Fe2+/H2O2体系O2生成路径

掌握Fe²⁺/H₂O₂体系O₂的生成路径,可为避免H₂O₂无效分解,开发经济高效的Fe²⁺/H₂O₂体系利用技术指明方向。采用添加自由基捕获剂的方法,探究Fe²⁺/H₂O₂体系内各种自由基对O₂生成速率的影响,进而确定O₂的生成路径。结果表明:Fe²⁺/H₂O₂体系内不会产生大量O₂^-·,O₂^-·不是生成O₂的主要反应物质;O₂^-·被全部捕获后,体系中仍产生大量O₂^-·,但此时无O₂生成,证明生成O₂的反应由·OH和HO₂·两种自由基直接参与。分析认为反应·OH+HO₂·-H₂O+O₂是体系内O₂生成的主要路径。控制Fe²⁺/H₂O₂体系定向生成·OH,抑制HO₂·的产生,是提高Fe²⁺/H₂O₂体系中H₂O₂利用率的有效手段。     

不同物相TiO2对H2O2/O3氧化效能的影响

研究了不同物相TiO₂对H₂O₂/O₃氧化效能的影响,目标有机物为羟基自由基探针化合物乙酸。结果表明,在初始pH为7.0和10.0时,加入TiO₂反而降低了H₂O₂/O₃的氧化效率,其中锐钛矿TiO₂比金红石TiO₂的减弱作用更为明显。当初始pH为3.0时,金红石TiO₂能显著提高H₂O₂/O₃的氧化效率,但锐钛矿TiO₂影响不明显。机理分析表明,H₂O₂浓度及其衰减速率与乙酸的去除效率有很大的相关性。在pH为7.0和10.0时,两种物相TiO₂均能加快H₂O₂的分解,其中锐钛矿TiO₂作用更为显著。此条件下HO₂^-能有效引发臭氧分解产生羟基自由基,故H₂O₂过快分解反而降低了乙酸的去除效果。在pH为3.0时,H₂O₂去质子化反应困难,故O₃/H₂O₂氧化效率极低,H₂O₂浓度也几乎不变。加入TiO₂能明显提高H₂O₂的分解速率,相比金红石TiO₂,锐钛矿TiO₂使H₂O₂在5 min内基本分解完毕,但其对H₂O₂/O₃氧化效率几乎没有影响。饱和臭氧水分解速度的批处理实验也有相似的结果。由此可见,合适引发剂浓度可能是保证臭氧类高级氧化技术较高效率的关键,否则只会导致氧化剂的无效过快分解。利用氯化硝基四氮唑蓝法对比分析了酸性条件下H₂O₂/O₃、锐钛矿TiO₂/H₂O₂/O₃和金红石TiO₂/H₂O₂/O₃体系产生超氧自由基(·O₂^-)的量,其大小顺序为:H₂O₂/O₃< 金红石TiO₂/H₂O₂/O₃< 锐钛矿TiO₂/H₂O₂/O₃,这与前面结果吻合很好。     

Generation of H2O2 from H2 and O2 over zeolite beta containing Pd and heterogenized organic compounds

The catalytic generation of H₂O₂ from H₂ and O₂ has been studied over zeolite beta-supported Pd and zeolite beta-adsorbed organic compounds such as 1,4-benzoquinone (BQ), hydroquinone (HQ), azobenzene (AB) and hydrazobenzene (HAB). According to catalytic results, zeolite beta-supported Pd catalysts display effective performance relative to those prepared from other types of zeolites reported and Pd-loaded zeolite beta-adsorbed HQ catalysts show enhanced activity compared to zeolite beta-supported Pd catalysts. In situ UV–Vis spectroscopic study indicates that HQ can readily be converted to BQ reversibly under H₂ and air inside zeolite beta only in the presence of Pd. The results suggest that HQ acts as a strong hydrogen transfer agent to promote the production of H₂O₂ from H₂ and O₂ in cooperation with a Pd catalyst. By contrast, adsorption of BQ, AB and HAB induces suppression of the catalytic properties of Pd/zeolite beta.     

Fe2+/H2O2体系内各种自由基在氧化NO中的作用

Fe²⁺/H₂O₂体系可分解产生多种氧化性自由基, 主要包括O₂^-·、·OH和HO₂·。本文实验研究了O₂^-·、·OH及HO₂·在Fe²⁺/H₂O₂体系氧化NO气体过程中的作用。结果表明:在本实验条件下, O₂^-·对NO气体的氧化作用不明显;·OH及HO₂·是该体系氧化NO气体的主要活性物质, 其中·OH的氧化作用更大。加快自由基的生成速率可以增强Fe²⁺/H₂O₂体系对NO气体的氧化能力, 但O₂的生成速率同时加快。只有少量·OH及HO₂·参与NO的氧化, ·OH与HO₂·之间的快速反应是Fe²⁺/H₂O₂体系氧化NO过程中H₂O₂利用率低的主要原因。     

A first-principles study of reaction mechanism over carbon decorated oxygen-deficient TiO2 supported Pd catalyst in direct synthesis of H2O2

The choice of support is one of the most significant components in the direct synthesis of H₂O₂. Aiming to improvement of activity and selectivity of H₂O₂ on Pd/TiO₂ surface, we systematically investigated the important elementary steps on Pd/TiO₂-Vo@C, Pd/TiO₂-Vo, Pd/TiO₂-2Vo, Pd/TiO₂, and Pd/C using the first-principles calculations. The Bader charge analysis and charge density difference of O2 adsorption elucidate the relationship between the electronic distribution and chemisorption energy. The effective barrier analysis further enables to quantitatively estimate the reactivity of H₂O₂ and H₂O. We demonstrate unambiguously that the selectivity of H₂O formation is boosted as the oxygen vacancy concentration raised. Moreover, the introduction of C into a TiO₂ with appropriate oxygen vacancies can slightly reduce the effective barrier for H₂O₂ formation and increase the effective barrier for H₂O formation leading to a higher activity and selectivity of H₂O₂ formation. Our finding suggests that carbon-doped oxygen vacancy TiO₂ supported Pd is potential alternative catalyst compared with the Pd/TiO₂.     

微波热解制备g-Fe2O3催化剂及其SCR脱硝性能

以FeSO₄·7H₂O[Fe(NO₃)₃·9H₂O]为铁源,采用新型微波热解法制备γ-Fe₂O₃[a-Fe₂O₃]催化剂样品,通过XRD、N₂等温吸附-脱附、压汞法等实验手段对催化剂样品晶相、微观孔结构等进行表征;考察两种催化剂样品的NH₃-SCR脱硝性能,通过归一化处理得到两种催化剂在不同温度下的本征脱硝反应速率,同时对比研究了γ-Fe₂O₃与钒系催化剂的脱硝活性;研究氨氮比、氧浓度等运行参数对γ-Fe₂O₃催化剂NH₃-SCR脱硝性能的影响规律,并对其抗硫抗水性能进行考察.结果表明:采用新型微波热解法可得到纯度较高的γ-Fe₂O₃催化剂,其介孔分布合理且大孔数量丰富;同时γ-Fe₂O₃催化剂表现出优于a-Fe₂O₃催化剂的脱硝性能,400℃时最大NO_x转化率达到96%,300、325、350℃下单位面积脱硝速率达到a-Fe₂O₃催化剂的3倍左右;γ-Fe₂O₃催化剂具备优良的抗硫抗水性能,其最佳氨氮比为1、最佳氧体积分数为3.5%.     

双膜强化类Fenton工艺处理制浆废水的研究

类Fenton工艺又称非均相Fenton工艺,主要用于降解废水COD,可避免传统Fenton工艺产生的铁泥问题,但双氧水利用率尚有待提高。采用1个陶瓷膜分布H₂O₂,另1个陶瓷膜分离催化剂,构成双膜促进的非均相Fenton新工艺,考察了不同催化剂对制浆废水中COD的降解效果,优化了H₂O₂进料速率和反应渗透通量,分析了催化剂的稳定性和陶瓷膜污染情况。结果表明,自制立方体结构的Cu₂O对制浆废水中COD降解效果最佳,当Cu₂O添加量为1 g·L^-1,H₂O₂加入量为0.8 ml·L^-1,反应温度为30℃,反应渗透通量为137 L·m^-2·h^-1时,RO（Ⅰ）～RO（Ⅳ）4种废水的COD降解量分别为11、130、291和417 mg·L^-1,H₂O₂的利用率分别为9%、106%、232%、334%,H₂O₂利用率大于100%的主要原因是废水中大量的氯离子与铜催化剂作用产生氯自由基参与了降解反应,COD降解量与Cl-含量呈现线性关系,并且COD降解率随膜渗透通量的减小而增大。360 min的连续运行表明陶瓷膜分布器在非均相Fenton反应过程中会形成可逆滤饼层,膜污染较小,COD降解率稳定保持在65%以上。随着制浆废水中盐浓度的增大,Cu₂O催化剂稳定性变差,Cu离子的溶出量增大。陶瓷膜可以强化非均相Fenton工艺处理制浆废水效果,提高双氧水的利用率和连续运行的稳定性。     

H4SiW12O40/SiO2催化正丁醛自缩合反应

正丁醛自缩合合成辛烯醛是工业生产辛醇的重要步骤之一。首先考察了3种杂多酸H₃PW₁₂O₄₀、H₄SiW₁₂O₄₀和H₃PMo₁₂O₄₀对正丁醛自缩合反应的催化性能,发现H₄SiW₁₂O₄₀的催化性能最好。其次,利用浸渍法制备了负载型H₄SiW₁₂O₄₀催化剂,考察了载体和制备条件对催化剂性能的影响,确定以SiO₂为载体,H₄SiW₁₂O₄₀负载量为50%（质量分数）,在150℃焙烧2 h的制备条件。探讨了反应条件对催化剂性能的影响,确定了适宜反应条件：催化剂与正丁醛的质量比为0.15,反应温度120℃,反应时间6 h。在此条件下,正丁醛的转化率为90.4%,辛烯醛的选择性为89.2%。通过对催化剂进行ICP-AES分析和XRD表征,发现活性组分流失是造成催化剂稳定性差的主要原因。为减缓H₄SiW₁₂O₄₀的流失,以[emim]BF₄离子液体为模板剂,采用溶胶-凝胶法制备了H₄SiW₁₂O₄₀/SiO₂催化剂,实验结果表明,催化剂稳定性有一定程度的提高。     

Complete oxidation of methane at low temperature over Pt and Pd catalysts for the abatement of lean-burn natural gas fuelled vehicles emissions: influence of water and sulphur containing compounds

The catalytic activity of fresh Pd and Pt catalysts supported on γ-alumina in the complete oxidation of CH₄ traces under lean-burn conditions was studied in the presence or the absence of water or H₂S. Steam-aged catalysts were also studied in order to simulate long-term ageing in real lean-burn natural gas fuelled vehicles (NGVs) exhaust conditions. Without water or H₂S added to the feed, Pd catalysts exhibit a superior catalytic activity in methane oxidation compared to Pt ones, whatever the catalysts were fresh or aged. The addition of 10 vol.% water vapour to the feed strongly affects the activity of the fresh Pd catalyst, thus being only slightly more efficient than the fresh Pt one. H₂S has a strong poisoning effect on the catalytic activity of Pd catalysts, while Pt catalysts are more resistant. The fresh H₂S-poisoned Pd/Al₂O₃ catalyst was studied by TPD in O₂/He. Poisoning species decompose above 873 K as SO₂ and O₂ in relative concentrations consistent with the decomposition of surface sulphate species. However, a treatment in O₂/He at temperatures as high as 923 K does not allow the complete regeneration of the catalytic activity of H₂S-poisoned Pd/Al₂O₃. A mechanism involving the poisoning of PdO by sulphate species is proposed. Different diffusion processes by which these sulphate species can migrate back and forth between PdO and the support, depending on the experimental conditions, are suggested.     

Nb2O5 promoted Pd/AC catalyst for selective phenol hydrogenation to cyclohexanone

Phenol hydrogenation is a green route to prepare cyclohexanone, an intermediate for the production of nylon 66 and nylon 6. The development of high-performance catalysts still keeps a great challenge. Herein, the activated carbon (AC) was modified with an acidic material Nb₂O₅ to adjust the microstructure and surface properties of AC, and the influences of the calcination temperature and Nb₂O₅ content on the catalytic performance of the Pd/AC-Nb₂O₅ catalysts for the phenol hydrogenation to cyclohexanone were investigated. The Nb₂O₅ with proper content can be highly uniformly distributed on the AC surface, enhancing the acidity of the Pd/AC-Nb₂O₅ catalysts with comparable specific surface area and Pd dispersion, thereby improving the catalytic activity. The hybrid Pd/AC-10Nb₂O₅-500 catalyst exhibits the synergistic effect between the Pd nanoparticles and AC-10Nb₂O₅, which enhances the catalytic activity for the hydrogenation of phenol. Furthermore, the as-prepared Pd/AC-10Nb₂O₅-500 catalyst shows good reusability during 7 reaction cycles.     

Membrane enhanced COD degradation of pulp wastewater using Cu2O/H2O2 heterogeneous Fenton process

Both activity and stability of the catalyst can be improved in heterogeneous Fenton reaction, in particular, with no limitation for the working pH and no production of the sludge. In this work, a combination of catalyst Cu₂O and pore-channel-dispersed H₂O₂ is proposed to treat the pulp wastewater. Degradation degree of CODs in the wastewater was up to 77% in the ceramic membrane reactor using Cu₂O powder (2.0 g·L^-1) and membranefeeding H₂O₂ (0.8 ml·L^-1) within 60 min. Evolution of ·OH radical formation in the advanced oxidation process was analyzed with a fluorescent method. Utilization efficiency of H₂O₂ was successfully enhanced by 10% with the membrane distributor. Further on, the catalyst recyclability was evaluated in a five-cycle test. The concentration of copper ions being dissolved in the treated water was monitored with ICP. After Cu₂O/H₂O₂ (membrane) treatment the effluent is qualified to discharge with COD concentration lower than 15 mg·L^-1 with regard to the national standard GB25467-2010.     

The role of lanthana loading on the catalytic properties of Pd/Al2O3-La2O3 in the NO reduction with H2

The role of La₂O₃ loading in Pd/Al₂O₃-La₂O₃ prepared by sol–gel on the catalytic properties in the NO reduction with H₂ was studied. The catalysts were characterized by N₂ physisorption, temperature-programmed reduction, differential thermal analysis, temperature-programmed oxidation and temperature-programmed desorption of NO.

The physicochemical properties of Pd catalysts as well as the catalytic activity and selectivity are modified by La₂O₃ inclusion. The selectivity depends on the NO/H₂ molar ratio (GHSV = 72,000 h⁻¹) and the extent of interaction between Pd and La₂O₃. At NO/H₂ = 0.5, the catalysts show high N₂ selectivity (60–75%) at temperatures lower than 250 °C. For NO/H₂ = 1, the N₂ selectivity is almost 100% mainly for high temperatures, and even in the presence of 10% H₂O vapor. The high N₂ selectivity indicates a high capability of the catalysts to dissociate NO upon adsorption. This property is attributed to the creation of new adsorption sites through the formation of a surface PdO_x phase interacting with La₂O₃. The formation of this phase is favored by the spreading of PdO promoted by La₂O₃. DTA shows that the phase transformation takes place at temperatures of 280–350 °C, while TPO indicates that this phase transformation is related to the oxidation process of PdO: in the case of Pd/Al₂O₃ the O₂ uptake is consistent with the oxidation of PdO to PdO₂, and when La₂O₃ is present the O₂ uptake exceeds that amount (1.5 times). La₂O₃ in Pd catalysts promotes also the oxidation of Pd and dissociative adsorption of NO mainly at low temperatures (<250 °C) favoring the formation of N₂.     

Cu/Al2O3催化剂用于H2O2分解生成羟基自由基的效率

非均相Fenton催化反应是降解废水中有机污染物的有效方法。提高H₂O₂分解生成羟基自由基（·OH）的利用率是提升废水处理效率、降低成本的关键。使用溶胶-凝胶法制备了Cu/Al₂O₃催化剂,基于·OH的生成效率,通过单因素实验发现反应温度、反应溶液pH及H₂O₂初始浓度是决定H₂O₂利用率的主要因素。通过响应面法进行实验设计,分析响应面方程,考察了H₂O₂初始浓度、溶液pH及反应温度三个因素之间的交互作用及其对反应过程的影响。以H₂O₂利用率的最大化为目标优化反应条件,当H₂O₂初始浓度、溶液pH及反应温度分别为707 mg·L^-1、5.12及59.4℃时,H₂O₂利用率可高达0.57,与实验结果相对误差仅为3.5%。所得结果对降低废水处理成本、提高降解效率具有重要的指导作用。     

非热等离子体协同Mn-Ce/La/γ-Al2O3催化剂去除甲苯

采用自制线管式介质阻挡放电反应器,针对非热等离子体协同Mn-Ce/La/γ-Al₂O₃催化剂对低浓度甲苯的去除开展研究。研究中制备了Mn/γ-Al₂O₃、Mn-Ce/γ-Al₂O₃、Mn-La/γ-Al₂O₃催化剂,从甲苯去除率、产物O₃生成、CO_x选择性及其他副产物生成情况考察比较了空管放电、协同催化剂放电时催化降解甲苯性能,并对催化剂进行了BET、SEM、H₂-TPR和ICP-OES表征研究。结果表明：稀土助剂的加入有助于提高甲苯去除率及降低程度,且La催化性能优于Ce_.,当外加电压22 kV、气量6 L·min^-1、甲苯初始浓度600 mg·m^-3时,Mn-La/γ-Al₂O₃催化剂对甲苯去除率达到72.74%。H₂-TPR结果表明,稀土助剂的加入提高了催化剂低温活性及储氧能力,添加La的效果优于Ce。催化剂有助于抑制副产物O₃生成,提高CO₂和CO_x选择性。     

宽pH条件下Mn3O4/ACF复合阴极类电芬顿体系降解亚甲基蓝

用电化学方法将Mn₃O₄负载于活性炭纤维（activated carbon fiber,ACF）表面制备了Mn₃O₄/ACF复合阴极,与铂丝阳极构成了异相类电芬顿体系对模型污染物亚甲基蓝（MB）进行降解,考察了该体系在不同pH条件下对MB去除率,并对体系中的活性氧物种进行了检测,初步探讨了降解机理。实验结果表明,在pH 3.0、pH 5.0和pH 7.0时亚甲基蓝脱色率分别达到97.3%、99.9%、99.8%,pH5.0时TOC去除率达到88.6%,pH 7.0和pH 3.0时也分别达到了80.4%和73.4%,拓宽了电芬顿反应的适宜pH范围。体系中活性氧物种的检测结果表明,氧在阴极电还原产生H₂O₂,并与Mn₃O₄反应生成羟基自由基·OH,同时,氧的一电子还原产物超氧自由基O₂·^-也对阴极表面污染物的脱色有重要贡献。     

复合催化剂ZnFe2O4/FeVO4的制备及光催化性能

为了降解污水中的有机染料,对复合催化剂ZnFe₂O₄/FeVO₄光降解有机染料进行了研究,以促进水中生物的健康生长和整个生态系统的平衡。通过聚乙烯吡咯烷酮(PVP)辅助水热法制备出了ZnFe₂O₄,通过水热法制得了FeVO₄,并按照ZnFe₂O₄和FeVO₄不同质量比合成了复合催化剂ZnFe₂O₄/FeVO₄。以甲基橙为降解染料,在相同条件下对ZnFe₂O₄、FeVO₄和复合催化剂ZnFe₂O₄/FeVO₄进行活性对比实验,结果表明,所合成的复合催化剂ZnFe₂O₄/FeVO₄是一种高效率催化剂。通过扫描电子显微镜(SEM)分析,可以看出ZnFe₂O₄和FeVO₄复合在了一起。在加入H₂O₂的条件下反应20 min,ZnFe₂O₄和FeVO₄对甲基橙的降解率分别为15%和25%,而复合催化剂ZnFe₂O₄/FeVO₄对甲基橙的降解率可以达到75%。此外,以ZnFe₂O₄/FeVO₄为样品考察了催化剂用量、H₂O₂浓度和pH值对催化活性的影响,结果表明,ZnFe₂O₄/FeVO₄样品的最佳催化条件为:溶液pH=5.0、H₂O₂浓度为0.044 mol/L、催化剂用量为1.0 g/L。     

H2O2强化光催化处理苯胺化工废水的应用试验

研究者在苯胺模拟废水高级氧化处理方面开展了很多研究,但针对炼化企业苯胺装置废水含盐高、色度高、COD降解难等问题尚未开展工程应用。为解决苯胺生产废水的实际问题,本研究开展了TiO₂/UV-H₂O₂氧化降解苯胺废水（1~2m³/h）的现场试验研究。考察了苯胺废水在单独TiO₂/UV、单独H₂O₂氧化及TiO₂/UV-H₂O₂协同作用下的处理效果,提出了苯胺废水的最佳处理工艺方案,并进行了成本核算。结果表明,单独TiO₂/UV和单独H₂O₂氧化对苯胺废水的脱色率和COD去除率偏低,而TiO₂/UV-H₂O₂协同作用时苯胺废水脱色率和COD去除率可达95%以上。协同氧化体系中,H₂O₂的氧化降解作用显著,H₂O₂投加量1%~2%;酸性条件利于苯胺废水的降解,特别是pH=3.8~4.2时;TiO₂/UV和H₂O₂协同作用一段时间后,停止UV而凭借残余H₂O₂可以将体系中的中间产物继续降解直至矿化成CO₂。TiO₂/UV- H₂O₂协同处理炼化企业苯胺生产废水,出水COD≤60mg/L,色度≤20倍,单位能耗约18.44kW·h/m³,明显低于文献报道值,具有显著的技术性与经济性。     

Fe3O4协同H2O2气相高级氧化单质汞的机理

利用密度泛函理论分别研究了H₂O₂分子在Fe₃O₄（111）、（110）和（001）表面分解特性,并对单质汞在H₂O₂/Fe₃O₄体系的反应特性进行了研究。对比不同构型的结合能、Mulliken电荷转移和分态密度分析,详细讨论了H₂O₂分解产生羟基的规律以及Hg⁰的氧化态中间产物成键特性。结果表明：H₂O₂分子在Fe₃O₄（111）、（001） A和（110） A表面更容易分解产生羟基;不同表面产生的羟基对Hg⁰具有不同的氧化活性;Hg⁰在表面羟基的作用下可有效通过电荷转移实现氧化。对比分析了三种表面汞氧化态中间产物的脱附路径,HO-Hg-OH和Hg-OH的表面脱附是主要的反应路径。     

磷钨酸掺杂二氧化钛光催化剂的吸附性能及光催化活性

以钛酸四丁酯和无水乙醇为原料,采用溶胶-凝胶法制备了磷钨酸掺杂二氧化钛(H₃PW₁₂O₄₀-TiO₂)光催化剂,并利用XRD、SEM、DRS等对掺杂前后二氧化钛的结构进行了表征。在光催化实验初期的暗反应之后,发现H₃PW₁₂O₄₀-TiO₂光催化剂的吸附效果很好。对H₃PW₁₂O₄₀-TiO₂光催化剂的吸附性能进行了研究,结果表明,相比于Freundlich方程,Langmuir方程能更好地描述其吸附平衡。H₃PW₁₂O₄₀-TiO₂光催化剂与纯TiO₂相比有更好的吸附性能,吸附时间为70 min的条件下H₃PW₁₂O₄₀-TiO₂对亚甲基蓝(MB)的脱色率可达90%以上。通过自行设计的光催化反应器考察了光催化剂用量、磷钨酸掺杂量等因素对光催化降解MB性能的影响。结果表明:H₃PW₁₂O₄₀-TiO₂在紫外和可见光区域有较强的吸收,对MB溶液具有更好的光催化降解效果,而且该复合材料有较高的循环回收利用率。     

Enthalpy recovery of gases issued from H2 production processes: Activity and stability of oxide and noble metal catalysts in oxidation reaction under highly severe conditions

Oxidation activity and stability under reaction was investigated for a series of mixed oxide catalysts, doped or not by a precious metal (Pd, Pt). The reaction feedstock, containing CO, H₂, CH₄, CO₂ and H₂O, simulated gases issued from H₂ production processes for fuel cells. Contrarily to conventional noble metal catalysts, mixed oxide samples present generally good stability under reaction at high temperature. The activities measured for the perovskite and hexaaluminate catalysts, are however largely lower than that of the reference Pd/Al₂O₃ catalyst. High activities were obtained after impregnation of 1.1 wt.% Pd or 0.8 wt.% Pt on the hexaaluminates samples. Even if Pd/Al₂O₃ was found to present a high activity, this sample suffered from drastic deactivation at 700 °C. Better stability were obtained on perovskite. Furthermore, doping hexaaluminate by Pt led to samples with good activities and high stability. Even if better activities were obtained by doping the hexaaluminate samples by Pd, the Pd/BaAl₁₂O₁₉ strongly deactivated, as it was previously observed for the reference catalyst. Interestingly, this Pd deactivation was not observed when Pd was impregnated on the Mn substituted hexaaluminate, leading to a stable and active catalyst. This suggests that it is possible to stabilize the palladium in its oxidized form at high temperature (700 °C) on the surface of some supports.