Second row transition metal sulfides for the hydrotreatment of coal-derived naphtha II. Removal of individual sulfur compounds

The disappearance of individual sulfur compounds has been investigated during the hydrotreatment (simultaneous removal of sulfur, nitrogen and oxygen) of coal-derived naphtha over each of the bulk second row transition metal sulfides. The sulfur compounds in the naphtha mainly consist of thiols/sulfides, thiophene and substituted thiophenes. Thiols/sulfides are, in general, more easily converted than thiophenic compounds are. Lighter thiols/sulfides are intermediates in the conversion of higher boiling thiols/sulfides or thiophenes. Side chain alkyl C---C bond breaking is predominant during the disappearance of thiophenes over the Zr and Nb catalysts while C---S bond breaking is predominant over the other catalysts. Thiophenic compounds are hydrogenated prior to desulfurization over the Mo, Ru, Rh and Pd sulfides. Highly substituted thiophenes are the compounds most difficult to convert over the Mo, Ru, Rh and Pd sulfides. The substituted thiophenes exhibit different reactivity trends over molybdenum sulfide, on one hand, and the Group VIII sulfides, on the other, indicating different adsorption modes and surface mechanisms for their conversion over these catalysts. Individual sulfur compounds do not follow first order kinetics and the disappearance rate is limited by product inhibition. The overall removal of sulfur does not follow simple first or second order kinetics since the individual compounds do not react in parallel, independent or first order reactions.     

Second row transition metal sulfides for the hydrotreatment of coal-derived naphtha I. Catalyst preparation, characterization and comparison of rate of simultaneous removal of total sulfur, nitrogen and oxygen

Naphtha derived from an Illinois No. 6 coal contains appreciable quantities of sulfur-, nitrogen- and oxygen-containing compounds. The hydrotreatment of this naphtha has been evaluated over unsupported transition metal sulfide catalysts of the second row in the Periodic Table. The catalysts were prepared by a room temperature precipitation reaction. Surface areas, crystalline phase and particle size distributions were determined by Brunauer-Emmet-Teller (BET), X-ray diffraction (XRD) and transmission electron microscopy (TEM), respectively. A comparison of average particle sizes calculated from these three techniques has enabled the understanding of the morphology of the transition metal sulfides. The catalysts exhibit a so-called volcano plot for the HDS of dibenzothiophene. Similar so-called volcano plots are also exhibited for the simultaneous hydrodesulfurization (HDS), hydrodenitrogenation (HDN) and the hydrodeoxygenation (HDO) of the coal-derived naphtha containing a mixture of heteroatoms. The order of reactivity of the transition metal catalysts is the same for all three of the processes. Ruthenium sulfide (RuS₂) is the most active catalyst for HDS, HDN and HDO of the coal-derived naphtha.     

原料对石脑油加氢催化剂性能的影响

对石脑油加氢处理产品硫、氮含量严重超标现象进行了研究 ,重点探讨了原料性质对催化剂活性的影响。研究表明 :直馏石脑油中高硫、氮含量蜡质混合物组分会引起NHT催化剂中毒 ,造成催化剂失活 ,此时通过提高反应温度和压力及降低空速对硫、氮的脱除效果影响不大 ,只有限制这种高硫、氮含量蜡质混合物进入装置 ,才能保证装置产品质量合格     

金属氮化物/碳化物催化剂加氢性能研究进展

介绍了过渡金属氮化物/碳化物独特的晶体结构和电子性能及其与催化性能的内在联系。综述了过渡金属氮化物/碳化物在涉氢反应中催化加氢机理的研究进展,以及过渡金属氮化物/碳化物在加氢脱硫(HDS)、加氢脱氮(HDN)和其他涉氢反应中的应用。与传统的过渡金属硫化物催化剂相比,过渡金属氮化物/碳化物具有更加优异的氢吸附、活化和转移能力。     

煤基石脑油半再生催化重整制芳烃的工艺

采用工业铂铼双金属重整催化剂Pt-Re/γ-Al₂O₃开展了煤基石脑油半再生固定床催化重整单因素实验,并采用响应面法对工艺参数进行了优化与分析,最后对优化工艺条件下实验产物进行了分析。结果表明：加权平均入口温度（WAIT）、压力（P）、液时空速（LHSV）等操作条件对煤基石脑油芳烃型半再生重整产品质量、芳烃收率和C₅₊液体收率有很大的影响。煤基石脑油重整合适工艺参数区间：WAIT（500~520℃）、P（1.2~1.6MPa）和LHSV（2.0~3.0h^-1）;最佳工艺条件：WAIT为516℃,P为1.4MPa,LHSV为2.3h^-1。优化工艺条件下芳烃收率达到了79.81%,响应面实验操作条件区间内,WAIT、P和LHSV对芳烃收率影响大小顺序为：P > LHSV > WAIT。相比于石油基石脑油重整,煤基石脑油重整不仅纯氢产率和氢气纯度更高,还可获得更高的苯-甲苯-二甲苯（BTX）产率,其中苯收率：甲苯收率：二甲苯收率近似为1：3：2。     

Encapsulation of transition metal sulfides in faujasite zeolite for hydroprocessing applications

The dispersion of the sulfides of Co, Ni, Mo and W—and their combinations—in the micropores of acidic faujasite zeolite is a challenging task. While a close proximity of the hydrogenation function to the acidic cracking sites is thought to be beneficial for industrial hydrocracking applications, the genesis of well-defined metal sulfides in a tunable environment allows to address two important fundamental issues: (i) the possible existence of an optimum cluster size of metal sulfides with respect to hydrodesulfurization activity and (ii) an extension of the well-known support effect in hydrotreating catalysis. This review will concentrate on the various preparation methods—ranging from the brute-force chemistry involved in dispersing anion precursors to the occlusion of well-defined organometallic complexes in the zeolite micropore space, characterization to determine the successful genesis of suitable models and activity tests.

Successful dispersion of these sulfides in the micropores of faujasite is only possible by careful preparative methods, either using well-dried cation-exchanged precursors or organometallic complexes. A synergistic effect of acidic protons on the metal sulfides is noted. However, the relatively low activities of ultra-dispersed Mo- or Co-sulfide particles compared to those of particles on more traditional supports force us to conclude that there must be an optimal size for metal sulfide clusters larger than those stabilized in the micropores. Although there are some indications that a sulfided CoMo cluster can be formed in the micropores using organometallic precursors, the synergistic effect between the two metals is quite small. From an application point of view, the detrimental effect of bases such as water or nitrogen compounds to the final dispersion of the metal sulfides is problematic. Nevertheless, model studies indicate that a close proximity of acidic and hydrogenation components decreases coking deactivation.     

Study of cracking FCC naphtha in a secondary riser of the FCC unit for maximum propylene production

To satisfy the increasing propylene demand, reprocessing FCC naphtha in a secondary riser of the FCC unit was investigated. To this aim, a full range FCC naphtha was cracked over a mixture of two kinds of commercial equilibrium FCC catalysts, which contained 95 t.% Y zeolite-based catalyst and 5 wt.% ZSM-5 zeolite-based additive. The effects of operating parameters such as reaction temperature (temperature of the riser outlet), catalyst-to-oil ratio and residence time on FCC naphtha cracking were studied in a continuous pilot plant. This work demonstrates that FCC naphtha requires high operating severities to crack, and approximately 12–19 wt.% FCC naphtha can be transformed into propylene. The conversion and yield of propylene showed a rapid increase with increasing reaction temperature, and the increase of catalyst-to-oil ratio also enhanced FCC naphtha cracking, even at high reaction temperature. However, at high catalyst-to-oil reactions, hydrogen-transfer reactions constrain further increases in light olefin yields. At these high operating severities, shortening residence time is an appropriate way to obtain high yields of propylene combined with (i) lower yields of dry gas and (ii) a lower apparent hydrogen-transfer coefficient.     

Understanding the trends in the hydrodesulfurization activity of the transition metal sulfides

It is shown that the trends in the hydrodesulfurization activity of the transition metal sulfides can be understood from the variation in the binding energy of sulfur to the transition metals. A model based on the ab initio calculations of Gelatt, Moruzzi, and Williams is used to describe the binding energy trends and to single out the important parameters determining them. One important aspect of the model is, that it predicts that the trends in the catalytic activity are given to a large extend by the coupling between the sulfur chemisorption energy and the sulfur-induced distortions of the metal lattice. The simple model also appears to describe promotional effects.     

A series of NiMo/Al2O3 catalysts containing boron and phosphorus: Part II. Hydrodenitrogenation and hydrodesulfurization using heavy gas oil derived from Athabasca bitumen

The hydrodenitrogenation (HDN) and hydrodesulfurization (HDS) activity of a series of NiMo/Al₂O₃ catalyst containing boron (B) and phosphorus (P) were tested in a trickle bed reactor using heavy gas oil derived from Athabasca bitumen. Detailed characterization of these catalysts is given in Part I of this paper. Addition of B and P caused the formation of extremely strong acid sites on the catalyst and enhanced its HDN activity. The total (TN), basic (BN) and non-basic nitrogen (NBN) conversions increased from 61.9 to 78.0 wt.%, from 78.9 to 93.0 wt.% and from 52.8 to 70.0 wt.%, respectively, with the increase in B concentration from 0 to 1.7 wt.% to NiMo/Al₂O₃ catalyst. Similarly, TN, BN and NBN conversions increased from 61.9 to 78.4 wt.%, from 78.9 to 91.0 wt.%, and from 52.8 to 71.6 wt.% with the addition of 2.7 wt.% P. Though the addition of B and P to NiMo/Al₂O₃ catalyst did not show any significant effect on S conversion, the HDN and HDS activities of the catalyst containing 1.7 wt.% B and the one containing 2.7 wt.% P are comparable to those of a commercial catalyst. The activity over extended period indicated that catalysts L and K were more stable (lower deactivation rate) in terms of nitrogen removal activity than catalyst B (reference catalyst). On the other hand, the stability for sulfur removal was comparable with catalyst B. Selected catalysts after use were characterized using BET surface area, TPR, TPD and SEM techniques which were correlated further with their activities.     

Investigation of nitrogen compounds in coal tar products. 1. Unfractionated materials

The direct application of gas chromatography (g.c.) with a nitrogen-selective alkali-flame detector (AFD) and mass spectrometry to the identification of nitrogen compounds in coal tar products without the need for prior separation of nitrogen-rich fractions is described. Accurate mass measurement has allowed the assignment of atomic compositions to many nitrogen heterocycles despite their presence as minor components in complex aromatic mixtures, but some interference from hydrocarbons was encountered. Boiling point characteristics were used to assist in distinguishing between the various possible isomeric compound types. The AFD was used successfully for the quantitative g.c. determination of a range of nitrogen heterocycles in the unfractionated samples.     

Investigation of nitrogen compounds in coal tar products. 2. Basic fractions

Gas chromatography (g.c.), in conjunction with nitrogen-selective alkali flame detection (AFD) and mass spectrometry (m.s.), has been used for the detailed examination of nitrogen compounds in basic fractions from an anthracene oil and a low-temperature coal tar. The compounds identified were mainly aza species, but some di-nitrogen and mixed heteroatomic compounds were detected in the anthracene oil bases. Nitrogen-selective g.c.—AFD chromatograms of the extraction residues showed complex mixtures of non-basic nitrogen compounds; the major peaks were identified, but further g.c.-m.s. investigation of these compounds will require the preparation of hydrocarbon-free fractions.     

Second moment of n.m.r. line for the Wiser model of coal

The Wiser model of coal structure was tested using the Van Vleck moment of theory of n.m.r. lines the second moment of rigid and rotational structures being calculated. The results correspond to the second moment of the Gaussian component of free induction decay (FID) observed experimentally in some coals.     

Removal of several metal ions from aqueous solution using powdered stem of Arundo donax L. as a new biosorbent

Arundo donax L., a member of Poaceae, was washed, dried, selected, pulverized, and then used for removal of Cu(II), Cd(II), Ni(II), Pb(II) and Zn(II) from aqueous solution. Series batch experiments were conducted to investigate the effects of contact time, pretreatment, particle size of biomass and solution pH on the biosorption capability of A. donax L. powder. The desorption characteristics and renewability of the biomass were also studied. The applicability of Langmuir and Freundlich isotherms was examined for the experimental data, so did the pseudo-first-order, pseudo-second-order and Elovich kinetic models. Results showed that alkali-treated A. donax L. biomass was more appropriate to be the bio-material for biosorption when compared to acid-treated, washed and virgin A. donax L. Owing to its fast adsorption rate, high uptake capacity and the renewability of facility, stem of A. donax L. treated with NaOH seems to be a promising biosorbent for removal of heavy metals from wastewater.     

含氯废气催化燃烧过程中氯物种的迁移与转化

催化燃烧技术是处理含氯挥发性有机化合物（CVOCs）最有效的技术之一,其中过渡金属氧化物因其具有较好的热稳定性和较强的抗中毒性而得到了广泛的应用和关注,但对其抗氯中毒原理尚不明确。本文回顾和总结了近几年来不同过渡金属氧化物在CVOCs催化燃烧中的应用,对其氯中毒机理和抗氯中毒方式进行了综述。已有的研究证实,过渡金属氧化物催化氧化CVOCs的中毒方式包括氯吸附和形成金属氯氧化物两种,基于对氯中毒方式的认识,本文提出催化剂形貌和晶型调控、掺杂改性和酸改性等方式改变催化剂的物理化学性质,进而提高催化剂的催化活性和抗氯中毒能力,为CVOCs催化燃烧催化剂的设计提供了重要的参考。     

Effect of catalysts in the quality of syngas and by-products obtained by co-gasification of coal and wastes. 1. Tars and nitrogen compounds abatement

The aim of this work is to analyse the possibility of using co-gasification technology to process coal mixed with wastes to take profit of its energy content and at the same time to minimize the environmental impact associated with the use of wastes and to diminish the costs of flue gas treatment. The addition to coal of different types of materials, like: pine based waste, petcoke and polyethylene (PE), was not found to give rise to any operational problems, regarding both the feeding system and gasification process and led to higher energy conversions, however, the gas presented higher tars and hydrocarbons content. Several catalysts were tested, such as, dolomite, olivine, nickel and magnesium oxides, zinc oxides and cobalt and molybdenum oxides. Catalyst action was analysed in tars release and also in ammonia compounds reduction. The presence of catalysts allowed increasing hydrogen release, whilst there was a decrease in hydrocarbons and tars contents. A nickel-magnesium oxide was the catalyst that led to the highest reduction in hydrocarbons and tars. This catalyst also led to the lowest NH₃ content in the fuel gas produced, due to the catalyst efficiency in NH₃ destruction.     

Signal analysis of fiber-optic biosensor for the detection of organophosphorus compounds in the contaminated water

The fiber-optic biosensor consisted of tubular enzyme reactor and two sensing parts was developed for the detection of organophosphorus compounds in a contaminated water. The organophosphorus compounds was measured by acetylcholinesterase entrapped by Ca-alginate gel on a silicon tube. The litmus dye was used as the indicator of color change due to the inhibition of organophosphorus compounds on the acetylcholinesterase. Transmittance change of light at the input and output parts of tubular enzyme reactor was detected. The biosensor has the linear analytical range of 0–1.0 ppm with response time of 5 minutes. The proposed kinetics for irreversible inhibition of organophosphorus compounds on AChE agreed well with the experimental data. The theoretical model of diffusion and reaction in enzyme membrane was presented to analyze the response of sensor signal. Based on the simulation results using the model, the optimal amount of enzyme loaded and substrate was obtained as 80 μg and 6 mM, respectively.     

A study on the preparation of supported metal oxide catalysts using JRC-reference catalysts. I. Preparation of a molybdena–alumina catalyst. Part 1. Surface area of alumina

This is the first report of a group study on the preparation of a MoO₃/Al₂O₃ catalyst to find predominant preparation parameters for better and reproducible catalyst preparations. Variously prepared MoO₃/Al₂O₃ catalysts possessing 13 wt% MoO₃ were subjected to multiprong characterizations and catalytic tests. It was found that the surface area of the support was the most predominant preparation parameter for the dispersion of Mo oxide species; the dispersion increased as the surface area of the support increased. The formation of crystalline MoO₃ was observed at a surface Mo concentration higher than 3.2 Mo nm⁻². With sulfided MoO₃/Al₂O₃, it was established that the dispersion of Mo sulfide species increased with increasing surface area of the support and was in proportion to that of Mo oxide precursor species. The hydrodesulfurization activity of sulfided MoO₃/Al₂O₃ was proportional to the NO adsorption capacity. It is suggested that a homogeneous distribution of Mo oxide species is attained by an equilibrium adsorption technique. However, it was revealed that the surface area of the catalyst and Mo distribution were considerably modified by preparation parameters, such as drying processes, other than the surface area.     

A study on the preparation of supported metal oxide catalysts using JRC-reference catalysts. I. Preparation of a molybdena–alumina catalyst. Part 2. Volume of an impregnation solution

Ten types of 13 wt% MoO₃/Al₂O₃ catalysts were prepared by a conventional impregnation or equilibrium adsorption method using a common extrudate support. These catalysts were subjected to a comprehensive characterization and catalytic reactions to find important preparation parameters in practical preparations. It was demonstrated in the present group study that the formation of crystalline MoO₃ was strongly correlated with the Mo segregation on the outer surface of the extrudate. When the amount of the impregnation solution was large (ca. 10 cm³ g-Al₂O₃⁻¹), a considerably homogeneous distribution and high dispersion of Mo oxide species were attained irrespective of the other preparation parameters. It is suggested that when a pore volume impregnation or incipient wetness technique is employed, drying processes strongly affect the dispersion and distribution of Mo oxide species. Drying at a reduced pressure is suggested to result in a segregation of Mo oxides on the outer surface of the extrudate, and accordingly a formation of crystalline MoO₃.     

Characterization and catalytic activity of coal mineral matter: 1. Effect of hydrogen pretreatment and exposure to sulphur and nitrogen compounds

Low temperature ash (LTA) samples prepared from nine US coals were characterized by X-ray diffraction. X-ray fluorescence, and surface area analyses. The results showed that illite, kaolinite, quartz and pyrite are major components in LTAs and that $\text{S}\text{Fe}$ ratios of some LTAs decreased significantly after H₂ treatment implying the occurrence of a partial reduction of pyrite during this treatment. Surface areas of LTAs increased drastically on H₂ treatment but decreased after exposure to sulphur and nitrogen compounds in activity testing. Correlations for the surface areas of LTAs before and after H₂ treatment were found in terms of clay content and element concentrations.     

Tuning the electronic and thermal transport behaviors of metal-dispersed Ti2O3 composites derived by metal–insulator transition

Thermal management requires an understanding of the relations among the thermal energy transfer, electronic properties, and structures of thermoconductive materials. Here, we enhanced the metal–insulator transition (MIT)-induced effect on the thermal conductivities of microstructure-controlled Ti₂O₃ composites containing W as a thermal conductive filler at approximately 450 K. To change the electronic and thermal transport properties, we varied the particle radii of the conductive phases in the raw material. The change in the calculated electronic thermal conductivity relative to the electrical conductivity of the W_x(Ti₂O₃)_1?x composite was enhanced by compounding the material. When x was reduced from 50 vol% to 20 vol% and the W particle diameter was reduced from 150 μm to 5 μm, the variation in the estimated electronic thermal conductivity of the W_x(Ti₂O₃)_1?x composite was increased by a factor of 2.01. The total thermal conductivity was also changed by the MIT. At x = 50 vol% and a W particle diameter of 5 μm, the maximum thermal conductivity change was 6.34 times larger than that of pure Ti₂O₃. The detailed relation between the MIT-induced changes in thermal transport and the microstructure were elucidated in classical effective medium approximations.