A novel catalytic process for cellulose gasification to synthesis gas

The catalytic gasification of cellulose to synthesis gas has been studied under mild conditions in a laboratory scale batch-feeding and fluidized bed reactor using air as a gasifying agent and Ar as a cellulose carrier from the feeder to catalyst bed under atmospheric pressure. Various types of support materials and supported metal catalysts have been investigated in this process. The flow conditions were 60 and 50 cm³ (STP)/min of air and Ar, 2 cm height of the fluidized bed and 0.7 s residence time of volatiles. From this investigation CeO₂ has been found as the best support and Rh/CeO₂ has been found as an excellent catalyst in the cellulose gasification at 823 K, which resulted in 100% C-conversion to gas. The use of Rh/CeO₂ catalyst in the secondary bed resulted in lower yield of CO and H₂.     

Kinetics of catalytic steam gasification of bitumen coke

The catalytic steam gasification of coke from Athabasca bitumen was investigated by thermogravimetric analysis using K₂CO₃ and Na₂CO₃ as catalysts, both of which reduced the activation energy of the reaction considerably to 1.2 × 10⁵ J mol⁻¹ and 1.3 × 10⁵ J mol⁻¹, respectively, down from 2.1 × 10⁵ J mol⁻¹ for the uncatalyzed reaction. The reaction rates varied with the partial pressure of steam between 60 kPa and 85 kPa consistent with a Langmuir-Hinshelwood model, but a first order equation was also sufficient given the low partial pressures. The initial rate of gasification of the coke particles correlated linearly with the estimated external surface area of the particles, as expected from a surface reaction involving a non-porous solid. The initial reaction rate increased with increasing the catalyst loading up to 2.4 (mol potassium)/kg. A portion of the catalyst penetrated into the coke, as confirmed by secondary ion mass spectroscopy analysis, where it could not promote the reaction with steam. This result was consistent with a small increase observed in the reaction rate at low catalyst loading. The shrinking core model was successful in predicting the rates at higher conversions from the initial rate data, despite increases in BET surface area with conversion.     

天然气、二氧化碳、空气和水蒸汽转化制备合成气的研究--原料气配比对催化剂性能的影响

本文研究了天然气、二氧化碳、空气和水蒸汽制备合成气中原料气配比对催化性能的影响，结果表明：空气含量的改变并不影响合成气中H／C值；而二氧化碳和水蒸汽的含量可以调节合成气中H／C值。     

A kinetics study on catalytic and non-catalytic steam gasification of biomass

An experimental study on catalytic and non-catalytic steam-gasification of sawdust has been conducted in a microsystem by exposing a small quantity (about 1 g) of sawdust to flash pyrolysis in an atmosphere of steam in the temperature range of 350 to 650°C. The results have been evaluated on the basis of loss of weight of sawdust and a detailed gas analysis through Orsat analyser and gas chromatograph. From the rate of gas evolution, i.e. volume fraction of gas collected with time, kinetic analysis was attempted through appropriate solid—gas-reaction models. Results of this analysis has been reported in the present paper.     

Production of H2 and medium heating value gas via steam gasification of lignins in fixed‐bed reactors

In this work, steam gasification of Alcell and Kraft lignins were carried out in a fixed‐bed reactor in order to produce H₂ and medium heating value gas. The conversion of lignins increased from a low of 64 wt% for Alceil lignin to a high of 88 wt% for Kraft lignin with increasing steam flow rate and temperature. Maximum H₂ production of 60.7 mol% was obtained at 800°C and at a steam flow rate of 15 g/h/g of Kraft lignin, whereas maximum heating value of 18000 kl/m³ of the product gas was obtained at 650°C and at 5 g/h/g of Alcell lignin. Also, the performance of a Ni‐based steam reforming catalyst for the production of H₂ was studied for both types of lignin in a dual fixed‐bed reaction system. A maximum H₂ production of 63 mol% was obtained at a catalyst bed temperature of 750°C and at a catalyst loading of 0.3 g for Alcell lignin. The sulfur present in Kraft lignin had detrimental effect on the catalyst performance.     

天然气、二氧化碳和氧气制备合成气催化剂应用后的表征

对大庆化工研究中心实验用500 h后卸除的自制催化剂的组分、强度、结构和积炭量进行了分析表征。结果表明,该催化剂在500 h实验过程中组分保持较好,催化剂没有积炭,XRD显示催化剂结构基本没有发生变化。     

Low temperature gasification using lattice oxygen

Low temperature pyrolysis and gasification has been investigated based on the chemical looping combustion (CLC), where insufficient amount of lattice oxygen was reacted with hydrocarbons. Metal oxides such as nickel oxide, iron oxide and titanium oxide were used as lattice oxygen source and were coated on silica gel or porous aluminum. Single column reactor was used for experiments and 36.1 mmol of polyethylene was dropped to the column whose temperature was ranged from 693 to 1073 K. For the pyrolysis, hydrogen yield was 100% of polyethylene contained hydrogen, while methane, CO and CO₂ were minor products and almost half of the supplied carbon was deposited on the particle surface. On the other hand, for the steam gasification, 2-3 mol of the hydrogen was generated from 1 mol of carbon and almost no carbon deposition was observed. It is found that no wax and heavy tar was observed in the exhaust. Therefore, the lattice oxygen was able to be applied to the low temperature gasification of hydrocarbons.     

废轮胎热解炭低温催化焦油重整制备富氢气体的研究

以全钢型废旧轮胎为原料,通过热解、活化、浸渍、焙烧的流程制备了三种热解炭催化剂,分别为轮胎热解炭（Raw char）、轮胎热解活性炭（AC）和负载Zn的活性炭（Zn/AC）。采用N₂吸/脱附、SEM、EDS、XRD等表征方法对催化剂进行了一系列表征和分析,发现CO₂/H₂O活化可显著提高催化剂BET比表面积,最高可达380 m²·g^-1,有效改善催化剂表面结构性质,同时浸渍法使催化剂表面负载大量ZnO活性位。对三种催化剂在纤维素热解焦油重整制氢过程中的催化性能进行了研究,发现Raw char（600℃）具有最佳催化效果,相较于空白组（500℃）,热解气中H₂体积分数提高了12.4%,达到19.3%,其次为Zn/AC（500℃）组的17.8%,实现了低温下催化纤维素焦油热解制得高产率H₂。     

甲烷及水蒸气对生物质催化气化合成气和焦油的影响

以松木木屑为生物质原料,在两段式反应器上进行甲烷、水蒸气对生物质催化气化影响的实验研究,考察了甲烷与生物质之比α、水碳比S/C对气体产率、碳转化率、焦油产率、焦油组分和露点温度影响的变化规律。结果表明：α从0增加到0.4,合成气中H₂的产率增加了57.4%,甲烷的加入有利于生成富含氢气的合成气;α为0.2时碳转化率最高,为86.9%,焦油产率下降了30.5%,第二、五类焦油的产率达到最低,可见适量CH₄的添加能促进焦油的转化,特别是大分子焦油和酚类的反应。随着S/C的提高,H₂产率升高,CO产率降低;S/C从1增加到1.5,各类焦油的含量均有所降低,当S/C进一步增加到2时,第二、五类焦油含量却有所上升,说明水蒸气可以促进焦油向气体分子转化的反应,但过量的水蒸气抑制酚类和大分子焦油的分解。总之,甲烷和水蒸气的适量添加均可以提高合成气中H₂的含量,降低焦油产率,提高合成气的品质,有利于气化产物的进一步利用。     

Effect of catalyst addition on gasification reactivity of HyperCoal and coal with steam at 775-700 °C

HyperCoal is a clean coal with ash content <0.05 wt%. HyperCoal was prepared from a bituminous coal by solvent extraction method with an extraction yield of 66.7%. Effect of K₂CO₃ loading and temperature on steam gasification rate of HyperCoal and parent raw coal was investigated. Experiments were carried out at 775 and 700 °C for both HyperCoal and coal with 0-25% catalyst loading. Gasification rates increased with increased catalyst loading and reached a value above which rates did not change with catalyst loading. The catalyst loadings were 6% for HyperCoal and 20% for coal. The difference is most likely due to the difference in ash content of HyperCoal and coal and not due to the effect of H₂ inhibition on the rate. In the presence of catalyst effect of temperature was only on gasification rate and total gas yield and gas composition were unaffected.     

Integrated high temperature gas cleaning: Tar removal in biomass gasification with a catalytic filter

A nickel-based catalytic filter material for the use in integrated high temperature removal of tars and particles from biomass gasification gas was tested in a broad range of parameters allowing the identification of the operational region of such a filter. Small-scale porous alumina filter discs, loaded with approximately 2.5 wt% Al₂O₃, 1.0 wt% Ni and 0.5 wt% MgO were tested with a particle free synthetic gasification gas with 50 vol% N₂, 12 vol% CO, 10 vol% H₂, 11 vol% CO₂, 12 vol% H₂O, 5 vol% CH₄ and 0–200 ppm H₂S, and the selected model tar compounds: naphthalene and benzene. At a typical face velocity of 2.5 cm/s, in the presence of H₂S and at 900 °C, the conversion of naphthalene is almost complete and a 1000-fold reduction in tar content is obtained. Technically, it would be better to run the filter close to the exit temperature of the gasifier around 800–850 °C. At 850 °C, conversions of 99.0% could be achieved in typical conditions, but as expected, only 77% reduction in tars was achieved at 800 °C.

Conversion data can be reasonably well described with first order kinetics and a dominant adsorption inhibition of the Ni sites by H₂S. The apparent activation energies obtained are similar to those reported by other investigators: 177 kJ/mol for benzene and 92 kJ/mol for naphthalene. The estimated heat of adsorption of H₂S is 71 kJ/mol in the benzene experiments and 182 kJ/mol in the naphthalene experiments, which points at very strong adsorption of H₂S. Good operation of the present material can hence only be guaranteed at temperatures above 830 °C mainly due to the strong deactivation by H₂S at lower temperatures.     

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。     

Shell煤气化制合成气与甲烷重整二氧化碳耦合研究

为了优化化工合成过程,节约资源,减排温室气体CO2,采用Aspen Plus软件,基于Gibbs自由能最小原理,对Shell煤气化制合成气与CH4、CO2耦合过程进行模拟。分析了CH4、CO2、O2三者之间的比例对于重整合成气的影响。结果表明:当CO2/CH4体积比为1.02时,O2/CH4体积比为0.1时,得到氢碳比为0.829。通过灵敏度分析了O2量和压力对反应的影响,O2量的增加,反应温度升高,有利于耦合反应的进行;压力的增加,不利于耦合反应,但是加压可以提高生产强度,因此一般都选用加压条件下进行。     

NaOH催化水蒸气活化制煤基活性炭和氢气

在NaOH的催化作用下,通过水蒸气活化法制备了神府煤基活性炭和H2。探讨了NaOH/煤质量比、活化时间、活化温度等工艺条件对活性炭性能和H2产量的影响。结果表明,在活化温度为700℃,NaOH/煤质量比为0.5,单元活化时间为10 min的工艺条件下,可以制得碘值为635 mg/g,亚甲基蓝值为280 mg/g的活性炭,此时H2产量约17.9 mmol/g煤。     

Parameters of high temperature steam gasification of original and pulverised wood pellets

Experiments on gasification of chars obtained from original and pulverised wood pellets were conducted in atmosphere of water steam and nitrogen under temperatures of 800, 900 and 950 °C. Molar flow rates of carbon containing product gases were measured and approximated using different models with respect to extents of carbon conversion in char of the pellets. Comparison of the random pore, grain and volumetric models revealed the best applicability for approximations of the random pore model. Apparent activation energies obtained as a result of application of the models to the data from experiments with char of original pellets were higher in comparison to those of pulverised pellets, except for a grain model. Approximations under 800 °C showed relatively big deviations from experimental data on the beginning of char gasification. This is attributed to catalytic effects from alkali metals in the pellets.     

Correlation between potassium losses and mineral matter composition in catalytic coal steam gasification

The utilization of potassium as catalyst in coal steam gasification suffers due to difficulty in its quantitative recovery from gasification residues. This is due to the formation of non-leachable compounds with the mineral matter of coal. The reactivity of K₂CO₃ with some mineral constituents of coal has been evaluated at 973 K; after reaction, residues were analysed by XRD and leached with water to test the potassium solubility. Subsequently, through investigation of the interaction of potassium with 8 carbonaceous matrices from four differen ccoals, an attempt was made to establish a correlation between ash characteristics and quantity of non-recoverable potassium. It was also possible to identify some compounds formed by reaction between potassium and mineral matter.     

Experimental study on catalytic steam gasification of natural coke in a fluidized bed

The gasification characteristics of natural coke from Peicheng mine with steam were investigated in a fluidized bed reactor. The effects of catalyst type, composition and dosage of catalyst on the yield, components and heating value of product gas, and carbon conversion rate were examined. The results show that fluidized bed gasification technology is an effective way to gasify natural coke. Also the results indicate that individual addition of K-, Ca-, Fe-, Ni-based catalyst effectively increases the gasification reaction rate of the natural coke samples. With the increase in catalyst dosage, the yield and heating value of product gas per hour increase obviously, and carbon conversion rate is improved substantially. Each of aforementioned catalysts has similar catalytic effect and trend, among which the effect of Ca-based catalyst is a little weaker. The optimum metal atom ratio of mixed catalyst is Fe/Ni/others = 35/55/10, and the mixed catalyst displays maximum catalytic performance when the catalyst dosage in the natural coke is about 4%. The experimental findings provide an interesting reference for large-scale development and utilization of natural coke.