Study On The Co-catalytic Cracking Of VGO/bio-oil And Its Reaction Mechanism In A Pilot Scale FCC Riser

Bio-oil derived from biomass pyrolysis is considered to be the cheapest biofuel.However,when compared with conventional petroleum derived hydrocarbons,bio-oil has some disadvantages such as high oxygen content,low energy density and inferior stability.Therefore,bio-oil needs to be upgraded before it is used as standard fuels or chemicals.Fluid catalytic cracking(FCC)is one of the most important second processes in petroleum refinery to convert heavy oil into light hydrocarbons.Compared with catalytic hydrogenation,catalytic cracking of bio-oil can remove the oxygen without high pressure hydrogen and precious metal catalysts,which rejects the oxygen as water,carbon monoxide and carbon dioxide.However,direct introduction of bio-oil into catalytic cracking process will be easy to yield coke at the expense of some elements.Bio-oil co-processing with VGO relys on conventional FCC unit to accomplish the co-processing experiments.And the FCC riser is usually used to conduct co-processing research owing to its advantages of the short reaction residence time and large throughput.Based on the pilot scale FCC riser setup,the researches in present dissertation are focused on co-processing of different bio-oils with VGO,and catalytic upgrading of bio-oil water-insoluble fraction into high value-added bio-based chemical.The reaction mechanisms of hydrogen transfer to deoxygenate during co-processing are investigated by using Gaussian quantum chemistry calculation software package.The water-soluble of bio-oil contains many highly active compounds such as carboxylic acids,aldehydes,ketones and sugars,which are the main coking precursors during co-processing and results in the lower H/Ceff of bio-oil.The experiment results indicate that decarbonylation and decarboxylation reaction present in the process of biomass catalytic pyrolysis and in-situ upgrade the biomass pyrolysis gas,which can effectively reduce the oxygen content and increase the carbon and hydrogen content of CPO.Mild hydrotreating can also reduce the content of highly active compounds and increase the H/Ceff of bio-oil.The co-processing experiments are successfully implemented without any operation deterioration when catalytic pyrolysis bio-oil up to 10 wt.%addition.Under the same reaction conditions,the conversions of co-processing feedstock are higher than the only VGO cracking.The yields of gasoline,light cycle oil,bottom oil and coke during co-processing are similar with only VGO feeding.At a conversion of about 70%,the oxygen content in co-processing liquid is 0.22%,which shows that the oxygen in bio-oil can be completely deoxygenated during co-processing.The renewable carbon content in co-processing gasoline is 7.0%,which is higher than raw bio-oil co-processing.This also indicates that the renewable carbon in bio-oil can be utilized effectively by integrating biomass catalytic pyrolysis and catalytic pyrolysis oil co-processing.The content of carbon and hydrogen increase respectively from 73.1%and 7.4%of biomass fast pyrolysis bio-oil to 56.7%and 5.6%of biomass catalytic pyrolysis oil,and oxygen content decreases from 38.2%to 19.5%.However,the liquid yield of catalytic pyrolysis is 26.8%,which is lower than 46.4%of fast pyrolysis.And the non-condensable gas yield of catalytic pyrolysis is 19.1%,which is higher than 11.3%of fast pyrolysis.This indicates that decarbonylation and decarboxylation reaction present in the process of catalytic pyrolysis and at the same time results in the loss of some elements and the decrease of liquid yield.Raw bio-oil,upgraded bio-oil at different hydrogenation conditions(SPO-1 and SPO-2)are co-processed with VGO with 10 wt.%addition.Under the same reaction conditions,the conversions in raw bio-oil,SPO-1 and SPO-2 co-processing are higher than only VGO cracking.When compared to VGO cracking at the conversion of about 70%,the gasoline yield in raw co-processing decreases,but both SPO-1 and SPO-2 co-processing gasoline yield increase.And the renewable carbon contents in gasoline from raw bio-oil,SPO-1 and SPO-2 co-processing are respectively 2.0%,5.3%and 6.1%,which shows that upgraded bio-oil could increase the renewable carbon content and enhance the utilization efficiency of renewable carbon.Hydrogen transfer reaction is an important pathway to deoxygenate during co-processing.Gaussian software package is used to study the mechanism of hydrogen transfer reaction by selecting phenol and iso-butane as model compounds to respectively represent bio-oi and VGO.The transition states are found corresponding to three process including phenol adsorption on ZHSM-5,iso-butane dissociation into carbocation,and recover of Bronsted acid sites.Taking 8T HZSM-5 for example,the activation energy corresponding to above three processes is respectively 278.78,449.00 and 6.12 kJ/mol.A preliminary mechanism is proposed for hydrogen transfer reaction.During the quantum calculation,we find that the water plays a key role in the formation of carbocation.The water-insoluble fraction has the properties of poor fluidity,high density and viscosity.The water-insoluble fraction is not suitable for being co-processing feedstock because the coke cake is easy to form during co-processing.Many substituted phenols are included in water-insoluble,which have potential value to produce bio-jet fuel and chemicals.Based on the results of quantum chemistry calculation and specific model compounds,at the atmospheric pressure of nitrogen and temperature of 400?,the experiment results show that the mixture of water-insoluble fraction and methanol can be converted into high purity hexamethylbenzene(>99%)in the presence of ?-Al2O3,the yield and renewable carbon content of which is respectively about 40%and 58%.The bio-oil co-processing research in present dissertation is a technology to upgrade and utilize bio-oil.The experiment and mechanism research provide the theory refrence for achieving the low-carbon goal of petrochemical industry.And as to the waster-insouble fraction being unsuitable for co-processsing,this work also provides an academic example of complex bio-oil into high purity and value-added bio-based compound.