I've the same problem. From the GUI isn't possible to change axis tipe. If you open the fxml you can manually change them:
<BarChart fx:id="chart" focusTraversable="false" horizontalGridLinesVisible="true" horizontalZeroLineVisible="true" legendVisible="false" mouseTransparent="false" prefHeight="385.9999000000025" prefWidth="599.9998779296875" verticalGridLinesVisible="false" verticalZeroLineVisible="true" AnchorPane.bottomAnchor="0.0" AnchorPane.leftAnchor="0.0" AnchorPane.rightAnchor="0.0" AnchorPane.topAnchor="0.0">
<yAxis>
<CategoryAxis side="LEFT" />
</yAxis>
<xAxis>
<NumberAxis side="BOTTOM" />
</xAxis>
</BarChart>
This example revert category with number axis (what i need).