A high propylene productivity over B2O3/SiO2@honeycomb cordierite catalyst for oxidative dehydrogenation of propane

Boron-based metal-free catalysts for oxidative dehydrogenation of propane (ODHP) have drawn great attention in both academia and industry due to their impressive activity and olefin selectivity. Herein, the SiO₂ and B₂O₃ sequentially coated honeycomb cordierite catalyst is designed by a two-step wash-coat method with different B₂O₃ loadings (0.1%-10%) and calcination temperatures (600, 700, 800 ℃). SiO₂ obtained by TEOS hydrolysis acts as a media layer to bridge the cordierite substrate and boron oxide via abundant Si-OH groups. The welldeveloped straight channels of honeycomb cordierite make it possible to carry out the reactor under high gas hourly space velocity (GHSV) and the thin wash-coated B₂O₃ layer can effectively facilitate the pore diffusion on the catalyst. The prepared B₂O₃/SiO₂@HC monolithic catalyst exhibits good catalytic performance at low boron oxide loading and achieves excellent propylene selectivity (86.0%), olefin selectivity (97.6%, propylene and ethylene) and negligible CO₂ (0.1%) at 16.9% propane conversion under high GHSV of 345,600 ml·(g B₂O₃)^-1·h^-1, leading to a high propylene space time yield of 15.7 g C₃H₆·(g B₂O₃)^-1·h^-1 by suppressing the overoxidation. The obtained results strongly indicate that the boron-based monolithic catalyst can be properly fabricated to warrant the high activity and high throughput with its high gas/surface ratio and straight channels.     

纤维状BPO4/SiO2催化剂的制备及其丙烷氧化脱氢性能

通过静电纺丝法制备了一种高温焙烧后具有纤维状结构的磷酸硼/二氧化硅（BPO₄/SiO₂）催化剂,并考察了BPO₄负载量和焙烧温度对该催化剂的结构和催化丙烷氧化脱氢性能的影响。研究发现焙烧过程使纤维直径减小。随着BPO₄负载量的增加,丙烷氧化脱氢活性增高。当BPO₄负载量为7%（质量分数）,焙烧温度为600℃时,BPO₄/SiO₂催化剂具有最佳的催化性能;在反应温度为480℃下,丙烷转化率和丙烯产率分别达到17.0%和13.0%,且催化剂稳定性良好。当焙烧温度较低时（550℃）,催化剂中的有机物分子未被除尽,导致烯烃的选择性偏低;当焙烧温度较高时（700℃）,SiO₂结构收缩紧密,抑制了活性相的暴露。由于纤维结构可暴露更多活性位点,该催化剂较相同条件下粉末状BPO₄催化剂有着更高的催化活性。     

Selective oxidative dehydrogenation of propane over surface molybdenum-enriched MgMoO4 catalyst

Drastic activity increases were observed by the treatments of the magnesium-rich MgMo_0.99O_y catalysts, which are poorly active for the oxidative dehydrogenation of propane, with inorganic or organic acid to remove excess magnesium on the surface. MoO₃ loading on magnesium-rich MgMo_0.99O_y catalysts also resulted in drastic activity increases. The activity increases followed non-effective loadings of MoO₃ in the range 0–2 wt%, because it is necessary to neutralize the surface magnesium with MoO₃ before the formation of molybdenum-rich surface. The pH of the aqueous (NH₄)₆Mo₇O₂₄ solution for the MoO₃ loading apparently influenced the activity. Under the acidic conditions the MoO₃ loading resulted in the drastic activity increase but under the basic conditions the effect of the MoO₃ loading was poor, suggesting that a cluster-type MoO₃ on MgMoO₄ surface is responsible for the activity of propane oxidative dehydrogenation.     

SAPO-34 supported Pt–Sn-based novel catalyst for propane dehydrogenation to propylene

The Pt–Sn-based catalyst was intensified using SAPO-34 as support for direct propane dehydrogenation to propylene. The catalyst was prepared by sequential impregnation method and characterized by XRF, BET, XRD, NH₃-IR, NH₃-TPD, H₂-TPR, HR-TEM and O₂-pulse coke analysis. NH₃-TPD, IR spectra and XRD results suggested that the doping of metals on SAPO-34 did not affect its acidic strength and structural topology of support, respectively. Propylene selectivity of 94% and total olefins selectivity greater than 97% was achieved using Pt–Sn/SAPO-34. The results were compared with Pt–Sn/ZSM-5 under identical conditions. The possible reasons for improvement were the larger surface area, shape selectivity and particular by suitable acidity of SAPO-34.     

CeO2‐CrOy/γ‐Al2O3 redox catalyst for the oxidative dehydrogenation of propane to propylene

CeO₂‐CrO_y loaded on γ‐Al₂O₃ was investigated in this work for the oxidative dehydrogenation (ODH) of propane under oxygen‐free conditions. The ODH experiments of propane were conducted in a fluidized bed at 500°C‐600°C under 0.1 Mpa. The prepared catalyst was characterized by N₂ adsorption‐desorption measurements, H₂‐temperature‐programmed reduction, O₂‐temperature‐programmed desorption, NH₃‐temperature‐programmed desorption, x‐ray photoelectron spectroscopy, and x‐ray diffraction. The change in the selectivity of propylene resulted from the thermal cracking of the propane and the competition for lattice oxygen in the catalyst between propylene formation and propane and propylene combustion. Therefore, to achieve higher propylene yield in the industry, the reaction temperature should be 550°C‐575°C for the 17.5Cr‐2Ce/Al catalyst. The results of H₂‐TPR (from 0.2218 mmol/g‐0.3208 mmol/g) revealed that the addition of CeO₂ can enhance the oxygen capacity of CrO_y. Compared with that for 17.5Cr/Al, the conversion can be enhanced from 22.4% to 28.5% and the selectivity of propylene can be improved from 72.2% to 75.9% for the 17.5Cr‐2Ce/Al catalyst. In addition, CeO₂ can inhibit the evolution of lattice oxygen (O^2?) to electrophilic oxygen species (O₂^?), causing the average CO_x (CO and CO₂) selectivity to decrease from 9.64% to 6.31%.     

丙烷脱氢制丙烯催化剂中国专利技术进展

介绍了近几年丙烷脱氢制丙烯催化剂中国专利技术,分别论述了铂系催化剂、铬系催化剂和其它催化剂专利技术进展,对丙烷脱氢制丙烯催化剂的发展方向进行了推测。     

镧对PtSnNa/Al2O3催化剂丙烷脱氢反应性能的影响

制备了镧改性的PtSnNa/La/Al2O3催化剂,用于丙烷脱氢反应研究.结果表明镧的添加对PtSnNa//Al2O3催化剂的丙烷脱氢反应性能影响明显,当镧添加量(质量分数)为0.7%时,PtSnNa(0.3)/La/Al2O3催化剂的丙烯收率最大,而过量镧的加入不利于脱氢反应的进行.Na+和La+的协同调变作用可以明显抑制催化剂表面的积炭.     

BiOCl催化剂的丙烷氧化脱氢催化性能

以_L-赖氨酸为模板剂,采用沉淀法制备了BiOCl催化剂,对催化剂进行了X射线衍射、N₂吸附-脱附和H₂-TPR等表征,并测试了BiOCl催化剂对丙烷氧化脱氢制丙烯反应的催化性能。结果表明,制备的BiOCl催化剂为四面体结构,500 ℃焙烧3 h后,催化剂比表面积为11.2 m²·g^-1,未完全还原氧物种的含量较多。随着反应温度升高,丙烷转化率和丙烯选择性增加,丙烷转化率为20%时,丙烯选择性达64.5%。     

Modeling-based optimization of a fixed-bed industrial reactor for oxidative dehydrogenation of propane

An industrial scale propylene production via oxidative dehydrogenation of propane(ODHP)in multi-tubular reactors was modeled.Multi-tubular fixed-bed reactor used for ODHP process,employing 10000 of small diameter tubes immersed in a shell through a proper coolant flows.Herein,a theory-based pseudo-homogeneous model to describe the operation of a fixed bed reactor for the ODHP to correspondence ole fin over V_2O_5/γ-Al_2O_3catalyst was presented.Steady state one dimensional model has been developed to identify the operation parameters and to describe the propane and oxygen conversions,gas process and coolant temperatures,as well as other parameters affecting the reactor performance such as pressure.Furthermore,the applied model showed that a double-bed multitubular reactor with intermediate air injection scheme was superior to a single-bed design due to the increasing of propylene selectivity while operating under lower oxygen partial pressures resulting in propane conversion of about 37.3%.The optimized length of the reactor needed to reach 100%conversion of the oxygen was theoretically determined.For the single-bed reactor the optimized length of 11.96 m including 0.5m of inert section at the entrance region and for the double-bed reactor design the optimized lengths of 5.72m for the first and 7.32 m for the second reactor were calculated.Ultimately,the use of a distributed oxygen feed with limited number of injection points indicated a signi ficant improvement on the reactor performance in terms of propane conversion and propylene selectivity.Besides,this concept could overcome the reactor runaway temperature problem and enabled operations at the wider range of conditions to obtain enhanced propylene production in an industrial scale reactor.     

The oxidative dehydrogenation of ethane with CO2 over Mo2C/SiO2 catalyst

Mo₂C prepared on SiO₂ was found to be an effective catalyst for the dehydrogenation of ethane to produce ethylene in the presence of CO₂. The selectivity to ethylene at 850–923 K was 90–95% at an ethane conversion of 8–30%. With the increase of the temperature the dry reforming of ethane became also a significant process. It is assumed that the Mo oxycarbide formed in the reaction between CO₂ and Mo₂C plays an important role in the activation of ethane. This revised version was published online in July 2006 with corrections to the Cover Date.     

Effect of alkali metals additives to V2O5/TiO2 catalyst on physicochemical properties and catalytic performance in oxidative dehydrogenation of propane

The effect of alkali metal additives Li, K, and Rb to V₂O₅/TiO₂ catalyst on the rate of catalyst reduction with propane and reoxidation with oxygen, sorption of propene, and the electron work function has been examined. The results have been correlated with the catalytic performance in oxidative dehydrogenation, ODH, of propane. It has been found that the rates of reduction, reoxidation and the ODH of propane decrease in the order: VTi>LiVTi>KVTi>RbVTi. The activation energies of the reduction and reoxidation are not, however, affected by the presence of the alkali metals. The same sequence has been observed for the work function values of the catalysts. It is argued that alkali metal poisons the centres of the hydrocarbon activation. The yield and selectivity to propene in the ODH of propane increase, however, for the promoted catalysts, following the above sequence. This effect is ascribed to the decrease in the heat of the propene adsorption, which is due to the increase in the basicity and decrease in acidity on the promoted catalysts.     

Effect of vanadia loading in propane oxidative dehydrogenation on V2O5/SiO2 catalysts

The influence of V₂O₅ loading on the catalytic behaviour of V₂O₅/SiO2₂ catalysts in the oxidative dehydrogenation of propane to propylene (POD) has been investigated. The different activity-selectivity pattern of low (5 wt%) and highly (>10 wt%) loaded V₂O₅/SiO₂ catalysts is explained in terms of different surface vanadia species.     

Oxidative dehydrogenation of propane over V2O5-MgO/TiO2 catalyst: Effect of reactants contact mode

The performance of the active catalyst 5%V₂O₅-1.9%MgO/TiO₂ in propane oxidative dehydrogenation is investigated under various reactant contact modes: co-feed and redox decoupling using fixed bed and co-feed using fluid bed. Using fixed bed reactor under co-feed conditions, propane is activated easily on the catalyst surface with selectivities ranging from 30 to 75% depending on the degree of conversion. Under varying oxygen partial pressures, especially for higher than the stoichiometric ratio O₂/C₃H₈ = 1/2, nor the propane conversion or the selectivities to propene and COx are affected. The performance of the catalyst in the absence of gas phase oxygen was tested at 400 °C. It was confirmed that the catalyst surface oxygen participates to the activation of propane forming propene and oxidation products with similar selectivities as those obtained under co-feed conditions. The ability of the catalyst to fully restore its activity by oxygen treatment was checked in repetitive reduction–oxidation cycles. Fluid bed reactor using premixed propane–oxygen mixtures was also employed in the study. The catalyst was proved to be very active in the temperature range 300–450 °C attaining selectivities comparable to those of fixed bed.     

CrOx/Ti-Al2O3催化剂结构及其催化丙烷脱氢性能

以模板法制备的Ti改性Al₂O₃为载体制备了CrO _x /nTi-Al₂O₃催化剂,考察了Ti含量对催化剂的结构及其催化丙烷脱氢性能的影响。采用X射线衍射（XRD）、N₂吸附-脱附、透射电子显微镜（TEM）、傅里叶变换红外光谱（FTIR）、拉曼光谱、X射线光电子能谱（XPS）、氨气程序升温脱附（NH₃-TPD）、吡啶红外吸附（Py-IR）等方法对催化剂的结构进行了表征。结果表明,CrO _x /nTi-Al₂O₃催化剂具有均匀的泡沫状介孔结构并含有少量微孔,表面积在180~195m²/g;铬主要以Cr⁶⁺和Cr³⁺形式存在,其中Cr⁶⁺主要以单铬酸盐和双铬酸盐形式存在,Cr³⁺以α-Cr₂O₃晶体和高分散Cr₂O₃形式存在,Ti的加入降低了催化剂表面Cr⁶⁺含量,增加了孔道内高分散Cr³⁺含量;Ti的加入降低了弱酸的强度,生成了少量中强酸,并使催化剂中B酸和L酸中心数量明显减少。少量的Ti（0.5%~1.0%TiO₂,质量分数）可明显提高丙烷转化率和丙烯收率,但过多的Ti（>2%TiO₂）则明显降低丙烯选择性而使丙烯收率降低。CrO _x /nTi-Al₂O₃催化剂表面Cr⁶⁺物种可催化丙烷氧化脱氢,本身还原成Cr³⁺后继续催化丙烷直接脱氢,孔道内部的高分散Cr³⁺可催化丙烷直接脱氢反应,二者结合使催化剂保持了较高的催化活性和较好的稳定性。     

V–Al–O catalysts prepared by flame pyrolysis for the oxidative dehydrogenation of propane to propylene

A flame pyrolysis (FP) procedure has been set up for the preparation of V/Al/O catalysts to be employed for the oxidative dehydrogenation of propane to propylene. The samples have been characterised by means of various techniques (FT-IR, Raman, EPR, ICP-MS, TGA, XRD, SEM) and their catalytic activity has been evaluated in two different operating modes, i.e. under anaerobic conditions and by co-feeding oxygen. The particle size distribution became progressively more homogeneous with increasing V concentration, due to the catalytic effect of the V ions during the FP synthesis. Some V₂O₅ segregation was observed even at low V loading. However, higher V dispersion was attained with respect to a reference sample prepared by impregnation of the FP-prepared alumina support.The increase of V concentration always led to an improvement of propane conversion, though selectivity showed different trends depending on the operating conditions. The comparison with the sample prepared by impregnation showed similar catalytic activity, with a bit higher selectivity for the FP-prepared sample under anaerobic conditions.     

助催化剂Sn、Ga、In和K对丙烷脱氢催化剂Pt/Al2O3

用廉价的丙烷脱氢制丙烯是解决丙烯供应紧张问题的途径之一,研究优异性能的丙烷脱氢催化剂具有重要意义。采用分步浸渍法制备不同类型的丙烷脱氢催化剂Pt/Al₂O₃,在固定床反应器中考察助催化剂Sn、Ga、In和K对催化剂性能的影响。结果表明,Pt-Sn/Al₂O₃催化剂性能略优于Pt-Ga/Al₂O₃和Pt-In/Al₂O₃,并且比较稳定。在Pt-Sn/Al2O3催化剂中加入适量K,可有效改善催化剂性能,但高温条件下积炭严重,有待深入研究和改进。     

Optimization of V2O5–MgO/TiO2 catalyst for the oxidative dehydrogenation of propane effect of magnesia loading and preparation procedure

The effect of magnesia loading and preparation procedure of vanadia on titania catalysts on the physicochemical characteristics and the performance in propane oxidative dehydrogenation were investigated. A series of magnesia promoted vanadia catalyst (5 wt% V₂O₅) with varying amounts of MgO (1.9--10 wt%) were synthesized by synchronous and sequential deposition on titania support. The catalysts were characterized using several techniques (BET, XRD, H₂-TPR and NH₃)-TPD). Both MgO loading and preparation procedure affect the catalyst surface properties and the behavior in the oxidative dehydrogenation of propane. Magnesia addition results in drastic increase in propene selectivity, while the effect on activity is negative. The activity is inversely related with the magnesia loading. Deposition of V₂O₅ on previously prepared MgO/TiO₂ presents a beneficial effect in the activity of the sample. The role of acidity and reducibility is explored. There is no correlation between reducibility and activity of the catalysts, whereas the acidity seems to influence the catalytic performance. Catalyst containing 5 wt% V₂O₅ and 1.9 wt% MgO prepared by sequential deposition of V₂O₅ on already doped with MgO titania exhibits the most interesting results.     

V2O5/Al2O3上异丁烷脱氢反应研究

用浸渍法制备了质量分数为12%V₂O₅/Al₂O₃负载型催化剂，考察了催化剂的活化气氛，反应中异丁烷与氢气的比例和反应温度对异丁烷脱氢活性的影响。结果表明，用N2作活化气，反应中异丁烷与氢气的体积比为1∶1时，在质量分数为12%的V₂O₅/Al₂O₃催化剂上异丁烷脱氢转化率和选择性较好，在625 ℃时，转化率达到52%，选择性为80%。     

新型丙烷脱氢催化剂制备及其活性评价

以MIL-101(Cr)为载体,异丙醇铝为铝前驱体,通过添加助剂钾制备新型Cr_2O_3/Al_2O_3脱氢催化剂。考察反应温度、气时空速及钾含量等因素对脱氢过程的影响。结果表明,该催化剂对丙烷脱氢过程表现出较好的催化活性。在反应温度615℃、进料量60 mL·min~(-1)、钾质量分数3.2%的条件下,丙烷转化率39.6%,丙烯选择性90.0%。     

助剂Zn对PtSn/Al2O3催化剂丙烷脱氢性能的影响

以羰基铂锡化合物为前体,采用浸渍法将其负载于Zn改性Al₂O₃载体上制备了PtSn/xZn-Al₂O₃催化剂,考察了Zn的添加对催化剂丙烷脱氢性能的影响。采用N₂吸附-脱附、X射线衍射（XRD）、吡啶红外吸附（Py-IR）、氨气程序升温脱附（NH₃-TPD）、透射电子显微镜（TEM）等手段对催化剂的孔结构、表面酸性以及积炭行为进行了分析。结果表明,PtSn/xZn-Al₂O₃催化剂孔道以介孔为主,孔径集中分布于8～10nm;Zn助剂的添加,在催化剂表面会形成ZnO物种,可使PtSn/Al₂O₃催化剂上的金属颗粒粒径减小、分散更加均匀;Zn的加入能有效降低催化剂表面酸量,主要表现为L中强/强酸中心的降低,随着Zn含量的增加,催化剂表面酸量先减少后增加。少量Zn的存在可使PtSn/Al₂O₃丙烯选择性和稳定性显著提高,但过量Zn的加入会降低催化剂的脱氢活性,适宜Zn的质量分数为0.75%～1.0%。反应后催化剂表面积炭主要表现为烯烃性质和芳香烃性质,Zn的添加可有效抑制积炭的形成,提高催化剂稳定性。