# Role of Ion-Exchange Resins in Hydrogen Reactions
## 3 Ion-Exchange Resins Application to Hydrogenation Reactions
### Hydrogenation of Alkynes  
In [PERSON] et al. (2009), self-made gel-type resins functionalized by amine were used, which were obtained by suspension polymerization of a mixture of glycidyl methacrylate, ST, and diethylene glycol dimethacrylate (DEGDMA). As metal nanoparticles, Pd (0.125-0.50 wt.%) of considerably large sizes (30-50 nm) were obtained when Pd was incorporated on dry resin beads using an aqueous solution of PdCl\({}_{2}\) as the precursor, which contrasts with the nano-scaled Pd particles obtained when Pd(OAc)\({}_{2}\) was used. However, it was the 30-50 nm Pd catalyst the one exhibiting better results for the hydrogations of 2-butyne-1,4-diol and phenylacetylene to their respective alkenes, with selectivity values ca. 92-95% at 90% conversion of the alkyne. The better performance of the large Pd nanoparticles-containing IER is related to its metal distribution (i.e., mostly, in the outer shell of the polymer beads, forming a thin layer) [75]. \begin{table}
\begin{tabular}{c c c c c c c c c c} \hline \hline \multicolumn{2}{c}{**Resin**} & \multicolumn{2}{c}{**Resin**} & \multicolumn{2}{c}{**Correlation**} & \multicolumn{2}{c}{**Selfectivity**} & \multicolumn{2}{c}{**Ref. **} \\ \hline
**Type** & **Polymer** & **Frontional** & **Group** & & & In-situ & & 30 & - & [44] \\ \hline \multirow{4}{*}{Macoreticalizer} & \multirow{4}{*}{Lovait\({}^{\prime}\)OC 1038, ST-OVB} & \multirow{4}{*}{-50 GH} & \multirow{4}{*}{Pd (3.3s\%)} & 1.8m/s/s/s/s & \multicolumn{2}{c}{1.8m/s/s/s/s/s/s/s/s/s/s/s  
\begin{table}
\begin{tabular}{c c c c c c c c c c c} \hline \multicolumn{3}{c}{**Rain**} & \multicolumn{3}{c}{**Rain**} & \multicolumn{3}{c}{**Congestion Conditions**} & \multicolumn{3}{c}{**Sensitivity**} & \multicolumn{3}{c}{**Sensitivity**} \\ \hline
**Type** & **Polymer** & **Functional Group** & **Model** & **Reduction Probical** & **Tested Reaction** & **Reaction Conditions** & **Companion** & **Sensitivity** & **Ref. ** \\ \hline \multirow{2}{*}{Gel-type} & \multirow{2}{*}{Dense\({}^{\text{th}}\times 1\times 2\text{-STOV}\)} & \multirow{2}{*}{-C\(\text{HB}\)(N\(\Delta\))} & \multirow{2}{*}{Pd(1.0 wt.5)} & \multirow{2}{*}{NaBH\({}_{k  
3-Hexyn-1-ol was hydrogenated to 3-hexen-1-ol by [PERSON] and coworkers over the already mentioned lithiated Pd/DowexTM 50W \(\times\) 2 IER (see Section 3.1) [67]. Very high values of both conversion (98.5%) and selectivity (>99.8%) were reported in their work. Four monometallic and six bimetallic catalysts, combining Cu, Ag, Ni, with Pd over the commercial acidic AmberliteTM IR-120 resin in Na+ form, were synthesized and tested for the hydrogenation of 4-nitrophenol and phenylacetylene in [PERSON] et al. (2019). Regarding the monometallic catalysts, Pd, Ag, Ni, or Cu were ion-exchanged with the resin and subsequently reduced with NaBH4. With regards to the bimetallic catalysts, two types are distinguished in their work: Pd-doped catalysts onto which a second metal was introduced by the same method (i.e., ion-exchange followed by NaBH4 reduction) and M-doped catalysts (with M being either Cu, Ag or Ni) onto which Pd was introduced as the second metal [87]. Among the monometallic catalysts, only Pd was active and selective towards ethylbenzene. Interestingly, the simultaneous presence of Ag completely inhibited the catalytic activity of Pd, while the presence of Cu enabled the selective production of styrene over ethylbenzene (i.e., >90% selectivity at high conversion values). On the other hand, Ni-containing catalysts favored ethylbenzene production. The authors attributed the superior behavior of bimetallic Cu catalysts to a geometric effect, rather than to electronic causes. [PERSON] et al. (2012) and [PERSON] et al. (2015) studied the use of hyper-crosslinked polystyrene as support for Pd nanoclusters to selectively hydrogenate C\(\equiv\)C bonds in acetylene alcohols (dimethylethylnylcarboniol, dehydrodinalool, and dehydrodionsophytol) [88; 89].