Honeycomb-like CuO/ZnO hybrid nanocatalysts prepared from solid waste generated in the organosilane industry

Article abstract of DOI:10.1039/c6ra11132g

We report the preparation of honeycomb-like CuO/ZnO (CZx/y) nanocatalysts with CuO nanospheres (NSs) adhered with ZnO nanoparticles (NPs) for the Rochow reaction. The synthesis was carried out via adsorption of Cu²⁺/Zn²⁺ ions on carbon black (CB) which acted as both the agglomeration inhibitor and the hard template, and followed by calcination in air. The low cost Cu²⁺/Zn²⁺ ions were recovered from the solid waste generated in the organosilane industry via a simple ammonia leaching treatment. The samples were characterized by X-ray diffraction, transmission electron microscopy, scanning electron microscopy, X-ray photoelectron spectroscopy, and temperature-programmed reduction. The as-obtained CZx/y nanohybrids had a honeycomb-like structure with large voids and openings among the CuO NSs. When re-used as a Cu-based catalyst for the Rochow reaction, the CZx/y NPs sample with an optimized ratio showed significantly improved dimethyldichlorosilane (M2) selectivity and silicon (Si) conversion as compared with the CuO/ZnO NPs prepared in the absence of CB, discrete CuO or ZnO NPs and the CuO/ZnO NPs with different compositions, mainly due to the unique honeycomb-like structure, smaller crystal size and synergistic electronic effect at the interface between Cu and ZnO in CZx/y NPs.

Full text of DOI:10.1039/c6ra11132g

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DOI: 10.1039/C6RA11132G
Honeycomb-like CuO/ZnO Hybrid Nanocatalysts Prepared from Solid
Waste Generated in Organosilane Industry
Jing Li,a,b Hezhi Liu,a Yongjun Ji,a,* Yu Zhang,a,b
Guangna Wang,a Yongxia Zhu,a Ziyi Zhong,c Xiao Huc and Fabing Sua,*
a State Key Laboratory of Multiphase Complex Systems, Institute of Process Engineering, Chinese
Academy of Sciences, Beijing 100190, People’s Republic of China
b University of Chinese Academy of Sciences, Beijing 100049, People’s Republic of China
c Nanyang Environment & Water Research Institute (NEWRI), Nanyang Technological University, 1
Cleantech Loop, CleanTech One, Singapore 637141, Singapore
*To whom correspondence should be addressed. Eꢀmail address: yjji@ipe.ac.cn (Y. Ji),
fbsu@ipe.ac.cn (F. Su), Tel.: +86ꢀ10ꢀ82544850, Fax: +86ꢀ10ꢀ82544851.
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Abstract
We report the preparation of honeycombꢀlike CuO/ZnO (CZx/y) nanocatalysts with CuO
nanosphere (NSs) adhered with ZnO nanoparticles (NPs) for the Rochow reaction. The synthesis
was carried out via adsorption of Cu2+/Zn2+ ions on carbon black (CB) which acted as both the
agglomeration inhibitor and the hard template, and followed with calcination in air. The low cost
Cu2+/Zn2+ ions were recovered from the solid wastes generated in organosilane industry via a simple
ammonia leaching treatment. The samples were characterized by Xꢀray diffraction, transmission
electron microscopy, scanning electron microscopy, Xꢀray photoelectron spectroscopy, and
temperatureꢀprogrammed reduction. The asꢀobtained CZx/y nanohybrids had a honeycombꢀlike
structure with large voids and openings among the CuO NSs. When reꢀused as a Cuꢀbased catalyst
for the Rochow reaction, the CZx/y NPs sample with the optimized ratio showed significantly
improved dimethyldichlorosilane (M2) selectivity and silicon (Si) conversion as compared with the
CuO/ZnO NPs prepared in the absence of CB, the discrete CuO or ZnO NPs and the CuO/ZnO NPs
with different compositions, mainly due to the unique honeycombꢀlike structure, smaller crystal size
and synergistic electronic effect at the interface between Cu and ZnO in CZx/y NPs.
Keywords: Heterostructure; CuO/ZnO nanocatalyst; Carbon black; Waste contact masses;
Ammonia leaching; Rochow reaction.
2

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1. Introduction
Owing to the structural features such as the pꢀn heterojunctions, CuO/ZnO materials are
promising in a wide range of applications1ꢀ4, including chemical and humidity sensing5, 6, CO2
photoreduction7, selfꢀcleaning sensor8 and selective H2S detection9ꢀ11. More recently, various
nanoscale CuO/ZnO heterostructures, such as CuO/ZnO nanoflakes12, 13, CuO/ZnO core/shell
heterostructured nanowires14, heterojunction CuO@ZnO composites15, 16, flowerꢀlike CuO/ZnO
heterostructured nanowires17, cornꢀlike CuO/ZnO structures18 and CuO/ZnO nanocorals19, have
been reported with improved catalytic performance as compared with their bulk counterparts. The
methods used to prepare these materials mainly include chemical vapor deposition20, 21, chemical
bath deposition22, 23 and hydrothermal technique24ꢀ26. However, these methods often suffer from
harsh reaction conditions, high cost, tedious synthesis process and/or complicated equipment, and
low productivity, thus hindering their eventual industrial application. To date, there is still lack of
very costꢀeffective approach to the production of hierarchically structured CuO/ZnO, particularly at
large scale.
Over the past few decades, the Rochow reaction has attracted intensive attention as it is the
most economical route to produce methylchlorosilanes (MCSs) monomers in the organosilane
industry 27ꢀ29. In this reaction, gaseous methyl chloride (MeCl) reacts with silicon (Si) with the
assistance of catalysts, and the reaction products are shown in Scheme 1. Among these products,
dimethyldichlorosilane ((CH3)2SiCl2, M2) is the most valuable one because it is a versatile building
block for some important silicon rubbers and silicon oil. Hence, the selective synthesis of M2 is
highly desired. It is reported that copperꢀbased catalysts added with zincꢀbased promoters are
effective in improving M2 selectivity and yield30. In this reaction, due to the reaction equilibrium
limitation, part of copper and zinc compounds as well as a large amount of solid Si particles will be
3