Laravel Passport not able to install on laravel 5.4.*

Hi I am new to laravel and trying to install the Laravel passport on an existing laravel project. I am trying to run this command

composer require Laravel/passport

When I run the command it shows nothing to install or update. But, I can see that in my composer I have Laravel version ~4.0 and I am using PHP7.1. I have also installed one of its dependency illuminator/encryption=5.4.36.

Can somebody help me out? How to install my Laravel passport?

I am running laravel 5.4.36 (it's locked)

Here's my composer:

 "require": {
        "php": ">=7.1.16",
        "davispeixoto/laravel5-salesforce": "2.*",
        "dingo/api": "1.0.x@dev",
        "doctrine/dbal": "^2.5",
        "docusign/esign-client": "^3.0",
        "elibyy/tcpdf-laravel": "5.4.2",
        "firebase/php-jwt": "5.0.*",
        "google/recaptcha": "~1.1",
        "illuminate/encryption": "5.4.36",
        "intervention/imagecache": "^2.3",
        "jiaxincui/hashid": "^1.2",
        "laracasts/flash": "^3.0",
        "laravel/framework": "5.4.*",
        "laravel/passport": "~4.0",
        "laravel/tinker": "~1.0",
        "laravelcollective/html": "^5.2.0",
        "nao-pon/flysystem-google-drive": "~1.1",
        "optimus/genie": "~2.0",
        "paragonie/random_compat": "2.*",
        "prateekkathal/laravel-simplecurl": "0.*",
        "rap2hpoutre/laravel-log-viewer": "^0.10.4",
        "reliese/laravel": "^0.0.13",
        "zizaco/entrust": "5.2.x-dev"
    },
    "require-dev": {
        "fzaninotto/faker": "~1.4",
        "mockery/mockery": "0.9.*",
        "phpunit/phpunit": "~5.7"
    },

    "scripts": {
        "post-root-package-install": [
            "php -r \"file_exists('.env') || copy('.env.example', '.env');\""
        ],
        "post-create-project-cmd": [
            "php artisan key:generate"
        ],
        "post-install-cmd": [
            "Illuminate\\Foundation\\ComposerScripts::postInstall",
            "php artisan optimize"
        ],
        "post-update-cmd": [
            "Illuminate\\Foundation\\ComposerScripts::postUpdate",
            "php artisan optimize"
        ]
    },
    "config": {
        "preferred-install": "dist",
        "sort-packages": true,
        "optimize-autoloader": true
    }

via Chebli Mohamed