Impact of Zn/Cr Ratio on ZnCrOx-SAPO-34 Bifunctional Catalyst for Direct Conversion of Syngas to Light Olefins

Authors: Yuxuan Huang, Weixin Qian, Hongfang Ma, Haitao Zhang, Weiyong Ying

Abstract:

Light olefins are important building blocks for chemical industry. Direct conversion of syngas to light olefins has been investigated for decades. Meanwhile, the limit for light olefins selectivity described by Anderson-Schulz-Flory (ASF) distribution model is still a great challenge to conventional Fischer-Tropsch synthesis. The emerging strategy called oxide-zeolite concept (OX-ZEO) is a promising way to get rid of this limit. ZnCrO_x was prepared by co-precipitation method and (NH₄)₂CO₃ was used as precipitant. SAPO-34 was prepared by hydrothermal synthesis, and Tetraethylammonium hydroxide (TEAOH) was used as template, while silica sol, pseudo-boehmite, and phosphoric acid were Al, Si and P source, respectively. The bifunctional catalyst was prepared by mechanical mixing of ZnCrO_x and SAPO-34. Catalytic reactions were carried out under H₂/CO=2, 380 ℃, 1 MPa and 6000 mL·g_cat^-1·h^-1 in a fixed-bed reactor with a quartz lining. Catalysts were characterized by XRD, N₂ adsorption-desorption, NH₃-TPD, H₂-TPR, and CO-TPD. The addition of Al as structure promoter enhances CO conversion and selectivity to light olefins. Zn/Cr ratio, which decides the active component content and chemisorption property of the catalyst, influences CO conversion and selectivity to light olefins at the same time. C_2-4⁼ distribution of 86% among hydrocarbons at CO conversion of 14% was reached when Zn/Cr=1.5.

Keywords: Light olefins, OX-ZEO, syngas, ZnCrOx.

Digital Object Identifier (DOI): doi.org/10.5281/zenodo.1474903

References:

[1] Hirsa M. Torres Galvis and Krijn P. de Jong, “Catalysts for production of lower olefins from synthesis gas: a review” in ACS Catalysis, vol. 3, issue. 9, 2013, pp. 2130–2149.
[2] Zhiqiang Yang, Shujing Guo, Xiulian Pan, Junhu Wang and Xinhe Bao, “FeN nanoparticles confined in carbon nanotubes for CO hydrogenation” in Energy & Environmental Science, vol. 4, issue. 11, 2011, pp. 4500–4503.
[3] Zhiqiang Yang, Xiulian Pan, Junhu Wang and Xinhe Bao, “FeN particles confined inside CNT for light olefin synthesis from syngas: effects of Mn and K additives” in Catalysis Today, vol. 186, issue. 1, 2012, pp. 121–127.
[4] Hirsa M. Torres Galvis, Johannes H. Bitter, Chaitanya B. Khare, Matthijs Ruitenbeek, A. Iulian Dugulan and Krijn P. de Jong, “Supported iron nanoparticles as catalysts for sustainable production of lower olefins” in Science, vol. 335, issue. 3070, 2012, pp. 835–838.
[5] Feng Jiao, Jinjing Li, Xiulian Pan, Jianping Xiao, Haobo Li, Hao Ma, et al., “Selective conversion of syngas to light olefins” in Science, vol. 351, issue. 6277, 2016, pp. 1065–1068.
[6] Xiaoliang Liu, Wei Zhou, Yudan Yang, Kang Cheng, Jincan Kang, Lei Zhang, et al., “Design of efficient bifunctional catalysts for direct conversion of syngas into lower olefins via methanol/dimethyl ether intermediates” in Chemical Science, vol. 9, issue. 20, 2018, pp. 4708–4718.
[7] Kang Cheng, Bang Gu, Xiaoliang Liu, Jincan Kang, Qinghong Zhang and Ye Wang, “Direct and highly selective conversion of synthesis gas into lower olefins: design of a bifunctional catalyst combining methanol synthesis and carbon-carbon coupling” in Angewandte Chemie, vol. 128, issue. 15, 2016, pp. 4803–4806.
[8] Feng Jiao, Xiulian Pan, Ke Gong, Yuxiang Chen, Gen Li and Xinhe Bao, “Shape-selective zeolites promote ethylene formation from syngas via a ketene intermediate” in Angewandte Chemie International Edition, vol. 57, issue. 17, 2018, pp. 4692–4696.
[9] Yifeng Zhu, Xiulian Pan, Feng Jiao, Jian Li, Junhao Yang, Minzheng Ding, et al., “Role of manganese oxide in syngas conversion to light olefins” in ACS Catalysis, vol. 7, issue. 4, 2017, pp. 2800–2804.
[10] Xiaoliang Liu, Mengheng Wang, Cheng Zhou, Wei Zhou, Kang Cheng and Jincan Kang, et al., “Selective transformation of carbon dioxide into lower olefins with a bifunctional catalyst composed of ZnGa2O4 and SAPO-34” in Chemical Communications, vol. 54, issue. 2, 2018, pp. 140–143.
[11] Junhao Yang, Xiulian Pan, Fengjiao, Jian Li and Xinhe Bao, “Direct conversion of syngas to aromatics” in Chemical Communications, vol. 53, issue. 81, 2017, pp. 11146–11149.
[12] Peipei Zhang, Li Tan, Guohui Yang and Noritatsu Tsubaki, “One-pass selective conversion of syngas to para-xylene” in Chemical Science, vol. 8, issue. 12, 2017, pp. 7941–7946.
[13] A. Izadbakhsh, F. Farhadi, F. Khorasheh, S. Sahebdelfar, M. Asadi and Z. F. Yan, “Key parameters in hydrothermal synthesis and characterization of low silicon content SAPO-34 molecular sieve” in Microporous and Mesoporous Materials, vol. 126, issue. 1-2, 2009, pp. 1–7.
[14] Naonobu Katada, Hirofumi Igi, Jong-Ho Kim and Miki Niwa, “Determination of the acidic properties of zeolite by theoretical analysis of temperature-programmed desorption of ammonia based on adsorption equilibrium” in The Journal of Physical Chemistry B, vol. 101, issue. 31, 1997, pp. 5969–5977.
[15] Miki Niwa, Masakazu Iwamoto and Kho-ichi Segawa, “Temperature-programmed desorption of ammonia on zeolites. Influence of the experimental conditions on the acidity measurement” in Bulletin of the Chemical Society of Japan, vol. 59, issue. 12, 1986, pp. 3735–3739.
[16] Huiqing Song, Daniel Laudenschleger, John J. Carey, Holger Ruland, Michael Nolan and Martin Muhler, “Spinel-structured ZnCr2O4 with excess Zn is the active ZnO/Cr2O3 catalyst for high-temperature methanol synthesis” in ACS Catalysis, vol. 7, issue. 11, 2017, pp. 7610–7622.