用于二甲醚水蒸气重整制氢的固体酸与金属催化剂研究

发布时间：2018-06-22 12:31

  本文选题：DME + SR　； 参考：《天津大学》2015年硕士论文

【摘要】：目前化石燃料的大量使用给我们带来了能源危机和各种各样的环境问题。因此,有必要寻求一种清洁的可再生能源。氢气作为一种新型的可再生能源越来越受到各国政府和研究者的关注。在过去的几年里,氢燃料电池,如质子交换膜燃料电池(PEMFCs),以其较高的能量转化效率成为国内外学者的研究热点。然而作为一种新型气态能源,氢气难以被储存、压缩和运输。这限制了氢燃料电池在车辆上的广泛应用。故发展在线制氢技术很有必要。二甲醚水蒸气重整(DME SR)制氢被认为是一种非常有前途的车载制氢路线。针对二甲醚水蒸气重整的特点,我们分别研究了P改性的HZSM-5固体酸催化剂和Cu基尖晶石甲醇水蒸气重整催化剂。采用浸渍法制备了不同P含量的P改性HZSM-5固体酸催化剂,详细研究了P改性对HZSM-5酸性及二甲醚水蒸气重整制氢活性的影响。与未改性的HZSM-5相比,P改性的HZSM-5催化剂(与CuZnAlO催化剂混合)在二甲醚水蒸气重整过程中表现出更高的CO_2选择性和更好的稳定性。通过N_2吸附-脱附、XRD、O_2-TPO、NH_3-TPD、pyridine-IR、~(31)P MAS NMR等技术对催化剂进行了表征。NH_3-TPD结果表明,P改性后HZSM-5催化剂的酸量和酸强度均发生了改变。结合~(31)P MAS NMR、NH_3-TPD及pyridine-IR结果,提出了P改性HZSM-5的可能的机理模型。通过柠檬酸辅助的溶胶-凝胶法制备了一系列铜基尖晶石催化剂(CuM_2O_4,M=Cr,Mn,Fe,Co,Al),并考察了铜基尖晶石催化剂与5%P/HZSM-5在二甲醚水蒸气重整中的耦合作用。发现在所有的尖晶石样品中,CuFe_2O_4催化剂具有最好的催化性能。XPS和XAFS结果表明,CuFe_2O_4催化剂具有最高的Cu~+/Cu比例,而Cu~+的存在有利于甲醇水蒸气重整反应中间物种HCOO-和COO-的形成,因此CuFe_2O_4催化剂具有更好的催化活性及CO_2选择性。此外,还研究了CuFe_2O_4催化剂与5%P/HZSM-5不同混合比例对二甲醚水蒸气重整反应性能的影响,发现混合质量比为1:1的催化剂在350 ℃时具有最好的催化活性。
[Abstract]:At present, the extensive use of fossil fuels has brought us energy crisis and various environmental problems. Therefore, it is necessary to seek a clean and renewable energy source. As a new type of renewable energy, hydrogen has been paid more and more attention by governments and researchers. In the past few years, hydrogen fuel cells, such as proton exchange membrane fuel cells (PEMFCs), have become a hot research area for their high energy conversion efficiency. However, as a new gaseous energy source, hydrogen is difficult to store, compress and transport. This limits the widespread use of hydrogen fuel cells in vehicles. Therefore, the development of online hydrogen production technology is very necessary. Dimethyl ether steam reforming (DME SR) is considered to be a promising vehicle hydrogen production route. According to the characteristics of dimethyl ether steam reforming, P-modified HZSM-5 solid acid catalyst and Cu-based spinel methanol steam reforming catalyst were studied respectively. P- modified HZSM-5 solid acid catalyst with different P content was prepared by impregnation method. The effect of P modification on HZSM-5 acid and dimethyl ether steam reforming activity was studied in detail. Compared with the unmodified HZSM-5, the modified HZSM-5 catalyst (mixed with CuZnAlO catalyst) showed higher CO-2 selectivity and better stability during the steam reforming of dimethyl ether. The results showed that the acid content and strength of the modified HZSM-5 catalyst had changed by means of N _ S _ 2 adsorption-desorption XRDO _ 2-TPOD _ 2-T _ P _ (2-TPOD) NH _ 3-TPO ~ (31) P MAS NMR technique. The results showed that the acid content and the acid strength of the modified HZSM-5 catalyst had changed. Based on the results of ~ (31) P-MAS NMR-NH3-TPD and pyridine-IR, a possible mechanism model of P-modified HZSM-5 was proposed. A series of Cu-Based spinel catalysts (CuM2O4MCrMnMnPCoCoAl) were prepared by citric acid-assisted sol-gel method. The coupling effect of Cu-based spinel catalyst and 5P- / HZSM-5 in the steam reforming of dimethyl ether was investigated. The results of XPS and XAFS showed that the CuFe2O4 catalyst had the highest Cu- / Cu ratio, and the presence of Cu- was beneficial to the formation of the intermediate species HCOO- and COO- in the steam reforming reaction of methanol, and the results of XPS and XAFS showed that the CuFe2O4 catalyst had the highest Cu / Cu ratio. Therefore, CuFe2O4 catalyst has better catalytic activity and COK2 selectivity. In addition, the effects of different mixing ratios of CuFe2O4 catalyst and 5P- / HZSM-5 on the performance of dimethyl ether steam reforming were studied. It was found that the catalyst with a mixture mass ratio of 1:1 had the best catalytic activity at 350 鈩，

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