Tuning the Acid/Metal Balance of Carbon Nanofiber‐Supported Nickel Catalysts for Hydrolytic Hydrogenation of Cellulose

Abstract

Carbon nanofibers (CNFs) are a class of graphitic support materials with considerable potential for catalytic conversion of biomass. Earlier, we demonstrated the hydrolytic hydrogenation of cellulose over reshaped nickel particles attached at the tip of CNFs. The aim of this follow-up study was to find a relationship between the acid/metal balance of the Ni/CNFs and their performance in the catalytic conversion of cellulose. After oxidation and incipient wetness impregnation with Ni, the Ni/CNFs were characterized by various analytical methods. To prepare a selective Ni/CNF catalyst, the influences of the nature of oxidation agent, Ni activation, and Ni loading were investigated. Under the applied reaction conditions, the best result, that is, 76 % yield in hexitols with 69 % sorbitol selectivity at 93 % conversion of cellulose, was obtained on a 7.5 wt % Ni/CNF catalyst prepared by chemical vapor deposition of CH(4) on a Ni/γ-Al(2)O(3) catalyst, followed by oxidation in HNO(3) (twice for 1 h at 383 K), incipient wetness impregnation, and reduction at 773 K under H(2). This preparation method leads to a properly balanced Ni/CNF catalyst in terms of Ni dispersion and hydrogenation capacity on the one hand, and the number of acidic surface-oxygen groups responsible for the acid-catalyzed hydrolysis on the other.

Catalytic transformation of cellulose into platform chemicals

“…Ni/CNF was prepared by chemical vapor deposition (CVD) of carbon on Ni/γ-Al 2 O 3 using methane. The method of catalyst preparation was modified by post-treatment for a better balance of hydrolysis and hydrogenation activities [72]. Ni/CNF was treated in concentrated HNO 3 at 383 K to oxidize CNF and to remove Ni species, and then Ni was again impregnated on the CNF.…”

Catalytic Conversion of Cellulose to Ethylene Glycol over a Low‐Cost Binary Catalyst of Raney Ni and Tungstic Acid

“…[2a] This process couples the hydrolysis of cellulose to glucose and the hydrogenation of glucose to sorbitol, which circumvents the problem of metastable glucose and allows the reaction to proceed at a relatively high temperature (above 453 K). To meet the requirements of both hydrolysis and hydrogenation, various bifunctional catalysts that bear both acid and metal sites on one catalyst have been designed and evaluated, which include Pt/Al 2 O 3 , [2a] Ni 2 P/C, [4] Ru/CNT (CNT = C nanotubes), [5] Ni/CNF (CNF = C nanofiber), [6] and Ir-Ni/MC (MC = mesoporous carbon). [7] In some cases, binary catalysts composed of a dilute mineral acid and a solid metal catalyst were also employed to make the two different functional sites more tunable.…”

Control of selectivity, activity and durability of simple supported nickel catalysts for hydrolytic hydrogenation of cellulose

“…4 The oxidation of this special catalyst by HNO 3 and subsequent impregnation of Ni (7.5) further raise the yield of hexitols up to 76%, due to the good rate balance between hydrolysis and hydrogenation. 5 In contrast, simple supported Ni metal catalysts [Ni(3)/C, Ni (16) …”