20083
A comprehensive reaction - parameter variation study involving substrate concentration , catalyst ( type of metal , support , and loading ) , initial pH value , hydrogen pressure , solvent , and reaction temperature demonstrates that superior performance and high selectivity can be achieved .
 Chemical: hydrogen
Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: Chemical 
Text: {0} 
Answer:
 Chemical: hydrogen