Synthesis of molybdovanadophosphoric acid supported hybrid materials and their heterogeneous catalytic activity Suranjana V. Mayani, Vishal J. Mayani, Sang Wook Kim n Department of Advanced Materials Chemistry, College of Science and Technology, Dongguk University-Gyeongju, Gyeongbuk 780-714, Republic of Korea article info Article history: Received 27 May 2013 Accepted 18 August 2013 Available online 24 August 2013 Keywords: Molybdovanadophosphoric acid Hydrogen peroxide Oxidation Degradation Heterogeneous catalysis abstract We have newly developed molybdovanadophosphoric acid (MVPA) supported nano silica ball/mesopor- ous carbon/SBA-15 as heterogeneous catalysts using the advanced impregnation method. Due to their potential applications in fine chemicals and pharmaceuticals, these hybrid materials are preferred for the development of clean and environmentally acceptable heterogeneous oxidation catalysts. This work illustrates the potential use of Keggin type catalysts in selective oxidation of benzaldehyde and formaldehyde along with degradation of methylene blue using hydrogen peroxide as oxidant. The activity and selectivity of the catalysts for solvent-free heterogeneous catalytic oxidation and degradation reaction revealed with excellent conversion and recyclability. & 2013 Elsevier B.V. All rights reserved. 1. Introduction The outstanding redox behavior and unique Keggin structure of heteropoly acids (HPA) play a significant role in synthesis and applications. These catalysts have major disadvantage such as their low surface area and thermal instability. Therefore, attempts have been made to make them functional by supporting them on different carriers and impregnating solutions [1–4]. Vanadium- substituted molybdophosphoric HPA are promising catalysts for selective oxidation for the production of fine chemicals and pharmaceuticals [5,6]. Earlier, many oxidation reactions, with H 2 O 2 , have been done using molybdovanadophosphoric acid supported MCM-41 [7,8]. Benzoic acid, oxidative product of hazardous toluene, is widely used in medicines, industrial raw materials, food preservatives, cosmetics, resin design, plasti- cizers, dyestuffs and fibers preparation [9] while formic acid is useful as intermediates and preservatives [10]. Methylene blue (MB) is used for dyeing cotton, wood and silk. It is potentially harmful to the eco-environment; therefore, degradation of MB has attracted higher consideration [11–14]. Conventionally, the oxida- tion methods involve expensive reagents, high temperatures, but give lower yields [10,15]. Thus, it is necessary to find out new and efficient alternative for oxidation/degradation of hazar- dous compounds. The aim of the present work is to design thermally stable molybdovanado phosphoric acid (MVPA) supported nano silica ball (NSB)/mesoporous carbon (MC)/SBA-15 Keggin catalysts with reasonable surface area. The catalysts were used to evaluate the catalytic activity for selective oxidation of benzaldehyde and formaldehyde along with degradation of MB. 2. Experimental Synthesis of catalysts MVPA/NSB, MVPA/MC and MVPA/SBA-15: The schematic representation of synthesis process of MVPA supported NSB/MC/SBA-15 catalysts is given in Fig. 1. MVPA was prepared as described earlier with yield (28.5 g) [8]. In our previous papers, we have described the synthesis methods of NSB [16,17], MC [16,18] and SBA-15 [19–22]. Here, we have newly synthesized three catalysts by impregnating NSB, MC and SBA-15 with MVPA to give MVPA/NSB (C1), MVPA/MC (C2) and MVPA/ SBA-15 (C3), respectively. 1 g of NSB/MC/SBA-15 was taken with an aqueous solution of MVPA (0.50 g in 50 ml of distilled water) under constant stirring followed by heating at 100 1C till complete evaporation. The mixture was dried in oven at 110 1C for 24 h followed by calcinations at 500 1C for 2 h. The yields of the composites are as follows: C1 (1.361 g), C2 (1.390 g) and C3 (1.397 g). Catalytic activity towards oxidation of benzaldehyde, formaldehyde and degradation of methylene blue: Catalytic oxidation/degradation process of benzaldehyde, formaldehyde and MB are given in support- ing information. The oxidation product was analyzed through GC–MS (Shimadzu GC 2010, USA). The decomposition of MB was monitored using a UV-visible spectrophotometer (Varian-Cary 4000) and an FTIR spectrometer (Bruker, Tensor-37) (see supplementary material). Contents lists available at ScienceDirect journal homepage: www.elsevier.com/locate/matlet Materials Letters 0167-577X/$ - see front matter & 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.matlet.2013.08.078 n Corresponding author. Tel.: þ82 54 770 2216; fax: þ82 54 770 2386. E-mail address: swkim@dongguk.ac.kr (S.W. Kim). Materials Letters 111 (2013) 112–115