(6ce) Study on Fe-Mo/CAR Bifunctional Catalyst for One-Step Synthesis of Methylal Via Methanol Oxidation

Teaching Interests: Chemical engineering and technology

Due to the increasing lack of petroleum resources and non-renewable energies, methanol, the basic product of C-1 chemistry, as the most fundamental raw material in place of petrochemical engineering products, has become the new development direction of energy and chemical industry at present stage. One of the representatives of C-1 chemical industry is the comprehensive utilization of methanol. In recent years, methanol and its derivatives have aroused a research upsurge in academic and industrial circles. Through oxidation or dehydration, methanol can be converted into formaldehyde (FA), dimethyl ether (DME), dimethoxymethane (DMM) and methyl formate (MF). Among which, DMM is an excellent industrial solvent and chemical intermediate. It is used as gasoline additive, base material for organic synthesis and HCHO synthesis and the precursor of PODEn, the additive of diesel fuel. The traditional DMM process is to extract DMM by dehydration and condensation of methanol and formaldehyde under the action of acid catalyst, and FA is extracted by oxidation of methanol under the catalysis of silver or Fe-Mo catalyst. The traditional process is featured by disadvantages such as high energy consumption, complicated process, rigorous reaction condition and relatively big environmental pollution. Therefore, the one-step extraction of DMM by methanol is of great research significance in theory and practice.

In the past dozens of years, a great number of researchers have made research and exploration on the bifunctional catalyst for one-step extraction process of DMM. The result shows that, although it can acquire relatively high DMM selectivity, it is still unable to get high methanol conversion rate, and the DMM yield is relatively low, its maximum yield is only 61.38%. In the meanwhile, this type of catalyst has disadvantages such as high cost, poor industrial applicability, strong acidity that may corrode reaction equipment and low reaction yield.

In order to solve aforesaid problems, the author designed and researched a series of Fe-Mo/CAR bifunctional acid catalysts and realized the one-step extraction of DMM by methanol in fluidized bed reactor. Through screening and regulation, the optimum Fe-Mo/CAR bifunctional catalyst was identified. The result showed that this process and catalyst could overcome the disadvantages of traditional bifunctional catalyst and realize relatively high DMM yield. Among which, the methanol conversion ratio and DMM selectivity of Mo-Fe/ZSM-5 (silica-alumina ratio=80) bifunctional catalyst reached 87.44% and 93% respectively, while the DMM yield was 81.32%, which was much higher than that of other research results. Finally, the catalyst was characterized by nitrogen adsorption, X-ray diffraction, X-ray energy spectrum, scanning electron microscope, transmission electron microscope, infrared spectroscopy and other characterization means. The influence of Mo-Fe ratio, acid degree, oxidation-reduction ability and surface properties of catalyst on the catalytic activity was studied and the structure-function relationship and regulatory mechanism of the bifunctional catalyst were revealed.