生物质气化焦油裂解用颗粒催化剂的再生性能

为开发适用于生物质气化焦油裂解的多孔白云石颗粒催化剂,以乙酸为生物质气化焦油的模型化合物,讨论了积炭对多孔白云石颗粒催化能力以及再生性能的影响。结果表明,在积炭率0～4.4%时,多孔白云石颗粒的催化能力随积炭率呈线性下降。当积炭率从0增加到4.4%时,颗粒的孔隙率从0.74 cm³·g^-1减小到0.48 cm³·g^-1,乙酸裂解率从99.3%降至32.3%。采用900 ℃和2 h焙烧法对积炭多孔白云石颗粒进行再生处理后,多孔白云石颗粒的强度基本不变,孔隙率增至0.55 cm³·g^-1。在再生多孔白云石颗粒上,乙酸裂解率达到99.5%。多孔白云石颗粒催化剂具有良好的再生性。     

生物质气化焦油裂解催化剂研究进展

将生物质气化转化为气体燃料或化工合成气原料,是生物质清洁高效利用的有效途径之一,焦油是气化的副产物,影响产气品质和气化效率,催化剂对生物质催化气化及焦油裂解效果明显,得到广泛应用。综述了天然催化剂、无机盐催化剂及合成催化剂对生物质气化过程焦油催化裂解效果、反应条件、催化机理。进一步分析了不同催化剂的生物质催化气化性能及研究进展。同时指出对天然矿石催化剂进行改性或大力发展合成类催化剂对生物质气化焦油降解有着良好的前景。     

多孔镍/白云石颗粒对生物质气化焦油裂解的催化性能

通过添加镍的方法,改善多孔白云石颗粒对生物质气化焦油裂解的催化能力。采用配位沉淀法制备Ni/白云石粉末,再以Ni/白云石粉末为原料,制备多孔Ni/白云石颗粒。以苯为生物质气化焦油的模型成分,在Ni/白云石颗粒固定床对苯进行蒸汽重整,考察了多孔Ni/白云石颗粒制备过程中,焙烧温度和氧化镍含量等条件对其催化能力的影响。结果表明,多孔Ni/白云石颗粒的催化能力随焙烧温度和氧化镍含量而变化,在焙烧温度750 ℃和氧化镍质量分数13.5%的条件下,Ni/白云石颗粒上苯蒸汽重整的气体收率达到最大值83.0%。在焙烧温度（450～900） ℃和氧化镍质量分数0～22.5%时,积炭率基本保持在4.5%。900 ℃焙烧2 h,对积炭失活的多孔Ni/白云石颗粒进行再生,再生的多孔Ni/白云石颗粒对苯蒸汽重整的催化能力与新鲜多孔Ni/白云石颗粒相同。     

Ni基生物质焦油重整催化剂的研究进展

Ni基催化剂对生物质气化过程中生成焦油的催化裂解重整具有较好的催化活性,但在催化反应中存在容易积炭进而失活的现象。如何提高Ni基催化剂的催化活性和抗积炭能力是Ni基催化剂研究中的难点。本文从催化剂的活性组分、载体和助催化剂3个方面入手,详细综述了近几年关于提高Ni基生物质焦油重整催化剂催化活性和抗积炭能力的研究进展,讨论了催化剂的活性组分、载体和助催化剂对催化剂催化活性的影响。指出Ni-Fe、Ni-Co、Ni-Cu催化剂均表现出比Ni基催化剂更好的催化活性,助剂的加入有利于提高吸附剂的抗积炭能力和抗烧结能力;催化剂载体方面,钙钛矿型混合金属氧化物载体、煤焦和生物质焦载体具有较好的研究前景。     

Thermal plasma-sprayed nickel catalysts in the clean-up of biomass gasification gas

Plasma spraying is a potential catalyst preparation method for hot gas clean-up which requires very durable catalytic coatings. In this work, the multi-layer composite coating powders consisted of a gibbsite or boehmite core together with a hydrotalcite coating. We used the coating powders in the preparation of the powder form Ni catalysts, which were characterized by XRD, BET, XPS, and XRF. The coating powders were also used in the preparation of plasma sprayed metal substrate supported Ni catalysts. Selected plasma-sprayed nickel containing catalysts were characterized by XRD and SEM. In addition, for comparative purposes we prepared and used a ceramic monolithic Ni catalyst on modified ZrO₂. The performance of all catalysts were studied in the clean-up of synthetic gasification gas, i.e. the decomposition of tar, ammonia, and methane, at 700 and 900 °C, without and with the addition of H₂S. Catalysts with a gibbsite-core showed higher activity and better sulfur resistance than those with a boehmite-core. The high activity of the gibbsite-core Ni catalyst with a sulfur-containing gas together with the promising mechanical and thermal strength makes the plasma spraying method an interesting alternative for gas clean-up catalysts in biomass gasification processes.     

高温水蒸气生物质催化气化研究进展

综述了近些年提出的高温水蒸气气化技术(HTSG),该技术不仅有利于抑制焦油生成,提高气化效率和碳的转化率,而且能够有效提高气化气中氢气含量(40%~60%),具有很好的研究意义和技术应用前景。此外,催化剂作为该技术的重要组成部分,通过介绍催化剂对生物质气化在产气量、气化效率、催化机理等方面的影响,重点综述其作用原理、实用性、优缺点及催化气化亟待解决的关键问题,最后给出高温水蒸气气化技术和合成类催化剂建议及其应用展望。     

高温水蒸气生物质催化气化研究进展

综述了近些年提出的高温水蒸气气化技术(HTSG),该技术不仅有利于抑制焦油生成,提高气化效率和碳的转化率,而且能够有效提高气化气中氢气含量(40%⁶0%),具有很好的研究意义和技术应用前景。此外,催化剂作为该技术的重要组成部分,通过介绍催化剂对生物质气化在产气量、气化效率、催化机理等方面的影响,重点综述其作用原理、实用性、优缺点及催化气化亟待解决的关键问题,最后给出高温水蒸气气化技术和合成类催化剂建议及其应用展望。     

Steam reforming of tar from a biomass gasification process over Ni/olivine catalyst using toluene as a model compound

A Ni/olivine catalyst, previously developed for biomass gasification and tar removal during fluidized bed steam gasification of biomass, was tested in a fixed bed reactor in toluene steam reforming as a tar destruction model reaction. The influence of the catalyst preparation parameters (nickel precursor, calcination temperature and nickel content) and operating parameters (reaction temperature, steam to carbon S/C ratio and space-time) on activity and selectivity was examined showing a high toluene conversion and a low carbon formation compared to olivine alone. The steam reforming of toluene was found to be of zero order for water and first order for toluene. Activation energy required for Ni/olivine was determined to be about 196 kJ mol⁻¹ in accordance with literature. Catalyst activity and stability and its resistance against carbon formation were discussed on the basis of X-ray diffraction (XRD), transmission electron microscopy (TEM) and temperature programmed oxidation (TPO) results. Characterization before test (XRD, temperature programmed reduction (TPR), Mössbauer spectroscopy) have shown the presence of NiO–MgO solid solution, formed on the surface of olivine support, which explains the efficiency of the catalyst calcined at 1100 °C. After test, Ni–Fe alloys were observed (TEM, Mössbauer spectroscopy). It was suggested that magnesium oxide enhanced steam adsorption, facilitating the gasification of surface carbon and that Ni–Fe alloys prevented carbon deposition by dilution effect.     

Development of new nickel based catalyst for tar reforming with superior resistance to sulfur poisoning and coking in biomass gasification

Gasification of tar by catalytic steam reforming was examined in the gasification process of biomass, such as dried sewage sludge and wood chips. The tar reforming characteristics of the newly-developed Ni/MgO–CaO (based on dolomite) catalyst which was doped with WO₃ as a sulfur-resistant promoter, was investigated using a simulated gas containing naphthalene as tar. The result has confirmed that the developed catalyst shows a high naphthalene reforming activity and is stable even in gas containing hydrogen sulfide. The catalyst also exhibited superior resistance to coking as well as sulfur poisoning compared to several commercial steam-reforming catalysts.     

Action of nickel catalyst during steam gasification of bituminous and brown coals

Steam gasification of a bituminous coal and a brown coal has been carried out in the presence of a nickel catalyst. The action of catalyst particles during gasification was investigated by comparing a series of scanning electron microscope (SEM) photographs taken at stages throughout the experiment. Finely dispersed catalysts with an average diameter of <10 nm were observed upon devolatilization. During the steam gasification of bituminous coal, the carbon substrate around the catalyst was gasified. At higher catalyst loadings considerable catalyst agglomeration occurred and was associated with a decrease in effectiveness of the catalyst. On the other hand, catalyst particles remaining well-dispersed in brown coal after 80 wt% char conversion maintained an extraordinarily high activity.     

应用镍/铜胶体催化的环氧树脂化学镀镍

研究了利用镍/铜胶体活化的环氧树脂板的化学镀镍方法,给出了镀镍液的工艺配方:30g/LNiSO4·6H2O,10g/LCH3COONa,10g/LNaH2PO2·H2O,温度(80±2)℃,时间30min。探讨了用镍/铜胶体处理印制板时温度、时间和pH的影响,测定了化学镀镍层的剥离强度。实验结果表明,获得胶体溶液的pH为7.80,镍/铜胶体的粒径随酒石酸钠钾摩尔浓度的增加而减小,镀层的剥离强度为1.38kg/cm。     

铜渣载镍催化剂催化气化松木屑的实验研究

采用二级固定床管式反应器,以松木屑为原料,水蒸气为气化介质,载镍铜渣为催化剂,结合XRD、TEM、BET、SEM、H₂-TPR等表征手段,考察了不同的镍载量、催化剂焙烧温度以及催化温度对生物质催化气化的影响。结果表明,铜渣载镍催化剂有相对低的比表面积,但它表现出极好的抗积炭性能和裂解焦油的能力。镍载量为2.0%的催化剂经过600℃焙烧后,氢气产量为26.91mmol/g,碳转化率达到了94.86%,积炭仅为0.16%;当催化温度从850℃升高到900℃时,氢气产量只增加了0.28mmol/g,综合考虑能源消耗、催化性能以及设备损耗等因素,最佳的催化温度为850℃。由此可见,铜渣在镍催化剂上的应用可实现废物回收利用,有着重要的实用价值。     

Promoting effect of Pt addition to Ni/CeO2/Al2O3 catalyst for steam gasification of biomass

The modification of Ni/CeO₂/Al₂O₃ with Pt can make the activation by H₂ reduction unnecessary, and this indicates that the Pt/Ni/CeO₂/Al₂O₃ catalyst can be activated automatically by the compounds contained in tar. This can be explained by the enhancement of the Ni reducibility by the addition of Pt. The results of the temperature programmed reduction with H₂ also support this enhancement. Furthermore, the addition of 0.1% Pt to Ni/CeO₂/Al₂O₃ (4 wt% Ni, 30 wt% CeO₂) enhanced the performance in the steam gasification of biomass, compared to Ni/Al₂O₃ and Ni/CeO₂/Al₂O₃ in terms of low tar yield and high gas yield. This can be related to the Pt–Ni alloy formation indicated by the extended X-ray absorption fine structure analysis.     

Catalytic reforming of tar during gasification. Part I. Steam reforming of biomass tar using ilmenite as a catalyst

Ilmenite, a natural iron-containing mineral, has been investigated as an inexpensive catalyst for the steam reforming of volatiles (tar) from the pyrolysis of mallee woody biomass. The results indicate that ilmenite has good activity for the steam reforming of tar into gases due to its highly dispersed iron-containing species. The supply of external steam, in addition to the H₂O and CO₂ produced during the pyrolysis of biomass, plays an important role in minimising the formation of coke on the catalyst surface and thus the catalyst activity. The catalyst deactivation due to coke formation has more adverse effects on the reforming of larger aromatic ring system with steam than that of smaller ones. In addition, the supply of additional oxygen at low concentration changed the outcomes of tar reforming mainly because oxygen activated the smaller aromatic ring systems and polymerised them into larger aromatic ring systems in the gas phase.     

金属氧化物对生物质半焦气化特性和反应动力学影响

为测试生物质半焦中金属氧化物的催化作用,本研究利用热重分析仪比较脱灰半焦(ALC)及负载金属氧化物半焦(ALC-K2O, ALC-Na2O, ALC-CaO, ALC-Fe2O3, ALC-MgO)的气化特性,并进行动力学计算。为提高结果准确性,采用等温和非等温实验方法,并利用分布活化能模型(DAEM)和Flynn-Wall-Ozawa (FWO)等转化率法求算动力学。结果表明,金属氧化物对半焦催化效果有明显差异。等温条件下,其气化活性依次为ALC-K2O>ALC-Na2O>ALC-CaO>ALC-Fe2O3>ALC-MgO>ALC。非等温条件下,相同升温速率下,各半焦的特征汽化温度(初始温度、最大速率下温度、结束温度)由小到大依次为ALC-K2O, ALC-Na2O, ALC-CaO, ALC-Fe2O3, ALC-MgO, ALC,低特征反应温度表明其高反应活性。动力学分析发现,无论是等温还是非等温气化,活化能数据依次为ALC-K2O相似文献   

海泡石和稀土对镍催化剂性能的影响

本文研究了海泡石和稀土Sm镍催化剂的苯加氢活性及CO_２甲烷化活性的影响，并用XPS、活性比表面积及CS_２中毒等方法表征了催化剂的表面性质。结果表明，海泡石和稀土Sm能提高镍催化剂的加氢活性和抗毒性，并能增大活性镍的比表面及镍上的电子云密度，降低CO_２甲烷化反应的活化能。     

生物质催化气化实验研究

在常压流化床上进行了生物质在水蒸气条件下的实验研究。实验装置主体由常压流化床反应器和固定床催化裂解反应器组合而成。生物质原料为木屑,焦油裂解催化剂分别选用煅烧白云石和镍基重整催化剂。实验结果表明,H2/CO(H/C)的摩尔比随着气化温度、水蒸气质量/生物质质量（S/B）的升高迅速增加,但催化裂解温度变化对H/C的影响较小。另外,在催化裂解反应器中使用催化剂种类不同,H/C也不同。本文采用两段催化裂解,一段催化剂采用煅烧白云石,二段采用镍基催化剂,焦油裂解率达到96.70％。采用两段催化裂解,不但可以提高焦油的裂解率,增加了H2和CO收率,净化生物质裂解气,而且可以防止镍基重整催化剂失活,延长其使用寿命。     

Effect of carbonization temperature on the nickel crystallite size of a Ni/C catalyst for catalytic hydrothermal gasification of organic compounds

A carbon based nickel (Ni) catalyst was prepared by ion exchanging Ni ions with the ion exchangeable sites in an ion exchange resin followed by carbonization of the resin. Effect of carbonization parameters such as temperature and time on nickel crystallite size and dispersion were studied. Samples were prepared at 500, 600, 700 and 800 °C to investigate the effect of carbonization temperature. The XRD pattern and TEM images of the catalysts showed that Ni particles become bigger in size as carbonization temperature increases. No effect of carbonization time on particle size was observed. The catalytic hydrothermal gasification (CHTG) experiments with 0.2% TOC organic water at 350 °C, 20 MPa, and 50 h⁻¹ liquid hourly space velocity (LHSV) showed that the conversion or activity decreased as particle size increased, from 99% for Ni500 (3.3 nm) to 25% for Ni800 (21.5 nm). The extended time experiments showed that the conversion or activity was stable for both Ni500 and Ni700 for 50 h run time. The XRD and TEM patterns of the two catalysts after 50 h gasification run showed that Ni500 with smaller particle size shows slightly higher sintering rate than Ni700 with bigger particles.     

Zirconia: Selective oxidation catalyst for removal of tar and ammonia from biomass gasification gas

Catalysts containing zirconia and alumina were tested for their activity in the selective oxidation of tar and ammonia in biomass gasification gas. Their performance was compared with that of nickel and dolomite catalysts. Synthetic gasification gas with toluene as tar model compound was used as feed. In the presence of oxygen, zirconia and alumina-doped zirconia gave high toluene and ammonia conversions even below 600 °C. They were the most active catalysts for toluene oxidation below 700 °C and for ammonia oxidation below 650 °C. At higher temperatures than these, the impregnated ZrO₂/Al₂O₃ catalysts performed better: oxidation selectivity was improved and toluene and ammonia conversions were higher. The presence of both zirconia and alumina in the catalyst promoted toluene and ammonia conversions at low temperatures: zirconia enhanced the oxidation activity, while alumina improved the oxidation selectivity. The presence of H₂S had little effect on the activity of alumina-doped zirconia.     

Hydrothermal gasification of glucose using Raney nickel and homogeneous organometallic catalysts

Catalytic gasification of biomass to fuel gaseous in sub and super critical water is a promising method for production of sustainable energy. In this paper, a microreactor has been utilized to study the hydrothermal gasification of glucose in the presence of transition metal chelates consisting of nickel(II) acetylacetonate (Ni(acac)₂), cobalt(II) acetylacetonate (Co(acac)₂), iron(III) acetylacetonate (Fe(acac)₃) and Raney-nickel particles. The reaction temperature and pressure were 310–350 °C and 100–210 bar, respectively. Effects of addition of catalysts, reaction temperature, reaction time, glucose concentration and liquid water volume fraction on the amount of the generated gas as well as its composition were investigated. Results indicated that the presence of the organometallic compounds can slightly facilitate the rate of decomposition of glucose. This enhancement in reaction rate was more pronounced at higher concentrations of the feed (~ 0.65 M) compared with lower concentrations (~ 0.06 M). In contrast to these homogeneous catalysts, Raney-nickel catalyst improved the gas yield by a factor of 3 to 5. It has been observed that the amount of the produced gas almost doubles when the batch time increased from 3 to 30 min, while no significant change was observed from 30 to 60 min. Finally, remarks on optimization of the amount of added water into the reaction vessel are provided.