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2024年 第52卷  第5期

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摘要:
褐煤碳含量高且富含氧、氮等杂原子,是制备炭材料的重要原料。但由于褐煤可溶有机碳含量低,杂原子分配无规律,导致以褐煤为原料制备炭材料面临诸多挑战。因此,亟需实现褐煤的可溶化转化。本研究以氨水为溶剂,旨在温和条件下,同步实现昭通褐煤的可溶化和褐煤热溶物中氧和氮的调控。实验结果表明,在氨水质量分数15%、温度160 ℃条件下反应3 h,热溶物收率最高为76.66%,昭通褐煤表现出良好的热溶效果。基于对热溶物的表征和分析,发现氨解在一定程度上改变了煤中的大分子结构,表现为氨基与羟基置换,或与部分羧基、羰基直接反应生成有机态氮。对比发现,原煤中氮元素赋存形态以季氮和吡咯氮为主,而可溶物中氮元素赋存形态以氨基氮和吡啶氮为主,表明褐煤氨解热溶过程产生了氨基或酰胺基。
摘要:
煤气化细渣是煤炭清洁高效利用的副产物之一,其资源化应用迫在眉睫。通过简单筛分得到固定碳含量高于60%的高炭组分,并以此为原料,采用超声酸浸法制备多孔材料。以核废水中放射性碘的吸附处理为应用背景,用碘吸附值表征多孔材料的吸附性能。结合SEM、BET、XRD和FT-IR等性质和结构分析方法,系统研究了超声时间、超声功率、酸浓度和温度对多孔材料碘吸附性能和组成结构的影响规律;并探讨了超声强化酸浸对残炭的组成结构的影响机制和灰成分的迁移转化规律,总结出超声强化酸浸作用机理。结果表明,煤气化细渣高炭组分在酸浓度为4 mol/L、酸浸温度为50 ℃、超声功率为210 W,超声时间1.5 h的条件下,所制备多孔材料的碘吸附性能最佳,为468.53 mg/g,比表面积达到474.97 m2/g,且具有以介孔为主的丰富孔隙结构。各因素对多孔材料碘吸附性能影响的顺序为:超声时间>酸浓度>超声功率>酸浸温度。超声强化酸浸作用机理是超声空化和机械波作用一方面强化炭灰黏附颗粒的解离,使堵塞在气化细渣孔道内的灰颗粒脱附,增加孔隙结构的连通性;其次,会导致炭灰颗粒表面裂纹的产生,增强碳颗粒内部无机组分的可及性;第三,能够提高酸浸过程的传质速率,强化气化细渣中的无机组分的浸出效果。
摘要:
通过简单加热乙二醇,对甲苯磺酸和八水氯氧化锆混合物制备了三元低共熔溶剂。采用傅里叶变换红外光谱(FT-IR)和核磁共振氢谱(1H NMR)验证了低共熔溶剂成功合成。分别采用紫外-可见吸收光谱和旋转式黏度计对其酸性和黏度进行测试。以双氧水作为氧化剂,以合成的低共熔溶剂为萃取剂和催化剂构成萃取-氧化脱硫系统,考察了低共熔溶剂的组成、反应温度、氧硫比、剂油比以及不同硫化物等对脱硫率的影响。实验结果表明,在氯氧化锆、乙二醇和对苯甲磺酸物质的量比为1∶10∶10,反应温度50 ℃、剂油比为1∶5、氧硫比为8的最佳反应条件下,二苯并噻吩(DBT)、4,6-二甲基二苯并噻吩(4,6-DMDBT)、苯并噻吩(BT)模拟油的脱硫率分别为100%、92.2%、60%,且低共熔溶剂重复使用五次后脱硫率仍可达到96.2%,最后对氧化脱硫的机理进行了探讨。
摘要:
以Co基催化剂耦合沸石分子筛催化剂应用于合成气催化转化可以有效改善催化剂的产物选择性。本研究通过浸渍法制备得到Zr/Al2O3载体和Pt/ZSM-5催化剂,再通过超声分散法制备了Co/Al2O3、Co/Zr/Al2O3和Co/Zr/Al2O3-Pt/ZSM-5催化剂。通过系列表征技术对载体和催化剂理化性质进行分析,评价了催化剂费-托合成反应性能。结果表明,Zr的引入有助于提升Co/Zr/Al2O3上Co物种的还原性,改善催化活性,增加C12+重质烃的选择性。当Co/Zr/Al2O3与Pt/ZSM-5耦合后,由于贵金属Pt的助剂效应,进一步促进Co物种的还原,Co/Zr/Al2O3-Pt/ZSM-5催化剂的CTY值提高至8.3×10−5 mmol/(g·s),同时具有较低的CH4、C2−C4产物选择性。此外,Pt/ZSM-5的酸性促进C12+产物的部分裂解,使产物分布向C5−C11液态烃偏移,C5−C11产物选择性达到45.9%。本研究为设计和制备高效的费-托合成催化剂提供了参考。
摘要:
A series of spinel catalysts, including ZnFe2O4, MgFe2O4, CuFe2O4, and MnFe2O4, were prepared and applied to the Fischer-Tropsch synthesis (FTS). Zn, Mg, Cu and Mn easily form spinels with Fe. Among them, Zn and Mg can significantly maintain the spinel structure during the pretreatment and reaction, resulting in a low CO conversion. Cu and Mn are beneficial to the formation of iron carbide during the reaction, resulting in an apparent influence on FTS performance. ZnFe2O4 has little effect on the hydrocarbon distribution and the olefin/paraffin (O/P) ratio of C2−C4. MgFe2O4 exhibits low selectivity for C5+ hydrocarbons, and the selectivity of $ {\mathrm{C}}_2^=-{\mathrm{C}}_4^=\;$ and the O/P ratio of C2−C4 in the product are increased due to the alkaline effect of Mg. Cu can promote the carbonization of the catalyst, so that CuFe2O4 has higher activity. Meanwhile, CuFe2O4 can significantly improve the selectivity of C5+ hydrocarbons. Moreover, Cu can promote the dissociation and activation of H2, which is beneficial to the secondary hydrogenation of olefins, thereby reducing the selectivity of $ {\mathrm{C}}_2^=-{\mathrm{C}}_4^=\;$ and the O/P ratio of C2−C4. Mn promotes carbonization during the reaction, but MnFe2O4 has little effect on the chain growth of hydrocarbon. However, Mn can promote the generation of a certain amount of ε-Fe2C, which may explain the higher selectivity of $ {\mathrm{C}}_2^=-{\mathrm{C}}_4^=\;$ and the O/P ratio of C2−C4 for MnFe2O4. All spinel catalysts exhibit low CO2 selectivity, which meets the current green environmental protection requirements.
摘要:
Phenolic derivatives, crucial components of bio-oil, require thorough understanding of their electrocatalytic hydrogenation (ECH) properties for efficient bio-oil utilization. This study investigated guaiacol, a representative phenolic derivative in bio-oil, focusing on its ECH mechanism, conversion, and product selectivity under varied conditions (temperature: 40−80 °C, perchloric acid concentration: 0.2−1.0 mol/L, current intensity: ((−10)−(−150) mA). Additionally, this study also explored the influence of intermediate products (2-methoxycyclohexanone and cyclohexanone) on both the conversion rate and the selectivity of the products. The experiment had revealed that guaiacol's ECH conversion rate improved with higher temperature and current intensity, whereas an increase in perchloric acid concentration negatively affected the conversion. Significantly, the presence of intermediate products, especially 2-methoxycyclohexanone, markedly enhanced the ECH conversion of guaiacol. Investigating further into the ECH mechanism of other phenolic derivatives, including phenol, pyrocatechol, guaiacol eugenol, and vanillin, as well as their combination, revealed a trend where conversion rates inversely correlated with the complexity of the functional groups on the benzene ring. Specifically, phenol, with its simpler structure, showed the highest conversion rate at 89.34%, in stark contrast to vanillin which, owing to its more complex structure, exhibited the lowest at 46.79%. In our multi-component mixture studies, it was observed that synergistic and competitive interactions significantly alter ECH conversion rates, with some mixtures showing enhanced conversion rate indicative of synergistic effects.
摘要:
The TiO2 nanotubes arrays/SnO2-Sb (TNTs/SnO2-Sb) electrode is successfully fabricated using the solvothermal synthesis technique. Various architectures of TNTs are constructed by varying the anodization voltage and time, aiming to investigate their impact on the structural and electrochemical properties of the SnO2-Sb electrode. The anodization voltage is identified as the primary influencing factor on the morphology and surface hydrophilia of TNTs arrays, which is evidenced by scanning electron microscopy (SEM) and contact angle testing. In contrast, the effect of anodization time is relatively small. SEM, X-ray diffraction (XRD), linear sweep voltammograms (LSV), and electrochemical impedance spectroscopy (EIS) results indicate that the morphology and crystal size of the catalytic coating, as well as the oxygen evolution potential of the electrode, are influenced by the pore size of TNTs arrays. The influencing mechanism of enhanced electrochemical activity by adjusting the architecture of TNTs arrays is investigated using X-ray photoelectron spectroscopy (XPS), electron paramagnetic resonance (EPR), and hydroxyl radicals (·OH) generation test. The results reveal a higher concentration of oxygen vacancies on the sample with a compact and smaller particle coating, indicating the presence of more adsorbed oxygen species. Consequently, this enhances the generation capacity of active radicals for organic matter degradation. The electrode featuring TNTs arrays with a length of 950 nm and a pore diameter of 100 nm exhibits the most effective remediation of phenol-containing wastewater, achieving approximately 92% ± 4.6% removal after a duration of 2 h.
摘要:
Cu2O具有禁带窄、环境友好和储量丰富等优点,是一种理想的可见光催化剂,然而其光生载流子复合率高和稳定性差等问题限制了Cu2O在光催化领域的实际应用。为此,本文采用光诱导原位技术,以甲醇为碳源、硫酸铜为铜源,一步成功制备了超薄炭壳层包覆的Cu2O复合纳米材料(Cu2O@C)。结果显示,与常规炭包覆方法相比,光诱导原位技术避免了苛刻的反应条件及繁琐的合成步骤对Cu2O半导体结构的破坏,有效保留了Cu2O本征电子结构,使其具有优异的光催化活性及稳定性。同时,Cu2O@C的核壳结构不仅可以钝化半导体表面缺陷和促进光生载流子的分离,而且炭壳层的包覆还可以避免Cu2O纳米颗粒与溶液的直接接触,有效抑制高活性反应中间体对催化剂结构的破坏。与单独的Cu2O纳米颗粒相比,Cu2O@C复合纳米材料在可见光下的光解水产氢活性和稳定性得到显著提高,产氢速率可达1.28 mmol/(g·h),且在连续五次循环稳定性测试中,氢气生成速率无明显变化。
摘要:
采用废弃的鸡蛋壳作载体,沉积沉淀法制备了一系列不同Co3O4含量Co3O4/鸡蛋壳催化剂,并在连续流动微反装置上考察了N2O分解性能。结果表明,当Co3O4质量分数为20%时,催化剂表现出优异的N2O分解性能。在空速10000 h−1和N2O含量0.1%的条件下,400 ℃可实现N2O完全转化;其比活性约为Co3O4催化剂的4.3倍(反应温度为440 ℃);同时,该催化剂对原料气中3% O2、3.3% H2O和/或2.0×10−4 NO表现出较强的耐受性和较高的稳定性。分析催化剂的多种表征结果发现,CaCO3作为鸡蛋壳的主要成分,与活性组分Co3O4紧密结合,两者的强相互作用导致20%Co3O4/鸡蛋壳催化剂中产生更多的氧空位和Co3+;Co3O4氧化还原性能得到提高,Co−O键被有效削弱;此外,该强相互作用可提高20%Co3O4/鸡蛋壳催化剂表面碱性位点的强度,增大碱性位点数量,更易于转移电子而促进N2O分解。
摘要:
基于密度泛函理论和经典过渡态理论,探究了石墨炭负载单原子Fe催化剂(Fe/G)异相还原NO的微观机理,并对催化剂失活原因进行分析。结果表明,基于E-R机理,NO还原反应依次经历了N2O形成与释放、N2形成与释放四个阶段。而基于L-H机理,NO还原反应主要经历了N2形成与释放两个阶段。在E-R机理作用下,NO分子以N,O-down结构吸附在Fe原子上发生的NO还原反应的控速步骤能垒值仅为15.5 kJ/mol,小于其余路径控速步骤能垒值。由能垒角度分析,Fe原子上残留的活性氧被还原的能垒值高于NO还原生成N2的能垒值。NO分解后残留在Fe原子表面的活性氧抑制了NO的吸附与还原,Fe原子活性位的缺失导致催化剂的失活,单原子Fe的存在促进了NO还原反应的进行。由动力学角度分析,随着反应温度的升高,NO还原速率较活性氧转移速率提升更为显著。
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火焰喷雾热解法(FSP)是一种简单、快速、可规模化制备纳米催化剂的技术。通过火焰喷雾热解法合成CeO2和Pt-CeO2载体、Pd-Pt-CeO2催化剂,采用浸渍法在CeO2和Pt-CeO2载体分别沉积Pd-Pt和Pd而制得Pd-Pt双金属催化剂,并考察其甲烷催化燃烧性能。利用ICP、XRD、TEM、BET、H2-TPR、XPS和Raman对催化剂的物化性质进行分析。TEM结果表明,Pd-Pt/CeO2催化剂中Pd和Pt物种高分散于CeO2载体。相比于一步法(one step)制得的Pd-Pt-CeO2(OS-FSP)催化剂,共浸渍法制得Pd-Pt/CeO2(0.25)-WI的催化活性更高,其t50降低了60 ℃,且稳定运行60 h而没有明显失活。这归因于Pd-Pt/CeO2(0.25)-WI催化剂表面上Pd0/Pd2+和Ce3+/Ce4+物质的量比更高、晶格氧更多,进而导致其具有良好的甲烷催化燃烧性能。
摘要:
生物质基2,5-呋喃二甲醇(BHMF)可从廉价易得的糖类出发,经催化转化-选择性氢化制取,并作为一种用途广泛的化工中间体及燃料前体,尤其在改善传统聚酯性能以及合成绿色可降解的生物基聚酯新材料方面具有独特优势。BHMF制取过程中,传统的氢化方式消耗了大量高品位能源氢气,且高压氢气存在安全隐患并导致基础设施投入多。本工作立足于催化转移氢化的优势,综述了甲酸、醇类及其他类型氢供体通过催化转移氢化的方式选择性加氢制取BHMF的研究进展;并针对催化转移氢化过程中不同类型氢供体、催化剂和反应工艺的特点及存在的问题,分析了反应条件、强化手段等对BHMF选择性和收率的影响以及反应体系的优劣。在此基础上,提出了转移氢化制取BHMF新型催化体系的研究方向,并对清洁高效、本质安全BHMF制取工艺的发展进行了展望,为生物质转化中特定催化体系的研发提供科学参考。
摘要:
选择性催化还原技术(SCR)在水泥行业脱硝中被广泛应用,其中,高温范围内(280–350 ℃)已有较为完善的SCR技术及体系,但在中温区仍有待突破。本工作以中温脱硝催化剂为重点,综述了Mn、Ce、V系脱硝催化剂的研究进展,并分析了Sm、Nb、Ho、Sb、La、Mo、Pr的掺杂对于脱硝催化剂的改性,结合水泥窑炉烟尘中SO2、H2O、碱金属含量高的特点,分析了脱硝催化剂中毒原因,对催化剂的抗H2O、SO2、碱金属中毒性能进行了探讨,展望了水泥行业SCR中温脱硝催化剂的研究前景。