【作者】 吴建芝；

【导师】 李春虎；

【作者基本信息】 中国海洋大学 ， 化学工程， 2007， 硕士

【摘要】 以煤、石油和天然气为原料生产氨、甲醇、甲烷化煤气等产品时大多使用高效催化剂或贵金属催化剂,原料气中硫化物中毒是催化剂失活的主要原因,微量的硫化物(如H2S为0.1ppm)就可使催化剂完全失去活性。本论文选用内蒙古鄂尔多斯活性半焦作为活性炭基材料脱硫剂的前驱体,利用高压水热活化、硝酸氧化和高温煅烧三种方式以及它们之间多步组合改性方式制备出了系列改性半焦脱硫剂。对原料半焦和改性半焦的表面总酸碱性官能团含量进行了滴定与分析。滴定与分析结果表明:原料半焦含有较高的含氧官能团和固定碳,表面酸碱性官能团含量都较小,其中表面碱性官能团含量高于表面酸性官能团含量;高压水热化学改性造成改性半焦表面酸性官能团减少,提高了表面碱性官能团的含量;硝酸氧化改性,增加了改性半焦样品表面含氧官能团的含量,同时也提高了改性半焦表面含氮官能团的含量,其脱灰能力非常明显;高温煅烧时,氧气或水的存在都能增加半焦表面的碱性官能团,增湿通氧煅烧后的改性半焦样品表面碱性官能团含量最高。在模拟原料气气氛下,利用固定床反应器,对原料半焦和改性半焦脱硫剂脱除H2S的性能以及工艺操作参数对脱硫活性的影响进行了研究。结果表明:原料半焦脱除原料气中H2S的效率和硫容都很低;高压水热化学、硝酸氧化和高温热处理三种改性方式可提高改性半焦脱硫效率和硫容,高压水热化学处理活性半焦后,用HNO3活化1.5h,水洗干燥后于720℃下,在约1%O2、45%H2O其余由氮气平衡的氛围中煅烧1.5h,这样制备的活性半焦脱硫效果最好;负载CuO的半焦,其脱硫能力提高明显;温度为75℃,水含量为8-10%,氧气含量在3-5%范围内,活性半焦的脱硫性能最佳;当空速小于900h-1时,脱硫反应为扩散控制,空速大于900h-1时,为反应控制。分析不同活性半焦的脱硫性能与其物性参数的关系,发现提高表面碱性官能团含量能改善活性半焦脱除H2S的效率和硫容,但硫容与表面碱性官能团含量不存在正比关系。改性半焦脱除H2S的效率和硫容,随微孔体积增大而增大,与总孔容也无线性关系。活性半焦比表面积较大时,脱硫效果较好,但脱硫能力与比表面积不存在线性关系,比表面积不是影响脱硫剂脱硫活性的关键因素;XRD分析表明,按CuO: C=4%(质量比)活性半焦负载硝酸铜,在550℃和720℃煅烧后表面有CuO存在,脱硫后有CuS生成。采用溶剂再生法和气体再生法对脱除H2S后的失活半焦再生。溶剂再生时所用的溶剂为HNO3溶液,氧化的方法使活性半焦再生。气体再生时所用到的气体分别为N2,含20%O2的N2,它们的再生原理分别是热再生,氧化单质S再生。再生效果最好的是65%的HNO3溶液和含20%O2的N2,它们的一次再生率分别为66.70%和85.93%。通过上述的研究工作,能够更加清楚的认识到活性半焦脱除H2S的原理以及各种因素的影响,从而为进一步工业应用积累基础数据。更多还原

【Abstract】 High-efficiency or noble metal catalysts have always been used during the process of producing ammonia, methanol and methanation gas when coal, petroleum and natural gas are as raw materials. Poisoning of sulfur complexes from raw gas is the major reason of the catalyst deactivation. The minim hydrogen sulphide (e.g, the H2S content is 0.1ppm) can make catalysts deactivate completely.In this paper, activated semi-coke in Inner Monogolia is as precursor of desulphurizer based on activated carbon. A series of H2S removal agents of activated semi-coke are prepared from activated semi-coke by means of hydrothermal method, HNO3 oxidation and heat treatment at high temperature as well as their combined modification. The composition and surface acid-base properties for semi-coke and activated semi-coke samples are characterized by means of acid-base titration methods. The analytical results show that raw semi-coke is higher in oxygen-containing functional groups content and fixed carbon content. Its contents of surface acidic and basic functional groups are lower, but the contents of basic functional groups are higher than that of acidic functional groups. The hydrothermal chemical modification can decrease the surface oxygen-containing acidic functional groups and raise the content of surface basic functional groups. HNO3 oxidation modification can increase the contents of oxygen-containing and nitrogen-containing functional groups of modified semi-coke. The de-ash capacity of HNO3 oxidation modification increases obviously. The basic functional of the surface of semi-coke can be increased by calcining at high temperature when oxygen or water is existent. The highest content of surface basic functional groups of modified semi-coke is by calcining at moistening and ventilating oxygen. The capacity of H2S removal and effect of process operation condition on H2S removal activities for raw semi-coke and the activated semi-coke are investigated in fixed bed reactor in simulated raw gas. The results indicate that the H2S removal efficiency and capacity for raw semi-cokes are very low, the hydrothermal method, HNO3 oxidation and heat treatment modification of the activated semi-cokes all can increase the H2S removal efficiency and capacity, that is, firstly, activated semi-coke treated by the hydrothermal method under high pressure. Secondly, activated semi-coke treated by HNO3 oxidation for half and an hour, then water cleaning and drying. Thirdly, it is calcined for half and an hour at 720℃, the atmosphere of 1%O2, 45%H2O and the rest of nitrogen. With this method the best desulfuring agent P270HN45NOHO720 with higher sulfur capacity and longer breakthrough time is prepared. The optimal conditions of H2S removal by activated semi-coke are desulfurization temperature 75℃, H2O content of 8-10%, O2 content from3% to 5%, and space velocity of 900h-1. The desulfurization reaction is controlled by diffusion at space velocity lower than 900h-1, while it is controlled by surface reaction at space velocity higher than 900h-1.The relationship between desulfurization property of different activated semi-coke and their physical parameters is analyzed. It is found that the activated semi-coke with high content of basic functional groups shows pretty well performance for H2S removal, but the desulfurizing capacity has no linear relationship with the content of basic groups. The activated semi-coke with large specific surface area shows desirable performance for H2S removal, but the desulfurizing capacity has no linear relationship to the specific surface area. The specific surface area of activated semi-coke is not the key factor for desulfurizing activity. XRD analyses indicate that there is CuO on the surface of desulfurizer which is prepared by dipping Cu(NO3)2 solution containing 4% CuO, calcining at 550℃a nd 720℃, and there is CuS on the surface of the spent carbon.Two methods, solvent regeneration and gas regeneration, have been used for the spent activated semi-cokes which had removed H2S. The solvents utilized is HNO3, it shows that HNO3 can regenerate the activated carbon by oxidation. The gases utilized are N2, 20%O2 in N2, the principles of regenerated activated semi-coke are thermal regeneration, oxidation, respectively. The best results are found as 65%HNO3, 20%O2 in N2, respectively. They can remove sulfur from the pore canal of carbon up to 66.70% and 85.93% of the total during the first regeneration cycle.The principle of H2S removal by activated semi-coke and effect of different factors on desulfurization property are clearly seen through above research work. So it can accumulate basic data for further industrial application.更多还原