Kinetics of steam regeneration of SAPO-34 zeolite catalyst in methanol-to-olefins (MTO) process

Methanol-to-olefins(MTO) is industrially applied to produce ethylene and propylene using methanol converted from coal,synthetic gas,and biomass.SAPO-34 zeolites,as the most efficient catalyst in MTO process,are subject to the rapid deactivation due to coke deposition.Recent work shows that steam regeneration can provide advantages such as low carbon dioxide emission and enhanced light olefins yield in MTO process,compared to that by air regeneration.A kinetic study on the steam regeneration of spent SAPO-34 catalyst has been carried out in this work.In doing so,we first investigated the effect of temperature on the regeneration performance by monitoring the crystal structure,acidity,residual coke properties and other structural parameters.The results show that with the increase of regeneration temperature,the compositions of residual coke on the catalyst change from pyrene and phenanthrene to naphthalene,which are normally considered as active hydrocarbon pool species in MTO reaction.However,when the regeneration temperature is too high,nitrogen oxides can be found in the residual coke.Meanwhile,as the regeneration temperature increases,the quantity of residual coke reduces and the acidity,BET surface area and pore structure of the regenerated samples can be better recovered,resulting in prolonging catalyst lifetime.We have further derived the kinetics of steam regeneration,and obtained an activation energy of about 177.8 kJ·mol~(-1).Compared that with air regeneration,the activation energy of steam regeneration is higher,indicating that the steam regeneration process is more difficult to occur.     

水蒸气抑制2-甲基戊烷在USHY上催化裂解反应中焦炭生成

The effect of steam dilution on the formation of coke and minor products in 2-methylpenatne cracking on ultra stable HY at 673 K has been studied. The results show that steam dilution suppresses the formation of coke and minor aromatic products, but enhances the H/C atomic ratio of coke and the production of di-olefins. This and other evidences suggest that steam dilution enhances the desorption of coke precursors, diolefinic ions and cyclic ions, by inhibiting the further pathological reactions to produce aromatics and polyaromatics. These insights into the chemistry underlying coke formation in hydrocarbon cracking on solid acid catalysts can potentially be applied to the development of additives which inhibit coke formation and control catalyst deactivation.     

Weak base favoring the synthesis of highly ordered V-MCM-41 with well-dispersed vanadium and the catalytic performances on selective oxidation of benzyl alcohol

The key to improve the performance of heteroatom catalysts is to ensure the orderliness of catalysts and the good dispersion of heteroatoms. The alkalinity plays the indispensable role in synthetic process of V-MCM-41 catalyst.The excessive alkalinity of synthetic system will make the MCM-41 difficult to crystallize, even to dissolve. It is easy to accumulate for heteroatomic species in the system of low alkalinity. Herein, the highly ordered VMCM-41 with high vanadic content in framework is synthesized in the condition of excessive NH_3·H_2 O in this paper. A series of characterization results prove the good dispersion of vanadium species, and most of vanadium gets into the framework of MCM-41 with the states of tetravalence and pentavalence. Furthermore, the modified MCM-41 by other transition metals is successful synthesized by the method of V-MCM-41 in this paper. The VMCM-41 shows well catalytic activity for the selective oxidation of benzyl alcohol, which up to 74.83% for the conversion of benzyl alcohol and 96.20% for selectivity of benzaldehyde when initial V/Si = 0.10. The paper provides the possibility for industrial application of V-MCM-41 in the oxidation of benzyl alcohol for benzaldehyde.Besides, the work provides a significant idea for the synthesis of modified MCM-41 by well-dispersed transition metals.     

Effect of the Ni size on CH4/CO2 reforming over Ni/MgO catalyst: A DFT study

Carbon deposition is sensitive to the metal particle sizes of supported Ni catalysts in CH4/CO2 reforming.To explore the reason of this phenomenon,Ni4,Ni8,and Ni12 which reflect the different cluster thicknesses supported on the MgO(100) slabs,have been employed to simulate Ni/MgO catalysts,and the reaction pathways of CH4/CO2 reforming on Nix/MgO(100) models are investigated by density functional theory.The reforming mechanisms of CH4/CO2 on different Nix/MgO(100) indicate the energy barriers of CH4 dissociated adsorption,CH dissociation,and C oxidation three factors are all declining with the decrease of the Ni cluster sizes.The Hirshfeld charges analyses of three steps as described above show only Ni atoms in bottom two layers can obtain electrons from the MgO supporters,and the main electron transfer occurs between adsorbed species and their directly contacted Ni atoms.Due to more electron-rich Ni atoms in contact with the MgO supporters,the Ni/MgO catalysts with small Ni particles have a strong metal particle size effect and lead to its better catalytic activity.     

氮化合物对饱和烃类氧化的作用

A custom built dynamic oxygen uptake tester was used to study the influence of nitrogen compounds on the oxidation characteristics of the saturate fractions from mineral base oils. Expermental results indicate that nitrogen compounds,especially quinoline and indole,take part in the oxidation of saturates.It is also found that indole is more active than quinoline. The latter can be oxidized partly into ketoimine,and the former is more rapidly oxidized into acylamide.The oxidation products, ketoimine or acylamide, could inhibit the oxidation of the saturates by decomposing hydroperoxide.The influences of indole and quinoline on oxidation of saturates are more complex.For lower nitrogen content, the oxidation processes were accelerated.However, at high nitrogen content, the oxidation induction peroids were increased. The oxidation characteristics of saturates were also dependent on the type of catalysts presented.     

Silver modified Cu/SiO2 catalyst for the hydrogenation of methyl acetate to ethanol

A series of silver modified Cu/SiO_2 catalysts were synthesized with ammonia-evaporation method and applied in vapor-phase hydrogenation of methyl acetate to ethanol. The influence of additive ‘Ag' on the structural evolution of catalyst was systematically studied by several characterization techniques, such as N_2 adsorption–desorption, N_2O titration, PXRD, FTIR, in-situ FTIR, H_2-TPR, H_2-TPD, XPS and TEM. Results showed that incorporation of a small amount of Ag could enhance the structural stability, and the strong interaction between Cu and Ag species was conducive to increase the dispersion of copper species and create a suitable Cu~(+)/(Cu~0+ Cu~(+)) ratio, which was proposed to be responsible for the improved catalytic activity. The maximum conversion of MA(94.1%)and selectivity of ethanol(91.3%) over optimized Cu-0.5 Ag/SiO_2 and 120 h on stream without deactivation under optimal conditions demonstrates its excellent stability.     

邻氯苯酚废水的催化湿式氧化处理

Catalytic wet air oxidation (CWAO) was investigated in laboratory-scale experiments for the treatment of o-chlorophenol in wastewater. Experimental results showed that wet air oxidation (WAO) process in the absence of catalyst was also effective for o-chlorophenol in wastewater treatment. Up to 80% of the initial CODCr was removed by wet air oxidation at 270℃ with twice amount of the required stoichiometric oxygen supply. At temperature of 150℃, the removal rate of CODCr was only 30%. Fe2(SO4)3, CuSO4, Cu(NO3)2 and MnSO4 exhibited high catalytic activity. Higher removal rate of CODCr was obtained by CWAO. More than 96% of the initial CODCr was removed at 270℃ and 84.6%-93.6% of the initial CODCr was removed at 150℃. Mixed catalysts had better catalytic activity for the degradation of o-chlorophenol in wastewater.     

One Step Preparation of Sulfonated Solid Catalyst and Its Effect in Esterification Reaction

A carbon-based sulfonated catalyst was prepared by direct sulfonation and carbonization （in moderate conditions：200 ＆#176;C, 12 h） of red liquor solids, a by-product of paper-making process. The prepared sulfonated cata-lyst （SC） had aromatic structure, composed of carbon enriched inner core, and oxygen-containing （SO3H, COOH, OH） groups enriched surface. The SO3H, COOH, OH groups amounted to 0.74 mmol·g^-1, 0.78 mmol·g^-1, 2.18 mmol·g^-1, respectively. The fresh SC showed much higher catalytic activity than that of the traditional solid acid catalysts （strong^-acid 732 cation exchange resin, hydrogen type zeolite socony mobile-five （HZSM-5）, sulfated zir-conia） in esterification of oleic acid. SC was deactivated during the reactions, through the mechanisms of leaching of sulfonated species and formation of sulfonate esters. Two regeneration methods were developed, and the catalytic activity can be mostly regenerated by regeneration Method 1 and be fully regenerated by regeneration Method 2, respectively.     

Influence of extra-framework Al in Fe-MOR catalysts for the direct conversion of methane to oxygenates by nitrous oxide

Iron-containing zeolites play an important role in the selective oxidation of methane to oxygenates by nitrous oxide. A solid-state ion exchange method is adopted to prepare Fe-MOR zeolite catalysts with different amounts of extra-framework Al. EPR spectra and UV–vis spectra show that the percentage of iron ions in tetrahedral or octahedral coordination increases while those of clustered Fe species decrease by the addition of extra-framework Al species. Nitrous oxide titration reveals that more active Fe centers are formed, which promote the nitrous oxide consumption. The number of active centers in the catalyst with the introduction of extra-framework Al is about four times that of the catalyst without the addition of extra-framework Al. Due to this, there is an increase in the methane conversion, total selectivity and yield of oxygenates.     

Support Effects on Thiophene Hydrodesulfurization over Co-Mo-Ni/Al2O3 and Co-Mo-Ni/TiO2-Al2O3 Catalysts

A carbon-based sulfonated catalyst was prepared by direct sulfonation and carbonization （in moderate conditions：200 ＆#176;C, 12 h） of red liquor solids, a by-product of paper-making process. The prepared sulfonated cata-lyst （SC） had aromatic structure, composed of carbon enriched inner core, and oxygen-containing （SO3H, COOH, OH） groups enriched surface. The SO3H, COOH, OH groups amounted to 0.74 mmol·g^-1, 0.78 mmol·g^-1, 2.18 mmol·g^-1, respectively. The fresh SC showed much higher catalytic activity than that of the traditional solid acid catalysts （strong-acid 732 cation exchange resin, hydrogen type zeolite socony mobile-five （HZSM-5）, sulfated zir-conia） in esterification of oleic acid. SC was deactivated during the reactions, through the mechanisms of leaching of sulfonated species and formation of sulfonate esters. Two regeneration methods were developed, and the catalytic activity can be mostly regenerated by regeneration Method 1 and be fully regenerated by regeneration Method 2, respectively.     

Nature of nitrogen specie in coke and their role in NOx formation during FCC catalyst regeneration

NO_x emission during the regeneration of coked fluid catalytic cracking (FCC) catalysts is an environmental problem. In order to follow the route to NO_x formation and try to find ways to suppress it, a coked industrial FCC catalyst has been prepared using model N-containing compounds, e.g., pyridine, pyrrole, aniline and hexadecane–pyridine mixture. Nitrogen present in the FCC feed is incorporated as polyaromatic compounds in the coke deposited on the catalyst during cracking. Its functionality has been characterized using XPS. Nitrogen specie of different types, namely, pyridine, pyrrolic or quaternary-nitrogen (Q-N) have been discriminated. Decomposition of the coke during the catalyst regeneration (temperature programmed oxidation (TPO) and isothermal oxidation) has been monitored by GC and MS measurements of the gaseous products formed. The pyrrolic- and pyridinic-type N specie, present more in the outer coke layers, are oxidized under conditions when still large amount of C or CO is available from coke to reduced NO_x formed to N₂. “Q-N” type species are present in the inner layer, strongly adsorbed on the acid sites on the catalyst. They are combusted last during regeneration. As most of the coke is already combusted at this point, lack of reductants (C, CO, etc.) results in the presence of NO_x in the tail gas.     

Cu/ZrO2催化剂的研究进展及其应用

综述了催化剂Cu／ZrO2的制备方法及其在CO／H2、CO2／H2合成甲醇、NOx的分解、醇胺脱氢合成氨基酸、CO的氧化及CO＋NO反应等方面的应用。     

Inductive effect of basic nitrogen compounds on coke formation during the catalytic cracking process

This paper proposes a mechanism for the inductive effect of quinoline on coke formation during the catalytic cracking of o-xylene. Quinoline preferentially adsorbs on the acidic sites to induce coke formation and promote the conversion of o-xylene via electrophilic substitutions and hydrogen transfer reactions. The presence of naphthyl-quinolines and benzyl-quinolines in soluble coke identified by electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry and the characterization of two types of nitrogen species in coke by XPS both confirm that the mechanism is reasonable. Basic nitrogen compounds poison the acidic sites of catalysts and induce the coke formation from aromatics.     

生焦FCC催化剂反应性能研究

介绍了近年来国内外开发的几种与生焦催化剂反应性能有关的催化裂化新工艺及生焦催化剂在这些工艺过程中所发挥的主要作用。讨论了有关生焦FCC催化剂物化性能、反应性能以及焦炭沉积规律和焦炭结构组成等方面的研究进展,重点介绍了中国石化石油化工科学研究院在本领域的最新研究工作。     

Effect of bitumen-derived coke on deactivation of an HDM catalyst

A large-pore hydrodemetallation catalyst was treated with anthracene (AN) or a bitumen feed (BIT) in mineral oil solvent to obtain coke levels up to 12% carbon. In some runs, carbazole was added to the AN-coking run and in others, a nickel porphyrin compound was added to the BIT-coking run. Physical properties of the coked catalysts were determined, as well as catalyst activities for hydrogenation (HYD) and for hydrodenitrogenation (HDN) using a mixture of naphthalene and indole in n-heptane. It was found that the coke produced via BIT appeared to be porous, while that from AN was non-porous. A significant enhancement in nitrogen on the catalyst over that in the bitumen feed was observed. Catalytic activities of the coked catalysts decreased with increasing coke content, with HDN activity loss being greater than HYD activity. Neither the nature of the coke precursor, nor the presence of nitrogen or nickel on the catalyst, affected the extent of deactivation. Apparent activation energies decreased with increasing coke content. The role of coke on catalyst deactivation is discussed in terms of its effect on the distribution of different catalytically active sites for the reactions.     

Rh<Subscript>1−<Emphasis Type="Italic">x</Emphasis></Subscript>Pd<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript> Nanoparticle Composition Dependence in CO Oxidation by NO

Abstract  

Bimetallic 15 nm Pd-core Rh-shell Rh_1−x Pd _x nanoparticle catalysts have been synthesized and studied in CO oxidation by NO. The catalysts exhibited composition-dependent activity enhancement (synergy) in CO oxidation in high NO pressures. The observed synergetic effect is attributed to the favorable adsorption of CO on Pd in NO-rich conditions. The Pd-rich bimetallic catalysts deactivated after many hours of oxidation of CO by NO. After catalyst deactivation, product formation was proportional to the Rh molar fraction within the bimetallic nanoparticles. The deactivated catalysts were regenerated by heating the sample in UHV. This regeneration suggests that the deactivation was caused by the adsorption of nitrogen atoms on Pd sites.     

Synergetic effects of Y-zeolite and amorphous silica-alumina as main FCC catalyst components on triisopropylbenzene cracking and coke formation

The synergetic effects of HY-zeolite and silica-alumina (SA), as two major components of an FCC catalyst, on the cracking activity and coking tendency during catalytic cracking of 1,3,5-triisopropylbenzene (TiPB, as a resid representative) were studied. NaY-zeolite and SA were synthesized by hydrothermal and co-precipitation methods, respectively, and ammonium exchanged for three times at 80 °C. The catalysts were characterized by XRD, XRF, SEM, BET, AAS and ammonia TPD techniques. TiPB cracking was investigated on four different catalyst configurations including SA, Y-zeolite, SA.Y and SA-Y in a fixed bed reactor. SA.Y stands for physical mixture of equal amounts of Y-zeolite and SA. For SA-Y, a bed of SA was placed upstream of the same amount of Y-zeolite. The catalysts were in-situ activated at 475 °C and evaluated by TiPB cracking at 350 °C. The coke content of the catalyst beds, after 40 min cracking of TiPB, was estimated by TPO using an FT-IR gas cell. At 3 min time on stream, 5.2 times higher yield of benzene, as a deep cracking product, is observed on SA-Y as compared to SA.Y. The TiPB conversion decreases in the order of SA-Y > SA.Y > Y-zeolite ? SA. Furthermore, as compared to Y-zeolite, 24% lower coke is formed on SA-Y. Also CO evolution during TPO of coked SA-Y catalyst is about 24% lower than that of the coked zeolite. As a result, protecting of Y-zeolite by SA from direct exposure to resid feed enhances the cracking activity, decreases the tendency to coke formation and diminishes CO emission in the catalyst regeneration process.     

无烟煤与添加剂炼焦实验研究

采用马钢炼焦原料研究了无烟煤与添加剂配煤炼焦新工艺.用无烟煤取代部分焦煤的炼焦实验结果表明,在黏结剂PRT和CMC分别为0.5％条件下,无烟煤配入量为14％时所炼出的焦炭的粒焦反应性比9％无烟煤时所炼的焦更低,而反应后强度则高于加入9％无烟煤时所炼的焦,与不加无烟煤所炼的焦的差距很小;此外,在无烟煤配入量为14％时,改变添加剂配比的炼焦实验结果表明,对3-2,3-3及3-5号配方所炼的焦,具有比较好的落下强度与转鼓指数、较低的粒焦反应性和较高的反应后强度,比较接近不加无烟煤的基准焦配方3-1.     

Ir-based additives for NO reduction and CO oxidation in the FCC regenerator: Evaluation, characterization and mechanistic studies

Ir-based additives, developed to reduce NO and CO emitted during the regeneration of spent fluid catalytic cracking (FCC) catalysts were characterized to correlate physicochemical properties with catalytic performance. Support, metal loading and the state of the metal significantly affected the catalytic performance. Increasing the Ir loading or using a Ce-promoted γ-alumina (CPBase) support results in the formation of larger Ir particles. Local reduction of iridium oxide surface in such particles leads to coexisting Ir and Ir₂O phases being very beneficial for the catalytic activity.

NO reduction and CO oxidation take place thermally at 700 °C. Increasing the O₂ concentration in the feed favors CO oxidation at the expense of NO reduction. With 500ppmIr/CPBase and 1000ppmIr/CPBase additives, complete NO reduction and CO oxidation is achieved in the presence of 40% excess oxygen. Higher oxygen excess, however, reduces or eliminates the NOx reduction activity of these materials. IR studies suggest that NO reduction by CO proceeds on Ir/alumina additives via the dissociative adsorption of NO, the formation of NCO species on Ir and their migration to the alumina support, where N₂ and CO₂ are formed. IR spectroscopy indicates that Ce modifies the Ir surface enhancing the CO oxidation and enabling NO reduction via the NO₂ formation.     

Formation of coke from propene over 5A adsorbents – influence of the binder on the coke composition, location and removal

Coke formation from propene was investigated at 623 K and P_propene=100 kPa on a pure 5A zeolite and an industrial adsorbent (5A zeolite 80 wt.%–binder 20 wt.%). The composition and location of coke molecules were determined as a function of time on stream. Coking on the pure zeolite was faster than on the industrial adsorbent. This result is mainly due to the trapping of coke precursors by the binder, and consequently a significant decrease in the amount of coke on the zeolite present in the adsorbent. While the coke deposited on the binder is very polyaromatic, the carbonaceous compounds formed on the zeolite and on the adsorbent are constituted at low coke content by mono-, bi-, tri- and tetra-alkyl aromatic components, and these compounds are sterically blocked in the -cages of the 5A zeolite. At high coke content, very heavy polyaromatic compounds appear and are certainly located on the external surface of the zeolite crystallites. Adsorption measurements of both samples show that coke is heterogeneously distributed in the zeolite pores. Whatever be the adsorbent, the partial oxidation of coke on highly coked samples caused an increase in the adsorption capacity. The first few steps of regeneration of coked samples remove the heavy polyaromatic molecules responsible for the pore blockage and thus liberate the pores which are not occupied by coke molecules.