Export equations as images when compiling

Question

I want to get a .pdf file where the text is normal but the equations/mathmode are all images so I can easily convert it to .docx.

I tried many converters but none of them could handle complex equations. Images and text were perfectly converted. I tried Nitro PDF, Office 2016, Adobe Acrobat Pro latest version and GrindEQ. (Office 2016 gave me the best result from all the programs I used.)

Then I changed my google search and decided to make equations as image. I got this results (this and this and many others) but none of them worked.

If you have a solution, could you please write a complete procedure because I'm still a beginner in Latex. The following example may be useful

\documentclass[a4paper,14pt]{extreport}
\newcommand*\chem[1]{\ensuremath{\mathrm{#1}}}
\usepackage[english]{babel}
\usepackage{caption}
\usepackage{gensymb}
\usepackage{amsmath}
\usepackage{graphicx}
\usepackage{caption}
\usepackage{subfigure}
\usepackage{float}
\usepackage{makecell}
\usepackage{boldline}
\usepackage{booktabs,tabularx,array}
\usepackage[table,dvipsnames,xcdraw]{xcolor}
\usepackage{colortbl}
\graphicspath{ {images/} }
\usepackage{cite}
\usepackage{varioref}
\usepackage[hyperfootnotes=false]{hyperref}
\usepackage[capitalize]{cleveref}
\hypersetup{
    colorlinks,
    citecolor=Blue,
    linkcolor=Red,
    urlcolor=Blue}

\newcommand{\thickhline}{%
    \noalign {\ifnum 0=`}\fi \hrule height 1pt
    \futurelet \reserved@a \@xhline}
\newcolumntype{P}[1]{>{\centering\arraybackslash}p{#1}}
\newcolumntype{M}[1]{>{\centering\arraybackslash}m{#1}}
\newcolumntype{N}{@{}m{0pt}@{}}

\begin{document}
\captionsetup[figure]{labelfont={bf},labelformat={default},labelsep=period,name={Fig.}}
\renewcommand{\figureautorefname}{Fig.}
\renewcommand{\equationautorefname}{Eq.}
\renewcommand{\arraystretch}{1.2}


\chapter{General Introduction}


\subsection {Ultrasonic Nebulized Atomization}
\indent 

Ultrasonic nebulizer has been used to obtain uniformly distributed droplets of micrometer size. In this process the precursor solutions are vaporized with an ultrasonic nebulizer which is operated at a frequency of 2.56 MHz. The produced droplets of micrometer size have no inertia in their movement and can be transported without heating by the carrier gas through a pipe to the substrate. The solvent vaporizes as the droplets approach the substrate. The reactants diffuse to the substrate and a heterogeneous reaction occurs which leads to the formation of thin solid films. The pyrolysis of an aerosol, produced by the ultrasonic spraying is known as the pyrosol process. The advantage in this method is that the gas flow rate is independent of the aerosol flow rate, which is not the case with air blast spraying. The droplets from ultrasonic atomizer can be controlled using \autoref{Ultrasonic}
\begin{equation} \label{Ultrasonic}
d=0.34\left (\frac{8 \pi \gamma}{\rho f^{2}}  \right )^{\frac{1}{3}}
\end{equation}
where d is the diameter of the droplet (m),  $\gamma$ is the liquid's surface tension $(Nm^{-1})$, $\rho$ is the liquid density $(kgm^{-3})$ and f is the ultrasonic frequency (MHz)  .

\subsection{literature}
Singh and Ravindra (2010) measured the optical properties of different MPcs thin films including NiPc. The variation of refractive index (\textit{n}), extinction coefficient (\textit{k}), real ($\epsilon$\textsubscript{1}), imaginary ($\epsilon$\textsubscript{2}) parts of the complex dielectric constant ($\epsilon$) and reflectivity ($ R $) with energy (\textit{E}) were discussed and it was shown that \textit{n}, \textit{k}, $\epsilon$\textsubscript{1}, $\epsilon$\textsubscript{2} and \textit{R} vary significantly with \textit{E}. From the different MPcs (CuPc, NiPc, CoPc, FePc and MnPc) the highest energy gab (\textit{E}\textsubscript{g}) was for the CoPc and MnPc with 3.25 eV while the lowest \textit{E}\textsubscript{g} was for NiPc
\end{document}