalysts were used for 1 hour in oxidative dehydrogenation of ethane to ethylene at 650°C, they were found by thermogravimetric analysis to contain less than 6% of the coke formed on the uncoated catalysts. Scanning transmission electron microscopy showed no visible morphology changes after reaction at 675°C for 28 hours. The yield of ethylene was improved on all ALD Al(2)O(3) overcoated Pd catalysts.

The solid superacid catalyst SO 4 2-/ZrO 2 was prepared by impregnation and characterized by infrared spectroscopy, thermogravimetric analysis, and X-ray diffraction. Their performances were evaluated by the transesterification reaction of waste cooking oil (WCO) with methanol. The influence of the load ratio of SO 4 2-/ZrO 2 , molar ratio of methanol/waste cooking oil, catalyst amount, reaction temperature, and reaction time on biodiesel yield was investigated. Under a condition of methanol/WCO molar ratio of 9:1, a catalyst amount of 3 wt %, reaction time of 4 h, and reaction temperature of 120°C, 93.6% of biodiesel yield was obtained.

A designer polymethylhydrosiloxane molecule, modified with nitrile and silanol groups, offers independent control of metal loading and particle size distribution when used to assist the preparation of metal nanoparticles.

A 500 h endurance test of continuous catalytic transesterification to biodiesel was conducted in a bench-scale fixed-bed reactor. A designed cylinder shape of KF/Ca−Mg−Al hydrotalcite catalyst was stable through the test with high catalytic activity and mechanical strength, converting palm oil to biodiesel with a conversion of more than 95%. Conditions effects on transesterification under relative high pressure (1.0 MPa) were investigated and a one-dimensional heterogeneous model of a fixed-bed reactor was developed to describe the reaction-mass transfer behaviors of continuous catalytic transesterification in a bench-scale fixed-bed reactor. With the given reactor size, optimum conditions were proposed as a LHSV (liquid hourly space velocity) of 0.76−0.25 h −1 , molar ratio of methanol-to-oil of 9.16−13.7, and temperature of 338−347 K.

No abstract