Experimental Study On Viscosity Reduction And Modification Of Heavy Oil Catalyzed By Metal Nanocrystals

Heavy oil has the characteristics of high viscosity,high density and poor fluidity,which brings a number of difficulties to exploitation,gathering and processing.Approximately 70%of the existing petroleum reserves in the world are heavy oil.Therefore,rational and efficient utilization of heavy oil resources has a very important strategic significance.In this work,the effect of bifunctional metal nanocrystals on catalytic cracking hydrogenation and viscosity reduction of different heavy oils was studied.The main research contents are as follows:Monometallic Ni,Pd and bimetallic Ni-Pd alloy nanocrystal catalysts were prepared by liquid phase reduction method.The catalytic cracking hydrogenation and upgrading of Nanpu 35-2 heavy oil were studied with prepared catalysts and hydrazine hydrate(N2H4.H2O)as hydrogen donor.The catalysts were characterized by TEM and XRD technologies,the results showed that metal nanocrystal catalysts has good solubility,the particle size was about 6.0 nm,and size distribution was uniform.The optimal reaction process parameters were determined by four factors and three levels orthogonal experiments.The SARA four components contents of crude oil and upgraded oil samples were tested by petrochemical industry standards NB/SH/T 0509-2010 method.The physical properties of crude oil and upgraded oil samples were characterized and analyzed by optical microscopy,TG-DTG,GC-MS and FT-IR technologies.The results showed that metal nanocrystal catalysts have dual functions.On the one hand,they can catalyze the cracking of heavy oil macromolecules,on the other hand,hydrogen donor can be decomposed to produce hydrogen by them.Among all catalysts,monometallic Pd nanocrystals combined with hydrazine hydrate presented the best viscosity reduction effect on Nanpu 35-2 heavy oil.After catalytic cracking hydrogenation reaction,the mass fractions of light component and heavy component are 75.85 wt%and 24.15 wt%,respectively.The viscosity of upgraded oil decreased from 2688 mPa·s to 235 mPa·s,the viscosity reduction rate was 91.3%,the viscosity of crude oil decreased irreversibly,the lightening degree and saturation degree of crude oil increased,and the quality of crude oil improved.Monometallic Ni,Fe and bimetallic Ni-Fe alloy nanocrystal catalysts were prepared by liquid phase reduction method.The catalytic cracking hydrogenation of Lvda 32-2 dehydrated crude oil was studied by using the catalysts and hydrazine hydrate as hydrogen donor.The prepared catalysts were characterized by TEM and XRD technologies,the results showed that the size distribution was uniform.Four groups of comparative experiments of catalytic cracking and hydrogenation of Lvda 32-2 dehydrated crude oil were performed under the reaction conditions of catalyst amount is 0.2 wt%,the hydrogen donor amount is 5 wt%,the reaction temperature is 240?,and the reaction time is 24 h.The basic physical properties of crude oil and upgraded oil samples,such as viscosity,contents of four components and distillation temperature ranges,were tested through experimental methods.The results showed that the Ni-Fe alloy/N2H4.H2O system presented the best viscosity reduction effect,the content of light components of upgraded oil increased to 89.20 wt%,the viscosity of crude oil decreased from 1630 mPa·s to 72 mPa·s,the viscosity reduction rate is 95.6%.The crude oil and upgraded oil samples were analyzed by optical microscopy,TG-DTG,GC-MS and FT-IR methods.The results showed that after catalytic cracking and hydrogenation reaction,the contents of light components increased,the chain and ring structure of some macromolecules of crude oil was destroyed,and the lightening degree of crude oil increased.The molecular structures of Nanpu 35-2 heavy oil and upgraded oil samples were studied by improved B-L method.Firstly,the contents of HA,H?,Hp and H? of the resins and asphaltenes were obtained by 1H NMR and CHONS element analysis technologies.Then the aromatic carbon ratios fA,aromatic condensation degrees HAU/CA and branching degrees BI were obtained.The average molecular weights of asphaltenes of crude oil and upgraded oil samples were measured by GPC method,and the average structural parameters of asphaltenes,such as cyclane numbers,alkyl ring numbers and aromatic carbon numbers were obtained.Finally,molecular formulas and molecular structures of asphaltenes were obtained.The results showed that the molecular structures of asphaltenes of Nanpu 35-2 crude oil presented a certain degree of fracture after catalytic cracking and hydrogenation reaction.Thermogravimetric experiments were carried out on the resins and asphaltenes of Nanpu 35-2 crude oil and Lvda 32-2 dehydrated crude oil under three heating rates.The formula lnk0=A+B(E-Emax)of the relationships between pre-exponential factor k0 and E were obtained by Distribution Activation Energy Model(DAEM).The maximum activation energies Emax and pyrolysis characteristics of asphaltenes and resins of crude oil were obtained through this method.Furthermore,the dynamics characteristics of thermal cracking of asphaltenes and resins was obtained.