Blautia coccoides GA-1的传代培养及其同化H_2/CO_2产乙酸特征

为了解同型产乙酸菌异养代谢与自养代谢的相互作用与机制,并为快速获得具有较强自养代谢能力的菌体细胞提供培养方法,以H_2/CO_2和(或)葡萄糖为碳源,考察了Blautia coccoides GA-1在连续传代培养中的代谢特征。结果表明,以H_2/CO_2作为唯一碳源进行连续传代培养时,菌株GA-1长势较弱,其子代的自养代谢能力也逐渐下降;在葡萄糖培养基中,菌株GA-1增殖旺盛,但高浓度的葡萄糖对其自养代谢能力有显著抑制作用,这种抑制作用可能是自养代谢和异养代谢对辅酶A和ATP的竞争、酸性环境造成的代谢抑制以及辅酶I的氧化还原平衡调节等综合作用的结果。以体积比为4:1的H_2/CO_2混合气为气相条件,用200 mg·L-1葡萄糖培养基对菌株GA-1进行传代培养,不仅可获得稳定的子代培养物,而且可以将其利用H_2/CO_2产乙酸的能力维持在2.16g乙酸·(g干细胞)-1的水平。     

温度对产甲烷菌代谢途径和优势菌群结构的影响

产甲烷菌是严格厌氧的古菌,由其完成的产甲烷过程通常是厌氧微生物生化代谢中最重要的限速步骤。温度作为影响产甲烷菌的产甲烷速率重要因素,其变化会改变生物环境中的产甲烷的代谢途径和优势菌群分布。目前已知甲烷生物合成有3条途径：乙酸代谢途径、CO₂还原途径和甲基营养型途径。理论上乙酸途径生成的甲烷约占甲烷生成总量的2/3,CO₂还原产甲烷途径则约占1/3,甲基营养型途径只在少数情况下考虑其影响,例如盐湖。在低温条件下产甲烷菌以利用乙酸代谢为主;在中温条件下,产甲烷途径以乙酸代谢和H₂/CO₂还原一定比例存在;在高温和超高温条件下,以只利用CO₂还原途径的菌群为主。     

代谢工程改造微生物固定二氧化碳研究进展

微生物固定CO₂是实现CO₂资源化利用的有效策略之一,为固碳减排、节能生产与绿色合成提供了借鉴。然而,微生物在固定CO₂过程中存在底物利用效率低、能量需求量大、路径难优化等问题。为了解决这些问题,本文总结了6种天然CO₂固定途径与5种人工CO₂固定途径,并从自养微生物、异养微生物和人工微生物三个方面系统分析了代谢工程改造微生物固定CO₂合成化学品的最新进展。在自养微生物固定CO₂方面,采用的策略主要包括提高CO₂固定途径效率、开发能量捕集系统与调节碳代谢流分布;在异养微生物固定CO₂方面,常用的方法主要有强化羧化途径、重构CO₂固定途径与优化能量供给;在人工微生物固定CO₂方面,主要的研究思路是设计人工CO₂固定途径与构建人工CO₂固定微生物。最后,从CO₂固定的关键酶、途径和微生物...     

低湿CO2/H2O混合气体吸附特性实验

CO₂捕集、封存及利用是实现“双碳”目标的重要途径,为将碳捕集后的低湿CO₂/H₂O进行CO₂提纯和资源化利用,采用动态吸附实验研究了不同温度（303K、313K）、H₂O含量（0.7%~3.0%）的CO₂/H₂O在活性炭、活性氧化铝、分子筛3A和13X四种吸附剂上的动态吸附穿透曲线、吸附床温度分布、吸附量,分析了CO₂/H₂O分离系数和吸附热。结果表明,在CO₂/H₂O动态吸附过程中,吸附床温度与各组分浓度随时间变化趋势相同。H₂O饱和时间随进气温度升高而缩短;H₂O含量增加,抑制CO₂吸附;活性炭和氧化铝中H₂O的饱和时间随H₂O含量增加而增长,但分子筛3A和13X饱和时间缩短。H₂O吸附量随H₂O含量增加而增加,吸附热随吸附量增加而减小,CO₂则相反。分子筛3A对CO₂吸附量最小且CO₂/H₂O分离系数最大。H₂O含量小于1%时,CO₂吸附量最大的分子筛13X分离系数大于活性氧化铝,分子筛3A和13X适合分离低湿CO₂/H₂O。     

氨水吸收CO2的吸收热预测模型

基于e-NRTL模型,利用Aspen Plus软件建立了氨水吸收CO₂的吸收热预测模型,验证了NH₃-CO₂-H₂O体系的汽液平衡、液相组成形态并与前人的实验数据做了对比,进而结合负载CO₂的氨水溶液中各离子及分子的变化特征,对CO₂吸收过程的反应热随着CO₂负载量的变化规律进行了预测并与已发表的数据进行了比较。结果表明,该吸收热模型能够准确地实现氨水吸收CO₂过程中汽液平衡、液相反应以及吸收热的计算。氨水吸收CO₂的反应热主要受H₂O的电离、NH₃的电离、NH₂COO^-的生成与水解、CO₂的溶解等反应过程的影响,H₂O的电离过程受NH₃的电离过程的抑制,对于总吸收热的贡献最大, NH₂COO^-的反应则随着CO₂负载量的增加先放热再吸热。随着温度的升高,总吸收热有所降低,当温度为80℃时,在较低的CO₂负载区间[0.2～0.5 mol CO₂·(mol NH₃)^-1],总吸收热约为70.5 kJ·(mol CO₂)^-1。     

外源H2对沼气发酵体系的影响

以水稻秸秆为原料,在30 L搅拌发酵罐中55℃下进行厌氧发酵产沼气实验,探索外源H₂的连续导入对发酵过程的影响。结果表明：外源H₂的导入可以实现沼气的原位提纯,CH₄相对平均体积分数从69.6%可提高到94.4%（搅拌速度100 r·min^-1）,同时CO₂相对平均体积分数从30.4%降低至5.6%（搅拌速度100 r·min^-1）;对比无搅拌的小试装置,搅拌速度为50 r·min^-1时,搅拌可将外源H₂的利用率从91.0%提高到93.1%,转化率从85.0%提高到96.8%;外源氢的导入可明显促进丙酸、丁酸和异丁酸的降解,可有效地避免发酵过程中VFAs的累积问题,同时搅拌的加强对发酵体系乙酸分解产CH₄和沼液中CO₂的消耗也有明显的促进作用,最终使得沼液的pH略有上升;外源H₂的通入与搅拌改变了发酵系统内的微生物群落组成比例,但并未对系统内的产CH₄微生物群落结构产生明显的影响。     

抗坏血酸对Fe2+/H2O2体系氧化NO的促进作用

采用实验方法研究了低成本环境友好型添加剂抗坏血酸(AA)对Fe²⁺/H₂O₂体系氧化NO气体及其对体系内H₂O₂分解的影响,分析了AA对体系氧化NO能力及H₂O₂分解的影响机制。研究结果表明:AA通过加速Fe³⁺向Fe²⁺的转化而促进Fe²⁺/H₂O₂体系对NO的氧化。[AA]₀:[Fe²⁺]₀对体系氧化NO的能力及H₂O₂的分解具有重要影响。综合考虑NO氧化脱除量及H₂O₂消耗量,合理的[AA]₀:[Fe²⁺]₀为1/3~1/2。AA的分次添加方式可大幅度提升体系氧化NO气体的能力。研究结果可望为发展基于H₂O₂为氧化剂的烟气NO绿色氧化技术提供理论基础。     

Zn(OAc)2/AC催化固定床上CO2与1,2-丙二醇合成碳酸丙烯酯及其反应机理

以负载型乙酸锌为催化剂,在固定床上实现了CO₂和1,2-丙二醇(PG)合成碳酸丙烯酯(PC)反应。考察了不同载体和负载量对负载型乙酸锌催化性能的影响以及反应条件对PC合成反应的影响。结果表明:负载量为40% (质量分数)的Zn(OAc)₂/AC催化性能最好。CO₂与PG合成PC适宜的反应条件为:PG、乙腈和CO₂的摩尔比为1:1.8:11,CO₂ 压力 4.0 MPa,反应温度160 ℃和液空速0.9 h^-1。在此条件下,PC收率和选择性分别为6.3%和49.0%。采用原位红外结合设计实验研究了无水乙酸锌分别与CO₂和PG之间的相互作用,发现CO₂与乙酸锌之间的化学吸附比较弱,而PG与乙酸锌之间的化学吸附较强,能够活化PG。据此推测了乙酸锌催化CO₂与PG合成PC的反应机理。     

CO2碳酸化石灰岩酸解产物回收乙酸及副产沉淀碳酸钙

乙酸酸解石灰石造腔是一种建造地下储库同时环保地开采石灰岩制备沉淀碳酸钙的新方法。通过耦合乙酸酸解石灰石及酸解产物乙酸钙CO₂碳酸化的工艺过程,研究了乙酸酸解石灰岩的表面反应动力学和乙酸钙CO₂碳酸化的工艺技术条件。采用正交实验分析法,研究了CO₂碳酸化反应中乙酸钙浓度、反应温度、CO₂压力、反应时间对乙酸钙碳酸化反应制沉淀碳酸钙的影响,并通过正交实验确定了最优化操作条件。实验结果表明,乙酸酸解反应速率主要受乙酸浓度控制。CO₂碳酸化反应在当乙酸钙溶液浓度为0.631 mol·L^-1,CO₂压力为5.0 MPa,温度为80℃,反应时间为50 min时CO₂碳酸化效率达到最高（23.13%）,生成的沉淀碳酸钙产品各项指标均符合中国国标优级要求。     

基于Langmuir-Hinshelwood动力学解析O2/CO2/H2O气氛下烟煤焦反应机理

流化床富氧燃烧湿烟气循环兼具经济与环保优势。湿烟气循环（O₂/CO₂/H₂O）条件下煤焦与O₂、CO₂及H₂O的反应同时发生。为探究O₂/CO₂/H₂O气氛下煤焦-O₂、煤焦-CO₂、煤焦-H₂O反应间的相互作用机制,在自制高精度热重实验装置上系统考察了O₂、CO₂、H₂O及其混合气氛下,典型烟煤焦在900℃的反应特性。基于吸附和脱附原理的Langmuir-Hinshelwood（L-H）机理性模型分别计算了烟煤焦与O₂、CO₂和H₂O反应的动力学参数。通过采用单独活性位点与竞争活性位点两种假设分析了O₂/CO₂、O₂/H₂O和CO₂/H₂O气氛下烟煤焦-O₂、烟煤焦-CO₂和烟煤焦-H₂O两两反应间的作用机制,揭示了H₂O分子优先吸附于烟煤焦表面活性位点,O₂分子次之,而CO₂分子相对滞后。O₂/CO₂/H₂O气氛下烟煤焦-O₂、烟煤焦-CO₂、烟煤焦-H₂O反应表现出部分竞争反应活性位点,传统的单独活性位点与竞争活性位点假设均无法准确描述其反应速率特性。基于H₂O分子优先,O₂分子次优先吸附的原理,建立了O₂、CO₂、H₂O混合气氛下煤焦反应速率L-H动力学方程,方程计算结果与实验值良好吻合。研究结果为深入分析煤焦颗粒流化床富氧燃烧特性及构建可靠、准确的燃烧反应模型提供了理论支撑。     

Characteristics of reactivity and structures of palm kernel shell (PKS) biochar during CO2/H2O mixture gasification

Palm kernel shell (PKS) biochars with different levels of carbon conversion were initially prepared using a tube furnace, after which the reactivity of each sample was assessed with a thermogravimetric analyzer under a CO₂ atmosphere. The pore structure and carbon ordering of each biochar also examined, employing a surface area analyzer and a Raman spectroscopy. Thermogravimetric results showed that the gasification index R_s of the PKS biochar decreased from 0.0305 min^-1 at carbon conversion (x)=20% to 0.0278 min^-1 at x=40%. The expansion of micropores was the dominant process during the pore structure evolution, ad mesopores with sizes ranging from 6 to 20, 48 to 50 nm were primarily generated during gasification under a CO₂/H₂O mixture. The proportion of amorphous carbon in the PKS biochar decreased significantly as x increased, suggesting that the proportion of ordered carbon was increased during the CO₂/H₂O mixed gasification. A significantly reduced total reaction time was observed when employing a CO₂/intermittent H₂O process along with an 83.46% reduction in the steam feed, compared with the amount required using a CO₂/H₂O atmosphere.     

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%。     

杂质离子对MgCl2和CO2反应-萃取-醇析耦合过程的影响

通过反应-萃取-醇析耦合过程，将MgCl₂和CO₂制备成碳酸镁和氯化氢气体是盐湖老卤资源化利用的有效途径。系统地研究了老卤中Na⁺、K⁺、Ca²⁺对MgCl₂和CO₂反应-萃取-醇析耦合过程得到的固体产物晶型晶貌的影响。结果表明，Na⁺和K⁺对耦合过程的影响相似，固体产物均为高纯棒状三水碳酸镁（MgCO₃·3H₂O），且Na⁺和K⁺均能选择性吸附在MgCO₃·3H₂O晶体的轴面（101），阻碍该晶面的生长，使得棒状MgCO₃·3H₂O直径变小；Ca²⁺对反应-萃取-醇析耦合过程有不利的影响，由于CaCl2能参与反应，生成球状无定形纳米钙镁碳酸盐，使得三水碳酸镁纯度降低。     

ABSORPTION OF SO2 AND H2S IN SMALL-SCALE VENTURI SCRUBBERS

Small-scale venturi scrubbers having geometries of typical large-scale units were constructed from glass and were operated in a laboratory system. Carrier gas streams consisting of air or nitrogen and up to 30% (by volume) CO₂ were mixed with SO₂ or H₂S to give SO₂ or H₂S concentrations in the range of 1890-4400 ppm. These gas mixtures were then scrubbed in the Venturis using various injected liquids (plain water, NaOH solutions, NH₄OH solutions, and NaOH/NaHCO₃ solutions) at L/G ratios of 0.0004-0.0040 m³ liquid per standard (1 atm, 60°F)m³ of gas (3-30 gallons liquid per 1000 standard ft³ of gas). Absorption percentages for SO₂ and H₂S were determined as functions of the L/G ratio, initial liquid pH, and liquid composition. The effects of venturi throat length, gas velocity, and the presence of CO₂ in the gas stream were also determined.     

On-stream modification of MFI zeolite membranes for enhancing hydrogen separation at high temperature

-Alumina-supported MFI zeolite membranes were modified by on-stream catalytic thermal cracking of methyldiethoxysilane (MDES) molecules inside the zeolitic channels during the separation of H₂/CO₂ gas mixture at 450 °C and atmospheric pressure. The MDES vapor was carried by the H₂/CO₂ feed gas and the effect of modification was monitored continuously through online analysis of the permeate stream. The modified membrane exhibited a significant increase in H₂ selectivity over CO₂ with a moderate decrease in H₂ permeance. At 450 °C, the modified MFI membrane obtained a H₂/CO₂ permselectivity of 17.5 with H₂ single gas permeance of 1.86 × 10⁻⁷ mol m⁻² s⁻¹ Pa⁻¹ as compared to a permselectivity of 2.78 and permeance of 2.75 × 10⁻⁷ mol m⁻² s⁻¹ Pa⁻¹ for the membrane before modification. The modified membrane also showed good performance and stability in separation of H₂/CO₂ gas mixture containing up to 28.4% water vapor at 450 °C and atmospheric pressure.     

Kinetics of CO and H2 oxidation over CuO-CeO2 catalyst in H2 mixtures with CO2 and H2O

The kinetics of CO and H₂ oxidation over a CuO-CeO₂ catalyst were simultaneously investigated under reaction conditions of preferential CO oxidation (PROX) in hydrogen-rich mixtures with CO₂ and H₂O. An integral packed-bed tubular reactor was used to produce kinetic data for power-law kinetics for both CO and H₂ oxidations. The experimental results showed that the CO oxidation rate was essentially independent of H₂ and O₂ concentrations, while the H₂ oxidation rate was practically independent of CO and O₂ concentrations. In the CO oxidation, the reaction orders were 0.91, −0.37 and −0.62 with respect to the partial pressure of CO, CO₂ and H₂O, respectively. In the H₂ oxidation, the orders were 1.0, −0.48 and −0.69 with respect to the partial pressure of H₂, CO₂ and H₂O, respectively. The activation energies of the CO oxidation and the H₂ oxidation were 94.4 and 142 kJ/mol, respectively. The rate expressions of both oxidations were able to predict the performance of the PROX reactor with accuracy. The independence between the CO and the H₂ oxidation suggested different sites for CO and H₂ adsorption on the CuO-CeO₂ catalyst. Based on the results, we proposed a new reaction model for the preferential CO oxidation. The model assumes that CO adsorbs selectively on the Cu⁺ sites; H₂ dissociates and adsorbs on the Cu⁰ sites; the adsorbed species migrates to the interface between the copper components and the ceria support, and reacts there with the oxygen supplied by the ceria support; and the oxygen deficiency on the support is replenished by the oxygen in the reaction mixture.     

An evaluation of autotrophic microbes for the removal of carbon dioxide from combustion gas streams

Carbon dioxide is a greenhouse gas that is believed to be a major contributor to global warming. Studies have shown that significant amounts of CO₂ are released into the atmosphere as a result of fossil fuels combustion. Therefore, considerable interest exists in effective and economical technologies for the removal of CO₂ from fossil fuel combustion gas streams. This work evaluated the use of autotrophic microbes for the removal of CO₂ from coal fired power plant combustion gas streams. The CO₂ removal rates of the following autotrophic microbes were determined: Chlorella pyrenoidosa, Euglena gracilis, Thiobacillus ferrooxidans, Aphanocapsa delicatissima, Isochrysis galbana, Phaodactylum tricornutum, Navicula tripunctata schizonemoids, Gomphonema parvulum, Surirella ovata ovata, and four algal consortia. Of those tested, Chlorella pyrenoidosa exhibited the highest removal rate with 2.6 g CO₂ per day per g dry weight of biomass being removed under optimized conditions. Extrapolation of these data indicated that to remove CO₂ from the combustion gases of a coal fired power plant burning 2.4 × 10⁴ metric tons of coal per day would require a bioreactor 386 km² × 1 m deep and would result in the production of 2.13 × 10⁵ metric tons (wet weight) of biomass per day. Based on these calculations, it was concluded that autotrophic CO₂ removal would not be feasible at most locations, and as a result, alternate technologies for CO₂ removal should be explored.     

Characterization and catalytic activity of soft-templated NiO-CeO2 mixed oxides for CO and CO2 co-methanation

Nanosized NiO,CeO₂ and NiO-CeO₂ mixed oxides with different Ni/Ce molar ratios were prepared by the soft template method.All the samples were characterized by different techniques as to their chemical composition,structure,morphology and texture.On the catalysts submitted to the same reduction pretreatment adopted for the activity tests the surface basic properties and specific metal surface area were also determined.NiO and CeO₂ nanocrystals of about 4 nm in size were obtained,regardless of the Ni/Ce molar ratio.The Raman and X-ray photoelectron spectroscopy results proved the formation of defective sites at the NiO-CeO₂ interface,where Ni species are in strong interaction with the support.The microcalorimetric and Fourier transform infrared analyses of the reduced samples highlighted that,unlike metallic nickel,CeO₂ is able to effectively adsorb CO₂,forming carbonates and hydrogen carbonates.After reduction in H2 at 400°C for 1 h,the catalytic performance was studied in the CO and CO₂ co-methanation reaction.Catalytic tests were performed at atmospheric pressure and 300°C,using CO/CO₂/H₂ molar compositions of 1/1/7 or 1/1/5,and space velocities equal to 72000 or 450000 cm³?h^-1?gcat^-1.Whereas CO was almost completely hydrogenated in any investigated experimental conditions,CO₂ conversion was strongly affected by both the CO/CO₂/H₂ ratio and the space velocity.The faster and definitely preferred CO hydrogenation was explained in the light of the different mechanisms of CO and CO₂ methanation.On a selected sample,the influence of the reaction temperature and of a higher number of space velocity values,as well as the stability,were also studied.Provided that the Ni content is optimized,the NiCe system investigated was very promising,being highly active for the CO_x co-methanation reaction in a wide range of operating conditions and stable(up to 50 h)also when submitted to thermal stress.