非含硫金属盐对稠油水热裂解生成硫化氢影响实验

高含硫稠油注蒸汽开采过程中,稠油、水蒸气和岩石基质间将发生水热裂解和硫酸盐热化学还原反应,并产生H₂S。为排除硫酸盐热化学还原生成H₂S反应,研究了金属离子对高含硫稠油水热裂解反应生成H₂S的催化作用,开展了AlCl₃、MgCl₂、CaCl₂和ZnCl₂这4种不含硫金属盐与稠油的水热裂解反应实验。实验结果表明:在240~300℃范围内,Al³⁺、Mg²⁺、Ca²⁺、Zn²⁺对稠油水热裂解反应生成H₂S均有催化作用,且Al³⁺的催化效果最好;pH值越低水热裂解生成H₂S反应越强烈,这是因为金属盐溶液呈酸性使H⁺质子化作用加强,而且金属离子对水热裂解中间反应包括C-S键断裂、加氢脱硫、水气转换等反应有催化作用;在一定浓度范围内,金属盐浓度越高,溶液pH值就越低,且金属离子与反应物接触几率增加,对水热裂解催化效果越明显,生成的H₂S越多。

An experiment on the influences of non-sulfur-bearing metal salt on hydrogen sulfide formation by aquathermolysis reaction of heavy oils

In the exploitation of high-sulfur heavy oil using steam injection method, aquathermolysis and thermochemical sulfate reduction occur among heavy oil, steam and rock matrix, thus forming the reaction product H₂S. To avoid H₂S formation by thermochemical sulfate reduction, the catalytic effect of metallic ions on H₂S formation by aquathermolysis of high-sulfur heavy oil was studied here. Meanwhile, the aquathermolysis reaction experiments between four non-sulfur-bearing metal salts(AlCl₃, MgCl₂, CaCl₂ and ZnCl₂) and heavy oil were also carried out. The experimental results show that within the temperature range of 240-300℃, Al³⁺, Mg²⁺, Ca²⁺ and Zn²⁺ all have certain catalytic effect on H₂S formation by aquathermolysis reaction of heavy oil, and Al³⁺ shows the optimal catalytic effect. The lower the pH value is, the stronger the aquathermolysis reaction will be. It results from the enhanced H⁺ protonation due to the acidity of metal salt solutions, and metal ions has catalytic effect on the intermediate reactions in aquathermolysis, such as C-S bond breaking, hydrodesulfsurizing and water-gas shift reaction. Within a certain density range, the higher the metal salt concentration is, the lower the pH value will be, the higher the chance of metal ions to contact reactants will be, the more significant the catalytic effect on aquathermolysis will be, and the more the generated H₂S will be.