Synthesis Of Mesoporous Fe-MCM-41 And Its Catalysis Research

Mesoporous molecular sieves MCM-41 have regularly arranged mono-dimention mesopores. Because of controllable pore size, big pore volume and specific surface area, MCM-41 has a wide range of application in catalysis and separation fields. In the catalysis field, molecular sieves are used as supports to enhance catalysis efficiency by enhancing effective areas of catalysis reaction, mesoporous molecular sieves partially substituted by heteroatoms are good catalysts, when iron atoms replace silicon atoms into the framework, strong Br(?)nsted acid sites will be produced, thereby iron-containing mesoporous silicates performance high activities in the selective oxidation of benzene or alkane, alkylation of aromatic hydrocarbon, and hydroxylation of phenol. With the raising requirements of environmental protection worldwide, every country accelerates the process of implementing the new oil standards which demand refineries to provide more clean and environmentally friendly oil, mainly with lower sulfur content. Hydrodesulfurization (HDS) is a widely used traditional desulfurization method, but it is difficult to remove dibenzothiophene (DBT). DBT can be oxidized to sulfoxide and sulfone by catalytic oxidation method, and removed by extraction or adsorption, thus transportation oil with ultra-low sulful content can be produced.In this paper we synthesized mesoporous molecular sieves with different iron contents in one step by hydrothermal method, and explored catalytic desulfurization effects of Fe-MCM-41 samples with H2O2 used as the oxidant, which achived good results.The work is divided into two parts:1. The preparation of Fe-MCM-41 catalysts. Cetyltrimethyl-ammonium bromide (CTAB) is used as the structure-directing agent, tetraethyl orthosilicate (TEOS) is used as the silica source, EDTA and tartaric acid are used as complexing agents respectively, Fe-MCM-41 is synthesized directly by hydrothermal method, pH,reaction time and iron content factors are researched. The prepared samples are characterized using XRD, N2 adsorption-desorption, HRTEM, etc. When using tartaric acid as the complexing agent, the molar ratio of Fe:Si is 0.15, Fe-MCM-41 still keep orderly structure and iron ions are introduced into the framework of molecular sieves, the pore size is 3.8nm, specific surface area is 987m2g-1,and pore volume is 2.049cm3g-1.2. Investigating the catalysis effects of catalysts with good structure property in oxidation desulfurization. Using petroleum ether adding DBT as model oil and H2O2 as the oxidant, then oxidation products are extracted. The desulfurization effects of molecular sieves with different iron contents are investigated in different conditions, including reaction time,reaction temperature and catalyst amouts. With Fe-MCM-41 (11.75wt%Fe), the sulfur content of model oil with 500ppm S can be decreased to 5.1ppm, sulfur removal is up to 98.98%, moreover, it has high reusability, for the third run, sulfur removal can achive 97.5%.