过渡金属/酚醛树脂基活性炭的制备及其吸附脱硫脱氮性能研究

Due to the increasingly stringent environmental regulations on sulfur concentration in transportation fuels, ultra-deep desulfurization/denitrogenation of liquid hydrocarbon fuels has become a more and more important research subject. Using adsorbents to selectively remove the refractory sulfur and/or nitrogen compounds in liquid hydrocarbon fuels is one of the promising approaches for producing ultra clean fuels that could meet the most stringent fuel specifications for transportation fuels. In the present study, phenolic resin-derived activated carbon with highly dispersed Cu，Ni，Fe，Ag and Co within the carbon matrix were prepared by blending transition metal nitrate into low cost and water soluble phenolic resin before carbonization and physical activation. The metal-loaded carbon-based sorbents containing Cu，Ni，Fe，Ag and Co species as media for the reactive adsorption were tested at room temperature for removal of heterocyclic sulfur and nitrogen compounds from model fuels. Furthermore, glow discharge plasma was introduced to prepare transition metal oxides loaded carbon-based sorbents containing Cu+，Ag+，Ni2+ as media for the π complexation adsorption. At the same time, the performance of adsorbent was enhanced by oxygen plasma treatment via introducing oxygen functional groups to the carbon surface. The above research on adsorbent preparation could provide new ideas, new methods for designing adsorbent for desulfurization/denitrogenation, promote its application in the field of ultra-deep desulfurization/denitrogenation.

由于环境法规对燃油中硫含量的规定日益严格，燃油深度脱硫脱氮成为精炼厂目前亟待解决的问题。加氢过程中难炼的硫氮杂环化合物在吸附过程中却易脱除。本项目利用价格低廉的水溶性酚醛树脂为炭前驱体，采用前驱体共混法，制备负载高分散过渡金属组分（Cu，Ni，Fe，Ag，Co）的酚醛树脂基活性炭吸附剂，考察其在模型油中的吸附脱硫脱氮性能。进一步利用辉光放电等离子体处理技术制备含金属阳离子Cu+，Ag+，Ni2+的过渡金属氧化物-酚醛树脂基活性炭吸附剂，构建π络合吸附和活性炭吸附协同作用。同时利用氧气等离子体处理增加活性炭表面的含氧基团，促进吸附脱硫脱氮。以上吸附剂的研究将为制备脱硫脱氮吸附剂提供新思路，新方法，促进其在清洁燃料深度脱硫脱氮领域中应用。

一方面，确定了商品水溶性酚醛树脂的固化碳化条件。采用前驱体共混法，经CO2活化，制备了一系列载过渡金属/酚醛树脂基活性炭。其吸附脱硫脱氮能力的大小顺序为：PFACCu-0.5> PFACCo-0.5> PFACFe-0.5> PFACNi-0.5> PFACZn-0.5> PFAC。最佳铜掺杂量为2.5 wt.%时，样品比表面积从未掺杂的402m2/g增大至522m2/g，对多组分混合油的吸附量从0.98 mmol/g升高至2.0 mmol/g。其吸附动力学热力学被进一步深入研究。另一方面，合成了酚醛树脂基球形炭，未活化比表面积即可达到470m2/g。添加造孔剂聚乙二醇改性的球形炭，比表面积升高至615 m2/g，孔容为0.234 cm3/g。在模型油MF#1中，改性后样品对各吸附质的最大吸附量为：吲哚（1.79mmol/g）>喹啉（1.40 mmol/g）>DBT（1.08mmol/g）。在混合模型油MF#2中，最大吸附总量达到2.91mmol/g。进一步也研究了该球形炭的吸附动力学热力学。考察了CO2和水蒸气活化球形炭的最佳条件。水蒸气活化的球形炭吸附效果较好，对混合模型油MF#2的吸附总量达到3.5mmol/g。与未活化，CO2活化、造孔剂改性样品对比，水蒸气活化后，样品对DBT的吸附量明显高于对氮化物的吸附量。这可归因于水蒸气活化扩大了活性炭的孔径，有利于大直径分子DBT的吸附。在球形炭基础上，采用浸渍法负载过渡金属，水蒸气活化后，对MF#2的吸附量大小顺序为PHSAC-Cu>PHSAC-Co>PHSAC-Ag>PHSAC-Fe>PHSAC。负载金属Cu组分的活性炭吸附量最高，可达到5.15mmol/g。同时，考察了前驱体共混法，制备载Cu/酚醛树脂基球形炭的吸附性能。在未活化的情况下，对MF#2的吸附量可达到2.06mmol/g，与商品水溶性酚醛树脂采用共混法制备的载Cu活性炭的最佳吸附量相当。进一步进行了载Cu前后酚醛树脂基球形炭吸附选择性研究。载Cu后球形炭抑制芳烃与球形炭之间的π-π键作用，显著增强对硫/氮化物吸附选择性。当模型油中芳烃增至20%时，对载Cu/球形炭的脱硫脱氮性能未产生明显影响。