Effect of WO_x on Bifunctional Pd–WO_x/Al₂O₃ Catalysts for the Selective Hydrogenolysis of Glucose to 1,2-Propanediol

Abstract

A series of Pd−WO x /Al 2 O 3 catalysts with different contents of WO x were prepared by stepwise incipient wetness impregnations. The influence of WO x on the physicochemical properties of Pd−WO x /Al 2 O 3 catalysts, as well as their catalytic performance for the hydrogenolysis of glucose to 1,2-propanediol (1,2-PDO), was investigated. At low surface W density (0.3−2.1 W nm −2 ), distorted isolated WO x and oligomeric WO x are present on the Pd−WO x /Al 2 O 3 catalysts. Furthermore, isolated WO 4 are the dominating species on the Pd−WO x (5%)/Al 2 O 3 catalyst. When the W density increased to 3.1 W nm −2 , polymeric WO x species are dominant on the Pd−WO x (30%)/Al 2 O 3 catalyst. The Pd surface area decreased while the acid amount increased with increasing W density. Furthermore, increased Lewis acid sites are provided by isolated WO 4 and oligomeric WO x species whereas increased Brønsted acid sites exist on polymeric WO x species. Lewis acid sites promote glucose isomerization to fructose, which is an intermediate in glucose hydrogenolysis to 1,2-PDO. Metal sites catalyze CO hydrogenation and C−C hydrogenolysis, which avoid the coke formation on catalysts. 1,2-PDO selectivity is dependent on the synergy of Lewis acid and metal sites; however, Brønsted acid sites have no contribution to the 1,2-PDO production. Typically, the Pd−WO x (5%)/Al 2 O 3 catalyst possessing the optimal balance of Lewis acid and the metal site shows a 1,2-PDO selectivity of 60.8% at a glucose conversion of 92.2% and has a lifetime of over 200 h.

Xylitol Hydrogenolysis over Ruthenium‐Based Catalysts: Effect of Alkaline Promoters and Basic Oxide‐Modified Catalysts

“…Ru/MnO/C and Ru/SrO/C, which have significant amounts of basic sites (Table ), were also able to cleave the C−C bond to produce glycols with a high combined selectivity to the glycols (23 and 18 %, respectively) and to glycerol (8 and 7 %, respectively), whereas the selectivity to arabitol was 17 and 20 %, respectively. In contrast, Ru/WO x /C favored the isomerization reaction to arabitol, the decarbonylation to threitol and erythritol, and the cyclization of xylitol to 1,4‐anhydroxylitol by a dehydration reaction, which is known to occur on acidic WO x sites …”

Effect of tungsten surface density of WO3–ZrO2 on its catalytic performance in hydrogenolysis of cellulose to ethylene glycol

“…46 The stronger basicity and Lewis acidity have been reported to promote the isomerization of glucose to fructose. 47,48 Therefore, the EG yield declined. Fig.…”

Ethylene glycol production from glucose over W‐Ru catalysts: Maximizing yield by kinetic modeling and simulation

“…The concentration of sugar feedstock can be very high, up to 50 wt %, producing EG at high concentrations and decreasing the energy consumption for separation by distillation. Recently, we and other groups have studied the catalytic conversion of glucose to EG and 1,2‐propylene glycol under high concentrations in a semicontinuous reactor or a fixed‐bed reactor . Over 60 mol % EG yields were obtained in the conversion of 10% glucose using a homogeneous catalyst of ammonium metatungstate (AMT) and a heterogeneous catalyst of 4%Ru/activated carbon (AC) .…”

“…Recently, we and other groups have studied the catalytic conversion of glucose to EG and 1,2-propylene glycol under high concentrations in a semicontinuous reactor or a fixed-bed reactor. 15,27,34 Over 60 mol % EG yields were obtained in the conversion of 10% glucose using a homogeneous catalyst of ammonium metatungstate (AMT) and a heterogeneous catalyst of 4%Ru/activated carbon (AC). 27 The reaction temperature (T) and reactant concentration (C glu ) significantly affected the EG yield.…”