Abstract
Optical spectra, images in the main optical emission lines and IR images directed towards the detection of molecular hydrogen, were obtained for 14 planetary nebulae (PNe). It was found that nine of these comply with the two criteria defining a type I PNe (He-rich with a large N/O ratio). All of these objects are bipolar and, with the exception of Sh 2-71, show shocked molecular hydrogen. The chemical composition of JnEr 1 indicates it was produced by a massive progenitor, and it can be tentatively classified as a type I PN. A 26 is a helium rich elliptical PN with a low N/O abundance ratio, probably without H2. Shocked H2 was found in K 3-92, an elliptical type IIb PN, which implies that this object is probably young. The chemical composition of K 3-72, K 4-55, M 1-75, and Sh 2-71 indicate that third dredge-up episodes occurred in their progenitor star. The temperatures and spectral properties of BV 5-1, K 4-55, M 1-41, M 1-75, and Sh 2-71 suggest the presence of shock waves in their ionized component.
