Guangxiang He

Synthesis and characterization of a K/K2CO3-based solid superbase as a catalyst in propylene dimerization

A novel solid superbase 3%K/K2CO3 was prepared by loading metallic potassium on K2CO3. The optimized preparation conditions included a loading time of 1.5 h, loading temperature of 150 °C, loading amount of 3wt% and average carrier size of 120 μm. Under the optimum conditions, the conversion of propylene is about 60% with the selectivity of dimers 98.5% and the selectivity of 4MP1 86.3%. In addition, the superbase 3%K/K2CO3 has a base strength of H−≥37, and the concentration of basic sites of H−≥35 is approximately 0.3mmol·gCAT−1. The microcrystal of metallic potassium was determined using X-ray diffraction (XRD) and differential scanning calorimetry (DSC). It was assumed that the oxygen species, which are adjacent to lattice defects, such as the crystalline corners, edges and vacancies of metallic potassium micro-crystals, constituted the superbasic sites.

Green synthesis of acetaldehyde oxime using ammonia oxidation in the TS-1/H2O2 system

A qualitative analysis for the ammoximation of acetaldehyde to its oxime using TS-1 as a catalyst and H2O2 as an oxidant was investigated. According to the hydroxylamine mechanism, the effects of temperature, H2O2/acetaldehyde, NH3/acetaldehyde, and the amount of TS-1 on the catalytic properties of TS-1 were studied in detail. The results showed that temperature determined the main and side reactions, and ammonia provided an alkaline environment. Under the optimized reaction conditions, acetaldehyde conversion and acetaldehyde oxime selectivity could reach up to 89.5 and 82.7%, respectively. The comprehensive results of FTIR, XRD, BET and XRF declared that TS-1 deactivation was caused by carbon deposition, not structural damage. The catalyst could be regenerated by calcination when the temperature exceeded a certain minimum value. Meanwhile, the reaction mechanism shows that the procedure of generating hydroxylamine was the control step of reaction, and the entire reaction goes on the route of hydroxylamine.

The catalytic characteristic and synthesis technique for 4-methyl-1-pentene over a potassium-supported superbase catalyst

Abstract The dimerization of propene to 4-methyl-1-pentene (4MP1) was studied in a fixed-bed reactor at 150 °C temperature, 8 MPa pressure, and 1 h−1 liquid hourly space velocity (LHSV) in the presence of solid superbase with 20 wt% one-pass conversion to hexene and 88% selectivity toward 4MP1. Based on the reaction results, propene competes with 4MP1 for adsorption on the catalyst surface. A higher reaction pressure or a lower liquid rate of 4MP1, controlled by a suitable propene LHSV or reaction temperature, was beneficial to the adsorption of propene, which reduced the isomerization of 4MP1. Under optimized conditions, propene dimerization was stable for 200 h, and isomerization was limited to less than 5%, yielding products with about 19% one-pass conversion to hexene by weight and 87% selectivity toward 4MP1.