甲烷干气重整（Ni/MgAl2O4）@SiO2催化剂的制备及抗积碳性能研究

采用烷基偶联剂水解法制备（Ni/MgAl₂O₄）@SiO₂催化剂,探究Ni、SiO₂质量分数对催化剂的甲烷干气重整（DRM）反应活性和抗积碳性能的影响。在常压、750℃、V（CH₄）∶V（CO₂）∶V（N₂）=5∶5∶1、GHSV=26 400 mL/(g_cat·h)条件下进行DRM反应,（10Ni/MgAl₂O₄）@5SiO₂催化剂表现出最好的反应性能,CH₄转化率为77%,CO₂转化率为90%。通过TEM、SEM等表征发现,SiO₂可以包覆在Ni/MgAl₂O₄催化剂表面,阻碍Ni晶粒团聚,增大催化剂的抗积碳性能。将该催化剂在严苛条件[V（CH₄）∶V（CO₂）∶V（N₂...     

催化剂颗粒形状对甲烷水蒸气重整反应的影响及工业反应器模拟

甲烷水蒸气重整工艺是现阶段最主要的工业制氢技术,催化剂颗粒形状和反应器操作条件是影响重整反应器性能和产物组成的重要因素。首先从颗粒尺度研究催化剂形状对甲烷水蒸气重整反应的影响,在不同的反应温度和压力下,计算并比较了球形、柱形和环形催化剂的效率因子,其大小顺序为:柱形 < 球形 < 环形。其次,将反应器床层的质量、热量和动量传递与环形催化剂颗粒的扩散-反应方程相结合,建立了用于描述甲烷水蒸气重整工业反应器的一维轴向数学模型。计算并分析了反应器进口温度和压力对反应器床层的温度和压力分布、催化剂效率因子以及甲烷转化率和各组分浓度分布的影响,确定了适宜的工业反应器进口温度和压力,分别为773 K和3 MPa。     

甲烷二氧化碳重整镍基催化剂的研究

采用浸渍法制备不同组成催化剂Ni-M/γ-Al₂O₃（M=Zr、Co、Mg、Nd）,通过固定床反应装置考察不同助剂、助剂含量和反应温度对催化剂活性的影响,并对催化剂进行X射线衍射表征。结果表明,14Ni-5Mg/γ-Al₂O₃的催化活性较好,随着反应温度的升高,甲烷转化率和CO收率均升高,反应温度升至800 ℃时,甲烷转化率达97.54%。采用共沉淀法制备载体、浸渍法制备的催化剂14Ni/MgO-Al₂O₃,在反应温度800 ℃、压力1.013 kPa、n(CO₂)∶n(CH₄)=1.2和催化剂用量0.5 g条件下,CO收率高于14Ni-5Mg/γ-Al₂O₃催化剂,但甲烷转化率略低。     

Si掺杂对Cu/ZrO2催化CO2加氢制甲醇性能的影响

为了提高Cu/ZrO₂催化剂在二氧化碳加氢制甲醇中的催化活性,制备了一系列不同Si/Zr的Si-ZrO₂载体并负载5%（质量分数）Cu得到了Cu/Si-ZrO₂催化剂。对所制备的催化剂进行了X射线衍射（XRD）、N₂物理吸脱附（BET）、X射线光电子能谱（XPS）、氢气程序升温还原（H₂-TPR）、二氧化碳程序升温脱附（CO₂-TPD）及高分辨透射电子显微镜 （HRTEM） 的表征。结果表明,Si的掺杂使得Cu/ZrO₂体系获得了稳定的晶相,大的比表面积和更多的碱性位点,尤其是中强碱性位点,同时产生了更多的氧空位,促进了CO₂的吸附和转化,因此得到了更高活性的催化剂。当Si与Zr的摩尔比为0.2时,在质量空速为6000 ml·g^-1·h^-1,温度为220℃、压力为3.0 MPa,V（H₂）∶V（CO₂）=3∶1（体积比）条件下,催化剂的CO₂转化率为4.6%,CH₃OH选择性为85%。     

Si掺杂对Cu/ZrO2催化CO2加氢制甲醇性能的影响

为了提高Cu/ZrO₂催化剂在二氧化碳加氢制甲醇中的催化活性,制备了一系列不同Si/Zr的Si-ZrO₂载体并负载5%（质量分数）Cu得到了Cu/Si-ZrO₂催化剂。对所制备的催化剂进行了X射线衍射（XRD）、N₂物理吸脱附（BET）、X射线光电子能谱（XPS）、氢气程序升温还原（H₂-TPR）、二氧化碳程序升温脱附（CO₂-TPD）及高分辨透射电子显微镜 （HRTEM） 的表征。结果表明,Si的掺杂使得Cu/ZrO₂体系获得了稳定的晶相,大的比表面积和更多的碱性位点,尤其是中强碱性位点,同时产生了更多的氧空位,促进了CO₂的吸附和转化,因此得到了更高活性的催化剂。当Si与Zr的摩尔比为0.2时,在质量空速为6000 ml·g^-1·h^-1,温度为220℃、压力为3.0 MPa,V（H₂）∶V（CO₂）=3∶1（体积比）条件下,催化剂的CO₂转化率为4.6%,CH₃OH选择性为85%。     

Cr/SSZ-13催化二氧化碳氧化乙烷脱氢反应的研究

通过脱氢反应将低碳烷烃转化为同碳数的烯烃是烷烃高值化利用和烯烃原料多元化的重要途径。烷烃氧化脱氢制烯烃的反应具有不受反应平衡限制、积炭少、反应温度低等优点,一直是研究的热点。通过利用浸渍法制备不同铬（Cr）负载量的Cr_x/SSZ-13系列催化剂,采用氮气物理吸附、氨程序升温脱附（NH₃-TPD）、二氧化碳程序升温脱附（CO₂-TPD）、氢气程序升温还原（H₂-TPR）、紫外-可见吸收光谱（UV-Vis）以及高角度环形暗场-扫描透射电镜（HAADF-STEM）与耦合能谱分析（EDX-Mapping）等方法对催化剂进行了物性表征,并用微型固定床反应器评价催化剂对乙烷氧化脱氢制乙烯的催化性能,最终建立了Cr/SSZ-13催化剂的构效关系。研究发现,当n（二氧化硅）/n（氧化铝）=10时,Cr_1.5/SSZ-13-10催化剂上含有丰富的Cr³⁺物种,其中配位不饱和Cr³⁺是优异的脱氢活性位,有利于二氧化碳氧化乙烷脱氢反应的进行。因此,Cr_1.5/SSZ-13催化剂在650 ℃时表现出优异的催化性能,即二氧化碳转化率和乙烷转化率分别达到26.41%和53.2%,乙烯产率为38.83%。     

焙烧温度对MnZnOx物化性质及催化性能的影响

采用湿化学共沉淀法制备了MnZnO_x固溶结构催化剂,考察了焙烧温度对催化剂物化性质和催化性能的影响。采用X射线衍射（XRD）、X射线光电子能谱（XPS）、N₂吸附-脱附、CO₂-TPD（程序升温脱附）及H₂-TPR（程序升温还原）等手段对不同焙烧温度下催化剂物化性质进行了分析表征。结果表明,焙烧温度对MnZnO_x晶相组成、孔结构性质、二氧化碳吸附特性及表面氧空位浓度等物化性质影响较大。500 ℃焙烧条件下制得的MnZnO_x催化剂形成了具有丰富的表面氧空位、较大的二氧化碳吸附量和介孔孔容且溶质组分分散均匀的固溶结构。在反应压力为3.0 MPa、反应空速（GHSV）为14 400 mL/（g·h）、V（氢气）∶V（二氧化碳）∶V（氮气）=72∶24∶4条件下,MnZnO_x催化剂于380 ℃表现出优异的催化性能,甲醇选择性为86.1%、二氧化碳转化率为16.0%、甲醇时空产率（STY）达0.68 g_MeOH /（h·g_cat）。     

CO2加氢制甲醇反应动力学及工艺能耗优化

为应对全球气候变暖等环境问题,碳捕集、利用和封存(CCUS)技术得到了越来越多的关注。CO₂加氢制甲醇既可以实现CO₂资源化利用,也可实现可再生能源的化学储存,是一种重要的CCUS技术。为探索优化CO₂加氢制甲醇的工艺,在固定床反应器中测试了商用Cu-ZnO/Al₂O₃催化剂在CO₂加氢制甲醇过程中的催化性能。探究了催化剂在448.15～543.15 K,1～3 MPa, H₂、CO₂物质的量比3～9的催化效果。结果表明,CO₂转化率随反应温度升高而增加;甲醇选择性主要受温度和氢碳物质的量比影响：温度越高甲醇选择性越低,氢碳物质的量比越大甲醇选择性越高;压力升高对CO₂转化率和甲醇选择性均有促进作用。以甲酸盐加氢步骤为反应的速率控制步骤,在LHHW动力学理论基础上推导建立了该催化剂用于CO₂加氢制甲醇的反应动力学模型,在MATLAB中构建模型优化函...     

Ni-CeO2-K/γ-Al2O3催化剂上沼气联合重整制合成气

采用超声波辅助等体积浸渍法制备Ni-CeO₂-K/γ-Al₂O₃催化剂用于沼气联合重整反应,采用 BET、XRD、TG/DTG等技术对催化剂性质进行了表征,在微型固定床反应装置中研究了反应温度、体积空速、原料气组成等对沼气联合重整反应特性的影响,并对催化剂的稳定性进行了研究。结果表明,助剂CeO₂的加入,提高了催化剂中Ni的分散度,降低了催化剂还原温度。升高反应温度和减小体积空速,能够提高沼气中CH₄和CO₂的转化率;原料气中加入水蒸气,能够明显提高H₂/CO体积比;加入的O₂容易与H₂、CO发生反应,CH₄转化率稍有提高。在常压、反应温度850℃、体积空速为100000h^-1、摩尔比CH₄∶CO₂∶H₂O∶O₂∶Ar=1∶0.5∶0.5∶0.1∶0.01的优化条件下,沼气中CH₄转化率超过95%,CO₂转化率超过75%,生成合成气H₂/CO体积比约为1.6,反应48h后,催化剂未见积炭,保持稳定的活性。与沼气干重整相比,沼气联合重整不利于沼气中CO₂的转化。     

H2O2/乙腈体系下MgO催化环己酮Baeyer-Villiger绿色氧化合成ε-己内酯的研究

在H₂O₂/乙腈体系下以沉淀法制备的MgO为催化剂催化Baeyer-Villiger（B-V）氧化环己酮合成ε-己内酯,考察了制备条件和反应条件对环己酮转化率和己内酯收率的影响。根据实验结果,Mg(NO₃)₂·6H₂O为前体,在煅烧温度为600℃、煅烧时间为2 h时制备MgO氧化性能最佳,由X射线衍射（XRD）、扫描电镜（SEM）进行了分析,可知随温度升高MgO粒径逐渐增大,500~800℃范围内,MgO晶粒尺寸由9.53 nm增大到29.49 nm。在n（催化剂）∶n（环己酮）=0.45∶1、n（乙腈）∶n（环己酮）=12∶1、n（双氧水）∶n（环己酮）=10∶1、70℃、6 h时获得环己酮转化率95.2%及ε-己内酯收率83.1%。对双氧水B-V氧化环己酮机理进行了深入的研究,采用在线原位红外光谱对反应进行实时监测与分析,验证了其过氧缩酰胺反应路径。     

Numerical simulation of fixed bed reactor for oxidative coupling of methane over monolithic catalyst

A three-dimensional geometric modelwas set up for the oxidative coupling of methane (OCM) fixed bed reactor loaded with Na₃PO₄-Mn/SiO₂/cordierite monolithic catalyst, and an improved Stansch kinetic model was established to calculate the OCMreactions using the computational fluid dynamicsmethod and Fluent software. The simulation conditions were completely the same with the experimental conditions that the volume velocity of the reactant is 80 ml·min^-1 under standard state, the CH₄/O₂ ratio is 3 and the temperature and pressure is 800 ℃ and 1 atm, respectively. The contour of the characteristic parameters in the catalyst bed was analyzed, such as the species mass fractions, temperature, the heat flux on side wall surface, pressure, fluid density and velocity. The results showed that the calculated valuesmatchedwell with the experimental values on the conversion of CH₄ and the selectivity of products (C₂H₆, C₂H₄, CO,CO₂ and H₂) in the reactor outlet with an error range of ±4%. The mass fractions of CH₄ and O₂ decreased from 0.600 and 0.400 at the catalyst bed inlet to 0.445 and 0.120 at the outlet, where the mass fractions of C₂H₆, C₂H₄, CO and CO₂ were 0.0245, 0.0460, 0.0537 and 0.116, respectively. Due to the existence of laminar boundary layer, the mass fraction contours of each species bent upwards in the vicinity of the boundary layer. The volume of OCM reaction was changing with the proceeding of reaction, and the total moles of products were greater than reactants. The flow field in the catalyst bed maintained constant temperature and pressure. The fluid density decreased gradually from 2.28 kg·m^-3 at the inlet of the catalyst bed to 2.18 kg·m^-3 at the outlet of the catalyst bed, while the average velocity magnitude increased from 0.108 m·s^-1 to 0.120 m·s^-1.     

耦合传质的羰基化固定床反应器传热模拟分析

固定床反应器中进行强放热反应时, 反应器的热点温度对操作参数变化敏感,容易引起飞温,导致转化率下降,影响催化剂寿命。为强化羰基化固定床反应器内热质传递与化学反应的协同性,建立考虑颗粒内扩散影响的羰基化固定床反应器拟均相一维传热模型,考察操作参数对床层热点温度、反应转化率、床层温升的影响。不仅体现传热传质和反应的协同作用,而且影响关系明晰、求解方便。为保证反应转化率,本实验条件下确定催化剂颗粒直径小于等于1.5 mm。反应器入口温度/冷却剂油温既要满足床层热稳定性需求,又要使反应转化率和床层温升都在合理范围内。模拟结果表明在床层入口温度升高的同时,可通过降低冷却剂油温获得良好的反应转化率和较小的床层温升。在此基础上,考察入口环氧乙烷浓度对反应转化率和床层温升的影响。本研究可为固定床反应器满足转化率要求、床层合理温升而选择催化剂颗粒直径、床层入口温度、冷却剂油温和床层入口浓度等操作参数提供计算依据。     

工艺条件对甲醇脱水制二甲醚反应的影响

以La改性氧化铝为催化剂,在模拟绝热固定床反应器中考察工艺条件对甲醇气相脱水制二甲醚反应的影响。结果表明,甲醇进料温度210℃时,甲醇脱水反应剧烈,绝热温升约130℃。催化剂床层热点温度低于380℃时,二甲醚选择性大于98%,过高温度产生大量副产物甲烷。反应压力对反应影响甚微。在甲醇进料温度240℃(热点温度370℃)、甲醇进料空速1.5 h-1和反应系统压力为50 k Pa条件下,甲醇转化率大于84%,二甲醚选择性大于98.5%,连续运转2 000 h,催化剂无明显失活迹象。     

Performance of catalytic reactors for the hydrogenation of CO2 to hydrocarbons

Fluidized bed and slurry reactors were employed to increase the CO₂ conversion and desirable product selectivity in the direct hydrogenation of CO₂ to hydrocarbons over K-promoted iron catalysts, as it is beneficial for the removal of heat generated due to highly exothermic nature of the reaction. The iron catalysts (Fe-K/Al₂O₃ and Fe-Cu-Al-K) were characterized by BET surface area, CO₂ and H₂ chemisorption, temperature-programmed reduction (TPR), X-ray diffraction (XRD) and temperature-programmed hydrogenation (TPH). The results of TPR and TPH study clearly indicated that co-precipitated Fe-Cu-Al-K catalyst has much higher reducibility and catalytic activity of CO₂ hydrogenation at low temperature than Fe-K/Al₂O₃. The performance of fluidized bed or slurry reactors was superior to that of fixed bed reactor for the CO₂ hydrogenation over Fe-Cu-Al-K catalyst in terms of CO₂ conversion and hydrocarbon productivity. Moreover, light olefins and heavy hydrocarbons were selectively synthesized in fluidized bed and slurry reactors, respectively. The optimum operation conditions and the effects of operating variables on the CO₂ conversion and its product distribution in these catalytic reactors were also discussed.     

A two-stage catalyst bed concept for conversion of carbon dioxide into methanol

Conversion of CO₂ into methanol by catalytic hydrogenation has been recognized as one of the most promising processes for stabilizing the atmospheric CO₂ level, and furthermore the methanol produced could be used as fuel or basic chemical for satisfying the large demand world-wide. The present work investigates a two-stage catalyst bed concept for conversion of CO₂ to methanol. A system with two catalyst beds instead of one single catalyst bed is developed for conversion of CO₂ to methanol. In the first catalyst bed, the synthesis gas is partly converted to methanol in a conventional water-cooled reactor. This bed operates at higher than normal operating temperature and at high yield. In the second bed, the reaction heat is used to pre-heat the feed gas to the first bed. The continuously reduced temperature in this bed provides increasing thermodynamic equilibrium potential. In this bed, the reaction rate is much lower and, consequently, so is the amount of the reaction heat. This feature results in milder temperature profiles in the second bed because less heat is liberated compared to the first bed. In this way the catalysts are exposed to less extreme temperatures and, catalyst deactivation via sintering is circumvented. In this work, a one-dimensional dynamic plug flow dynamic is used to analyze and compare the performance of two-stage bed and conventional single bed reactors. The results of this work show that the two-stage catalyst bed system can be operated with higher conversion and longer catalyst life time.     

Si含量对CO_2加氢制烃铁基催化剂的影响

以湿固相研磨法制备不同硅含量的铁基催化剂,采用X射线衍射、H2程序升温还原和傅里叶红外光谱对催化剂进行表征,在V(H_2)∶V(CO_2)∶V(N_2)=16∶8∶1、反应压力1.6 MPa、反应温度230℃、反应时间48 h和空速6 000 m L·(h·g-cat)-1条件下,在固定床反应器中考察催化剂的CO_2加氢制烃反应活性和烃类选择性。结果表明,随着Si O_2掺入量增加,催化剂的还原性能降低,结晶度呈下降趋势,CO_2转化率下降,但C5+烃类产物选择性在硅含量为10%时达到最大,为38.6%。     

K2CO3对兰炭催化气化特性的影响

在固定床中考察了不同K₂CO₃植入浓度和不同温度条件下兰炭催化气化特性。结果表明，5%的催化剂植入浓度主要起到填充孔隙的作用，当植入浓度增加到10%以后，催化剂发生堆积会使颗粒表面及内部形成较多孔隙。提高气化温度可提高兰炭转化率，超过750℃之后碳转化率增幅减缓，催化剂饱和装载浓度为10%。在颗粒表面和开放孔隙中的高浓度C(O)才具有较高的脱附速率，并提高CO生成速率。在非催化条件下，随着气化的进行CO/CO₂下降，而H₂/(2CO₂+CO)先增后减。在催化条件下，H₂/(2CO₂+CO)稳定在1.5～1.7。催化剂兰炭样品中出现了K₂Ca(CO₃)₂双金属碳酸盐、K₂O、KO₂等活性组分，并随催化剂植入浓度的增加而增加。催化剂植入浓度的增加会导致失活现象加重，但兰炭在750℃条件下气化1 h 催化剂没有完全失活。     

Performance characteristics of fluidized bed syngas methanation over Ni-Mg/Al2O3 catalyst

The performance characteristics of isothermal fluidized bed syngas methanation for substitute natural gas are investigated over a self-made Ni–Mg/Al2O3 catalyst. Via atmospheric methanation in a laboratory fluidized bed reactor it was clarified that the CO conversion varied in 5% when changing the space velocity in 40–120 L·g?1·h?1 but the conversion increased obviously by raising the superficial gas velocity from 4 to 12.4 cm·s?1. The temperature at 823 K is suitable for syngas methanation while obvious deposition of uneasy-oxidizing Cγoccurs on the catalyst at temperatures around 873 K. From a kinetic aspect, the lowest reaction temperature is suggested to be 750 K when the space velocity is 60 L·g?1·h?1. Raising the H2/CO ratio of the syngas increased proportionally the CO conversion and CH4 selectivity, showing that at enough high H2/CO ratios the active sites on the catalyst are sufficient for CO adsorption and in turn the reaction with H2 for forming CH4. Introducing CO2 into the syngas feed suppresses the water gas shift and Boudouard reactions and thus increased H2 consumption. The ratio of CO2/CO in syngas should be better below 0.52 because varying the ratio from 0.52 to 0.92 resulted in negligible increases in the H2 conversion and CH4 selectivity but decreased the CH4 yield. Introducing steam into the feed gas affected little the CO conversion but decreased the selectivity to CH4. The tested Ni–Mg/Al2O3 catalyst manifested good stability in structure and activity even in syngas containing water vapor.     

Characterization and reactivity of pure TiO2–SO4 SCR catalyst: influence of SO4 content

The kinetics of the reaction of NO, N₂O and CO₂ with activated carbon without catalyst and impregnated with a precursor salt of vanadium (ammonium monovanadate) was investigated. The conversion of NO, N₂O and CO₂ was studied (450–900°C) using a TGA apparatus and a fixed bed reactor. The reactor effluents were analysed using a GC/MS on line. The addition of vanadium increased carbon reactivity and adsorption at lower temperatures. For NO and N₂O conversion the main products obtained were N₂, N₂O, CO and CO₂ but for CO₂ conversion only CO was detected. In situ XRD was a useful tool for interpreting catalyst behaviour and identifying phases present during reaction conditions. The catalytic effect of vanadium can be explained by the occurrence of redox processes in which the catalyst is reduced to lower oxidation states such as V₂O₅/V₆O₁₃.