添加金属氧化物的V2O5/AC在烟气脱SO2及脱SO2后H2再生制备硫磺的活性研究

干法脱除烟气SO2的多种催化剂均可在H2气氛中再生,直接制备硫磺。该过程的实现不仅要求再生尾气循环,而且要求催化剂具有双重功能,即在脱硫过程中催化氧化SO2为H2SO4以及在再生过程中将催化还原释放出的SO2进一步转化为硫磺。添加有金属氧化物的V2O5/AC催化剂具备双重功能。着重考察了添加Ce、W、Fe、Co 等氧化物的V2O5/AC催化剂烟气SO2脱除能力及脱除SO2后经H2再生制备硫磺的能力,并对添加Co的催化剂进行了优化。结果表明,在这类催化剂中,对烟气脱SO2起主要催化氧化作用的是V2O5,对H2再生硫磺制备起作用的是添加的金属氧化物。除Ce2O3外,WO3、Fe2O3和CoO都提高了再生中的硫磺收率,CoO的作用最为显著。较合适的催化剂组成是1%V2O5和0.5%CoO。这些金属氧化物在AC上的担载方法,对烟气脱SO2和H2再生结果的影响不明显。硫磺的生成需要CoO向CoS2的转变,再生后催化剂上残余有部分CoS2,且残余硫量还与V2O5量有关。     

SCR催化剂碱(土)金属中毒的研究进展

在选择性催化还原(SCR)烟气脱硝系统中,催化剂碱(土)金属中毒和再生受到广泛关注。本文综述了SCR脱硝催化剂碱(土)金属中毒的失活机理及基于分子水平上碱金属中毒的研究新思路,并根据催化剂的各种失活机理,有针对性地综述了提高催化剂抗碱金属中毒的途径及中毒催化剂的再生方法。     

Hysteresis phenomena in sulfur dioxide oxidation over supported vanadium catalysts

Catalyst deactivation and hysteresis behavior in industrial SO₂-oxidation catalysts have been studied in the temperature region 350–480°C by combined in situ EPR spectroscopy and catalytic activity measurements. The feed gas compositions simulated sulfuric acid synthesis gas and wet/dry deNO_x'ed flue gas. The vanadium (IV) compound K₄(VO)₃(SO₄)₅ precipitated during all the investigated conditions hence causing catalyst deactivation. Hysteresis behavior of both the catalytic activity and the V(IV) content was observed during reheating.     

Gold(I)-catalyzed addition of thiols and thioacids to 3,3-disubstituted cyclopropenes

Gold(I)-catalyzed reactions of thiols, thiophenols, and thioacids with 3,3-disubstituted cyclopropenes occur in a regioselective and chemoselective manner to produce either vinyl thioethers or primary allylic thioesters in good yields. A survey of commonly used gold(I) catalysts shows Echavarren's cationic gold(I) catalyst to be most tolerant of deactivation by sulfur. A novel digold with bridging thiolate complex is characterized by X-ray crystallography, shedding light on a possible deactivation pathway.     

过渡金属硫化物催化剂上SO2的还原

 对系列过渡金属硫化物催化剂上CO还原SO2的反应进行了研究．结果表明，FeS的催化性能最好，而MnS的催化性能最差，其他几种催化剂的活性顺序依次为CoS＞CuS＞NiS．催化剂的活性与硫化物自身的氧化还原能力、所具有的晶相结构及其同SO2的吸附键合作用力有密切的关系．在硫化物催化剂上，SO2还原的反应机理很可能是贫、富含硫化合物的交替作用机理．     

XAFS STUDIES OF IRON CATALYSTS FOR F-T SYNTHESIS

IntroductionX-rnyabsorptionfinestructure(XAFS)spectroscopeprovidesauniqucopportunitytodetermincthcstructureofnanophasesystemswithshort-rangeorder,suchascatalystslllAnalysisofthcextendedpartofX-rayabsorptionfincstructure(EXAFS)providesthcinformationaboutthcidcntity,intefatomicdistanccs,andcoordinationnumbcrofatomsintheneghboringatomicshellssurroundingthccentralabsorbingatomFortransitionmetalcompondswithincompletelyfilleddshellthesamepre-edgepcaksintheX-rayabsorptionncar-edgestructure(XANE…     

铜基甲醇合成催化剂的失活研究

选用了两个化肥厂的失活甲醇合成催化剂,采用ＸＲＤ、ＳＥＭ、ＳＥＭ－ＥＤＳ、ＴＥＭ、ＸＰＳ、ＴＲＰ、ＣＯ－ＴＰＤ和化学吸附等方法对催化剂进行比较测试。结果表明,硫中毒、积炭、铜粒长大和杂质金属沉积等是造成甲醇合成催化剂失活的因素。由于某一种或几种因素都导致催化剂活性表面积的降低,对反应物ＣＯ吸附量减少,或造成催化剂对ＣＯ吸附能力的降低,从而降低合成甲醇反应的活性。硫中毒和铜粒长大是普遍存在的最主要因     

Mechanisms of catalytic biomass gasification

This paper discusses possible mechanisms for the pyrolytic reaction of biomass with steam in the presence of alkali carbonate and supported-nickel catalysts. In addition to catalyzing the carbon/steam reaction, the alkali carbonates alter the biomass pyrolysis reaction path-ways, producing gas and char at the expense of tars. Nickel catalyst, while quite effective for secondary tar and gas reactions, tend to lose activity over time; therefore, studies of these catalysts were directed toward identifying mechanisms of carbon deposition, the primary cause of catalyst deactivation.     

Kinetics of Catalyst Poisoning during Capillary Condensation of Reactants

The influence of the capillary condensation of reactants on the poisoning of Pt/SiO₂ catalysts by thiophene is studied experimentally for p-xylene hydrogenation at T = 60 and 80°C. The poisoning kinetics is independent of a catalyst and its rate decreases with a decrease in temperature. Poisoning during capillary condensation is 1.5–6 times slower than that in the gas phase, depending on the fraction of surface platinum in the pores filled with a liquid. The poisoning of the catalyst active sites in the pores filled with a liquid requires less sulfur at the same deactivation degree. The number of sulfur atoms per one platinum atom necessary for the complete poisoning of platinum in the gas phase is higher than that in the case of capillary condensation by a factor of 1.4–1.5.     

Continuous Heterogeneous Photocatalysis in Serial Micro‐Batch Reactors

Solid reagents, leaching catalysts, and heterogeneous photocatalysts are commonly employed in batch processes but are ill‐suited for continuous‐flow chemistry. Heterogeneous catalysts for thermal reactions are typically used in packed‐bed reactors, which cannot be penetrated by light and thus are not suitable for photocatalytic reactions involving solids. We demonstrate that serial micro‐batch reactors (SMBRs) allow for the continuous utilization of solid materials together with liquids and gases in flow. This technology was utilized to develop selective and efficient fluorination reactions using a modified graphitic carbon nitride heterogeneous catalyst instead of costly homogeneous metal polypyridyl complexes. The merger of this inexpensive, recyclable catalyst and the SMBR approach enables sustainable and scalable photocatalysis.     

平板式V_2O_5-MoO_3/TiO_2型SCR催化剂的中低温脱硝和抗中毒性能研究

针对中低温锅炉烟气脱硝技术需求的特点,采用等体积浸渍法,以V_2O_5为活性组分、MoO_3为助剂,制备了高钒高钼含量的V_2O_5-MoO_3/TiO_2型粉末和平板式SCR脱硝催化剂,考察了活性组分和助剂含量对催化剂活性以及抗SO_2和H_2O中毒性能的影响,对反应前后的催化剂进行了微观表征,并针对最优催化剂研究了其在不同烟气工况下催化剂的脱硝性能。结果表明,提升V_2O_5负载量可以有效提高催化剂的脱硝活性;MoO_3助剂的添加也可以提高催化剂的脱硝活性。XPS、XRF、FTIR等表征结果表明,MoO_3的含量会影响催化剂中V~(4+)/V~(5+)的比值,其相对含量的增加有利于催化剂中非化学计量钒物种的形成以及化学吸附氧比例的增加,钼与钒物种间的交互作用是抑制SO_2和H_2O对催化剂的毒化作用的关键。3V_2O_5-10MoO_3/TiO_2平板式催化剂在温度为200℃、空速为3 500 h~(-1)含SO_2和H_2O烟气条件下,经30 d连续反应,脱硝效率稳定维持在82%左右,该催化剂在中低温下具有优异的抗SO_2和H_2O中毒性能以及稳定性。     

Solid-phase synthesis of homogeneous ruthenium catalysts on silica for the continuous asymmetric transfer hydrogenation reaction

The solid-phase synthesis of new asymmetric transfer hydrogenation catalysts as well as the use of these silica supported systems in batch and flow reactors is reported. The ruthenium complex of NH-benzyl-(1R,2S)-(-)-norephedrine covalently tethered to silica showed a high activity and enantioselectivity in the reduction of acetophenone. In three consecutive batchwise catalytic runs, we obtained ee values of 88%. In a continuous flow reactor, a very constant catalytic activity was observed; no catalyst deactivation occurred over a period of one week. This has been ascribed to successful site isolation. Using optimized conditions in this flow reactor, the ee was as high as 90% at 95% conversion. The supported catalysts generally show the same trend in catalyst performance as in solution. The viability of our approach was further shown in one example, the ruthenium(II) complex of (1S,2R)-(+)-2-amino-1,2-diphenylethanol, for which an enantiomeric excess of 58% was observed, which is nearly three times higher than its homogeneous analogue.     

Role of hydrogen in catalytic dehydrogenation: Film diffusion controlled deactivation

The function of hydrogen used as carrier gas in catalytic dehydrogenation is to increase the selectivity and stability of catalysts. It slows down catalyst deactivation by either inhibiting deposition of potential coke precursors or facilitating their desorption by rehydrogenation. This function, in gas-solid catalytic dehydrogenation appears to be interphase mass transfer controlled by increased hydrogen linear flow velocities decreasing the extent of deactivation. Besides, deactivation appears to progress through two regimes, an initial short term followed by a long term deactivation.     

Synthesis of seven and higher-membered heterocycles using ruthenium catalysts

A wide variety of biological activities are possessed by nitrogen, oxygen, and sulfur containing heterocycles and many methods are explored for the preparation of these heterocyclic compounds. Metal catalysts are used in organic reactions with high activity. The synthesis of heterocycles with the help of metal catalysts became very important in organic synthesis. New protocols have been investigated for the synthesis of heterocycles in the last decades. In present review article I have concentrated on the synthesis of seven and higher-membered heterocylces in the presence of ruthenium catalyst.     

Mo-Co-Mg/Al2O3工业耐硫变换催化剂的失活

利用活性评价、程序升温技术、硫的测定、Ｘ光衍射和孔结构分析等手段,对工业耐硫变换催化剂（Ｋ）失活原因进行了研究,并与模型催化剂进行了比较．结果表明,催化剂（Ｋ）失活的原因是烧结;部分物相分离及转化生成不活泼ＭｏＳ２、ＣｏＳ２、ＣｏＳＯ４和ＭｇＡｌ２Ｏ４及活性硫转化为非活性硫．模型实验表明,反应温度偏高和水蒸汽量过大是加速失活的主要原因．     

Engineering Catalyst Microenvironments for Metal‐Catalyzed Hydrogenation of Biologically Derived Platform Chemicals

It is shown that microenvironments formed around catalytically active sites mitigate catalyst deactivation by biogenic impurities that are present during the production of biorenewable chemicals from biologically derived species. Palladium and ruthenium catalysts are inhibited by the presence of sulfur‐containing amino acids; however, these supported metal catalysts are stabilized by overcoating with poly(vinyl alcohol) (PVA), which creates a microenvironment unfavorable for biogenic impurities. Moreover, deactivation of Pd catalysts by carbon deposition from the decomposition of highly reactive species is suppressed by the formation of bimetallic PdAu nanoparticles. Thus, a PVA‐overcoated PdAu catalyst was an order of magnitude more stable than a simple Pd catalyst in the hydrogenation of triacetic acid lactone, which is the first step in the production of biobased sorbic acid. A PVA‐overcoated Ru catalyst showed a similar improvement in stability during lactic acid hydrogenation to propylene glycol in the presence of methionine.     

Selective adsorption of refractory sulfur species on active carbons and carbon based CoMo catalyst

Adsorption technique could be a reliable alternative in removing to a certain remarkable extent the sulfur species from the feedstock of petroleum oil. The performance of various carbons on adsorption of model sulfur compounds in a simulated feed solution and the sulfur containing compounds in the real gas oil was evaluated. The adsorption experiments have been carried out in a batch scale at ambient temperature and under the atmospheric pressure. In general, the most refractory sulfur compounds in the hydrotreatment reactions were selectively removed and adsorbed. It was found that the adsorbents affinities to dibenzothiophene and 4,6-dimethyldibenzothiophene were much more favored and pronounced than the aromatic matrices like fluorene, 1-methylnaphthalene and 9-methylanthracene. Among the sulfur species, 4,6-dimethyldibenzothiophene was the highest to be removed in terms of both selectivity and capacity over all the present adsorbents. The studied adsorbents showed significant capacities for the polyaromatic thiophenes. The electronic characteristics seem to play a certain role in such behavior. Regeneration of the used adsorbent was successfully attained either by washing it with toluene or by the release of the adsorbates through heat treatment. A suggested adsorptive removal process of sulfur compounds from petroleum distillate over carbon supported CoMo catalyst was discussed.     

硫化NiW/Al2O3催化剂上H2同时催化还原SO2和NOⅠ.NO的分解与还原

 考察了NO在硫化NiW/Al2O3催化剂上分解和还原的规律. 结果表明,在350 ℃以上,NO完全分解,但同时催化剂的晶格硫因氧化而以SO2的形式大量流失,最终导致催化剂完全失活. 在NO分解反应体系中,按化学计量比引入的H2与晶格硫竞争消耗NO分解所生成的Oad,使晶格硫的氧化在一定程度上得到抑制; 氧化的部分晶格硫能通过一系列氧化还原过程重新进入催化剂晶格,导致晶格硫的流失速度和程度得到缓和,催化剂可在较长的时间内保持较高的NO转化活性. 但是,催化剂的活性最终仍会因为大部分晶格硫逐渐流失而大幅度下降.     

Morphological and chemical influences on alumina-supported palladium catalysts active for the gas phase hydrogenation of crotonaldehyde

A series of five alumina-supported palladium catalysts have previously been prepared and characterised by a combination of CO chemisorption and infrared spectroscopy. The reactive attributes of these catalysts are examined using the hydrogenation of crotonaldehyde as a test reaction, using a modified infrared gas cell as a batch reactor. Periodic scanning of the infrared spectrum of the gaseous phase present over the Pd/Al(2)O(3) catalysts was used to construct reaction profiles. Four of the catalysts were able to facilitate a 2-stage hydrogenation process (crotonaldehyde → butanal → butanol), whilst one catalyst was totally selective for the first stage hydrogenation process (crotonaldehyde → butanal). Rate coefficients for the first and second stage hydrogenation processes are normalised to the number of surface palladium atoms for the particular catalyst. Correlation of these kinetic parameters as a function of mean particle size indicates the first stage process to be structure insensitive, whilst the second stage hydrogenation is structure sensitive. Chlorine residues associated with the preparative process of one of the catalysts is seen to selectively poison the second stage hydrogenation process for that catalyst. Structure/activity relationships are considered to explain the observed trends.     

Interaction forces between a deformable air bubble and a spherical particle of tuneable hydrophobicity and surface charge in aqueous solutions

Unsupported nanosized MoS(2) and CoMo-sulfide catalysts were synthesized, and their catalytic performances for the deep hydrodesulfurization (HDS) of treated gas oil were investigated as compared with that of a CoMo/Al(2)O(3) catalyst. The HDS reactions were carried out in a batch autoclave reactor at 340 °C and 3 MPa H(2). The CoMo-sulfide catalyst shows the highest activity and can reduce the sulfur content to less than 10 ppm. The decrease in total sulfur content as a function of reaction time was found to follow pseudo-second order kinetics (empirical form). The change in the concentration of some individual representative sulfur-containing species in gas oil as a function of time was found to follow pseudo-first-order kinetics. However, the change in combined concentration of these species in the gas oil during HDS with the reaction time was found to corroborate pseudo-second-order kinetics. A kinetic model approach was proposed from which an estimation of the intrinsic kinetic data can be achieved. The model fitted the obtained data reasonably well, suggesting its potential for better assessment of the catalytic activity in the HDS of real feedstock. The study reveals that ranking of catalyst activities using model refractory sulfur-containing compounds does not necessarily imply a typical rank in case of investigating the real feedstocks.