Ni基重整催化剂失活机理研究进展

H₂是一种清洁、绿色的燃料和能源载体。目前工业上应用较为成熟的生产工艺是重整反应制氢。其中,Ni基重整催化剂由于其高储量、高活性和低成本的优点而受到研究人员的广泛关注,但在反应过程中存在易因烧结、积炭和中毒等原因而失活的问题。因此,如何提高Ni基重整催化剂的反应稳定性是一个急需解决的问题。本文介绍了上述三种引起Ni基重整催化剂失活的主要原因,并从调控金属Ni粒子粒径、增强金属-载体相互作用、形成晶格氧或表面氧物种以及Ni粒子纳米结构调控四个方面阐述了近年来在抑制失活并提高Ni基重整催化剂反应性能和稳定性领域所取得的研究进展,并且提出优化反应条件、调变化学组成和调控Ni粒子纳米结构将是提高Ni基催化剂在重整反应过程中的稳定性的有效方法。     

Coking characteristics of reforming catalysts

Coking rates were measured for two different γ-aluminas, each with and without platinum, under near commercial conditions using a gravimetric reactor. Coke on catalyst was characterized by a Temperature-Programmed Oxidation (TPO) technique. With a naphtha feed, coke formed on both aluminas at rates related to the respective population of α-sites as measured by IR. For the corresponding Pt on alumina catalysts, coke, as measured by TPO, predominantly formed on sites associated with alumina (“alumina coke”), while coke associated with Pt (“Pt coke”), was relatively minor. With a n-heptane feed, under the same conditions, coke formation on both aluminas was much less than with the naphtha feed. However, the corresponding Pt on alumina catalysts generated comparatively more coke with a higher proportion associated with Pt. A correspondence between this proportion of “Pt coke” and the decline in reforming activity was observed. It is postulated that most of the coke produced during naphtha reforming with an active catalyst is formed by a reaction between α-sites on alumina and certain components in the feed via a polymerization mechanism. This type of coke has minimal effect on the reforming reactivity of the catalyst. However, in n-heptane reforming, about 50% of the coke also results from precursors formed from reactions with Pt. In either case, coke associated with Pt appears to be the probable cause of deactivation.     

重整催化剂硫中毒的工业再生处理

针对中国石化沧州分公司150 kt·a^－1催化重整装置的3932和3933两种重整催化剂两次硫中毒的工业再生处理,阐述了重整催化剂硫中毒工业处理方法。两次再生效果的对比表明,提高热氢除硫操作温度是保证催化剂再生效果的关键。     

Cracking properties of some reforming catalysts

The cracking properties of industrial reforming catalysts of γ-alumina loaded with 0.6% Pt, with 0.35% Pt, and with 0.35% Pt plus promoters were investigated. The mode of cracking of these catalysts was studied after treatment under different oxidation and reducing atmospheres. Cumene cracking was used as a model reaction. The cracking products were collected and analysed, and the quantity of benzene produced was used to compare the activities of these catalysts. Maximum cracking was observed around 550°C for all catalysts studied. Cracking rates differed for various treatment conditions for the same catalyst, normally increasing after oxidation treatment. Marked changes in the cracking activity of unloaded γ-alumina were observed after it was chlorinated. Benzene yield was studied in relation to possible complex formation of Pt-Al₂O₃-Cl₂.     

Exhaust-gas reforming using precious metal catalysts

Rh-only and Rh bimetallic catalysts have been screened for exhaust-gas reforming, under conditions that mimic the output of an autoignition gasoline engine. Propane has been used as a model fuel, with simulated exhaust-gas providing the co-reactants (O₂ and H₂O) needed to generate hydrogen. Based on oxygen-conversion as a measure of light-off, Pt–Rh on ceria–zirconia shows the highest activity. In the presence of SO₂, adsorbed sulphur species do not inhibit the oxidation reactions that induce light-off, but suppress the major pathway to hydrogen (steam reforming). By excluding platinum and using silica-enriched alumina as the underlying support, light-off is delayed, but the steam reforming reaction becomes much more insensitive to the presence of sulphur. The Pt–Rh catalyst is most suited to exhaust-gas reforming systems in which the engine runs on a sulphur-free fuel, whereas the Rh-only catalyst is the better choice when the fuel is conventional gasoline.     

Industrial operation experience of PR reforming catalysts

The industrial operation experience of Russian PR reforming catalysts in Russian and Ukrainian refineries was summarized. The comparative industrial application efficiency analysis of developed PR reforming catalysts and their imported analogues was provided for different refineries. For the first time, the results showed the higher efficiency of the PR-71 catalyst used in radial reactors with alternated raw gas flow direction.     

Development of ultra-stable Ni catalysts for CO2 reforming of methane

Carbon deposition behavior in CO₂ reforming of methane, methane decomposition, and CO disproportionation on nickel-magnesia solid solution was investigated by means of thermogravimetric analysis and temperature programmed reaction of deposited carbon with carbon dioxide. It was found that rapid oxidation of CH_x on Ni surface by oxygen species from CO₂ through dissociation at metal-support interface is a key step for the inhibition of carbon formation.     

Olivine catalysts for methane- and tar-steam reforming

The removal of tar and lower hydrocarbons is a vital technological barrier hindering the development of biomass gasification. The present work evaluates four olivine catalysts (three untreated of different origin and one calcined) for lowering the amount of these compounds in biomass derived syngas by reforming model compounds (naphthalene, toluene, and methane). Treatments prior to reaction were shown to largely impact the catalytic activity and physiochemical properties of the olivine catalysts depending on its origin. The formation of free Fe phases following decomposition of a Fe-bearing serpentine phase ((Mg,Fe)₃Si₂O₅(OH)₄) near the surface of untreated olivine catalysts proved most important for facilitating higher activity compared to olivine catalysts with little or no serpentine phase initially. The most active catalyst was efficient at naphthalene removal (90% conversion at 800 °C), but more active catalysts are needed for applications where methane removal is required. Additionally, carbon deposition during naphthalene-steam reforming as well as Fe clustering during naphthalene-steam reforming and exposure to reducing conditions suggested stability may be a liability.     

甲醇氧化重整催化剂的研究

制备并优选了甲醇氧化重整的催化剂 ,实验表明在相同的温度下 ,Pd催化剂、Cr2 O3 ZnO氧化物催化剂和Cu催化剂相比 ,活性、选择性以及氢产率都表现为Cu >Cr Zn >Pd。其中 ,Cu催化剂在低温时、Cr Zn催化剂在高温下表现出良好的活性和选择性 ,而且Cr Zn催化剂的热稳定性较好     

UOP公司催化重整催化剂专利技术分析

对UOP公司催化重整催化剂领域相关专利进行了检索,从专利申请趋势、技术区域分布、专利技术布局和在中国专利申请情况等方面对其专利技术进行分析。UOP公司在催化重整催化剂领域进行了大量的研究工作,自1943年开始在该领域申请专利,并不断加强其在世界主要国家的专利布局,在美国和中国等10 余个国家申请了相关专利,专利技术主要涉及含分子筛催化剂、含贵金属催化剂和分子筛催化剂等制备技术。UOP公司催化重整催化剂专利技术的研发主要集中在铂基多金属催化剂的优化、催化剂载体性能的进一步提高以及新助剂的研究,目前主要是通过对不同类型和含量的助金属进行研究,研发高活性、高产率、高选择性、低生焦、抗磨性能好的催化重整催化剂,其催化剂呈现系列化发展。     

Progress in the sulfur resistance of reforming catalysts

Hydrocarbon in-situ reforming hydrogen supply technology based on solid oxide fuel cell (SOFC) is an important distributed and miniaturized hydrogen production solution. Traditional nickel-based reforming catalysts often face sulfur poisoning during the reaction with trace amount of sulfur in the feedstock. In some cases, the existing sulfur may even cause severe safety risks. In this paper, the mechanisms of sulfur poisoning are summarized; the compositions and contents of sulfur species in natural gas, liquefied petroleum gas and liquid hydrocarbon are briefly described; the reported sulfur resistant catalysts for different reforming reactions are reviewed, and the effective and feasible solutions for developing sulfur-tolerant catalysts are summarized. The mechanisms of sulfur poisoning could guide the design of sulfur-resistant reforming catalyst with high performance. Finally, the paper reveals that the improvement of catalytic overall performance, the pretreatment of reforming feedstock and the design of reforming reactor and other comprehensive anti-sulfur strategies are also important research directions.     

Combined reforming of methane over supported Ni catalysts

The hydrogen exchange for propane-d ₈ adsorbed on zeolite Zn/H-MFI has been studied by¹H MAS NMR spectroscopy in situ within the temperature range of 420–490 K. Kinetic measurements of the H/D exchange between the acidic hydroxyl groups of the zeolite and the adsorbed deuterated propane molecules show that only methyl groups of the alkane are involved in the exchange. Two mechanisms are proposed to rationalize the regioselectivity of the exchange: (i) propane dehydrogenation on Zn-sites followed by protonation of propene by acidic OH groups in accordance to the Markovnikov’s rule and abstraction of deuteride ion from another propane molecule; (ii) the reversible heterolytic dissociative adsorption of propane to form Zn-propyl species and acidic OH groups.     

重整催化剂的抗硫性能研究进展

基于固体氧化物燃料电池(SOFC)的烃类原位重整供氢技术是重要的分布式和小型化制氢方案。传统镍基重整催化剂在烃类重整过程中,原料中微量的硫化物即可使催化剂中毒失活,严重时还可能造成巨大的安全隐患。本文梳理总结了催化剂硫中毒的机理,简述了天然气、液化石油气、液态烃重整原料中硫化物的组成和含量,重点分析了已报道的用于重整反应的抗硫催化剂并总结了有效可行的催化剂抗硫方案,并从重整制氢催化剂的硫中毒机理指导高效抗硫催化剂的开发。最后,文章指出,重整催化综合性能的提升、重整原料的预处理和重整反应器设计等综合抗硫策略也是重要的研究方向。     

Role of metallic tin in PtSn reforming catalysts

Metallic tin was detected using X-ray photoelectron spectroscopy (XPS) after H₂ reduction of 5%Pt/SnO₂, 5%Pt-5%Sn/SiO₂, and 5%Pt-29%Sn/Al₂O₃. However, no metallic tin could be detected in PtSn/Al₂O₃ catalysts with tin loadings up to 5 wt%. These findings indicate that tin reducibility depends on the extent of interaction between SnO _x and the substrate. Hexane reaction studies indicate that metallic tin poisons all reforming reaction channels regardless of the support.     

Metathesis probes of Re promoters on reforming catalysts

Propene metathesis results show conclusively that a significant fraction of the Re is in a positive oxidation state in EUROCAT-4 (0.3% Re/0.3% Pt/alumina) pre-treated in H₂ to 673 K, and, since some of the product (and reactant) alkenes are self-hydrogenated the zero-valent Pt component is not entirely encapsulated in this Re _x O _y .     

Investigation of bio-ethanol steam reforming over cobalt-based catalysts

The catalytic performance of cobalt catalysts supported on γ-Al₂O₃, TiO₂, ZrO₂ were studied for bio-ethanol steam reforming (BESR) reaction. The supported catalysts (10 wt%Co) were prepared by impregnation and characterized through Thermogravimetric analysis (TGA), H₂ chemisorption, laser Raman Spectroscopy, Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS), and temperature-programmed reaction (TPRxn). The metallic cobalt sites were found to correlate with the BESR reaction activity. The reaction and H₂ chemisorption showed that ZrO₂ supported catalyst showed the best dispersion and best catalytic activity. Over the 10% Co/ZrO₂ catalyst, using a H₂O:EtOH:inert molar ratio of 10:1:75 and a GHSV = 5000 h⁻¹, 100% ethanol conversion and a yield of 5.5 mol H₂/mol EtOH were obtained at 550 °C and atmospheric pressure.     

SHS-produced Ni-Co-Al-Mg-O catalysts for dry reforming of methane

Oxide catalysts Ni-Co-Al-Mg-O, Ni-Al-Mg-O, Co-Al-O, and Co-Mg-O have been prepared by combustion synthesis and characterized by XRD, Fourier transform IR spectroscopy (FTIR), SEM/EDS, TEM, and nitrogen porosimetry. Their catalytic activity in the process of dry (carbon dioxide) reforming of methane was studied by gas chromatography at different temperatures. Feed gas contained equal amounts of methane, carbon dioxide, and nitrogen and the effect of catalyst composition and temperature on the catalytic activity, selectivity, and product yields were recorded.