Title: Characterization of olivine-supported nickel silicate as potential catalysts for tar removal from biomass gasification
Author: Zhongkui Zhao Nandita Lakshminarayanan Scott L.
Swartz Gene B. Arkenberg Larry G. Felix Rachid B. Slimane
Chun C. Choi Umit S. Ozkan
Reference: APCATA 15042
To appear in: Applied Catalysis A: General
Received date: 6-8-2014
Revised date: 2-10-2014
Accepted date: 5-10-2014
Please cite this article as: Z. Zhao, N. Lakshminarayanan, S.L. Swartz, G.B. Arkenberg,
L.G. Felix, R.B. Slimane, C.C. Choi, U.S. Ozkan, Characterization of olivine-supported nickel silicate as potential catalysts for tar removal from biomass gasification, Applied
Catalysis A, General (2014), http://dx.doi.org/10.1016/j.apcata.2014.10.011
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Ac ce pte d M an us cri pt 1
Characterization of olivine-supported nickel silicate as potential catalysts for tar removal from biomass gasification
Zhongkui Zhao1, Nandita Lakshminarayanan1, Scott L. Swartz2, Gene B.
Arkenberg2, Larry G. Felix3, Rachid B. Slimane4, Chun C. Choi4, Umit S. Ozkan1,* 1 Department of Chemical and Biomolecular Engineering, The Ohio State University, 140 W. 19th Avenue, Columbus, OH 43210, USA 2 NexTech Materials, Ltd., 404 Enterprise Drive, Lewis Center, OH 43035, USA 3 Gas Technology Institute, 1500 First Avenue, North, Suite L134, Birmingham, AL, 35203-1821,
USA 4 Gas Technology Institute, 1700 South Mt. Prospect Rd. Des Plaines, IL, 60618-1804, USA * To whom correspondence should be addressed.
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Ac ce pte d M an us cri pt 2
In this work olivine-supported nickel silicate, which was prepared by thermal impregnation is considered as a potential tar removal catalyst for cleaning the gas stream during biomass gasification. Previous work on Ni-olivine catalysts has shown that these catalysts have good activity for the tar-reforming reaction as well as good stability and tolerance to coking. In this work, various characterization techniques such as X-ray diffraction, X-ray photoelectron spectroscopy, laser Raman spectroscopy, temperature programmed reduction, temperature programmed reaction, and subsequent temperature programmed oxidation are employed to reveal the properties of the catalyst surface and bulk as well as their relationship to catalytic activity. Higher thermal impregnation temperatures produce stronger interactions between the active component and support, leading to better coke tolerance. Relative amounts of reducible Ni, Fe species and surface Mg have an influence on catalytic behavior. Moreover, compared to olivine, the
Ni2SiO4/olivine catalyst exhibits good catalytic activity for dry reforming, water gas shift, reverse water gas shift and methanation reactions, as well as the steam reforming reaction.
Keywords: Olivine; Nickel silicate; Thermal impregnation; Steam reforming; Tar removal;
Biomass gasification 1. Introduction
With the constant rise in petroleum prices, the use of biomass as a potential and promising renewable energy resource, partially replacing fossil fuels via biomass-to-liquid
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Ac ce pte d M an us cri pt 3 or biomass-to-gas processes has been receiving increasing interest . Biomass gasification is currently a leading option for converting biomass to fuel or chemicals since many of the syngas utilization technologies have already been proven . However, one of the most crucial technical barriers is the effective removal of the tar produced. Tar is a mixture of condensable aromatic compounds [3-5]. The higher molecular weight products of biomass gasification are collectively called tar and are known to be refractory and difficult to remove by thermal, catalytic or physical processes. Tar can also cause problems downstream in the processing clogging coolers, filters and suction channels . Thus, tar removal is one of the major technological barriers to gasification technology. Several technologies are proven for the removal of tar [7-9], and catalytic tar conversion is a technically and economically interesting approach for gas cleaning [10-12].
Ni based catalysts [13-21] have been proved to be effective for eliminating tar from biomass gasification gas due to their high tar cracking activity, along with the additional advantages of steam reforming and water gas shift activity, which allows adjustment of the ratio of H2 to CO in the product gas. However, there are two main limitations for Ni based catalysts: attrition and rapid deactivation by coke formation and sintering [22-27]. Olivine is a naturally occurring mineral with the general formula (Mg,Fe)2SiO4. Olivine is mechanically hard and attrition resistant, and thus been identified as a potential support material for nickel based reforming catalysts used in fluidized bed gasification processes [28-36].
In our previous work, the thermal impregnation technique has been developed to prepare the robust and coke-resistant olivine-supported nickel catalyst for tar removal
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Ac ce pte d M an us cri pt 4 [32-34]. In the present paper, a conventional ceramic processing route was employed, by using commercially available equipment and methods for preparing large quantities of the catalyst. Methane steam reforming is used as a model reaction. Various characterization techniques, such as X-ray diffraction (XRD), X-ray Photoelectron Spectroscopy (XPS),
BET, Temperature-programmed reduction (TPR), Laser Raman Spectroscopy (LRS) have been used to study the catalyst surface and structural characteristics. Temperature programmed reaction experiments of methane steam reforming were performed to investigate the relative activity. Effect of calcination temperature and olivine geographical locations on catalyst nature and properties are also examined. Besides steam reforming,