Preparation Of Super Acidic Zeolite And Its Application In Catalytic Viscosity Reduction Of Heavy Oil

With the rapidly increasing global energy consumption and the declining of conventional oil reserves,heavy oil will be the main petroleum supply in future because of its huge reserves.However,it is very difficult to explore heavy oil resources due to its high viscosity.In recent decades,several heavy oil recovery technologies have been developed,such as thermal recovery,chemical recovery,microbial recovery and catalytic aquathermolysis.Among them,catalytic aquathermolysis is a promising technology for practical application.Catalytic hydrothermal cracking can promote the conversion of heavy oil heavy components into light components,at the same time the quality of heavy oil was improved.Catalyst for heavy oil catalytic viscosity reduction reaction is very important.Sulfate-modified metal oxide is a kind of ideal solid superacid catalyst because of its superior acidic properties.Among them,SO₄^2-/ZrO₂ is the most common solid superacid,but the limited of solid specific superacid lead to insufficient surface acid sites.On the other hand,loss of the sulfuric acid will cause inactivation of the catalyst.To enhance the chemical stability and enlarge the specific surface area of the SO₄^2-/ZrO₂ catalyst,the catalyst is combined with zeolite,which has ordered pore size structure,large specific surface area and good stability.In this study,the mesoporous Zr alloyed Zeolite（SiO_x）catalyst with large surface area was prepared as a support matrix and SO₄^2-modified Zr-Zeolite(denoted as SO₄^2-/Zr-Zeolite)was used as a solid superacid catalyst to crack the heavy oil.Compared with the SO₄^2-/Zr-SiO_x nanoparticles catalyst,the amount of acid sites for the mesoporous SO₄^2-/Zr-Zeoliteis catalyst are significantly increased,and the stability is also enhanced.The as-prepared catalysts were applied heavy oil catalytic aquathermolysis.In additon,Ni O was selected as modifier to further improve the removal rate of N,S heteroatoms.The specific research contents are as follows.Improved heavy oil viscosity reduction efficiency by enhancing surface acid sites in SO₄^2-/Zr-Zeolite molecular sieve catalyst.The specific surface area of the catalyst was increased from96.67 m²/g to 297.55 m²/g by changing the structure of SO₄^2-/ZrO₂.The surface acid sites of the SO₄^2-/Zr-Zeolite catalyst is significantly increased by increasing the specific surface area,consequently,the viscosity reduction rate of the heavy oil is improved.After catalytic aquathermolysis,the content of saturated hydrocarbons and aromatics in crude oil were increased by 4.6%and 0.8%,respectively,while the resin and asphaltene decreased by 2.9%and 2.4%,respectively.The content of sulfur in crude oil was reduced by 0.07%and the quality of crude oil was improved.Enhanced viscosity reduction efficiency by increasing the content of Zr in SO₄^2-/Zr-Zeolite catalyst and hydrogen donor.Upon the molecular sieve structure,the viscosity reduction rate of SO₄^2-/Zr-Zeolite（4:1）catalyst was achieved 62%by adjusting the amount of n-butoxide and tetramethoxysilane from 1:1 to 4:1.Compared with the nanoparticles SO₄^2-/Zr-SiO_x（1:1）catalyst,the viscosity reduction rate of heavy oil increased by 40%.At the same time,the SO₄^2-/Zr-Zeolite（4:1）catalyst showed better hydrothermal stability,and the results of cyclic viscosity reduction test showed that the viscosity reduction rate of heavy oil did not decrease obviously.In order to further improved the viscosity reduction of heavy oil,the synergistic effect of different hydrogen donor and SO₄^2-/Zr-Zeolite（4:1）catalyst on viscosity reduction was investigated.The coexistence of tetrahydronaphthalene and the SO₄^2-/Zr-Zeolite（4:1）catalyst exhibited a synergistic effect to improve the viscosity reduction rate,and the viscosity reduction rate was increased from 54%of the to 92%.The main reason is that hydrogen donor can effectively prevent the repolymerization of the active chain formed by the catalytic reaction.The cyclic structure of the hydrogen donor is also beneficial to increases the steric hindrance of the product molecule,and effective to reduce the cross-linking of the product during catalytic aquathermolysis.Improved removal rate of N,S heteroatoms by modifying SO₄^2-/Zr-Zeolite catalyst with NiO.By modifying the NiO,the optimal heavy oil viscosity reduction rate reached to 58%.Among them,the denitrification rate was 16.7%and the desulfurization rate was 6.4%.So that the crude oil quality was improved.