Qingli Xu

Steam Reforming of Model Compounds and Fast Pyrolysis Bio-oil on Supported Nickle Metal Catalysts for Hydrogen Production

Abstract Steam reforming of biomass derived bio-oil liquid products was an available low carbon technology to produce sustainable hydrogen fuel. In this article, a series of nickel-based catalysts have been prepared. To examine the catalytic steam reforming behaviors over these catalysts in a fixed bed reactor system, several typical oxygen-containing chemicals, including acetic acids, furfural, cyclopentanone, and meta-cresol, that were proved to be contained in the bio-oil feedstock, were first selected as model starting materials. In these tests, yields for hydrogen were taken as an index of the catalyst activity and the catalyst that exhibited the maximum activity by hydrogen yields was then used for the bio-oil steam reforming studies. In this work, it was concluded that the catalyst activity reached a maximum hydrogen yield of 90.56% and decreased in an order of Ni/MgO-La2O3-Al2O3 > Ni/MgO-Al2O3 ≈ Ni/La2O3-Al2O3 > Ni/Al2O3. The yield of hydrogen for steam reforming of the whole fraction of the bio-oil reached 70% under 800°C and it only lowered 10%, after 10 hours on stream in a stability test.

Mechanism of Hydrogen Production by the Catalytic Steam Reforming of Bio-oil

Many oxygen compounds were contained in bio-oil, such as acids, alcohols, ketones, aldehydes, phenols, and sugar. Acetic acid, ethylene glycol, butanone, furfural, and m-cresol were selected as bio-oil model compounds in this article. Hydrogen production was carried out via catalytic steam reforming under the conditions of the mole ratio of steam and carbon = 6, liquid hourly space velocity = 5 h−1, and 600°C with catalyst Ni/MgO. Infrared gas analyzer was used to analyze gas concentration via catalytic steam reforming of model compounds on line, while the liquid products from a collection device were analyzed by gas chromatography/mass spectrum. Intermediates were formed under catalytic steam reforming through elimination and recombination reaction, etc. The intermediates reacted with steam to produce H2 and CO2, and then the reactions reached equilibrium in the end. The hydrogen yield of acetic acid, ethylene glycol, and butanone as materials were higher than that of furfural and m-cresol as materials at the same conditions. The lowest hydrogen yield is only 34.0% (m-cresol as feedstock) and the highest hydrogen yield is up to 78.6% (butanone as feedstock).

Preparation of Syngas via Catalytic Gasification of Biomass with a Nickel-based Catalyst

Biomass gasification to produce syngas was carried out in a fluidized bed reactor and a catalytic fixed bed reactor. The feedstock was sawdust and the cracking catalyst included the calcined dolomite, Ni/dolomite, Ni/modified dolomite, and reforming catalyst. The Ni/modified dolomite catalyst showed better performance and low cost. The optimum technological conditions were as follows: fluidized bed temperature, 1,073 K; catalytic fixed bed temperature, 1,073 K; the mass ratio of steam to biomass, 2.0.

Effect of Different Ratios of Si-Al of Zeolite HZSM-5 on the Activity of Bifunctional Catalysts Upon Dimethyl Ether Synthesis

Abstract Four bifunctional catalysts were prepared by physical mixing of a commercial methanol synthesis catalyst (JC207 catalyst, a catalyst for methanol synthesis, which has been industrialized in China) with zeolite HZSM-5 (Si-Al ratios of 25, 38, 50, 150) as a methanol dehydration catalyst. The bifunctional catalyst (JC207/HZSM-5 [Si/Al = 38]) showed better performance, which can be attributed to more acidic sites with moderate strength of zeolite, and which can control methanol dehydration rate, which is a rate determining step.

Hydrogen production by the catalytic reforming of volatile from biomass pyrolysis over a bimetallic catalyst.

Ni-Co/γ-Al2O3, Ni/γ-Al2O3, Co/γ-Al2O3, mechanical mixed Ni/γ-Al2O3, and Co/γ-Al2O3 catalyst (another name is Ni/γ-Al2O3|Co/γ-Al2O3) were prepared by the wet impregnation method, and the catalytic performance for hydrogen production by catalytic reforming of volatile from biomass pyrolysis over the four catalysts was compared under the condition of different temperatures and weight hourly space velocity. The experimental results show that the catalytic performance of the four catalysts from high to low is Ni-Co/γ-Al2O3 > Co/γ-Al2O3 > Ni/γ-Al2O3|Co/γ-Al2O3 > Ni/γ-Al2O3 within the studied temperature and weight hourly space velocity scope. Hydrogen selectivity of 94.83% and hydrogen yield of 120.81 g/kg biomass (dry basis) were obtained over Ni-Co/γ-Al2O3 under the condition of catalytic reforming temperature of 825°C and weight hourly space velocity of 0.71 h−1.

Co-processing the high-boiling fraction of bio-oil with paraffin oil.

Biomass fast pyrolysis oil (bio-oil) is considered to be a promising renewable liquid energy carrier. But it cannot be applied in stationary combustion engines, so upgrading is required. A considerable alternative upgrading method is hydrodeoxygenation; the heavy fraction of hydrodeoxygenated pyrolysis oil (HDO-oil) is called HHDO-oil. In this article, HHDO-oil co-processed with paraffin oil in a fixed-bed was studied under the conditions of different temperatures, different weight hourly space velocity, and also different co-processed ratio. It was found that co-processing of 20 wt% HHDO-oil with paraffin oil gave higher yields of liquid and better oil quality than that of the pure paraffin oil cracking. The optimum operating condition was at 520°C, the weight hourly space velocity was 4.0 h−1, and the co-processed ratio was 20%. In this operating condition, it produced the highest yield of liquid, which was 78.65 wt%, including gasoline fraction that was 8.48 wt%, diesel fraction was 37.37 wt%, lubricant fraction was 19.03 wt%, and residue fraction was 13.78 wt%.

A Model for Carbon Deposition During Hydrogen Production by the Steam Reforming of Bio-oil

H2 production by steam reforming of fast pyrolyzed bio-oil over Ni/MgO-La2O3-Al2O3 catalyst was carried out in a fixed-bed reactor by using model compounds (acetic acid, furfural, cyclopentanone, and m-cresol) and real bio-oil as the starting materials. The carbon deposition mechanism was discussed and a model of carbon deposition was built based on the amount of coke formed under different reaction temperatures, reaction times, steam to carbon molar ratios (S/C), and liquid hourly space velocities. The activation energies in the carbon deposition reaction and in the carbon elimination reaction were calculated as 28 and 71 kJ/mol, respectively, in terms of the carbon deposition model employed.

Pyrolysis Kinetics Mechanism Analysis of Sawdust by Sestak-Berggren Function

Pyrolysis kinetic characteristics of sawdust samples were studied at heating rates of 30, 40, and 50°C·min−1 by thermogravimetric analysis. The pyrolysis of sawdust could be divided into five stages, and Sestaks complex mechanism was used to study the mechanism of each stage. The thermal degradation mechanism, activation energy, and frequency factor of each stage were obtained by multi-linear regression using Microsoft Excel. The results showed that the Sestak-Berggren function is very suitable for the mechanism analysis of complex systems.

A Study on the Integrated Process for Hydrogen-rich Gas Production from Biomass

In this article, the integrated process technology is introduced for production of hydrogen, which incorporates pyrolysis of biomass and catalytic steam reforming. The process adopts a fluidized bed reactor for pyrolysis and a fixed bed reactor for steam reforming, in which technological parameters, such as pyrolysis temperature, ratio of steam over biomass, reforming temperature, gas hourly space velocity, catalyst size, and the life of the catalyst, were investigated in order to conclude their effects on the hydrogen production. Results from experiments indicate the concentration of hydrogen in the gaseous product and thus the hydrogen yield increases as both operation temperatures of pyrolysis and reforming increase while catalyst size reduces. The increase in steam over biomass, however, results in hydrogen yield varying from increase to decrease.

Effect of Modified Zeolite on One-Step Process of DME Synthesis

Abstract HZSM-5 zeolites modified by MgO, CaO, and ZnO were prepared by impregnation and bifunctional catalysts were prepared by modified HZSM-5 zeolites and JC207 catalyst (a catalyst for methanol synthesis, which has been industrialized in China). Evaluation of catalytic activity was conducted in a fixed-bed reactor. Results show, with proper basic oxide-modified zeolite, a Br⊘nsted acid site (strong acid sites) shift to Lewis acid site (weak acid sites). Weak and less strong acid sites on HZSM-5 zeolite are activity centers for the formation of dimethyl ether (DME), whereas strong acid sites for by products such as hydrocarbons. Consequently, the selectivity of CO2 and hydrocarbons decrease, especially with zeolite modified by CaO.