Alkaline hydrogen peroxide bleaching of cellulose

A closed system bleaching apparatus was designed to determine the kinetics and effects of various factors on alkaline hydrogen peroxide bleaching of textile cellulose fabrics. It was confirmed that perhydroxyl anion is the primary bleaching moiety in alkaline hydrogen peroxide systems. The use of the apparatus in the measurement of fabric color, waste oxygen, and the subsequent calculation of hydroxyl ion, and molecular hydrogen peroxide confirmed that pH and titration of 'free' hydrogen peroxide in alkaline bleaching systems are not good indicators of bleaching mechanism. The role of the cellulose itself in the chemical bleaching system was determined. The rate of bleaching on cotton fabric was shown to be a first order reaction in concentration of perhydroxyl anion at 60 and 90°C. An activation energy of 17kcal/mole was estimated. Decomposition of H₂O₂ into waste oxygen was found to be second order kinetics.     

Future perspectives for the advancement of electrochemical hydrogen peroxide production

Hydrogen peroxide (H₂O₂)is an important chemical with multiple uses across domestic and industrial settings. With a global need for wider adoption of green synthetic methods, there has been a growing interest in the electrochemical synthesis of H₂O₂ from oxygen reduction or water oxidation. State-of-the-art catalyst and reactor developments are beginning to advance to a stage where electrochemical synthesis is discussed as a viable alternative to current industrial methods. In this review, we highlight some of the most promising candidates for H₂O₂ electrosynthesis technologies and what further advancements are needed before the electrochemical route could challenge the ubiquitous anthraquinone process.     

预处理对Ni-Co双金属沼气重整催化剂性能与结构的影响

采用过量浸渍法制备了Ni-Co/La₂O₃-γ-Al₂O₃双金属催化剂, 并使用固定床石英反应器在850℃,0.1MPa和空速为6000mL g_cat^-1 h^-1的条件下考察了预处理对催化剂性能的影响. 运用X射线衍射、热重-差示扫描量热、透射电子显微镜、扫描电镜和X射线能谱分析等手段对催化剂进行了表征. 结果表明,与传统氢气还原预处理相比,经氢气和二氧化碳预处理后, 催化剂性能明显提高,且能基本消除该催化剂上沼气重整反应的诱导期. 511 h的稳定性实验结果表明,催化剂经氢气和二氧化碳预处理后具有很好的稳定性和抗积碳性,平均积碳速率仅为0.2 mg g_cat^-1 h^-1. 表征结果显示,经氢气和二氧化碳预处理后,催化剂具有更好的抗烧结和抗积碳性能,反应后金属颗粒较小,分布较均匀,粒径分布范围较窄,从而增强了催化剂的稳定性.     

Production and energetic use of biogas from energy crops and wastes in Germany

The production of biogas for reducing fossil CO₂ emissions is one of the key strategic issues of the German government and has resulted in the development of new process techniques and new technologies for the energetic use of biogas. Progress has been made in cultivating energy crops for biogas production, in using new reactor systems for anaerobic digestion, and in applying more efficient technologies for combined heat and power production. Recently, integration of fuel cells within the anaerobic digestion process was started, and new technologies for biogas upgrading and conversion to hydrogen were tested. This article describes the trends in Germany for achieving more efficient energy production.     

过氧化氢生产工艺进展

生产过氧化氢通常有电解法、蒽醌法、异丙醇法以及氧阴极还原法等.目前全世界总产量的95%以及国内总产量的99%的过氧化氢都是采用蒽醌法生产的.在更先进的生产过氧化氢的技术出现之前,蒽醌法仍将是今后一段时期生产过氧化氢最普遍的一种方法.蒽醌加氢工艺有固定床和浆态床两种,国内仍采用较为落后的固定床工艺,而国外基本都采用浆态床工艺.固定床存在床层温升大、易偏流、有局部热点等缺陷,易导致蒽醌过度加氢,降解物种类和数量增多,降低了催化剂稳定性,限制了加氢单元的氢效,生产装置难以大型化.而浆态床工艺具有传质传热好、温度和气液固三相分布均匀等优势,是过氧化氢生产技术的发展趋势.浆态床反应器对催化剂的选择性具有更高的要求.因此,浆态床加氢技术的研发核心是开发兼有耐磨性和高选择性的微球催化剂.中国石化自主开发了具有高活性、高选择性和良好稳定性的蒽醌加氢微球催化剂,并对其活性和选择性进行了寿命试验和中试评价.中试结束后结粒度分布基本保持不变;载体水热稳定性好,使用过程结构没有发生明显变化.证明该催化剂机械强度高、耐磨性能好,能够满足浆态床使用要求.在新生产工艺中采用自主开发的新型浆态床反应器,具有优异的传质、传热效率;催化剂粒径小,完全克服了固定床反应器在规模稍大时存在的偏流、沟流、触媒板结等缺点,氢化效率可长期稳定在11 g/L以上;副反应少,氢化降解物大幅度减少,极大地减轻后续降解物再生负担.在实际工业生产中,蒽醌加氢选择性无法实现100%,因此工作液中难以避免生成降解物,通常采用白土再生手段,使其再转变为蒽醌.但再生剂更换频繁,大大增加了生产成本,同时损失被物理吸附上去的昂贵的蒽醌.因此,十分有必要对蒽醌加氢的降解物种类进行定性识别并研究其再生机理,并在此基础上开发兼有长寿命和高活性的蒽醌降解物再生催化剂.中国石化采用GC-MS对乙基蒽醌和戊基蒽醌多种降解物进行比较全面的定性和定量研究,通过分析蒽醌工作液组成准确推测工作液再生效果,便于及时调整双氧水生产工艺工艺流程和优化参数;并自主开发高性能的蒽醌加氢降解物再生催化剂,可替代现有效率低下的白土床,显著提高装置经济性.为有效解决蒽醌法生产中氧化废气的排放问题,中国石化发明一种无尾气排放、无需溶剂回收、氧含量可控、可减少氧化残液量的蒽醌法生产过氧化氢的氧化方法,从源头上解决蒽醌法生产双氧水装置的最大环保问题,它的应用将使蒽醌法生产双氧水装置朝着绿色环保迈出一大步.目前蒽醌法生产H2O2虽然具有技术成熟、单程产率高、安全性高等优点,依旧存在投资高、工艺流程复杂,以及大量使用有机溶剂带来的产品污染、环境污染问题.与其相比,H2和O2直接合成H2O2(以下称为DSHP)技术的原子经济性高,并且污染少、环境友好.但由于反应过程中H2和O2直接接触,DSHP工艺存在一定的安全隐患.在反应过程中需要充入大量惰性气体稀释并循环,导致DSHP工艺效率低,操作及控制难度大.该反应所使用的Pd基催化剂,既有利于H2O2的生成,也利于三个副反应的发生:H2O的生成、H2O2的后续加氢及分解,导致产品选择性和产率较低.加入酸和卤素等稳定剂虽然可以显著提高产率,但存在设备腐蚀、催化剂活性组分流失等问题,严重影响催化剂的使用寿命.中国石化目前已经开始布局研发DSHP技术,在提高H2/O2反应的本质安全性、研发H2O2精准合成的催化材料和提高H2O2产能等方面做了大量的研究.可以预见,通过理论研究、实验设计和工程开发相结合,在不远的未来能够实现DHSP技术的工业应用.目前国内双氧水几乎全部采用蒽醌法生产.虽然蒽醌法工艺已很成熟,但在多个技术环节,特别是蒽醌加氢催化剂、工作液体系、加氢反应器和环保等方面,存在非常大改进提升的空间.这些问题是实现装置大型化必须解决的.中国石化在这几个方面都自主开发了创新技术,形成了国内全新的拥有自主知识产权的生产过氧化氢的成套技术.作为最直接、最环保、最经济的生产过氧化氢的方法,氢氧直接合成技术与化工反应过程耦合,是未来过氧化氢生产和应用的发展方向,中国石化也已经开始在此方面进行研究和布局.     

Trace water triggers high-efficiency photocatalytic hydrogen peroxide production

Photocatalytic production of hydrogen peroxide(H₂O₂)has attracted much attentions as a promising method for sustainable solar fuel.Here,we demonstrate that trace water can drastically boost highefficiency photocatalytic production of H₂O₂ with a record-high concentration of 113 mmol L^-1 using alkali-assisted C₃N₄ as photocatalyst in water/alcohol mixture solvents.By electron paramagnetic resonance(EPR)measurement,the radical species generated during the photocatalytic process of H₂O₂ are identified.We propose alcohol is used to provide and stabilize-OOH radicals through hydrogen bond,while trace water could trigger photocatalytic production of H₂O₂ via providing and transferring indispensable free protons to completely consume OOH radicals,which breaks the reaction balance of-OOH radical generation from alcohol.Thus-OOH radicals could be supplied by alcohol continuously to serve as a reservoir for high-efficiency production of H₂O₂.These results pave the way towards photocatalytic method on semiconductor catalysts as an outstanding approach for production of hydrogen peroxide.     

过氧化氢生产与利用的新进展

过氧化氢既可用作环境友好的绿色氧化剂,也可用作燃料电池中的太阳能燃料,因而受到越来越多的关注.本文综述了太阳能驱动分子氧氧化水制备过氧化氢及其作为绿色氧化剂和燃料的研究进展.利用太阳能将水的2e-和4e-氧化与分子氧的2e-还原相结合,使光催化生产过氧化氢成为可能;本文讨论了与2e-和4e-水氧化选择性及2e-和4e-...     

Simultaneous hydrogen and peroxide production by photocatalytic water splitting

Photocatalytic oxidation of water is a promising method to realize large-scale H₂O₂ production without a hazardous and energy-intensive process. In this study, we introduce a Pt/TiO₂(anatase) photocatalyst to construct a simple and environmentally friendly system to achieve simultaneous H₂ and H₂O₂ production. Both H₂ and H₂O₂ are high-value chemicals, and their separation is automatic. Even without the assistance of a sacrificial agent, the system can reach an efficiency of 7410 and 5096 μmol g^–1 h^–1 (first 1 h) for H₂ and H₂O₂, respectively, which is much higher than that of a commercial Pt/TiO₂(anatase) system that has a similar morphology. This exceptional activity is attributed to the more favorable two-electron oxidation of water to H₂O₂, compared with the four-electron oxidation of water to O₂.     

基于可再生能源的水电解制氢技术（英文）

在全球变暖,污染日益严重的今天,发展可再生清洁能源成为了当务之急.然而可再生能源(风能、太阳能)本身具有间断特性,这就需要寻找一种合适的能量媒介储存能量来保证其能源的稳定输出.当前,我国各地不断出现弃风、弃光和弃水电事件,据国家能源局的公开数据,仅2016年,全国弃风电量497×10~8 kW·h,弃光率仅西部地区就已达20%,弃风弃光日臻凸显[1].从地域方面来看,我国光伏发电呈现东中西部共同发展格局,其中,西部地区主要发展集中式光伏发电,新疆、甘肃、青海、宁夏的累计装机容量均超过5×10~6 k W·h,而中东部地区除集中式光伏发电外,还重点建设分布式光伏发电,江苏、浙江、山东、安徽的分布式光伏装机规模已超过100万千瓦.我国光伏发电集中开发的西北地区也存在严重的弃光问题.根据中国光伏行业协会发布的报告,我国的弃光现象主要集中于西北的新疆、甘肃、青海、宁夏和陕西五省区.据统计,2016年,五省区光伏发电量287.17×10~8 k W·h,弃光电量70.42×10~8 k W·h,弃光率为19.81%,各省区光伏发电并网运行数据如表格所示.可以看出,新疆、甘肃光伏发电运行较为困难,弃光电量绝对值高,弃光率分别达到32.23%和30.45%[2].在新能源体系中,氢能是一种理想的二次能源,与其它能源相比,氢热值高,其能量密度(140 MJ/kg)是固体燃料(50MJ/kg)的两倍多.且燃烧产物为水,是最环保的能源,既能以气、液相的形式存储在高压罐中,也能以固相的形式储存在储氢材料中,如金属氢化物、配位氢化物、多孔材料等.对可再生和可持续能源系统,氢气是一种极好的能量存储介质.氢气作为能源载体的优势在于:(1)氢和电能之间通过电解水技术可实现高效相互转换;(2)压缩的氢气有很高的能量密度;(3)氢气具有成比例放大到电网规模应用的潜力.制氢的方式有很多,包括:化石燃料重整、分解、光解或水解等.全球每年总共需要约40亿吨氢气,95%以上的氢气是通过化石燃料重整来获得,生产过程必然排出CO_2,而电解水技术利用可再生能源获得的电能进行规模产氢,可实现CO_2的零排放,可将具有强烈波动特性的风能、太阳能转换为氢能,更利于储存与运输.所存储的氢气可用于燃料电池发电,或单独用作燃料气体,也可作为化工原料.通过水电解方式获得的氢气纯度较高,可达99.9%以上.     

A conformal titanyl phosphate amorphous overlayer for enhancing photoelectrochemical hydrogen peroxide production

Photoelectrochemical(PEC) H₂O₂ production through water oxidation reaction(WOR) is a promising strategy,however,designing highly efficient and selective photoanode materials remains challenging due to competitive reaction pathways.Here,for highly enhanced PEC H₂O₂ production,we present a conformal amorphous titanyl phosphate(a-TP) overlayer on nanoparticulate TiO₂ surfaces,achieved via lysozyme-molded in-situ surface reforming.The a-TP overl...     

Ab initio determination of the roto-torsional energy levels of hydrogen peroxide

In the present paper, the roto-torsional energy levels of hydrogen peroxide are determined from ab initio calculations performed at the MP4(SDQ)/AUG-cc-pVTZ//MP4(SDQ)/cc-pVTZ+ ++ level. The rotational levels corresponding to the torsional states n = 0 and 1 are determined variationally up to J = 20. The flexible model used considers the roto-vibrational interactions. Symmetry conditions are included for classifying the levels and reducing the cost of diagonalization. Products of contracted torsional basis functions and top symmetric solutions are employed as basis functions. The calculated levels are in a very good agreement with the experimental data. In addition, the K-doubling has been obtained and the levels fitted to the top symmetric equations for determining the centrifugal distortion constants. The expectation values of the rotational constants at the lowest torsional levels are compared with the rotational constants arising from the experimental fit.     

Optical sensor for hydrogen peroxide

Three types of sensors for continuous determination of hydrogen peroxide (HP) are described. The working principles are based on the decomposition of HP by a catalyst and on the measurement of the amount of oxygen thereby produced. The change in oxygen tension is quantitatively determined via the quenching of the fluorescence of a silica gel-adsorbed dye entrapped in silicone rubber. Three methods were found to be useful for HP decomposition. In the first one, the enzyme catalase (which acts as the catalyst) is co-adsorbed onto silica gel and thus is in the same phase as the indicator. In the second one, the enzyme and the dye are adsorbed on different silica gel particles which then are incorporated into the polymer layer. In the third one, finely dispersed silver powder (another catalyst) is embedded in a silicone rubber layer that is spread over the oxygen sensing membrane. The sensor is capable of continuously recording HP in the 0.1 to 10.0 mM concentration range, with a precision of ±0.1 mM at 1 mM HP. Its response time varies from 2.5 to 5 min.     

Effect of pretreatment reagent and hydrogen peroxide on enzymatic hydrolysis of oak in percolation process

The effect of pretreatment reagent and hydrogen peroxide on enzymatic digestibility of oak was investigated to compare pretreatment performance. Pretreatment reagents used were ammonia, sulfuric acid, and water. These solutions were used without or in combination with hydrogen peroxide in the percolation reactor. The reaction was carried out at 170°C for the predetermined reaction time. Ammonia treatment showed the highest delignification but the lowest digestibility and hemicellulose removal among the three treatments. Acid treatment proved to be a very effective method in terms of hemicellulose recovery and cellulose digestibility. Hemicellulose recovery was 65–90% and digestibilities were >90% in the range of 0.01–0.2% acid concentration. In both treatments, hydrogen peroxide had some effect on digestibility but decomposed soluble sugars produced during pretreatment. Unlike ammonia and acid treatments, hydrogen peroxide in water treatment has a certain effect on hemicellulose recovery as well as delignification. At 1.6% hydrogen peroxide concentration, both hemicellulose recovery and digestibility were about 90%, which were almost the same as those of 0.2% sulfuric acid treatment. Also, digestibility was investigated as a function of hemicellulose removal or delignification. It was found that digestibility was more directly related to hemicellulose removal rather than delignification.     

Hydrothermal pretreatment of rice straw at relatively lower temperature to improve biogas production via anaerobic digestion

The performances of rice straw (RS) degradation and biogas production were examined at different pretreatment temperatures from 90℃ to 130℃ to improve biogas fermentation efficiency and net energy production in whole slurry. Test at 100℃ pretreatment, which achieved 12.8% higher net energy production from RS than that observed in the control, could be considered as the optimal choice.     

底物水解预处理对玉米秸秆发酵生物产氢的影响

水解预处理是影响纤维索类生物质发酵产氢效率的关键因素之一.在批式试验条件下,分别采用乳酸处理(方法A),生物处理(方法B)和生物/乳酸两步处理(方法C)方法对玉米秸秆进行糖化水解预处理;考察了水解预处理对产氢效率的影响.结果表明:经乳酸预处理、生物预处理和乳酸/生物两步处理的玉米秸秆的累积氢产量分别为132 mL/g,...     

Dilute-acid pretreatment of two short-rotation herbaceous crops

Applied Biochemistry and Biotechnology -     

Accurate ab initio potential energy surface and vibration‐rotation energy levels of hydrogen peroxide

The accurate ground‐state potential energy surface of hydrogen peroxide, H₂O₂, has been determined from ab initio calculations using the coupled‐cluster approach in conjunction with the correlation‐consistent basis sets up to septuple‐zeta quality. Results obtained with the conventional and explicitly correlated coupled‐cluster methods were compared. The core–electron correlation, scalar relativistic, and higher‐order valence–electron correlation effects were taken into account. The adiabatic effects were also discussed. The vibration–rotation energy levels of the H₂O₂, D₂O₂, and HOOD isotopologues were predicted, and the experimental vibrational fundamental wavenumbers were reproduced to 1 cm^?1 (“spectroscopic”) accuracy. © 2012 Wiley Periodicals, Inc.