BUTENEDIOLS PRODUCTION FROM ERYTHRITOL ON Rh PROMOTED CATALYST

Abstract

The C-O hydrogenolysis of Erythritol to Butanodiols was studied in aqueous solution at 473 K and 25 bar of H2 using Rh/ReOx/TiO2 and the monometallic Rh/TiO2 and ReOx/TiO2 catalysts. The solids were characterized by temperature programmed reduction (TPR), TEM and XPS. TPR and XPS showed that ReOx species are close to Rh particles leading to reduction at lower temperature than Re on monometallic catalyst. However, some segregated Rhenium species were suspected by TPR profile for the bimetallic catalyst and detected by TEM. Re/TiO2 exhibited low activity forming only products from dehydration and epimerization. Although Rh/TiO2 showed high activity (total conversion at 14 h), was more selective to C-C cleavage leading to lower carbon products. Rh/ReOx/TiO2, showed instead, a good activity and selectivity towards C-O hydrogenolysis route yielding 37.5% of Butanodiols. Activation energy and reaction orders on ERY (0.58) and H2 (0.53) were estimated from experiences made at different reaction conditions

Effect of Support Properties on Selective Butanediols Production from Erythritol using Ir/ReOx Catalysts

“…Figure 3 shows the high-resolution image, the size histogram for Ir/ReO x / TiO 2 ; the mean particle size was 1.6 nm in accordance with the value estimated from CO chemisorption. Similar particle sizes determined by TEM were reported by other authors on Rh/ ReO x /TiO 2 [39,54,55] and Ir/ReO x /rutile; [40] it was also informed [39] that Rh/ReO x particles on ZrO 2 support were larger than on TiO 2 similarly to results in Table 3 for Ir-based catalysts. Both the particle size from CO chemisorption and the estimated from TEM were similar for all catalysts except for Ir/ReO x /SiO 2 ( d p TEM = 3.1 nm, less than half the d p CO ).…”

Ru/ReOx/TiO2 Selective and Reusable Catalyst for C−O Hydrogenolysis of C4 Polyols

“…Figure 2 B shows the Ru3d region spectrum for Ru/ReO x /TiO 2 , where a single Ru species was also observed (Ru 0 ). On the other hand, three doublets related to three different Re species were detected in the Re4 f region (Re 0 , Re +IV and Re +V ) for Ru/ReO x /TiO 2 (Figure 2 C), with Re +IV (≈73 %) as the predominant species in good agreement with previous results [32,37] …”

“…A maximum H 2 consumption was observed at 483 K and a broad peak of H 2 consumption was also detected between 873 and 973 K related to the partial reduction of surface species from Ti +IV to Ti +III [41] . The consumption of H 2 obtained for this bimetallic catalyst was 720 μmol H2 g −1 , for temperatures lower than 873 K. The difference when comparing to the theoretical value (1012 μmol H2 g −1 ) would be related to partial reduction of Re species as also observed in the Ir/ReO x /TiO 2 and Rh/ReO x /TiO 2 catalysts [32,37] . The H 2 consumption related to the first peak (483 K) corresponds to a H 2 /Ru=3.64 ratio, so it would be attributed to the reduction of RuO 2 to Ru 0 together with part of the Re 2 O 7 to ReO x .…”

“…[41] The consumption of H 2 obtained for this bimetallic catalyst was 720 μmol H2 g À 1 , for temperatures lower than 873 K. The difference when comparing to the theoretical value (1012 μmol H2 g À 1 ) would be related to partial reduction of Re species as also observed in the Ir/ReO x /TiO 2 and Rh/ReO x / TiO 2 catalysts. [32,37] The H 2 consumption related to the first peak (483 K) corresponds to a H 2 /Ru = 3.64 ratio, so it would be attributed to the reduction of RuO 2 to Ru 0 together with part of the Re 2 O 7 to ReO x . From the TPR analysis, the temperature of the first reduction peak for Ru/ReO x /TiO 2 (483 K) was selected as the optimum temperature to reduce the catalyst prior to catalytic tests in order to get ruthenium as Ru 0 keeping Re as partially oxidized.…”

“…[28][29][30] The ERY hydrogenolysis has been less studied but, in recent years it has attracted much attention. Ir/ReO x /support [31][32][33] and Rh/ReO x /support [34][35][36][37][38] catalysts have been reported to be promising for the selective formation of butanetriols (BTO) and butanediols (BDO) by CÀ O hydrogenolysis reactions. Particularly, on Ir/ReO x /SiO 2 , Ir/ReO x /TiO 2 or Ir/FeO x /TiO 2 the highest yields to BDO have been achieved.…”