Mechanism of Microwave Activation on Molybdenite

The effect of microwave activation on the properties of oxidation roasting for molybdenite was investigated under the protection of inert gas, and the specific surface area, the oxidation properties, lattice constant, microstructure, and shape of molybdenite were analyzed and characterized by a laser particle size analyzer, thermogravimetry (TG), X-ray diffractometry (XRD) and scanning electron microscopy (SEM). The results show that microwave activation could effectively reduce the residual amount of sulfur in the molybdenum calcine and decrease the average particle size of molybdenite while increasing the specific surface area of molybdenite. On increasing the microwave activation power, the crystal cell volume and grain size of MoS2 reduced, and the microstrain increased slightly. At the same time, the surface shape of molybdenite became looser, but the layered structure is not changed. In addition, the oxidation property changed significantly; microwave activation promoted the oxidation reaction of molybdenite above 538 °C, and the rate of weight loss increased from 6.177% to 7.718% at 620 °C.

Adsorption of petroleum products by modified and activated adsorbents

This research is aimed at investigating the adsorption of petroleum products from aqueous solutions by adsorbents modified with HCl and those activated by microwave radiation. The research objects were carbon adsorbents: activated coals, such as AD-05-2, IPI-T, KAD-iodine and zeolites of the TransBaikal deposit. The quantitative analysis of waters (standardised test solutions with an initial concentration of petroleum products not exceeding 10 mg/l) was carried out by the fluorimetric method using a Fluorat-02 liquid analyser. The adsorbents were activated in a microwave oven at a wave power of 800 W for 1 min. The modification was carried out according to the following procedure: 10 g of the adsorbents dried to a constant weight at a temperature of 120-150 °C were stirred for 24 h with 200 ml of a 12% HCl solution in water.Next, the suspension was filtered and washed with distilled water until neutral. It was found that the value of adsorption of petroleum products by adsorbents modified with HCl increases by 3.8 times for activated carbon KAD-iodine, 0.5 times for IPI-T, and equals 0.71 mg/g and 0.80 mg/g respectively. Among the studied sorbents, these sorbents have the largest grain size (3-5 mm) and micropore volume (0.28-0.29 cm3/g). It was established that the method of short-term (within 1 min) microwave activation makes it possible to increase the adsorption of petroleum products by: 4.2 times for activated carbon KAD-iodine and 0.6 times for IPI-T in comparison with the original adsorbents. The highest adsorption value of petroleum products corresponds to zeolites and equals 0.99 mg/g. The action of microwave radiation is associated with the dissociation and evaporation of the water bound in the adsorbents and flammable organic substances, which leads to an increase in the porosity of the adsorbent. The application of the microwave activation method is highly promising in comparison with the classic methods of chemical and steam-gas activation. This method simplifies the technological design and reduces the consumption of reagents for the production of effective adsorbents used to extract petroleum products from aqueous solutions, which acquires particular importance in the context of maintaining the environmental safety of water use.

Microwave-Assisted Continuous Flow for the Selective Oligomerization of Glycerol

The continuous oligomerization of glycerol for the formation of polyglycerol was carried out for the first time under microwave activation. In the presence of potassium carbonate, we studied the ease of handling, effects of temperature, flow rate and residence time of an inexpensive homogeneous commercial catalyst. The main linear and branched-chain diglycerol and triglycerol regioisomers were characterized and the quantification of the different isomers was realized. Successive cyclic mode processes followed by short distance distillation allowed the mixture to be enriched with glycerol ethers and thus to obtain a mixture of diglycerol (50.2 wt%), triglycerol (22.1 wt%), tetraglycerol (9.5 wt%), and pentaglycerol (4.3 wt%).

The Piancatelli rearrangement of non-symmetrical furan-2,5-dicarbinols for the synthesis of highly functionalized cyclopentenones

Substituted and non-symmetrical furan-2,5-dicarbinols were readily prepared from hydroxymethylfurfural (HMF), a renewable raw material from biomass. The Piancatelli rearrangement of these furan-2,5-dicarbinols, catalyzed by DyCl3 and under microwave activation, affords...

Aging Properties and Mechanism of Microwave-Activated Crumb Rubber Modified Asphalt Binder

Although crumb rubber modified asphalt (CRMA) has a better performance than matrix asphalt (MA) in road engineering, the application bottlenecks of this material lies in its high viscosity, poor workability and bad storage stability. Microwave technology is one of the solutions to the above problems. The objective of this study was to investigate the physical and chemical changes before and after aging of CRMA which was prepared by microwave activated crumb rubber, and the aging mechanism of microwave-activated crumb rubber modified asphalt (MACRMA). Through penetration, softening point, ductility, viscosity and DSR test, the high and low temperature performance and temperature sensitivity of MA, CRMA and MACRMA before and after aging were studied. These tests results revealed that microwave treatment can improve the anti-rutting ability and the anti-aging performance of rubber asphalt. According to gel permeation chromatography (GPC) test, the distribution changes of the internal molecular content of the three asphalts were determined during the aging process. Its test results showed that aging effect accelerated the conversion of small molecules to large molecules in asphalt, and the value of large molecular size (LMS) increases more after long-term aging. The microwave activation made the swelling reaction more intense, thereby delayed the conversion of LMS in the rubber asphalt. In addition, LMS has a high correlation with test indicators. The fourier transform infrared spectroscopy (FTIR) test was used to measure the functional group changes of each asphalt. The FTIR spectra indicated that microwave activation is mainly a process of physical change. The carbonyl and sulfoxide functional group indices of MACRMA were lower than those of MA and CRMA, which also confirmed that MACRMA has a better anti-aging ability.