(583by) Highly Selective and Stable Cs/SBA Catalyst for Dehydration of Glycerol to Acrolein

Highly Selective and Stable Cs/SBA Catalyst for Dehydration of Glycerol to Acrolein

Rong Liu, Tiefeng Wang*, Yong Jin

Beijing Key Laboratory of Green Reaction Engineering and Technology

Department of Chemical Engineering, Tsinghua University, Beijing 100084, China

*wangtf@tsinghua.edu.cn

Abstract

The current technology for producing acrolein is based on the selective oxidation of propylene over complex multi-component BiMoO_x-based catalysts [1, 2]. However, with the fast development of the biodiesel industry, the price of glycerol has decreased from $800/t to $300/t [2-4]. The sustainable production of acrolein from glycerol is competitive with the technology based on propylene [1, 3, 5].

The bare SBA-15 support only gave 45% glycerol conversion and 30% selectivity to acrolein. This indicated that SBA-15 itself was not effective for the dehydration of glycerol to acrolein [6]. Cs_2.5H_0.5PW₁₂O₄₀ (CsPW) has been shown to give good performance [7], with 100% initial conversion and 94% selectivity to acrolein. However, this catalyst has poor stability with the glycerol conversion decreasing to 67% after 20 h due to coke formation on its strong acid sites. As is shown in Table 1, we demonstrated for the first time the use of CsPW supported on SBA-15 as a highly efficient catalyst for the production of acrolein from glycerol. According to the CsPW loading w (wt%), the final catalyst samples were denoted as wCs/SBA (w = 30–70). The 50Cs/SBA catalyst gave the highest yield of acrolein (85%) at 300 ^oC with O₂ co-feeding, and was stable for at least 150 h. This catalyst also had good thermal stability at the coke burning temperature of 500 ^oC.

The CsPW loading had a significant influence on the glycerol conversion and selectivity to acrolein. The initial selectivity to acrolein increased from 50 to 90% with complete glycerol conversion when the CsPW loading was increased from 0 to 70%, whereas15% decreases in the glycerol conversion was observed at TOS = 20 h with 70Cs/ SBA.

Table 1 Reaction results of catalysts at TOS = 20 h

^a Reaction conditions: 300 ^oC, 0.50 g catalyst powder of 325 to 500 μm, 36 mL/min gas flow rate (N₂:O₂ = 5:1), 20 wt% glycerol aqueous solution fed at 0.6 mL/h  (WHSV_GL = 240 g_/kg_(cat)•h), 20 h time on stream

^b In brackets, glycerol conversion and acrolein selectivity at TOS = 2 h

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