(183a) Catalytic Bitumen Partial Upgrading Under Methane Environment

Heavy oil and bitumen extracted from oil sands such as the ones abundant in Canada cannot be directly sent to existing refineries mainly due to its high viscosity. Traditionally, hydrotreating is widely employed to break down the long carbon chain and complicated polycyclic molecular structure of heavy crude to lower the viscosity, and remove the impurities such as sulfur, nitrogen and metals simultaneously. However, such treatment consumes expensive hydrogen and requires extremely high operating pressure. Replacing hydrogen with methane, the principal component of natural gas, and lowering the operating pressure would significantly decrease the cost of oil refining. The activation and conversion of methane has been a great challenge due to its symmetric molecular structure and high C-H bond energy. The presence of higher hydrocarbons, which is rich during the upgrading process of heavy oil, would significantly enhance the conversion of methane. In the present work, methane is activated with ZSM-5 based catalysts loaded with active metals and upgrade the heavy oil at low pressure. The charged catalyst witnesses significant viscosity reduction, excellent product stability and compatibility, decreased total acid number, averaged molecular weight, asphaltene content, and increased H/C atomic ratio of the product. The reaction between the heavy oil molecules and methane is studied by choosing several representative model compounds including n-butylbenzene to analog the feedstock components in heavy oil. The study of the reaction is executed from multiple aspects with several analytic instruments, including the GC-MS analysis of products, which provides the composition information, and Diffuse Reflectance Infrared Fourier Transform (DRIFT) Spectroscopy, which detects the formation of organic species on the surface of the catalyst during the upgrading process. ¹³C and ²D enriched methane are also employed to track the catalytic pathways. Several key products such as ethylbenzene, propylbenzene, isopropylbenzene and butylbenzene, which are the saturation products of styrene, are separated and purified. Their ¹H NMR, ¹³C NMR, FTIR and GC-MS spectra reveal how the CH_x and H are added into unsaturated bonds. This work clearly demonstrates the feasibility of upgrading heavy oil by directly using cheap natural gas on zeolite-supported catalyst at moderate pressure. This mechanistic study would also benefit the rational design of catalyst for direct upgrading of heavy crude oil using natural gas in the future.