Study On The Mechanism Of Ni?SO₃CH₃?₂ In The Catalytic Cracking Of Sulfide In Heavy Oil

Thick oil is also called heavy oil.The composition is the macromolecule,and its microstructure is different.It results high viscosity coefficient,poor mobility,high relative density and other characteristics,so it isn't easy to extract from underground,and processing.It is necessary to reduce the mobility under the catalytic cracking of sulfide in heavy oil.It is useful to develop a more effective catalyst to improve the efficiency of heavy oil recovery by studying the mechanism of reducing the viscosity of sulfide in heavy oil.In the thesis,Gaussian 03 software and B3LYP is used to calculate on the basis of the density functional theory?DFT?,the basis set of Ni element is the Lanl2dz,the basis set of C,H,O and S element is the 6-31+G*.The main forms of sulfur compounds in heavy oil are sulfide,thiophene,tetrahydrothiophene and it's derivatives,so CH₂CHSCH₃ is used as the straight chain thioether representative of organic sulfide in heavy oil,thiophene is used as the representative of closed-chain hydrocarbon containing a large?bond in heavy oil sulfide,tetrahydrothiophene is used as the representative of closed-chain hydrocarbon uncontaining a large?bond in heavy oil sulfide.Ni?SO₃CH₃?₂ is used as catalyst.The C-S band clevage,enol structural rearrangements to aldehydes,aldehyde decarbonylation and desulfurization process in the catalytic cracking reaction are study on the quantitative calculation.the reactants,intermediate,transition states and products are confirmed according to the intrinsic reaction coordinate?IRC?calculations,the reaction path are determined through careful analysising the calculation results,At the same time,sulfide in heavy oil catalytic cracking reasons is explained from the reaction energy barrier,electronic structure,molecular structure,energy and valence bond angle in the microcosmic level.The conversion of sulfides in heavy oil is studied.After the Ni?SO₃CH₃?₂ is added into the heavy oil,the sulfides cracking is studied at different pH conditions.In order to explain the composition and structure changes,Analyses are conducted on the elements,the viscosity reduction,GC spectrum of gas after the reaction,IR spectrum of heavy oil samples before and after the reaction,nuclear magnetic resonance and other aspects of the catalytic cracking of.In according to the combination of calculation and experiment,the correctness of the calculation is confirmed,and the mechanism of sulfide catalytic cracking is clarified.During the CH₂CHSCH₃ catalytic cracking reaction:C-S bond breakage reaction take place in the Ni?SO₃CH₃?₂ as the catalyst,it is the OH^-that attacks C-S causes the C-S bond cleavage,and generates CH₂CHOH and SCH₃^-,then SCH₃^-and H⁺bind and generate CH₃SH rapidly,the reaction barrier 24.3 kJ/mol.CH₂CHOH transfers proton and makes structural rearrangements with the aid of H₂O.The reaction barrier is 67.0kJ/mol.In CH₃CHO decarbonylation reaction,the catalyst is Ni²⁺,the reaction products is CH₄ and CO.The catalytic decarbonylation reaction barrier is 147.0kJ/mol.In the catalytic hydrodesulfurization of C₃H₅SH,the catalyst is the Ni²⁺,the reaction barrier is 98.0 kJ/mol.During the cleavage reactionDuring the C₄H₄S catalytic cracking reaction:C-S bond breakage reaction take place in the Ni?SO₃CH₃?₂ as the catalyst,first the OH^-attacks C-S and causes the C-S bond cleavage,generate SC₄H₄OH^-,the reaction barrier 66.2 kJ/mol,then SC₄H₄OH^-and H⁺combines rapidly and generates HSC₄H₄OH,HSC₄H₄OH transfers proton and makes structural rearrangements with the aid of H₂O.The reaction barrier is 77.9kJ/mol.In HSC₃H₄CHO decarbonylation reaction,the catalyst is Ni²⁺,The HSC₄H₄OH generates C₃H₅SH and CO in the decarbonylation reaction with the Ni²⁺as catalyst.The reaction barrier is 157.5 kJ/mol.In the catalytic Hydrodesulfurization of C₃H₅SH,the catalyst is the Ni²⁺,the catalytic hydrodesulfurization reaction barrier is 140.6 kJ/mol.During the C₄H₈S catalytic cracking reaction:C-S bond breakage reaction take place in the Ni?SO₃CH₃?₂ as the catalyst,it is the OH^-that attacks C-S and causes the C-S bond cleavage,generates SC₄H₈OH-,the reaction barrier is 45.3 kJ/mol.then SC₄H₈OH^-and H⁺combines rapidly and generates HSC₄H₈OH,C₄H₇OH and H₂S are generated in the HSC₄H₈OH desulfurization with the Ni²⁺aid,the reaction energy barrier is 183.0 kJ/mol,C₄H₇OH makes structural rearrangements and generate the C₃H₇CHO with the aid of H₂O.The reaction barrier is 113.9 kJ/mol,it is the Ni²⁺plays the key role in the C₃H₇CHO decarbonylation,the reaction barrier is 136.5kJ/mol.In the experimental study of sulfide cracking of Ni?SO₃CH₃?₂₂ as the catalyst in heavy oil,S has been released from H₂S,when the pH is eight,the conversion of S reaches 70.158%and the viscosity reduction rate reached 94.9%.It shows the reaction is carried out under alkaline conditions,and knows that the cleavage of the C-S bond is due to OH^-attacking C-S band.There is not only the final product in the calculations of H₂S,CO₂,CO and CH₄,but also the C₁₇H₂₇CHO,and the intermediate product of the C₁₉H₃₃OH and C₁₈H₃₃OH calculations in the products.The decarbonylation reaction occurres,and the alcohols,ethers and esters are formed in the reaction.The C-O stretching vibration ratio is slightly higher than that before reaction,the aromaticity of the heavy oil decreases from 0.443 to 0.384,and the BI increases from 0.129 to 0.161,indicating that the fragmentation is effectively carried out.The calculation results and the experimental data are analyzed.The experimental results show that the intermediate products and the final products appear in the calculation,which shows the correctness of the calculation.In the cleavage reaction of Ni?SO₃CH₃?₂ in the sulfide of heavy oil,the C-S band cleavage is achieved by the OH^-,and then the enol is rearranged to form aldehyde by H₂O,and then decarbonylation reaction and hydrodesulfurization reaction occurs with the Ni²⁺ascatalyst.