Studies On Synthesis, Characterization And Photocatalytic Oxidation Performance Of Catalysts In Photocatalytic Oxidation Desulfurization Of Diesel Oil

Improvement of industrialized hydrodesulfurization and development of non-hydrodesulfurization have been steped up, in order to meet the new standards for sulfur content in the fuel oil. In the non-hydrodesulfurization, photochemical desulfurization is a novel method, which is easy to control and save energy, etc. This paper uses the model compounds and diesel oil as object. Photocatalytic oxidation desulfurization performance and factors of Riboflavin/O₂, TiO₂/BC/H₂O₂, Ti-containing molecular sieve/H₂O₂, amphiphilic Ti-containing molecular sieve/H₂O₂ and amphiphilic Ti-containing molecular sieve/O₂ are investigated in detail. The oxidation reaction mechanism and the reaction kinetics are also studied. The innovation research results are acquired.The following are the five parts of the paper.1.Oxidation desulfurization of DBT was carried out by using riboflavin (RF) as photosensutizer and water as sovent. Effect of RF concentration and air flow on removal ratio of DBT were investigated.The results show that the removal ratio of DBT is up to 60% under condition which are RF concentration 20 mg/mL, air flow 80¹00mL/min and irradiation time 2h. DBT was sensitized by RF through 1O₂ mechanism; the kinetics of oxidation of DBT is fist-order. Oxidation products are DBT monoxide, DBT sulfone and SO4-2 by mass spectra.2.Oxidation desulfurization of DBT was carried out by using TiO₂ supported on banmboo carbon (BC) which has a similar structure to C60 and carbon nanometer tube as photocatalyst and H₂O₂ as oxidant. Effect of adsorption of BC on DBT and effect of amount of loaded TiO₂ on BC, H₂O₂ concentration and amount of TiO₂/BC on removal ratio of DBT were investigated in detail. The results show that BC has very large adsorption capacity of DBT, the adsorption behaviour is described better by a monolayer Freundlich type isotherm and kinetic data follows a pseudo second-order model. The optimum reaction conditions are amount of loaded TiO₂ 15% (wt%), H₂O₂ concentration O/S 14(mol) and amount of TiO₂/BC 0.02g/10mL model diesel. Removal ratio of DBT is up to 66% under optimum reaction conditions. In addition,we also found TiO₂/BC can locate just at the oil-water phase boundary, which lead to a different reaction model from other photocatalysts.3. Ti-NaY and Ti-βwere prepared using liquid-solid isomorphous substitution of Ti(SO₄)₂ method and Ti-MCM-41 was prepared using improved microwave heating method (in domestic microwave oven). Prepared Ti-NaY, Ti-βand Ti-MCM-41 were characterized by XRD, FT-IR,SEM and TEM,EDS and UV-Vis. The results show that Ti was introduced in framework of molecular sieve successfully; Prepared Ti-MCM-41 has a regular structure, a good long order hexagonal arrangement and a stronger UV absorbance. Compared with the reported synthesis methods, the remarkable vantage of this method are simpler operation, shorter crystallization time (only 40 min), lower energy consumption and facility request. The order of photocatalytic activity of Ti-containing molecular sieve is Ti-MCM-41>TS-1>Ti-NaY>Ti-β.4. Amphiphilic Ti-containing molecular sieve were prepared by partial modification of the external surface of TS-1, Ti-NaY, Ti-βand Ti-MCM-4 with trimethylchlorosilane (TMS), dimethyldichlorosilane (DMS) octadecyltrichlorosilane (OTS). XRD,FT-IR,SEM and BET were used to characterize the surface properties of these modified samples. The results show that partial modification of the external surface of TS-1, Ti-βand Ti-MCM-4 with three modifiers is successful,but partial modification of the external surface of Ti-NaY is only successful with OTS. In addition,the structure of OTS-Ti-NaY collapsed seriously,while other modified samples have no change for crystalline,pattern and pore structure. The order of photocatalytic activity of these modified samples is OTS-Ti-MCM-41> DMS-TS-1>TMS-Ti-β> OTS-Ti-NaY. Photocatalytic activity of these modified samples are higher and amount of photocatalysts is fewer than that of unmodified these samples. Removal ratio of DBT is up to 98% after static irradiation 2h by using OTS-Ti-MCM-41 as photocatalyst. Photocatalytic activity of amphiphilic samples don't decrease obviously after reused for 5 times. Removal ratio of DBT can be up to 85% after static irradiation 2h by using OTS-Ti-MCM-41 as photocatalyst and air as oxidant.5. In order for deep desulfurization, oxidation desulfurization of diesel (sulfur content 1500μg/g) was carried out by using several photocatalytic systems mentioned in previous chapters. The results show that the order of photocatalytic activity to desulfurization of diesel is OTS-Ti-MCM-41 > OTS-Ti-MCM-41/O₂ > TiO₂/BC > RF/O₂. Sulfur content was reduced to 30μg/g in OTS-Ti-MCM-41 system and 50μg/g in OTS-Ti-MCM-41/O₂ system, which can meet European-â…¢standard. In addition, effects of paraffin, olefin, aromatic hydrocarbon and nitrogenous compounds on removal ratio of DBT were investigated. We found that olefin had greater effect on desulfurization than aromatic hydrocarbon, while paraffin had no effect on desulfurization. Nitrogenous compounds were also removed partly in these photocatalytic systems. The order of denitrification activity is the same as that of desulfurization activity in these photocatalytic systems.