Effects of Mo-Sn interactions on the performance of Mo1Sn2 catalysts for low-temperature oxidation of dimethyl ether

The performance of molybdenum tin catalyst was evaluated using a quartz tube fixed bed reactor with an inner diameter of 5mm and a length of 420 mm. The prepared catalysts were all crushed and sieved into 20-40 mesh sizes, with a dosage of 1ml. In order to maintain a constant temperature of the catalyst bed and prevent catalyst sintering, 1ml ceramic rings were used for dilution. Before the reaction, the catalyst is pre treated with oxygen at 300 ° C for 2 hours, then lowered to a reaction temperature of 110 ° C and introduced into the DME reaction. The feed ratio of dimethyl ether to oxygen is 1:1 (mass ratio), the airspeed is 1800h-1, and the exhaust gas flow rate is detected. The reaction products were analyzed on GC-2014CPF/SPL and GC-2014 chromatography using FID and TCD detectors, respectively. The two chromatography data were corrected and correlated with DME to obtain the amount of substance in the products. The catalyst was characterized by TEM using JEM-2001 transmission electron microscopy at a working voltage of 200kV. The texture properties of the catalyst were determined using the JW-BK100B physical adsorption instrument. The sample was subjected to degassing pretreatment at 250 ° C and vacuum conditions, and low-temperature N2 adsorption and desorption experiments were conducted using pure liquid nitrogen as the adsorption medium (-196 ° C). The catalyst was subjected to X-ray diffraction (XRD) testing using the MiniFlex600 X-ray diffractometer from Rigaku, Japan. Cu K α Radiation irradiation with a scanning angle of 5o-90o and a continuous scanning rate of 5o/min. The programmed temperature desorption (NH3-TPD) test was conducted on the TP5080 chemical adsorption instrument. Weigh 50mg of catalyst and place it in a sample tube. Heat it up to 400 ° C in an inert atmosphere with a gas flow rate of 30 mL/min, then cool it down to 50 ° C. Introduce NH3 (30 mL/min) for adsorption for 10 minutes, then blow it out. Finally, heat it up to 600 ° C for desorption and record the signal. The programmed temperature reduction (H2-TPR) test was conducted on the TP5080 chemical adsorption instrument. Weigh 50mg of catalyst and place it in a sample tube. Program the temperature to 200 ° C and then cool it down to 50 ° C. Then, the mixed gas is introduced and the temperature is programmed to 900 ° C to reduce the catalyst, and the signal is recorded. Raman testing was conducted on a Horiba evolution Raman spectrometer with an excitation wavelength of 532 nm and a scanning range of 100-1100 cm-1. Fourier transform infrared spectroscopy (FT-IR) is performed on BrukerTensor27, using KBr to scan the background. Place the catalyst into the sample cell with Ar as the carrier gas, raise the temperature to 110 ° C, maintain the constant temperature for 1 hour, and then perform testing. The catalyst was characterized by ESR using Bruker EMX plus-10/12 instrument. The sample was thoroughly ground and 10 mg of powder was loaded into a nuclear magnetic tube for detection at -173 ° C.