Carboxylic acid assisted synthesis of ordered mesoporous silicon-doped γ-alumina with high thermal stability Wen Zhang a , Xiaohai Zheng a , Xiaoliang Zhao a , Ying Zheng a,n , Lilong Jiang b a College of Materials Science and Engineering, Fujian Normal University, Fuzhou, Fujian 350007, China b National Engineering Research Center of Chemical Fertilizer Catalyst, Fuzhou University, Fuzhou, Fujian 350002, China article info Article history: Received 30 April 2015 Received in revised form 6 July 2015 Accepted 18 July 2015 Available online 20 July 2015 Keywords: Sol–gel preparation Porous materials Alumina Ordered mesoporous High surface area abstract Ordered mesoporous silicon-doped γ-alumina with high thermal stability was synthesized by a modified sol–gel process with the assistance of carboxylic acid as interfacial protector in the presence of aluminum isopropoxide, tetraethylorthosilicate and Pluronic P123. The effect of molecular structure, complexation ability and volatility of carboxylic acids on the thermal stability of the obtained alumina was investigated. Structural and morphological characterization indicated that the silicon-doped γ-alumina assisted with acetic acid possesses long-range ordered 2D hexagonal mesostructure even after the calcined tem- perature up to 1000 °C and confirmed the retention of the mesoporous structure with a large surface area of 243.50 m 2 g À1 , pore volume of 0.6 cm 3 g À1 and narrow pore size distribution, demonstrating the highly thermal stability of the resulting alumina. & 2015 Elsevier B.V. All rights reserved. 1. Introduction Ordered mesoporous alumina (OMA) with uniform channels, large surface areas and tunable pore size is one of the most pop- ular catalyst supports for active species in such fields as hydro- desulfurization, hydrodechlorination, metathesis and some oxi- dation reactions [1]. However, Al 3 þ is highly susceptible to hy- drolysis, making it great difficulty to build strong Al–O–Al con- nectivity which is crucial for the formation of mesostructured alumina. Furthermore, the sintering and collapse of alumina fra- mework upon template removal by calcinations occurs easily, re- sulting in the loss of the ordered mesostructures. So far, many techniques have been developed to synthesize OMA with high thermal stability [2]. Compared with nanocasting method with silica or carbon as hard templates [3,4], the sol–gel process using block polymers as soft template is proved to be more convenient. Somorjai's group [5] was the first to report the suc- cessful synthesis of OMA and showed the corresponding TEM images with a hexagonal arrangement by using Pluronic P123. After laborious treatment, the sample possessed surface area of 410 m 2 g À1 after calcinations at 400 °C. Employing the same template, Yuan [6] made a great progress in a simple sol–gel route with HNO 3 as pH adjustor, and the as-prepared sample still pre- served surface area of 116 m 2 g À1 after 1000 °C of calcinations. Subsequently, our group extended this approach to obtain a series of thermally stable OMA by using different carboxylic acids as interfacial protectors, such as a mixture of salicylic acid and citric acid [7], o-phthalic acid [8] and p-aminobenzoic acid [9], which exhibited large surface area in range of 200–300 m 2 g À1 after calcined at 800 °C. Recently, we introduced silicon as a dopant to further stabilize the structure of OMAs in the presence of HCl [10]. Herein, we report a modify sol–gel route to synthesize meso- porous Si-doped γ-aluminas with long-range ordering mesos- tructure and the largest surface area of 243.5 m 2 g À1 at Si/Al molar ratio ca. 0.07 even after the calcined temperature up to 1000 °C, utilizing acetic acid as a interfacial protector and HCl as a acid adjustor. 2. Experimental The synthesis of samples assisted with carboxylic acids was followed the typical procedure [10]. The molar ratio of Al 3 þ :Si 4 þ : Pluronic P123:carboxylic acid in the final solution was fixed at 1:0.07:0.017:0.15 and the exact contentof the dopant Si was 6.87% determined by a PANalytical Axios XRF Petro spectrometer. The resulting samples were labeled by the corresponding carboxylic acids, that is, AA, CA or SA stands for acetic acid, citric acid or salicylic acid, respectively. For convenient comparison, Si-doped OMA without any carboxylic acid was prepared simultaneously and named as blank sample. The small- and wide-angle XRD patterns of samples ground into powder were recorded on a Philips X'Pert Pro MPD Contents lists available at ScienceDirect journal homepage: www.elsevier.com/locate/matlet Materials Letters http://dx.doi.org/10.1016/j.matlet.2015.07.097 0167-577X/& 2015 Elsevier B.V. All rights reserved. n Corresponding author. Tel.: þ89 591 82315; fax: þ86 591 83464353. E-mail address: zhn63200@163.com (Y. Zheng). Materials Letters 160 (2015) 85–87