Zhang Yuanjing, Yang Yusen, Hou Quandong, Xu Enze, Wang Lei, Li Feng, Wei Min
State Key Laboratory of Chemical Resource Engineering, Beijing Advanced Innovation Center for Soft Matter Science and Engineering, Beijing University of Chemical Technology, Beijing 100029, P.R. China.
ACS Appl Mater Interfaces. 2022 Jul 20;14(28):31998-32008. doi: 10.1021/acsami.2c07074. Epub 2022 Jul 6.
The one-step hydroalkylation of benzene to cyclohexylbenzene (CHB) is a technically challenging and economically interesting reaction with great industrial importance, where bifunctional catalysts play a crucial role in such a tandem reaction. In this work, we report HPWO (HPW) modified Ni nanoparticles (NPs) supported on mixed metal oxides (Ni/MMOs), which are featured by HPW species localized on the surface of Ni NPs (denoted as HPW-Ni/MMOs). The optimal catalyst (0.3HPW-Ni/MMOs) exhibits a satisfactory catalytic performance toward benzene hydroalkylation to CHB with a CHB yield of up to 41.2%, which is the highest standard among previously reported catalysts to date. A combination investigation based on HR-TEM, XPS, XANES, and FT-IR verified the electron transfer from the W atom to the adjacent Ni atom, which facilitated the formation and desorption of cyclohexene (CHE) from Ni followed by the alkylation reaction of benzene and CHE at the interfacial Brønsted (B) acid sites of HPW, accounting for the significantly enhanced catalytic behavior. It is proposed that the HPW-Ni interface structure in HPW-Ni/MMOs samples provides unique adsorption sites for benzene and CHE with a moderate adsorption strength, which serve as the intrinsic active center for this reaction: the Ni site promotes the hydrogenation of benzene to CHE, while the B acid site in HPW facilitates the alkylation of CHE and benzene to produce CHB. This work provides a fundamental understanding of the metal-acid synergistic catalysis toward the hydroalkylation reaction, which can be extended to the design and preparation of high-performance catalysts used in tandem reactions.
苯一步加氢烷基化制环己基苯（CHB）是一个技术上具有挑战性且在经济上具有吸引力、具有重大工业意义的反应，其中双功能催化剂在这种串联反应中起着关键作用。在本工作中，我们报道了负载在混合金属氧化物上的HPWO（HPW）修饰的镍纳米颗粒（NPs）（Ni/MMOs），其特征是HPW物种位于Ni NPs表面（记为HPW-Ni/MMOs）。最优催化剂（0.3HPW-Ni/MMOs）对苯加氢烷基化制CHB表现出令人满意的催化性能，CHB产率高达41.2%，这是迄今为止报道的催化剂中的最高水平。基于高分辨透射电子显微镜（HR-TEM）、X射线光电子能谱（XPS）、X射线吸收近边结构（XANES）和傅里叶变换红外光谱（FT-IR）的联合研究证实了电子从W原子转移到相邻的Ni原子，这促进了环己烯（CHE）在Ni上的生成和解吸，随后苯与CHE在HPW的界面布朗斯特（B）酸位点发生烷基化反应，这解释了催化性能的显著增强。提出HPW-Ni/MMOs样品中的HPW-Ni界面结构为苯和CHE提供了具有适度吸附强度的独特吸附位点，其作为该反应的本征活性中心：Ni位点促进苯加氢生成CHE，而HPW中的B酸位点促进CHE与苯烷基化生成CHB。这项工作为加氢烷基化反应的金属-酸协同催化提供了基本认识，可扩展到串联反应中高性能催化剂的设计和制备。
