The catalytic properties were evaluated for the reactions using [0.1% C3H4/40% H2/He balance], [0.1% C3H6/40% H2/He balance], [0.1% C3H4/10% C3H6/40% H2/He balance], and [0.1% C2H2/10% C2H4/40% H2/He balance] reactants. The measurements were conducted in standard flow reactors with gas chromatographs: (i) an Agilent 490 Micro GC equipped with a thermal conductivity detector (TCD) and a PoraPLOT Q column for the C3H4 hydrogenation and (ii) a Shimadzu GC-8A equipped with a TCD and a Shincarbon-ST column for the C2H2 hydrogenation. The catalyst (400 mg) was supported on quartz wool in a quartz tube with an internal diameter of 4 mm and surrounded by an electric furnace. After the catalyst was heated under an H2 gas flow at 600°C for 1 hour to remove the surface oxides, the reactant mixture was introduced at 30 ml min−1 (standard temperature and pressure) at ambient temperature and pressure through mass flow controllers into the catalyst channel (space velocity, about 20,000 hours−1). The catalyst was then left standing for 1 hour, and then, analysis of the gaseous species and heating were started. The unreacted reactants and products were analyzed 30 min after heating ended at every 25°C interval from 25° to 250°C.

The alkyne conversion and the alkene selectivity were estimated by usingEmbedded Image(5)Embedded Image(6)Embedded Image(7)where Cfeed, Cunreact, Calkene, and Calkane were the concentrations of the feed alkyne, the unreacted alkyne, the produced alkene, and the produced alkane, respectively. Clost in Eq. 6 is the concentration of the carbon species lost due probably to oligomerization (Clost = CfeedCunreactCalkeneCalkane). For the alkyne hydrogenation in the presence of alkene, the alkene selectivity was estimated using Eq. 7 under the assumption that all the reacted alkynes were converted into alkenes and that Clost = 0 because the very large amount of the feed alkene made it impossible to estimate small amounts of produced alkene and the lost carbon.

The apparent Ea for the C3H4 hydrogenation in the absence of C3H6 was evaluated by continuous cyclic measurement with analysis performed at every 1°C during the heating and cooling cycle at a rate of 0.5°C min−1 between 50° and 100°C. Appropriate amounts of the catalysts and the flow rates were used so that the conversion was appropriate for estimating the Ea value. The Ea value was estimated by averaging the values for both the heating and cooling processes after the change in the slope of the Arrhenius plot had sufficiently settled, as shown in fig. S4. The values and the ranges of the temperature and the conversion used for the estimation are shown in table S1. The error bar corresponds to the original values before the averaging.

The reaction orders with respect to C3H4 and H2 for the C3H4 hydrogenation in the absence of C3H6 were evaluated at 100°C from the reaction rates for four different concentrations in the feed. The reactants were [n% C3H4/40% H2/He balance (n = 0.05, 0.08, 0.13, and 0.2)] and [0.1% C3H4/m% H2/He balance (m = 20, 30, 50, and 80)]. Appropriate amounts of the catalysts and the flow rates were used so that the conversion was appropriate for estimating the reaction orders. Data were obtained 30 min after changing the concentration. Figure S5 shows the double logarithmic plots of the reaction rate versus concentration. The reaction orders were measured twice; their averages are shown in table S1.

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