Catalytic desulphurization of benzothiophene in an emulsion via in situ generated H2

Catalytic desulphurization of benzothiophene (BTH) in a water/toluene emulsion, a model system for heavy oil emulsions, was achieved at 340°C using a water-soluble phosphomolybdic acid (PMA), a precursor for dispersed Mo catalyst. This process is based on the activation of H₂O to generate H₂ in situ via the water gas shift reaction (WGSR) for hydrodesulphurization (HDS). At 340°C with an initial CO loading of 4.14 MPa, essentially complete sulphur removal was obtained. Kinetic expressions for the WGSR and HDS of BTH with in situ generated H₂ and externally supplied H₂ were developed and verified experimentally. The kinetic analysis indicates that WGSR is rate-determining and desulphurization with in situ generated H₂ is a relatively fast step. Apparently, in situ H₂ is about seven times more active than externally supplied H₂ for the hydrogenation of BTH. A mechanism for desulphurization involving initial hydrogenation of BTH to dihydrobenzothiophene (DHBTH) followed by hydrogenolysis to give ethylbenzene (EB) and H₂S is proposed.     

Kinetics of sulfur model molecules competing with H2S as a tool for evaluating the HDS activities of commercial CoMo/Al2O3 catalysts

The relative-volume activities (RVAs) for real feedstocks HDS of four commercial CoMo/Al₂O₃ catalysts have been compared to the rates for thiophene and dibenzothiophene conversion. The reaction of thiophene competing with H₂S was studied in flow microreactors under a wide range of conditions: 300–400°C, overall pressure 0.1 or 3 MPa, thiophene pressure 8–125 kPa, H₂S content 0–15 mol%. The reaction of dibenzothiophene (DBT, 2 wt% in decaline) was carried out in a batch reactor at 335°C and 4 MPa.

The conversion of the two model molecules proceeds through the same mechanism with a preliminary dearomatization step followed by parallel hydrogenolysis and hydrogenation. From kinetic modeling, the global rates and the contribution of the hydrogenation and hydrogenolysis routes to HDS were determined. Under pressure, hydrogenolysis was predominant. In that case, thiophene and DBT behaved similarly and their initial relative rates did not correlate the RVA. Industrial HDS is controlled by hydrogenation as evidenced by the good correlation between RVA and the rates of dearomatization of thiophene at atmospheric pressure and hydrogenation of the product biphenyl from DBT under pressure. It is concluded that the reaction of model molecules under selected conditions can appraise rapidly industrial HDS.     

Hydrotreating properties of mixed NbxMo1−xS2 alumina supported catalysts

Niobium-molybdenum disulfide solid solution (Nb_xMo_1−xS₂) has been prepared in a dispersed state on gamma alumina. The existence of this solid solution supported on alumina carrier has been proven with the help of EXAFS technique. The catalytic properties of these materials have been studied in hydrogenation and hydrodesulfurization reactions. Interestingly, as already observed for niobium sulfide, the activity of the Nb_xMo_1−xS₂ solid solution (HDS of DBT, P_tot=33 bar) is not decreased in the presence of H₂S up to p(H₂S)=200 Torr, at least up to x=0.4.     

Intensification of Deep Hydrodesulfurization Through a Two-stage Combination of Monolith and Trickle Bed Reactors

Deep hydrodesulfurization (HDS) is an important process to produce high quality liquid fuels with ultra-low sul-fur. Process intensification for deep HDS could be implemented by developing new active c...     

Preparation,Structure Characterization and Hydrodesulfurization Performance of B-Ni2P/SBA-15/Cordierite Monolithic Catalysts

A series of B-Ni2P/SBA-15/cord monolithic catalysts were prepared by coating the slurry of the B-Ni2P/SBA-15 precursors on a pretreated cordierite support, and followed by temperature-programmed reduct...     

HDS of dibenzothiophenes and hydrogenation of tetralin over a SiO2 supported Ni-Mo-S catalyst? ?

A one-step synthesized Ni-Mo-S catalyst supported on SiO₂ was prepared and used for hydrodesulphurization (HDS) of dibenzothiophene (DBT), and 4,6-dimethyl-dibenzothiophene (4,6-DMDBT), and for hydrogenation of tetralin. The catalyst showed relatively high HDS activity with complete conversion of DBT and 4,6-DMDBT at temperature of 280 °C and a constant pressure of 435 psi. The HDS conversions of DBT and 4,6-DMDBT increased with increasing temperature and pressure, and decreasing liquid hourly space velocity (LHSV). The HDS of DBT proceeded mostly through the direct desulphurization (DDS) pathway whereas that of 4,6-DMDBT occurred mainly through the hydrogenation-desulphurization (HYD) pathway. Although the catalyst showed up to 24% hydrogenation/dehydrogenation conversion of tetralin, it had low conversion and selectivity for ring opening and contraction due to the competitive adsorption of DBT and 4,6-DMDBT and insufficient acidic sites on the catalyst surface.     

钼酸铵与LaHY固相反应机理

采用TG-DSC技术研究了钼酸铵和LaHY在空气气氛中的失重行为,考察了钼酸铵与LaHY的固相反应机理,用XRD、BET和NH₃-TPD对其物相结构、比表面积和表面酸性进行了表征。结果表明,（NH₄）₆Mo₇O₂₄·4H₂O分解产生的表相Mo物种借助固相反应以金属-氧簇定位在LaHY分子筛体相笼中形成nMoO_x·LaHY单相复合体,引起分子筛的晶胞收缩,晶胞参数a₀减小,比表面积下降。制备的nMoO_x·LaHY较相应LaHY分子筛的弱酸中心变化较小,中强酸中心增加,强酸中心略有减少,总酸量增加。以质量分数为0.6%的二苯并噻吩/正癸烷溶液为模型反应物,评价了制备的nMoO_x·LaHY催化剂的加氢脱硫性能。负载Mo质量分数为5.0%制得的nMoO_x·LaHY催化剂在反应压力4.0 MPa,反应液时空速20 h^-1,H₂/原料液体积比500:1的实验条件下,290℃和310℃的二苯并噻吩加氢脱硫转化率达到了56.38%和88.79%,较相应负载Mo质量分数为20.0%制备的MoO₃/Al₂O₃催化剂分别提高了约12个百分点和28个百分点,表现出了较高的二苯并噻吩加氢脱硫反应活性。     

Hydrodesulfurization of model diesel using Pt/Al2O3 catalysts prepared by supercritical deposition

Pt/Al₂O₃ catalysts with Pt loadings ranging from 0.5 to 11 wt.% were synthesized by supercritical carbon dioxide (scCO₂) deposition method. Transmission electron microscopy (TEM) images showed that the synthesized catalysts contained small Pt nanoparticles (1–4 nm in diameter) with a narrow size distribution, no observable agglomeration, and uniformly dispersed on the alumina support. The catalysts were found to be active for hydrodesulfurization of dibenzothiophene (DBT) dissolved in n-hexadecane (n-HD) without sulfiding the metal phase. The reaction proceeded only via the direct hydrogenolysis route in the temperature range 310–400 °C and at atmospheric pressure. The activity increased with increasing the metal loading. Increasing [H₂]₀/[DBT]₀ by either increasing [H₂]₀ or decreasing [DBT]₀, increased the DBT conversion. At a fixed weight hourly space velocity and feed concentration, conversion did not increase with increasing temperature beyond 330 °C. The presence of toluene inhibited the catalyst activity presumably due to competitive adsorption between DBT and toluene. Under the operating conditions, the reaction was far from equilibrium.     

Si改性对NiMo/Al2O3催化剂加氢脱硫性能的影响

以中和法合成的不同SiO₂含量的改性氧化铝为载体,本文制备系列Si改性的NiMo/Al₂O₃催化剂,采用X射线衍射（XRD）、N₂物理吸附（BET）、程序升温脱附（NH₃-TPD）、吡啶吸附红外光谱（Py-IR）、程序升温还原（H₂-TPR）、高分辨透射电镜（HRTEM）和X射线光电子能谱（XPS）等分析手段进行详细表征。表征结果显示,引入Si减弱了活性金属与载体之间的相互作用,改善了催化剂的孔结构与表面酸性分布,提高了活性相分散度和金属硫化度,促使形成更多的II类NiMoS活性相。以二苯并噻吩（DBT）为模型化合物,在固定床加氢装置上考察了系列催化剂的加氢脱硫（HDS）性能,结果表明,引入Si可降低DBT的加氢反应活化能,提高反应速率常数,进而提高催化剂的加氢脱硫活性。对比DBT转化率在50%时的脱硫产物分布表明引入Si可影响催化剂的反应路径选择性,直接脱硫路径（DDS）选择性从83.69%增加至92.89%,证实了催化剂的表征规律。     

Hydrodenitrogenation of pyridine over alumina-supported iridium catalysts

The catalytic properties of alumina-supported Ir catalysts (≈1 wt% Ir) were studied in the hydrodenitrogenation (HDN) of pyridine at 320°C and 20 bar of pressure in the absence as well as presence of parallel hydrodesulfurization (HDS) of thiophene. The effects of Ir precursor (Ir(AcAc)₃, Ir₄(CO)₁₂, H₂IrCl₆, (NH₄)₂IrCl₆), metal dispersion and sulfur addition were investigated. Ir₄(CO)₁₂ gave the most active catalyst which was ascribed to a lower amount of contaminants originated from the starting Ir compounds rather than to a better Ir dispersion. The decrease of Ir dispersion by sintering in air led to much higher decrease of the rate of C–N bond hydrogenolysis than that of pyridine hydrogenation. The Ir dispersion determined partly the HDN selectivity; a better dispersed Ir phase gave a lower amount of intermediate piperidine. Presulfidation of the reduced catalyst led to 20% decline of the rates of both consecutive HDN steps. An additional and much larger activity decline was caused by the simultaneous execution of HDS. The competitive adsorption of thiophene (or H₂S) was selectively affecting C–N bond hydrogenolysis more than pyridine hydrogenation. The alumina-supported Ir catalysts possessed much higher HDN activity and HDN/HDS selectivity than a conventional NiMo system.     

Effect of the nitrogen heterocyclic compounds on hydrodesulfurization using in situ hydrogen and a dispersed Mo catalyst

The hydrodesulfurization (HDS) of the highly refractory sulfur-containing compounds, dibenzothiophene (DBT) and 4,6-dimethyldibenzothiophene (4,6-DMDBT), and the effect of the basic and non-basic nitrogen heterocyclic compounds, such as quinoline and carbazole, on HDS using a dispersed unsupported Mo catalyst and in situ generated hydrogen were studied. Experimental results indicated that the dispersed unsupported Mo catalyst was effective for the HDS of 4,6-DMDBT in a mixture containing DBT. The direct desulfurization pathway (DDS) was the preferred pathway for the HDS of DBT while the hydrogenation pathway (HYD) was the preferred pathway for the HDS of 4,6-DMDBT under our experimental conditions. A strong inhibitive effect of the basic quinoline or the non-basic carbazole on the HDS of each of the sulfur-containing compounds was observed. The DDS and HYD pathways in the HDS of the refractory sulfur-containing compounds were affected to a different extent by the nitrogen-containing compounds, suggesting that different active sites were involved in these two reaction pathways.     

Assessment of limitations and potentials for improvement in deep desulfurization through detailed kinetic analysis of mechanistic pathways

Utilizing an improved method for the assignment of the rate constants to the complicated network of reaction pathways in the hydrodesulfurization (HDS) of polyaromatic sulfur compounds (PASCs), new understanding has been obtained concerning the intrinsic limitations to achieving the new distillate fuels standards. Establishing the relative rates for hydrogenation of the parent sulfur compound and its desulfurized products, and considering thermodynamic limitations on hydrogenated intermediates are critical to these improved kinetics. With this new approach, it has been possible to more accurately assess the differences in performance of different catalysts such as Co–MoS_x/Al₂O₃, Ni–MoS_x/Al₂O₃ and analogous catalysts supported on carbons, the basic causes of selectivity change with temperature, and the mechanistic consequences of inhibitors on the HDS product distributions. Ni promoted catalysts were found to possess much higher hydrogenation activities than comparable Co promoted catalysts. Carbon supported catalysts appear to have potential for HDS at high temperatures. Inhibition by H₂S affects both hydrogenation and direct sulfur extraction HDS routes, but, secondary hydrogenation of desulfurized aromatic products was found to be the most sensitive to inhibition. Naphthalene inhibits all hydrogenation reactions but has little effect on direct HDS.     

Sulfur exchange on Co---Mo/Al2O3 hydrodesulfurization catalyst using S radioisotope tracer

A commercial Co---Mo/Al₂O₃ catalyst was labeled with the radioisotope ³⁵S in hydrodesulfurization (HDS) of ³⁵S-labeled dibenzothiophene (³⁵S-DBT) in a high-pressure flow reactor at 50 kg/cm². Then, HDS of 4-methyldibenzothiophene (4-MDBT) and 4,6-dimethyldibenzothiophene (4,6-DMDBT) or sulfur exchange of H₂S were carried out on the labeled catalyst at 50 kg/cm² and 260–360°C. The amounts of labile sulfur participating in the reaction were determined from the radioactivity of ³⁵S---H₂S released from the ³⁵S-labeled catalyst. In the HDS reactions, the amount of labile sulfur participating in the reaction decreased in the order: DBT> 4-MDBT> 4,6-DMDBT. In the sulfur exchange reaction with H₂S, the adsorption of H₂S on the catalyst reached saturation above a H₂S partial pressure of 0.36 kg/cm². It was suggested that the release of H₂S from the labile sulfur may be the rate determining step of the HDS reaction.     

CO and CO2 hydrogenation study on supported cobalt Fischer–Tropsch synthesis catalysts

The conversion of CO/H₂, CO₂/H₂ and (CO+CO₂)/H₂ mixtures using cobalt catalysts under typical Fischer–Tropsch synthesis conditions has been carried out. The results show that in the presence of CO, CO₂ hydrogenation is slow. For the cases of only CO or only CO₂ hydrogenation, similar catalytic activities were obtained but the selectivities were very different. For CO hydrogenation, normal Fischer–Tropsch synthesis product distributions were observed with an of about 0.80; in contrast, the CO₂ hydrogenation products contained about 70% or more of methane. Thus, CO₂ and CO hydrogenation appears to follow different reaction pathways. The catalyst deactivates more rapidly for the conversion of CO than for CO₂ even though the H₂O/H₂ ratio is at least two times larger for the conversion of CO₂. Since the catalyst ages more slowly in the presence of the higher H₂O/H₂ conditions, it is concluded that water alone does not account for the deactivation and that there is a deactivation pathway that involves the assistance of CO.     

Upgrading Siberian (Russia) crude oil by hydrodesulfurization in a slurry reactor: A kinetic study

Hydrodesulfurization (HDS) of sour crude oil is an effective way to address the corrosion problems in refineries, and is an economic way to process sour crude oil in an existing refinery built for sweet oil. In the current study, the HDS of Siberian crude oil was carried out in a slurry reactor. The Co-Mo, Ni-Mo, and Ni-W catalysts supported on γ-Al₂O₃ were compared at the temperature of 340℃ and the pressure of 4.5 MPa. The HDS activity follows the order of Co-Mo > Ni-Mo > Ni-W at a high concentration of H₂S, and the difference between Co-Mo and Ni-Mo becomes insignificant at a low concentration of H₂S. The influence of reaction temperature 320-360℃ and reaction pressure 3-5.5 MPa was investigated, and both play a positive role in the HDS reaction. A kinetic model over Ni-Mo/Al₂O₃ in the slurry reactor was established. The activation energy is estimated as 60.34 kJ·mol^-1; the orders of sulfur components and hydrogen partial pressure are 1.43 and 1.30, respectively. The kinetic parameters are compared with those in a trickle-bed reactor, implying that the mass transfer is greatly enhanced in the slurry reactor. The back mixing effect is present in the slurry reactor and can be reduced by a multi-stage design, which would lead to higher reactor efficiency in industrial application.     

Deep desulfurization of diesel fuels: kinetic modeling of model compounds in trickle-bed

Five catalysts with different hydrodesulfurization (HDS) and hydrogenation activity were tested in HDS of fresh crude heavy atmospheric gas oil (HAGO) (1.33 wt% S), two partially hydrotreated HAGO (1100 and 115 ppm S) and two model compounds, dibenzothiophene (DBT) and 4,6-dimethyldibenzothiophene (DMDBT), dissolved in model solvents and HAGO. Aromatic compounds in the liquid decreased significantly the HDS rate of 4,6-DMDBT, especially for catalysts with high hydrogenation activity. H₂S displayed a similar inhibition effect with all catalysts. These effects were extremely pronounced in HAGO where the DBT HDS rate decreased by a factor of 10 while 4,6-DMDBT – of 20 relative to paraffinic solvent. The feasibility of using a highly active hydrogenation catalyst for deep HDS of HAGO is diminished by the strong impact of aromatics.     

Removal of refractory S-containing compounds from liquid fuels on novel bifunctional CoMo/HMS catalysts modified with Ti

This study shows that titanium incorporation into hexagonal mesoporous silica (HMS) material has a positive effect on the activity of supported CoMo catalysts in the hydrodesulfurization (HDS) of dibenzothiophene (DBT) and 4-ethyl,6-methyl-dibenzothiophene (4E6MDBT). All catalysts showed the highest activity in the HDS of DBT than in the HDS of 4E6MDBT. The low reactivity observed in the HDS of 4E6MDBT is caused by the steric hindrance of the two alkyl groups at positions 4 and 6. The HDS of DBT over Ti-free catalyst proceeds exclusively via the direct desulfurization (DDS) route whereas over Ti-containing catalysts proceed via DDS (main route) and hydrogenation (HYD) pathway. The catalyst with a Si/Ti = 40 (molar ratio) was the most active in the HDS of DBT. A further increase in the Ti-content led to a decrease in Brønsted acidity and the S_BET specific area of the catalysts, which implies a decrease in the bifunctional character of the catalysts. Raman spectroscopy demonstrated that Ti-incorporation into HMS material leads to a decrease in the degree of polymerization of Mo species, and this implies a better dispersion of MoS₂, in good agreement with the XPS measurements. Regarding the HDS-resistant 4E6MDBT, the HDS reaction over the Ti-free catalyst was found to proceed exclusively via the dealkylation (DA) route. After Ti-incorporation into HMS material, additional acid-catalyzed isomerization occurs. With respect to industrial sample, the catalyst with Si/Ti = 40 showed lower intrinsic activity as well as greater selectivity toward isomerization route products.     

乙炔加氢反应系统操作优化策略

乙炔加氢反应系统是乙烯生产流程中的重要装置, 在催化剂反应动力学模型和失活模型已知的情况下, 研究两组串联反应器中除炔负荷的最佳分配。通过优化计算结果显示, 一段反应器入口氢炔比尽量控制在1.0以下, 二段反应器的氢炔比根据实际需要可以从1.9逐渐提高到3.5。考虑实际的操作费用和产品价格因素, 在负荷分配优化操作的前提下, 进一步研究了反应器切换再生对整体经济效益的影响。为使其整体效益最大, 一段反应器应该使用14个月后切换再生, 而二段反应器使用4个月后就需要切换再生。     

Si含量对CO_2加氢制烃铁基催化剂的影响

以湿固相研磨法制备不同硅含量的铁基催化剂,采用X射线衍射、H2程序升温还原和傅里叶红外光谱对催化剂进行表征,在V(H_2)∶V(CO_2)∶V(N_2)=16∶8∶1、反应压力1.6 MPa、反应温度230℃、反应时间48 h和空速6 000 m L·(h·g-cat)-1条件下,在固定床反应器中考察催化剂的CO_2加氢制烃反应活性和烃类选择性。结果表明,随着Si O_2掺入量增加,催化剂的还原性能降低,结晶度呈下降趋势,CO_2转化率下降,但C5+烃类产物选择性在硅含量为10%时达到最大,为38.6%。