Product oriented oxidative bromination of methane over Rh/SiO2 catalysts

Rh/SiO2 was prepared for the oxidative bromination of methane. The catalyst was prepared by calcination at different temperatures and for different times to obtain catalysts with different specific surface areas for the purposes of producing either CH3Br or CH3Br and CO. It was found that the catalyst having a low specific surface area (calcined at relatively high temperature) favors the selective oxidation of methane to prepare CH3Br, while the catalyst having a high specific surface area favors the deeper partial oxidation of methane, which is good for CH3Br and CO preparation. The 650 h on stream life-time test revealed that the catalytic performance of the 0.4Rh/SiO2--900-10 catalyst was excellent. Both methane conversion and CH3Br selectivity kept increasing trends during the life-time test. No matter how serious was the Rh leaching during the reaction, the 0.4Rh/SiO2--900-10 catalyst did not deactivate at all.     

In-Situ FT-IR Investigation Methane to Syngas over of Partial Oxidation of Rh/SiO2 Catalyst

Partial oxidation of methane to syngas （POM） over Rh/SiO2 catalyst was investigated using in-situ FT-IR. When methane interacted with 1.0wt%Rh/SiO2 catalyst, it was dissociated to adsorbed hydrogen and CHx species. The adsorbed hydrogen atoms were transferred to SiO2 surface by ＂spill-over＂ and reacted with lattice oxygen to form surface -OH species. POM mechanism was investigated over Rh/SiO2 catalyst using in-situ FT-IR. It was found that CO2 was formed before CO could be detected when CH4 and O2 were introduced over the preoxidized Rh/SiO2 catalyst, whereas CO was detected before CO2 was formed over the prereduced Rh/SiO2 catalyst.     

Rh/SiO_2催化剂上甲烷部分氧化制合成气的反应机理

采用原位Raman光谱技术,在原料气中的O2未完全耗尽的条件下,对CH4部分氧化制合成气反应的Rh/SiO2催化剂床层前部贵金属物种的化学态以及由CH4解离所生成的碳物种进行了表征.在此基础上采用脉冲反应和同位素示踪技术,比较了CH4的部分氧化及其与H2O和CO2的重整等反应对催化剂床层氧化区内CO和H2生成的相对贡献,并将实验结果与Ra-man光谱表征结果进行了关联.结果表明,在600°C下将还原后的4%Rh/SiO2催化剂切入CH4:O2:Ar=2:1:45原料气,催化剂床层前部未检测到铑氧化物的Raman谱峰,但可清晰检测到源于CH4解离的碳物种;在700°C和接触时间小于1ms的条件下,催化剂床层的氧化区内已有大量CO和H2生成,在相同的实验条件下,CH4与H2O或CO2重整反应对氧化区内合成气生成的贡献则很小;以CH4:16O2:H218O:He=2:1:2:95为原料气的同位素示踪实验结果表明,在原料气中16O2未完全耗尽的情况下,反应产物中C16O的含量占CO生成总量的92.3%,表明CO主要来自CH4的部分氧化反应.上述结果均表明,在O2存在下Rh/SiO2催化剂上CO和H2可以通过CH4直接解离和部分氧化机理生成.     

Rh/SiO_2催化剂上甲烷部分氧化制合成气反应机理的研究(英文)

运用ＴＰＳＲ、ＴＲ－ＦＴＩＲ和化学捕获技术（ＣＨ３Ｉ作捕获剂）,探讨了Ｒｈ／ＳｉＯ２催化剂上的ＰＯＭ反应机理,由此提出热分解氧化机理,认为ＣＨｘ（ｘ＝１～３）和ＣＨｘＯ（ｘ＝１～３）可能是反应物种。     

铁助剂对Rh-Mn-Li/SiO2催化剂表面上的CO脱附和CO加氢行为的影响

 采用一氧化碳程序升温脱附（CO－TPD）和吸附的一氧化碳加氢程序升温表面反应（TPSR）考察了Fe助剂对Rh基催化剂上CO的脱附行为及吸附CO的加氢行为的影响．CO－TPD实验表明，在Rh／SiO2催化剂上CO有三个脱附峰．在Rh－Mn－Li／SiO2中加入0．05％Fe后，高温脱附CO比Rh／SiO2催化剂上相应的CO量大．增加Fe的负载量，CO的脱附量减少．TPSR实验中，CO加氢反应的主要产物是甲烷．不同组分的催化剂上甲烷的生成温度有如下顺序：Rh／SiO2（482K）＜Rh－Mn－Li／SiO2（489K）＜Rh－Fe／SiO2（494K）＜Rh－Mn－Li－Fe／SiO2（501K）．甲烷峰的产生伴随着CO（s）高温脱附峰的消失，说明甲烷是由强吸附的CO加氢生成的．     

Mechanistic study of partial oxidation of methane to syngas using in situ time-resolved FTIR and microprobe Raman spectroscopies

In situ time-resolved Fourier transform infrared (FTIR) and microprobe Raman spectroscopies were used to characterize the reaction mechanisms of the partial oxidation of methane to syngas over SiO(2)- and gamma-Al(2)O(3)-supported rhodium and ruthenium catalysts. The interaction of both pure methane and a methane/oxygen mixture at a stoichiometric feed ratio with an oxygen-rich catalyst surface led to the formation of CO2 and H(2)O as the primary products. For the H(2)-pretreated samples, the reaction mechanisms with the catalysts differ. Only Rh/SiO(2) is capable of catalyzing the direct oxidation of methane to syngas, while syngas formation over Rh/gamma-Al(2)O(3), Ru/SiO(2), and Ru/gamma-Al(2)O(3) can be achieved mainly via a combustion-reforming scheme. The significant difference in the mechanisms for partial oxidation of methane to syngas over the catalysts can be correlated to the differences in the concentration of oxygen species (O(2-)) on the catalyst surface during the reaction, mainly due to the difference in the nature of the metals and supports.     

Ir/SiO2上甲烷部分氧化制合成气反应的原位时间分辨红外和原位Raman光谱表征

采用原位时间分辨红外光谱和原位显微Raman光谱技术对Ir/SiO₂上甲烷部分氧化(POM)制合成气反应的初级产物和反应条件下催化剂表面物种进行了跟踪考察,实验结果表明,在H₂预还原的新鲜Ir/SiO₂表面,CO是V(CH₄):V(O₂):V(Ar)=2:1:45混合气反应的初级产物,因而甲烷的直接氧化过程是CO生成的主要途径;而在稳态反应条件下,CO生成的途径可能主要来自CO₂和H₂O与催化剂表面积碳物种(CHx)和/或CH₄的反应.催化剂上生成的积碳可能是导致稳态条件下Ir/SiO₂上POM反应机理不同于H₂预还原的新鲜催化剂的主要原因.     

金属-载体相互作用对CH4/CO2重整反应中Rh基催化剂抗积炭性能的影响

考察了Rh/Al2O3,Rh/SiO2和Rh/CeO2催化剂上金属-载体间相互作用对CH4/CO2重整反应抗积炭性能的影响,并与反应前后催化剂的程序升温还原和程序升温氧化(TPO)测试结果相关联.实验发现,Rh与Al2O3和SiO2载体间的相互作用越强,催化剂还原后Rh的分散度越高,晶粒越小,高分散的Rh表面生成的碳物种CHx越多,其作为活泼的反应中间体越易与CO2反应生成CO和H2.而游离态的Rh还原后晶粒较大,生成的碳物种与CO2反应能力较低,从而导致催化剂失活.TPO和CO2脉冲实验结果表明,反应过程中Rh/CeO2催化剂上反应生成的CHx物种比Rh/Al2O3和Rh/SiO2上的CHx物种更活泼.同时由于Rh-CeO2间独特的相互作用,部分CeO2还原后生成CeO2-x和氧空位,促进CO2分子的活化解离,导致生成的表面氧容易与CHx反应,从而抑制催化剂积炭.     

反应条件对固相合成负载羰基铑原子簇催化剂及其性能的影响

本文报告了由金属盐直接固相合成负载铑络合物或原子簇催化剂的新方法及IR谱表征。CO容易使表面吸附有水分子的RhCl_3/SiO_2还原并生成表面羰基物Rh~+-(CO)_2/SiO_2;CO、CO/H_2和CO/2H_2等不同还原气对表面络合物的生成没有影响。采用H_2还原只能得到金属Rh催化剂。水是重要影响因素,如果RhCl_3/SiO_2先抽空脱水,再用含水的CO还原,就会使Rh~+(CO)_2/SiO_2转化为Rh_6(CO)_(16)/SiO_2。此外,还考察了负载原子簇的CO加氢和热分解反应性能。采用CO还原RhCl_3/SiO_2制备的催化剂同负载原子簇催化剂的反应行为非常相近,而且比传统催化剂具有更高的反应活性。     

Quantum Chemical Studies on the Mechanism of Producing Oxygenates in Fischer-Tropsch Synthesis on M/SiO2(M = Ni,Ru,Rh,Pd)

EHMO calculations and orbital analyses of fragment;;have been performed for the formation of oxygenates in Fischer-Tropsch synthesis on the butterfly model for four different metal (Ni,Ru,Rh,Pd) catalysts supported on SiO2.Calculations were made for the four processes,i.e.,CO-dissociation;Coupling of CO and H to produce CHO;Insertion of CO to M-CH3;insertion of CH2 to M-CH3 On the basis of comparing the degree of CO bonds activation and the energy barriers of the foregoing processes for these four catalysts,it is concluded that Ni/SiO2 can be used as the methanation catalyst.On Ru/SiO2 and Rh/SiO2 C2-oxygenated compound can be produced (acetaldehyde),especially Rh/SiO2 is the even better catalyst,and Pd/SiO2 is a methanol synthesis catalyst.     

Ag/La0.6Sr0.4MnO3基催化剂上CH3OH和CO的完全氧化

合成了Ａｇ／Ｌａ０．６Ｓｒ０．４ＭｎＯ３、Ａｇ／Ｌａ０．６Ｓｒ０．４ＭｎＯ３／γ－ＡＩ２Ｏ３两毓催化剂,发现钙钛矿型Ｌａ０．６Ｓｒ０．４ＭｎＯ３对低浓度ＣＨ３ＯＨ或ＣＯ的完全氧化显示出相当高的催化活性,适量Ａｇ对钙钛矿型Ｌａ０．６Ｓ５０．４ＭｎＯ３基质的修使其对ＣＨ３ＯＨ或ＣＯ完全氧化催化活性获明显提高;在６％Ａｇ／２０％Ｌａ０．６Ｓｒ０．４ＭｎＯ３／γ－ＡＩ２Ｏ３催化剂 ,ＣＨ３ＯＨ完全氧化的Ｔ     

Rh/Al_2O_3-Cr_2O_3整体式催化剂的制备和二氯甲烷催化氧化性能

以粉末Al_2O_3为载体,通过浸渍Rh(NO_3)_3制备Rh/Al_2O_3催化剂;再以Rh/Al_2O_3、粉末Cr_2O_3和铝胶经过研磨混合制得催化剂活性浆料;将催化剂活性浆料涂覆到堇青石蜂窝陶瓷载体表面,经烘干,焙烧制得不同Rh含量的Rh/Al_2O_3-Cr_2O_3系列整体式催化剂.研究了该类催化剂的二氯甲烷催化氧化性能,发现Rh负载量为0.4 g/L的Rh/Al_2O_3-Cr_2O_3催化剂活性最佳,且未生成含氯中间产物.结合催化剂的表征结果发现,Rh的添加可增加催化剂的表面酸性和氧化还原性能,二者的协同作用提高了催化剂活性;而Cr_2O_3的存在有利于CH_3Cl中间体的进一步氧化,从而提高了催化剂的选择性.     

Studies on the Performance and Structure of Supported Catalysts for the Partial Oxidation of Methane to Syngas

The catalytic properties of several supported metal catalysts on different carriers were studied in the partial oxidation of methane (POM) to syngas. In our experiment, supported noble metal catalysts exhibited better performance than the other supported transition metal catalysts. The catalyst performances were significantly influenced by the d-electron configuration of the active metal components and the dispersion of active metal components on the support. A catalyst with a moderate number of unpaired electrons in the d-orbital of the active metal support without obvious acidity or redox activity (e.g. MgO) was suitable for POM performance. The Rh/SiO2 catalyst was the best in the POM reaction, among those investigated. Reaction conditions apparently also affected the POM performance of the catalyst. The conversion of methane and the selectivity for CO increased with the reaction temperature, and a high CH4/O2 ratio was not beneficial for POM performance.     

不同温度烧制介孔碳作为直接甲醇燃料电池催化剂载体

以嵌段共聚物P123为模板制备介孔氧化硅SBA-15, 并以此SBA-15为模板, 以蔗糖为碳源在不同的温度下(600-900 °C)制备介孔碳CMK-3. 采用浸渍还原法, 以硼氢化钠为还原剂, 制备介孔碳载Pt电催化剂, 即20% (w) Pt/CMK-3. 利用循环伏安法(CV)、计时电流法等测试电催化剂对甲醇的催化氧化性能及稳定性. 预吸附单层CO溶出伏安法研究测试催化剂抗CO中毒能力. 结果表明在烧制温度为900 °C时制备的介孔碳载Pt催化剂具有最好的催化性能和稳定性, 而在烧制温度为700 °C时制备的介孔碳载Pt催化剂对CO有较低的溶出电位.     

低浓度甲烷甲醇深度氧化Ag/La0.6Sr0.4MnO3催化剂

用柠檬酸溶胶－凝胶法制备钙钛矿型Ｌａ０．６Ｓｒ０．４ＭｎＯ３氧化物,并用Ａｇ对其进行修饰,制得Ａｇ／Ｌａ０．６Ｓｒ０．４ＭｎＯ３系列催化剂。结果表明,６％Ａｇ／Ｌａ０．６Ｓｒ０．４ＭｎＯ３催化剂上甲烷或甲醇氧化转化９５％时的反应温度Ｔ９５可低至７３５Ｋ（对ＣＨ４）或４２１Ｋ（对ＣＨ３ＯＨ）;适量Ａｇ的负载修饰并不改变催化剂基质氧化物Ｌａ０．６Ｓｒ０．４ＭｎＯ３的纳米级钙钛矿型结构;Ａｇ的掺杂诱使催     

低浓度甲烷甲醇深度氧化Ag/La0.6Sr0.4MnO3催化剂

Ag-modified La0.6Sr0.4MnO3 catalysts were prepared and their catalytic performance for deep oxidation of CH4 and CH3OH at low concentrations were investigated. The results showed that the La0.6Sr0.4MnO3 host catalyst with the perovskite-type nano-crystallite structure displayed considerably high catalytic activity for deep oxidation of CH4 and CH3OH at low concentrations. Ag modification to the La0.6Sr0.4MnO3 host catalyst resulted in significant enhancement of the catalyst activity, making the T95 (the reaction temperature needed for conversion of 95%of CH4 or CH3OH) lowered down to 735K (for CH4) and 421K (for CH3OH) from 813 and 465 K over the Ag-free system under the reaction conditions:0.1MPa,CH4/O2/N2=2/12/86(molar ratio),GHSV=45000 h-1 and CH3OH/O2/N2= 0.2/1.0/98.8 (molar ratio),GHSV=58000 h-1,respectively.The carbon containing product was almost CO2 and the contents of HCHO and CO in the reaction exit gas were both under GC detectable limit in both cases.
The results of spectroscopic characterization indicated that modification by proper amount of Ag-dopant did not change the perovskite structure of the La0.6Sr0.4MnO3 host catalyst as a whole. Interaction of Ag-dopant with the surface of the host catalyst,La0.6Sr0.4MnO3,was in favor of high dispersion of the Ag component at the catalyst surface and led to the oxidation of part of the Mn3+species to Mn4+,resulting in an increase of amounts of the reducible Mnn+ species and a decrease of their reduction temperature. On the other hand, this interaction led also to enhancement of adsorption ability of the catalyst toward O2 at relatively low temperature. High activity of the Ag modified La0.6Sr0.4MnO3 catalyst for CH4 and CH3OH complete oxidation was closely related to high redox-activity of the catalyst and its prominent adsorption-activation ability to O2 at relatively low temperatures.     

Studies on the Performance and Structure of Supported Catalysts for the Partial

The catalytic properties of several supported metal catalysts on different carriers were studied in the partial oxidation of methane (POM) to syngas. In our experiment, supported noble metal catalysts exhibited better performance than the other supported transition metal catalysts. The catalyst performances were significantly influenced by the d-electron configuration of the active metal components and the dispersion of active metal components on the support. A catalyst with a moderate number of unpaired electrons in the d-orbital of the active metal support without obvious acidity or redox activity (e.g. MgO) was suitable for POM performance. The Rh/SiO2 catalyst was the best in the POM reaction, among those investigated. Reaction conditions apparently also affected the POM performance of the catalyst. The conversion of methane and the selectivity for CO increased with the reaction temperature, and a high CH4/O2 ratio was not beneficial for POM performance.     

Ni-Mg-ZrO2催化剂上煤层甲烷三重整制合成气

采用共沉淀法制备Ni-ZrO₂和Ni-Mg-ZrO₂催化剂,用BET、XRD、H₂-TPR、CO₂-TPD等技术对催化剂进行了表征。采用固定床流动反应装置,研究了催化剂在煤层甲烷三重整制合成气反应中的催化性能;考察了反应温度和原料气体组成对反应的影响。实验结果表明,Ni-Mg-ZrO₂催化剂在反应温度800℃、常压、空速为30 000 mL/(g·h)、CH₄/CO₂/H₂O/O₂/N₂=1.0/0.45/0.45/0.1/0.4的条件下,CH₄转化率为99%,CO₂转化率为65%左右,生成合成气H₂/CO体积比为1.5,并在58 h的实验中催化剂活性和稳定性良好。这主要归因于催化剂中金属和载体之间的强相互作用、催化剂的高热稳定性和强碱性。此外,较高的反应温度有利于甲烷三重整反应的进行;通过调节原料气组成,可以获得不同H₂/CO体积比的合成气。     

Ni(OCH3)2/SiO2催化剂的制备及其合成碳酸二甲酯的反应性能

采用表面改性和离子交换相结合的方法，制备了负载型单核金属甲氧基配合物Ni(OCH3)2/SiO2催化剂。利用IR、TPD、TPSR和微反技术，考察了催化剂的表面结构以及CO2、CH3OH在催化剂表面上的化学吸附和反应性能。结果表明，负载型单核金属甲氧基配合物Ni(OCH3)2/SiO2中，Ni^2 与载体SiO2表面的O^2-以双齿形式配位；在催化剂表面存在CO2的桥式吸附态和甲氧碳酸酯基物种两种吸附态，CH3OH则只有一种分子吸附态。在373-473K条件下，CO2和CH3OH在催化剂上的反应物主要是DMC、H2O以及少量的CO、CH4和CH2O，催化剂的活性由表面甲氧碳酸酯基物种与分子吸附态甲醇的反应决定的。讨论了催化剂上CO2和CH3OH的活化过程及吸附态的形成机理。     

Syngas production by combined carbon dioxide reforming and partial oxidation of methane over Ni/α-Al2O3 catalysts

Ni/α-Al2O3 catalysts were found to be active in the temperature range 600~900 ℃ for both CO2 reforming and partial oxidation of methane. The effects of Ni loading, reaction temperature and feed gas ratio for the combination of CO2 reforming and partial oxidation of CH4 over Ni/α-Al2O3 were investigated. Catalysts of xwt%Ni/α-Al2O3 (x = 2.5, 5, 8 and 12) were prepared by wet impregnating the calcined support with a solution of nickel nitrate. XRD patterns and activity tests have verified that the 5wt%Ni/α-Al2O3 was the most active catalyst, as compared with the other prepared catalyst samples. An increase of the Ni loading to more than 5 wt% led to a reduction in the Ni dispersion. In addition, by combining the endothermic carbon dioxide reforming reaction with the exothermic partial oxidation reaction, the loss of catalyst activity with time on stream was reduced with the amount of oxygen added to the feed.