浆态床反应器中含氮合成气合成二甲醚的研究

Cu ZnO Al2O3甲醇合成催化剂和HZSM 5分子筛通过机械混合制备了合成气直接合成二甲醚催化剂,并在浆态床反应器中进行了含氮合成气制二甲醚的研究,考察了各种工艺条件对二甲醚合成性能的影响。结果表明:转子转速、原料气空速、反应压力和温度均对催化剂的反应性能有影响。采用浆态床反应器合成二甲醚,可实现等温操作并可使反应热及时移出,从而避免催化剂床层形成热点,使催化剂失活减缓,但CO转化率和二甲醚选择性相对较低。采用浆态床反应器与固定床反应器集成技术,不仅可以解决催化剂床层形成热点问题,还可得到90%的CO转化率和75%的二甲醚选择性,并使催化剂保持高的稳定性,二甲醚收率为68%。     

热处理对K_2MoO_4-P_(0.2)/SiO_2催化剂结构及性能的影响

采用等体积浸渍法制备了K2MoO4-P0.2/SiO2催化剂,通过XRD,TG,H2-TPR,XPS方法对催化剂进行了表征,考察了焙烧气氛、焙烧温度对催化剂表面结构及其催化性能的影响。实验结果表明,空气中焙烧的催化剂由于添加剂柠檬酸在焙烧过程中发生燃烧反应,造成局部过热,导致催化剂表面活性物种部分烧结长大,从而降低了催化剂的活性;而在氮气中焙烧的催化剂,由于柠檬酸缓慢分解且形成了还原性气氛,将易还原的Mo-O物种还原,形成了更多的活性Mo物种,且活性组分分散更均匀,从而表现出了比空气中焙烧的催化剂更高的活性。对于甲硫醇合成反应,后者的CO转化率提高约10%,甲硫醇选择性提高约7%。     

LaFeO3氧载体在乙烷化学链干重整中的性能评估

采用溶胶凝胶法制备了钙钛矿型氧化物LaFeO₃,在固定床上研究了反应温度和重时空速对氧载体在乙烷化学链干重整中性能的影响,以及氧载体的长周期循环性能．结果表明LaFeO₃氧载体可实现乙烷向合成气的高效转化,还原态的氧载体可以被CO₂氧化以实现其晶格氧的恢复,且表面积碳能被有效清除．反应最佳温度为800℃,此时CO产率最高(54.84%),最佳重时空速为12 000 L/(kg·h),CO选择性最高(60.16%)．在20次循环实验中,LaFeO₃氧载体的各项性能指标波动幅度较小,具有较好的反应稳定性．     

有效气体回收对造气岗位的意义浅议

介绍气量波动、紧张时,工艺方面的补救措施,包括调整变压吸附、提氢岗位指标,改变气柜高度,控制循环氢等手段。     

Steam gasification of bitumen oil in presence of Ni/dolomite catalysts

An important step in developing clean energy and reducing greenhouse gas emissions is the use of clean technologies such as gasification. In this work, we were used a bubbling fluidized bed (BFB) to convert the bitumen oil into a clean syngas in presence of three kinds of Ni/dolomite catalysts. While all three catalysts were acceptable in the process of tar elimination, but DN-22 was more successful in eliminating tar than the other two samples, which might be due to the higher amount of CaO in the composition DN-22. With increase in Ni, the amount of eliminated tars in the tar cracking process was also increased due to the delay in the deactivation of the dolomite catalyst.     

Dynamic Matrix Control of a Bubble‐Column Reactor for Microbial Synthesis Gas Fermentation

A spatiotemporal metabolic model of a representative syngas bubble‐column reactor was applied to design and evaluate dynamic matrix control (DMC) schemes for regulation of the desired by‐product ethanol and the undesired by‐product acetate. This model was used to develop linear step response models for controller design and also served as the process in closed‐loop simulations. A 2 × 2 DMC scheme with manipulation of the liquid and gas feed flows to the column provided a superior performance to proportional integral (PI) control due to slow process dynamics combining the multivariable and constrained nature of the control problem. Ethanol concentration control for large disturbances was further improved by adding the flow of a pure hydrogen stream as a third manipulated variable. The advantages of DMC for syngas bubble‐column reactor control are demonstrated and a design strategy for future industrial applications is provided.     

The Effect of Additives on Cu/HZSM-5 Catalyst for DME Synthesis

The addition of ZnO or ZrO₂ into CuO/HZSM-5 was investigated for DME synthesis from syngas by using the reactive frontal chromatography method, TPR and in situ TPR. These promoters enhanced the catalytic activity of Cu/HZSM-5 and promotion with ZnO and ZrO₂ produced a maximum activity, which could be explained by the improvement of the dispersion of Cu and the promotion of CuO reduction. The Cu⁺ species existing during the reaction have been detected, based on which a Cu⁰ Cu⁺¹ redox cycle model was put forward.     

Partial Oxidation of Methane to Syngas over Monolithic Ni/γ-Al2O3 Catalyst——Effects of Rare Earths and Other Basic Promoters

A series of monolithic Ni/γ-Al2O3 catalysts with and without basic promoters (Na, Sr, La, Ce) were prepared. Partial oxidation of methane (POM) to syngas was carried out in a continuous-flow, fixed-bed reactor. The influences of reaction conditions, including temperature, CH4/O2 ratio and space velocity, on the performance of the catalyst were investigated. The results show that at a high space velocity of 1×105 h-1, optimal CH4 conversion can be obtained. Effects of promoters such as Na, Sr, Ce, La were also investigated, and the catalyst samples were characterized by means of temperature-programmed reduction and XRD techniques. XRD suggests that the addition of promoters has no influence on the crystal structure of Ni/γ-Al2O3 catalyst. The results show that the addition of a small amount of promoters improves the reducibility and activity of the catalyst. The side reaction CH4 2 O2→CO2 H2O, is fully restrained and 100% H2 selectivity is achieved when Ce and La are used as promoters, respectively.     

Carbon Dioxide Reforming of Methane Over Nanocomposite Ni/ZrO2 Catalysts

A systematic study of the size effect of zirconia nanocrystals on nickel-catalyzed reforming of methane with CO₂ shows that extremely stable Ni/ZrO₂ catalysts are obtainable by hydrogen reduction of impregnated nickel nitrate on zirconia particles with sizes less than 25 nm. The same preparation method with larger particles of zirconia results in catalyst samples that deactivate rapidly in the reforming reaction. Comprehensive characterization with XRD, TPR/TPD, and TEM shows that the stable Ni/ZrO₂ catalysts are better described as nanocomposites of size comparable to Ni metal (9-15 nm) and zirconia (7-25 nm) nanoparticles. The high percentage of the Ni-zirconia boundary or perimeter in the nanocomposite catalysts is believed to be crucial for the extremely stable catalytic activity.     

Infrared studies of reaction of ethylene with syngas on Ni/SiO2

Ni/SiO₂, a methanation catalyst, has been shown to exhibit CO insertion activity. In situ infrared studies of CO/H₂ and C₂H₄/CO/H₂ reactions on Ni/SiO₂ show that carbonylation of Ni/SiO₂ to Ni(CO)₄ leads to an inhibition of methanation in CO hydrogenation but an enhancement of formation of propionaldehyde in the C₂H₄/CO/H₂ reaction.