Synthesis of C 4 and C 8 Chemicals from Ethanol on MgO- Incorporated Faujasite Catalysts with Balanced Confinement Effects and Basicity Lu Zhang, [a] Tu N. Pham, [a] Jimmy Faria, [b] Daniel Santhanaraj, [a] Tawan Sooknoi, [a] Qiaohua Tan, [a] Zheng Zhao, [a] and Daniel E. Resasco* [a] Introduction Although biorefineries can produce bioethanol on a large scale, [1] the low return on investment, which is characteristic of commodities, challenges their economic profitability and ulti- mately the widespread use of bioethanol as a transportation fuel. Therefore, chemical conversion of bioethanol into more valuable commodity chemicals is a highly desirable option for its utilization. [2] The integration of energy and chemical produc- tion in biorefineries by combining existing fermentation facili- ties and chemical industrial production seems to be a crucial aspect in the development of the technology. [3] For example, the conversion of ethanol to crotonaldehyde is a reaction that has been investigated extensively. [4–8] Crotonal- dehyde is a highly reactive a,b-unsaturated aldehyde that can be used to produce the industrially valuable crotyl alcohol through chemoselective hydrogenation. [3] The two main steps in the conversion of ethanol into crotonaldehyde include dehy- drogenation to acetaldehyde and aldol condensation to the C 4 product. The latter step is conducted on either acid or basic catalysts. [9–20] One of the key requirements of these catalysts is their selectivity to C 4 products to minimize excessive conden- sation to  C 6 products. In this scenario, zeolites appear to be potentially attractive catalysts to maximize the desirable prod- uct due to their enhanced shape and size selectivity. Adjusta- ble molecular confinement when using zeolites as catalysts is a unique tool offered by zeolites to enhance selectivity. Previ- ously, we investigated the aldol condensation of acetaldehyde over faujasite zeolites with varying silicon/aluminum ratios and different types of alkali-metal cations. [21] We found that the C 4 / (C 6 + C 8 ) product ratio depended on a variety of factors, such as strength, density, and accessibility of basic sites. It was also shown that base-catalyzed condensation (C 4 and  C 6 prod- ucts) dominated at temperatures around 230 8C, whereas acid- catalyzed acetalization prevailed below 180 8C. Because high reaction temperatures may lead to side products and faster de- activation, we investigate herein the modification of faujasite zeolites to improve their activity at low temperatures. Due to its high basicity, MgO is an effective basic catalyst for aldol condensation, but, in general, it tends to generate exces- sive over-condensation products. For instance, acetaldehyde on MgO results in low C 4 /(C 6 + C 8 ) product ratios as the conver- sion increases. Therefore, herein, we have investigated novel compositions of MgO-modified faujasites, which exhibit the desirable combination of the required basic properties of MgO for the aldol reaction with the confinement benefits of the fau- jasite zeolites, which inhibit excessive condensation. This work is motivated by numerous previous investigations that have demonstrated the incorporation of metal or metal oxide clus- ters inside zeolite cavities. [22–32] Herein, we have used several A new type of catalyst has been designed to adjust the basici- ty and level of molecular confinement of KNaX faujasites by controlled incorporation of Mg through ion exchange and pre- cipitation of extraframework MgO clusters at varying loadings. The catalytic performance of these catalysts was compared in the conversion of C 2 and C 4 aldehydes to value-added prod- ucts. The product distribution depends on both the level of acetaldehyde conversion and the fraction of magnesium as ex- traframework species. These species form rather uniform and highly dispersed nanostructures that resemble nanopetals. Specifically, the sample containing Mg only in the form of ex- changeable Mg 2 + ions has much lower activity than those in which a significant fraction of Mg exists as extraframework MgO. Both the (C 6 + C 8 )/C 4 and C 8 /C 6 ratios increase with addi- tional extraframework Mg at high acetaldehyde conversion levels. These differences in product distribution can be attrib- uted to 1) higher basicity density on the samples with extrafra- mework species, and 2) enhanced confinement inside the zeo- lite cages in the presence of these species. Additionally, the formation of linear or aromatic C 8 aldehyde compounds de- pends on the position on the crotonaldehyde molecule from which abstraction of a proton occurs. In addition, catalysts with different confinement effects result in different C 8 products. [a] Dr. L. Zhang, Dr. T.N. Pham, Dr. D. Santhanaraj, Prof. T. Sooknoi, Dr. Q. Tan, Z. Zhao, Prof. D. E. Resasco School of Chemical, Biological, and Materials Engineering University of Oklahoma, Norman, OK 73019 (USA) E-mail : resasco@ou.edu [b] Dr. J. Faria Abengoa Research, C/Energía Solar no. 1 Palmas Altas, Seville 41014 (Spain) Supporting Information for this article can be found under http:// dx.doi.org/10.1002/cssc.201501518. ChemSusChem 2016, 9, 736 – 748 # 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim 736 Full Papers DOI: 10.1002/cssc.201501518