Enzyme-like mechanism of selective toluene oxidation to benzaldehyde over organophosphoric acid-bonded nano-oxides

doi:10.1016/S1872-2067(20)63758-5

Abstract

Abstract:

The completely selective oxidation of toluene to benzaldehyde with dioxygen, without the need to use H₂O₂, halogens, or any radical initiators, is a reaction long desired but never previously successful. Here, we demonstrate the enzyme-like mechanism of the reaction over hexadecylphosphate acid (HDPA)-bonded nano-oxides, which appear to interact with toluene through specific recognition. The active sites of the catalyst are related to the ability of HDPA to change its bonding to the oxides between monodentate and bidentate during the reaction cycle. This greatly enhances the mobility of the crystal oxygen or the reactivity of the catalyst, specifically in toluene transformations. The catalytic cycle of the catalyst is similar to that of methane monooxygenase. In the presence of catalyst and through O₂ oxidation, the conversion of toluene to benzaldehyde is initiated at 70 °C. We envision that this novel mechanism reveals alternatives for an attractive route to design high-performance catalysts with bioinspired structures.

Key words: Selective oxidation, Toluene, Benzaldehyde, Hexadecylphosphate acid, Enzyme-like, Mechanism

Changshun Deng, Yun Cui, Junchao Chen, Teng Chen, Xuefeng Guo, Weijie Ji, Luming Peng, Weiping Ding. Enzyme-like mechanism of selective toluene oxidation to benzaldehyde over organophosphoric acid-bonded nano-oxides[J]. Chinese Journal of Catalysis, 2021, 42(9): 1509-1518.

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URL: https://www.cjcatal.com/EN/10.1016/S1872-2067(20)63758-5

https://www.cjcatal.com/EN/Y2021/V42/I9/1509

Figures/Tables 8

Fig. 1. Schematic of methane monooxygenase and HDPA-Fe2O3. (a) Structure of sMMO hydroxylase and the reaction cycle for the transformation of methane to methanol over methane monooxygenase summarized from previous investigations. (b) HDPA-Fe2O3 and the possible catalytic cycle of the reaction for the oxidation of toluene presented in this work.

Table 1 Catalytic performances of reported catalysts in the O2 oxidation of toluene to benzaldehyde.

Entry ^a	Cat.	Oxidant	Pressure (MPa)	Temp. (°C)	pH	Time (h)	Conv. (%)	Sel. (%)	STY ^c	Ref.
1	Fe₃O₄	O₂	3	180	2.5	4	< 1	—	—	[2]
2	HDPA-Fe₃O₄	O₂	3	180	2.5	4	64	> 99	1.6	[2]
3	25Fe₂O₃/Al₂O₃	O₂	2	180	2.5	4	< 8	40	—	[7]
4	HDPA-25Fe₂O₃/Al₂O₃	O₂	2	180	2.5	4	71	> 99	2.0
5	(20Fe₂O₃-5NiO)/Al₂O₃	O₂	2	180	2.5	4	< 8	30	—
6	HDPA-(20Fe₂O₃-5NiO)/Al₂O₃	O₂	2	180	2.5	4	83	> 99	2.4
7 ^b	HDPA-FeVO_x/γ-Al₂O₃	O₂	0.1	160	—	4000 ^d	~0.8	> 99	—	This work

Fig. 2. General synthetic procedure and morphology of the catalysts and the arrangement of HDPA on the catalysts. (a) Nano γ-Al2O3 used as catalytic support and its TEM image, with the {111} crystal plane as its main external surface [27]. (b) 25 wt% Fe2O3/γ-Al2O3 prepared by the impregnation and calcination method and its TEM image. (c) HDPA-Fe2O3/γ-Al2O3 prepared by bonding HDPA to 25 wt% Fe2O3/γ-Al2O3 in a density of 0.4/nm2 and its typical TEM image. The TEM observations indicate similar morphologies for the samples. (d) P 2p binding energy measured by XPS for HDPA, HDPA-Fe2O3/γ-Al2O3, and HDPA-FeVOx/γ-Al2O3. (e) FTIR result of pyridine adsorbed on Fe2O3/γ-Al2O3 (i), fresh HDPA-Fe2O3/γ-Al2O3 (ii), and HDPA-Fe2O3/γ-Al2O3 after use in toluene/O2 (iii) or toluene/Ar (iv). The inset shows the proposed Br?nsted acid site that originated from monodentate-bonded HDPA on Fe2O3/γ-Al2O3.

Fig. 3. Operando FTIR measurements with the catalysts on stream. The FTIR spectra of FeVOx/γ-Al2O3 ((a) and (d)) and HDPA-FeVOx/γ-Al2O3 ((b) and (e)) in flowing toluene and oxygen at different temperatures. (c) and (f) depict the FTIR spectra of HDPA-FeVOx/γ-Al2O3 in flowing toluene and argon at different temperatures. (Toluene: 1 μL/min, vaporized in the line; O2 or Ar: 20 mL/min; catalyst of ~0.01 g pressed into a disk; temp.: 30-130 °C).

Table 2 Changes in the IR bands with the catalysts on stream during heating (30-130 °C).

FeVO_x/γ-Al₂O₃(Toluene + O₂)		HDPA-FeVO_x/γ-Al₂O₃(Toluene + O₂)		HDPA-FeVO_x/γ-Al₂O₃(Toluene + Ar)		Assignment ^a	Ref.
Position	Intensity	Position	Intensity	Position	Intensity	Assignment ^a	Ref.
2934	n.c. ^b	2934	weak	2933	weak	ν_as(CH)	[34-36]
2879		2879	weak	2877	weak	ν_s(CH)	[34-36]
—		2833	↑ from 70 °C	2836	↑ from 100 °C	ν(CH), aldehyde	[39-42]
1948-1799		1946-1797	weak	1945-1800	weak	ring, freq. doubling
—		1742	↑ from 70 °C	1741	↑ from 120 °C	ν(C=O)	[39-42]
1605		1603	weak	1602	weak	ν_s(C=C), ring	[37]
1540		1538		1536		ν(CC), ring
1495		1494		1496		ν(CC), ring
1460		1455		1457		β_as(CH)	[34,38]
1383		1384		1381		β_s(CH)	[34,38]
—		1340	↑ from 70 °C	1337	↑ from 110 °C	δ(CH), aldehyde	[39-42]
1081		1080	Interesting (cf. Fig. 4)	1080	Interesting (cf. Fig. 4)	β(CH), ring	[37,38]
1043		1031	Interesting (cf. Fig. 4)	1031	Interesting (cf. Fig. 4)	β(CH), ring	[37,38]

Fig. 4. Specificity of the catalyst toward toluene oxidation. (a) Turnover frequency (TOF) for benzyl alcohol oxidation over HDPA-FeVOx/γ-Al2O3 and FeVOx/γ-Al2O3 based on surface area. (Benzyl alcohol: 1 μL/min, vaporized in the line; O2: 20 mL/min; cat.: 0.3 g; temp.: 130-190 °C). (b) The adsorption of toluene and benzyl alcohol by the two catalysts in a mixed ethanol solution of toluene and benzyl alcohol (cat.: 0.3 g; 30 mg toluene and 30 mg benzyl alcohol in 50 mL ethanol; temp.: 50 °C). (c) The intensity ratio of the two IR peaks related to the in-plane C-H bending vibrations of the toluene aromatic ring for toluene adsorption over the catalysts during heating between 40 and 130 °C.

Fig. 5. Redox behavior of the catalysts. (a) H2-TPR results of Fe2O3/γ-Al2O3 before and after HDPA bonding; (b) Gas-phase concentrations of benzaldehyde and O2 over HDPA-Fe2O3/γ-Al2O3 during the switch from toluene + O2 to toluene + Ar (toluene: 1 μL/min, vaporized in the line; O2 or Ar: 20 mL/min; cat.: 1 g; temp.: 160 °C).

Fig. 6. Kinetic measurements of the toluene oxidation reaction. (a) Arrhenius plots for the gas-phase toluene conversion over HDPA-Fe2O3/γ-Al2O3 and HDPA-FeVOx/γ-Al2O3 (130-170 °C); (b) Dependences of the reaction rate on the partial pressure of toluene or oxygen over HDPA-FeVOx/γ-Al2O3 (oxygen: 6-18 mL/min; toluene: 0.4-2.0 μL/min (liquid); cat.: 0.3 g; temp.: 170 °C. The total flow of the reactant was kept constant at 20 mL/min with argon used as balance); (c) Effect of the H2O pressure on the TOF of the toluene conversion over HDPA-FeVOx/γ-Al2O3 (toluene: 1 μL/min, vaporized in the line; O2: 20 mL/min; cat.: 0.3 g; temp.: 170 °C).

References

[1]	National Research Council, Board on Chemical Sciences and Technology, Panel on New Directions in Catalytic Science and Technology, Catalysis Looks to the Future. National Academy Press, Washington, DC, 1992, pp. 23-24.
[2]	L. Li, J. G. Lv, Y. Shen, X. F. Guo, L. M. Peng, Z. Xie, W. P. Ding, ACS Catal., 2014,4, 2746-2752.
[3]	J. G. Lv, Y. Shen, L. M. Peng, X. F. Guo, W. P. Ding, Chem. Commun., 2010,46, 5909-5911.
[4]	E. Gaster, S. Kozuch, D. Pappo, Angew. Chem. Int. Ed., 2017,56, 5912-5915.
[5]	Z. Liang, T. Li, M. Kim, A. Asthagiri, J. F. Weaver, Science, 2017,356, 299-303.
[6]	L. Kesavan, R. Tiruvalam, M. H. Ab Rahim, M. I. bin Saiman, D. I. Enache, R. L. Jenkins, N. Dimitratos, J. A. Lopez-Sanchez, S. H. Taylor, D. W. Knight, C. J. Kiely, G. J. Hutchings, Science, 2011,331, 195-199.
[7]	C. S. Deng, M. X. Xu, Z. Dong, L. Li, J. Y. Yang, X. F. Guo, L. M. Peng, N. H. Xue, Y. Zhu, W. P. Ding, Chin. J. Catal., 2020,41, 314-349.
[8]	M. Liu, S. Shi, L. Zhao, C. Chen, J. Gao, J. Xu, Chin. J. Catal., 2019,40, 1488-1493.
[9]	S. Ghosh, S. S. Acharyya, D. Tripathi, R. Bal, J. Mater. Chem. A, 2014,2, 15726-15733.
[10]	W. Partenheimer, Adv. Synth. Catal., 2006,348, 559-568.
[11]	M. I. bi. Saiman, G. L. Brett, R. Tiruvalam, M. M. Forde, K. Sharples, A. Thetford, R. L. Jenkins, N. Dimitratos, J. A. Lopez-Sanchez, D. M. Murphy, D. Bethell, D. J. Willock, S. H. Taylor, D. W. Knight, C. J. Kiely, G. J. Hutchings, Angew. Chem. Int. Ed., 2012,51, 5981-5985.
[12]	N. Dimitratos, J. A. Lopez-Sanchez, G. J. Hutchings, Chem. Sci., 2012,3, 20-44.
[13]	M. Sankar, N. Dimitratos, P. J. Miedziak, P. P. Wells, C. J. Kiely, G. J. Hutchings, Chem. Soc. Rev., 2012,41, 8099-8139.
[14]	T. C. Bruice, F. C. Lightstone, Acc. Chem. Res., 1999,32, 127-136.
[15]	P. Zhang, D. R. Sun, A. Cho, S. Weon, S. Lee, J. Lee, J. W. Han, D.-P. Kim, W. Choi, Nat. Commun., 2019,10, 940.
[16]	M. D. Nothling, Z. Xiao, N. S. Hill, M. T. Blyth, A. Bhaskaran, M.-A. Sani, A. Espinosa-Gomez, K. Ngov, J. White, T. Buscher, F. Separovic, M. L. O’Mara, M. L. Coote, L. A. Connal, Sci. Adv., 2020, 6, eaaz0404.
[17]	A. Warshel, P. K. Sharma, M. Kato, Y. Xiang, H. Liu, M. H. M. Olsson, Chem. Rev., 2006,106, 3210-3235.
[18]	E. Tabor, J. Dedecek, K. Mlekodaj, Z. Sobalik, P. C. Andrikopoulos, S. Sklenak, Sci. Adv., 2020, 6, eaaz9776.
[19]	J. Baek, B. Rungtaweevoranit, X. K. Pei, M. Park, S. C. Fakra, Y.-S. Liu, R. Matheu, S. A. Alshmimri, S. Alshehri, C. A. Trickett, G. A. Somorjai, O. M. Yaghi, J. Am. Chem. Soc., 2018,140, 18208-18216.
[20]	S. A. Ikbal, C. Colomban, D. W. Zhang, M. Delecluse, T. Brotin, V. Dufaud, J.-P. Dutasta, A. B. Sorokin, A. Martinez, Inorg. Chem., 2019,58, 7220-7228.
[21]	B. J. Wallar, J. D. Lipscomb, Chem. Rev., 1996,96, 2625-2657.
[22]	M. Merkx, D. A. Kopp, M. H. Sazinsky, J. L. Blazyk, J. Müller, S. J. Lippard, Angew. Chem. Int. Ed., 2001,40, 2782-2807.
[23]	K. E. Liu, A. M. Valentine, D. L. Wang, B. H. Huynh, D. E. Edmondson, A. Salifoglou, S. J. Lippard, J. Am. Chem. Soc., 1995,117, 10174-10185.
[24]	S. K. Lee, J. C. Nesheim, J. D. Lipscomb, J. Biol. Chem., 1993,268, 21569-21577.
[25]	L. Que, Y. H. Dong, Acc. Chem. Res., 1996,29, 190-196.
[26]	C. E. Tinberg, S. J. Lippard, Acc. Chem. Res., 2011,44, 280-288.
[27]	W. M. Cai, S. E. Zhang, J. G. Lv, J. C. Chen, J. Yang, Y. B. Wang, X. F. Guo, L. M. Peng, W. P. Ding, Y. Chen, Y. Lei, Z. Chen, W. M. Yang, Z. Xie, ACS Catal., 2017,7, 4083-4092.
[28]	Y. Sahoo, H. Pizem, T. Fried, D. Golodnitsky, L. Burstein, C. N. Sukenik, G. Markovich, Langmuir, 2001,17, 7907-7911.
[29]	J. Zhang, L. D. Ellis, B. W. Wang, M. J. Dzara, C. Sievers, S. Pylypenko, E. Nikolla, J. Will Medlin, Nat. Catal., 2018,1, 148-155.
[30]	C. Yee, G. Kataby, A. Ulman, T. Prozorov, H. White, A. King, M. Rafailovich, J. Sokolov, A. Gedanken, Langmuir, 1999,15, 7111-7115.
[31]	G. Busca, Phys. Chem. Chem. Phys., 1999,1, 723-736.
[32]	S. K. Davidowski, G. P. Holland, Langmuir, 2016,32, 3253-3261.
[33]	W. Gao, L. Dickinson, C. Grozinger, F. G. Morin, L. Reven, Langmuir, 1996,12, 6429-6435.
[34]	Z. B. Rui, M. N. Tang, W. K. Ji, J. J. Ding, H. B. Ji, Catal. Today, 2017,297, 159-166.
[35]	Z. R. Zhu, F. Y. Liu, W. Zhang, Mater. Res. Bull., 2015,64, 68-75.
[36]	W. M. Liao, P. P. Zhao, B. H. Cen, A. P. Jia, J. Q. Lu, M. F. Luo, Chin. J. Catal., 2020,41, 442-453.
[37]	S. Ramalingam, S. Periandy, M. Govindarajan, S. Mohan, Spectrochim. Acta A, 2010,75, 1308-1314.
[38]	Z. P. Qu, Y. B. Bu, Y. Qin, Y. Wang, Q. Fu, Chem. Eng. J., 2012,209, 163-169.
[39]	J. P. H. Li, E. M. Kennedy, A. A. Adesina, M. Stockenhuber, J. Catal., 2019,369, 157-167.
[40]	Y. N. Liao, X. Zhang, R. S. Peng, M. Q. Zhao, D. Q. Ye, Appl. Surf. Sci., 2017,405, 20-28.
[41]	J. Palomar, J. L. G. De Paz, J. Catalán, Chem. Phys., 1999,246, 167-208.
[42]	W. J. Zhu, X. Chen, J. H. Jin, X. Di, C. H. Liang, Z. M. Liu, Chin. J. Catal., 2020,41, 679-690.
[43]	H. Sun, Z. G. Liu, S. Chen, X. Quan, Chem. Eng. J., 2015,270, 58-65.
[44]	M. W. Xue, J. Z. Ge, H. L. Zhang, J. Y. Shen, Appl. Catal. A: Gen., 2007,330, 117-126.
[45]	N. K. Nag, T. Fransen, P. Mars, J. Catal., 1981,68, 77-85.
[46]	E. Genty, S. Siffert, R. Cousin, Catal. Today, 2019,333, 28-35.