| With the increasing demands for energy resources and the serious shortage of conventional hydrocarbon resources,heavy oil,a type of unconventional hydrocarbon resource with great potential,has attracted worldwide interest.However,there are difficulties in the heavy oil transportation and processing such as high viscosity and poor fluidity.Therefore,for a long time,people have explored various chemical and physical methods to reduce the viscosity of heavy oil and achieve better fluidity for subsequent transportation.However,considering that there are few light fractions such as saturate and aromatic in the heavy oil,but most of which are heavy fractions such as resin and asphaltene,which contain more sulfur,nitrogen,oxygen and trace metals and are the most difficult raw materials to process.Therefore,in order to further facilitate subsequent processing,scientists usually use thermal modification to upgrade heavy oil,which can not only facilitate subsequent transportation,but also decrease heavy fraction in heavy oil to a certain extent for subsequent processing.In this work,alkaline-treated Fe/ZSM-5(AT-Fe/ZSM-5)was modified by continuous alkali treatment and ion exchange for catalytic pyrolysis of glycerol and biomass to upgrade heavy oil corporately.The prepared catalysts were characterized by XRD,SEM,EDX,BET,TEM,NH3-TPD,Pyridine-IR.It was found that the average pore size,specific surface area,total pore volume and Bronsted acid sites were all increased.In the process of applying AT-Fe/ZSM-5 to upgrade heavy oil,a large number of experiments has been done and the effect of upgrading heavy oil using any one or two of 0.4wt%AT-Fe/ZSM-5,1 wt%biomass and 5 wt%glycerol was not significant.Therefore,we choosed the AT-Fe/ZSM-5 and biomass,glycerol combined together to reduce the viscosity of heavy oil.The ratio of them in the heavy oil was evaluated for so many times.Finally,we found that the effect of upgrading heavy oil could be optimal when 0.4wt%alkali-treated Fe/ZSM-5,1wt%biomass and wt%glycerol were added into the heavy oil.The effect of temperature and time on upgrading heavy oil was evaluated based on the optimal ratio of additives in the heavy oil.Compared with pyrolysis reaction under the same condition,the viscosity was decreased from 22300mPa·s to 417mPa·s and the corresponding optimal viscosity reduction was 98%at 350℃.Besides,the structures and the group compositions of heavy oil samples before and after reactions at 350℃ were analyzed by SARA,FT-IR,EL,1H NMR,GC-MS.Meanwhile,the synergistic effect of alkali-treated Fe/ZSM-5 with glycerol and biomass was proposed and confirmed in this paper from the angle of upgrading heavy oil.Based on the analysis of catalysts and heavy oil,the mechanism of upgrading heavy oil was proposed:(1)Bio-oil produced from the co-pyrolysis AT-Fe/ZSM-5(alkali treatment-Fe/ZSM-5),biomass and glycerol mainly includes alcohols,phenols and ketones.These polar substances may formed hydrogen bonds between them and were penetrated into the supramolecular model of colloidal asphalt components to loosen their structure and reduce the viscosities of heavy oil to a certain extent;(2)Thiophene and Tetrahydrothiophene in heavy oil reacted with water to form hydrogen as a hydrogen donor proposed by Clark;(3)Based on the mechanism of free radicals and carbon cations in oil pyrolysis,the author proposes two stages of reaction in the process of catalytic upgrading heavy oil.The first stage mainly followed free radical reaction mechanism,and the second stage mainly followed mechanism of carbon cations reaction;(4)Lipids in bio-oils,as well as lipids produced by esterification of carboxylic acids and glycerol,alcohols and phenols in bio-oils,may play some roles similar to oil-soluble polyesters,such as changing the polymerization state of resins and asphaltenes in the heavy oils to reduce the interaction between them,thus reducing the viscosity of oils.AT-Fe/ZSM-5 after upgrading heavy oil was recycled and applied in the upgrading heavy oil again.It was found that the effect of upgrading heavy oil was remained. |
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